Recombinant RSV f protein and use thereof

Abstract

Provided are a recombinant respiratory syncytial virus (RSV) fusion (F) protein, and a fusion protein, vaccine, immunogenic composition, kit and pharmaceutical composition comprising same. Further provided is a use of the recombinant RSV F protein, fusion protein, vaccine, immunogenic composition, kit and pharmaceutical composition in preventing and / or treating RSV infection or diseases and / or symptoms caused by RSV infection.

Description

Cross-Reference to Related Application The present application claims priority to Chinese Patent Application No. 202410361533.6 filed on March 27, 2024, and the entire contents of which are incorporated herein by reference in their entirety. Technical Field The present application relates to the field of biomedicine. Specifically, the present application relates to a recombinant respiratory syncytial virus (RSV) fusion (F) protein, as well as a fusion protein, a vaccine, an immunogenic composition, a kit, and a pharmaceutical composition comprising the same. The present application also relates to the use of the recombinant respiratory syncytial virus (RSV) fusion (F) protein, the fusion protein, the vaccine, the immunogenic composition, the kit, and the pharmaceutical composition for preventing and / or treating RSV infection or diseases and / or symptoms caused by RSV infection. Background Art Respiratory syncytial virus (RSV) is one of the most important pathogens causing lower respiratory tract infections in infants and young children worldwide. According to statistics, RSV infects 33 million children under 5 years of age globally each year, causing nearly 160,000 deaths. RSV infection does not confer lasting immunity, and reinfection can occur. More than 99% of children under 2 years of age have been infected with RSV at least once, and 70% of these patients are hospitalized with complications of bronchiolitis, pneumonia, and asthma. In addition to infants and children, elderly people with low immunity and immunocompromised individuals are also at high risk for RSV infection. In the elderly, RSV often leads to obstructive pulmonary disease accompanied by cardiopulmonary complications. Despite causing a serious disease and economic burden globally, there is currently no safe and effective vaccine against RSV. RSV belongs to the genus Pneumovirus and the family Pneumoviridae, and is an enveloped, single-stranded, negative-sense RNA virus. Its genome is approximately 15.2 kb in length and transcribes ten genes, encoding a total of eleven proteins. Among them, the attachment glycoprotein G and the membrane fusion protein F are located on the viral membrane surface. Compared to the G protein, the F protein has greater conservation and is therefore considered the most important protective antigen of RSV. RSV F protein belongs to type I integral membrane proteins. Its precursor protein F0 consists of 574 amino acids. Three F0 molecules form a trimer through hydrophobic interactions. During passage through the Golgi apparatus, it is cleaved by host furin protease between amino acids 109 and 110, and between amino acids 136 and 137. The cleaved F protein releases a short peptide, P27, consisting of 27 amino acids. The remaining two fragments, F2 and F1, are connected by two disulfide bonds to form the mature F protein, which is displayed on the cell membrane or virion surface via budding. At this stage, the F protein is in a high-energy metastable state, termed pre-F. At the N-terminus of F1 is a highly hydrophobic fusion peptide (FP), located within a hydrophobic cavity of the trimer. Upon triggering by currently unknown factors, the N-terminus of F1 undergoes a series of drastic structural changes. This process allows the FP to insert into the cell membrane, facilitating viral membrane fusion and enabling infection. It also drives the pre-F structure into a stable, low-energy post-F conformation. In comparison, the immune system generates stronger antibodies against the pre-F conformation of the protein. However, using the pre-F conformation as an antigen presents challenges, as its stability is difficult to maintain and it readily converts to the post-F conformation. In 2013, McLellan et al. first obtained a stabilized pre-F protein through point mutations, named DS-Cav1. Subsequently, several other pre-F proteins were reported, including DS-Cav1-Cys-zipper, SC-TM, SC-DM, and SC-TM. Compared to post-F proteins, these pre-F proteins were confirmed to elicit significantly higher levels of neutralizing antibody titers. The pre-F protein of RSV can be divided into two parts: a membrane-proximal "stalk" region, which includes domains I and II, primarily composed of P-strand structures and terminating in a C-terminal helix that enters the membrane; and, a membrane-distal portion, which is the RSV F "head" region, includes domain III and is mainly a-helical. The RSV F head contains at least two epitopes associated with neutralizing antibodies. Site 0 and site V are located at the apex of the pre-F trimer and can be recognized by potent neutralizing antibodies, including D25, AM22, 5C4, and hRSV90. Site II is located in the middle of the pre-F trimer and is the binding site for the commercial antibody palivizumab. Site I and site IV, recognized by low-potency antibodies, are located in the stalk region of the pre-F protein. The stalk region of the pre-F protein accounts for 55% of the total trimer surface area and may compete with the highly neutralizing epitopes site 0 or site II in the head region, leading to a weakened antibody response against these potent neutralizing epitopes. The primary goal of RSV vaccine research, using F protein as the main protective antigen, is to generate high-titer neutralizing antibodies. Improving the immunogenicity of RSV vaccines using F protein as the protective antigen is of great significance for RSV vaccine development. Contents of the Invention To address the issues encountered in RSV vaccine development, the present application provides a recombinant RSV F protein to enhance the stability and / or immunogenicity of the pre-fusion conformation of the F protein. Recombinant RSV F Protein Therefore, in a first aspect, the present application provides a recombinant respiratory syncytial virus (RSV) fusion (F) protein, comprising the F2 domain and F1 domain of a wild-type RSV F protein; and, compared to the wild-type RSV F protein, further comprising at least one amino acid mutation that stabilizes the pre-fusion (pre-F) conformation of the RSV F protein. In certain embodiments, the recombinant RSV F protein has increased stability compared to the wild-type RSV F protein. In certain embodiments, the stability is measured by the binding of the recombinant RSV F protein to antibody D25. In certain embodiments, the recombinant RSV F protein has a higher proportion of pre-F protein compared to the wild-type RSV F protein. In certain embodiments, the recombinant RSV F protein comprises pre-fusion conformation (pre-F) protein, post-fusion conformation (post-F) protein, or a mixture thereof. In certain embodiments, the proportion of pre-F protein is measured by the ratio of antibody D25 to antibody palivizumab bound to the recombinant RSV F protein. In certain embodiments, the recombinant RSV F protein has a higher protein expression level compared to the wild-type RSV F protein. Stabilizing Modifications The pre-fusion (pre-F) conformation of the RSV F protein is a soluble F protein. The recombinant RSV F protein of the present application stabilizes the pre-F conformation by introducing one or more modifications, such as insertion, deletion, and / or mutation of one or more amino acids. In certain embodiments, the recombinant RSV F protein retains at least one immunodominant epitope of the pre-fusion conformation of the F protein. A first type of stabilizing modification is the introduction of amino acid insertions, deletions, and / or mutations. Thus, in certain embodiments, the recombinant RSV F protein comprises an insertion, deletion, and / or mutation of one or more amino acids compared to the wild-type RSV F protein. In certain embodiments, the position of the amino acid mutation comprised in the recombinant RSV F protein is selected from any one or more of the following: positions corresponding to positions 35, 60, 79, 92, 