Cysteine-substituted rsv-f proteins

Abstract

The present disclosure provides inter alia, an RSV-F protein comprising at least two mutations relative to SEQ ID NO: 1 or 3 within a region of the protein corresponding to positions 474-523 of SEQ ID NO: 1 or 3; wherein the at least two mutations introduce, through substitution or insertion, a pair of C residues into the region, which form a disulphide bond.

Description

[0001] Docket No.: 70348WO01 CYSTEINE-SUBSTITUTED RSV-F PROTEINS FIELD The present disclosure is in the field of vaccinology, in particular structure-based protein design of vaccine antigens. BACKGROUND Respiratory syncytial virus (“RSV”) is a ribonucleic acid virus of the Pneumoviridae family of which two antigenically distinct subgroups / subtypes, referred to as RSV A and RSV B, exist. RSV is a leading cause of infant and older adult hospitalisation and mortality. Each year in the United States, RSV leads to approximately 58,000 hospitalisations with 100-500 deaths among children under five [1], and 177,000 hospitalisations with 14,000 deaths among adults aged 65 years and above [2]. The development of a safe and efficacious vaccine to prevent severe disease and hospitalization from RSV is therefore a high priority. The antiviral drug ribavirin is the only approved antiviral therapy for RSV treatment, but its use is restricted to severe hospitalized cases in infants and young children [3]. Furthermore, two RSV- specific humanized monoclonal antibodies, palivizumab (Synagis) and motavizumab, are confirmed to be safe and effective in reducing RSV hospitalization rates and serious complications among high- risk children in multiple clinical settings [4, 5, 6, 7, 8]. Available treatment for RSV in older adults is generally supportive in nature, consisting of supplemental oxygen, intravenous fluids and bronchodilators. In May 2023, the first RSV vaccine was approved by the FDA (AREXVY, for older adults). However, there evidently remains a need for further safe and effective prophylactic vaccines for RSV. Structure-based antigen design may hold the key to the development of such a vaccine. The RSV fusion protein (“RSV-F”) in the viral envelope is the most effective target of neutralizing antibodies, such as motavizumab. Recent advances in RSV-F structural biology have revealed changes in its antigenic characteristics that occur during the fusion process between the viral envelope and host cell membrane. RSV-F adopts a metastable “pre-fusion” conformation in the viral envelope as a homotrimer, and then an irreversible and distinct “post-fusion” conformation during fusion with the host cell membrane (see Figure 2 of [9]). The pre-fusion conformation is more immunogenic, and is bound by most RSV-F-specific neutralising antibodies in human sera. However, the native pre-fusion conformation is not energetically favourable. Therefore, pre-fusion RSV-F antigens, for use in vaccination, need to be stabilised to prevent irreversible folding to the post-fusion conformation. Thus, there remains a need for pre-fusion RSV-F protein designs which exhibit optimal properties for use as vaccine antigens, e.g. being stable in the pre-fusion conformation, amenable to high expression Docket No.: 70348WO01 yields when expressed from nucleic acids (for nucleic acid-based vaccine formats), and which elicit potent neutralising immune responses against RSV. SUMMARY The inventors have created new RSV-F proteins in the pre-fusion conformation. Firstly, exemplary RSV-F proteins according to the present disclosure exhibit particularly high stability of the pre-fusion conformation. When subjected to increasing temperature, with protein unfolding events being observed via nano-differential scanning fluorimetry (nano-DSF), exemplary RSV-F proteins exhibit higher melting temperatures than a number of control designs, including DS-Cav1 (see, e.g. Example 2, Table 4). Furthermore, the ability of exemplary RSV-F proteins to retain the pre- fusion conformation when stressed at temperatures of 50°C and 60°C over hourly timescales is greater than such control designs (see, e.g. Example 2, Figure 8). In the in vivo context, such enhanced stability is advantageous. Without wishing to be bound by theory, RSV-F proteins of the present disclosure may consistently retain the immunogenic pre-fusion conformation over time, either when expressed on the cell surface following delivery via nucleic acid, or when administered as a recombinant protein. Hence, the subject’s immune system may be exposed to pre-fusion RSV-F for longer, leading to more potent immune responses. In the context of a nucleic acid (e.g. RNA)-based vaccine, high expression levels from nucleic acids may further potentiate the immunogenicity of a stable pre-fusion RSV-F design. Indeed, exemplary RSV-F proteins according to the present disclosure exhibit such high expression levels from nucleic acids in vitro (see, e.g. Example 4; Figures 16-18) – an effect which is enhanced through selective truncation of the C-terminal cytoplasmic tail of the RSV-F protein. These in vitro observations are corroborated by in vivo evidence (see e.g. Example 6, Figures 23 and 24), where exemplary RSV-F proteins (delivered via nucleic acid) elicited higher neutralising antibody titres against RSV of the A and B subtypes, in comparison to a number of control constructs. Neutralising antibody titres generally correlate with inhibition of viral replication in the lungs and other respiratory sites, and thus protective efficacy in a subject. Hence, without wishing to be bound by theory, RSV-F proteins of the present disclosure may allow for protective efficacy against RSV to be achieved at lower doses of a nucleic acid-based vaccine, leading to further possible benefits, such as reduced reactogenicity. See also e.g. Examples 11, 14 and 15 (Figures 31-34, 48-49 and 41-47 respectively), for further evidence of in vivo efficacy, in particular incorporating codon optimisation of nucleic acids. Furthermore, one or two administrations of codon-optimised nucleic acid elicited neutralising antibody titers against RSV strains of the A and B subtypes which were maintained for at least six months post-administration (see, e.g. Example 15, Figures 39 and 40). The effects and advantages above were achieved through a combination of originally in silico- predicted substitutions (to wild-type RSV-F) which promote and / or stabilise the pre-fusion conformation, and the introduction of a disulphide bond into the heptad repeat B (HRB) domain of the Docket No.: 70348WO01 RSV-F protein. Cysteine residue pairs were introduced into inter alia, said region, in the expectation of forming inter-protomer disulphide bonds (that is, between protomers in an RSV-F protein trimer). See, e.g. Example 1; Figures 1-3 and 13. However, surprisingly, certain cysteine pairs form intra- protomer disulphide bonds (that is within protomers in an RSV-F protein trimer). See, e.g. Example 3; Figures 14 and 15, where the intra-protomer disulphide bond was confirmed through cryo-electron microscopy (cryo-EM). Moreover, such disulphide bonds in specific positions result in a stabilisation mechanism whereby (i) negatively charged residues in the HRB domain are substituted for cysteines and (ii) further negatively charged residues are positioned further apart, relative to wild-type, as a result of the disulphide bond (see e.g. Figure 15 C-F). This mechanism reduces repulsive electrostatic interactions between negatively charged residues in the HRB domain, which in wild-type help to drive the conformational change from pre- to post-fusion conformation. Hence, such disulphide bonds contribute to the stability of RSV-F proteins of the present disclosure. Analysis by cryo-EM also revealed further, surprising, structural effects of such disulphide bonds (see, e.g. Example 12). In some embodiments, such disulphide bonds may reposition the side chain of wild- type aromatic residue F488 to introduce a pi-pi stacking interaction with wild-type residue aromatic F137 in the fusion peptide (see, e.g. Figures 36A and D). In such embodiments, the additional interaction (over wild-type) may result in a cation-pi-pi trio-stacking interaction between residues K339, F137 and F488, which may further restrict movement of the fusion peptide, thereby helping to stabilise the pre-fusion conformation (see, e.g. Figures 36C and D). Furthermore, exemplary RSV-F proteins according to the present disclosure also elicit neutralising antibody titers when administered as an adjuvanted recombinant protein, see e.g. Example 14 (Figure 49). Given all of the above, RSV-F proteins generated by the inventors may be useful as vaccine antigens, namely to be used in prophylactic vaccination against RSV. Accordingly, in a first independent aspect, the present disclosure provides: An RSV-F protein, comprising at least two mutations relative to SEQ ID NO: 1 or 3 within a region of the protein corresponding to positions 474-523 of SEQ ID NO: 1 or 3; wherein the at least two mutations introduce, through substitution or insertion, a pair of C residues into the region, which form a disulphide bond. In a further independent aspect, the present disclosure provides a nucleic acid (preferably RNA) encoding an RSV-F protein of the present disclosure. In a further independent aspect, the present disclosure provides a host cell comprising a nucleic acid of the present disclosure. Docket No.: 70348WO01 In a further independent aspect, the present disclosure provides an in vitro method for the production of an RSV-F protein of the present disclosure, comprising expressing a nucleic acid of the present disclosure (preferably, an expression vector) in a host cell, and optionally purifying the RSV-F protein. In a further independent aspect, the present disclosure provides a carrier (preferably, a lipid nanoparticle) comprising a nucleic acid of the present disclosure. In a further independent aspect, the present disclosure provides a pharmaceutical composition comprising an RSV-F protein, nucleic acid (preferably RNA) or carrier (preferably lipid nanoparticle) of the present disclosure. In a further independent aspect, the present disclosure provides an RSV-F protein, nucleic acid (preferably RNA), carrier (preferably lipid nanoparticle) or pharmaceutical composition of the present disclosure, for use in medicine. In a further independent aspect, the present disclosure provides a therapeutic method comprising the step of administering an effective amount of the RSV-F protein, nucleic acid (preferably RNA), carrier (preferably lipid nanoparticle), or pharmaceutical composition of the present disclosure to a subject (preferably a subject in need of such administration). Further independent aspects of the present disclosure are provided throughout the detailed description, below. DESCRIPTION OF FIGURES Figure 1. Expression of Round 5 designs and DS-Cav1. Biolayer Interferometry (BLI) of the histidine- tagged sequences indicates design F528 is expressed particularly well in mammalian cells, when compared to spent media (confirmed by subsequent experiments). Error bars represent standard error. Figure 2. OCTET BLI of Round 5 sequences bound to RSV-F antibodies (AM14, D25, RSB1). Responses normalized to DS-Cav1. Figure 3. Binding of (A) DS-Cav1, (B) F504, and (C) F528 incubated at 50 or 60°C for 30, 60, or 120 min to RSV-F antibodies (AM14 and D25) was determined using OCTET BLI. Results are reported as response relative to control (Time 0) sample. Figure 4. OCTET BLI of Round 6 designs in RSV-F A2 subtype (“F300”) background quantified for expression with a histidine-tag. Negative control subtracted from all samples. Error bars are standard error. Figure 5. OCTET BLI of Round 6 designs in RSV-F A2 subtype (“F300”) background bound to RSV- F antibodies (AM14, D25, RSB1, motavizumab). Responses normalized to DS-Cav1. Figure 6. OCTET BLI of Round 6 designs in F420 and F528 backgrounds quantified for expression with a histidine-tag. *Indicates concentrations were too high to determine (>300 µg / mL before Docket No.: 70348WO01 subtraction of negative control). Negative control subtracted from all samples. Error bars are standard error. Figure 7. OCTET BLI of Round 6 designs in F420 and F528 backgrounds bound to RSV-F antibodies (AM14, D25, RSB1, motavizumab). Responses normalized to DS-Cav1. Figure 8. Binding of (A) DS-Cav1, (B) F(i), (C) F(ii), (D) F420, (E) F647, (F) F651, (G) F528, (H) F663, and (I) F664 incubated at 50 or 60°C for 30, 60, or 120 min to RSV-F antibodies (AM14 and D25) was determined using OCTET BLI. Results are reported as response relative to control (Time 0) sample. Figure 9. Round 6 design final protein yield from 100 mL of EXPI293 cell harvest media. Quantification of final protein yield from 100 mL culture for 4 Round 6B designs, as compared to controls (F528 and F420), DS-Cav1, F(i), and F(ii). Figure 10. Round 6 design affinity for RSV-F antibodies (AM14, D25, RSB1, motavizumab) as determined on BIACORE. Binding affinity (KD) of pre-fusion RSV-F-specific antibodies for Round 6B RSV-F designs tested using BIACORE against antibodies AM14 (quaternary epitope), D25 (site Ø), RSB1 (site V), and motavizumab (site II). Figure 11. Round 6 (part 1) designs summary Figure 12. Round 6 (part 2) designs summary: (A) F528-based designs; (B) F420-based designs Figure 13. E486C and A490C were predicted to form an inter-protomer disulphide bond in design F528. E486 and A490 are labeled and individual protomers are shaded differently for clarity. Image was generated using CHIMERAX molecular visualization program. Figure 14. Structural characteristics of RSV F528 determined by cryo-EM. (A) Cryo-EM structure of the RSV F528-AM14 Fab complex. For simplicity, one protomer is shown in ribbon while the other protomers of the F528 trimer are shown in surface presentation. Mutations introduced in F528 design relative to wild-type are indicated by black spheres and labelled accordingly. Two of the bound AM14 Fabs are shown in white and light grey ribbon. (B) The formation of intra-protomer disulphide bonds. The D486C-A490C mutations are shown in sticks and the disulphide bonds are emphasised with diagonal lines. (C) The density of disulphide bond captured in cryo-EM map. The EM density map is shown in mesh while the D486C-A490C mutations are shown in sticks and the disulphide bonds are emphasised with diagonal lines. Figure 15. Structural characteristics of RSV F647 determined by cryo-EM. (A) Cryo-EM structure of the RSV F647-RSB1 Fab complex. For simplicity, one protomer is shown in ribbon while the other two protomers of the F647 trimer are shown in surface presentation. Mutations introduced in F647 design relative to wild-type are indicated by black spheres and labelled accordingly. Two of the bound RSB1 Fabs are shown in white and light grey ribbon. (B) A zoom view of intra-protomer disulphide Docket No.: 70348WO01 bonds captured by cryo-EM. The EM density map is shown in mesh. The D486C-A490C disulphide bond is emphasised with diagonal lines. (C) The stabilized electrostatic repulsive ring in design F647. (D) The electrostatic repulsive ring in wild-type RSV F protein. In both (C) and (D), the disulphide bond and nearby negatively charged residues are shown in sticks and the distances of the negatively charged residues at the trimer centre are labelled. (E) The electrostatic distribution of the stabilized electrostatic repulsive ring in design F647. (F) The electrostatic distribution repulsive ring in wild-type RSV F protein. In both (E) and (F), the residues are rendered in surface presentative and coloured from dark to light based on their charges: dark, negatively charged; white, not charged. Residues that are highly negatively charged are indicated. Figure 16. 26 RSV F-encoding mRNAs were screened in primary human BJ cells for their ability to express the RSV F antigen on the cell surface. RSV F trimeric surface expression was detected by indirect immunofluorescent labelling (using AM14 antibody) followed by quantification using high content imaging and analysis. At (A) 25 hours, and (B) 72 hours post-transfection (hpt) cell monolayers were fixed, then RSV-F was labelled and imaged using a 10x objective. Each bar depicts the average intensity of the Alexa647 signal for cells identified by automated image analysis from 9 imaged fields per well, and as shown, represents the mean (µ) + / - 1 standard deviation (σ) from 3 biological replicates, as calculated by GRAPHPAD PRISM software. Figure 17. 26 RSV F-encoding mRNAs were screened in primary human BJ cells for their ability to express the RSV F antigen on the cell surface. RSV F pre-fusion surface expression was detected by indirect immunofluorescent labelling (using D25 antibody) followed by quantification using high content imaging and analysis. At (A) 25 hours, and (B) 72 hours post-transfection (hpt) cell monolayers are fixed, then RSV-F was labelled and imaged using a 10x objective. Each bar depicts the average intensity of the Alexa647 signal, as per Figure 16. Figure 18. 26 RSV F-encoding mRNAs were screened in primary human BJ cells for their ability to express the RSV F antigen on the cell surface. Total RSV F surface (pre- or post-fusion conformation) expression was detected by indirect immunofluorescent labelling (using motavizumab antibody) followed by quantification using high content imaging and analysis. At (A) 25 hours, and (B) 72 hours post-transfection (hpt) cell monolayers are fixed, then RSV-F was labelled and imaged using a 10x objective. Each bar depicts the average intensity of the Alexa647 signal, as per Figures 16 and 17. Figure 19. Zoomed in view of substitution 228K from cryo-EM structure of a parental design to inter alia, F217, F528 and F647, called F21 (structure as depicted here also applicable to aforementioned designs). K228 and surrounding residues are depicted as sticks. Hydrogen bond between K228 and Y250 is depicted as a dashed line. Figure 20. Zoomed in view of substitution 55T from cryo-EM structure of a parental design to inter alia, F217, F528 and F647, called F21 (structure as depicted here also applicable to aforementioned Docket No.: 70348WO01 designs). T55 is shown as sticks with a transparent surface. Residues forming the hydrophobic pocket and involved in van der Waals contacts with T55 are shown as sticks (including hydrophobic pocket). Figure 21. Zoomed in view of substitution 215A from cryo-EM structure of a parental design to inter alia, F217, F528 and F647, called F21 (structure as depicted here also applicable to aforementioned designs), including proximal α helices. A215 is depicted as stick with transparent surface. Residues forming a hydrophobic region that may be involved in van der Waals contacts with A215 are shown as sticks. Figure 22. First derivative (330 / 350 nm fluorescence intensity ratio) nanoDSF unfolding curves of freshly thawed designs F528, F647, F651, F420, F663, F664 and controls (DS-Cav1, F(ii), F(i) and F21). Figure 23. (A) RSV A neutralising antibody titres (ED60) on day 21 (3wp1) and day 35 (2wp2) in animals immunized with 0.5 μg of RNA encoding F528, F647, F647 ΔCT20, F651 ΔCT20, F(iii), F(i), F(ii), or DS-Cav1 (where each point represents an individual animal). (B) RSV A and B day 35 (2wp2) cross-neutralisation titres to lab-adapted (RSV A-long and RSV B-18537) and clinical RSV strains (RSV A-Clinical 2015, RSV B-Clinical 2015 and 2017). Figure 24. pre-F IgG binding antibody titers on day 21 and day 35 for constructs in Example 6. Figure 25. Protein yields of minimal substitution designs, relative to DS-Cav1. Negative control (EXPIFECTAMINE and cell culture supernatant), F225 (positive control; SEQ ID NO: 15) and F300 (wild-type) also shown. Figure 26. Octet BLI of the minimal substitution designs bound to RSV-F antibodies (AM14, D25, RSB1, motavizumab), relative to DS-Cav1. Negative control (EXPIFECTAMINE and cell culture supernatant), F225 and F300 (wild-type) also shown. Figure 27. 7 RSV F-encoding mRNAs with different numbers of substitutions (see Table 6) were screened in primary human BJ cells for their ability to express AM14-positive RSV-F antigen (see Table 6 for encoded proteins). Each bar depicts the average intensity of the Alexa647 signal for cells identified by automated image analysis from 9 imaged fields per well, and as shown, represents the mean (µ) + / - 1 standard deviation (σ) from 3 technical replicates, as calculated by GraphPad Prism software. Figure 28 The optimal length of the RSV F CT that supports cell-surface expression of the trimeric, pre-fusion RSV F protein includes CTs of at least 5, but not longer than 10, amino acids. The cell- surface expression of trimeric, pre-fusion RSV F protein was evaluated by indirect immunofluorescent labelling using monoclonal antibody AM14 followed by quantification using high content imaging and analysis across a 4-day time course. Primary, human fibroblast (BJ) cells were forward transfected in 96-well format with mRNAs encoding RSV F variant F(ii). In (A), select CT variations are shown. The parent (F(ii), solid line, solid box) was modified by deletion of the RNA sequence encoding the Docket No.: 70348WO01 terminal 15 amino acids (F(ii) CTDΔ15, solid line, solid circle), 16 amino acids ((F(ii) CTDΔ16, dotted line, solid circle), 17 amino acids (F(ii) CTDΔ17, dotted line, open circle), 20 amino acids (F(ii) CTDΔ20, solid line, open circle), 21 amino acids (F(ii) CTDΔ21, dotted line, solid box), or complete deletion of the CT domain (F(ii) CTDΔ25, solid line, open box). In (B), the area under the curve is shown, as calculated from the line graphs in (A) and extended to include additional CT deletions, and (C), the same data as B depicted as line graph. At specific time points (hours post transfection) cell monolayers were fixed, then RSV F was labelled and imaged using a 10x objective. For line graphs, each plotted value expresses the average intensity of the Alexa647 signal for cells identified by automated image analysis from 9 imaged fields per well. Each point on the line graph represents the mean (µ) + / - 1 standard deviation (σ) from 3 biological replicates. The area under the curve (AUC) is shown in (B) with 1 standard error of the mean (SEM). The means, AUC and variability shown on the line and bar graphs were calculated by GraphPad Prism software. Figure 29. As for Figure 28 but with D25 antibody binding being assessed. Figure 30. HPLC chromatograms assessing monodispersity of F310 or F310_v2 (2x Strep tag removed relative to F310) following purification, incubation at 4°C overnight, or one freeze / thaw cycle. Figure 31. pre-F IgG binding antibody titres on (A) day 21 (3wp1) and (B) day 35 (2wp2) in animals immunised with varying doses of RNA encoding F647 ΔCT20, F647 ΔCT20 (codon optimised), F(iii), F(i) and F(i) ΔCT20. Figure 32. RSV A neutralising antibody titres on (A) day 21 (3wp1) and (B) day 35 (2wp2) in animals immunised with varying doses of RNA encoding F647 ΔCT20, F647 ΔCT20 (codon optimized), F(iii), F(i) and F(i) ΔCT20. Figure 33. Percentage of RSV A specific (A) CD4+ and (B) CD8+ T cells from mice immunised with F647 ΔCT20 and F647 ΔCT20 (codon optimised) (1.5 μg and 0.5 μg doses). Figure 34. Percentage of (A) CXCR5+PD1+ Tfh cells and (B) Pre-F specific CD95+GL7+ germinal center B cells from mice immunised with F647 ΔCT20 and F647 ΔCT20 (codon optimised) (1.5 μg and 0.5 μg doses). Figure 35. Ribbon diagram illustrating that the 486:490 disulphide (in inter alia design F647) restricts the transformation of residues 485-492 into a helix in their post-fusion conformation. Figure 36. The 486:490 disulphide repositions the side chain of F488 to introduce a pi-pi stacking interaction with residue F137 in the fusion peptide. (A) Ribbon diagram overview of the fusion peptide and HRB regions in design F647 (the repositioning of F488 relative to wild-type is indicated by three black arrows). (B) Ribbon diagram overview of the fusion peptide and HRB regions in wild-type RSV- F, with the wild-type position of F488 circled by a dashed line. (C) Cryo-EM density of the fusion peptide in F647, showing that all residues are well-resolved. (D) Cryo-EM density of residues K339, Docket No.: 70348WO01 F137, F488 and the 486:490 disulphide in F647. In (C) and (D), cryo-EM density is shown in mesh. In all of (A)-(D), fusion peptide residues (e.g. F137) are indicated with diagonal lines. Figure 37. Structural comparison between F647, F651 and 2ndgeneration DS-Cav1 (positioning of α10 helices at the trimer base). Distances between the three α10 helices in the trimer were measured from the Cα of residue 501 of (A) F647, (B) F651 and (C) 2ndgeneration DS-Cav1. (D) Sequence alignment of N-terminal portions of F647, F651and 2nd generation DS-Cav1 (“FP” = fusion peptide). Figure 38. (A) Expression of “Round 6” RSV-F designs and comparators in A2 and M16 strain background (wild-type) sequences, relative to DS-Cav1 A2, measured using biolayer interferometry (BLI) of histidine-tagged sequences. Error bars represent standard error. (B) OCTET BLI of RSV-F designs in A2 and M16 background sequences bound to RSV-F antibodies (AM14, D25, Motavizumab, and RSB1). Response normalised to DS-Cav1 A2. (C) Binding affinity (KD) of pre- fusion- RSV-F-specific antibodies AM14, D25, RSB1 and motavizumab for RSV-F designs, determined using BIACORE. Figure 39. RSV A neutralizing antibody titer elicited by RNA encoding F647 ΔCT20 (codon optimised), measured from serum collected on day 21 and day 35 plus monthly for six months. Each mouse is presented as a dot. The horizontal dotted line represents the Limit of Detection (LOD). Data with observed geometric mean titer (GMT) and 95% confidence interval (CI) by dose. Observed GMT values are noted at the bottom. (A) saline group; (B) 0.497 μg dose group (two administrations, on days 0 and 21); (C) 0.497 μg dose group (one administration, on day 0). Figure 40. RSV B neutralizing antibody titer elicited by RNA encoding F647 ΔCT20 (codon optimised), measured from serum collected on day 21 and day 35 plus monthly for six months. Each mouse is presented as a dot. The horizontal dotted line represents the Limit of Detection (LOD). Data with observed geometric mean titer (GMT) and 95% confidence interval (CI) by dose. Observed GMT values are noted at the bottom. (A) saline group; (B) 0.497 μg dose group (two administrations, on days 0 and 21); (C) 0.497 μg dose group (one administration, on day 0). Figure 41. RSV A F-specific CD4+ and CD8+ responses from mice administered (1) saline; (2) 0.2 µg RNA encoding F647 ΔCT20 (codon optimised) – A subtype, A2 strain wildtype background sequence (“F647 A subtype RNA”); (3) 0.2 µg RNA encoding F647 ΔCT20 (codon optimised) – B subtype, M16 strain wildtype background sequence (“F647 B subtype RNA”); (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Total RSV A F-specific (A) CD4+ or (B) CD8+ T cell proportions were defined based on their Th0 / Tc0 (upward traveling diagonal lines), Th1 / Tc1 (vertical lines), Th2 / Tc2 (downward traveling diagonal lines), or Th17 / Tc17 (horizontal lines) phenotype. Data are displayed as the frequency (in %) of grandparents (CD4+ or CD8+) (n=6 / group). Cytokines were gated on time / live / lymphocytes / singlets / CD3+ CD4+ / CD44+ or CD8+ / CD44+, and phenotypic subsets were Docket No.: 70348WO01 determined as described in methods by the Boolean Combination Gate Tool and defined in Phenotype Subset. The geometric means (GM) with 95% confidence interval (CI) are displayed by phenotype. Figure 42. RSV B F-specific CD4+ and CD8+ responses from mice administered (1) saline; (2) 0.2 µg F647 A subtype RNA; (3) 0.2 µg F647 B subtype RNA; (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Total RSV B F-specific (A) CD4+ or (B) CD8+ T cell proportions were defined based on their Th0 / Tc0 (upward traveling diagonal lines), Th1 / Tc1 (vertical lines), Th2 / Tc2 (downward traveling diagonal lines), or Th17 / Tc17 (horizontal lines) phenotype. Data are displayed as the frequency (in %) of grandparents (CD4+ or CD8+) (n=6 / group). Cytokines were gated on time / live / lymphocytes / singlets / CD3+ CD4+ / CD44+ or CD8+ / CD44+, and phenotypic subsets were determined as described in methods by the Boolean Combination Gate Tool and defined in Phenotype Subset. The geometric means (GM) with 95% confidence interval (CI) are displayed by phenotype. Figure 43. T follicular helper (Tfh) and germinal center (GC) responses elicited by (1) saline; (2) 0.2 µg F647 A subtype RNA; (3) 0.2 µg F647 B subtype RNA; (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Horizontal bold lines are geometric means (GM) by group with 95% confidence interval (CI). (A) Total Tfh cells. Tfh cells were gated on time / live / lymphocytes / singlets / CD3+ / CD4+ / CD44+ / CXCR5+PD1+. (B) Total GC B cells (%). Germinal center B cells were gated on time / live / lymphocytes / singlets / CD3- / B220+CD19+ / IgM-IgD- / CD95+GL7+. (C) F647-Specific GC B cells. GC B cells were gated on time / live / lymphocytes / singlets / CD3- / B220+CD19+ / IgM-IgD- / CD95+GL7+ / F647. Figure 44. RSV A neutralizing antibody titers elicited by (1) saline; (2) 0.2 µg F647 A subtype RNA; (3) 0.2 µg F647 B subtype RNA; (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Neutralizing antibody titers were measured from serum collected on day 21. Each mouse is presented as a dot. The horizontal dotted line represents the Limit of Detection (LOD). Data with observed geometric mean titer (GMT) and 95% confidence interval (CI) by dose. Observed GMT values are noted at the bottom. Figure 45. RSV A neutralizing antibody titers elicited by (1) saline; (2) 0.2 µg F647 A subtype RNA; (3) 0.2 µg F647 B subtype RNA; (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Neutralizing antibody titers were measured from serum collected on day 35. Each mouse is presented as a dot. The horizontal dotted Docket No.: 70348WO01 line represents the Limit of Detection (LOD). Data with observed geometric mean titer (GMT) and 95% confidence interval (CI) by dose. Observed GMT values are noted at the bottom. Figure 46. RSV B neutralizing antibody titers elicited by (1) saline; (2) 0.2 µg F647 A subtype RNA; (3) 0.2 µg F647 B subtype RNA; (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Neutralizing antibody titers were measured from serum collected on day 21. Each mouse is presented as a dot. The horizontal dotted line represents the Limit of Detection (LOD). Data with observed geometric mean titer (GMT) and 95% confidence interval (CI) by dose. Observed GMT values are noted at the bottom. Figure 47. RSV B neutralizing antibody titers elicited by (1) saline; (2) 0.2 µg F647 A subtype RNA; (3) 0.2 µg F647 B subtype RNA; (4) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-formulated; (5) 0.2 µg of F647 A subtype RNA + 0.2 µg of F647 B subtype RNA, co-administered; (6) 0.4 µg F647 A subtype RNA; or (7) 0.4 µg F647 B subtype RNA. Neutralizing antibody titers were measured from serum collected on day 35. Each mouse is presented as a dot. The horizontal dotted line represents the Limit of Detection (LOD). Data with observed geometric mean titer (GMT) and 95% confidence interval (CI) by dose. Observed GMT values are noted at the bottom. Figure 48. Pre-F specific IgG binding antibody titers in rats administered RNA encoding F647 ΔCT20 (codon optimised), F647 recombinant protein plus AS01e adjuvant, or DS-Cav1 recombinant protein plus AS01e adjuvant , measured from serum collected on days 14, 28 and 42. The error bars represent the 95% CI. Each circle represents a single animal. Figure 49. Neutralizing antibody titers to RSV A2 in rats administered RNA encoding F647 ΔCT20 (codon optimised), F647 recombinant protein plus AS01e adjuvant, or DS-Cav1 recombinant protein plus AS01e adjuvant , measured from serum collected on days 14 and 42. The error bars represent the 95% CI. Each circle represents a single animal. References to “CTD” (cytoplasmic tail domain) in the figures are equivalent to references to “CT” (cytoplasmic tail) throughout this specification. Accordingly, “CTDΔ20” is equivalent to “ΔCT20”, and so forth. DETAILED DESCRIPTION RSV-F proteins The present disclosure provides, in a first independent aspect, an RSV-F protein, comprising at least two mutations relative to SEQ ID NO: 1 or 3 within a region of the protein corresponding to positions 474-523 of SEQ ID NO: 1 or 3; wherein the at least two mutations introduce, through substitution or insertion, a pair of C residues into the region, which form a disulphide bond. Docket No.: 70348WO01 The present disclosure also provides, in a second independent aspect, an RSV-F protein comprising a C residue at position 486 and a C residue at position 490; wherein the C residues form a disulphide bond. The present disclosure also provides, in a third independent aspect, a trimer comprising three RSV-F proteins according to said first and second independent aspects. Preferably, the trimer is a homotrimer. The homotrimer will generally comprise or consist of three RSV-F proteins, each of which comprise or consist of the same amino acid sequence. For the avoidance of doubt, RSV-F proteins according to said first and second independent aspects (including when in trimeric form according to said third independent aspect) are “RSV-F proteins of the present disclosure”, as referred to herein. Nucleic acids (e.g. RNA) which encode such RSV-F proteins are “nucleic acids of the present disclosure”, as referred to herein (or e.g. in preferred embodiments, “RNA of the present disclosure”, as referred to herein). The RSV-F sequences that are wild-type (in whole or in large part) according to SEQ ID NO: 1, 2, 3 and 4 are not “RSV-F proteins of the present disclosure” as referred to herein. Consequently, nucleic acids encoding SEQ ID NO: 1, 2, 3 or 4 are also not “nucleic acids of the present disclosure” as referred to herein. RSV-F proteins of the present disclosure and the mutations which they comprise (relative to a wild- type RSV-F protein), are “engineered”, in the sense that such mutations have been deliberately selected and introduced into the proteins, at least in part in order to enhance pre-fusion stability and / or expression from nucleic acids. RSV-F proteins of the present disclosure may also be considered “recombinant” (“engineered” and “recombinant” may be used interchangeably in this context). Accordingly, RSV-F proteins of the present disclosure are mutated relative to SEQ ID NO: 1 or 3. RSV-F proteins of the present disclosure are also mutated relative to SEQ ID NO: 2 or 4. SEQ ID NO: 1 is an RSV-F sequence from a strain of human RSV of the A2 subtype that contains two mutations (K66E and Q101P) relative to GenBank Accession number KT992094 (said mutations resulting from in vitro passaging, see

[0010] ). SEQ ID NO: 3 is the RSV-F sequence from B subtype strain M16 (GenBank accession no. ASU44512.1). SEQ ID NO: 2 and 4 are recombinant protein sequences comprising the wild-type sequence from SEQ ID NO: 1 and 2, respectively, up to position 513, and various domains (including a bacteriophage T4 fibritin foldon trimerisation domain) and linkers from position 514 onwards in place of inter alia, a transmembrane domain and cytoplasmic tail. SEQ ID NO: 1, 2, 3 and 4, and any wild-type RSV-F sequence (e.g. RSV-F proteins of other A or B subtype strains), are referred to herein as “wild-type”. SEQ ID NO: 5 and 6 may also be referred to as a “wild type cytoplasmic tail”. RSV-F proteins of the present disclosure may comprise mutations relative to SEQ ID NO: 1, 2, 3 or 4 found in RSV-F proteins from further strains and subtypes, both naturally-occurring and engineered (e.g. RSV-F proteins of further A subtype strains, or further B subtype strains). Hence, RSV-F proteins of the present disclosure may be of the RSV A or the RSV B Docket No.: 70348WO01 subtype. RSV-F proteins of the present disclosure may also have a specific degree of sequence identity to SEQ ID NO: 1, 2, 3 or 4, e.g. as detailed in the embodiments below. Where not otherwise specified, residue positions as defined throughout the present disclosure are numbered according to SEQ ID NO: 1, 2, 3 or 4, which will generally correspond to the residue numbering of the RSV-F protein of the present disclosure. For RSV-F proteins of the present disclosure comprising linker sequences joining their F1 and F2 domains (e.g. F651 a.k.a R715; SEQ ID NO: 32 / 73), residue numbering of the F1 domain will diverge from SEQ ID NO: 1, 2, 3 or 4. However, for ease of reference, substitutions in such RSV-F proteins relative to wild-type (e.g.486C, and so forth) are numbered according to SEQ ID NO: 1, 2, 3 or 4. References to a sequence / region of an RSV-F protein of the present disclosure “corresponding to positions x-y” of SEQ ID NO: 1, 2, 3 or 4 encompasses sequences / regions which align with positions x-y of SEQ ID NO: 1, 2, 3 or 4 (which, for the avoidance of doubt, includes positions x and y). However, in preferred embodiments, the mutations as defined throughout the present disclosure are introduced within positions x-y of SEQ ID NO: 1, 2, 3 or 4 (again, including positions x and y). Alignments may be performed visually, or by any well-known algorithm; e.g. using an NCBI BLAST algorithm, e.g. “blastp”, e.g. on default settings (available at https: / / blast.ncbi.nlm.nih.gov / Blast.cgi?PAGE=Proteins), or e.g. using the “Clustal Omega” algorithm (see, e.g.