189, 190, 227, 238, 298, 320, 326, 377, 405, 437, 481, and 496 of the wild-type RSV F protein. Another type of stabilizing modification is the elimination of a furin cleavage site and / or a pep27 domain. The furin cleavage site is located between the F2 and F1 domains in the F0 precursor protein. One or two furin cleavage sites can be eliminated by deleting or substituting one or more amino acids of the furin cleavage sites. In such embodiments, the F protein lacking the furin cleavage site can avoid being cleaved into its constituent domains, thereby maintaining stability. In certain embodiments, one furin cleavage site is located at amino acid residues 105-109 of the wild-type RSV F protein. In certain embodiments, another furin cleavage site is located at amino acid residues 133-136 of the wild-type RSV F protein. In certain embodiments, the sequence of the furin cleavage site can be replaced with a sequence (e.g., a linker). Thus, in certain embodiments, the recombinant RSV F protein lacks at least one furin cleavage site, or lacks one or more amino acids in a furin cleavage site, compared to the wild-type RSV F protein. Similarly, the pep27 domain is located between the F2 and F1 domains in the F0 precursor protein. The pep27 domain can be eliminated by deleting or substituting one or more amino acids of the pep27 domain. In certain embodiments, the pep27 domain is located at amino acid residues 110-136 of the wild-type RSV F protein. In certain embodiments, the recombinant RSV F protein lacks one or more (e.g., 1 to 5, 5 to 10, 10 to 15, 15 to 20, 20 to 27) amino acids of the pep27 domain compared to the wild-type RSV F protein. Wild-type RSV F Protein Natural RSV F proteins exhibit high sequence conservation among different RSV subtypes. For example, RSV subtypes A and B share 90% sequence identity. Furthermore, within the same RSV subtype, F protein sequence identity is even higher; within RSV subtype A or subtype B, RSV F proteins share about 98% sequence identity. Moreover, almost all identified RSV F protein sequences consist of 574 amino acids, with length variations typically only due to minor differences in the C-terminal cytoplasmic tail. The sequence identity among these natural RSV F proteins is known in the art (see, e.g., WO2014 / 160463). Given the sequence conservation of RSV F proteins, one of ordinary skill in the art can readily compare amino acid positions between different natural RSV F protein sequences to identify corresponding amino acid positions of RSV F proteins from different RSV strains or subtypes. For example, in almost all identified natural RSV F proteins, furin cleavage sites are located at identical amino acid positions. Therefore, the conservation of natural RSV F protein sequences among strains or subtypes allows them to serve as reference RSV F sequences to compare specific positions in RSV F proteins. As used herein, when referring to the amino acid sequence of a wild-type RSV F protein, it is described using the sequence as set forth in SEQ ID NO: 1, 2, or 64. For example, the expression "position 298 of the wild-type RSV F protein" refers to the 298th amino acid residue of the protein set forth in SEQ ID NO: 1, 2, or 64. However, those skilled in the art understand that wild-type RSV F proteins can have multiple versions that have substantially the same primary structure (i.e., amino acid sequence) and higher-order structure (i.e., three-dimensional structure), as well as substantially the same biological function, but minor differences in amino acid sequences may still exist between them. Therefore, in the present application, wild-type RSV F protein is not limited to the protein set forth in SEQ ID NO: 1, 2, or 64, but is intended to encompass all known wild-type RSV F proteins. Thus, in the present application, the term "wild-type RSV F protein" shall include various naturally occurring, biologically functional RSV F proteins, including, for example, the RSV F proteins set forth in SEQ ID NO: 1, 2, or 64, as well as naturally occurring variants thereof. Furthermore, when describing amino acid positions of an RSV F protein, it includes not only the specific amino acid positions in SEQ ID NO: 1, 2, or 64, but also the amino acid positions in naturally occurring variants thereof that correspond to the specific amino acid positions. For example, the expression "position 298 of the wild-type RSV F protein" includes the 298th amino acid residue of SEQ ID NO: 1, 2, or 64, as well as the corresponding amino acid position in naturally occurring variants thereof. According to the present application, the expression "corresponding amino acid position" refers to the amino acid position in the sequences being compared that is located at an equivalent position when the sequences are optimally aligned, i.e., when the sequences are aligned to obtain the highest percent identity. In certain embodiments, the wild-type RSV is a subtype A strain, a subtype B strain, or a strain derived from subtype A or subtype B. In certain embodiments, the wild-type RSV is selected from strain A2, strain Ontario, strain Buenos Aires, or strain B18537. In certain embodiments, the wild-type RSV F protein comprises a sequence selected from the following, or consists of a sequence selected from the following: (i) the sequence as set forth in SEQ ID NO: 1, 2, or 64; (ii) a sequence having substitution, deletion, and / or addition of one or more amino acids (e.g., substitution, deletion, and / or addition of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids) compared to the sequence as set forth in SEQ ID NO: 1, 2, or 64; (iii) a sequence having at least 90% (e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%) sequence identity to the sequence as set forth in SEQ ID NO: 1, 2, or 64. Amino Acid Mutations In certain embodiments, the recombinant RSV F protein comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more amino acid mutations compared to the wild-type RSV F protein. In certain embodiments, the position of the amino acid mutation comprised in the recombinant RSV F protein is selected from: positions corresponding to positions 35, 189, 190, 227, 238, or 298 of the wild-type RSV F protein. In certain embodiments, the position of the amino acid mutation comprised in the recombinant RSV F protein is a position corresponding to position 298 of the wild-type RSV F protein; and one or more positions selected from: positions corresponding to positions 60, 79, 92, 189, 190, 227, 238, 320, 326, 377, 405, 437, 481, and 496 of the wild-type RSV F protein. In certain embodiments, the amino acid at position corresponding to position 35 of the wild-type RSV F protein in the recombinant RSV F protein is Y or F. In certain embodiments, the amino acid mutation at position 35 in the recombinant RSV F protein is a S to Y or F mutation. In certain embodiments, the amino acid at position corresponding to position 298 of the wild-type RSV F protein in the recombinant RSV F protein is I, H, M, P, or L. In certain embodiments, the amino acid mutation at position 298 in the recombinant RSV F protein is an A to I, H, M, P, or L mutation. In certain embodiments, the amino acid at position corresponding to position 238 of the wild-type RSV F protein in the recombinant RSV F protein is L, I, T, or V. In certain embodiments, the amino acid mutation at position 238 in the recombinant RSV F protein is an S to L, I, T, or V mutation. In certain embodiments, the amino acid at position corresponding to position 189 of the wild-type RSV F protein in the recombinant RSV F protein is L, I, or V. In certain embodiments, the amino acid mutation at position 189 in the recombinant RSV F protein is a T to L, I, or V mutation. In certain embodiments, the amino acid at position corresponding to position 190 of the wild-type RSV F protein in the recombinant RSV F protein is I, L, M, V, or Y. In certain embodiments, the amino acid mutation at position 190 in the recombinant RSV F protein is an S to I, L, M, V, or Y mutation. In certain embodiments, the amino acid at position corresponding to position 227 of the wild-type RSV F protein in the recombinant RSV F protein is L. In certain embodiments, the amino acid mutation at position 227 in the recombinant RSV F protein is an N to L mutation. In certain embodiments, the amino acid at position corresponding to position 