[0011] ), e.g. on default settings; with the Clustal Omega algorithm being preferred. Corresponding residue positions (e.g. position 486 and so forth of SEQ ID NO: 1, 2, 3 or 4) are easily identifiable to the skilled person, and can be identified by aligning the amino acid sequences using any well-known method (visual or algorithm, e.g. as detailed above). As used herein, “heptad repeat A” (“HRA”) domain refers to positions 149-206 of SEQ ID NO: 1, 2, 3 or 4 and “heptad repeat C” (“HRC”) domain refers to positions 53-100 of SEQ ID NO: 1, 2, 3 or 4. As used herein, “Heptad repeat B” (“HRB”) domain refers to positions 474-523 of SEQ ID NO: 1 and 3, and positions 474-513 of SEQ ID NO: 2 and 4. RSV-F proteins of the present disclosure are preferably antigens (or, phrased differently, are antigenic). As such, RSV-F proteins of the present disclosure preferably elicit an immune response when administered in vivo, namely against RSV. The immune response may comprise an antibody response (usually including IgG) and / or a cell-mediated immune response, in particular an antibody response. The immune response will typically recognise the three-dimensional structure of the corresponding wild-type pre-fusion RSV-F, in particular one or more epitopes present on the (solvent-exposed) surface of the protein when in the pre-fusion conformation. Generally, RSV-F proteins of the present disclosure elicit a pre-fusion RSV-F-specific antibody response in vivo, e.g. an IgG antibody response (see, e.g. Examples 6, 11 and 14). Docket No.: 70348WO01 Generally, RSV-F proteins of the present disclosure elicit a neutralising antibody response against RSV (RSV A or B) in vivo, e.g. against RSV A (see, e.g. Examples 6, 11, 14, 15 and 16). Said neutralising antibody response may inhibit replication of RSV (such as RSV A or B) in the respiratory system of a subject, such as in the lungs. Said neutralising antibody response may yield protective immunity against RSV (RSV A or B) in a subject, e.g. against RSV A. Generally, RSV-F proteins of the present disclosure elicit a cross-neutralising antibody response against RSV in vivo, e.g. against strains of both RSV A and B subtypes (see, e.g. Examples 6, 15 and 16). Said cross-neutralising antibody response may yield protective immunity against strains of both RSV A and B subtypes in a subject. RSV-F proteins of the present disclosure may also be considered antigens (or, phrased differently, are antigenic) given their ability to be bound by antibodies AM14, D25, RSB1 and motavizumab (in particular AM14, D25 and RSB1, in particular AM14), e.g. with a dissociation constant (KD), as measured by SPR, of less than 10 nM, such as 1 pM – 10 nM, e.g. as detailed in the subsection below. The incorporation of both naturally and non-naturally occurring amino acids is envisaged in RSV-F proteins of the present disclosure, although naturally occurring amino acids are preferred. Pre-fusion conformation RSV-F proteins of the present disclosure are generally in the pre-fusion conformation (e.g. following expression from nucleic acids), and may generally be considered as stabilised in the pre-fusion conformation. The pre-fusion conformation of RSV-F proteins of the present disclosure may be confirmed via binding of pre-fusion RSV-F-specific monoclonal antibodies (“pre-fusion mAbs”). For example, RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a light chain and a heavy chain (LC and HC) selected from the group consisting of: SEQ ID NO: 7 and 8 respectively, SEQ ID NO: 9 and 10 respectively, and SEQ ID NO: 11 and 12 respectively. The foregoing are the LC and HC sequences of prefusion mAbs AM14, D25, and RSB1, respectively; see, e.g. [12, 13, 14]. Specific binding of the pre-fusion mAb(s) (or lack thereof) may be determined via surface plasmon resonance (“SPR”) or biolayer interferometry (“BLI”), however SPR is preferred. SPR may be performed using a BIACORE system; preferably as performed in the Examples (see subsection Binding kinetics using BIACORE). Generally, RSV-F proteins of the present disclosure may be specifically bound by any of the pre-fusion mAbs above with a dissociation constant (KD), as measured by SPR, of less than 10 nM, such as 1 pM – 10 nM; in particular less than 2 nM (2000 pM), such as 1- 2000 pM. For determining pre-fusion conformation via antibody binding, AM14 is preferred. Unlike the other pre-fusion mAbs, AM14 is specific for RSV-F in the pre-fusion conformation when in an intact trimer. Docket No.: 70348WO01 In particular embodiments, RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 7 and 8 respectively (or, defined differently, antibody AM14), with a KD, as measured via SPR, of: less than 1000, 900, 800, 700, 600, 500, 400, 350 or 320 pM; or, in some embodiments, less than 300, 200, 150, 100, 90, 80, 70, 60, 50, or 40 pM; or, in some embodiments, less than 35, 30, 25 or 20 pM. By way of example, RSV-F proteins according to present disclosure designated F528, F647, F651 are specifically bound by such a mAb with KDs, as measured via SPR, of 37.8, 309.5 and 18.9 pM respectively (see, e.g. Example 2, Table 5). RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 7 and 8 respectively (or, defined differently, antibody AM14) with a KD, as measured via SPR, in the range of: 1-1000, 1-900, 1-800, 1-700, 1-600, 1-500, 1-400, 1-350 or 1-320 pM (such as 10-1000, 10-900, 10-800, 10-700, 10-600, 10-500, 10-400, 10-350 or 10-320 pM); or, in some embodiments, 1-300, 1-200, 1-150, 1-100, 1-90, 1-80, 1-70, 1-60, 1-50, or 1-40 pM (such as 10-300, 10-200, 10-150, 10-100, 10-90, 10-80, 10-70, 10-60, 10-50, or 10- 40 pM); or, in some embodiments, 1-35, 1-30, 1-25 or 1-20 pM (such as 10-35, 10-30, 10-25 or 10-20 pM. In the foregoing embodiments in this paragraph, the RSV-F proteins of the disclosure are generally assembled in trimeric form, as a homotrimer. In particular embodiments, RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a LC and HC according SEQ ID NO: 9 and 10 respectively (or, defined differently, antibody D25), with a KD, as measured via SPR, of: less than 5000, 4000, 3000, 2500, 2000, 1900 or 1850 pM; or, in some embodiments, less than 1500, 1000, 800, 600, 400, 200, 100, 90, 80, 75 or 70 pM; or, in some embodiments, less than 65 pM. By way of example, RSV-F proteins according to present disclosure designated F528, F647, F651 are specifically bound by such a mAb with KDs, as measured via SPR, of 1840.4, 66.3 and 64.4 pM respectively (see, e.g. Example 2, Table 5). RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 9 and 10 respectively (or, defined differently, antibody D25) with a KD, as measured via SPR, in the range of: 1-5000, 1-4000, 1-3000, 1-2500, 1- 2000, 1-1900 or 1-1850 pM (such as 10-5000, 10-4000, 10-3000, 10-2500, 10-2000, 10-1900 or 10- 1850 pM); or, in some embodiments, 1-1500, 1-1000, 1-800, 1-600, 1-400, 1-200, 1-100, 1-90, 1-80, 1-75 or 1-70 pM (such as 10-1500, 10-1000, 10-800, 10-600, 10-400, 10-200, 10-100, 10-90, 10-80, 10-75 or 10-70); or, in some embodiments, 1-65 pM (such as 10-65 pM). In particular embodiments, RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 11 and 12 (or, defined differently, antibody RSB1) respectively with a KD, as measured via SPR, of: less than 1000, 500, 450, 400, 350, 300, 250, 200 or 190 pM; or, in some embodiments, less than 180, 170, 160, 150, 140, 130 or 125 pM; or, in some embodiments, less than 120, 100, 90, 80, 70 or 65 pM. By way of example, RSV-F proteins according to present disclosure designated F528, F647, F651 are specifically bound by such a mAb with KDs, as measured via SPR, of 189.1, 120.6 and 72.9 pM respectively (see, e.g. Example 2, Table Docket No.: 70348WO01 5). RSV-F proteins of the present disclosure may be specifically bound by a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 11 and 12 respectively (or, defined differently, antibody RSB1) with a KD, as measured via SPR, in the range of: 1-1000, 1-500, 1-450, 1-400, 1-350, 1-300, 1-250, 1-200 or 1-190 pM (such as 10-1000, 10-500, 10-450, 10-400, 10-350, 10-300, 10-250, 10-200 or 10-190 pM); or, in some embodiments, 1-180, 1-170, 1-160, 1-150, 1-140, 1-130 or 1-125 pM (such as 10-180, 10-170, 10-160, 10-150, 10-140, 10-130 or 10-125 pM); or, in some embodiments, 1-120, 1-100, 1-90, 1-80, 1-70 or 1-65 pM (such as 10-120, 10-100, 10-90, 10-80, 10- 70 or 10-65 pM). In an embodiment, RSV-F proteins of the present disclosure are specifically bound by: (i) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 7 and 8 respectively (or, defined differently, antibody AM14), with a KDof less than 100, 90, 80, 70, 60, 50, or 40 pM (such as 1-100, 1-90, 1-80, 1-70, 1-60, 1-50, or 1-40 pM); (ii) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 9 and 10 respectively (or, defined differently, antibody D25), with a KD of less than 3000, 2000, 1900 or 1850 pM (such as 1-3000, 1-2000, 1-1900 or 1-1850 pM); and / or (iii) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 11 and 12 respectively (or, defined differently, antibody RSB1), with a KDof less than 300, 250, 200 or 190 pM (such as 1-300, 1-250, 1-200 or 1-190 pM); wherein the KDis measured via SPR. In particular, the RSV-F protein of the present disclosure meets 2, or preferably all 3 of criteria (i), (ii) and (iii). By way of example, protein F528 meets all of said criteria (see, e.g. Example 2, Table 5). In an embodiment, RSV-F proteins of the present disclosure are specifically bound by: (iv) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 7 and 8 respectively (or, defined differently, antibody AM14), with a KD of less than 500, 400, 350 or 320 pM (such as 1-500, 1-400, 1-350 or 1-320 pM); (v) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 9 and 10 respectively (or, defined differently, antibody D25), with a KDof less than 100, 90, 80, 75 or 70 pM (such as 1-100, 1-90, 1-80, 1-75 or 1-70 pM); and / or (vi) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 11 and 12 respectively (or, defined differently, antibody RSB1), with a KD of less than 180, 170, 160, 150, 140, 130 or 125 pM (such as 1-180, 1-170, 1-160, 1-150, 1-140, 1-130 or 1- 125 pM); Docket No.: 70348WO01 wherein the KDis measured via SPR. In particular, the RSV-F protein of the present disclosure meets 2, or preferably all 3 of criteria (iv), (v) and (vi). By way of example, protein F647 meets all of said criteria (see, e.g. Example 2, Table 5). In an embodiment, RSV-F proteins of the present disclosure are specifically bound by: (vii) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 7 and 8 respectively (or, defined differently, antibody AM14), with a KD of less than 50, 40, 35, 30, 25 or 20 pM (such as 1-50, 1-40, 1-35, 1-30, 1-25 or 1-20 pM); (viii) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 9 and 10 respectively (or, defined differently, antibody D25), with a KDof less than 100, 90, 80, 75, 70 or 65 pM (such as 1-100, 1-90, 1-80, 1-75, 1-70 or 1-65 pM); and / or (ix) a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 11 and 12 respectively (or, defined differently, antibody RSB1), with a KD of less than 120, 100, 90, 80, 70 or 65 pM (such as 1-120, 1-100, 1-90, 1-80, 1-70 or 1-65 pM); wherein the KD is measured via SPR. In particular, the RSV-F protein of the present disclosure meets 2, or preferably all 3 of criteria (vii), (viii) and (ix). By way of example, protein F651 meets all of said criteria (see, e.g. Example 2, Table 5). Generally, RSV-F proteins of the present disclosure may be bound by a pre-fusion mAb (in particular, any of those defined above) over a time of, for example, at least: 24 hours, 1 week, 2 week, 3 weeks, 4 weeks, 5 weeks or 6 weeks, 7 weeks or 8 weeks; for example wherein the RSV-F protein is stored at 4° or 25°C in a buffer for said period(s) and then assayed to determine the presence or absence of specific binding of a pre-fusion mAb (in particular AM14 or D25), or an antigen binding fragment thereof (e.g. a Fab fragment thereof). Said binding over time may be determined via, for example, SPR or BLI. The buffer may be HEPES buffer, e.g. 20mM HEPES comprising 150mM NaCl. Thermostability (e.g. using Nano-DSF, e.g. as performed in the Examples) may also be assessed. Aggregation of the protein may also be assessed (e.g. via high-performance liquid chromatography (“HPLC”), e.g. as performed in the Examples). In an alternative, also preferred, method to mAb binding, the pre-fusion conformation of RSV-F proteins of the present disclosure may be confirmed via cryo-electron microscopy single particle analysis (“cryo-EM” – see e.g. Example 3, Figures 14 and 15), preferably when the protein is complexed with an antigen binding fragment of a pre-fusion mAb. Preferably, such cryo-EM comprises the steps: complexing the RSV-F protein of the present disclosure with an antigen binding fragment, such as a Fab fragment, of a pre-fusion mAb (preferably of AM14 or RSB1, preferably a Fab fragment of AM14 or RSB1) to form complexes; Docket No.: 70348WO01 isolating (e.g. via gel filtration) and concentrating said complexes; depositing said complexes onto an electron microscopy grid, and vitrifying the complexes and grid (e.g. via plunge freezing into liquid ethane); imaging via electron microscopy; and solving the structure of said complexes via single particle analysis. More preferably, such cryo-EM is performed as in the Examples (see Example 3 and associated Materials and Methods). Disulphide bond RSV-F proteins of the present disclosure comprise (according to the first, second and third independent aspects) a disulphide bond formed between two, generally non-naturally occurring, C residues. According to the first independent aspect of the present disclosure, a pair of C residues is introduced into the region of the RSV-F protein corresponding to positions 474-523 of SEQ ID NO: 1 or 3 (a.k.a. the HRB domain) which form a disulphide bond. Preferably, this is an intra-protomer disulphide bond (i.e. linking two C residues within the same protomer). The presence of an intra-protomer disulphide bond may be confirmed via e.g. (i) cryo-EM (e.g. using the method set out in the preceding subsection, in particular as performed in Example 3), or (ii) X-ray crystallography (e.g. performed in accordance with the method in

[0015] ). The pair of C residues may be within the region corresponding to positions 474-513 of SEQ ID NO: 1 or 3. For example, when in recombinant protein form, position 513 is the typical C-terminal residue of the HRB domain, prior to, typically, a linker sequence connecting the HRB domain to a trimerisation domain (e.g. a bacteriophage T4 fibritin foldon trimerisation domain, e.g. according to SEQ ID NO: 19) and other sequences as needed. In some embodiments, a first C residue of said pair may be within a region of the RSV-F protein corresponding to positions 478-501 of SEQ ID NO: 1 or 3, and / or (optionally and) a second C residue of said pair may be within a region corresponding to positions 482-504 of SEQ ID NO: 1 or 3. Examples of such C residue pairs include those at positions: 486 and 490, 485 and 494, 480 and 497, 490 and 494, 479 and 482, 484 and 498, 487 and 490, 491 and 494, 482 and 502, 478 and 483, 481 and 501, 482 and 499, 486 and 489, 486 and 488, 485 and 494, 480 and 487, or 501 and 504 of SEQ ID NO: 1 or 3. C residues in these positions were (i) computationally predicted to form intra-protomer disulphide bonds, based on a distance criterion of 5Å between Cβ atoms in the RSV-F pre-fusion conformation (see e.g. Example 5); and / or (ii) are present in designs F526, F527 and F528 (see e.g. Example 1) . In some embodiments, a first C residue of said pair may be within a region of the RSV-F protein corresponding to positions 478-491 of SEQ ID NO: 1 or 3, and / or (optionally and) a second C residue of said pair may be within a region corresponding to positions 482-502 of SEQ ID NO: 1 or 3. Examples of such C residue pairs include those at positions: 486 and 490, 485 and 494, 480 and 497, Docket No.: 70348WO01 490 and 494, 479 and 482, 484 and 498, 487 and 490, 491 and 494, 482 and 502, or 478 and 483 of SEQ ID NO: 1 or 3. C residues in these positions were (i) computationally predicted to form intra- protomer disulphide bonds, based on a distance criterion of 5Å between Cβ atoms in the RSV-F pre- fusion conformation and (ii) stabilise said conformation (see e.g. Example 5); and / or are present in designs F526, F527 and F528 (see e.g. Example 1) . In particular embodiments, a first C residue of said pair is within a region of the RSV-F protein corresponding to positions 480-486 of SEQ ID NO: 1 or 3, and / or (optionally and) a second C residue of said pair is within a region corresponding to positions 490-497 of SEQ ID NO: 1 or 3. Examples of such C residue pairs include those at positions: 486 and 490, 485 and 494, or 480 and 497 of SEQ ID NO: 1 or 3. As detailed in e.g. Example 1 (see, e.g. Figures 1 and 2), designs F526, F527 and F528 demonstrated higher expression levels and pre-fusion mAb binding compared to other non-control constructs comprising engineered disulphide bonds (see Table 3). Preferably, the pair of C residues is at positions 486 and 490 of SEQ ID NO: 1 or 3. In Example 1, design F528 (486:490 disulphide bond) demonstrated the highest expression level of all constructs tested (both control and non-control), and comparable or greater prefusion mAb binding than controls DS-Cav1, F(i) and F(ii). The 486:490 disulphide bond was confirmed to be intra-protomer by cryo-EM in Example 3. According to the second independent aspect of the present disclosure, the RSV-F protein comprises a C residue at position 486 and a C residue at position 490, which form a disulphide bond. Said residue numbering will typically correspond to that of SEQ ID NO: 1 or 3. Preferably, this disulphide bond is an intra-protomer disulphide bond, the presence of which may be confirmed using the methods detailed above in relation to the first independent aspect of the present disclosure. Generally, the substitutions for / insertions of C residues (and the resulting disulphide bond) detailed throughout this subsection may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. In addition to the substitutions for / insertions of C residues, and the resulting disulphide bond detailed throughout this subsection, preferably, RSV-F proteins of the present disclosure do not comprise a deletion of position 137. Such RSV-F proteins of the present disclosure preferably comprises neither (i) a deletion of the fusion peptide (in whole), nor (ii) substitution of the fusion peptide (in whole) for a linker sequence e.g. GSGSG (SEQ ID NO: 16), GSGSGRS (SEQ ID NO: 17), or GS (SEQ ID NO: 18). Such RSV-F proteins of the present disclosure preferably comprise (i) a deletion of p27 (in whole) and the fusion peptide (in whole), nor (ii) substitution of p27 (in whole) and the fusion peptide (in whole) for a linker sequence e.g. GSGSG (SEQ ID NO: 16), GSGSGRS (SEQ ID NO: 17), or GS (SEQ ID NO: 18). Such RSV-F proteins of the present disclosure preferably comprise: (a) an aromatic residue at position 137 (such as F, W, Y or H; optionally F, W or Y; optionally F); (b) an aromatic residue at position 488 (such as F, W, Y or H; optionally F, W or Y; optionally F); and / or (c) a positively charged residue at position 339 (such as K, R or H, optionally K or R, optionally K); and Docket No.: 70348WO01 preferably all of (a), (b) and (c). Such RSV-F proteins of the present disclosure preferably comprise a pi-pi stacking interaction between (a) and (b), and preferably comprise a pi-pi-cation stacking interaction between (a), (b) and (c). In such RSV-F proteins of the present disclosure, the (preferably intra-protomer) disulphide bond is preferably formed by a C residue at position 486 and a C residue at position 490 (as per preferred embodiments of the first independent aspect of the present disclosure, or as per the second independent aspect of the present disclosure). As detailed in e.g. Example 12, cryo-EM analysis of design F647 demonstrated that the 486:490 disulphide bond repositions the side chain of wild-type aromatic residue F488 to introduce a pi-pi stacking interaction with wild-type residue aromatic F137 in the fusion peptide (see, e.g. Figures 36 A and D). This additional interaction (over wild-type) resulted in a cation-pi-pi trio-stacking interaction between residues K339, F137 and F488, which further restricts movement of the fusion peptide, thereby helping to stabilise the pre-fusion conformation of RSV-F (see, e.g. Figures 36C and D). For the avoidance of doubt, features detailed in this paragraph are not applicable to RSV-F proteins of the present disclosure comprising linker sequences joining their F1 and F2 domains (e.g. F651 a.k.a R715; SEQ ID NO: 32 / 73). Deletions and residue positioned identified in this paragraph are relative to and numbered according to SEQ ID NO: 1, 2, 3 or 4, which will generally correspond to the residue numbering of the RSV-F protein of the present disclosure. As exemplified in e.g. Example 3 (Figures 14-15), when in trimeric form (according to the third independent aspect of the present disclosure), RSV-F proteins of the present disclosure may comprise an electrostatic repulsive ring comprising three negatively residues, each of which is in the HRB domain of an RSV-F protein in the trimer. The negatively charged residues are typically at position 487 of each of the RVF-proteins, and may be E or D residues, typically E residues. As a result of the disulphide bond in RSV-F proteins of the present disclosure, the distances between each of the negatively-charged residues in the trimer may be increased relative to such distances in a trimer comprising three RSV-F proteins comprising or consisting of SEQ ID NO: 1, 2, 3 or 4 (i.e. wild-type trimers), as exemplified in e.g. Example 3, Figure 15. In RSV-F proteins of the present disclosure, such distances may be at least 5.0, 5.5, 6.0, 6.5, 7.0, 7.2 or 7.4 Å (or e.g. 5.0-8.0 Å, such as 6.0-8.0, 6.5-7.5 or 7.0-7.5 Å). Such distances may be assessed e.g. using cryo-EM, (e.g. using the method set out in the preceding subsection, in particular as performed in Example 3). In wild type, such distances are generally lower, such as 4.3 Å (see e.g. Figure 15 D). The resulting reduction in electrostatic repulsive forces in RSV-F proteins of the present disclosure (relative to wild-type) inhibits, at least partly inhibits, or completely inhibits, the transition from pre-fusion to post-fusion conformation of RSV-F In addition to the substitutions for / insertions of C residues, and the resulting disulphide bond, detailed throughout this subsection, RSV-F proteins of the present disclosure preferably comprise one or more further mutations (relative to wild type, e.g. SEQ ID NO: 1 or 3), such as at least 2, 3, 4, 5, 6 or 7 further mutations. Generally, the one or more further mutations are, or comprise, one or more Docket No.: 70348WO01 substitutions (relative to wild type, e.g. SEQ ID NO: 1 or 3), such as at least 2, 3, 4, 5, 6 or 7 further substitutions. Generally, the one or more further mutations / substitutions stabilise and / or promote the pre-fusion conformation of RSV-F. In some embodiments, the one or more mutations are, or comprise, the substitutions 103C, 148C and 190I, or 103C, 148C, 190I and 486S (optionally numbered according to SEQ ID NO: 1 or 3). In some embodiments, the one or more mutations are, or comprise, the substitutions 67I and 215P (optionally numbered according to SEQ ID NO: 1 or 3). In some embodiments, the one or more mutations are, or comprise, the substitutions 66E, 67I, 76V, 215P and 486G (optionally numbered according to SEQ ID NO: 1 or 3). In some embodiments, the one or more mutations are, or comprise, the substitutions 149C, 155C, 190F, 207L, 290C and 458C (optionally numbered according to SEQ ID NO: 1 or 3), optionally with a linker sequence joining the F2 and F1 domains of the RSV-F protein (e.g. GS / SEQ ID NO: 18). In some embodiments, the one or more mutations are, or comprise, the substitutions 102A, 149C, 155C, 190F, 207L, 290C, 373R, 379V, 447V and 458C (optionally numbered according to SEQ ID NO: 1 or 3), optionally with a linker sequence joining the F2 and F1 domains of the RSV-F protein (e.g. GS / SEQ ID NO: 18). In some embodiments, the one or more mutations are, or comprise, the substitutions 155C, 190F, 207L and 290C (optionally numbered according to SEQ ID NO: 1 or 3). Preferably, the one or more mutations are, or comprise, those set out in the following four subsections. Further mutations – positions 228 and / or 232 According to all independent aspects of the present disclosure, in preferred embodiments, RSV-F proteins of the present disclosure comprise a substitution at position 228 for K, R or Q (optionally K or R), and / or a substitution at position 232 for N. In preferred embodiments, RSV proteins of the present disclosure comprise a substitution at position 228 for K, R or Q (optionally K or R). In such embodiments, it is more preferred that RSV proteins of the present disclosure comprise a substitution at position 228 for K (e.g. as found in designs such as F217, F528 and F647). In the foregoing embodiments in which position 228 is substituted, preferably position 232 has either the wild-type residue (E),or is substituted for D (also a negatively charged residue). E or D at position 232 may help to provide a tertiary cation-pi-anion interaction discussed below. In the foregoing embodiments in this paragraph, preferably position 250 has either the wild-type residue (Y), or is substituted for D. Such substitutions at position 228 and / or 232 may be the only mutation(s) in the region of the RSV-F protein corresponding to positions 217-239 of SEQ ID NO: 1 or 3, relative to a corresponding wild- type region, e.g. positions 217-239 of SEQ ID NO: 1 or 3. As detailed in Example 7, a minimal substitution screen revealed the 228K substitution alone to be able to achieve pre-fusion RSV-F (see Figure 26; design F310). Without wishing to be bound by this theory, K at position 228 appears to result in an H bond with Y250 on the same protomer (see Figure 19, dashed line indicating hydrogen bond). Said H bonding may stabilise Y250 to form a tertiary cation-pi-anion interaction between E232, Y250 and R235 (E232 and Y250 being on one protomer, with R235 being on an adjacent protomer). E, Y and R are one of the dominant triads for such a tertiary Docket No.: 70348WO01 cation-pi-anion interaction (see, e.g.

[0016] ). Furthermore, residues with other H bond donors in their side chains (such as R, Q or N, in particular R) at position 228 may also provide this stabilising H bond with Y250. In addition, based on the proximity and orientation of the E232 side chain (see Figure 19), substitution for N may also provide a stabilising hydrogen bond with Y250. In all foregoing embodiments in this subsection, optionally RSV-F proteins of the present disclosure may comprise a substitution at position 250 for D. A 250D substitution may strengthen a cross- protomer interaction with R235 (wild-type residue) by forming a salt bridge between the two residues. For an example of an engineered cross-protomer salt bridge between D and R residues to stabilise a multimeric protein in a pre-fusion conformation, see

[0017] (Figure 1; D961–R765 salt bridge). Furthermore, D comprises an H bond acceptor moiety and so the Y250D substitution would maintain the preferred hydrogen bond between positions 250 and 228. Generally, the substitutions detailed throughout this subsection may provide core stabilisation in the F1 domain (positions 137-513 of SEQ ID NO: 1 or 3), proximal to the heptad repeat A (“HRA”) domain and antibody binding site Ø (”site Ø”). Generally, the substitutions detailed throughout this subsection may provide a H bond with Y250, e.g. which stabilises Y250 to provide a tertiary cation-pi-anion interaction between positions (i) 232 (preferably E232, as in wild-type, or D232 if substituted), (ii) Y250 and (ii) R235 across different RSV-F protomers. Such core stabilisation, H bonds and / or tertiary anion-pi-cation interactions may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Generally, the substitutions detailed throughout this subsection may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Further mutations – position 55 According to all independent aspects of the present disclosure, in preferred embodiments, RSV-F proteins of the present disclosure comprise a substitution at position 55 for T, C, V, I or F (optionally T, C or V; optionally T or C). In such embodiments, it is preferred that RSV proteins of the present disclosure comprise a substitution at position 55 for T (e.g. as found in designs such as F217, F528 and F647). Such substitutions at position 55 may be the only mutation(s) in the region of the RSV-F protein corresponding to positions 38-60 of SEQ ID NO:1 or 3 relative to a corresponding wild-type region, e.g. positions 38-60 of SEQ ID NO: 1 or 3. As detailed in Example 7, a minimal substitution screen revealed the S55T substitution to be a likely driver of the pre-fusion conformation (see Figure 26; design F308). Without wishing to be bound by this theory, T in place of S (wild-type) at position 55 provides a slightly larger residue which (from in silico three-dimensional structural analysis, see Figure 20) appears to be accommodated well in the hydrophobic pocket discussed above, without generating significant steric clashes. Moreover, the addition of the CH3 group of T appears to provide new, energetically favourable VDW contacts of the Docket No.: 70348WO01 type discussed above. Furthermore, alternative substitutions provided for position 55 by ROSETTA software include C and V (based on all amino acids being allowed (no evolutionary constraints) with energy thresholds of 0.0, -0.1 or -0.5 being used). Generally, the substitutions detailed throughout this subsection may stabilise the interface between the F1 domain (positions 137-523 of SEQ ID NO: 1 or 3) and the heptad repeat A (“HRA”) domain. Such stabilization may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Generally, the substitutions detailed throughout this subsection may provide energetically-favourable Van der Waals (VDW) contacts within a hydrophobic pocket of RSV-F, at the interface between the F1 domain and the HRA domain. Such contacts may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Generally, the substitutions detailed throughout this subsection may inhibit refolding of the HRA and HRC domains. Such refolding may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Generally, the substitutions detailed throughout this subsection may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Further mutations – position 215 According to all independent aspects of the present disclosure, in preferred embodiments, RSV-F proteins of the present disclosure comprise a substitution at position 215 for A, P, V, I, or F (optionally A or P). In such embodiments, it is preferred that RSV proteins of the present disclosure comprise a substitution at position 215 for A (e.g. as found in designs such as F217, F528 and F647). Such substitutions at position 215 may be the only mutation(s) in the region of the RSV-F protein corresponding to positions 208-216 of SEQ ID NO:1 or 3 relative to a corresponding wild-type region, e.g. positions 38-60 of SEQ ID NO: 1 or 3. In other embodiments, RSV-F proteins of the present disclosure may comprise a substitution at position 211 and / or (optionally and) position 216 for P (see e.g. designs in Example 2). As detailed in Example 7, a minimal substitution screen revealed the S215A substitution to be a likely driver of the pre-fusion conformation (see Figure 26; design F309). Without wishing to be bound by this theory, removal of the hydrophilic OH group, as S (wild-type) is substituted for A, is likely favourable to the packing and rigidity of the loop (see Figure 21). Furthermore, the A residue at position 215 may provide energetically-favourable VDW contacts with positions 79, 206, 203, and / or T219. Such packing, rigidification and / or VDW contacts may inhibit, at least partly inhibit, or completely inhibit the transition from pre-fusion to post-fusion conformation of RSV-F (in particular, inhibition of the relative motion of the two α helices adjacent to the loop (generally the α4 and α5 helices of RSV-F), or, defined differently, inhibition of refolding of the HRC and HRA domains). Furthermore, the side chains of P, V, I or F may also reduce conformational freedom of the loop, thus also being favourable to the packing and rigidification of the loop. Docket No.: 70348WO01 Generally, the substitutions detailed throughout this subsection may stabilise or rigidify the loop corresponding to positions 208-216 of SEQ ID NO: 1 or 3. Such stabilisation or rigidification may inhibit, at least partly inhibit, or completely inhibit, the transition of RSV-F from pre-fusion to post- fusion conformation (in particular, by inhibiting the relative motion of the two α helices adjacent to the loop, generally the α4 and α5 helices of RSV-F). Generally, the substitutions detailed throughout this subsection may inhibit, at least partly inhibit, or completely inhibit, the transition of RSV-F from pre-fusion to post-fusion conformation (in particular, by inhibiting of the relative motion of the two α helices adjacent to the loop (generally the α4 and α5 helices of RSV-F), or, defined differently, by inhibiting refolding of the HRC and HRA domains). Combinations of substitutions According to all independent aspects of the present disclosure, RSV-F proteins of the present disclosure preferably comprise combinations of substitutions as detailed in the preceding three subsections, such as: a substitution at position 228 for K, R or Q (optionally K or R; wherein substitution for K is preferred); a substitution at position 55 for T, C, V, I (optionally T, C or V; optionally T or V, wherein substitution for T is preferred); and a substitution at position 215 for A, P, V, I, or F (optionally A, V, I, or F; optionally A or P; wherein substitution for A is preferred). In addition, RSV-F proteins of the present disclosure preferably comprise further substitutions, such as: a substitution at position 152 for R, L or W (optionally R or W; wherein substitution for R is preferred); a substitution at position 315 for I or V (wherein substitution for I is preferred); a substitution at position 346 for Q, D, H, K, N, R, S or W (optionally Q, D, H, K, N, R or S; wherein substitution for Q is preferred); a substitution at position 445 for D; a substitution at position 455 for V or I (wherein substitution for V is preferred); and / or a substitution at position 459 for M; in particular: a substitution at position 152 for R, L or W (optionally R or W; wherein substitution for R is preferred); Docket No.: 70348WO01 a substitution at position 315 for I or V (wherein substitution for I is preferred); a substitution at position 346 for Q, D, H, K, N, R, S or W (optionally Q, D, H, K, N, R or S; wherein substitution for Q is preferred); a substitution at position 445 for D; a substitution at position 455 for V or I (wherein substitution for V is preferred); and a substitution at position 459 for M; in particular: a substitution at position 152 for R; a substitution at position 315 for I; a substitution at position 346 for Q; a substitution at position 445 for D; a substitution at position 455 for V; and a substitution at position 459 for M. As such, RSV-F proteins of the present disclosure may, in preferred embodiments, comprise: a substitution at position 55 for T; a substitution at position 152 for R; a substitution at position 215 for A; a substitution at position 228 for K; a substitution at position 315 for I; a substitution at position 346 for Q; a substitution at position 445 for D; a substitution at position 455 for V; and a substitution at position 459 for M; more preferably: a substitution at position 55 for T; a substitution at position 152 for R; a substitution at position 215 for A; Docket No.: 70348WO01 a substitution at position 228 for K; a substitution at position 315 for I; a substitution at position 346 for Q; a substitution at position 445 for D; a substitution at position 455 for V; a substitution at position 459 for M; a substitution at position 486 for C; and a substitution at position 490 for C. In some embodiments, RSV-F proteins of the present disclosure further comprise a substitution at position 211 for N and / or (optionally and) a substitution at position 348 for N. Generally, further substitutions as detailed throughout this subsection may inhibit, at least partly inhibit, or completely inhibit, the transition from pre-fusion to post-fusion conformation of RSV-F. Melting temperature When in the form of a homotrimer (e.g. according to the third independent aspect of the present disclosure), RSV-F proteins of the present disclosure may have a first melting temperature (Tm1) of at least 65.0 °C, such as at least 65.5, 66.0, 66.5, 67.0, 67.5, 68.0, 68.5, 69.0, 69.5, 70.0, 70.5, 71.0, 71.5, 72.0, 72.5, 73.0, 73.5, or 74.0 °C. The Tm1 may be 65.0-80.0°C, such as 70.0-80.0, 70.0-75.0, 71.0- 75.0, 72.0-75.0, 73.0-75.0, 73.0-74.5, 73.5-74.5 or 74.0-74.5 °C. In some embodiments, the Tm1 may be at least, or may be, 65.7°C (see, e.g. Example 2, design F651). In some embodiments, the Tm1 may be at least, or may be, 72.3 °C (see, e.g. Example 2, design F528). In some embodiments, the Tm1 may be at least, or may be, 74.4 °C (see, e.g. Example 2, design F647). When in the form of a homotrimer (e.g. according to the third independent aspect of the present disclosure), RSV-F proteins of the present disclosure may have a second melting temperature (Tm2) of at least 78.0 °C, such as at least 78.5, 79.0, 79.5.5, 80.0, 80.5, 81.0, 81.5, 82.0, 82.5, 83.0, or 83.5. The Tm2 may be 78.0-90.0°C, such as 78.0-85.0, 79.0-85.0, 80.0-85.0, 80.0-84.0, 81.0-84.0, 82.0-84.0, 83.0-84.0, or 83.0-83.5 °C. In some embodiments, the Tm2 may be at least, or may be, 80.8 °C; and optionally the Tm1 may be at least, or may be, 65.7°C (see, e.g. Example 2, design F651). In some embodiments, the Tm2 may be at least, or may be, 79.4 °C; and optionally the Tm1 may be at least, or may be, 72.3 °C (see, e.g. Example 2, design F528). In some embodiments, the Tm2 may be at least, or may be, 80.7 °C; and optionally the Tm1 may be at least, or may be, 74.4 °C (see, e.g. Example 2, design F647). The Tm1 and / or Tm2 may be determined via differential scanning fluorimetry (DSF), preferably nanoDSF (e.g. using a PROMETHEUS NT.48 instrument from NANOTEMPER TECHNOLOGIES), Docket No.: 70348WO01 preferably as determined in the Examples (see Examples 1 and 2, nanoDSF experiments, and associated materials and methods). DSF measures protein unfolding events resulting from increasing temperature by monitoring changes in fluorescence, generally corresponding to the exposure of W or Y residues which were previously buried in the protein structure. With nanoDSF, fluorescence may be measured as the ratio of the recorded emission intensities (Em350 nm / Em330 nm). The Tm1 may be determined by exposing the RSV-F protein trimer to an increasing temperature (e.g. from 25 to 95°C, e.g. at a ramp rate of 1°C / min) and measuring the temperature at which a first peak in fluorescence occurs (see e.g. Figure 22A-C for examples). The Tm2 may be determined by exposing the RSV-F protein trimer to an increasing temperature (e.g. from 25 to 95°C, e.g. at a ramp rate of 1°C / min) and measuring the temperature at which a second peak in fluorescence occurs (see e.g. Figure 22A-C for examples). When assessing the Tm1 and / or Tm2, typically the RSV-F protein comprises trimerisation domain at the C-terminus thereof, and / or C-terminal to the F1 domain (e.g. a bacteriophage T4 fibritin foldon trimerisation domain, e.g. according to SEQ ID NO: 19). The RSV-F protein may comprise a C- terminal domain comprising or consisting of positions 514-596 of SEQ ID NO: 2 or 4. General sequence features of RSV-F proteins in the pre-fusion conformation (protein per se) When considering protein per se (e.g. a mature, furin-processed protein), RSV-F proteins of the present disclosure generally have two domains (in the N-terminal to C-terminal direction, an “F2” domain and an “F1” domain), which may or may not be linked via peptide bonds (although in the wild-type protein they are not so linked; linkage typically occurring through disulphide bonds). RSV-F proteins of the present disclosure may comprise or consist of (i) an F2 domain comprising or consisting of an amino acid sequence having at least 70% sequence identity to positions 26-109 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1), such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98% or 99% sequence identity to positions 26-109 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1); and (ii) an F1 domain comprising or consisting of an amino acid sequence having at least 70% sequence identity to positions 137-513 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1), such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99% or 99.5% sequence identity to positions 137-513 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1). In some embodiments, RSV-F proteins of the present disclosure comprising an E residue at position 66, and a P residue at position 101 of SEQ ID NO: 1 or 3. In preferred embodiments (such as the mature, furin processed protein), a signal peptide is not present in the RSV-F protein of the present disclosure, optionally as a result of signal peptide cleavage, optionally wherein the signal peptide is positions 1-25 of SEQ ID NO: 1 or 3. In preferred embodiments (such as the mature, furin processed protein), a p27 peptide is not present in RSV-F Docket No.: 70348WO01 proteins of the present disclosure, optionally as a result of furin cleavage, optionally wherein the p27 peptide is positions 110-136 of SEQ ID NO: 1 or 3. In some embodiments, the p27 peptide may still be present as a result of furin cleavage at only one site, e.g. the p27 peptide is linked via a peptide bond to one of the F2 or F1 domains. In embodiments wherein the F2 and F1 domains are linked via peptide bonds (e.g. those of an intervening amino acid sequence), they may be linked by a linker sequence. The linker sequence will join the C and N terminal regions / residues of said F2 and F1 domains. The linker sequence may be glycine-serine rich or consist of G and S residues, for example GSGSG (SEQ ID NO: 16), GSGSGRS (SEQ ID NO: 17), or GS (SEQ ID NO: 18). In one particular embodiment, the F2 and F1 domains may be linked by a linker sequence comprising or consisting of SEQ ID NO: 18. In embodiments wherein the F2 and F1 domains are not linked via peptide bonds, they may be linked by at least one disulphide bond (typically two such bonds, which are typically naturally-occurring, e.g. as in the wild- type protein). RSV-F proteins of the present disclosure (protein per se) generally comprise a heterologous trimerisation domain on the C-terminus thereof (“heterologous” meaning not being native to the viral protein). The trimerisation domain may be positioned C-terminal to the F1 domain. A trimerisation domain is a sequence which promotes assembly of RSV-F proteins of the present disclosure (i.e. individual promoters) into trimers, namely in particular via associations with other trimerisation domains (i.e. those on other protomers). Trimerisation domains may, in some embodiments, fold into a coiled-coil. Exemplary trimerisation domains include: a T4 fibritin foldon domain; a yeast GCN4 isoleucine zipper, e.g. according to SEQ ID NO: 39 (or an amino acid sequence, in particular having a trimerisation function, at least 50%, 60%, 70%, 80%, 90% or 95% identical thereto); TRAF2 (GENBANK Accession No. Q12933 [gi:23503103]; amino acids 299-348); Thrombospondin 1 (Accession No. PO7996 [gi:135717]; amino acids 291-314); Matrilin-4 (Accession No. 095460 [gi:14548117]; amino acids 594-618; CMP (matrilin-1) (Accession No. NP_002370 [gi:4505111]; amino acids 463-496; HSF1 (Accession No. AAX42211 [gi:61362386]; amino acids 165-191; Cubilin (Accession No. NP_001072 [gi:4557503]; amino acids 104-138); a trimerisation domain from an influenza hemagglutinin; a trimerisation domain from a SARS spike protein, a trimerisation domain from HIV gp41; NadA; and ATCase Preferably, the trimerisation domain is a T4 fibritin foldon domain, more preferably comprising or consisting of an amino acid sequence according to SEQ ID NO: 19 (or a trimerizing amino acid sequence at least 50%, 60%, 70%, 80%, 90% or 95% identical thereto). The trimerisation domain is generally linked to the C-terminus of the F1 domain via a linker sequence. Said linker sequence may comprises or consists of an amino acid sequence according to SEQ ID NO: 20 (or an amino acid sequence at least 50% or 75% identical thereto). In a preferred embodiment, RSV-F proteins of the present disclosure comprise: (i) an F2 domain comprising or consisting of an amino acid sequence according to positions 26-109 of SEQ ID NO: 24 and an F1 domain comprising or consisting of an amino acid sequence according to positions 137-513 Docket No.: 70348WO01 of SEQ ID NO: 24; or (ii) an F2 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98% or 99% identity to positions 26-109 of SEQ ID NO: 24, and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99% or 99.5% to positions 137-513 of SEQ ID NO: 24, wherein the RSV- F protein preferably comprises the substitutions 55T, 152R, 211N, 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C and 490C relative to wild-type F2 and F1 domains, e.g. according to positions 26-109 and 137-513 of SEQ ID NO: 1 or 3. In such embodiments, RSV-F proteins of the present disclosure generally comprise a heterologous trimerisation domain C-terminal to the F1 domain; e.g. a T4 fibritin foldon domain e.g. according to SEQ ID NO: 19, or a trimerising amino acid sequence at least 50%, 60%, 70%, 80%, 90% or 95% identical to SEQ ID NO: 19. In a preferred embodiment, RSV-F proteins of the present disclosure comprise: (i) an F2 domain comprising or consisting of an amino acid sequence according to positions 26-102 of SEQ ID NO: 32 and an F1 domain comprising or consisting of an amino acid sequence according to positions 105-472 of SEQ ID NO: 32; or (ii) an F2 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98% or 99% identity to positions 26-102 of SEQ ID NO: 32, and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5% to positions 105-472 of SEQ ID NO: 32, wherein the RSV-F protein preferably comprises the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to wild-type F2 and F1 domains, e.g. according to positions 26-109 and 137-513 of SEQ ID NO: 1 or 3, and wherein the RSV-F protein preferably comprises a linker sequence joining the F1 and F2 domains which is preferably a GS linker (SEQ ID NO: 18). In such embodiments, RSV- F proteins of the present disclosure generally comprise a heterologous trimerisation domain C-terminal to the F1 domain; e.g. a T4 fibritin foldon domain e.g. according to SEQ ID NO: 19, or a trimerising amino acid sequence at least 50%, 60%, 70%, 80%, 90% or 95% identical to SEQ ID NO: 19. In a more preferred embodiment, RSV-F proteins of the present disclosure comprise: (i) an F2 domain comprising or consisting of an amino acid sequence according to positions 26-109 of SEQ ID NO: 28 and an F1 domain comprising or consisting of an amino acid sequence according to positions 137-513 of SEQ ID NO: 28; or (ii) an F2 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98% or 99% identity to positions 26-109 of SEQ ID NO: 28, and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99% or 99.5% to positions 137-513 of SEQ ID NO: 28, wherein the RSV- Docket No.: 70348WO01 F protein preferably comprises the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to wild-type F2 and F1 domains, e.g. according to positions 26-109 and 137-513 of SEQ ID NO: 1 or 3. In such embodiments, RSV-F proteins of the present disclosure generally comprise a heterologous trimerisation domain C-terminal to the F1 domain; e.g. a T4 fibritin foldon domain e.g. according to SEQ ID NO: 19, or a trimerising amino acid sequence at least 50%, 60%, 70%, 80%, 90% or 95% identical to SEQ ID NO: 19. In other embodiments, RSV-F proteins of the present disclosure comprise: - (i) an F2 and an F1 domain according to positions 26-109 and 137-513, respectively, of SEQ ID NO: 25; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-109 and 137-513 of SEQ ID NO: 25, relative to positions 26-109 and 137-513 of SEQ ID NO: 1; - (i) an F2 and an F1 domain according to positions 26-109 and 137-513, respectively, of SEQ ID NO: 27; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-109 and 137-513 of SEQ ID NO: 27, relative to positions 26-109 and 137-513 of SEQ ID NO: 1; - (i) an F2 and an F1 domain according to positions 26-109 and 137-513, respectively, of SEQ ID NO: 29; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-109 and 137-513 of SEQ ID NO: 29, relative to positions 26-109 and 137-513 of SEQ ID NO: 1; - (i) an F2 and an F1 domain according to positions 26-109 and 137-513, respectively, of SEQ ID NO: 30; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-109 and 137-513 of SEQ ID NO: 30, relative to positions 26-109 and 137-513 of SEQ ID NO: 1; - (i) an F2 and an F1 domain according to positions 26-109 and 137-513, respectively, of SEQ ID NO: 39; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally Docket No.: 70348WO01 comprising the substitutions present in positions 26-109 and 137-513 of SEQ ID NO: 39, relative to positions 26-109 and 137-513 of SEQ ID NO: 1; - (i) an F2 and an F1 domain according to positions 26-109 and 137-513, respectively, of SEQ ID NO: 39; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-109 and 137-513 of SEQ ID NO: 39, relative to positions 26-109 and 137-513 of SEQ ID NO: 1; - (i) an F2 and an F1 domain according to positions 26-102 and 105-472, respectively, of SEQ ID NO: 31; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-472 of SEQ ID NO: 31, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-102 and 105-472, respectively, of SEQ ID NO: 33; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-472 of SEQ ID NO: 33, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-102 and 105-472, respectively, of SEQ ID NO: 34; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-472 of SEQ ID NO: 34, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-102 and 105-472, respectively, of SEQ ID NO: 40; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally Docket No.: 70348WO01 comprising the substitutions present in positions 26-102 and 105-472 of SEQ ID NO: 40, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-102 and 105-472, respectively, of SEQ ID NO: 42; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-472 of SEQ ID NO: 42, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-103 and 106-474, respectively, of SEQ ID NO: 35; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-474 of SEQ ID NO: 35, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-103 and 106-474, respectively, of SEQ ID NO: 36; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-474 of SEQ ID NO: 36, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); - (i) an F2 and an F1 domain according to positions 26-103 and 106-474, respectively, of SEQ ID NO: 37; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-474 of SEQ ID NO: 37, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); Docket No.: 70348WO01 - (i) an F2 and an F1 domain according to positions 26-103 and 106-474, respectively, of SEQ ID NO: 38; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-474 of SEQ ID NO: 38, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18); or - (i) an F2 and an F1 domain according to positions 26-103 and 106-474, respectively, of SEQ ID NO: 41; or (ii) an F2 domain and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity thereto, and optionally comprising the substitutions present in positions 26-102 and 105-474 of SEQ ID NO: 41, relative to positions 26-102 and 105-472 of SEQ ID NO: 1; wherein according to (i) and (ii) the RSV-F protein optionally comprises a linker sequence joining the F1 and F2 domains which is optionally a GS linker (SEQ ID NO: 18). RSV-F proteins of the present disclosure may comprise or consist of an amino acid sequence having at least 70% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, such as at least 75% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 80% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 85% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 90% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 95% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137- 544 of SEQ ID NO: 2 or 4 respectively, at least 99% sequence identity to positions 26-109 and 137- 544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99.4% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99.5% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 80% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 75% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 80% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 85% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% Docket No.: 70348WO01 of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 90% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137- 544 of SEQ ID NO: 2 or 4 respectively, at least 95% sequence identity to positions 26-109 and 137- 544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99.4% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99.5% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 90% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 75% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 80% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 85% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137- 544 of SEQ ID NO: 2 or 4 respectively, at least 90% sequence identity to positions 26-109 and 137- 544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 95% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, at least 99.4% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively, or at least 99.5% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 over at least 95% of positions 26-109 and 137-544 of SEQ ID NO: 2 or 4 respectively. RSV-F proteins of the present disclosure may have at least 70% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2, such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 2 over 100% of positions 26-109 and 137-544 of SEQ ID NO: 2. RSV-F proteins of the present disclosure may have at least 70% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 4, such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to positions 26-109 and 137-544 of SEQ ID NO: 4 over 100% of positions 26-109 and 137-544 SEQ ID NO: 4. Docket No.: 70348WO01 Preparing RSV-F proteins RSV-F proteins of the present disclosure can be prepared by routine methods, such as by expression in a recombinant host system using a nucleic acid expression vector (e.g. an expression vector as detailed in the section entitled Nucleic acids encoding RSV-F proteins, below). Suitable recombinant host cells include, for example, insect cells (e.g. Sf9 cells, Sf21 cells, Tn5 cells, Schneider S2 cells, and High Five cells); mammalian cells (e.g. Chinese hamster ovary (CHO) cells, human embryonic kidney cells (e.g. HEK293), NIH-3T3 cells, 293-T cells, Vero cells, and HeLa cells); avian cells (e.g. chicken embryonic fibroblasts and chicken embryonic germ cells); bacteria; and yeast cells. HEK293 cells are preferred (as were used in the examples). Accordingly, the present disclosure also provides, in one independent aspect, a host cell (in particular, those detailed above) comprising a nucleic acid (in particular, an expression vector as detailed below) encoding an RSV-F protein of the present disclosure. The present disclosure also provides, in a further independent aspect, a host cell (in particular, those detailed above) comprising and / or expressing an RSV-F protein of the present disclosure. The present disclosure also provides, in a further independent aspect, a composition comprising a host cell (in particular, those detailed above) and (i) a nucleic acid (in particular, an expression vector as detailed below) encoding an RSV-F protein of the present disclosure, and / or (ii) an RSV-F protein of the present disclosure. The present disclosure also provides, in a further independent aspect, an in vitro method for the production of an RSV-F protein of the present disclosure, comprising expressing a nucleic acid (in particular, an expression vector as detailed below) encoding the RSV-F protein in a host cell (in particular, those detailed above), and optionally purifying the RSV- F protein. RSV-F proteins of the present disclosure can be purified, following expression from a host cell, by routine methods, such as precipitation and chromatographic methods (e.g. hydrophobic interaction, ion exchange, affinity, chelating or size exclusion chromatography). The RSV-F proteins of the present disclosure can include a tag that facilitates purification, such as an epitope tag or a histidine (HIS) tag, to facilitate purification e.g. by affinity chromatography. Nucleic acids encoding RSV-F proteins The present disclosure also provides, in a further independent aspect, a nucleic acid encoding an RSV- F protein of the present disclosure. General sequence features of RSV-F proteins in the pre-fusion conformation, when encoded by nucleic acids (e.g. RNA) Nucleic acids of the present disclosure may encode an RSV-F protein of the present disclosure comprising or consisting of an amino acid sequence having at least 70% sequence identity to SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1), such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1). SEQ ID NO: 1 and 3 are full-length wild-type A and B subtype sequences respectively, Docket No.: 70348WO01 which include the signal sequence (positions 1-25 of SEQ ID NO: 1 and 3) and p27 peptide (positions 110-136 of SEQ ID NO: 1 and 3) both of which are typically cleaved out in the mature, furin processed, protein. Nucleic acids of the present disclosure may encode an RSV-F protein of the present disclosure comprising (i) an F2 domain comprising or consisting of an amino acid sequence having at least 70% sequence identity to positions 26-109 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1), such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98% or 99% sequence identity to positions 26-109 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1); and (ii) an F1 domain comprising or consisting of an amino acid sequence having at least 70% sequence identity to positions 137-523 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1), such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99% or 99.5% sequence identity to positions 137-523 of SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1). In some embodiments, nucleic acids of the present disclosure encode an RSV-F protein of the present disclosure comprising an E residue at position 66, and a P residue at position 101 of SEQ ID NO: 1 or 3. In some embodiments, the signal peptide (positions 1-25 of SEQ ID NO: 1 and 3) is not considered in the above sequence identity assessment. Hence, in some embodiments, nucleic acids of the present disclosure encode an RSV-F protein of the present disclosure comprising an amino acid sequence having at least 70% sequence identity to positions 26-574 SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1), such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to positions 26-574 SEQ ID NO: 1 or 3 (in particular to SEQ ID NO: 1). In a preferred embodiment, nucleic acids of the present disclosure encode an RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 47; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 47, which preferably comprises the substitutions 55T, 152R, 211N, 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C and 490C relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3. In a preferred embodiment, nucleic acids of the present disclosure encode an RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 57; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 57, which preferably comprises the substitutions 55T, 152R, 211N, Docket No.: 70348WO01 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C, 490C and Δ555-574 relative to a wild- type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3. In a preferred embodiment, nucleic acids of the present disclosure encode an RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 73; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 73, which preferably comprises the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to a wild-type RSV- F sequence, e.g. according to SEQ ID NO: 1 or 3, and wherein the RSV-F protein preferably comprises a linker sequence joining positions 102 and 105 which is preferably a GS linker (SEQ ID NO: 18). In a preferred embodiment, nucleic acids of the present disclosure encode an RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 87; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 87, which preferably comprises the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C, 490C and Δ555-574 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3, and wherein the RSV-F protein preferably comprises a linker sequence joining positions 102 and 105 which is preferably a GS linker (SEQ ID NO: 18). In a more preferred embodiment, nucleic acids of the present disclosure encode an RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 69; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 69, which preferably comprises the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to a wild-type RSV- F sequence, e.g. according to SEQ ID NO: 1 or 3. In a more preferred embodiment, nucleic acids of the present disclosure encode an RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 83; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 83, which preferably comprises the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C, 490C and Δ555-574 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3. In other embodiments, nucleic acids of the present disclosure encode: - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 110; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, Docket No.: 70348WO01 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 110, which preferably comprises the mutations present in SEQ ID NO: 49 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 112; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 112, which preferably comprises the mutations present in SEQ ID NO: 49 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 49; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 49, which preferably comprises the mutations present in SEQ ID NO: 49 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 51; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 51, which preferably comprises the mutations present in SEQ ID NO: 51 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 53; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 53, which preferably comprises the mutations present in SEQ ID NO: 53 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 55; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 55, which preferably comprises the mutations present in SEQ ID NO: 55 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 71; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, Docket No.: 70348WO01 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 71, which preferably comprises the mutations present in SEQ ID NO: 71 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 75; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 75, which preferably comprises the mutations present in SEQ ID NO: 75 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 77; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 77, which preferably comprises the mutations present in SEQ ID NO: 77 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3; or - An RSV-F protein comprising or consisting of (i) an amino acid sequence according to SEQ ID NO: 79; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 79 which preferably comprises the mutations present in SEQ ID NO: 79 relative to a wild-type RSV-F sequence, e.g. according to SEQ ID NO: 1 or 3. Two furin cleavage sites exist between positions 109 and 137 of SEQ ID NO: 1 and 3 (positions 110- 136 of SEQ ID NO: 1 and 3 defining the “p27” peptide). In some embodiments, nucleic acids of the present disclosure encode an RSV-F protein of the present disclosure in which the p27 peptide is artificially absent (i.e. there is an artificial deletion of the p27 peptide, e.g. through recombinant means, at the level of the encoding nucleic acid). In such embodiments, the fusion peptide (positions 137-157 of SEQ ID NO: 1 and 3) may also be artificially absent. In some embodiments, the p27 peptide (and, optionally, also the fusion peptide) may be replaced by a linker sequence encoded by the nucleic acid. The linker sequence may be glycine-serine rich or consist of G and S residues, for example GSGSG (SEQ ID NO: 16), GSGSGRS (SEQ ID NO: 17), or GS (SEQ ID NO: 18). In one particular embodiment, the F2 and F1 domains may be linked by a linker sequence comprising or consisting of SEQ ID NO: 18. Nucleic acids of the present disclosure may also encode an RSV-F protein of the present disclosure having at least 70% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively; in particular at least 75% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of Docket No.: 70348WO01 SEQ ID NO: 1 or 3 respectively, at least 80% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 85% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 90% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 95% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 99% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 99.4% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 99.5% sequence identity to SEQ ID NO: 1 or 3 over at least 80% of SEQ ID NO: 1 or 3 respectively, at least 75% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 80% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 85% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 90% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 95% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 99% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 99.4% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 99.5% sequence identity to SEQ ID NO: 1 or 3 over at least 90% of SEQ ID NO: 1 or 3 respectively, at least 75% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, at least 80% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, at least 85% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, at least 90% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, at least 95% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, at least 99% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, at least 99.4% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively, or at least 99.5% sequence identity to SEQ ID NO: 1 or 3 over at least 95% of SEQ ID NO: 1 or 3 respectively. Nucleic acids of the present disclosure may encode an RSV-F protein of the present disclosure having at least 70% sequence identity to SEQ ID NO: 1, such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 1 over 100% of SEQ ID NO 1. Nucleic acids of the present disclosure may encode an RSV-F protein of the present disclosure having at least 70% sequence identity to SEQ ID NO: 3, such as at least 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or preferably at least 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% sequence identity to SEQ ID NO: 3 over 100% of SEQ ID NO 3. Nucleic acids of the present disclosure preferably encode an RSV-F protein comprising a transmembrane domain, and, optionally, C-terminal to said transmembrane domain, a cytoplasmic tail. Docket No.: 70348WO01 In some embodiments, a cytoplasmic tail is absent in whole. Preferably, a transmembrane domain comprises or consists of an amino acid sequence according to SEQ ID NO: 21 (or a sequence at least 80%, 85%, 90%, or 95% identical thereto). Preferably, a cytoplasmic tail, if present, comprises or consists of an amino acid sequence according to SEQ ID NO: 5 or 6 (or a sequence at least 80%, 85%, 90%, 95% or 95% identical thereto). Nucleic acids encoding RSV-F proteins comprising cytoplasmic tail deletions The cell-surface expression of trimeric, pre-fusion RSV-F protein, when expressed from nucleic acids in vitro, has been enhanced through the deletion of residues (e.g.20 residues) from the C-terminal end of the cytoplasmic tail (see e.g. Example 4). In addition, surprisingly, deletion of 15, 16, 17 and 20 C- terminal residues resulted in higher trimeric pre-fusion RSV-F expression at 72 and 96 hours post- transfection, compared to the deletion of 21 C-terminal residues (see e.g. Example 9; Figure 28A). Furthermore, in vivo, deletion of 20 C-terminal residues from an RNA-delivered RSV-F protein of the present disclosure enhanced titres of neutralising antibodies elicited against RSV strains of both the A and B subtypes (see, e.g. Example 6; comparing constructs “647” and “647 ΔCT20”; Figures 23A and B). Neutralising antibody titres generally correlate with inhibition of viral replication in the lungs and other respiratory sites, and thus protective efficacy in a subject. Hence, without wishing to be bound by theory, the cytoplasmic tail deletions disclosed herein may allow for protective efficacy against RSV to be achieved at lower doses of a nucleic acid-based vaccine, leading to further possible benefits, e.g. reduced reactogenicity. In embodiments in which RSV-F proteins comprise cytoplasmic tail deletions, an RSV-F protein having a “cytoplasmic tail” refers to the presence of residues (e.g. 5 residues) that are C-terminal to the residue which aligns with position 549 of SEQ ID NO: 1 or 3 (Y), when the F1 and transmembrane domains of the RSV-F protein is aligned with positions 137-549 of SEQ ID NO: 1 or 3. Accordingly, the cytoplasmic tail is positioned C-terminal to the transmembrane domain. Preferably, an RSV-F protein having a “cytoplasmic tail” refers to the presence of residues (e.g. 5 residues) that are C- terminal to position 549 of the RSV-F protein. Reference to e.g. deletion of 2-20 residues (and the like) from the C-terminal end of the CT (relative to SEQ ID NO: 5 or 6) refers to deletion of at least the two, and no more than the 20, most C-terminal residues from the CT. That is, at least the deletion of C- terminal residues SN or SK relative to SEQ ID NO: 5 or 6 respectively, and no more than the deletion of C-terminal residues TPVTLSKDQLSGINNIAFSN or TPVTLSKDQLSGINNIAFSK relative to SEQ ID NO: 5 or 6 respectively. In some embodiments, nucleic acids of the present disclosure encode an RSV-F protein comprising a cytoplasmic tail; wherein, relative to a cytoplasmic tail according to SEQ ID NO: 5 or SEQ ID NO: 6, 2-23 residues are deleted from the C-terminal end of the cytoplasmic tail of the RSV-F protein. In some embodiments, 2-22, 2-21, 2-20 or 3-20 residues are deleted from said C-terminal end. In some embodiments, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or at least 19 residues are deleted from said C-terminal end. In some embodiments, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, Docket No.: 70348WO01 16, 17, 18, 19 or 20 residues are deleted from said C-terminal end. In some embodiments, 2-5, 3-5, 6- 20, 7-20, 8-20, 9-20, 10-20, 11-20, 12-20, 13-20, 14-20, 15-20 or 16-20 residues are deleted from said C-terminal end. In some embodiments, 2-5, such as 2-4, 2-3, 3-4 or 3 residues are deleted from the C-terminal end of the CT of the RSV-F protein (relative to a wild-type cytoplasmic tail according to SEQ ID NO: 5 or 6). In some embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-22 of SEQ ID NO: 5, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii) (meaning, the RSV-F protein sequence ends with the amino acid sequence of (i) or (ii)). In other embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-22 of SEQ ID NO: 6, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). In other embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-20 of SEQ ID NO: 5, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C- terminal to the amino acid sequence of (i) or (ii). In other embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-20 of SEQ ID NO: 6, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). In some embodiments, 6-13, such as 7-13, 8-12, 9-11, 9-10, 10-11 or 10 residues are deleted from the C-terminal end of the CT of the RSV-F protein (relative to a wild-type cytoplasmic tail according SEQ ID NO: 5 or 6). In some embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-15 of SEQ ID NO: 5, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). In other embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-15 of SEQ ID NO: 6, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C- terminal to the amino acid sequence of (i) or (ii). In some embodiments, 14-16, such as 14-15, 15-16 or 15 residues are deleted from the C-terminal end of the CT of the RSV-F protein (relative to a wild-type cytoplasmic tail according SEQ ID NO: 5 or 6). In some embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence Docket No.: 70348WO01 according to positions 1-10 of SEQ ID NO: 5, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). In other embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-10 of SEQ ID NO: 6, or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C- terminal to the amino acid sequence of (i) or (ii). In preferred embodiments, 16-20, such as 17-20, 18-20 or 19-20, and preferably 20, residues are deleted from the C-terminal end of the CT of the RSV-F protein (relative to a wild-type cytoplasmic tail according SEQ ID NO: 5 or 6). See, e.g. effects of such deletions in Examples 4, 6 and 9 (summarised above). In preferred embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-5 of SEQ ID NO: 5, or (ii) an amino acid sequence at least 60% or 80% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). In ither preferred embodiments, the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-5 of SEQ ID NO: 6, or (ii) an amino acid sequence at least 60% or 80% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). Generally, the deletions outlined above increase the cell-surface expression of RSV-F protein from nucleic acids (e.g. RNA), relative to an RSV-F protein having the same amino acid sequence absent deletions, e.g. comprising a wild-type cytoplasmic tail, e.g. according to SEQ ID NO: 5 or 6 (e.g. over at least 24, 48, 72 or 96 hours; or e.g. over 24, 48, 72 or 96 hours). Generally, the deletions outlined above increase the cell-surface expression of RSV-F protein in trimeric, pre-fusion form from nucleic acids (e.g. RNA), relative to expression in such form of an RSV-F protein having the same amino acid sequence absent such deletions, e.g. comprising a wild-type cytoplasmic tail, e.g. according to SEQ ID NO: 5 or 6 (e.g. over at least 24, 48, 72 or 96 hours; or e.g. over 24, 48, 72 or 96 hours). When determining the effect of cytoplasmic tail deletions, trimeric, pre-fusion RSV-F expression is typically assessed using AM14 antibody binding (or defined differently, using binding of an antibody comprising a light chain (LC) according to SEQ ID NO: 7 and a heavy chain (HC) according SEQ ID NO: 8). AM14 antibody binding may be assayed using indirect immunofluorescent labelling, e.g. using the protocol in the examples (see subsection “Indirect immunofluorescent labelling and detection of surface-expressed RSV F”). Cell-surface expression may be assessed in fibroblasts, preferably human fibroblasts, preferably human foreskin fibroblasts, preferably human primary BJ cells, preferably the CRL-2522 cell line (deposited at American Type Culture Collection (ATCC) under said accession number and publicly available). Docket No.: 70348WO01 General features of nucleic acids The nucleic acid of the present disclosure may be DNA or RNA (including hybrids thereof), preferably RNA. DNA and RNA analogues, such as those containing modified backbones (e.g. peptide nucleic acids (PNAs) or phosphorothioates) or modified bases, are within the scope of the present disclosure. The nucleic acid may be linear, circular and / or branched, but will generally be linear. Typically, the nucleic acid will be in recombinant form, i.e. a form which does not occur in nature. The nucleic acid may be for the expression of an RSV-F protein of the present disclosure in vitro from a host cell (i.e. the nucleic acid is, or is part of, an expression vector). Suitable nucleic acid expression vectors (in particular, DNA expression vectors) can comprise, for example, (1) an origin of replication; (2) a selectable marker gene; (3) one or more expression control elements, such as a transcriptional control element (e.g., a promoter, an enhancer, or a terminator), and / or one or more translation signals; and (4) a signal sequence or leader sequence for targeting to the secretory pathway in a selected host cell (e.g. those as detailed in the section entitled Preparing RSV-F proteins, above). In a preferred alternative embodiment, the nucleic acid is for the expression of an RSV-F protein of the present disclosure in vivo in a subject (i.e. the nucleic acid is, or is part of, a nucleic acid-based vaccine). In such preferred embodiments, in addition to a sequence encoding the RSV-F protein of the present disclosure, the nucleic acid may comprise one or more heterologous sequences, such as a sequence encoding a further protein (e.g. as detailed below) and / or a control sequence, in particular a promoter or an internal ribosome entry site. Nucleic acids of the present disclosure may be codon optimised. In some embodiments, nucleic acids of the present disclosure may be codon optimised for expression in human cells. Codon optimisation refers to the use of specific codons, which, while not altering the sequence of the expressed protein (given genetic code redundancy), may increase translation efficacy and / or half- life of the nucleic acid. Embodiments of codon optimised RNA are discussed in more detail in the subsection entitled RNA below. In some embodiments, nucleic acids of the present disclosure are in the form of a viral vector, such as a replicating or replication-deficient viral vector; including both DNA and RNA-based viral vectors. Suitable examples of viral vectors for encoding an RSV-F protein of the present disclosure include, for example: adenovirus vectors, such as replication-deficient or replication-competent adenovirus vectors; pox virus vectors, such as vaccinia virus vectors (e.g. modified vaccinia Ankara virus (MVA), NYVAC, avipox vectors, canarypox (e.g. ALVAC), and fowl pox virus (FPV)); Alphavirus vectors, such as Sindbis virus, Semlike Forest virus (SFV), Ross River virus, Venezuelan equine encephalitis (VEE) virus, and chimeras derived from Alphavirus vectors such as the foregoing; herpes virus vectors, such as cytomegalovirus (CMV)-derived vectors; arena virus vectors, such as lymphocytic choriomeningitis virus (LCMV) vectors; measles virus vectors; vesicular stomatitis virus vectors; pseudorabies virus vectors; adeno-associated virus vectors; retrovirus vectors; lentivirus vectors; and viral-like particles. In other embodiments, the nucleic acid is in the form of a DNA plasmid. In Docket No.: 70348WO01 embodiments wherein the nucleic acid of the present disclosure is a viral vector, preferably the viral vector is an adenovirus vector (e.g. Ad26). The nucleic acid (preferably RNA) may encode an RSV-F protein of the present disclosure only (i.e. the nucleic acid encodes a single protein). Alternatively, the nucleic acid may encode multiple proteins, of which one is the RSV-F protein of the present disclosure. In some embodiments, the nucleic acid encodes at least (i) an RSV-F protein of the present disclosure; and (ii) at least one further protein. The at least one further protein may be a nanoparticle, e.g. a ferritin nanoparticle (e.g. which is encoded, along with the RSV-F protein of the present disclosure, by a single open reading frame, resulting in expression of a single polypeptide). In preferred embodiments, the at least one further protein is an antigen; and, as such, the at least one further protein may comprise, or may be, a viral, bacterial, fungal, parasitic, tumour, or allergenic (i.e. from, or derived from, an allergen) antigen. The at least one further protein will typically be encoded by a separate open reading frame to the RSV-F protein of the invention. The at least one further protein will typically be a pathogen antigen. The at least one further protein will typically be an antigen that is a surface polypeptide e.g. a spike glycoprotein, a haemagglutinin, an adhesin or an envelope glycoprotein. In a particular embodiment, the at least one further protein is an antigen from, or derived from, a virus, in particular a virus causing respiratory disease, in particular a seasonal virus causing respiratory disease. In embodiments wherein the at least one further protein is an antigen from, or derived from, a virus, examples of such viruses include: Coronavirus, Orthomyxovirus, Pneumoviridae, Paramyxoviridae, Poxviridae, Picornavirus, Bunyavirus, Heparnavirus, Filovirus, Togavirus, Flavivirus, Pestivirus, Hepadnavirus, Rhabdovirus, Caliciviridae, Retrovirus, Reovirus, Parvovirus, Herpesvirus, Papovaviruses and Adenovirus. In a preferred embodiment, the at least one further protein detailed above is a further Pneumoviridae protein (in particular a Pneumoviridae antigen). Useful further Pneumoviridae proteins (in particular, antigens) can be from an Orthopneumovirus or Metapneumovirus, in particular human RSV or human Metapneumovirus (hMPV). Useful further hMPV antigens include e.g. the F, N, P, M, M2-1, and M2 antigens (in particular, the F antigen). Such hMPV proteins (in particular, antigens) may be from, or derived from, the A or B subtype. In a preferred embodiment, the nucleic acid is RNA encoding an RSV-F protein of the present disclosure in addition to an hMPV antigen (in particular, the F antigen). In such RNA embodiments, a preferred patient group (in which the RNA may be used in therapy, in particular vaccination) is infants (see section entitled Medical uses and methods of treatment, below). Useful further human RSV antigens include e.g. the G, M1, M2-1, M2-2, P, L, N, NS1, NS2 and SH antigens, in addition to further RSV-F antigens, i.e. of distinct amino acid sequence to the RSV-F protein of the present disclosure encoded by the nucleic acid. Such further human RSV proteins (in particular, antigens; in particular F, antigens) may be from, or derived from, the A or B subtype. In a particular embodiment, the nucleic acid is a viral vector (in particular, a poxvirus vector, in particular an MVA vector) encoding an RSV-F protein of the present disclosure in addition to a plurality of further RSV proteins (in particular, antigens); in particular at least 2, 3, or 4 further RSV proteins / Docket No.: 70348WO01 antigens; in particular selected from G (from or derived from the A subtype: “GA”), G (from or derived from the B subtype: “GB”) N and either M2-1 or M2-2; in particular GA, GB, N and either of M2-1 or M2-2. In such viral vector embodiments, a particular patient group (in which the viral vector may be used in therapy, in particular vaccination) is older adults (see section entitled Medical uses and methods of treatment, below). In some embodiments, the at least one further protein detailed above is a Coronavirus antigen. Useful Coronavirus antigens can be from a SARS coronavirus, in particular SARS-CoV2. Useful Coronavirus antigens (preferably SARS-CoV2 antigens) include the spike, M, E, HE, Nuclocapsid, Plpro and 3CLPro proteins, in particular spike protein. Preferably, the Coronavirus antigen is a SARS- CoV2 spike protein. Said SARS-CoV2 spike protein may be from any variant, e.g. Omicron (such as Omicron BA.1, BA.2, BA3, BA.4 or BA.5), Alpha, Epsilon, Eta, Theta, Kappa, Iota, Zeta, Mu, Lambda, Beta, Gamma, or Delta. Preferably, said SARS-CoV2 spike protein includes one or more mutations relative to the wild-type protein, in particular one or more (e.g. two) mutations to proline resides. Said one or more mutations may be introduced to stabilise said SARS-CoV2 spike protein in its pre-fusion conformation. In a preferred embodiment, the nucleic acid is RNA encoding an RSV-F protein of the present disclosure in addition to a Coronavirus antigen, e.g. as detailed above. In such RNA embodiments, a preferred patient group (in which the RNA may be used in therapy, in particular vaccination) is older adults (see section entitled Medical uses and methods of treatment, below). In some embodiments, the at least one further protein detailed above is an Orthomyxovirus antigen. Useful Orthomyxovirus antigens can be from an influenza A, B or C virus. Useful Orthomyxovirus antigens (in particular influenza A, B or C virus antigens) include the haemagglutinin, neuraminidase and matrix M2 proteins, in particular haemagglutinin. Preferably, the Orthomyxovirus antigen is an influenza A virus haemagglutinin. Said influenza A virus hemagglutinin may be from any subtype e.g. H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15 or H16. In a preferred embodiment, the nucleic acid is RNA encoding an RSV-F protein of the present disclosure in addition to an Orthomyxovirus antigen, e.g. as detailed above. In such RNA embodiments, a preferred patient group (in which the RNA may be used in therapy, in particular vaccination) is older adults (see section entitled Medical uses and methods of treatment, below). In such RNA embodiments, the RNA may encode (i) an RSV-F protein of the present disclosure, (ii) a Coronavirus antigen, e.g. as detailed above, and (iii) an Orthomyxovirus antigen, e.g. as detailed above. A plurality of nucleic acids of the present disclosure is, in particular, provided in purified or substantially purified form; that is, substantially free from other nucleic acids (e.g. free or substantially free from naturally-occurring nucleic acids, such as further nucleic acids expressed by a host cell). Said plurality of nucleic acids is generally at least 50% pure (by weight), such as at least 60%, 70%, 80%, 90%, or 95% pure (by weight). Docket No.: 70348WO01 The present disclosure also provides, in a further independent aspect, a vector comprising one or more nucleic acids of the present disclosure. Nucleic acids encoding an RSV-F protein of the present disclosure may be delivered naked, or preferably in conjunction with a carrier (e.g. as detailed in the section entitled Carriers comprising a nucleic acid encoding an RSV-F protein in the prefusion conformation, below). Generally, nucleic acids (preferably RNA) of the present disclosure, and the RSV-F proteins encoded thereby, elicit a pre-fusion RSV-F-specific antibody response in vivo, e.g. an IgG antibody response (see, e.g. Examples 6, 11 and 14). Generally, nucleic acids (preferably RNA) of the present disclosure, and the RSV-F proteins encoded thereby, elicit a neutralising antibody response against RSV (RSV A or B) in vivo, e.g. against RSV A (see, e.g. Examples 6, 11, 14, 15 and 16). Said neutralising antibody response may inhibit replication of RSV (RSV A or B) in the respiratory system of a subject (such as in the lungs). Said neutralising antibody response may yield protective immunity against RSV (such as RSV A or B) in a subject, e.g. against RSV A. Generally, nucleic acids (preferably RNA) of the present disclosure, and the RSV-F proteins encoded thereby, elicit a cross-neutralising antibody response against RSV in vivo, e.g. against strains of both RSV A and B subtypes (see, e.g. Examples 6, 15 and 16). Said cross-neutralising antibody response may yield protective immunity against strains of both RSV A and B subtypes in a subject. RNA In a preferred embodiment, the nucleic acid of the present disclosure (encoding an RSV-F protein of the present disclosure) is RNA. In the context of this section entitled RNA, “RNA” refers to an artificial (or, defined differently, recombinant) ribonucleic acid encoding an RSV-F protein of the present disclosure, which may be translated in a cell (i.e. mRNA). Preferably, the RNA is neither, nor comprised within, a viral vector or virus-based vaccine (such as a live-attenuated virus vaccine). RNA molecules can have various lengths but are typically 500-20,000 ribonucleotides long e.g.1000- 20,000, 1000-15,000, 1000-10,000, 1000-5000, 1000-3000, 1000-2500, 1000-2500 or 1000-2000 ribonucleotides long. The RNA can be non-self-replicating (also referred to as “conventional” RNA), or self-replicating; preferably non-self-replicating. In some embodiments, the RNA is self-replicating. Self-replicating RNA can be produced using replication elements derived from, e.g., alphaviruses, and substituting sequences encoding the structural viral proteins with that encoding at least an RSV-F protein of the present disclosure. A self- replicating RNA molecule is typically a positive-strand molecule which can be directly translated after delivery to a cell, and this translation provides an RNA-dependent RNA polymerase which then produces both antisense and sense transcripts from the delivered RNA. Thus, the delivered RNA leads Docket No.: 70348WO01 to the production of multiple daughter RNAs. These daughter RNAs, as well as collinear subgenomic transcripts, may be translated themselves to provide in situ expression of the encoded protein (i.e. the RSV-F protein of the present disclosure); or may be transcribed to provide further transcripts with the same sense as the delivered RNA, which are translated to provide in situ expression of the encoded protein. The overall result of this sequence of transcriptions is substantial amplification in the number of the introduced RNAs, and so the encoded RSV-F protein of the present disclosure (potentially in addition to further proteins as detailed above) becomes a major polypeptide product of the cells. In such embodiments wherein the RNA is self-replicating, it may encode (i) an RNA-dependent RNA polymerase which can transcribe RNA from the self-replicating RNA and (ii) an RSV-F protein of the present disclosure. The polymerase can be an alphavirus replicase e.g. comprising one or more of alphavirus proteins nsP1, nsP2, nsP3 and nsP4. Such alphavirus-based self-replicating RNA can use a replicase from, for example, a Sindbis virus, a Semliki forest virus, an eastern equine encephalitis virus (EEEV), or a Venezuelan equine encephalitis virus (VEEV). Mutant or wild-type virus sequences can be used e.g. the attenuated TC83 mutant of VEEV has been used for self-replicating RNA (see