320 of the wild-type RSV F protein in the recombinant RSV F protein is A, F, H, I, K, L, M, N, Q, R, S, T, V, W, or Y. In certain embodiments, the amino acid mutation at position 320 in the recombinant RSV F protein is a P to A, F, H, I, K, L, M, N, Q, R, S, T, V, W, or Y mutation. In certain embodiments, the amino acid at position corresponding to position 326 of the wild-type RSV F protein in the recombinant RSV F protein is D, E, or P. In certain embodiments, the amino acid mutation at position 326 in the recombinant RSV F protein is a T to D, E, or P mutation. In certain embodiments, the amino acid at position corresponding to position 377 of the wild-type RSV F protein in the recombinant RSV F protein is P or Q. In certain embodiments, the amino acid mutation at position 377 in the recombinant RSV F protein is an S to P or Q mutation. In certain embodiments, the amino acid at position corresponding to position 405 of the wild-type RSV F protein in the recombinant RSV F protein is V. In certain embodiments, the amino acid mutation at position 405 in the recombinant RSV F protein is an S to V mutation. In certain embodiments, the amino acid at position corresponding to position 60 of the wild-type RSV F protein in the recombinant RSV F protein is F or Y. In certain embodiments, the amino acid mutation at position 60 in the recombinant RSV F protein is an E to F or Y mutation. In certain embodiments, the amino acid at position corresponding to position 437 of the wild-type RSV F protein in the recombinant RSV F protein is R or Y. In certain embodiments, the amino acid mutation at position 437 in the recombinant RSV F protein is an N to R or Y mutation. In certain embodiments, the amino acid at position corresponding to position 481 of the wild-type RSV F protein in the recombinant RSV F protein is R. In certain embodiments, the amino acid mutation at position 481 in the recombinant RSV F protein is an L to R mutation. In certain embodiments, the amino acid at position corresponding to position 496 of the wild-type RSV F protein in the recombinant RSV F protein is F or Y. In certain embodiments, the amino acid mutation at position 496 in the recombinant RSV F protein is an N to F or Y mutation. In certain embodiments, the amino acid at position corresponding to position 92 of the wild-type RSV F protein in the recombinant RSV F protein is T, V, M, or I. In certain embodiments, the amino acid mutation at position 92 in the recombinant RSV F protein is an E to T, V, M, or I mutation. In certain embodiments, the amino acid at position corresponding to position 79 of the wild-type RSV F protein in the recombinant RSV F protein is L. In certain embodiments, the amino acid mutation at position 79 in the recombinant RSV F protein is an I to L mutation. F2 Domain and F1 Domain The F1 domain of the recombinant RSV F protein of the present application may have the same length as the full-length F1 domain of the wild-type RSV F protein. It is understood that it may also comprise a fragment of the full-length F1 domain of the RSV F protein, as long as the stabilized pre-F conformation is maintained. For example, the F1 domain of the recombinant RSV F protein may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or up to 60 amino acid residues deleted from the C-terminus of the full-length F1 domain, or may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or up to 60 amino acid residues deleted from the N-terminus of the full-length F1 domain. In certain embodiments, the full-length F1 domain of the RSV F protein corresponds to positions 137-574 of the wild-type RSV F protein and comprises (from N-terminus to C-terminus) the ectodomain (ED) (positions 137-524), the transmembrane domain (TM) (positions 525-550), and the cytoplasmic tail (CT) (positions 551-574). In certain embodiments, the F1 domain of the recombinant RSV F protein of the present application lacks all or part of the cytoplasmic tail. In other embodiments, the F1 domain of the recombinant RSV F protein lacks the cytoplasmic tail and all or part of the transmembrane domain. Typically, for recombinant RSV F proteins intended to be linked to a multimerization domain (i.e., foldon), all or part of amino acid residues 514 to 574 may be deleted. Thus, in some specific embodiments, the F1 domain of the recombinant RSV F protein does not comprise the transmembrane domain and / or cytoplasmic tail of the wild-type RSV F protein. In some specific embodiments, the F1 domain of the recombinant RSV F protein does not comprise amino acid residues 514 to 574 of the wild-type RSV F protein. Similarly, the F2 domain of the recombinant RSV F protein of the present application may have the same length as the full-length F2 domain of the wild-type RSV F protein. It is understood that it may also comprise a fragment of the full-length F2 domain of the RSV F protein, as long as the stabilized pre-F conformation is maintained. For example, the F2 domain of the recombinant RSV F protein may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or up to 30 amino acid residues deleted from the C-terminus of the full-length F2 domain. Alternatively, it may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or up to 30 amino acid residues deleted from the N-terminus of the full-length F2 domain. In certain embodiments, the full-length F2 domain of the RSV F protein corresponds to positions 1-109 of the wild-type RSV F protein. In certain embodiments, there is no furin cleavage site and / or pep27 domain between the F2 domain and the F1 domain. In certain embodiments, the F2 domain comprises the complete F2 domain of a wild-type RSV F protein (e.g., a portion corresponding to positions 1-109 of the wild-type RSV F protein) or a fragment thereof. In certain embodiments, the F2 domain comprises a portion corresponding to positions 1-95, 5-95, 10-95, 1-100, 5-100, 10-100, 1-105, 5-105, 10-105, 1-110, 5-110, or 10-110 of the wild-type RSV F protein. In certain embodiments, the F2 domain comprises a portion corresponding to positions 1-105 of the wild-type RSV F protein. In certain embodiments, the F2 domain has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more amino acid residues deleted from the N-terminus and / or C-terminus compared to the F2 domain of the wild-type RSV F protein. In certain embodiments, the F2 domain has 5 or 25 amino acids deleted from the N-terminus and 4 amino acids deleted from the C-terminus compared to the F2 domain of the wild-type RSV F protein. In certain embodiments, the F1 domain comprises the complete F1 domain of a wild-type RSV F protein (e.g., a portion corresponding to positions 137-574 of the wild-type RSV F protein) or a fragment thereof. In certain embodiments, the F1 domain comprises the ectodomain, transmembrane domain, and / or cytoplasmic tail of the wild-type RSV F protein. In certain embodiments, the F1 domain comprises a portion corresponding to positions 135-503, 140-503, 145-503, 135-508, 140-508, 145-508, 135-513, 140-513, 145-513, 135-518, 140-518, or 145-518 of the wild-type RSV F protein. In certain embodiments, the F1 domain comprises a portion corresponding to positions 145-513 of the wild-type RSV F protein. In certain embodiments, the F1 domain has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more (e.g., 30-50, 50-100, 100-150, 150-200, 200-250, 250-300) amino acid residues deleted from the N-terminus and / or C-terminus compared to the F1 domain of the wild-type RSV F protein. In certain embodiments, the F1 domain has 8 amino acids deleted from the N-terminus and 252 or 268 amino acids deleted from the C-terminus compared to the F1 domain of the wild-type RSV F protein. Linker The F2 domain and F1 domain as described above may be connected via a disulfide bond, or via a peptide bond or a linker. The linker of the present application can be any suitable linker that joins two polypeptide chains. Specific sequences of such linkers include, but are not limited to, G, GG, GGG, GS, SAIG, GGPG, GPGGG, GGGPG, EAAAK, and PAAAK. Thus, in certain embodiments, the recombinant RSV F protein further comprises a linker. In certain embodiments, the linker is located at the C-terminus of the F2 domain. In certain embodiments, the linker is located at the N-terminus of the F1 domain. In certain embodiments, the linker has 3 to 20 (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 