[0018] ). Thus, a self-replicating RNA encoding an RSV-F protein of the present disclosure may have two open reading frames. The first (5') open reading frame encodes a replicase, in particular an alphavirus replicase (e.g. as detailed above); the second (3') open reading frame encodes the RSV-F protein of the present disclosure. Further open reading frames may also be present, encoding (i) one or more further proteins (preferably one or more further antigens, e.g. as detailed above); and / or (ii) accessory polypeptides. Generally, the RNA comprises a 5’ cap, such as a 7-methylguanosine (m7G / m7G), which may be added via enzymatic means or a non-enzymatic reaction. The RNA may have the following exemplary 5’ caps: - a 7-methylguanosine linked 5’-to-5’ to the 5’ first ribonucleotide by a triphosphate bridge (also referred to as “Cap O”); - a 7-methylguanosine linked 5’-to-5’ to the 5’ first ribonucleotide by a triphosphate bridge, and wherein the first 5’ ribonucleotide comprises a 2’-methylated ribose (2’-O-Me) (also referred to as “Cap 1”); - a 7-methylguanosine linked 5’-to-5’ to the 5’ first ribonucleotides by a triphosphate bridge, and wherein the first and second 5’ ribonucleotides comprise a 2’-methylated ribose (2’-O-Me) (also referred to as “Cap 2”); - or a 7-methylguanosine linked 5’-to-5’ to the 5’ first ribonucleotides by a triphosphate bridge, and wherein the first, second and third 5’ ribonucleotides comprise a 2’-methylated ribose (2’- O-Me). In a preferred embodiment, the 5’ cap is a 7-methylguanosine linked 5’-to-5’ to the 5’ first ribonucleoside by a triphosphate bridge, and wherein the first 5’ ribonucleoside comprises a 2’- Docket No.: 70348WO01 methylated ribose (2’-O-Me), e.g. the 5’ end of the RNA has the structure m7G(5')ppp(5')(2'OMeA)pG. Preferably, this cap is added non-enzymatically through the use of the following reagent: Said reagent is sold as CLEANCAP Reagent AG (TRILINK BIOTECHNOLOGIES). In other embodiments, a cap may be added resulting in the 5’ end of the RNA having the structure m7(3'OMeG)(5')ppp(5')(2'OMeA)pG. This cap may be added non-enzymatically through the use of the following reagent: Said reagent is sold as CLEANCAP Reagent AG (3’OMe) (TRILINK BIOTECHNOLOGIES) Generally, the RNA comprises a 3’ poly-adenosine (“poly-A”) tail, e.g. comprising 10-700 A ribonucleotides. The poly-A tail may comprise at least two non-contiguous stretches of A Docket No.: 70348WO01 ribonucleotides (also referred to as a “split poly-A tail”), or a (in particular, only one) contiguous stretch of A ribonucleotides. The total number of A ribonucleotides (“As”) in at least two non- contiguous stretches may be, for example, 10-700, such as 10-600, 10-500, 20-500, 50-500, 70-500, 100-500, 20-400, 30-300, 40-200, 50-150, 70-120, 100-120, or, in particular, 100-120. The total number of As in a (in particular, only one) contiguous stretch may be, for example, 10-700; such as 10-600, 20-600 or in particular 40-600 (such as 50-600, 80-600, 80-550, 100-500; or 40-70, 50-65 or 55-65). Wherein at least two non-contiguous stretches of As are used, these may be of differing length. For example, a first stretch may be 10-150 As in length, such as 10-100, 10-50, 15-50, 20-50, 20-40, 25-40, or, in particular 25-35 As in length. For example, a second stretch may be 10-150 As in length, such as 10-150, 20-120, 30-100, 40-90, 50-90, 60-90, 65-90, 70-90, or, in particular, 80-90 As in length. The first stretch may be located 5’ or 3’ relative to the second stretch. However, in a particular embodiment, the first stretch is located 5’ relative to the second stretch. In a further particular embodiment, the polyA tail comprises, in the 5’ to 3’ direction, a first and a second non-contiguous stretch of As, that are 25-35 and 80-90 As in length respectively. In a further particular embodiment, the polyA tail comprises, in the 5’-3’ direction, a first and a second non-contiguous stretch of As, that are 25-35 and 65-90 As in length respectively. In a preferred embodiment, the polyA tail comprises, in the 5’-3’ direction, a first and a second non-contiguous stretch of As, that are 25-35 (e.g.28-32, 29- 31, about 30 or 30) and 25-45 (e.g. 25-40, 30-40, 35-40, 35-39, 36-38, about 37 or 37) As in length respectively. In some embodiments, the at least two non-contiguous stretches of As is from, or is part of, the 3’ untranslated region (UTR), e.g. as detailed below. The RNA preferably comprises (in addition to any 5' cap structure) one or more modified ribonucleotides, i.e. ribonucleotides that are modified in structure relative to standard A, C, G or U ribonucleotides. In other embodiments, the RNA does not comprise modified ribonucleotides, i.e. the RNA contains standard A, C, G or U ribonucleotides only (except for any 5’ cap structure, if present, e.g. as detailed above). In preferred embodiments wherein one or more modified ribonucleotides are used, said one or more modified ribonucleotides may be, or may comprise, N1-methylpseudouridine (“1mΨ”); pseudouridine (“Ψ”); N1-ethylpseudouridine; 2-methylthio-N6-(cis- hydroxyisopentenyl)adenosine; 2-methylthio-N6-methyladenosine; 2-methylthio-N6-threonyl carbamoyladenosine; N6-glycinylcarbamoyladenosine; N6-isopentenyladenosine; N6- methyladenosine (m6A); N6-threonylcarbamoyladenosine; 1,2'-O-dimethyladenosine; 1- methyladenosine; 2'-O-methyladenosine; 2'-O-ribosyladenosine (phosphate); 2-methyladenosine; 2- methylthio-N6 isopentenyladenosine; 2-methylthio-N6-hydroxynorvalyl carbamoyladenosine; 2'-O- methyladenosine; 2'-O-ribosyladenosine (phosphate); Isopentenyladenosine; N6-(cis- hydroxyisopentenyl)adenosine; N6,2'-O-dimethyladenosine; N6,2'-O-dimethyladenosine; N6,N6,2'- O-trimethyladenosine; N6,N6-dimethyladenosine; N6-acetyladenosine; N6- hydroxynorvalylcarbamoyladenosine; N6-methyl-N6-threonylcarbamoyladenosine; 2- methyladenosine; 2-methylthio-N6-isopentenyladenosine; 7-deaza-adenosine; N1-methyl-adenosine; N6,N6 (dimethyl)adenine; N6-cis-hydroxy-isopentenyl-adenosine; .alpha.-thio-adenosine; 2 Docket No.: 70348WO01 (amino)adenine; 2 (aminopropyl)adenine; 2 (methylthio) N6 (isopentenyl)adenine; 2-(alkyl)adenine; 2-(aminoalkyl)adenine; 2-(aminopropyl)adenine; 2-(halo)adenine; 2-(halo)adenine; 2- (propyl)adenine; 2'-Amino-2'-deoxy-ATP; 2'-Azido-2'-deoxy-ATP; 2'-Deoxy-2'-a-aminoadenosine TP; 2'-Deoxy-2'-a-azidoadenosine TP; 6 (alkyl)adenine; 6 (methyl)adenine; 6-(alkyl)adenine; 6- (methyl)adenine; 7 (deaza)adenine; 8 (alkenyl)adenine; 8 (alkynyl)adenine; 8 (amino)adenine; 8 (thioalkyl)adenine; 8-(alkenyl)adenine; 8-(alkyl)adenine; 8-(alkynyl)adenine; 8-(amino)adenine; 8- (halo)adenine; 8-(hydroxyl)adenine; 8-(thioalkyl)adenine; 8-(thiol)adenine; 8-azido-adenosine; aza adenine; deaza adenine; N6 (methyl)adenine; N6-(isopentyl)adenine; 7-deaza-8-aza-adenosine; 7- methyladenine; 1-Deazaadenosine TP; 2'Fluoro-N6-Bz-deoxyadenosine TP; 2'-OMe-2-Amino-ATP; 2'O-methyl-N6-Bz-deoxyadenosine TP; 2'-a-Ethynyladenosine TP; 2-aminoadenine; 2- Aminoadenosine TP; 2-Amino-ATP; 2'-a-Trifluoromethyladenosine TP; 2-Azidoadenosine TP; 2'-b- Ethynyladenosine TP; 2-Bromoadenosine TP; 2'-b-Trifluoromethyladenosine TP; 2-Chloroadenosine TP; 2'-Deoxy-2',2'-difluoroadenosine TP; 2'-Deoxy-2'-a-mercaptoadenosine TP; 2'-Deoxy-2'-a- thiomethoxyadenosine TP; 2'-Deoxy-2'-b-aminoadenosine TP; 2'-Deoxy-2'-b-azidoadenosine TP; 2'- Deoxy-2'-b-bromoadenosine TP; 2'-Deoxy-2'-b-chloroadenosine TP; 2'-Deoxy-2'-b-fluoroadenosine TP; 2'-Deoxy-2'-b-iodoadenosine TP; 2'-Deoxy-2'-b-mercaptoadenosine TP; 2'-Deoxy-2'-b- thiomethoxyadenosine TP; 2-Fluoroadenosine TP; 2-Iodoadenosine TP; 2-Mercaptoadenosine TP; 2- methoxy-adenine; 2-methylthio-adenine; 2-Trifluoromethyladenosine TP; 3-Deaza-3- bromoadenosine TP; 3-Deaza-3-chloroadenosine TP; 3-Deaza-3-fluoroadenosine TP; 3-Deaza-3- iodoadenosine TP; 3-Deazaadenosine TP; 4'-Azidoadenosine TP; 4'-Carbocyclic adenosine TP; 4'- Ethynyladenosine TP; 5'-Homo-adenosine TP; 8-Aza-ATP; 8-bromo-adenosine TP; 8- Trifluoromethyladenosine TP; 9-Deazaadenosine TP; 2-aminopurine; 7-deaza-2,6-diaminopurine; 7- deaza-8-aza-2,6-diaminopurine; 7-deaza-8-aza-2-aminopurine; 2,6-diaminopurine; 7-deaza-8-aza- adenine, 7-deaza-2-aminopurine; 2-thiocytidine; 3-methylcytidine; 5-formylcytidine; 5- hydroxymethylcytidine; 5-methylcytidine; N4-acetylcytidine; 2'-O-methylcytidine; 2'-O- methylcytidine; 5,2'-O-dimethylcytidine; 5-formyl-2'-O-methylcytidine; Lysidine; N4,2'-O- dimethylcytidine; N4-acetyl-2'-O-methylcytidine; N4-methylcytidine; N4,N4-Dimethyl-2'-OMe- Cytidine TP; 4-methylcytidine; 5-aza-cytidine; Pseudo-iso-cytidine; pyrrolo-cytidine; .alpha.-thio- cytidine; 2-(thio)cytosine; 2'-Amino-2'-deoxy-CTP; 2'-Azido-2'-deoxy-CTP; 2'-Deoxy-2'-a- aminocytidine TP; 2'-Deoxy-2'-a-azidocytidine TP; 3 (deaza) 5 (aza)cytosine; 3 (methyl)cytosine; 3- (alkyl)cytosine; 3-(deaza) 5 (aza)cytosine; 3-(methyl)cytidine; 4,2'-O-dimethylcytidine; 5 (halo)cytosine; 5 (methyl)cytosine; 5 (propynyl)cytosine; 5 (trifluoromethyl)cytosine; 5- (alkyl)cytosine; 5-(alkynyl)cytosine; 5-(halo)cytosine; 5-(propynyl)cytosine; 5- (trifluoromethyl)cytosine: 5-bromo-cytidine; 5-iodo-cytidine; 5-propynyl cytosine; 6-(azo)cytosine; 6- aza-cytidine; aza cytosine; deaza cytosine; N4 (acetyl)cytosine; 1-methyl-1-deaza-pseudoisocytidine; 1-methyl-pseudoisocytidine; 2-methoxy-5-methyl-cytidine: 2-methoxy-cytidine; 2-thio-5-methyl- cytidine; 4-methoxy-1-methyl-pseudoisocytidine; 4-methoxy-pseudoisocytidine; 4-thio-1-methyl-1- deaza-pseudoisocytidine; 4-thio-1-methyl-pseudoisocytidine; 4-thio-pseudoisocytidine; 5-aza- Docket No.: 70348WO01 zebularine; 5-methyl-zebularine; pyrrolo-pseudoisocytidine; Zebularine; (E)-5-(2-Bromo- vinyl)cytidine TP; 2,2'-anhydro-cytidine TP hydrochloride; 2'Fluor-N4-Bz-cytidine TP; 2'Fluoro-N4- Acetyl-cytidine TP; 2'-O-Methyl-N4-Acetyl-cytidine TP; 2'O-methyl-N4-Bz-cytidine TP; 2'-a- Ethynylcytidine TP; 2'-a-Trifluoromethylcytidine TP; 2'-b-Ethynylcytidine TP; 2'-b- Trifluoromethylcytidine TP; 2'-Deoxy-2',2'-difluorocytidine TP; 2'-Deoxy-2'-a-mercaptocytidine TP; 2'-Deoxy-2'-a-thiomethoxycytidine TP; 2'-Deoxy-2'-b-aminocytidine TP; 2'-Deoxy-2'-b-azidocytidine TP; 2'-Deoxy-2'-b-bromocytidine TP; 2'-Deoxy-2'-b-chlorocytidine TP; 2'-Deoxy-2'-b-fluorocytidine TP; 2'-Deoxy-2'-b-iodocytidine TP; 2'-Deoxy-2'-b-mercaptocytidine TP; 2'-Deoxy-2'-b- thiomethoxycytidine TP; 2'-O-Methyl-5-(1-propynyl)cytidine TP; 3'-Ethynylcytidine TP; 4'- Azidocytidine TP; 4'-Carbocyclic cytidine TP; 4'-Ethynylcytidine TP; 5-(1-Propynyl)ara-cytidine TP; 5-(2-Chloro-phenyl)-2-thiocytidine TP; 5-(4-Amino-phenyl)-2-thiocytidine TP; 5-Aminoallyl-CTP; 5-Cyanocytidine TP; 5-Ethynylara-cytidine TP; 5-Ethynylcytidine TP; 5'-Homo-cytidine TP; 5- Methoxycytidine TP; 5-Trifluoromethyl-Cytidine TP; N4-Amino-cytidine TP; N4-Benzoyl-cytidine TP; Pseudoisocytidine; 7-methylguanosine; N2,2'-O-dimethylguanosine; N2-methylguanosine; Wyosine; 1,2'-O-dimethylguanosine; 1-methylguanosine; 2'-O-methylguanosine; 2'-O- ribosylguanosine (phosphate); 2'-O-methylguanosine; 2'-O-ribosylguanosine (phosphate); 7- aminomethyl-7-deazaguanosine; 7-cyano-7-deazaguanosine; Archaeosine; Methylwyosine; N2,7- dimethylguanosine; N2,N2,2'-O-trimethylguanosine; N2,N2,7-trimethylguanosine; N2,N2- dimethylguanosine; N2,7,2'-O-trimethylguanosine; 6-thio-guanosine; 7-deaza-guanosine; 8-oxo- guanosine; N1-methyl-guanosine; .alpha.-thio-guanosine; 2 (propyl)guanine; 2-(alkyl)guanine; 2'- Amino-2'-deoxy-GTP; 2'-Azido-2'-deoxy-GTP; 2'-Deoxy-2'-a-aminoguanosine TP; 2'-Deoxy-2'-a- azidoguanosine TP; 6 (methyl)guanine; 6-(alkyl)guanine; 6-(methyl)guanine; 6-methyl-guanosine; 7 (alkyl)guanine; 7 (deaza)guanine; 7 (methyl)guanine; 7-(alkyl)guanine; 7-(deaza)guanine; 7- (methyl)guanine; 8 (alkyl)guanine; 8 (alkynyl)guanine; 8 (halo)guanine; 8 (thioalkyl)guanine; 8- (alkenyl)guanine; 8-(alkyl)guanine; 8-(alkynyl)guanine; 8-(amino)guanine; 8-(halo)guanine; 8- (hydroxyl)guanine; 8-(thioalkyl)guanine; 8-(thiol)guanine; aza guanine; deaza guanine; N (methyl)guanine; N-(methyl)guanine; 1-methyl-6-thio-guanosine; 6-methoxy-guanosine; 6-thio-7- deaza-8-aza-guanosine; 6-thio-7-deaza-guanosine; 6-thio-7-methyl-guanosine; 7-deaza-8-aza- guanosine; 7-methyl-8-oxo-guanosine; N2,N2-dimethyl-6-thio-guanosine; N2-methyl-6-thio- guanosine; 1-Me-GTP; 2'Fluoro-N2-isobutyl-guanosine TP; 2'O-methyl-N2-isobutyl-guanosine TP; 2'-a-Ethynylguanosine TP; 2'-a-Trifluoromethylguanosine TP; 2'-b-Ethynylguanosine TP; 2'-b- Trifluoromethylguanosine TP; 2'-Deoxy-2',2'-difluoroguanosine TP; 2'-Deoxy-2'-a- mercaptoguanosine TP; 2'-Deoxy-2'-a-thiomethoxyguanosine TP; 2'-Deoxy-2'-b-aminoguanosine TP; 2'-Deoxy-2'-b-azidoguanosine TP; 2'-Deoxy-2'-b-bromoguanosine TP; 2'-Deoxy-2'-b- chloroguanosine TP; 2'-Deoxy-2'-b-fluoroguanosine TP; 2'-Deoxy-2'-b-iodoguanosine TP; 2'-Deoxy- 2'-b-mercaptoguanosine TP; 2'-Deoxy-2'-b-thiomethoxyguanosine TP; 4'-Azidoguanosine TP; 4'- Carbocyclic guanosine TP; 4'-Ethynylguanosine TP; 5'-Homo-guanosine TP; 8-bromo-guanosine TP; 9-Deazaguanosine TP; N2-isobutyl-guanosine TP; 1-methylinosine; Inosine; 1,2'-O-dimethylinosine; Docket No.: 70348WO01 2'-O-methylinosine; 7-methylinosine; 2'-O-methylinosine; Epoxyqueuosine; galactosyl-queuosine; Mannosylqueuosine; Queuosine; allyamino-thymidine; aza thymidine; deaza thymidine; deoxy- thymidine; 2'-O-methyluridine; 2-thiouridine; 3-methyluridine; 5-carboxymethyluridine; 5- hydroxyuridine; 5-methyluridine; 5-taurinomethyl-2-thiouridine; 5-taurinomethyluridine; Dihydrouridine; (3-(3-amino-3-carboxypropyl)uridine; 1-methyl-3-(3-amino-5- carboxypropyl)pseudouridine; 1-methylpseduouridine; 1-methyl-pseudouridine; 2'-O-methyluridine; 2'-O-methylpseudouridine; 2'-O-methyluridine; 2-thio-2'-O-methyluridine; 3-(3-amino-3- carboxypropyl)uridine; 3,2'-O-dimethyluridine; 3-Methyl-pseudo-Uridine TP; 4-thiouridine; 5- (carboxyhydroxymethyl)uridine; 5-(carboxyhydroxymethyl)uridine methyl ester, 5,2'-O- dimethyluridine; 5,6-dihydro-uridine; 5-aminomethyl-2-thiouridine; 5-carbamoylmethyl-2'-O- methyluridine; 5-carbamoylmethyluridine; 5-carboxyhydroxymethyluridine; 5- carboxyhydroxymethyluridine methyl ester, 5-carboxymethylaminomethyl-2'-O-methyluridine; 5- carboxymethylaminomethyl-2-thiouridine; 5-carboxymethylaminomethyl-2-thiouridine; 5- caboxymethylaminomethyluridine; 5-carboxymethylaminomethyluridine; 5-Carbamoylmethyluridine TP; 5-methoxycaeoonylmethyl-2'-O-methyluridine; 5-methoxycarbonylmethyl-2-thiouridine; 5- methoxycarbonylmethyluridine; 5-methoxyuridine; 5-methyl-2-thiouridine; 5-methylaminomethyl-2- selenouridine; 5-methylaminomethyl-2-thiouridine; 5-methylaminomethyluridine; 5- Methyldihydrouridine; 5-Oxyacetic acid-Uridine TP; 5-Oxyacetic acid-methyl ester-Uridine TP; N1- methyl-pseudo-uridine; N1-ethyl-pseudo-uridine; uridine 5-oxyacetic acid; uridine 5-oxyacetic acid methyl ester; 3-(3-Amino-3-carboxypropyl)-Uridine TP; 5-(iso-Pentenylaminomethyl)-2-thiouridine TP; 5-(iso-Pentenylaminomethyl)-2'-O-methyluridine TP; 5-(iso-Pentenylaminomethyl)uridine TP; 5- propynyl uracil; .alpha.-thio-uridine; 1 (aminoalkylamino-carbonylethylenyl)-2(thio)-pseudouridine; 1 (aminoalkylaminocarbonylethylenyl)-2,4-(dithio)pseudouridine; 1 (aminoalkylaminocarbonylethylenyl)-4 (thio)pseudouridine; 1 (aminoalkylaminocarbonylethylenyl)- pseudouridine; 1 (aminocazbonylethylenyl)-2(thio)-pseudouridine; 1 (aminocarbonylethylenyl)-2,4- (dithio)pseudouridine; 1 (aminocarbonylethylenyl)-4 (thio)pseudouridine; 1 (aminocarbonylethylenyl)-pseudouridine; 1 substituted 2(thio)-pseudouridine; 1 substituted 2,4- (dithio)pseudouridine; 1 substituted 4 (thio)pseudouridine; 1 substituted pseudouridine; 1- (aminoalkylamino-carbonylethylenyl)-2-(thio)-pseudouridine; 1-Methyl-3-(3-amino-3- carboxypropyl) pseudouridine TP; 1-Methyl-3-(3-amino-3-carboxypropyl)pseudo-UTP; 1-Methyl- pseudo-UTP; 2 (thio)pseudouridine; 2' deoxy uridine; 2' fluorouridine; 2-(thio)uracil; 2,4- (dithio)psuedouracil; 2' methyl, 2'amino, 2'azido, 2'fluoro-guanosine; 2'-Amino-2'-deoxy-UTP; 2'- Azido-2'-deoxy-UTP; 2'-Azido-deoxyuridine TP; 2'-O-methylpseudouridine; 2' deoxy uridine; 2' fluorouridine; 2'-Deoxy-2'-a-aminouridine TP; 2'-Deoxy-2'-a-azidouridine TP; 2- methylpseudouridine; 3 (3 amino-3 carboxypropyl)uracil; 4 (thio)pseudouridine; 4- (thio)pseudouridine; 4-(thio)uracil; 4-thiouracil; 5 (1,3-diazole-1-alkyl)uracil; 5 (2- aminopropyl)uracil; 5 (aminoalkyl)uracil; 5 (dimethylaminoalkyl)uracil; 5 (guanidiniumalkyl)uracil; 5 (methoxycarbonylmethyl)-2-(thio)uracil; 5 (methoxycarbonyl-methyl)uracil; 5 (methyl) 2 Docket No.: 70348WO01 (thio)uracil; 5 (methyl) 2,4 (dithio)uracil; 5 (methyl) 4 (thio)uracil; 5 (methylaminomethyl)-2 (thio)uracil; 5 (methylaminomethyl)-2,4 (dithio)uracil; 5 (methylaminomethyl)-4 (thio)uracil; 5 (propynyl)uracil; 5 (trifluoromethyl)uracil; 5-(2-aminopropyl)uracil; 5-(alkyl)-2-(thio)pseudouridine; 5-(alkyl)-2,4 (dithio)pseudouridine; 5-(alkyl)-4 (thio)pseudouridine; 5-(alkyl)pseudouridine; 5- (alkyl)uracil; 5-(alkynyl)uracil; 5-(allylamino)uracil; 5-(cyanoalkyl)uracil; 5- (dialkylaminoalkyl)uracil; 5-(dimethylaminoalkyl)uracil; 5-(guanidiniumalkyl)uracil; 5-(halo)uracil; 5-(1,3-diazole-1-alkyl)uracil; 5-(methoxy)uracil; 5-(methoxycarbonylmethyl)-2-(thio)uracil; 5- (methoxycarbonyl-methyl)uracil; 5-(methyl) 2(thio)uracil; 5-(methyl) 2,4 (dithio)uracil; 5-(methyl) 4 (thio)uracil; 5-(methyl)-2-(thio)pseudouridine; 5-(methyl)-2,4 (dithio)pseudouridine; 5-(methyl)-4 (thio)pseudouridine; 5-(methyl)pseudouridine; 5-(methylaminomethyl)-2 (thio)uracil; 5- (methylaminomethyl)-2,4(dithio)uracil; 5-(methylaminomethyl)-4-(thio)uracil; 5-(propynyl)uracil; 5- (trifluoromethyl)uracil; 5-aminoallyl-uridine; 5-bromo-uridine; 5-iodo-uridine; 5-uracil; 6 (azo)uracil; 6-(azo)uracil; 6-aza-uridine; allyamino-uracil; aza uracil; deaza uracil; N3 (methyl)uracil; Pseudo- UTP-1-2-ethanoic acid; Pseudouridine; 4-Thio-pseudo-UTP; 1-carboxymethyl-pseudouridine; 1- methyl-1-deaza-pseudouridine; 1-propynyl-uridine; 1-taurinomethyl-1-methyl-uridine; 1- taurinomethyl-4-thio-uridine; 1-taurinomethyl-pseudouridine; 2-methoxy-4-thio-pseudouridine; 2- thio-1-methyl-1-deaza-pseudouridine; 2-thio-1-methyl-pseudouridine; 2-thio-5-aza-uridine; 2-thio- dihydropseudouridine; 2-thio-dihydrouridine; 2-thio-pseudouridine; 4-methoxy-2-thio-pseudouridine; 4-methoxy-pseudouridine; 4-thio-1-methyl-pseudouridine; 4-thio-pseudouridine; 5-aza-uridine; Dihydropseudouridine; (.+-.)1-(2-Hydroxypropyl)pseudouridine TP; (2R)-1-(2- Hydroxypropyl)pseudouridine TP; (2S)-1-(2-Hydroxypropyl)pseudouridine TP; (E)-5-(2-Bromo- vinyl)ara-uridine TP; (E)-5-(2-Bromo-vinyl)uridine TP; (Z)-5-(2-Bromo-vinyl)ara-uridine TP; (Z)-5- (2-Bromo-vinyl)uridine TP; 1-(2,2,2-Trifluoroethyl)-pseudo-UTP; 1-(2,2,3,3,3- Pentafluoropropyl)pseudouridine TP; 1-(2,2-Diethoxyethyl)pseudouridine TP; 1-(2,4,6- Trimethylbenzyl)pseudouridine TP; 1-(2,4,6-Trimethyl-benzyl)pseudo-UTP; 1-(2,4,6-Trimethyl- phenyl)pseudo-UTP; 1-(2-Amino-2-carboxyethyl)pseudo-UTP; 1-(2-Amino-ethyl)pseudo-UTP; 1-(2- Hydroxyethyl)pseudouridine TP; 1-(2-Methoxyethyl)pseudouridine TP; 1-(3,4-Bis- trifluoromethoxybenzyl)pseudouridine TP; 1-(3,4-Dimethoxybenzyl)pseudouridine TP; 1-(3-Amino- 3-carboxypropyl)pseudo-UTP; 1-(3-Amino-propyl)pseudo-UTP; 1-(3-Cyclopropyl-prop-2- ynyl)pseudouridine TP; 1-(4-Amino-4-carboxybutyl)pseudo-UTP; 1-(4-Amino-benzyl)pseudo-UTP; 1-(4-Amino-butyl)pseudo-UTP; 1-(4-Amino-phenyl)pseudo-UTP; 1-(4-Azidobenzyl)pseudouridine TP; 1-(4-Bromobenzyl)pseudouridine TP; 1-(4-Chlorobenzyl)pseudouridine TP; 1-(4- Fluorobenzyl)pseudouridine TP; 1-(4-Iodobenzyl)pseudouridine TP; 1-(4- Methanesulfonylbenzyl)pseudouridine TP; 1-(4-Methoxybenzyl)pseudouridine TP; 1-(4-Methoxy- benzyl)pseudo-UTP; 1-(4-Methoxy-phenyl)pseudo-UTP; 1-(4-Methylbenzyl)pseudouridine TP; 1-(4- Methyl-benzyl)pseudo-UTP; 1-(4-Nitrobenzyl)pseudouridine TP; 1-(4-Nitro-benzyl)pseudo-UTP; 1- (4-Nitro-phenyl)pseudo-UTP; 1-(4-Thiomethoxybenzyl)pseudouridine TP; 1-(4- Trifluoromethoxybenzyl)pseudouridine TP; 1-(4-Trifluoromethylbenzyl)pseudouridine TP; 1-(5- Docket No.: 70348WO01 Amino-pentyl)pseudo-UTP; 1-(6-Amino-hexyl)pseudo-UTP; 1,6-Dimethyl-pseudo-UTP; 1-[3-(2-{2- [2-(2-Aminoethoxy)-ethoxy]-ethoxy}-ethoxy)-propionyl]pseudouri- dine TP; 1-{3-[2-(2- Aminoethoxy)-ethoxy]-propionyl} pseudouridine TP; 1-Acetylpseudouridine TP; I-Alkyl-6-(1- propynyl)-pseudo-UTP; 1-Alkyl-6-(2-propynyl)-pseudo-UTP; 1-Alkyl-6-allyl-pseudo-UTP; 1-Alkyl- 6-ethynyl-pseudo-UTP; 1-Alkyl-6-homoallyl-pseudo-UTP; 1-Alkyl-6-vinyl-pseudo-UTP; 1- Allylpseudouridine TP; 1-Aminomethyl-pseudo-UTP; 1-Benzoylpseudouridine TP; 1- Benzyloxymethylpseudouridine TP; 1-Benzyl-pseudo-UTP; 1-Biotinyl-PEG2-pseudouridine TP; 1- Biotinylpseudouridine TP; 1-Butyl-pseudo-UTP; 1-Cyanomethylpseudouridine TP; 1- Cyclobutylmethyl-pseudo-UTP; 1-Cyclobutyl-pseudo-UTP; 1-Cycloheptylmethyl-pseudo-UTP; 1- Cycloheptyl-pseudo-UTP; 1-Cyclohexylmethyl-pseudo-UTP; 1-Cyclohexyl-pseudo-UTP; 1- Cyclooctylmethyl-pseudo-UTP; 1-Cyclooctyl-pseudo-UTP; 1-Cyclopentylmethyl-pseudo-UTP; 1- Cyclopentyl-pseudo-UTP; 1-Cyclopropylmethyl-pseudo-UTP; 1-Cyclopropyl-pseudo-UTP; 1-Ethyl- pseudo-UTP; 1-Hexyl-pseudo-UTP; 1-Homoallylpseudouridine TP; 1-Hydroxymethylpseudouridine TP; 1-iso-propyl-pseudo-UTP; 1-Me-2-thio-pseudo-UTP; 1-Me-4-thio-pseudo-UTP; 1-Me-alpha- thio-pseudo-UTP; 1-Methanesulfonylmethylpseudouridine TP; 1-Methoxymethylpseudouridine TP; 1-Methyl-6-(2,2,2-Trifluoroethyl)pseudo-UTP; 1-Methyl-6-(4-morpholino)-pseudo-UTP; 1-Methyl- 6-(4-thiomorpholino)-pseudo-UTP; 1-Methyl-6-(substituted phenyl)pseudo-UTP; 1-Methyl-6-amino- pseudo-UTP; 1-Methyl-6-azido-pseudo-UTP; 1-Methyl-6-bromo-pseudo-UTP; 1-Methyl-6-butyl- pseudo-UTP; 1-Methyl-6-chloro-pseudo-UTP; 1-Methyl-6-cyano-pseudo-UTP; 1-Methyl-6- dimethylamino-pseudo-UTP; 1-Methyl-6-ethoxy-pseudo-UTP; 1-Methyl-6-ethylcarboxylate-pseudo- UTP; 1-Methyl-6-ethyl-pseudo-UTP; 1-Methyl-6-fluoro-pseudo-UTP; 1-Methyl-6-formyl-pseudo- UTP; 1-Methyl-6-hydroxyamino-pseudo-UTP; 1-Methyl-6-hydroxy-pseudo-UTP; 1-Methyl-6-iodo- pseudo-UTP; 1-Methyl-6-iso-propyl-pseudo-UTP; 1-Methyl-6-methoxy-pseudo-UTP; 1-Methyl-6- methylamino-pseudo-UTP; 1-Methyl-6-phenyl-pseudo-UTP; 1-Methyl-6-propyl-pseudo-UTP; 1- Methyl-6-tert-butyl-pseudo-UTP; 1-Methyl-6-trifluoromethoxy-pseudo-UTP; 1-Methyl-6- trifluoromethyl-pseudo-UTP; 1-Morpholinomethylpseudouridine TP; 1-Pentyl-pseudo-UTP; 1- Phenyl-pseudo-UTP; 1-Pivaloylpseudouridine TP; 1-Propargylpseudouridine TP; 1-Propyl-pseudo- UTP; 1-propynyl-pseudouridine; 1-p-tolyl-pseudo-UTP; 1-tert-Butyl-pseudo-UTP; 1- Thiomethoxymethylpseudouridine TP; 1-Thiomorpholinomethylpseudouridine TP; 1- Trifluoroacetylpseudouridine TP; 1-Trifluoromethyl-pseudo-UTP; 1-Vinylpseudouridine TP; 2,2'- anhydro-uridine TP; 2'-bromo-deoxyuridine TP; 2'-F-5-Methyl-2'-deoxy-UTP; 2'-OMe-5-Me-UTP; 2'-OMe-pseudo-UTP; 2'-a-Ethynyluridine TP; 2'-a-Trifluoromethyluridine TP; 2'-b-Ethynyluridine TP; 2'-b-Trifluoromethyluridine TP; 2'-Deoxy-2',2'-difluorouridine TP; 2'-Deoxy-2'-a- mercaptouridine TP; 2'-Deoxy-2'-a-thiomethoxyuridine TP; 2'-Deoxy-2'-b-aminouridine TP; 2'- Deoxy-2'-b-azidouridine TP; 2'-Deoxy-2'-b-bromouridine TP; 2'-Deoxy-2'-b-chlorouridine TP; 2'- Deoxy-2'-b-fluorouridine TP; 2'-Deoxy-2'-b-iodouridine TP; 2'-Deoxy-2'-b-mercaptouridine TP; 2'- Deoxy-2'-b-thiomethoxyuridine TP; 2-methoxy-4-thio-uridine; 2-methoxyuridine; 2'-O-Methyl-5-(1- propynyl)uridine TP; 3-Alkyl-pseudo-UTP; 4'-Azidouridine TP; 4'-Carbocyclic uridine TP; 4'- Docket No.: 70348WO01 Ethynyluridine TP; 5-(1-Propynyl)ara-uridine TP; 5-(2-Furanyl)uridine TP; 5-Cyanouridine TP; 5- Dimethylaminouridine TP; 5'-Homo-uridine TP; 5-iodo-2'-fluoro-deoxyuridine TP; 5- Phenylethynyluridine TP; 5-Trideuteromethyl-6-deuterouridine TP; 5-Trifluoromethyl-Uridine TP; 5- Vinylarauridine TP; 6-(2,2,2-Trifluoroethyl)-pseudo-UTP; 6-(4-Morpholino)-pseudo-UTP; 6-(4- Thiomorpholino)-pseudo-UTP; 6-(Substituted-Phenyl)-pseudo-UTP; 6-Amino-pseudo-UTP; 6- Azido-pseudo-UTP; 6-Bromo-pseudo-UTP; 6-Butyl-pseudo-UTP; 6-Chloro-pseudo-UTP; 6-Cyano- pseudo-UTP; 6-Dimethylamino-pseudo-UTP; 6-Ethoxy-pseudo-UTP; 6-Ethylcarboxylate-pseudo- UTP; 6-Ethyl-pseudo-UTP; 6-Fluoro-pseudo-UTP; 6-Formyl-pseudo-UTP; 6-Hydroxyamino-pseudo- UTP; 6-Hydroxy-pseudo-UTP; 6-Iodo-pseudo-UTP; 6-iso-Propyl-pseudo-UTP; 6-Methoxy-pseudo- UTP; 6-Methylamino-pseudo-UTP; 6-Methyl-pseudo-UTP; 6-Phenyl-pseudo-UTP; 6-Phenyl-pseudo- UTP; 6-Propyl-pseudo-UTP; 6-tert-Butyl-pseudo-UTP; 6-Trifluoromethoxy-pseudo-UTP; 6- Trifluoromethyl-pseudo-UTP; Alpha-thio-pseudo-UTP; Pseudouridine 1-(4-methylbenzenesulfonic acid) TP; Pseudouridine 1-(4-methylbenzoic acid) TP; Pseudouridine TP 1-[3-(2-ethoxy)]propionic acid; Pseudouridine TP 1-[3-{2-(2-[2-(2-ethoxy)-ethoxy]-ethoxy)-ethoxy}]propionic acid; Pseudouridine TP 1-[3-{2-(2-[2-{2-(2-ethoxy)-ethoxy)-ethoxy}-ethoxy]-ethoxy}]propionic acid; Pseudouridine TP 1-[3-{2-(2-[2-ethoxy]-ethoxy)-ethoxy}]propionic acid; Pseudouridine TP 1-[3-{2- (2-ethoxy)-ethoxy}]propionic acid; Pseudouridine TP 1-methylphosphonic acid; Pseudouridine TP 1- methylphosphonic acid diethyl ester; Pseudo-UTP-N1-3-propionic acid; Pseudo-UTP-N1-4-butanoic acid; Pseudo-UTP-N1-5-pentanoic acid; Pseudo-UTP-N1-6-hexanoic acid; Pseudo-UTP-N1-7- heptanoic acid; Pseudo-UTP-N1-methyl-p-benzoic acid; Pseudo-UTP-N1-p-benzoic acid; Wybutosine; Hydroxywybutosine; Isowyosine; Peroxywybutosine; undermodified hydroxywybutosine; 4-demethylwyosine; 2,6-(diamino)purine; 1-(aza)-2-(thio)-3-(aza)-phenoxazin- 1-yl: 1,3-(diaza)-2-(oxo)-phenthiazin-1-yl; 1,3-(diaza)-2-(oxo)-phenoxazin-1-yl; 1,3,5-(triaza)-2,6- (dioxa)-naphthalene; 2 (amino)purine; 2,4,5-(trimethyl)phenyl; 2' methyl, 2'amino, 2'azido, 2'fluoro- cytidine; 2' methyl, 2'amino, 2'azido, 2'fluoro-adenine; 2'methyl, 2'amino, 2'azido, 2'fluoro-uridine; 2'- amino-2'-deoxyribose; 2-amino-6-Chloro-purine; 2-aza-inosinyl; 2'-azido-2'-deoxyribose; 2'fluoro-2'- deoxyribose; 2'-fluoro-modified bases; 2'-O-methyl-ribose; 2-oxo-7-aminopyridopyrimidin-3-yl; 2- oxo-pyridopyrimidine-3-yl; 2-pyridinone; 3 nitropyrrole; 3-(methyl)-7-(propynyl)isocarbostyrilyl; 3- (methyl)isocarbostyrilyl; 4-(fluoro)-6-(methyl)benzimidazole; 4-(methyl)benzimidazole; 4- (methyl)indolyl; 4,6-(dimethyl)indolyl; 5 nitroindole; 5 substituted pyrimidines; 5- (methyl)isocarbostyrilyl; 5-nitroindole; 6-(aza)pyrimidine; 6-(azo)thymine; 6-(methyl)-7- (aza)indolyl; 6-chloro-purine; 6-phenyl-pyrrolo-pyrimidin-2-on-3-yl; 7-(aminoalkylhydroxy)-1-(aza)- 2-(thio)-3-(aza)-phenthiazin-1-yl; 7-(aminoalkylhydroxy)-1-(aza)-2-(thio)-3-(aza)-phenoxazin-1-yl; 7-(aminoalkylhydroxy)-1,3-(diaza)-2-(oxo)-phenoxazin-1-yl; 7-(aminoalkylhydroxy)-1,3-(diaza)-2- (oxo)-phenthiazin-1-yl; 7-(aminoalkylhydroxy)-1,3-(diaza)-2-(oxo)-phenoxazin-1-yl; 7-(aza)indolyl; 7-(guanidiniumalkylhydroxy)-1-(aza)-2-(thio)-3-(aza)-phenoxazinl-yl; 7-(guanidiniumalkylhydroxy)- 1-(aza)-2-(thio)-3-(aza)-phenthiazin-1-yl; 7-(guanidiniumalkylhydroxy)-1-(aza)-2-(thio)-3-(aza)- phenoxazin-1-yl; 7-(guanidiniumalkylhydroxy)-1,3-(diaza)-2-(oxo)-phenoxazin-1-yl; 7- Docket No.: 70348WO01 (guanidiniumalkyl-hydroxy)-1,3-(diaza)-2-(oxo)-phenthiazin-1-yl; 7-(guanidiniumalkylhydroxy)-1,3- (diaza)-2-(oxo)-phenoxazin-1-yl; 7-(propynyl)isocarbostyrilyl; 7-(propynyl)isocarbostyrilyl, propynyl-7-(aza)indolyl; 7-deaza-inosinyl; 7-substituted 1-(aza)-2-(thio)-3-(aza)-phenoxazin-1-yl; 7- substituted 1,3-(diaza)-2-(oxo)-phenoxazin-1-yl; 9-(methyl)-imidizopyridinyl; Aminoindolyl; Anthracenyl; bis-ortho-(aminoalkylhydroxy)-6-phenyl-pyrrolo-pyrimidin-2-on-3-yl; bis-ortho- substituted-6-phenyl-pyrrolo-pyrimidin-2-on-3-yl; Difluorotolyl; Hypoxanthine; Imidizopyridinyl; Inosinyl; Isocarbostyrilyl; Isoguanisine; N2-substituted purines; N6-methyl-2-amino-purine; N6- substituted purines; N-alkylated derivative; Napthalenyl; Nitrobenzimidazolyl; Nitroimidazolyl; Nitroindazolyl; Nitropyrazolyl; Nubularine; O6-substituted purines; O-alkylated derivative; ortho- (aminoalkylhydroxy)-6-phenyl-pyrrolo-pyrimidin-2-on-3-yl; ortho-substituted-6-phenyl-pyrrolo- pyrimidin-2-on-3-yl; Oxoformycin TP; para-(aminoalkylhydroxy)-6-phenyl-pyrrolo-pyrimidin-2-on- 3-yl; para-substituted-6-phenyl-pyrrolo-pyrimidin-2-on-3-yl; Pentacenyl; Phenanthracenyl; Phenyl; propynyl-7-(aza)indolyl; Pyrenyl; pyridopyrimidin-3-yl; pyridopyrimidin-3-yl, 2-oxo-7-amino- pyridopyrimidin-3-yl; pyrrolo-pyrimidin-2-on-3-yl; Pyrrolopyrimidinyl; Pyrrolopyrizinyl; Stilbenzyl; substituted 1,2,4-triazoles; Tetracenyl; Tubercidine; Xanthine; Xanthosine-5'-TP; 2-thio-zebularine; 5- aza-2-thio-zebularine; 7-deaza-2-amino-purine; pyridin-4-one ribonucleoside; 2-Amino-riboside-TP; Formycin A TP; Formycin B TP; Pyrrolosine TP; 2'-OH-ara-adenosine TP; 2'-OH-ara-cytidine TP; 2'- OH-ara-uridine TP; 2'-OH-ara-guanosine TP; 5-(2-carbomethoxyvinyl)uridine TP; or N6-(19-Amino- pentaoxanonadecyl)adenosine TP. In some embodiments, the percentage of standard As substituted with A-substitutable modified nucleotide (e.g. those above) is at least: 0.1%, 0.5%, 0.8%, 1%, 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, or at least 99.9%, or 100%. In some embodiments, the percentage of standard As substituted with m6A may be 0.1-5%, in particular 0.5- 2%, in particular 0.8-1.2%, such as about 1% (or 1%); in these embodiments the RNA may be circular RNA. Low substitution levels with m6A (e.g.1%) have been shown in inhibit innate immune activation

[0019] . In some embodiments, the percentage of standard Cs substituted with cytosine-substitutable modified nucleotide (e.g. those above) is at least: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, or at least 99.9%, or 100%. In some embodiments, the percentage of standard Gs substituted with G-substitutable modified nucleotide (e.g. those above) is at least: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, or at least 99.9%, or 100%. In preferred embodiments, the percentage of standard Us substituted with U-substitutable modified nucleotide (e.g. those above) is at least: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, or at least 99.9%, or preferably 100%; more preferably with 1mΨ and / or Ψ (even more preferably 1mΨ) . In a preferred embodiment, the one or more modified ribonucleotides detailed above is, or comprise, 1mΨ and / or Ψ, more preferably 1mΨ. In such embodiments, the RNA may comprise 1mΨ and / or Ψ, and neither standard U ribonucleotides nor other modified U ribonucleotides (i.e. there are no standard Docket No.: 70348WO01 U nucleotides, nor modified U ribonucleotides other than 1mΨ and / or Ψ, in the RNA; i.e. 100% U substitution). In particular, the RNA may comprise 1mΨ and / or Ψ, and neither standard U ribonucleotides nor other modified ribonucleotides (i.e. there are no standard U nucleotides, nor modified ribonucleotides of any type - A, C, G or U substitutable - other than 1mΨ and / or Ψ, in the RNA; i.e. 100% U substitution with no other modified nucleotides being allowed). The RNA may comprise Ψ, and neither standard U ribonucleotides nor other modified U ribonucleotides (i.e. 100% U substitution with Ψ). In particular, the RNA may comprise Ψ, and neither standard U ribonucleotides nor other modified ribonucleotides (i.e. 100% U substitution with Ψ with no other modified nucleotides being allowed). More preferably, the RNA comprises 1mΨ, and neither standard U ribonucleotides nor other modified U ribonucleotides (i.e.100% U substitution with 1mΨ). In an even more preferred embodiment, the RNA comprises 1mΨ, and neither standard U ribonucleotides nor other modified ribonucleotides (i.e.100% U substitution with 1mΨ with no other modified nucleotides being allowed). In the embodiments in this paragraph, “[may] comprise[s]... and neither [X]...nor [Y]” may be used interchangeably with the wording “[may] comprise[s]... and does not comprise... [X] and / or [Y] ”. Preferably, the RNA is codon-optimised. An example of a codon-optimised sequence is SEQ ID NO: 104 (codon-optimised version of SEQ ID NO: 83). Codon optimisation may provide an elevated GC content, relative to non-codon optimised RNA encoding the same protein(s). The GC content (the percentage of all ribonucleotides (or, defined alternatively, all “nitrogenous bases”) in the RNA which are G or C) of the RNA may be at least 10%, such as at least 20%, 30%, 35% or at least 40%, preferably at least 45%, 46%, 47%, 48%, 49%, or at least 50%. The GC content of the RNA may be 10-70%, such as 20-65%, 30-65% or 35-65%, preferably 40-60%, 45-55%, 46-53%, 47-51%, or 48-50%. The GC content of the RNA may be 30-70%, such as 40-70%, 45-70%, 50-70%, or 55-70%. Codon optimisation may provide an elevated C content relative to non-codon optimised RNA encoding the same protein(s). The percentage of C-optimisable codons in the RNA which have been substituted, as a result of codon optimisation, for a codon with greater C content (while encoding the same amino acid) may be least 30%, such as at least 40%, 50%, 55% or at least 60%, preferably at least 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72% or at least 72%; The percentage of C-optimisable codons in the RNA which have been substituted, as a result of codon optimisation, for a codon with greater C content (while encoding the same amino acid) may be 30-80%, such as 40-90%, 45-90%, 50-80%, 55-80% or 60-80%, preferably 65-75%, 66-75%, 67-75%, 68-75%, 69-75%, 70-74%, 71-74% or 72-74%. Generally, the RNA comprises a 5’ and / or a 3’ untranslated region (UTR), preferably both a 5’ and 3’ UTR; e.g. selected from the 5’and 3’ UTRs of RNA transcripts of the following genes (preferably the following human genes): beta-actin, albumin, ATP synthase beta subunit, fibroblast activation protein (“FAP”), H4 clustered histone 15 (“HIST2H4A”), glyceraldehyde-3-phosphate dehydrogenase, heat shock protein family A (Hsp70) member 8 gene,, interleukin-2 gene (“IL-2”), and transferrin. In some preferred embodiments, the RNA comprises a 5’ and a 3’ UTR selected from: Docket No.: 70348WO01 - SEQ ID NO: 94 and 95, respectively, - SEQ ID NO: 96 and 97, respectively, - SEQ ID NO: 98 and 99, respectively, - SEQ ID NO: 100 and 101, respectively, - SEQ ID NO: 102 and 103, respectively, and - 5’ and 3’ UTRs having at least 70%, 80%, 85%, 90%, 95%, 96%, 98%, 99% or 99.5% identity to SEQ ID NO: 94 and 95, SEQ ID NO: 96 and 97, SEQ ID NO: 98 and 99, SEQ ID NO: 100 and 101, and SEQ ID NO: 102 and 103, respectively); with RNA sequences according to SEQ ID NO: 94 and 95, SEQ ID NO: 96 and 97, SEQ ID NO: 98 and 99 (and RNA sequences having such identity thereto, preferably at least 95% or greater) being preferred; and RNA sequences according to SEQ ID NO: 94 and 95 (and RNA sequences having such identity thereto, preferably at least 95% or greater) being more preferred. Both the 3’ and 5’ UTR may influence expression of the RSV-F protein of the present disclosure through a variety of mechanisms. Without wishing to be found by this theory, the 5’ UTR may affect the expression of at least the RSV-F protein of the present disclosure e.g. via pre-initiation complex regulation, closed-loop regulation, upstream open reading frame regulations (i.e. reinitiation), provision of internal ribosome entry sites, and provision of microRNA binding sites. Without wishing to be found by this theory, the 3’ UTR may affect the expression of at least the RSV-F protein of the present disclosure e.g. via providing regulation regions that post-transcriptionally influence expression; e.g. influencing translation efficiency, localisation of the RNA, stability of the RNA, polyadenylation, and circularization of the RNA. In one specific embodiment, the RNA is circular RNA. In a preferred embodiment, the RNA fulfils any 2, 3, 4 or 5 of the following criteria (for example, (a) (b), (d) and (f); (a), (b), (c), (d) and (f); or (a), (b), (d), (e) and (f): (a) is non-self-replicating; (b) is single stranded; (c) comprises a 5’ cap, which is a 7-methylguanosine linked 5’-to-5’ to the 5’ first ribonucleotide by a triphosphate bridge, and wherein the first 5’ ribonucleotide comprises a 2’-methylated ribose (2’-O-Me); (d) comprises a 3’poly-A tail; (e) comprises 1mΨ, and neither standard U ribonucleotides nor other modified ribonucleotides Docket No.: 70348WO01 (f) comprises a 5’ and a 3’ UTR. More preferably, the RNA fulfils all of criteria (a) – (f), above. Generally, the RNA will comprise, in the 5’ to 3’ direction: 5’ Cap, 5’ UTR, open reading frame encoding at least an RSV-F protein of the present disclosure, 3’UTR, and 3’ poly-A tail (in particular, the 5’ Caps; 5’ UTRs, 3’UTRs and 3’ poly-A tails as detailed above throughout this subsection). In preferred embodiments, the RNA comprises or consists of the sequence: SEQ ID NO: 82; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; SEQ ID NO: 104; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; SEQ ID NO: 128; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; SEQ ID NO: 68; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3; SEQ ID NO: 56; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure Docket No.: 70348WO01 comprising the substitutions 55T, 152R, 211N, 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; or SEQ ID NO: 46; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 211N, 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C, 490C relative to (and numbered according to) SEQ ID NO: 1 or 3. SEQ ID NO: 86; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C, 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising a linker sequence joining the F1 and F2 domains of the RSV-F protein which is preferably a GS linker (SEQ ID NO: 18), preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; or SEQ ID NO: 72; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C, 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising a linker sequence joining the F1 and F2 domains of the RSV-F protein which is preferably a GS linker (SEQ ID NO: 18); wherein, of the above embodiments, the following is more preferred: SEQ ID NO: 104; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical thereto, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3. In other embodiments, the RNA comprises or consists of any of SEQ ID NOs: 48, 50, 52, 54, 58, 60, 62, 64, 70, 74, 76, 78, 80, 84, 88, 90 or 92; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to any of said SEQ ID NOs, optionally encoding an RSV-F protein of the present Docket No.: 70348WO01 disclosure comprising the mutations relative to (and numbered according to) SEQ ID NO: 1 present in the protein encoded by any of said SEQ ID NOs respectively. See Table 1 in the Examples for mutations (substitutions, and deletions where present) in the proteins encoded by said sequences. The present disclosure also provides, in a further independent aspect, a DNA construct (preferably a DNA plasmid) encoding an RNA sequence comprising or consisting of: any of SEQ ID NOs: 48, 50, 52, 54, 56, 58, 60, 62, 64, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92 or 104; or any of the foregoing sequences having identity to said SEQ ID NOs. In preferred embodiments, the RNA comprises an open reading frame (ORF) comprising or consisting of the sequence of: positions 32-1693 of SEQ ID NO: 82; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; positions 32-1693 of SEQ ID NO: 104; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; positions 32-1693 of SEQ ID NO: 128; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; positions 32-1753 of SEQ ID NO: 68; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3; Docket No.: 70348WO01 positions 32-1693 of SEQ ID NO: 56; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 211N, 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; or positions 32-1753 of SEQ ID NO: 46; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 211N, 215A, 228K, 315I, 346Q, 348N, 445D, 455V, 459M, 486C, 490C relative to (and numbered according to) SEQ ID NO: 1 or 3. positions 32-1693 of SEQ ID NO: 86; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C, 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising a linker sequence joining the F1 and F2 domains of the RSV-F protein which is preferably a GS linker (SEQ ID NO: 18), preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3; or positions 32-1753 of SEQ ID NO: 72; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C, 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising a linker sequence joining the F1 and F2 domains of the RSV-F protein which is preferably a GS linker (SEQ ID NO: 18); wherein, of the above embodiments, the following is more preferred: positions 32-1693 of SEQ ID NO: 104; or an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to said positions, preferably encoding an RSV-F protein of the present disclosure comprising the substitutions 55T, 152R, 215A, 228K, 315I, 346Q, 445D, 455V, 459M, 486C and 490C relative to (and numbered according to) SEQ ID NO: 1 or 3, preferably further comprising the deletion Δ555-574 relative to (and numbered according to) SEQ ID NO: 1 or 3. Docket No.: 70348WO01 In other embodiments, the RNA comprises an ORF comprising or consisting of the ORF from any of SEQ ID NOs: 48, 50, 52, 54, 58, 60, 62, 64, 70, 74, 76, 78, 80, 84, 88, 90 or 92; or an ORF at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to the ORF from any of said SEQ ID NOs, optionally encoding an RSV-F protein of the present disclosure comprising the mutations relative to (and numbered according to) SEQ ID NO: 1 present in the protein encoded by the ORF from any of said SEQ ID NOs respectively. See Table 1 in the Examples for mutations (substitutions and deletions where present) in the proteins encoded by said sequences The present disclosure also provides, in a further independent aspect, a DNA construct (preferably a DNA plasmid) encoding an RNA sequence comprising an ORF comprising or consisting of the sequence of: the ORF from any of SEQ ID NOs: 48, 50, 52, 54, 56, 58, 60, 62, 64, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92 or 104; or any of the foregoing ORFs having identity to the ORFs from said SEQ ID NOs. Nucleic acid (e.g. RNA) alignments may be performed, for example, visually, or by any well-known algorithm; e.g. using an NCBI BLAST algorithm such as “megablast”, e.g. on default settings (available at e.g. https: / / blast.ncbi.nlm.nih.gov / Blast.cgi?PROGRAM=blastn&BLAST_SPEC=GeoBlast&PAGE_TY PE=BlastSearch); or e.g. using the “Muscle” algorithm (see, e.g.