15, 20) amino acids. In certain embodiments, the linker comprises at least 1 (e.g., 1, 2, 3, 4, 5, 6, 7) glycine. In certain embodiments, the linker further comprises at least 1 (e.g., 1, 2, 3) proline. In certain embodiments, the linker comprises a sequence selected from the following, or consists of a sequence selected from the following: the sequence as set forth in any one of SEQ ID NOs: 54-59. Fusion Protein In a second aspect, the present application provides a fusion protein, which comprises the recombinant RSV F protein according to the first aspect, wherein the fusion protein further comprises an additional protein or polypeptide. It is understood that these additional proteins or polypeptides will not adversely affect the activity and / or function of the recombinant RSV F protein. In certain embodiments, the additional protein or polypeptide is selected from: a signal peptide, a multimerization domain, a tag, or any combination thereof. Signal Peptide To enhance protein production or secretion, the fusion protein of the present application may comprise a signal peptide. In certain embodiments, the signal peptide is a native RSV signal peptide or a variant thereof, or a native signal peptide derived from another organism or a variant thereof. In certain embodiments, the signal peptide is located at one end (e.g., the N-terminus) of the fusion protein. In certain embodiments, the signal peptide is located at the N-terminus of the F2 domain. In certain embodiments, the signal peptide is linked to the F2 domain with or without a first linking peptide. Multimerization Domain The recombinant RSV F protein provided in the present application can be linked to a multimerization domain to promote the formation of a multimer (e.g., dimer, trimer, tetramer, pentamer) of the recombinant RSV F protein. Exogenous multimerization domains capable of promoting the formation of stable multimers of soluble proteins are known in the art. Specifically, examples of multimerization domains that can be linked to the recombinant RSV F protein of the present application include, but are not limited to: (1) GCN4 leucine zipper (for specific sequence and information, please refer to Harbury et al. 1993 Science 262: 1401-1407); (2) Trimerization motif from pulmonary surfactant protein (for specific sequence and information, please refer to Hoppe et al. 1994 FEBS Lett 344: 191-195); (3) Collagen (for specific sequence and information, please refer to McAlinden et al. 2003 Biol Chem 278:42200-42207, ); and (4) Bacteriophage T4 fibritin foldon (for specific sequence and information, please refer to Miroshnikov et al., 1998 Protein Eng 11:329-414). Typically, the multimerization domain is linked to the C-terminus of the F1 domain. It can be connected directly or via a linker (e.g., an amino acid linker, e.g., the sequence GG, GS, or SAIG) to the F1 domain. The linker can also be a longer linker (e.g., a sequence comprising repeats of GG). In some embodiments, a protease cleavage site can also be included between the F1 domain and the multimerization domain for removing the multimerization domain from the recombinant RSV F protein. In certain embodiments, the multimerization domain is a dimerization domain, a trimerization domain, a tetramerization domain, or a pentamerization domain. In certain embodiments, the multimerization domain is derived from T4 phage fibritin (T4 fibritin). In certain embodiments, the multimerization domain has the sequence as set forth in SEQ ID NO: 39. In certain embodiments, the multimerization domain is a leucine zipper or an isoleucine zipper. In certain embodiments, the multimerization domain has the sequence as set forth in SEQ ID NO: 60. In certain embodiments, the multimerization domain is derived from pulmonary surfactant protein. In certain embodiments, the multimerization domain is located at the C-terminus of the F1 domain. In certain embodiments, the multimerization domain is linked to the F1 domain with or without a second linking peptide. In certain embodiments, the second linking peptide has the sequence as set forth in SEQ ID NO: 61. Tag In certain embodiments, the recombinant RSV F protein of the present invention can be linked to a tag to facilitate expression, detection, tracking, and / or purification of the protein of the present invention. Such epitope tags are well known to those skilled in the art, and examples thereof include, but are not limited to, His, V5, FLAG, HA, Myc, VSV-G, Trx, etc. Those skilled in the art know how to select an appropriate epitope tag according to the desired purpose (e.g., purification, detection, or tracking). In certain embodiments, the tag is selected from a polyhistidine tag, an antigenic or epitope tag, an enzyme tag, or any combination thereof. In certain embodiments, the tag is located at the terminus (e.g., C-terminus) of the fusion protein. In certain embodiments, the tag is located at the C-terminus of the F1 domain or the multimerization domain. In certain embodiments, the tag is linked to the F1 domain or the multimerization domain with or without a third linking peptide. In certain exemplary embodiments, the tag is a polyhistidine tag, i.e., 6xHis-tag (HHHHHH). In certain exemplary embodiments, the tag is linked to a polyhistidine tag via a enzyme cleavage site. In certain embodiments, the fusion protein comprises sequentially from N-terminus to C-terminus: F2 domain, linker, F1 domain. In certain embodiments, the fusion protein comprises sequentially from N-terminus to C-terminus: F2 domain, linker, F1 domain, multimerization domain. In certain embodiments, the multimerization domain is linked to the F1 domain with or without a second linking peptide. In certain embodiments, the fusion protein comprises sequentially from N-terminus to C-terminus: F2 domain, linker, F1 domain, second linking peptide, multimerization domain; in certain embodiments, the fusion protein comprises or does not comprise a tag at its C-terminus. In certain embodiments, the fusion protein comprises or does not comprise a signal peptide at its N-terminus. In certain embodiments, the fusion protein has: (i) a sequence set forth in any one of SEQ ID NOs: 4-38; (ii) a sequence having substitution, deletion, and / or addition of one or more amino acids (e.g., substitution, deletion, and / or addition of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids) compared to the sequence set forth in any one of SEQ ID NOs: 4-38; (iii) a sequence having at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.5% sequence identity to the sequence set forth in any one of SEQ ID NOs: 4-38. In certain embodiments, the fusion protein is in the form of a multimer (e.g., dimer, trimer, tetramer), a monomer, or a mixture thereof. In certain embodiments, the fusion protein is in the pre-fusion conformation (pre-F), the post-fusion conformation (post-F), or a mixture thereof. Nucleic Acid Molecule It is readily understood that the nucleic acid molecule can be used for cloning or expressing the recombinant RSV F protein or fusion protein of the present invention. In some cases, to improve efficiency, the nucleotide sequence of the nucleic acid molecule can be codon-optimized according to cellular preference. Therefore, in a third aspect, the present application provides a nucleic acid molecule comprising a nucleotide sequence encoding the recombinant RSV F protein according to the first aspect or the fusion protein according to the second aspect. In certain embodiments, the nucleotide sequence has been codon-optimized or not optimized according to the codon preference of a host cell. In certain embodiments, the nucleic acid molecule is DNA, or an RNA (mRNA) product transcribed from the DNA, or a mixture thereof. The nucleic acid molecule of the present application can comprise DNA, cDNA, and RNA sequences. The present application also encompasses a nucleic acid molecule encoding the separate F2 domain or F1 domain of the recombinant RSV F protein according to the first aspect. The nucleic acid molecule can be incorporated into a vector, such as an expression vector. Vector Vectors for expressing the recombinant RSV F protein or fusion protein of the present application in insect or mammalian cells are known in the art. These vectors can be cloning vectors or expression vectors. In certain preferred embodiments, the vector of the present invention can be, for example, a plasmid; a phagemid; a cosmid; an artificial chromosome, such as a yeast artificial chromosome (YAC), bacterial artificial chromosome (BAC), or P1-derived artificial chromosome (PAC); a bacteriophage such as X phage or M13 phage; or, a viral vector, etc. Viruses that can be used as vectors include, but are not limited to, retrovirus (including lentivirus), adenovirus, adeno-associated virus, herpesvirus (e.g., herpes simplex virus), poxvirus, baculovirus, papillomavirus, and papovavirus (e.g., SV40). In certain preferred embodiments, the vector of the present application is capable of expressing or is used for expressing the recombinant RSV F protein or fusion protein of the present invention. In certain preferred embodiments, the vector of the present invention is capable of or is used for expressing the recombinant RSV F protein or fusion protein of the present invention in a subject (e.g., a mammal, such as a human). The vector of the present application can comprises various elements, including but not limited to one or more of the following: an origin of replication; a selectable marker gene; one or more expression control elements, such as transcriptional control elements (e.g., promoter, enhancer, terminator) and / or one or more translational signals; and a signal sequence or leader sequence for targeting to the secretory pathway in a selected host cell. In a fourth aspect, the present application provides a vector, which comprises the nucleic acid molecule according to the third aspect. In certain embodiments, the vector is a viral vector. In certain embodiments, the viral vector is selected from the group consisting of: influenza virus vector, retrovirus vector, adenovirus vector, adeno-associated virus vector, herpesvirus vector, poxvirus vector, baculovirus vector, papillomavirus vector, or papovavirus vector. Host Cell The recombinant RSV F protein provided in the present application can be prepared by conventional methods known in the art, such as by using a suitable vector in a recombinant host cell. Host cells include, for example, insect cells, mammalian cells, avian cells, bacteria, and yeast cells. Examples of insect cells include, for example, Sf9 cells, Sf21 cells, Tn5 cells, and Schneider S2 cells. Examples of mammalian cells include Chinese hamster ovary (CHO) cells, human embryonic kidney cells (HEK293 or Expi 293 cells), NIH-3T3 cells, 293-T cells, Vero cells, and HeLa cells. Avian cells include, for example, chicken embryonic stem cells, chicken embryonic fibroblasts, chicken embryonic germ cells, quail fibroblasts, and duck cells. Insect cell expression systems, such as baculovirus vector systems, are known to those skilled in the art and described in, for example, Summers and Smith, Texas Agricultural Experiment Station Bulletin No. 1555 (1987). Avian cell expression systems are also known to those skilled in the art and described in, for example, U.S. Patent Nos. 5,340,740; 5,656,479; 5,830,510; 6,114,168 and 6,500,668. Similarly, bacterial and mammalian cell expression systems are also known in the art and described in, for example, Yeast Genetic Engineering (Barr et al., eds., 1989) Butterworths, London. In a fifth aspect, the present application provides a host cell, which comprises the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect, or the nucleic acid molecule according to the third aspect, or the vector according to the fourth aspect. In certain embodiments, the host cell is selected from a prokaryotic cell (e.g., an Escherichia coli cell) or a eukaryotic cell. In certain embodiments, the eukaryotic cell is a mammalian cell, such as a mouse cell or a human cell. In certain embodiments, the recombinant RSV F protein or fusion protein is displayed on the surface of the cell membrane of the host cell. Preparation Method The recombinant RSV F protein or fusion protein of the present application can be prepared using any method known in the art and is not limited to specific expression methods (e.g., recombinant expression). Methods for expressing and purifying the recombinant RSV F protein according to the first aspect or the fusion protein according to the second aspect of the present application are common in the art and can be specifically found in the following references: Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 2001; and Ausubel et al., Short Protocols in Molecular Biology, 4th ed., John Wiley & Sons, Inc., 1999. Therefore, in a sixth aspect, the present application provides a method for expressing or producing the recombinant RSV F protein according to the first aspect or the fusion protein according to the second aspect, the method comprising culturing the host cell according to the fifth aspect under a condition that allows expression of the protein, and optionally, recovering or purifying the recombinant RSV F protein or fusion protein expressed by the host cell. Vaccine The vaccine provided in the present application is not limited to protein form, nucleic acid form, or a mixture thereof. Furthermore, the nucleic acid can be selected from DNA, cDNA, RNA, or any combination thereof. In a seventh aspect, the present application provides a vaccine comprising one or more selected from the following (1) to (4): (1) the recombinant RSV F protein according to the first aspect; (2) the fusion protein according to the second aspect; (3) the nucleic acid molecule according to the third aspect; (4) the vector according to the fourth aspect. In certain embodiments, the vaccine further comprises an adjuvant and / or a buffer. In certain embodiments, the adjuvant is selected from metal salt, 3-D-monophosphoryl lipid A (MPL), saponin, oil and water emulsion, liposome, nanoparticle, or any combination thereof. In certain embodiments, the fusion protein in the vaccine is in the form of a multimer (e.g., dimer, trimer, tetramer), a monomer, or a mixture thereof. In certain embodiments, the recombinant RSV F protein or fusion protein in the vaccine is in the pre-fusion conformation (pre-F), the post-fusion conformation (post-F), or a mixture thereof. The vaccines provided in the present application can be administered via standard routes of administration. Non-limiting examples include parenteral administration, such as intradermal, intramuscular, subcutaneous, transdermal, mucosal, or oral administration. A single administration or one or more booster administrations can be given to a subject. If a booster vaccination is given, the booster vaccination will typically be administered to the same individual at a time between 1 week and 10 years, for example between 2 weeks and 6 months, after the first administration to the individual (which in such cases is termed "primary vaccination"). The vaccine provided in the present application can also be used with one or more other vaccines. For example, in adults, it can be used with influenza vaccine, Prevnar, tetanus vaccine, diphtheria vaccine, and pertussis vaccine. For children, the vaccine provided in the present application can be used with any other vaccine indicated for pediatric patients. Immunogenic Composition In an eighth aspect, the present application provides an immunogenic composition, which comprises: (i) a first immunogenic component, wherein the first immunogenic component is selected from one or more of the following (1) to (4): (1) the recombinant RSV F protein according to the first aspect; (2) the fusion protein according to the second aspect; (3) the nucleic acid molecule according to the third aspect; (4) the vector according to the fourth aspect; and (ii) a second immunogenic component. In certain embodiments, the first immunogenic component and the second immunogenic component are each independently selected from a protein component, a nucleic acid component, or any combination thereof. In certain embodiments, the first immunogenic component and the second immunogenic component are formulated for simultaneous or separate administration. In certain embodiments, the immunogenic composition further comprises more immunogenic components (e.g., a third immunogenic component, a fourth immunogenic component, a fifth immunogenic component). In certain embodiments, the second immunogenic component is an immunogen derived from another strain of RSV. For example, the first immunogenic