[0020] ,

[0021] ), e.g. on default settings; with the Muscle algorithm being preferred. Corresponding nucleotide or ribonucleotide positions are easily identifiable to the skilled person, and can be identified by aligning the nucleotide or ribonucleotide sequences using any well-known method (such as visual or algorithm, e.g. as detailed above). The RNA can conveniently be prepared by in vitro transcription (IVT). IVT can use a (DNA) template created and propagated in plasmid form in bacteria, or created synthetically (for example by gene synthesis and / or polymerase chain-reaction (PCR) engineering methods). For instance, a DNA- dependent RNA polymerase (such as the bacteriophage T7, T3 or SP6 RNA polymerases) can be used to transcribe the replicating RNA from a DNA template. Appropriate capping and poly-A addition reactions can be used as required (although the poly-A tail is usually encoded within the DNA template). Carriers comprising a nucleic acid encoding an RSV-F protein in the prefusion conformation Nucleic acid (especially RNA) by themselves and unprotected, may be degraded by the subject’s nucleases and may require a carrier to facilitate target cell entry. Accordingly, the present disclosure also provides a carrier comprising a nucleic acid (preferably RNA) encoding an RSV-F protein of the present disclosure. The carrier may be lipid-based (e.g. a lipid nanoparticle or cationic nanoemulsion), polymer-based (e.g. comprising polyamines, dendrimers and / or copolymers), peptide or protein-based (e.g. comprising protamine, a cationic cell-penetrating peptide, and / or an anionic peptide conjugated Docket No.: 70348WO01 to a positively charged polymer), cell-based (e.g. antigen presenting cells, such as dendritic cells loaded with the nucleic acid), or virus-based (e.g. viral replicon particles). In particular embodiments, the carrier is non-virion, i.e. free or substantially free of viral capsid. In particular, lipid-based carriers provide a means to protect the nucleic acid (preferably RNA), e.g. through encapsulation, and deliver it to target cells for protein expression. In some embodiments, the lipid-based carrier is, or comprises, a cationic nano-emulsion (“CNE”). CNEs and methods for their preparation are described in, for example,

[0022] . With a CNE, the nucleic acid (preferably RNA) which encodes the RSV-F protein of the present disclosure is complexed with a CNE particle, in particular comprising an oil core and a cationic lipid. The cationic lipid can interact with the negatively charged molecule, thereby anchoring the molecule to the emulsion particles. In a particular embodiment, a lipid-based carrier is a lipid inorganic nanoparticle (“LION”). LNPs In a preferred embodiment, nucleic acids (preferably RNA) are encapsulated in a lipid nanoparticle (LNP). Thus, in a preferred embodiment, the present disclosure also provides an LNP encapsulating a nucleic acid (preferably RNA) which encodes an RSV-F protein of the present disclosure. A plurality of such LNPs will be part of a composition (e.g. a pharmaceutical composition as detailed in the section entitled Pharmaceutical compositions below) comprising free and / or encapsulated nucleic acid (preferably RNA), and in some embodiments the LNPs encapsulate at least: 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97.0%, 97.1%, 97.2%, 97.3%, 97.4%, 97.5%, 97.6%, 97.7%, 97.8%, 97.9%, 98.0%, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7%, 98.8%, 98.9%, 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or at least 100% of the total number of nucleic acid (preferably RNA) molecules in the composition. At least 80% of the LNPs in the composition may be 20-200 nm, 40-190 nm, 60-180 nm or, in particular, 80-160 nm in diameter. In a particular embodiment, substantially all, or all, LNPs in the composition are 20-200 nm, 40-190 nm, 60-180 nm or, in particular, 80-160 nm in diameter. The LNP can comprise multilamellar vesicles (MLV), small uniflagellar vesicles (SUV), or large unilamellar vesicles (LUV). The amount of nucleic acid (preferably RNA) per LNP can vary, and the number of individual nucleic acid molecules per LNP can depend on the characteristics of the particle being used. For RNA molecules, in general, an LNP may include 1-500 RNA molecules, e.g. <200, <100, <50, <20, <10, <5, or 1-4. Generally, an LNP includes fewer than 10 different species of RNA e.g. fewer than 5, 4, 3, or 2 different species. Preferably the LNP includes a single RNA species (i.e. all RNA molecules in the particle have the same sequence). LNPs according to the present disclosure may be formed from a single lipid (e.g. a cationic lipid) or, in particular, from a mixture of lipids. In particular, the mixture comprises various classes of lipids, such as: Docket No.: 70348WO01 (a) a mixture of cationic lipids and sterols, (b) a mixture of cationic lipids and neutral lipids, (c) a mixture of cationic lipids and polymer-conjugated lipids, (d) a mixture of cationic lipids, sterols and polymer-conjugated lipids, or (e) a mixture of cationic lipids, neutral lipids and polymer-conjugated lipids; or preferably: (f) a mixture of cationic lipids, sterols and neutral lipids; or more preferably: (g) a mixture of cationic lipids, neutral lipids, sterols and polymer-conjugated lipids. Further classes of lipids, such as anionic lipids, may also be present in a mixture of lipids. The cationic lipid may have a pKa of 5.0-10.0, 5.0-9.0, 5.0-8.5, preferably 5.0-8.0, 5.0-7.9, or 5.0-7.8, 5.0-7.7, or more preferably 5.0-7.6. The pKa of the cationic lipid is distinct to the pKa of the LNP as a whole (sometimes called “apparent pKa”). pKa may be determined via any well-known method, such as via a toluene nitrosulphonic acid (TNS) fluorescence assay or acid base titration; preferably a TNS fluorescence assay; more preferably performed according to Example 10. The cationic lipid preferably comprises a tertiary or quaternary amine group, more preferably a tertiary amine group. Exemplary cationic lipids comprising tertiary amine groups include: 1,2-dilinoleyoxy- 3-(dimethylamino)acetoxypropane (DLin-DAC), 1,2-dilinoleyoxy-3morpholinopropane (DLin-MA), 1,2-dilinoleoyl-3-dimethylaminopropane (DLinDAP), 1,2-dilinoleylthio-3-dimethylaminopropane (DLin-S-DMA), 1-linoleoyl-2-linoleyloxy-3dimethylaminopropane (DLin-2-DMAP), 1,2- dilinoleyloxy-3-trimethylaminopropane chloride salt (DLin-TMA.Cl), 1,2-dilinoleoyl-3- trimethylaminopropane chloride salt (DLin-TAP.Cl), 1,2-dilinoleyloxy-3-(N- methylpiperazino)propane (DLin-MPZ), 3-(N,Ndilinoleylamino)-1,2-propanediol (DLinAP), 3-(N,N- dioleylamino)-1,2-propanediol (DOAP), 1,2-dilinoleyloxo-3-(2-N,N-dimethylamino)ethoxypropane (DLin-EG-DMA), and 2,2-dilinoleyl-4-dimethylaminomethyl[1,3]-dioxolane (DLin-K-DMA), 2,2- dilinoleyl-4-(2-dimethylaminoethyl)[1,3]-dioxolane (DLin-KC2-DMA); dilinoleyl-methyl-4- dimethylaminobutyrate (DLin-MC3-DMA); or MC3 (see, e.g.

[0023] ). In some embodiments, the cationic lipid has the structure of lipid RV28, RV31, RV33, RV37, RV39 RV42, RV44, RV73, RV75, RV81, RV84, RV85, RV86, RV88, RV91, RV92, RV93, RV94, RV95, RV96, RV97, RV99 or RV101, as disclosed in

[0024] . In a further embodiment, the cationic lipid has the structure: Docket No.: 70348WO01 In a preferred embodiment, the cationic lipid has the structure: (also referred to as lipid RV39). In another preferred embodiment, the cationic lipid has the structure (referred to as Structure A): In another preferred embodiment, the cationic lipid has the structure: Docket No.: 70348WO01 In another preferred embodiment, the cationic lipid has the structure: (also referred to as lipid RV94). The lipids in the LNP may comprise (in mole %) 20-80, 25-75, 30-70, or 35-65%, preferably 30-60, 40-55 or 40-50% cationic lipid; such as about 40% (or 40%), about 42% (or 42%), about 44% (or 44%), about 46% (or 46%) or about 48% (or 48%) cationic lipid. The lipids in the LNP may comprise (in mole %) at least 20, 25 or at least 35%, or preferably at least 40% cationic lipid. The lipids in the LNP may comprise (in mole %) no more than 80, 70 or no more than 60% or preferably no more than 50% cationic lipid. The molar ratio of protonatable nitrogen atoms in the LNP’s cationic lipids to phosphates in the nucleic acid, preferably RNA (a.k.a “N:P” ratio), may be in the range of (including the endpoints) 1:1-20:1, 2:1-10:1, 3:1-9:1, or 4:1-8:1; preferably 4.5:1-7.5:1, 4.5:1-6.5:1 or 5.0:1-6.5:1. The polymer-conjugated lipid is preferably a PEGylated lipid. In an LNP, the PEGs of such PEGylated lipids may have an average molecular weight of 0.5-11.0 kDa; such as 0.5-8.0, 0.8-8.0, 0.8-7.0, 0.8- 6.0, 0.8-5.0, 0.8-4.0, 1.0-4.0 or 1.0-3.5 kDa, preferably 1.0-3.0, 1.2-2.8, 1.4-2.6, 1.5-2.5, 1.6-2.4, or 1.7-2.3 kDa, or more preferably 1.8-2.2, 1.9-2.1, about 2.0 (or 2.0 kDa). The average molecular weight of such PEGs may be expressed as the median molecular weight. In an LNP, the PEGs of such PEGylated lipids may have a weight average molecular weight of 0.5-11.0 kDa; such as 0.5-8.0, 0.8- 8.0, 0.8-7.0, 0.8-6.0, 0.8-5.0, 0.8-4.0, 1.0-4.0 or 1.0-3.5 kDa, preferably 1.0-3.0, 1.2-2.8, 1.4-2.6, 1.5- 2.5, 1.6-2.4, or 1.7-2.3 kDa, or more preferably 1.8-2.2, 1.9-2.1, about 2.0 (or 2.0 kDa). Alternatively, Docket No.: 70348WO01 in an LNP, the PEGs of such PEGylated lipids may have a number average molecular weight of 0.5- 11.0 kDa; such as 0.5-8.0, 0.8-8.0, 0.8-7.0, 0.8-6.0, 0.8-5.0, 0.8-4.0, 1.0-4.0 or 1.0-3.5 kDa, preferably 1.0-3.0, 1.2-2.8, 1.4-2.6, 1.5-2.5, 1.6-2.4, or 1.7-2.3 kDa, or more preferably 1.8-2.2, 1.9-2.1, about 2.0 (or 2.0 kDa). Alternatively, in an LNP, at least 80% of the PEGs of such PEGylated lipids may have a molecular weight of 0.5-11.0 kDa; such as 0.5-8.0, 0.8-8.0, 0.8-7.0, 0.8-6.0, 0.8-5.0, 0.8-4.0, 1.0-4.0 or 1.0-3.5 kDa, preferably 1.0-3.0, 1.2-2.8, 1.4-2.6, 1.5-2.5, 1.6-2.4, or 1.7-2.3 kDa, or more preferably 1.8-2.2, 1.9-2.1, about 2.0, or 2.0 kDa. The PEGylated lipid may have the structure: Exemplary PEGylated lipids include 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide and 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000, 1,2-dimyristoyl-sn-glycero-2- phosphoethanolamine-N-[methoxy(polyethylene glycol)] and 1,2-dimyristoyl-rac-glycerol-3- methoxypolyethylene glycol. Preferably, the PEGylated lipid is 2-[(polyethylene glycol)-2000]-N,N- ditetradecylacetamide or 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000. The lipids in the LNP may comprise (in mole %) 0.1-8.0, 0.4-7.0, 0.6-6.0, 0.8-4.0 or 0.8-3.5%, preferably 1.0-3.0% polymer-conjugated lipid (preferably PEGylated lipid); such as about 1.0 (or 1.0%), about 1.5% (or 1.5%), about 2.0% (or 2.0%) or about 2.5% (or 2.5%) polymer-conjugated lipid (preferably PEGylated lipid). The lipids in the LNP may comprise (in mole %) at least 0.1, 0.5 or at least 0.8%, or preferably at least 1% polymer-conjugated lipid (preferably PEGylated lipid). The lipids in the LNP may comprise (in mole %) no more than 8.0, 6.0 or 4.0% or preferably no more than 3.0% polymer-conjugated lipid (preferably PEGylated lipid). Preferably, the neutral lipid is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) or 1,2-dioleoyl-sn- glycero-3-phosphoethanolamine (DOPE), although other neutral lipids available to the skilled person may also be used. The lipids in the LNP may comprise (in mole %) 0-15.0, 0.1-15.0, 2.0-14.0, 5.0-13.0, 6.0-12.0 or 7.0- 11.0%, preferably 8.0-11.0% or 9.0-11.0% neutral lipid; such as about 9.4% (or 9.4%), about 9.6% (or 9.6%), about 9.8% (or 9.8%) or about 10.0% (or 10%) neutral lipid. The lipids in the LNP may comprise (in mole %) at least 0.1, 5.0 or at least 7.0%, or preferably at least 8.0% or at least 9.0% Docket No.: 70348WO01 neutral lipid. The lipids in the LNP may comprise (in mole %) no more than 15.0, 13.0 or no more than 12.0%, or preferably no more than 11.0% neutral lipid. Exemplary sterols include cholesterol, cholesterol sulfate, desmosterol, stigmasterol, lanosterol, 7- dehydrocholesterol, dihydrolanosterol, symosterol, lathosteriol, 14-demethyl-lanosterol, 8(9)- dehydrocholesterol, 8(14)-dehydrocholesterol, 14-demethyl-14-dehydrolanosterol (FF-MAS), diosgenin, dehydroepiandrosterone sulfate (DHEA sulfate), dehydroepiandrosterone, sitosterol, lanosterol-95, 4,4-dimethyl(d6)-cholest-8(9), 14-dien-3β-ol (dihydro-FF-MAS-d6), 4,4-dimethyl(d6)- cholest-8(9)-en-3β-ol (dihydro T-MAS-d6), zymostenol, sitostanol, campestanol, camperstanol, 7- dehydrodesmosterol, pregnenolone, 4,4-dimethyl-cholest-8(9)-en-3β-ol (dihyrdro T-MAS), Δ5- avensterol, brassicasterol, dihydro FF-MAS, 24-methylene cholesterol, oxysterols, deuterated sterols, fluorinated sterols, sulfonated sterols, phosphorylated sterols, A-ring substituted sterols, cholest-5-ene- 3ß,4ß-diol, 5α-cholestan-3ß-ol, 4-cholesten-3-one, cholesta-8(9),24-dien-3-one, cholesta-8(9),24- dien-3-one, 2,2,3,4,4-pentadeuterio-5a-cholestan-3ß-ol, cholesteryl phosphocholine, cholesteryl-d7 pentadecanoate, cholesteryl-d7 palmitate, B-ring substituted sterols, cholestanol, 5ß,6ß-epoxy-d7, 3ß- hydroxy-5-cholestene-7-one, 6α-hydroxy-5α-cholestane, cholestanol, 5α,6α-epoxy, cholest-5-en- 3ß,7α-diol, cholest-5-en-3ß,7ß-diol, cholestanol, 5α,6α-epoxy-d7, Δ5,7-cholesterol, cholesta-5,8(9)- dien-3ß-ol, cholesta-5,8(14)-dien-3ß-ol, 7α-hydroxy-4-cholesten-3-one, zymostenol-d7, zymostenol, 7-dehydrodesmosterol, 3b,5a-dihydroxy-cholestan-6-one, D-ring substituted sterols, 3ß-hydroxy-5α- cholest-8(14)-en-15-one, 3ß-hydroxy-5α-cholestane-15-one, 5α-cholest-8(14)-ene-3ß,15α-diol, 5α- cholest-8(14)-ene-3ß,15ß,-diol, lanosterol-95, 5α-7,24-cholestadiene, 14-dehydro zymostenol, ergosta-5,7,9(11),22-tetraen-3ß-ol, cholest-5-ene-3ß,25-diol, cholest-(25R)-5-ene-3ß,27-diol, 24(R / S),25-epoxycholesterol, 24(S),25-epoxycholesterol, 24(R / S),25-epoxycholesterol-d6, cholest-5- ene-3ß,22(S)-diol, cholest-5-ene-3ß,22(R)-diol, cholest-5-ene-3ß,24(S)-diol, cholest-5-ene-3ß,24(R)- diol, 27-hydroxy-4-cholesten-3-one, campestanol, N,N-dimethyl-3ß-hydroxycholenamide, 25,27- dihydroxycholesterol, N,N-dimethyl-3ß-hydroxycholenamide, 25,27-dihydroxycholesterol, 5- cholestene-3β,20α-diol, 24S,25-epoxy-5α-cholest-8(9)-en-3β-ol, 24(S / R),25-epoxylanost-8(9)-en-3β- ol, 7-keto-27-hydroxycholesterol, 7α,27-dihydroxy-4-cholesten-3-one, 7α,27-dihydroxycholesterol, 7ß,27-dihydroxycholesterol, 5α,6ß-dihydroxycholestanol, 7α,25-dihydroxycholesterol, 7β,25- dihydroxycholesterol, 7α,24(S)-dihydroxycholesterol, 7α,24(S)-dihydroxy-4-cholesten-3-one, 7-keto- 25-hydroxycholesterol, 7α,24S,27-trihydroxycholesterol, dihydrotestosterone, testosterone, estrone, estrogen, estradiol, corticosterone, cortisol, or 24S,27-dihydroxycholesterol. Preferably, the sterol is cholesterol or a cholesterol-based lipid (e.g. any of those provided in the foregoing paragraph). The lipids in the LNP may comprise (in mole %) 20-80, 25-80, 30-70, 30-60, 35-60 or 40-60%, preferably 40-50% or 41-49% sterol; such as about 42% (or 42%), about 43% (or 43%), about 44% Docket No.: 70348WO01 (or 44%), about 46% (or 46%), or about 48% (or 48%) sterol. The lipids in the LNP may comprise (in mole %) at least 20, 30 or at least 35%, or preferably at least 40% or at least 41% sterol. The lipids in the LNP may comprise (in mole %) no more than 80, 70 or no more than 60%, or preferably no more than 50% sterol. The lipids in the LNP may have the following mole % in combination: 30-60% cationic lipid (such as 35-55%, or preferably 40-50%), 35-70% sterol (such as 40-55%, or preferably 41-49%), 0.8-4.0% polymer-conjugated lipid (such as 0.8-3.5%, or preferably 1.0-3.0%), and 0-15% neutral lipid (such as 6.0-12.0% or preferably 8.0-11.0%). A preferred LNP comprises: (i) cationic lipid of Structure A (defined above), (ii) cholesterol, (iii) 2- [(polyethylene glycol)-2000]-N,N-ditetradecylacetamide and (iv) 1,2-distearoyl-sn-glycero-3- phosphocholine; wherein said LNP encapsulates RNA according to present disclosure (preferably according to SEQ ID NO: 104). Said preferred LNP may comprise (in mole %): (i) 30-60% cationic lipid of Structure A (defined above) (such as 35-55%, or preferably 40-50%, 44-48%, 45-47%, about 46.2% or 46.2%), (ii) 35-70% cholesterol (such as 40-55%, or preferably 40-49%, 41-45%, 42-44%, about 42.6%, or 42.6%), (iii) 0.8-4.0% 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (such as 0.8-3.5%, or preferably 1.0-3.0%, 1.6-2.0%, 1.7-1.9%, about 1.8%, or 1.8%), and (iv) 0-15% 1,2-distearoyl-sn-glycero-3- phosphocholine (such as 6.0-12.0% or preferably 8.0-11.0%, 9.0-10.0%, about 9.4%, or 9.4%); wherein said LNP encapsulates RNA according to present disclosure (preferably according to SEQ ID NO: 104). Such LNPs encapsulating nucleic acids (preferably RNA) may be formed by admixing a first solution comprising the nucleic acids with a second solution comprising lipids which form the LNP. The admixing may be performed by any suitable means available to the skilled person, e.g. a T-mixer, microfluidics, or an impinging jet mixer. Admixing may be followed by filtration to obtain a desirable LNP size distribution (e.g. those as detailed above in this subsection). The filtration may be performed by any suitable means available to the skilled person, e.g. tangential-flow filtration or cross-flow filtration. According, in a further independent aspect, the present disclosure provides a method of preparing an LNP encapsulating a nucleic acid (preferably RNA) encoding a RSV-F protein of the present disclosure, comprising admixing a first solution comprising the nucleic acid and a second solution comprising lipids which form the LNP (e.g using the means as set out in the foregoing paragraph); and optionally filtering the obtained admixture (e.g using the means as set out in the foregoing paragraph). Pharmaceutical compositions In a further independent aspect, the present disclosure also provides a pharmaceutical composition comprising an RSV-F protein, nucleic acid (preferably RNA) and / or carrier (preferably lipid Docket No.: 70348WO01 nanoparticle) of the present disclosure. Such compositions typically further comprise a pharmaceutically acceptable excipient. Pharmaceutically acceptable excipients are well-known in the art, see, e.g.

[0025] . Such compositions are generally for immunising subjects against disease, preferably against RSV. Accordingly, pharmaceutical compositions of the present disclosure are generally considered vaccine compositions. Pharmaceutical compositions of the present disclosure may comprise the RSV-F protein, nucleic acid (preferably RNA) and / or carrier (preferably lipid nanoparticle) in plain water (e.g. “w.f.i.”) or in a buffer e.g. a phosphate buffer, a Tris buffer, a borate buffer, a succinate buffer, a histidine buffer, or a citrate buffer. Buffer salts will typically be included in the 5-20mM range. Pharmaceutical compositions of the present disclosure may have a pH between 5.0 and 9.5 e.g. between 6.0 and 8.0. Pharmaceutical compositions of the present disclosure compositions may include sodium salts (e.g. sodium chloride) to give tonicity. A concentration of 10±2 mg / mL NaCl is typical, e.g. about 9 mg / mL (or 9 mg / mL).. Pharmaceutical compositions of the present disclosure may include metal ion chelators (in particular, in embodiments wherein such compositions comprise RNA). These can prolong RNA stability by removing ions which can accelerate phosphodiester hydrolysis. Thus, such compositions may include one or more of EDTA, EGTA, BAPTA, pentetic acid, etc.. Such chelators are typically present at between 10-500 μΜ e.g.0.1 mM. A citrate salt, such as sodium citrate, can also act as a chelator, while advantageously also providing buffering activity. Pharmaceutical compositions of the present disclosure may have an osmolality of between 200 mOsm / kg and 400 mOsm / kg, e.g. between 240-360 mOsm / kg, or between 290-310 mOsm / kg. Pharmaceutical compositions of the present disclosure may include one or more preservatives, such as thiomersal or 2-phenoxyethanol. Mercury-free compositions are preferred, and preservative-free vaccines can be prepared. Pharmaceutical compositions of the present disclosure may be aseptic or sterile. Pharmaceutical compositions of the present disclosure may be non-pyrogenic e.g. containing <1 EU (endotoxin unit, a standard measure) per dose, and preferably <0.1 EU per dose. Pharmaceutical compositions of the present disclosure may be gluten free. Pharmaceutical compositions of the present disclosure may be prepared in unit dose form. In some embodiments a unit dose may have a volume of between 0.1 -1.0 mL e.g. about 0.5mL (or 0.5mL). Pharmaceutical compositions of the present disclosure may be prepared as injectables, either as solutions or suspensions. The composition may be prepared for pulmonary administration e.g. by an Docket No.: 70348WO01 inhaler, using a fine spray. The composition may be prepared for nasal, aural or ocular administration e.g. as spray or drops. Injectables for intramuscular administration are typical. Pharmaceutical compositions of the present disclosure comprise an immunologically effective amount of RSV-F protein. nucleic acid (preferably RNA) and / or carrier (preferably lipid nanoparticle), as well as any other components, as needed. By “immunologically effective amount”, it is meant that the administration of that amount to an individual, either in a single dose or as part of a series, is effective for treatment or prevention, preferably prevention of RSV. This amount varies depending upon the health and physical condition of the individual to be treated, age, the taxonomic group of individual to be treated (e.g. non-human primate, primate, etc.), the capacity of the individual's immune system to synthesise antibodies, the degree of protection desired, the formulation of the vaccine, the treating doctor's assessment of the medical situation, and other relevant factors. It is expected that the amount will fall in a relatively broad range that can be determined through routine trials. In embodiments wherein pharmaceutical compositions of the present disclosure comprise RNA, the RNA content will generally be expressed in terms of the amount of RNA per dose. A preferred dose has <120µg RNA e.g. <100µg (e.g.10-120µg or 10-100 µg, such as 10µg, 25µg, 50µg, 75µg or 100µg, or about 10µg, 25µg, 50µg, 75µg or 100µg), but expression can be seen at much lower levels e.g. <1µg / dose, <100ng / dose, <10ng / dose, <1ng / dose, etc. A further preferred dose has 1-100µg RNA (e.g.1-90µg, 1- 80µg, 1-70µg, 1-60µg, 1-55µg or 1-50µg), with further preferred specific doses of 3µg, 6µg, 12.5µg, 25µg or 50µg; in particular wherein said further preferred dose (or specific dose) is administered to a subject at least twice, separated by 1-3 months, e.g. about 2 months apart or 2 months apart. Pharmaceutical compositions of the present disclosure may further comprise an adjuvant (i.e. an agent that enhances an immune response in a non-specific manner), in particular, but not exclusively, when comprising an RSV-F protein of the present disclosure. Common adjuvants include suspensions of minerals (e.g. alum, aluminum hydroxide, aluminum phosphate) onto which RSV-F proteins may be adsorbed; emulsions, including water-in-oil, and oil-in-water (and variants thereof, including double emulsions and reversible emulsions), liposaccharides, lipopolysaccharides, immunostimulatory nucleic acids (such as CpG oligonucleotides), liposomes, Toll Receptor agonists (particularly, TLR2, TLR4, TLR7 / 8 and TLR9 agonists), and various combinations of such components. In some embodiments, the adjuvant is a TLR7 agonist, such as imidazoquinoline or imiquimod. In some embodiments, the adjuvant is an aluminum salt, such as aluminum hydroxide, aluminum phosphate, aluminum sulphate. The adjuvants described herein can be used singularly or in any combination, such as alum / TLR7 (also called AS37). Pharmaceutical compositions of the present disclosure may comprise a saponin as an adjuvant, e.g. saponin fraction QS21 (see, e.g.

[0026] ). QS21 may be used in substantially pure form, e.g. at least 80% pure, such as at least 85, 90%, 95% or at least 98% pure. A suitable QS-21 fraction is as described in

[0027] . Pharmaceutical compositions of the present disclosure (preferably when comprising a lipid nanoparticle comprising a nucleic acid of the present disclosure, preferably RNA) may be lyophilised. Docket No.: 70348WO01 In some embodiments, pharmaceutical compositions of the present disclosure comprise (i) a nucleic acid (preferably RNA) encoding an RSV-F protein of the present disclosure, and (ii) a further nucleic acid (preferably RNA) encoding at least one further protein. The nucleic acids of (i) and (ii) may be comprised within the same carrier (preferably lipid nanoparticle), or within separate carriers (preferably lipid nanoparticles). In preferred embodiments, the at least one further protein is an antigen; and as such may comprise, or may be, a viral, bacterial, fungal, parasitic, tumour, or allergenic (i.e. from, or derived from, an allergen) antigen. The at least one further protein will typically be a pathogen antigen. The at least one further protein will typically be an antigen that is a surface polypeptide e.g. a spike glycoprotein, a haemagglutinin, an adhesin or an envelope glycoprotein. In a particular embodiment, the at least one further protein is an antigen from, or derived from, a virus, in particular a virus causing respiratory disease, in particular a seasonal virus causing respiratory disease. In embodiments wherein the at least one further protein is an antigen from, or derived from, a virus, examples of such viruses include: Coronavirus, Orthomyxovirus, Pneumoviridae, Paramyxoviridae, Poxviridae, Picornavirus, Bunyavirus, Heparnavirus, Filovirus, Togavirus, Flavivirus, Pestivirus, Hepadnavirus, Rhabdovirus, Caliciviridae, Retrovirus, Reovirus, Parvovirus, Herpesvirus, Papovaviruses and Adenovirus. In a preferred embodiment, the at least one further protein encoded by the nucleic acid of (ii) is a further Pneumoviridae protein (in particular a Pneumoviridae antigen). Useful further Pneumoviridae proteins (in particular, antigens) can be from an Orthopneumovirus or Metapneumovirus, in particular human RSV or human Metapneumovirus (hMPV). Useful further hMPV antigens include e.g. the F, N, P, M, M2-1, and M2 antigens (in particular, the F antigen). Such hMPV proteins (in particular, antigens) may be from, or derived from, the A or B subtype. In a preferred embodiment, the nucleic acid of (i) is RNA encoding an RSV-F protein of the present disclosure and the nucleic acid of (ii) is RNA encoding an hMPV antigen (in particular, the F antigen). In such RNA embodiments, a preferred patient group (in which the pharmaceutical composition may be used in therapy, in particular vaccination) is infants (see section entitled Medical uses and methods of treatment, below). Useful further human RSV antigens encoded by the nucleic acid of (ii) include e.g. the G, M1, M2-1, M2-2, P, L, N, NS1, NS2 and SH antigens, in addition to further RSV-F antigens, i.e. of distinct amino acid sequence to the RSV-F protein of the present disclosure encoded by the nucleic acid. Such further human RSV proteins (in particular, antigens, in particular F antigens) may be from, or derived from, the A or B subtype, in particular the B subtype. In a preferred embodiment, the at least one further protein encoded by the nucleic acid of (ii) is a Coronavirus antigen. Useful Coronavirus antigens can be from a SARS coronavirus, in particular SARS-CoV2. Useful Coronavirus antigens (preferably SARS-CoV2 antigens) include the spike, M, E, HE, Nuclocapsid, Plpro and 3CLPro proteins, in particular spike protein. Preferably, the Coronavirus antigen is a SARS-CoV2 spike protein. Said SARS-CoV2 spike protein may be from any variant, e.g. Omicron (such as Omicron BA.1, BA.2, BA3, BA.4 or BA.5), Alpha, Epsilon, Eta, Theta, Docket No.: 70348WO01 Kappa, Iota, Zeta, Mu, Lambda, Beta, Gamma, or Delta. Preferably, said SARS-CoV2 spike protein includes one or more mutations relative to the wild-type protein, in particular one or more (e.g. two) mutations to proline resides. Said one or more mutations may be introduced to stabilise said SARS- CoV2 spike protein in its pre-fusion conformation. In a preferred embodiment, the nucleic acid of (i) is RNA encoding an RSV-F protein of the present disclosure and the nucleic acid of (ii) is RNA encoding a Coronavirus antigen, e.g. as detailed above. In such RNA embodiments, a preferred patient group (in which the pharmaceutical composition may be used in therapy, in particular vaccination) is older adults (see section entitled Medical uses and methods of treatment, below). In another preferred embodiment, the at least one further protein encoded by the nucleic acid of (ii) is an Orthomyxovirus antigen. Useful Orthomyxovirus antigens can be from an influenza A, B or C virus. Useful Orthomyxovirus antigens (in particular influenza A, B or C virus antigens) include the haemagglutinin, neuraminidase and matrix M2 proteins, in particular haemagglutinin. Preferably, the Orthomyxovirus antigen is an influenza A virus haemagglutinin. Said influenza A virus hemagglutinin may be from any subtype e.g. H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15 or H16. In a preferred embodiment, the nucleic acid of (i) is RNA encoding an RSV-F protein of the present disclosure and the nucleic acid of (ii) is RNA encoding an Orthomyxovirus antigen, e.g. as detailed above. In such RNA embodiments, a preferred patient group (in which the pharmaceutical composition may be used in therapy, in particular vaccination) is older adults (see section entitled Medical uses and methods of treatment, below). In such RNA embodiments, the nucleic acid of (i) may encode an RSV-F protein of the present disclosure, the nucleic acid of (ii) may encode an Orthomyxovirus antigen, e.g. as detailed above, and (iii) a third nucleic acid may be present in the pharmaceutical composition which may encode a Coronavirus antigen, e.g. as detailed above in the preceding paragraph. In some embodiments, pharmaceutical compositions of the present disclosure comprise (i) a first plurality of RSV-F proteins and / or trimers according to the present disclosure, wherein the RSV-F proteins and / or trimers are of the A subtype; and (ii) a second plurality of RSV-F proteins and / or trimers according to the present disclosure, wherein the RSV-F proteins and / or trimers are of the B subtype. In some embodiments, pharmaceutical compositions of the present disclosure comprise (i) a first plurality of nucleic acids (preferably RNAs) and / or carriers (preferably lipid nanoparticles) according to the present disclosure, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the present disclosure of the A subtype; and (ii) a second plurality of nucleic acids (preferably RNAs) and / or carriers (preferably lipid nanoparticles) according to the present disclosure, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the present disclosure of the B subtype. Docket No.: 70348WO01 In a further independent aspect, the present disclosure also provides a delivery device (e.g. syringe, nebuliser, sprayer, inhaler, dermal patch, etc.) comprising a pharmaceutical composition of the present disclosure. This device can be used to administer the composition to a vertebrate subject. In a further independent aspect, the present disclosure also provides a method of preparing a pharmaceutical composition, comprising formulating an RSV-F protein, nucleic acid (preferably RNA) or carrier (preferably lipid nanoparticle) of the present disclosure with a pharmaceutically acceptable excipient, to produce said composition. In particular, said pharmaceutical composition has the features as detailed above throughout this section. In a further independent aspect, the present disclosure also provides a kit comprising an RSV-F protein, nucleic acid, carrier, pharmaceutical composition or delivery device of the present disclosure, and instructions for use. Medical uses and methods of treatment The present disclosure also provides, in a further independent aspect, an RSV-F protein, nucleic acid (preferably RNA), carrier (preferably lipid nanoparticle) or pharmaceutical composition of the present disclosure, for use in medicine. Said use will generally be in a method for raising an immune response in a subject. The present disclosure also provides, in a further independent aspect, the use of an RSV-F protein, nucleic acid (preferably RNA), carrier (preferably lipid nanoparticle) or pharmaceutical composition of the present disclosure, in the manufacture of a medicament. Said medicament will generally be for raising an immune response in a subject. The present disclosure also provides, in a further independent aspect, a therapeutic method comprising the step of administering an effective amount of an RSV-F protein, nucleic acid (preferably RNA), carrier (preferably lipid nanoparticle) or pharmaceutical composition of the present disclosure to a subject (preferably a subject in need of such administration). Said method will generally be for raising an immune response in the subject. The immune response is preferably protective and, preferably involves antibodies and / or cell-mediated immunity. Generally, the subject is a vertebrate, preferably a mammal, more preferably a human or large veterinary mammal (e.g. horses, cattle, deer, goats, pigs), even more preferably a human. The RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure may be for use in the prevention, reduction or treatment of infection or disease. In addition, or alternatively, the RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure may be for use in the prevention, reduction or treatment of symptoms associated with infection or disease. The infection is generally one by, and said disease is generally one associated with, a Pneumoviridae virus. In preferred embodiments, the Pneumoviridae virus is an Docket No.: 70348WO01 Orthopneumovirus, which is more preferably RSV, and even more preferable human RSV (including both the A and B subtypes thereof). Accordingly, the present disclosure also provides an RSV-F protein, nucleic acid, carrier or pharmaceutical composition of the present disclosure; for use in treating of preventing RSV (preferably a method of vaccination against RSV). The present disclosure also provides the use of an RSV-F protein, nucleic acid, carrier or pharmaceutical composition of the present disclosure, in the manufacture of a medicament for treating or preventing RSV (preferably wherein the medicament is a vaccine). The present disclosure also provides a method of inducing an immune response against RSV in a subject (preferably a method of vaccinating a subject against RSV), comprising administering to the subject an immunologically effective amount of the RSV-F protein, nucleic acid, carrier or pharmaceutical composition of the present disclosure to the subject. Vaccination according to the present disclosure may either be prophylactic (i.e. to prevent infection) or therapeutic (i.e. to treat infection), but will typically be prophylactic. Such methods of vaccination may comprise administration of a single dose. Alternatively, such methods of vaccination may comprise a vaccination regimen (i.e. administration of multiple doses). Such regimens may involve the repeated administration of an immunologically identical protein antigen (in the form of, or delivered via, an RSV-F protein, nucleic acid, carrier, or pharmaceutical composition of the present disclosure), in particular in a prime-boost regimen. In a prime-boost regimen, the first administration (“prime”) may induce proliferation and maturation of B and / or T cell precursors specific to one or more immunogenic epitopes present on the delivered antigen (induction phase). The second (and in some cases subsequent) administration (“boost”), may further stimulate and potentially select an anamnestic response of cells elicited by the prior administration(s). The different administrations may be given by the same or different routes e.g. a parenteral prime and mucosal boost, a mucosal prime and parenteral boost, etc. The prime administration(s) and boost administration(s) will be temporally separated, e.g. by at least: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or more months. In some embodiments, two prime administrations may be administered 3-9 weeks apart (e.g.4-9, 5-9, 6-9, 7-9 or 7-8 weeks apart, or about two months apart), followed by one or more boost administrations 4-14 months after the second prime administration (e.g.5-13, 6-13, 7-13, 8-13, 9-13, 10-13 or 11-13 months, or about one year). In some embodiments, prime administration is to a naïve subject. In some embodiments, the protein antigen may be delivered in the prime and boost administrations as, or via, different formats. For example, the protein antigen may be delivered as a protein for the prime administration(s), and via a nucleic acid (in particular RNA, in particular via a carrier comprising RNA) for the boost administration(s), or vice versa. Alternatively, different nucleic acid formats may be used, e.g. the protein antigen may be delivered via RNA (in particular via a carrier comprising RNA) for the prime administration(s), and a via a viral vector (e.g. an adenoviral vector) for the boost administration(s), or vice versa. Docket No.: 70348WO01 The RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure will generally be administered directly to the subject. Direct delivery may be accomplished by parenteral injection (e.g. subcutaneously, intraperitoneally, intravenously, intramuscularly, intradermally, or to the interstitial space of a tissue). Alternative delivery routes include rectal, oral (e.g. tablet, spray), buccal, sublingual, vaginal, topical, transdermal or transcutaneous, intranasal, ocular, aural, pulmonary or other mucosal administration. Preferably, the RSV-F proteins, nucleic acids, carriers, or pharmaceutical composition of the present disclosure will be administered intramuscularly or intradermally (in particular via a needle such as a hypodermic needle), more preferably intramuscularly. In some embodiments, the subject is administered (i) a first plurality of nucleic acids (preferably RNAs) and / or carriers (preferably lipid nanoparticles) according to the present disclosure, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the A subtype; and (ii) a second plurality of nucleic acids (preferably RNAs) and / or carriers (preferably lipid nanoparticles) according to the present disclosure, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the B subtype; wherein the first plurality and second plurality are administered simultaneously, separately or sequentially to one another (preferably simultaneously, e.g. in the same composition). In some embodiments, the subject is administered (i) a first plurality of nucleic acids (preferably RNAs) and / or carriers (preferably lipid nanoparticles) according to the present disclosure, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the present disclosure of the A subtype; and (ii) a second plurality of nucleic acids (preferably RNAs) and / or carriers (preferably lipid nanoparticles) according to the present disclosure, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the present disclosure of the B subtype; wherein the first plurality and second plurality are administered simultaneously, separately or sequentially to one another (preferably simultaneously, e.g. in the same composition). The RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure may be used to elicit systemic and / or mucosal immunity. The subject of a method of vaccination according to the present disclosure may be a child (preferably an infant) or adult (preferably an older adult or pregnant female). Immunocompromised individuals may also be the subject of such vaccination (whether children or adults). Infant vaccination In a preferred embodiment, the RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure are administered to infants (preferably human infants), as the subject of vaccination. The immune systems of infants are immature (see, e.g.

[0028] ), hence this Docket No.: 70348WO01 population is susceptible to RSV infection and resulting disease. Infant vaccination may prevent lower respiratory tract infection (in particular, bronchiolitis and (broncho-)pneumonia). The infant may be less than one year old, such as less than: 11, 10, 9, 8, 7, 6, 5, 4 or less than 3 months old. The infant may be ≥one month old, such as ≥: 2, 3, 4, 5 or ≥6 months old. Preferably the infant is 2-6 months old (i.e. within and including the ages of 2 and 6 months), more preferably 2-4 months old. In a preferred embodiment, the infant was born from a female to whom an RSV vaccine (such as an RSV-F protein, nucleic acid, carrier, or pharmaceutical composition of the present disclosure) was administered, preferably while pregnant with said infant. The combination of maternal and infant vaccination may advantageously provide passive transfer of maternal antibodies (i.e. via the placenta and / or breast milk) to, in addition to active immunity generated by, the infant. Older adult vaccination In another preferred embodiment, the RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure are administered to older adults (preferably human older adults), as the subject of vaccination. Older adults may suffer from age-related immunosenescence (reviewed in, e.g.

[0029] ), hence this population is also susceptible to RSV infection and resulting disease. Older adult vaccination may prevent lower respiratory tract infection (in particular, pneumonia). The older adult may be ≥50 years old, such as ≥: 55, 60, 65, 70, 75, 80, 85, 90, 95 or ≥100 years old. Preferably, the older adult is ≥60 or ≥65 years old (such as 60-120 or 65-120 years old). Pregnant female vaccination In another preferred embodiment, the RSV-F proteins, nucleic acids, carriers, or pharmaceutical compositions of the present disclosure are administered to pregnant females (preferably pregnant human females), as the subject of vaccination. The primary object of maternal vaccination is to protect the infant from RSV infection when born, e.g. through passive transfer of antibodies via the placenta and / or breast milk. The pregnant female may be in her first, second or third trimester of pregnancy, preferably third trimester. The pregnant female may be ≥20 weeks pregnant, such as ≥: 22, 24, 26, 28, 30, 32, 34, 36 or ≥38 weeks pregnant. Preferably, the pregnant female is ≥28 , ≥29 or ≥30 weeks pregnant (such as 28-43, 29-43 or 30-43 weeks pregnant). General The practice of the present disclosure will employ, unless otherwise indicated, conventional methods of chemistry, biochemistry, molecular biology, immunology and pharmacology. The singular terms "a," "an," and "the" include plural referents unless context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise. The term "plurality" refers to two or more. The term “at least one” refers to one or more. Docket No.: 70348WO01 Unless specified otherwise, where a numerical range is provided, it is inclusive, i.e., the endpoints are included. The terms “at least”, “no more than” and other such terms preceding a list of values are applicable to all members of said list (not merely the first member thereof), unless otherwise stated. The term “comprising” encompasses “including” as well as “consisting” e.g. a composition “comprising” X may consist exclusively of X or may include something additional e.g. X + Y. The term “about” in relation to a numerical value x is optional and means, for example, x+10%. The word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the present disclosure. References to charge, to cations, to anions, etc., are taken at pH 7. Embodiments The present disclosure also provides the following numbered embodiments. Combinations of features of the present disclosure presented below are exemplary, and not to be construed as exhaustive. 1. An RSV-F protein, comprising at least two mutations relative to SEQ ID NO: 1 or 3 within a region of the protein corresponding to positions 474-523 of SEQ ID NO: 1 or 3; wherein the at least two mutations introduce, through substitution or insertion, a pair of C residues into the region, which form a disulphide bond. 2. The RSV-F protein of embodiment 1, wherein the pair of C residues form an intra-protomer disulphide bond. 3. The RSV-F protein of embodiment 1 or 2, wherein the pair of C residues is within a region of the protein corresponding to positions 474-513 of SEQ ID NO: 1 or 3. 4. The RSV-F protein of embodiment 3, wherein a first C residue of said pair is within a region of the protein corresponding to positions 478-501 of SEQ ID NO: 1 or 3. 5. The RSV-F protein of embodiment 3 or 4, wherein a second C residue of said pair is within a region of the protein corresponding to positions 482-504 of SEQ ID NO: 1 or 3. 6. The RSV-F protein of embodiment 4 or 5, wherein the pair of C residues is at positions 486 and 490, 485 and 494, 480 and 497, 490 and 494, 479 and 482, 484 and 498, 487 and 490, 491 and 494, 482 and 502, 478 and 483, 481 and 501, 482 and 499, 486 and 489, 486 and 488, 485 and 494, 480 and 487, or 501 and 504 of SEQ ID NO: 1 or 3. 7. The RSV-F protein of embodiment 4 or 5, wherein a first C residue of said pair is within a region of the protein corresponding to positions 478-491 of SEQ ID NO: 1 or 3. Docket No.: 70348WO01 8. The RSV-F protein of embodiment 4, 5 or 7, wherein a second C residue of said pair is within a region of the protein corresponding to positions 482-502 of SEQ ID NO: 1 or 3. 9. The RSV-F protein of embodiment 7 or 8, wherein the pair of C residues is at positions 486 and 490, 485 and 494, 480 and 497, 490 and 494, 479 and 482, 484 and 498, 487 and 490, 491 and 494, 482 and 502, or 478 and 483 of SEQ ID NO: 1 or 3. 10. The RSV-F protein of embodiment 7 or 8, wherein a first C residue of said pair is within a region of the protein corresponding to positions 480-486 of SEQ ID NO: 1 or 3. 11. The RSV-F protein of embodiment 7, 8 or 10, wherein a second C residue of said pair is within a region of the protein corresponding to positions 490-497 of SEQ ID NO: 1 or 3. 12. The RSV-F protein of embodiment 10 or 11, wherein the pair of C residues is at positions 486 and 490, 485 and 494, or 480 and 497 of SEQ ID NO: 1 or 3. 13. The RSV-F protein of embodiment 12, wherein the pair of C residues is at positions 486 and 490 of SEQ ID NO: 1 or 3. 14. An RSV-F protein comprising a C residue at position 486 and a C residue at position 490; wherein the C residues form a disulphide bond. 15. The RSV-F protein of embodiment 14, wherein the pair of C residues form an intra-protomer disulphide bond. 16. The RSV-F protein of any preceding embodiment, wherein the RSV-F protein does not comprise a deletion at position 137 (e.g. relative to SEQ ID NO: 1 or 3). 17. The RSV-F protein of embodiment 16, wherein the RSV-F protein comprises neither (i) a deletion of the fusion peptide, nor (ii) substitution of the fusion peptide for a linker sequence (e.g. relative to SEQ ID NO: 1 or 3). 18. The RSV-F protein of embodiment 17, wherein the RSV-F protein comprises neither (i) a deletion of p27 and the fusion peptide, nor (ii) substitution of p27 and the fusion peptide for a linker sequence (e.g. relative to SEQ ID NO: 1 or 3). 19. The RSV-F protein of any of embodiments 16-18, comprising an aromatic residue at position 137, such as F, W, Y or H; optionally F, W or Y. 20. The RSV-F protein of embodiment 19, wherein the aromatic residue at position 137 is F. 21. The RSV-F protein of any preceding embodiment, comprising an aromatic residue at position 488, such as F, W, Y or H; optionally F, W or Y; optionally F. 22. The RSV-F protein of embodiment 21, wherein the aromatic residue at position 488 is F. Docket No.: 70348WO01 23. The RSV-F protein of embodiment 21 or 22, comprising a pi-pi stacking interaction between the aromatic residue at position 137 and the aromatic residue at position 488. 24. The RSV-F protein of any preceding embodiment, comprising a positively charged residue at position 339, such as K, R or H, optionally K or R, optionally K. 25. The RSV-F protein of embodiment 24, wherein the positively charged residue at position 339 is K. 26. The RSV-F protein of embodiment 24 or 25, comprising a pi-pi-cation stacking interaction between the aromatic residue at position 137, the aromatic residue at position 488 and the positively charged residue at position 339. 27. The RSV-F protein of any of embodiments 19-26, wherein the residue numbering is according to SEQ ID NO: 1 or 3 28. The RSV-F protein of any preceding embodiment, which is in the pre-fusion conformation. 29. The RSV-F protein of any preceding embodiment, comprising one or more further mutations, optionally one or more further substitutions, which stabilise and / or promote the pre-fusion conformation of RSV-F. 30. The RSV-F protein of embodiment 29, comprising at least 2, 3, 4, 5, 6 or 7 further mutations, optionally substitutions, which stabilise and / or promote the pre-fusion conformation of RSV- F. 31. The RSV-F protein of any preceding embodiment, comprising a substitution at position 228 for K, R or Q, optionally K or R; and / or a substitution at position 232 for N. 32. The RSV-F protein of embodiment 31, comprising a substitution at position 228 for K, R or Q; optionally K or R. 33. The RSV-F protein of embodiment 32, comprising a substitution at position 228 for K. 34. The RSV-F protein of any preceding embodiment, comprising a substitution at position 55 for T, C, V, I or F; optionally T, C or V; optionally T or C. 35. The RSV-F protein of embodiment 34, comprising a substitution at position 55 for T. 36. The RSV-F protein of any preceding embodiment, comprising a substitution at position 215 for A, P, V, I, or F; optionally A or P. 37. The RSV-F protein of embodiment 36, comprising a substitution at position 215 for A. 38. The RSV-F protein of any of embodiments 31-36, comprising a substitution at position 228 for K, a substitution at position 55 for T, and a substitution at position 215 for A. Docket No.: 70348WO01 39. The RSV-F protein of any preceding embodiment, comprising a substitution at position 152 for R, L or W; optionally R or W. 40. The RSV-F protein of embodiment 39, comprising a substitution at position 152 for R. 41. The RSV-F protein of any preceding embodiment, comprising a substitution at position 315 for I or V. 42. The RSV-F protein of embodiment 41, comprising a substitution at position 315 for I. 43. The RSV-F protein of any preceding embodiment, comprising a substitution at position 346 for Q, D, H, K, N, R, S or W; optionally Q, D, H, K, N, R or S. 44. The RSV-F protein of embodiment 43, comprising a substitution at position 346 for Q. 45. The RSV-F protein of any preceding embodiment, comprising a substitution at position 445 for D. 46. The RSV-F protein of any preceding embodiment, comprising a substitution at position 455 for V or I. 47. The RSV-F protein of embodiment 46, comprising a substitution at position 455 for V. 48. The RSV-F protein of any preceding embodiment, comprising a substitution at position 459 for M. 49. The RSV-F protein of any preceding embodiment, comprising: a substitution at position 55 for T, a substitution at position 152 for R, a substitution at position 215 for A, a substitution at position 228 for K, a substitution at position 315 for I, a substitution at position 346 for Q, a substitution at position 445 for D, a substitution at position 455 for V, a substitution at position 459 for M, a substitution at position 486 for C, and a substitution at position 490 for C. Docket No.: 70348WO01 50. The RSV-F protein of any of embodiments -49, wherein the substitution(s) are relative to SEQ ID NO: 1 or 3, and / or the residue numbering of the substitution(s) is according to SEQ ID NO: 1 or 3. 51. The RSV-F protein of any preceding embodiment, comprising (i) an F2 domain comprising or consisting of an amino acid sequence according to positions 26-109 of SEQ ID NO: 28 or positions 26-102 of SEQ ID NO: 32, and an F1 domain comprising or consisting of an amino acid sequence according to positions 137-513 of SEQ ID NO: 28 or positions 105-472 of SEQ ID NO: 32; or (ii) an F2 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identity to positions 26-109 of SEQ ID NO: 28 or positions 26-102 of SEQ ID NO: 32, and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5% to 137- 513 of SEQ ID NO: 28 or positions 105-472 of SEQ ID NO: 32. 52. The RSV-F protein of any preceding embodiment, comprising or consisting of (i) the amino acid sequence of SEQ ID NO: 83, 69, 47, 57, 73 or 87; or (ii) an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5% identity to any of SEQ ID NO: 83, 69, 47, 57, 73 or 87. 53. The RSV-F protein of any preceding embodiment, which, when in the form of a homotrimer, is specifically bound by a pre-fusion mAb comprising a LC and HC according to SEQ ID NO: 7 and 8 respectively with a KD, as measured via SPR, of less than 1000, 900, 800, 700, 600, 500, 400, 350, 320, 300, 200, 150, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25 or 20 pM. 54. The RSV-F protein of any preceding embodiment, which is specifically bound by a pre- fusion mAb comprising a LC and HC according SEQ ID NO: 9 and 10 respectively with a KD, as measured via SPR, of less than 5000, 4000, 3000, 2500, 2000, 1900, 1850, 1500, 1000, 800, 600, 400, 200, 100, 90, 80, 75, 70 or 65 pM. 55. The RSV-F protein of any preceding embodiment, which is specifically bound by a pre- fusion mAb comprising a LC and HC according SEQ ID NO: 11 and 12 respectively with a KD, as measured via SPR, of less than 1000, 500, 450, 400, 350, 300, 250, 200, 190, 180, 170, 160, 150, 140, 130, 125, 120, 100, 90, 80, 70 or 65 pM. 56. The RSV-F protein of any preceding embodiment, having a Tm1 of at least 65.5, 66.0, 66.5, 67.0, 67.5, 68.0, 68.5, 69.0, 69.5, 70.0, 70.5, 71.0, 71.5, 72.0, 72.5, 73.0, 73.5, or 74.0 °C, when in the form of a homotrimer. 57. The RSV-F protein of embodiment 56, having a Tm1 of at least, or of, 65.7°C. Docket No.: 70348WO01 58. The RSV-F protein of embodiment 56, having a Tm1 of at least, or of, 72.3°C. 59. The RSV-F protein of embodiment 56, having a Tm1 of at least, or of, 74.4°C. 60. The RSV-F protein of any preceding embodiment, having a Tm2 of at least 78.0, 78.5, 79.0, 79.5.5, 80.0, 80.5, 81.0, 81.5, 82.0, 82.5, 83.0, or 83.5 °C, when in the form of a homotrimer. 61. The RSV-F protein of embodiment 60, having a Tm2 of at least, or of, 80.8 °C. 62. The RSV-F protein of embodiment 60, having a Tm2 of at least, or of, 79.4 °C. 63. The RSV-F protein of embodiment 60, having a Tm2 of at least, or of, 80.7 °C. 64. The RSV-F protein of any of embodiments 55-63, wherein the Tm1 and / or the Tm2 is measured via differential scanning fluorimetry; optionally nano-differential scanning fluorimetry. 65. The RSV-F protein of any of embodiments 56-64, comprising a bacteriophage T4 fibritin foldon trimerisation domain at the C-terminus thereof, and / or C-terminal to the F1 domain, when the Tm1 and / or Tm2 is measured; optionally wherein RSV-F protein comprises a C- terminal domain comprising or consisting of positions 514-596 of SEQ ID NO: 2 or . 66. The RSV-F protein of any preceding embodiment, comprising a heterologous trimerisation domain on the C-terminus thereof and / or C-terminal to the F1 domain, optionally wherein the heterologous trimerisation domain is a T4 fibritin foldon domain, optionally according to SEQ ID NO: 19. 67. The RSV-F protein of embodiments 1-65, comprising a transmembrane domain, and optionally a cytoplasmic tail C-terminal to said transmembrane domain. 68. The RSV-F protein of any of embodiments 1-65 or 67, comprising a cytoplasmic tail; wherein, relative to a cytoplasmic tail according to SEQ ID NO: 5 or 6, 2-23 residues are deleted from the C-terminal end of the cytoplasmic tail. 69. The RSV-F protein of embodiment 68, wherein 2-22, 2-21, 2-20 or 3-20 residues are deleted from the C-terminal end of the cytoplasmic tail of the RSV-F protein. 70. The RSV-F protein of embodiment 68 or 69, wherein 2-5, such as 2-4, 2-3, 3-4 or 3 residues are deleted from the C-terminal end of the cytoplasmic tail of the RSV-F protein. 71. The RSV-F protein of any of embodiments 68-70, wherein the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-22 of SEQ ID NO: 5 or 6; or (ii) an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). Docket No.: 70348WO01 72. The RSV-F protein of embodiment 69, wherein 16-20, such as 17-20, 18-20 or 19-20 residues are deleted from the C-terminal end of the cytoplasmic tail of the RSV-F protein. 73. The RSV-F protein of embodiment 72, wherein 20 residues are deleted from the C-terminal end of the cytoplasmic tail of the RSV-F protein. 74. The RSV-F protein of any of embodiments 69, 72 or 73 wherein the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-5 of SEQ ID NO: 5 or 6, or (ii) an amino acid sequence at least 60% or at least 80% identical to positions 1-5 of SEQ ID NO: 5 or 6 and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). 75. The RSV-F protein of any of embodiments 68-74, wherein the deletions increase the cell- surface expression, optionally in human fibroblasts, optionally in human foreskin fibroblasts, optionally in human primary BJ cells, optionally the ATCC CRL-2522 cell line, of the RSV- F protein in trimeric, pre-fusion form from a nucleic acid, relative to expression in such form of an RSV-F protein having the same amino acid but absent such deletions, such as an RSV- F protein comprising a cytoplasmic tail according to SEQ ID NO: 5 or 6. 76. The RSV-F protein of embodiment 75, wherein the increased cell surface expression is for a period of at least 24, 48, 72 or 96 hours. 77. The RSV-F protein of any preceding embodiment, wherein a signal peptide is not present in the RSV-F protein, optionally as a result of signal peptide cleavage, optionally wherein the signal peptide is or corresponds to positions 1-25 of SEQ ID NO: 1 or 3. 78. The RSV-F protein of any preceding embodiment, wherein a p27 peptide is not present in the RSV-F protein, optionally as a result of furin processing, optionally wherein the p27 peptide is or corresponds to positions 110-136 of SEQ ID NO: 1 or 3. 79. The RSV-F protein of any preceding embodiment, comprising an F2 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to positions 26-109 of SEQ ID NO: 1; and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%, sequence identity to positions 137-523 or 137-513 of SEQ ID NO: 1. 80. The RSV-F protein of any preceding embodiment, comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to SEQ ID NO: 1. Docket No.: 70348WO01 81. The RSV-F protein of any preceding embodiment, wherein the RSV-F protein is of the A subtype. 82. The RSV-F protein of any of embodiments 1-78, comprising an F2 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to positions 1-109 of SEQ ID NO: 3; and an F1 domain comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%, sequence identity to positions 137-523 or 137-513 of SEQ ID NO: 3. 83. The RSV-F protein of any of embodiments 1-78 or 82, comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to SEQ ID NO: 3. 84. The RSV-F protein of any of embodiments 1-78, 82 or 83, wherein the RSV-F protein is of the B subtype. 85. A trimer comprising three RSV-F proteins of any preceding embodiment. 86. A trimer according to embodiment 85, wherein the trimer is a homotrimer. 87. A trimer according to embodiment 85 or 86, comprising an electrostatic repulsive ring comprising three negatively charged residues, each of which is in an HRB domain of an RSV-F protein in the trimer. 88. A trimer according to embodiment 87, wherein the negatively charged residues are at position 487 of each of the RSV-F proteins; optionally wherein the negatively-charged residue is E487 or D487; optionally wherein the negatively charged residue is E487. 89. A trimer according to embodiment 87 or 88, wherein the distances between each of the negatively-charged residues in the trimer are increased relative to such distances in a trimer comprising three RSV-F proteins comprising or consisting of SEQ ID NO: 1, 2, 3 or 4. 90. A trimer according to any of embodiments 87-89, wherein the distances between each of the negatively-charged residues in the trimer are at least 5.0, 5.5, 6.0, 6.5, 7.0 or 7.2 Å. 91. A nucleic acid encoding the RSV-F protein of any of embodiments 1-84. 92. The nucleic acid of embodiment 91, wherein the nucleic acid is, or is comprised within, a viral vector; optionally wherein the viral vector is an adenovirus vector. 93. The nucleic acid of embodiment 91, wherein the nucleic acid is DNA; optionally wherein the DNA is a DNA plasmid. Docket No.: 70348WO01 94. The nucleic acid of embodiment 91, wherein the nucleic acid is RNA. 95. The RNA of embodiment 94, which is non-self-replicating RNA. 96. The RNA of embodiment 94, which is self-replicating RNA. 97. The RNA of any of embodiments 94-96, comprising, in the 5’ to 3’ direction: a 5’ Cap, a 5’ UTR, an open reading frame encoding at least an RSV-F protein according to any of embodiments 1-84, a 3’UTR, and a 3’ poly-A tail. 98. The RNA of embodiment 97, wherein the 5’ cap comprises a 7’-methylguanosine linked 5’- to-5’ to the 5’ first ribonucleoside by a triphosphate bridge, and wherein the first 5’ ribonucleoside comprises a 2’-methylated ribose (2’-O-Me). 99. The RNA of embodiment 97 or 98 or, wherein the 3’ poly-A tail comprises a contiguous stretch of 100-500 A ribonucleotides. 100. The RNA of embodiment 97 or 98, wherein the 3’ poly-A tail comprises at least two non-contiguous stretches of A ribonucleotides; optionally: (a) 25-35 and 65-90 ribonucleotides in length respectively; optionally orientated in the 5’ to 3’ direction, or (b) 25-35 and 25-45 ribonucleotides in length respectively which are optionally orientated in the 5’ to 3’ direction. 101. The RNA of any of embodiments 94-100, comprising a modified ribonucleotide. 102. The RNA of embodiment 101, wherein the modified ribonucleotide is 1mΨ 103. The RNA of embodiment 102 wherein the RNA comprises 1mΨ and neither standard U ribonucleotides nor other modified U ribonucleotides; optionally wherein the RNA comprises 1mΨ and neither standard U ribonucleotides nor other modified ribonucleotides. 104. The RNA of any of embodiments 94-103, having a GC content of 55-70%. 105. The RNA of any of embodiments 94-103, having a GC content of 40-60%. 106. The RNA of any of embodiments 94-105, comprising or consisting of (i) SEQ ID NO: 82, 104, 128, 68, 56, 46, 86 or 72; or (ii) an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to any of said sequences. 107. The RNA of embodiment 106, comprising or consisting of (i) SEQ ID NO: 104; or (ii) an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to SEQ ID NO: 104. Docket No.: 70348WO01 108. The RNA of any of embodiments 94-107, comprising an open reading frame (ORF) comprising or consisting of (i) positions 32-1693 of SEQ ID NO: 82, positions 32-1693 of SEQ ID NO: 104, positions 32-1693 of SEQ ID NO: 128, positions 32-1753 of SEQ ID NO: 68, positions 32-1693 of SEQ ID NO: 56, positions 32-1753 of SEQ ID NO: 46, positions 32-1693 of SEQ ID NO: 86, or positions 32-1753 of SEQ ID NO: 72; or (ii) an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to any of positions 32-1693 of SEQ ID NO: 82, positions 32-1693 of SEQ ID NO: 104, positions 32-1693 of SEQ ID NO: 128, positions 32-1753 of SEQ ID NO: 68, positions 32- 1693 of SEQ ID NO: 56, positions 32-1753 of SEQ ID NO: 46, positions 32-1693 of SEQ ID NO: 86, or positions 32-1753 of SEQ ID NO: 72; preferably wherein the RNA comprises an ORF comprising or consisting of (i) positions 32- 1693 of SEQ ID NO: 104; or (ii) an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to positions 32-1693 of SEQ ID NO: 104. 109. A carrier comprising nucleic acid of any of embodiments 91 or 93-108. 110. The carrier of embodiment 109, which is a lipid nanoparticle. 111. The lipid nanoparticle of embodiment 110, comprising a mixture of cationic lipids, neutral lipids, sterols and polymer-conjugated lipids. 112. The lipid nanoparticle of embodiment 111, wherein the cationic lipid has a pKa of 5.0-8.0; optionally 5.0-7.6. 113. The lipid nanoparticle of embodiment 111 or 112, wherein the cationic lipid comprises a tertiary amine group. 114. The lipid nanoparticle of any of embodiments 111-113, wherein the polymer- conjugated lipid is a PEGylated lipid; optionally wherein the PEG has an average molecular weight of 1-3 kDa. 115. The lipid nanoparticle of embodiment 114, wherein the PEG has a weight average molecular weight of 1-3 kDa 116. The lipid nanoparticle of any of embodiments 111-114, wherein the sterol is cholesterol or a cholesterol-based lipid. 117. The lipid nanoparticle of any of embodiments 111-116, comprising: (i) cationic lipid of Structure A; (ii) cholesterol; (iii) 2-[(polyethylene glycol)-2000]-N,N- ditetradecylacetamide; and (iv) 1,2-distearoyl-sn-glycero-3-phosphocholine; preferably wherein said LNP encapsulates RNA according to SEQ ID NO: 104. Docket No.: 70348WO01   118. The lipid nanoparticle of embodiment 117, comprising (in mole %): (i) 30-60% cationic lipid of Structure A, such as 35-55%, or preferably 40-50%, 44-48%, 45-47%, about 46.2% or 46.2%; (ii) 35-70% cholesterol, such as 40-55%, or preferably 40-49%, 41-45%, 42-44%, about 42.6%, or 42.6%; (iii) 0.8-4.0% 2-[(polyethylene glycol)-2000]-N,N- ditetradecylacetamide, such as 0.8-3.5%, or preferably 1.0-3.0%, 1.6-2.0%, 1.7-1.9%, about 1.8%, or 1.8%; and (iv) 0-15% 1,2-distearoyl-sn-glycero-3-phosphocholine, such as 6.0- 12.0% or preferably 8.0-11.0%, 9.0-10.0%, about 9.4%, or 9.4%; preferably wherein said LNP encapsulates RNA according to SEQ ID NO: 104. 119. The lipid nanoparticle of any of embodiments 111-116, comprising (in mole %) 30- 60% cationic lipid, 35-70% sterol, 0.8-4.0% polymer-conjugated lipid, and 0-15% neutral lipid; optionally 40-50% cationic lipid, 41-49% sterol, 1.0-3.0% polymer-conjugated lipid and 8.0-11.0% neutral lipid. 120. A pharmaceutical composition comprising the RSV-F protein of any of embodiments 1-84, trimer of any of embodiments 85-90, nucleic acid of any of embodiments 91-108, or carrier of any of embodiments 109-119; optionally comprising a pharmaceutically acceptable excipient; optionally further comprising an adjuvant. 121. A vaccine composition comprising the RSV-F protein of any of embodiments 1-84, trimer of any of embodiments 85-90, nucleic acid of any of embodiments 91-108, or carrier of any of embodiments 109-119; optionally comprising a pharmaceutically acceptable excipient; optionally further comprising an adjuvant. 122. The composition of embodiment 120 or 121, comprising (i) a first plurality of RSV-F proteins of any of embodiments 1-84 and / or trimers of any of embodiments 85-90, wherein the RSV-F proteins and / or trimers are of the A subtype; and (ii) a second plurality of RSV-F proteins of any of embodiments 1-84 and / or trimers of any of embodiments 85-90, wherein the RSV-F proteins and / or trimers are of the B subtype. 123. The composition of embodiment 120 or 121, comprising (i) a first plurality of nucleic acids of any of embodiments 91-108 and / or carriers of any of embodiments 109-119, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the A subtype; and (ii) a second plurality of nucleic acids of any of embodiments 91-108 and / or carriers of any of embodiments 109-119, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the B subtype. 124. The composition of any of embodiments 120-123, for use in medicine. 125. The composition for use of embodiment 124, for use in a method of raising an immune response in a subject; optionally a protective immune response in a subject. Docket No.: 70348WO01 126. The composition for use of embodiment 124 or 125, for use in the treatment or prevention of RSV. 127. The composition for use of embodiment 126, for use in a method of vaccinating a subject against RSV; optionally wherein the vaccination is prophylactic. 128. The composition for use of any of embodiments 125- 127, wherein the subject is a human infant; optionally 2-6 months old. 129. The composition for use of any of embodiments 125- 127, wherein the subject is a human older adult; optionally ≥50 or ≥60 years old. 130. The composition for use of any of embodiments 125-127, wherein the subject is a pregnant human female; optionally ≥28 weeks pregnant. 131. A method of inducing an immune response against RSV in a subject, comprising administering to the subject an immunologically effective amount of the RSV-F protein of any of embodiments 1-84, trimer of any of embodiments 85-90, nucleic acid of any of embodiments 91-108, carrier of any of embodiments 109-119, pharmaceutical composition of embodiment 120, or vaccine composition of embodiment 121. 132. Use of the RSV-F protein of any of any of embodiments the RSV-F protein of any of embodiments 1-84, trimer of any of embodiments 85-90, nucleic acid of any of embodiments 91-108, or carrier of any of embodiments 109-119, in the manufacture of a medicament. 133. Use according to embodiment 132, wherein the medicament is for treating or preventing RSV. 134. Use according to embodiment 133, wherein the medicament is a vaccine; optionally a prophylactic vaccine. 135. The composition for use of any of embodiments 125-130, method of embodiment 131, or use of any of embodiments 132-134, wherein the subject is administered a first plurality of RSV-F proteins of any of embodiments 1-84 and / or trimers of any of embodiments 85-90, wherein the RSV-F proteins and / or trimers are of the A subtype; and (ii) a second plurality of RSV-F proteins of any of embodiments 1-84 and / or trimers of any of embodiments 85-90, wherein the RSV-F proteins and / or trimers are of the B subtype; wherein the first plurality and second plurality are administered simultaneously, separately or sequentially to one another. 136. The composition for use of any of embodiments 125-130, method of embodiment 131, or use of any of embodiments 132-134, wherein the subject is administered (i) a first plurality of nucleic acids of any of embodiments 91-108 and / or carriers of any of embodiments 109-119, wherein the nucleic acids encode, and / or the carriers comprise nucleic Docket No.: 70348WO01 acids encoding, an RSV-F protein of the A subtype; and (ii) a second plurality of nucleic acids of any of embodiments 91-108 and / or carriers of any of embodiments 109-119, wherein the nucleic acids encode, and / or the carriers comprise nucleic acids encoding, an RSV-F protein of the B subtype; wherein the first plurality and second plurality are administered simultaneously, separately or sequentially to one another. 137. A kit comprising the RSV-F protein of any of embodiments the RSV-F protein of any of embodiments 1-84, trimer of any of embodiments 85-90, nucleic acid of any of embodiments 91-108, carrier of any of embodiments 109-119, pharmaceutical composition of embodiment 120, or vaccine of embodiment 121, and instructions for use. 138. A recombinant ribonucleic acid (RNA) encoding a respiratory syncytial virus fusion (RSV-F) protein, comprising, in the 5’ to 3’ direction: a 5’ cap, a 5’ untranslated region (UTR), an open reading frame encoding the RSV-F protein, a 3’UTR, and a 3’ poly-adenine (poly-A) tail; wherein the RNA has a guanine-cytosine (GC) content of 30-70%; wherein the encoded RSV-F protein comprises at least two mutations relative to SEQ ID NO: 1 or 3 within a region of the protein corresponding to positions 474-523 of SEQ ID NO: 1 or 3; wherein the at least two mutations introduce, through substitution or insertion, a pair of C residues into the region; and wherein, when the encoded RSV-F protein is expressed, the pair of C residues form a disulphide bond. 139. The RNA of embodiment 138, wherein, when expressed, the encoded RSV-F protein is in the pre-fusion confirmation. 140. The RNA of embodiment 138 or 139, wherein the encoded RSV-F protein comprises one or more further substitutions, optionally at least 2, 3, 4, 5, 6 or 7 further substitutions. 141. The RNA of embodiment of embodiment 140, wherein the substitutions stabilise and / or promote the pre-fusion conformation of RSV-F. 142. An RSV-F protein in the pre-fusion conformation, comprising at least two mutations relative to SEQ ID NO: 1 or 3 within a region of the protein corresponding to positions 474- 523 of SEQ ID NO: 1 or 3; wherein the at least two mutations introduce, through substitution or insertion, a pair of C residues into the region, which form a disulphide bond; and wherein the RSV-F protein further comprises, relative to SEQ ID NO: 1 or 3: Docket No.: 70348WO01 (i) a substitution at position 228 for K, R or Q, and / or a substitution at position 232 for N; (ii) a substitution at position 55 for T, C, V, I or F; and / or (iii) a substitution at position 215 for A, P, V, I, or F. 143. The RNA or RSV-F protein of any of embodiments 138-142, wherein the disulphide bond is an intra-protomer disulphide bond. 144. The RNA or RSV-F protein of any of embodiments 138-143, wherein a first C residue of said pair is within a region of the encoded RSV-F protein or the RSV-F protein corresponding to positions 480-486 of SEQ ID NO: 1 or 3. 145. The RNA or RSV-F protein of any of embodiments 138-144, wherein a second C residue of said pair is within a region of the encoded RSV-F protein or the RSV-F protein corresponding to positions 490-497 of SEQ ID NO: 1 or 3. 146. The RNA or RSV-F protein of embodiment 144 or 145, wherein the pair of C residues is at positions 486 and 490, 485 and 494, or 480 and 497 of SEQ ID NO: 1 or 3. 147. The RNA or RSV-F protein of embodiment 146, wherein the pair of C residues is at positions 486 and 490 of SEQ ID NO: 1 or 3. 148. The RNA or RSV-F protein of any of embodiments 138-147, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises, relative to SEQ ID NO: 1 or 3, a substitution at position 228 for K, R or Q, optionally K or R, optionally K. 149. The RNA or RSV-F protein of any of embodiments 138-148, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises, relative to SEQ ID NO: 1 or 3, a substitution at position 55 for T, C, V, I or F, optionally T, C or V, optionally T or C, optionally T. 150. The RNA or RSV-F protein of any of embodiments 138-149, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises, relative to SEQ ID NO: 1 or 3, a substitution at position 215 for A, P, V, I, or F; optionally A or P; optionally A. 151. The RNA or RSV-F protein of any of embodiments 138-150, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises, relative to SEQ ID NO: 1 or 3, a substitution at position 228 for K, a substitution at position 55 for T, and a substitution at position 215 A. 152. The RNA or RSV-F protein of any of embodiments 138-151, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises, relative to SEQ ID NO: 1 or 3: Docket No.: 70348WO01 a substitution at position 55 for T, a substitution at position 152 for R, a substitution at position 215 for A, a substitution at position 228 for K, a substitution at position 315 for I, a substitution at position 346 for Q, a substitution at position 445 for D, a substitution at position 455 for V, a substitution at position 459 for M, a substitution at position 486 for C, and a substitution at position 490 for C. 153. The RSV-F protein of any of embodiments 142-152, comprising a heterologous trimerisation domain on the C-terminus thereof and / or C-terminal to the F1 domain, optionally wherein the heterologous trimerisation domain is a T4 fibritin foldon domain, optionally according to SEQ ID NO: 19. 154. The RNA or RSV-F protein of any of embodiments 138-152, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises a cytoplasmic tail; wherein, relative to a cytoplasmic tail according to SEQ ID NO: 5 or 6, 16-20, such as 17-20, 18-20, 19-20 or 20 residues are deleted from the C-terminal end of the cytoplasmic tail. 155. The RNA or RSV-F protein of any of embodiments 138-150, wherein the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1- 5 of SEQ ID NO: 5 or 6, or (ii) an amino acid sequence at least 60% or 80% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii). 156. The RNA or RSV-F protein of any of embodiments 138-155, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises: an F2 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to positions 26-109 of SEQ ID NO: 1; and an F1 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%, sequence identity Docket No.: 70348WO01 to positions 137-523 or 137-513 of SEQ ID NO: 1; optionally wherein the RSV-F protein is of the A subtype. 157. The RNA or RSV-F protein of any of embodiments 138-155, wherein the encoded RSV-F protein or wherein the RSV-F protein comprises: an F2 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to positions 1-109 of SEQ ID NO: 3; and an F1 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%, sequence identity to positions 137-523 or 137-513 of SEQ ID NO: 3; optionally wherein the RSV-F protein is of the B subtype. 158. A nucleic acid encoding the RSV-F protein of any of embodiments 142-157; optionally wherein the nucleic acid is RNA. 159. The RNA of any of embodiments 138-141, 143-152 or 154-158, having a GC content of 40-70% or 45-70%. 160. The RNA of any of embodiments 138-141, 143-152 or 155-159, comprising or consisting of (i) SEQ ID NO: 82, 104, 68, 56, 46, 86 or 72; or (ii) an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to any of SEQ ID NO: 82, 104, 68, 56, 46, 86 or 72. 161. A lipid nanoparticle comprising the RNA of any of embodiments 138-141, 143-152 or 155-160. 162. A pharmaceutical composition comprising the RSV-F protein of any of embodiments 142-157, nucleic acid of embodiment 158, RNA of any of embodiments 138-141, 143-152 or 155-160 or lipid nanoparticle of embodiment 161; optionally for use in medicine. 163. The composition for use of embodiment 162, for use in a method of vaccinating a subject against RSV; optionally wherein the subject is: a human infant; optionally 2-6 months old; a human older adult; optionally ≥50 or ≥60 years old; or a pregnant human female; optionally ≥28 weeks pregnant 164. A method of inducing an immune response against RSV in a subject, comprising administering to the subject an immunologically effective amount of the RSV-F protein of any of embodiments 142-157, nucleic acid of embodiment 158, RNA of any of embodiments 138-141, 143-152 or 155-160 or lipid nanoparticle of embodiment 161. Docket No.: 70348WO01 EXAMPLES Many modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, a skilled person in the art would recognise that the invention may be practiced otherwise than as specifically described. The illustrative embodiments and examples should not be construed as limiting the invention. Materials & Methods Expression and Purification of RSV-F Mutants, DS-Cav1 and RSV-F mAbs (Examples 1, 2, 7 and 13) RSV-F mutants were synthesized (GENEWIZ / AZENTA) and cloned into a CMV-based vector with a C-terminal thrombin-cleavable double Strep tag II tag followed by a 6x His-tag. DS-Cav1, F(i), F(ii), and RSV-F mutants were transiently expressed in Expi293 F cells (THERMO FISHER SCIENTIFIC). Media was harvested after 4 days, and purified using affinity chromatography, either nickel affinity or strep-tag affinity. Briefly, for nickel affinity chromatography, cell harvest medium was passed over a HisTrap Excel column (CYTIVA) and eluted with a step gradient of imidazole. For strep-tag affinity, the harvest medium was buffer exchanged into 50 mM Tris pH 8, 300 mM NaCl, passed over a StrepTrap HP column (CYTIVA) and eluted with elution buffer (100 mM Tris pH 8, 150 mM NaCl, 1 mM EDTA and 2.5 mM desthiobiotin). This was followed by a final size exclusion chromatography polishing step. RSV-F antibodies, AM14, D25, Motavizumab, and RSB1, were transiently transfected in Expi293F cells (THERMO FISHER SCIENTIFIC) according to manufacturer’s instructions and media was harvested 6-7 days post transfection. The cell harvest media was passed over a MABSELECT SURE COLUMN (CYTIVA) and eluted with 0.1 M citrate pH 3 into 1 M Tris pH 9; buffer exchanged into 20 mM HEPES pH 7, 150 mM NaCl; followed by a final size exclusion chromatography step on a HILOAD 16 / 600 Superdex 30 pg column (CYTIVA) in 20 mM Hepes pH 7, 150 mM NaCl. Initial Quantitation and Antigenicity using Biolayer Interferometry (Examples 1, 2, 7 and 13) Quantitation experiments were performed on the un-purified cell harvest media of 6x His-tagged DS- Cav1, F(i), F(ii) and RSV-F mutants using the Octet Red 96 or 384 instrument (SARTORIUS). Purified DS-Cav1 diluted in EXPI293 expression media with 0.1% BSA, 0.05% Tween-20 was used to make a standard curve. BSA and Tween-20 were added to DS-Cav1, F(i), F(ii), and RSV-F mutants un- purified cell harvest media to a final concentration of 0.1% and 0.05%, respectively. 6x His-tagged purified DS-Cav1, F(i), F(ii), and RSV-F mutant un-purified cell harvest media was captured on HIS2 biosensors for 2 min and the capture level was recorded. The concentrations were determined using unweighted 4 parameter logistics curve fitting in the manufacturer’s analysis software (Data Analysis HT 12.2.1.18). Initial antigenicity experiment was performed on the un-purified cell harvest media of DS-Cav1, F(i), F(ii), and RSV-F mutants to determine binding to AM14, D25, Motavizumab, and RSB1 mAbs using Docket No.: 70348WO01 the OCTET Red 96 or 384 (SARTORIUS). mAbs were diluted to 8 µg / mL in 1xPBS with 0.1% BSA and 0.05% Tween-20. BSA and Tween-20 was added to DS-Cav1 and RSV-F mutant un-purified cell harvest media to a final concentration of 0.1% and 0.05%, respectively. AHC biosensors were regenerated in 10 mM Glycine pH 1.5 before and between experiments. AHC biosensors were washed in 1x PBS with 0.1% BSA and 0.05% Tween-20 for 30 sec, mAbs were loaded for 60 sec, and washed for 30 sec before capturing DS-Cav1, F(i), F(ii), or RSV-F mutants from the un-purified cell harvest media. Binding and dissociation of DS-Cav1, F(i), F(ii), and RSV-F mutants was measured for 180 sec each. The binding response of DS-Cav1 binding to each mAb was compared to the RSV-F mutants’ binding response to each mAb to determine yes or no binding. Rapid Stability Assay using Biolayer Interferometry (Examples 1, 2 and 7) The rapid stability assay was performed on un-purified cell harvest media of DS-Cav1, F(i), F(ii), and RSV-F mutants to determine binding to AM14 and D25 mAbs using the OCTET Red 96 or 384 (SARTORIUS). mAbs were diluted to 8 µg / mL in 1xPBS with 0.1% BSA and 0.05% Tween-20. DS- Cav1 and RSV-F mutant unpurified cell harvest media were incubated at 50 or 60°C for 0, 30, 60, or 120 min and diluted 1:1 with 1xPBS with 1% BSA and 0.05% Tween-20. AHC biosensors were regenerated in 10 mM Glycine pH 1.5 before and between experiments. AHC biosensors were washed in 1x PBS with 1% BSA and 0.05% Tween-20 for 30 sec, mAbs were loaded for 60 sec, and washed for 30 sec before capturing DS-Cav1, F(i), F(ii), or RSV-F mutants from the unpurified cell harvest media. Binding and dissociation of DS-Cav1, F(i), F(ii), and RSV-F mutants was measured for 180 sec each. The blank subtracted binding response was normalized to the time 0 response and plotted in EXCEL. Thermostability using nanoDSF (Examples 1, 2 and 13) Thermostability experiments were performed in duplicate on a PROMETHEUS NT.48 instrument (NANOTEMPER TECHNOLOGIES). Capillaries were filled with 10 µL of DS-Cav1, F(i), F(ii), and RSV-F mutants, placed in the sample holder, and the temperature was increased from 25 to 95°C at a ramp rate of 1°C / min. The reported ratio of the recorded emission intensities (Em350 nm / Em330 nm) and its first derivative was calculated with the manufacturer’s software (PR.ThermControl v2.1.1) to determine melting temperatures. Binding Kinetics using BIACORE (Example 2 and 13) Single cycle kinetics experiments were performed in duplicate on a BIACORE 8K+ (CYTIVA) using a ligand capture method at 25°C. HBS-EP+ was used as both a running buffer and sample diluent. A blank run of buffer as the ligand was followed by runs with IgGs captured to 100-200 RUs in flow cell 2 on a Protein A chip, leaving flow cell 1 as a reference. DS-Cav1, F(i), F(ii), and RSV-F mutants were injected in both flow cells at 30 µL / min for 120 sec followed by 2400 sec dissociation. Antigen concentrations ranged from 0-10 nM. Reference- and blank-subtracted sensograms were fitted using a 1:1 binding model to calculate kon, koff, and KD. Docket No.: 70348WO01 Rapid Stability Assay (BIACORE) (Example 2 and 13) The rapid stability assay was performed in duplicate on a BIACORE 8K+ (CYTIVA) using a ligand capture method at 25°C. HBS-EP+ was used as both a running buffer and sample diluent. A blank run of buffer as the ligand was followed by runs with 10 µg / mL IgGs captured in flow cell 2 on a Protein A chip, leaving flow cell 1 as a reference. 5 µg / mL DS-Cav1 and PreF mutants, incubated at 50 or 60°C for 0, 30, 60, or 120 min, were injected in both flow cells at 10 µL / min for 120 sec followed by 60 sec dissociation. The relative analyte stability early response from blank subtracted sensograms was normalized to the time 0 response and plotted in EXCEL. Cryo-EM sample preparation and data collection of the F528:AM14 Fab complex (Example 3) ~10 µg F528 was mixed with 1:3.5 ratio excess AM14 Fab with a final concentration of 0.4 mg / ml and incubated at 4°C for 2hrs. Prior to sample loading, QUANTIFOIL Cu 300 mesh grids (AGAR SCIENTIFIC) were glow discharged (PELCO EASIGLOW) for 60s at 25 mA. 3.0 µl of complex mixture was applied to the grid and incubated on the grid for 10 sec at 10°C and ~99% relative humidity using a LEICA EM GP2 Plunge Freezer (LEICA MICROSYSTEMS). The grid was then plunged into liquid ethane at liquid nitrogen temperature after blotting for 3.5 sec. The grid was then transferred into a GLACIOS cryo-transmission electron microscope (THERMOFISHER SCIENTIFIC) equipped with a FALCON 3EC direct electron detector for data collection. A total of 5,139 micrographs were collected using EPU data collection software at 0.87 Å / pixel with a total dose of 38.25 e- / Å2. Defocus targets cycled from -0.8 to -1.8 microns. Cryo-EM Image Processing and Model Building of the F528:AM14 Fab complex (Example 3) The collected micrographs were processed by CRYOSPARC (v4.0.3) single particle analysis software platform (STRUCTURA BIOTECHNOLOGY INC.). A total of 817,845 particles were picked by using blob picker, which were subjected to 2D classification resulting in the selection of 199,514 particles for further processing. Following Ab-initio model building and a single round of heterogeneous refinement, 101,115 particles were selected for non-uniform refinement, which resulted a 4.07 Å resolution map when C3 symmetry is applied, and a 5.1 Å resolution map when no symmetry is applied. The map resolution was estimated using the Fourier shell correlation at 0.143 as the criterion. The first map was used to build the structural model which was iteratively refined using COOT