component is an immunogen derived from an RSV subtype A strain, and the second immunogenic component is an immunogen derived from an RSV subtype B strain. In certain embodiments, the recombinant RSV F proteins comprised in the first immunogenic component and the second immunogenic component may comprise the same or different amino acid mutations. In certain embodiments, the second immunogenic component is an immunogen derived from another protein of RSV. For example, the first immunogenic component is an immunogen derived from RSV F protein, and the second immunogenic component is an immunogen derived from RSV attachment protein (G) protein or RSV small hydrophobic protein (SH) protein. In certain embodiments, the recombinant RSV F proteins comprised in the first immunogenic component and the second immunogenic component may comprise the same or different amino acid mutations. In certain embodiments, the second immunogenic component is an immunogen derived from a pathogenic organism different from RSV. For example, the first immunogenic component is an immunogen derived from RSV, and the second immunogenic component is an immunogen derived from a virus different from RSV (e.g., hepatitis B virus (HBV), parainfluenza virus (PIV), poliovirus, influenza virus). In certain embodiments, the recombinant RSV F proteins comprised in the first immunogenic component and the second immunogenic component may comprise the same or different amino acid mutations. Kit In a ninth aspect, the present application provides a kit, which comprises an immunogenic component, wherein the immunogenic component is selected from one or more of the following (1) to (4): (1) the recombinant RSV F protein according to the first aspect; (2) the fusion protein according to the second aspect; (3) the nucleic acid molecule according to the third aspect; (4) the vector according to the fourth aspect. In certain embodiments, the kit further comprises a carrier component capable of displaying the immunogenic component. In certain embodiments, the carrier component is selected from: nanomaterials (e.g., lipid nanoparticles, protein nanoparticles, polymer nanoparticles, inorganic nanocarriers, and biomimetic nanoparticles), bacterial outer membrane vesicles (OMVs), multimerization scaffolds, virus-like particles (VLPs), or any combination thereof. In certain embodiments, the immunogenic component and the carrier component in the kit are provided separately, or provided as a complex. In certain embodiments, the immunogenic component is in the form of a multimer (e.g., dimer, trimer, tetramer), a monomer, or a mixture thereof. In certain embodiments, the immunogenic component in the kit is provided in protein form or nucleic acid form. In certain embodiments, the carrier component in the kit is provided in protein form or nucleic acid form. In certain embodiments, the VLP is assembled from proteins obtained from RSV, hepatitis B virus (HBV), human papillomavirus (HPV), or human immunodeficiency virus (HIV). Pharmaceutical Composition In a tenth aspect, the present application provides a pharmaceutical composition, which comprises: (i) any one or more selected from the following (1) to (8): (1) the recombinant RSV F protein according to the first aspect; (2) the fusion protein according to the second aspect; (3) the nucleic acid molecule according to the third aspect; (4) the vector according to the fourth aspect; (5) the host cell according to the fifth aspect; (6) the vaccine according to the seventh aspect; (7) the immunogenic composition according to the eighth aspect; (8) the kit according to the ninth aspect; and (ii) a pharmaceutically acceptable carrier and / or excipient, a buffer, an adjuvant, or any combination thereof. In certain preferred embodiments, the pharmaceutically acceptable carrier and / or excipient is selected from pH adjuster (including but not limited to phosphate buffer), surfactant (including but not limited to a cationic, anionic, or non-ionic surfactant, such as Tween-80), adjuvant, ionic strength enhancer (including but not limited to sodium chloride), diluent, excipient, medium for containing or administering therapeutic agent, and any combination thereof. In certain preferred embodiments, the pharmaceutically acceptable carrier can be a sterile liquid, such as water and oil, including oils derived from petroleum, animals, plants, or synthetic oils, for example, peanut oil, soybean oil, mineral oil, sesame oil, and the like. In certain preferred embodiments, the pharmaceutically acceptable carrier is selected from water, saline solution, aqueous dextrose, glycerol, and any combination thereof. In certain preferred embodiments, the pharmaceutically acceptable excipient can be selected from starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glyceryl monostearate, talc, sodium chloride, skim milk powder, glycerol, propylene, glycol, water, ethanol, and any combination thereof. In certain preferred embodiments, the pharmaceutical composition can be in the form of a solution, suspension, emulsion, tablet, pill, capsule, powder (e.g., lyophilized powder), sustained-release formulation, or the like. The pharmaceutical composition of the present invention can be administered by various suitable modes. Suitable modes of administration include, but are not limited to, parenteral administration, e.g., intravenous, intradermal, subcutaneous, buccal, intranasal (e.g., inhalation), transdermal (e.g., topical), transmucosal, and rectal administration. In certain preferred embodiments, the pharmaceutical composition is formulated according to conventional procedures as a pharmaceutical preparation suitable for intravenous, subcutaneous, intramuscular, buccal, intranasal, or topical administration to humans. Typically, pharmaceutical compositions for injection (e.g., intravenous administration, e.g., via bolus injection or continuous infusion) are sterile and isotonic. If desired, such pharmaceutical compositions may also contain a solubilizer and a local anesthetic such as ergotamine to alleviate pain at the injection site. Additionally, pharmaceutical compositions for injection may also contain a preservative. In certain preferred embodiments, pharmaceutical compositions for injection may also be presented in unit dosage form (e.g., stored in ampoules or in multi-dose containers). In certain embodiments, the pharmaceutical composition of the present invention may comprise an additional active ingredient, for example, additional vaccine, antiviral agent, and / or monoclonal antibody. In certain embodiments, the additional vaccine, antiviral agent, and / or monoclonal antibody is an additional vaccine, antiviral agent, and / or monoclonal antibody against RSV; or a vaccine, antiviral agent, and / or monoclonal antibody against a pathogenic organism other than RSV. In certain embodiments, the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect, or the nucleic acid molecule according to the third aspect, or the vector according to the fourth aspect, or the host cell according to the fifth aspect, or the vaccine according to the seventh aspect, or the immunogenic composition according to the eighth aspect, or the kit according to the ninth aspect, and the additional active ingredient can be administered simultaneously, separately, or sequentially. Use In another aspect, the present application provides a use of the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect, or the nucleic acid molecule according to the third aspect, or the vector according to the fourth aspect, or the host cell according to the fifth aspect, or the vaccine according to the seventh aspect, or the immunogenic composition according to the eighth aspect, or the kit according to the ninth aspect, in the manufacture of a pharmaceutical composition for inducing an immune response against RSV in a subject. In certain embodiments, the immune response comprises inducing the production of an antibody (e.g., a neutralizing antibody) against RSV in the subject. In certain embodiments, the subject is a mammal, e.g., a mouse, a human. In certain embodiments, the subject is selected from infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus. In another aspect, the present application provides a use of the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect, or the nucleic acid molecule