[0030] and PHENIX

[0031] . The obtained structure was fitted into the 5.1 Å resolution map to verify the presence of intra-protomer disulphide bonds within all three protomers. Structures were visualized and analyzed using UCSF CHIMERAX

[0032] . Cryo-EM sample preparation and data collection of the F647:RSB1 Fab complex (Example 3) Complex was formed by mixing ~5 µg of F647 trimer with 1:3.5 ratio excess RSB1 Fab with a final concentration of 0.4 mg / ml and incubated at 4°C for 2hrs. Prior to sample loading, the QUANTIFOIL Cu 300 mesh grids (AGAR SCIENTIFIC) were glow discharged (PELCO EASIGLOW) for 60s at 25 mA. 3.0µl of complex mixture was applied to the grid and incubated on the grid for 10s at 10°C and ~95% relative humidity using a VITROBLOT VP3 Plunge Freezer. The grid was then plunged into Docket No.: 70348WO01 liquid ethane after blotting for 4.0s. The grid was then transferred into a GLACIOS cryo-transmission electron microscope (THERMOFISHER SCIENTIFIC) equipped with Falcon 3EC direct electron detector for data collections. A total of 3,470 micrographs were collected FALCON the EPU data collection software at 0.87 Å / pixel with a total dose of 38.25 e- / Å2. Defocus targets cycled from -0.8 to -1.8 microns. Cryo-EM Image Processing and Model Building of the F647:RSB1 complex (Example 3) The collected data was processed in CRYOSPARC V4.0.3 (STRUCTURA BIOTECHNOLOGY INC.). A total of 680,164 particles were picked by using blob picker, which were subjected to 2D classification resulting in the selection of 162,493 particles. Following Ab-initio model building and one round of heterogeneous refinement, 137,515 particles were selected for non-uniform refinement, which resulted in a 3.47 Å resolution map when C3 symmetry is applied. This class was subjected to one more round of Ab-initio model building and 81,943 particles were selected for the final refinement, which then resulted in a map with a global resolution of 3.36 Å, which was estimated using the Fourier shell correlation at 0.143 as the criterion. Structure model building and refinement was performed iteratively using COOT

[0030] and PHENIX

[0031] . UCSF ChimeraX

[0032] was used for structural visualization and analysis. Cryo-EM sample preparation and data collection of the F651:AM14 Fab complex (Example 12) Complex was formed by mixing ~5 µg of F647 trimer with 1:3.5 ratio excess AM14 Fab with a final concentration of 0.4 mg / ml and incubated at 4°C for 2hrs. Prior to sample loading, the QUANTIFOIL Cu 300 mesh grids (AGAR SCIENTIFIC) were glow discharged (PELCO EASIGLOW) for 60s at 25 mA. 3.0µl of complex mixture was applied to the grid and incubated on the grid for 10s at 10°C and ~95% relative humidity using a Leica Em GP2 Plunge Freezer. The grid was then plunged into liquid ethane after blotting for 3.5s. The grid was then transferred into a GLACIOS cryo-transmission electron microscope (THERMOFISHER SCIENTIFIC) equipped with Falcon 3EC direct electron detector for data collections. A total of 5,620 micrographs were collected FALCON the EPU data collection software at 0.87 Å / pixel with a total dose of 38.25 e- / Å2. Defocus targets cycled from -0.8 to -1.8 microns. Cryo-EM Image Processing and Model Building of the F651:AM14 complex (Example 12) The collected data was processed in CRYOSPARC V4.0.3 (STRUCTURA BIOTECHNOLOGY INC.). A total of 1,430,870 particles were picked by using template picker, which were subjected to 2D classification resulting in the selection of 272,978 particles. Following Ab-initio model building and one round of heterogeneous refinement, 72,775 particles were selected for non-uniform refinement, which resulted in a 3.55 Å resolution map, which was estimated using the Fourier shell correlation at 0.143 as the criterion. Structure model building and refinement was performed iteratively using COOT

[0030] and PHENIX

[0031] . UCSF ChimeraX

[0032] was used for structural visualization and analysis. Docket No.: 70348WO01 Cryo-EM sample preparation and data collection of the 2ndGen DS-Cav1:VHH-L66 nanobody complex (Example 12) Complex was formed by mixing ~5 µg of 2ndGen DS-Cav1 trimer with 1:3.5 ratio excess VHH-L66 nanobody with a final concentration of 0.4 mg / ml and incubated at 4°C for 2hrs. Prior to sample loading, the QUANTIFOIL Cu 300 mesh grids (AGAR SCIENTIFIC) were glow discharged (PELCO EASIGLOW) for 60s at 25 mA. 3.0µl of complex mixture was applied to the grid and incubated on the grid for 10s at 10°C and ~95% relative humidity using a Leica Em GP2 Plunge Freezer. The grid was then plunged into liquid ethane after blotting for 3.5s. The grid was then transferred into a GLACIOS cryo-transmission electron microscope (THERMOFISHER SCIENTIFIC) equipped with Falcon 4i direct electron detector for data collections. A total of 6,001 micrographs were collected FALCON the EPU data collection software at 0.93 Å / pixel with a total dose of 40.12 e- / Å2. Defocus targets cycled from -0.6 to -1.8 microns. Cryo-EM Image Processing and Model Building of the 2ndGen DS-Cav1: VHH-L66 complex (Example 12) The collected data was processed in CRYOSPARC V4.0.3 (STRUCTURA BIOTECHNOLOGY INC.). A total of 2,179,850 particles were picked by using template picker, which were subjected to 2D classification resulting in the selection of 273,7773 particles. Following Ab-initio model building and one round of heterogeneous refinement, 184,701 particles were selected for non-uniform refinement, which resulted in a 3.45 Å resolution map, which was estimated using the Fourier shell correlation at 0.143 as the criterion. Structure model building and refinement was performed iteratively using COOT

[0030] and PHENIX

[0031] . UCSF ChimeraX

[0032] was used for structural visualization and analysis. Cloning of specific RSV-F mutants from mRNA (Example 4) RSV-F wildtype (A2 subtype) protein sequence (SEQ ID NO: 1) was back-translated to a nucleic acid sequence using specific metrics for codon optimality. The DNA gBLOCKS (INTEGRATED DNA TECHNOLOGIES) were amplified by PCR, followed with introduction of restriction sites, then ligated into vector with a polyA tail. Table 1 – substitutions in mRNA-encoded protein designs tested in cell-based assay Designation mRNA construct Protein substitutions relative to wild- RSV-F design in Figures designation type 16-18 (x axis) and Ex 4 n / a All mRNAs encode RSV-F proteins n / a having these mutations relative to WT Docket No.: 70348WO01 (SEQ ID NO: 1). Further mutations in each RSV-F design are listed below. S55T, V152R, S215A, N228K, K315I, A346Q, K445D, T455V, V459M 1) KM112 (SEQ ID NO: S211N, S348N F217 (SEQ ID 43) NO: 22) 2) KM112d20 (SEQ ID S211N, S348N, Δ555-574 F217d20 (SEQ NO: 44) ID NO: 45) 3) KM211 (SEQ ID NO: S211N, S348N, D486C, A490C F528 (SEQ ID 46) NO: 47) 4) KM212 (SEQ ID NO: S211P, N216P, S348N, D486C, A490C R701 (SEQ ID 48) NO: 49) 5) KM213 (SEQ ID NO: S211N, S348N, D486C, A490C, 103- R702 (SEQ ID 50) 145SubsGS NO: 51) 6) KM214 (SEQ ID NO: S211N, S348N, D486C, A490C, 104- R703 (SEQ ID 52) 144SubsGS NO: 53) 7) KM215 (SEQ ID NO: S348N, D486C, A490C R704 (SEQ ID 54) NO: 55) 8) KM223 (SEQ ID NO: S211N, S348N, D486C, A490C, Δ555- F528d20 (SEQ 56) 574 ID NO: 57) 9) KM224 (SEQ ID NO: S211P, N216P, S348N, D486C, A490C, R701d20 (SEQ 58) Δ555-574 ID NO: 59) 10) KM225 (SEQ ID NO: S211N, S348N, D486C, A490C, Δ555- R702d20 (SEQ 60) 574, 103-145SubsGS ID NO: 61) 11) KM226 (SEQ ID NO: S211N, S348N, D486C, A490C, Δ555- R703d20 (SEQ 62) 574, 104-144SubsGS ID NO: 63) 12) KM227 (SEQ ID NO: S348N, D486C, A490C, Δ555-574 R704d20 (SEQ 64) ID NO: 65) 13) KM235 (SEQ ID NO: R712 (SEQ ID 66) NO: 67) Docket No.: 70348WO01 14) KM236 (SEQ ID NO: D486C, A490C R713 a.k.a 68) F647 (SEQ ID NO: 69) 15) KM237 (SEQ ID NO: S211P, N216P, D486C, A490C R714 (SEQ ID 70) NO: 71) 16) KM238 (SEQ ID NO: D486C, A490C, 103-145SubsGS R715 a.k.a 72) F651 (SEQ ID NO: 73) 17) KM239 (SEQ ID NO: D486C, A490C, 104-144SubsGS R716 (SEQ ID 74) NO: 75) 18) KM240 (SEQ ID NO: S211P, N216P, D486C, A490C, 103- R717 (SEQ ID 76) 145SubsGS NO: 77) 19) KM241 (SEQ ID NO: S211P, N216P, D486C, A490C, 104- R718 (SEQ ID 78) 144SubsGS NO: 79) 20) KM242 (SEQ ID NO: Δ555-574 R712d20 (SEQ 80) ID NO: 81) 21) KM243 (SEQ ID NO: D486C, A490C, Δ555-574 R713d20 a.k.a 82) F647d20 (SEQ ID NO: 83) 22) KM244 (SEQ ID S211P, N216P, D486C, A490C, Δ555- R714d20 (SEQ NO: 84) 574 ID NO: 85) 23) KM245 (SEQ ID NO: D486C, A490C, Δ555-574, 103- R715d20 a.k.a 86) 145SubsGS F651d20 (SEQ ID NO: 87) 24) KM246 (SEQ ID NO: D486C, A490C, Δ555-574, 104- R716d20 (SEQ 88) 144SubsGS ID NO: 89) 25) KM247 (SEQ ID NO: S211P, N216P, D486C, A490C, Δ555- R717d20 (SEQ 90) 574, 103-145SubsGS ID NO: 91) 26) KM248 (SEQ ID NO: S211P, N216P, D486C, A490C, Δ555- R718d20 (SEQ 92) 574, 104-144SubsGS ID NO: 93) Docket No.: 70348WO01 The C-terminal 20 amino acids (positions 555-574) of the cytoplasmic tail were selectively removed from these constructs to create ΔCT20 (aka “d20”) mutants, detailed above. Briefly, the ligation mixtures were transformed into competent cells (NEB C3040H) was carried out by following manufacture instructions.24 hours after, colonies were picked for sequencing validation to screen clones with correct sequences. The final plasmids of selected clones were validated by Sanger sequencing and purified to support mRNA production. In vitro transcription to generate mRNA for RSV-F variations (Example 4) The plasmids were linearized with the BspQ1 restriction enzyme (NEW ENGLAND BIOLABS) to produce the DNA templates for in vitro transcription. mRNAs were produced by in vitro transcription with capping analogue (TRILINK CLEANCAP A / G) and 100% uridine replacement (with 1mΨ), followed with DNase I and phosphatase treatments (NEW ENGLAND BIOLABS) and silica column purification (QIAGEN). Cell culture conditions (Example 4) Primary BJ cells (ATCC, CRL-2522) are maintained by routine passaging in growth media (DMEM (Lonza 12-614F) supplemented with 10% FBS (Corning 35-016-CV), antibiotic (Gibco 15140-122) and glutamine (Gibco 25030-081)) and grown at 37°C, 5% CO2. Forward transfection of candidate mRNAs (Example 4) BJ cells were seeded in growth media at 1.5x105cells / mL onto 96-well, clear-bottom, black-walled imaging microwell plates (PERKIN ELMER 6055302). The following day, target mRNAs were complexed with TRANSIT mRNA transfection reagent (MIRUS mir2250) in OPTIMEM (GIBCO 31985-070). Each target mRNA was forward transfected into BJ cell monolayers using 0.35% transfection reagent (final concentration) with mRNAs diluted to 0.454ng / uL (final con...

Claims

Docket No.: 70348WO01 CLAIMS 1. A respiratory syncytial virus F (RSV-F) protein, comprising at least two mutations relative to SEQ ID NO: 1 or 3 which introduce, through substitution or insertion, a pair of C residues which form a disulphide bond; wherein a first C residue of said pair is within a region of the RSV-F protein corresponding to positions 480-486 of SEQ ID NO: 1 or 3; wherein a second C residue of said pair is within a region of the RSV-F protein corresponding to positions 490-497 of SEQ ID NO: 1 or 3; and wherein the RSV-F protein does not comprise a deletion at position 137 relative to SEQ ID NO: 1 or 3.

2. The RSV-F protein of claim 1, which is in the pre-fusion conformation.

3. The RSV-F protein of claim 1 or 2, wherein the disulphide bond is an intra-protomer disulphide bond.

4. The RSV-F protein of any of claims 1-3, wherein the pair of C residues is at positions 486 and 490, 485 and 494, or 480 and 497.

5. The RSV-F protein of claim 12, wherein the pair of C residues is at positions 486 and 490.

6. The RSV-F protein of any preceding claim, comprising an aromatic residue at position 137; optionally F, W or Y; optionally F.

7. The RSV-F protein of any preceding claim, comprising an aromatic residue at position 488; optionally F, W or Y; optionally F.

8. The RSV-F protein of any preceding claim, comprising a positively charged residue at position 339; optionally K or R, optionally K.

9. The RSV-F protein of any preceding claim, comprising a substitution at position 228 for K, R or Q, optionally K or R, optionally K.

10. The RSV-F protein of any preceding claim, comprising a substitution at position 55 for T, C, V, I or F; optionally T, C or V; optionally T or C, optionally T.

11. The RSV-F protein of any preceding claim, comprising a substitution at position 215 for A, P, V, I, or F; optionally A or P; optionally A.

12. The RSV-F protein of claim 11, comprising a substitution at position 228 for K, a substitution at position 55 for T, and a substitution at position 215 A.

13. The RSV-F protein of claim 12, comprising:Docket No.: 70348WO01 a substitution at position 55 for T, a substitution at position 152 for R, a substitution at position 215 for A, a substitution at position 228 for K, a substitution at position 315 for I, a substitution at position 346 for Q, a substitution at position 445 for D, a substitution at position 455 for V, a substitution at position 459 for M, a substitution at position 486 for C, and a substitution at position 490 for C.

14. The RSV-F protein of any preceding claim, comprising a heterologous trimerisation domain on the C-terminus thereof and / or C-terminal to the F1 domain, optionally wherein the heterologous trimerisation domain is a T4 fibritin foldon domain, optionally according to SEQ ID NO:

19.

15. The RSV-F protein of any of claims 1-13, wherein the RSV-F protein comprises a cytoplasmic tail; and wherein, relative to a cytoplasmic tail according to SEQ ID NO: 5 or 6, 16-20, such as 17-20, 18-20, 19-20 or 20 residues are deleted from the C-terminal end of the cytoplasmic tail.

16. The RSV-F protein of claim 15, wherein the cytoplasmic tail comprises or consists of (i) an amino acid sequence according to positions 1-5 of SEQ ID NO: 5 or 6, or (ii) an amino acid sequence at least 60% or 80% identical to said positions and optionally the same length as said positions; and wherein the cytoplasmic tail does not comprise any residues C-terminal to the amino acid sequence of (i) or (ii).

17. The RSV-F protein of any preceding claim, comprising: an F2 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to positions 26-109 of SEQ ID NO: 1; and an F1 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%, sequence identity to positions 137-523 or 137-513 of SEQ ID NO: 1; optionally wherein the RSV-F protein is of the A subtype.Docket No.: 70348WO01 18. The RSV-F protein of any of claims 1-16, comprising: an F2 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to positions 1-109 of SEQ ID NO: 3; and an F1 domain comprising or consisting of an amino acid sequence having at least 80%, 81% 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%, sequence identity to positions 137-523 or 137-513 of SEQ ID NO: 3; optionally wherein the RSV-F protein is of the B subtype.

19. A nucleic acid encoding the RSV-F protein of any preceding claim.

20. The nucleic acid of claim 19, wherein the nucleic acid is RNA.

21. The RNA of claim 20, comprising, 5’ to 3’ direction: a 5’ cap, a 5’ untranslated region (UTR), an open reading frame encoding at least an RSV-F protein according to any of embodiments 1-18, a 3’UTR, and a 3’ poly-A tail.

22. The RNA of claim 20 or 21, comprising or consisting of (i) SEQ ID NO: 104, 128, 82, 68, 56, 46, 86 or 72; or (ii) an RNA sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or preferably 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.94% identical to any of SEQ ID NO: 104, 128, 82, 68, 56, 46, 86 or 72.

23. A lipid nanoparticle comprising the nucleic acid of claim 19 or RNA of any of claims 20-22.

24. A pharmaceutical composition comprising the RSV-F protein of any of claims 1-18, nucleic acid of claim 19, RNA of any of claims 20-22 or lipid nanoparticle of claim 23; optionally for use in medicine.

25. The composition for use of claim 24, for use in a method of vaccinating a subject against RSV; optionally wherein the subject is: a human infant; optionally 2-6 months old; a human older adult; optionally ≥50 or ≥60 years old; or a pregnant human female; optionally ≥28 weeks pregnant.

26. A method of inducing an immune response against RSV in a subject, comprising administering to the subject an immunologically effective amount of the RSV-F protein of any of claims 1-18, nucleic acid of claim 19, RNA of any of claims 20-22, lipid nanoparticle of claim 23, or pharmaceutical composition of claim 24.

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