according to the third aspect, or the vector according to the fourth aspect, or the host cell according to the fifth aspect, or the vaccine according to the seventh aspect, or the immunogenic composition according to the eighth aspect, or the kit according to the ninth aspect, in the manufacture of a pharmaceutical composition for preventing and / or treating a RSV infection or a disease and / or symptom caused by RSV infection. In certain embodiments, the subject is a mammal, e.g., a mouse, a human. In certain embodiments, the subject is selected from infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus. In certain embodiments, the disease and symptom caused by RSV infection are selected from bronchitis, pneumonia, asthma, obstructive pulmonary disease, and cardiopulmonary complications. Method In another aspect, the present application provides a method for inducing an antibody against RSV, the method comprising administering an effective amount of the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect, or the nucleic acid molecule according to the third aspect, or the vector according to the fourth aspect, or the host cell according to the fifth aspect, or the vaccine according to the seventh aspect, or the immunogenic composition according to the eighth aspect, or the kit according to the ninth aspect, in a cell in vitro or in a subject. In certain embodiments, the mode of administration comprises intradermal, intramuscular, subcutaneous, transdermal, mucosal, or oral administration. In certain embodiments, the subject is a mammal, e.g., a mouse, a human. In certain embodiments, the subject is selected from infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus. In another aspect, the present application provides a method for detecting the presence of RSV infection in a subject in vitro, the method comprising: contacting a biological sample obtained from the subject with the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect; and detecting the presence of a complex formed by the recombinant RSV F protein or the fusion protein and an antibody. In certain embodiments, the subject is a mammal, e.g., a mouse, a human. In certain embodiments, the subject is selected from infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus. In certain embodiments, the biological sample is selected from whole blood, serum, plasma, or any combination thereof. In another aspect, the present application provides a method for screening a candidate drug capable of inhibiting RSV infection in a cell, the method comprising contacting the host cell with the candidate drug before, simultaneously with, or after contacting the host cell with the recombinant RSV F protein according to the first aspect, or the fusion protein according to the second aspect. Definition of Terms As used herein, the term "respiratory syncytial virus (RSV)" is a virus of the genus Pneumovirus and the family Pneumoviridae. The RSV genome is approximately 15 Kb in length and contains 10 genes encoding 11 proteins, including 8 structural proteins (F, G, M2-1, M2-2, SH, N, P, L) and 3 non-structural proteins (NS1, NS2, NS3). Among them, the fusion protein (F) and the attachment protein (G) are the two major envelope glycoproteins. The F protein is a type I glycoprotein that can be cleaved by cellular proteases into an F1 polypeptide and an F2 polypeptide. RSV strains exist in subtypes A and B, and their F protein amino acid sequences are approximately 90% homologous. Many RSV strains have been isolated to date and the amino acid sequences of their F proteins have been reported. For example, an example sequence of the F protein of subtype A is provided in SEQ ID NO: 1 (A2 strain; GenBank GI: QGW56794.1; Swiss Prot P03420), and an example sequence of the F protein of subtype B is provided in SEQ ID NO: 2 (18537 strain; GenBank GI: 138250; Swiss Prot P13843) or SEQ ID NO: 64. SEQ ID NO: 1 and SEQ ID NO: 2 are both sequences of 574 amino acids. As used herein, RSV encompasses naturally occurring RSV, as well as RSV generated by genetic drift, artificial synthesis, and / or recombination, and also includes variants derived from naturally occurring RSV. As used herein, the terms "F protein" or "fusion protein" or "F protein polypeptide" or "fusion protein polypeptide" refer to a polypeptide or protein having all or part of the amino acid sequence of the RSV fusion protein. The term "G protein" as used in the description refers to a polypeptide or protein having all or part of the amino acid sequence of the RSV attachment protein. The sequences of many RSV fusion and attachment proteins have been reported. WO2008 / 114149 discloses exemplary available F and G protein variants (e.g., naturally occurring variants). As used herein, the terms "wild-type", "wild type", or "natural" are used interchangeably. When these terms are used to describe a nucleic acid molecule, polypeptide, or protein, they mean that the nucleic acid molecule, polypeptide, or protein exists in nature, is found in nature, and has not been subjected to any artificial modification or processing. As used herein, the wild-type respiratory syncytial virus (RSV) F protein refers to a naturally occurring, biologically active F protein. As used herein, the terms "F0 polypeptide (F0)" or "F0 precursor" refer to the precursor polypeptide of the RSV F protein. The F0 polypeptide of RSV strains consists of 574 amino acids. In vivo, F0 oligomerizes in the endoplasmic reticulum and is proteolytically processed by furin at two conserved furin consensus sequences (furin cleavage sites), RARR (SEQ ID NO: 62) and RKRR (SEQ ID NO: 63), to produce oligomers composed of two disulfide-linked fragments. The smaller of these fragments is F2 and originates from the N-terminal portion of the F0 precursor. The larger is F1 and originates from the C-terminal portion of the F0 precursor. As used herein, the terms "F1 polypeptide (F1)" or "F1 domain" are used interchangeably and refer to the polypeptide chain of the mature RSV F protein. The natural F1 polypeptide includes approximately amino acids 137-574 of the RSV F0 precursor and consists of (from N-terminus to C-terminus) the ectodomain (ED) (positions 137-524), the transmembrane domain (TM) (positions 525-550), and the cytoplasmic tail (CT) (positions 551-574). As used herein, "F1 polypeptide (F1)" or "F1 domain" encompasses natural F1 polypeptides or fragments thereof, as well as F1 polypeptides from natural F1 polypeptide sequences that include a modification (e.g., a substitution, insertion, or deletion of 1 or more amino acids). In certain embodiments, the modification is a modification that stabilizes the recombinant RSV F protein or enhances the immunogenicity of the recombinant RSV F protein. As used herein, the terms "F2 polypeptide (F2)" or "F2 domain" are used interchangeably and refer to the polypeptide chain of the mature RSV F protein. The natural F2 polypeptide includes approximately amino acids 1-109 of the RSV F0 precursor. As used herein, "F2 polypeptide (F2)" or "F2 domain" encompasses natural F2 polypeptides or fragments thereof, as well as F2 polypeptides from natural F2 polypeptide sequences that include a modification (e.g., a substitution, insertion, or deletion of 1 or more amino acids). In certain embodiments, the modification is a modification that stabilizes the recombinant RSV F protein or enhances the immunogenicity of the recombinant RSV F protein. As used herein, the terms "pep27 polypeptide" or "pep27 domain" are used interchangeably and refer to the polypeptide consisting of 27 amino acids excised from the F0 precursor during RSV F protein maturation. The sequence of the pep27 domain is flanked by two furin cleavage sites that are cleaved by cellular proteases during F protein maturation to generate the F1 polypeptide and F2 polypeptide. As used herein, the terms "multimerization domain", "multimerization motif", "fold", "folding domain", or "foldon" have the same meaning and are used interchangeably. They refer to an amino acid sequence capable of forming a multimer. In certain embodiments, they are capable of promoting the assembly of polypeptide or protein into a dimer, trimer, tetramer, or pentamer. As used herein, the term "immunogenicity" refers to the ability of a substance to elicit, trigger, stimulate, or induce an immune response against a specific antigen in a human or animal, in the presence or absence of an adjuvant. As used herein, the terms "immunogen" or "immunogenic component" refer to a substance having immunogenicity. In certain embodiments, it prevents (or alleviates or ameliorates) a symptom or disease caused by a pathogen by inhibiting the replication of the pathogen (e.g., RSV) after a subject is exposed to the pathogen. Herein, "immunogen" or "immunogenic component" should be understood to encompass a substance (e.g., vaccine) intended for administration to a subject or a population of subjects to elicit a protective or palliative immune response against RSV. As used herein, the term "immunogenic composition" refers to a composition of matter suitable for administration to a human or animal subject (e.g., in an experimental setting) that is capable of eliciting a specific immune response, e.g., a specific immune response against a pathogen such as RSV. Thus, an immunogenic composition contains one or more antigens (e.g., polypeptide antigens) or antigenic epitopes. An immunogenic composition may also contain one or more additional components capable of eliciting or enhancing an immune response, such as excipients, carriers, and / or adjuvants. As used herein, the term "immune response" refers to a response of immune system cells, such as B cells, T cells, or monocytes, to a stimulus. An immune response can be a B cell response, resulting in the production of a specific antibody, such as antigen-specific neutralizing antibody. An immune response can also be a T cell response, such as a CD4+ response or a CD8+ response. In some embodiments, the response is specific for a particular antigen (i.e., an "antigen-specific response"). If the antigen is derived from a pathogen, the antigen-specific response is a "pathogen-specific response". "Protective immune response" refers to an immune response that inhibits the harmful function or activity of a pathogen, reduces pathogen infection, or reduces symptom (including death) resulting from pathogen infection. Herein, immune response encompasses all of the above. As used herein, the term "adjuvant" refers to an agent that enhances the production of an immune response in a non-specific manner. Common adjuvants include: suspensions of minerals (alum, aluminum hydroxide, aluminum phosphate) to which the antigen is adsorbed, and emulsions; the emulsions can include water-in-oil, oil-in-water (and variations thereof, including double emulsions and reversible emulsions), glycolipids, lipopolysaccharides, immunostimulatory nucleic acids (e.g., CpG oligonucleotides), liposomes, Toll-like receptor agonists (particularly, TLR2, TLR4, TLR7 / 8, and TLR9 agonists), and various combinations of the above. As used herein, the term "mutation" refers to the inclusion of a deletion, addition, or substitution of an amino acid residue in the amino acid sequence of a protein or polypeptide compared to the amino acid sequence of a reference protein or polypeptide. In the description (particularly the examples), substitution of an amino acid at a specific position in a protein sequence is expressed as "(amino acid residue in wild-type protein) (amino acid position) (amino acid residue in engineered protein)". For example, "A298L" means that the alanine (A) residue at position 298 of the reference protein amino acid sequence is replaced with a leucine (L) residue. As used herein, the term "corresponding position" refers to the amino acid position in the two sequences being compared that is located at an equivalent position when the two sequences are optimally aligned, i.e., when the two sequences are aligned to obtain the highest percent identity. For example, the expression "positions corresponding to positions 35, 60, 79, 92, 189, 190, 227, 238, 298, 320, 326, 377, 405, 437, 481, and 496 of SEQ ID NO: 1" means that when a certain sequence is optimally aligned with SEQ ID NO: 1, i.e., when the certain sequence is aligned with SEQ ID NO: 1 to obtain the highest percent identity, the amino acid positions in the compared sequence that are at positions equivalent to positions 35, 60, 79, 92, 189, 190, 227, 238, 298, 320, 326, 377, 405, 437, 481, and 496 of SEQ ID NO: 1. As used herein, the term "identity" is used to refer to the matching of sequences between two polypeptides or between two nucleic acids. When a position in both of the two sequences being compared is occupied by the same base or amino acid monomer subunit (e.g., if a position in each of two DNA molecules is occupied by adenine, or a position in each of two polypeptides is occupied by lysine), then the molecules are identical at that position. The "percent identity" between two sequences is a function of the number of matching positions shared by the two sequences divided by the number of positions compared x 100. For example, if 6 of 10 positions in two sequences match, then the two sequences have 60% identity. For example, the DNA sequences CTGACT and CAGGTT share 50% identity (3 of 6 total positions match). Typically, comparisons are made when two sequences are aligned to yield maximum identity. Such alignment can be performed using, for example, the method of Needleman et al. (1970) J. Mol. Biol. 48:443-453, which can be conveniently performed by computer programs such as the Align program (DNAstar, Inc.). Percent identity between two amino acid sequences can also be determined using the algorithm of E. Meyers and W. Miller (Comput. Appl Biosci., 4:11-17 (1988)) incorporated into the ALIGN program (version 2.0), using a PAM120 weight residue table, a gap length penalty of 12, and a gap penalty of 4. Additionally, percent identity between two amino acid sequences can be determined using the algorithm of Needleman and Wunsch (J Mol Biol. 48:444-453 (1970)) incorporated into the GAP program in the GCG software package (available at www.gcg.com), using a Blossum 62 matrix or PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6. As used herein, the term "antigen" refers to a molecule that can be recognized by an antibody. Examples of antigens include molecules containing antigenic determinants, such as polypeptides, lipids, polysaccharides, and nucleic acids recognized by immune cells. As used herein, the term "D25" refers to the antibody described in WO 2008 / 147196 A2, which has a heavy chain variable domain comprising the amino acid sequence as set forth in SEQ ID NO: 40 and a light chain variable domain comprising the amino acid sequence as set forth in SEQ ID NO: 41. As used herein, the term "Palivizumab" refers to palivizumab, which has a heavy chain variable domain comprising the amino acid sequence as set forth in SEQ ID NO: 42 and a light chain variable domain comprising the amino acid sequence as set forth in SEQ ID NO: 43. As used herein, the term "C-terminal truncation of X amino acids" means that the X consecutive amino acids at the very end of the C-terminus are truncated. Similarly, the term "N-terminal truncation of X amino acids" means that the X consecutive amino acids at the very end of the N-terminus are truncated. As used herein, the term "vector" refers to a nucleic acid vehicle into which a polynucleotide can be inserted. When the vector enables expression of the protein encoded by the inserted polynucleotide, the vector is called an expression vector. The vector can be introduced into a host cell by transformation, transduction, or transfection, allowing the genetic material elements it carries to be expressed in the host cell. Vectors are well known to those skilled in the art and include, but are not limited to: plasmid; phagemid; cosmid; artificial chromosome, such as yeast artificial chromosome (YAC), bacterial artificial chromosome (BAC), or Pl-derived artificial chromosome (PAC); bacteriophage such as X phage or M13 phage, and animal virus. Animal viruses that can be used as vectors include, but are not limited to, retrovirus (including lentivirus), adenovirus, adeno-associated virus, herpesvirus (e.g., herpes simplex virus), poxvirus, baculovirus, papillomavirus, and papovavirus (e.g., SV40). A vector may contain various control elements for expression, including but not limited to, promoter sequence, transcription initiation sequence, enhancer sequence, selection element, and reporter gene. Additionally, the vector may contain an origin of replication. As used herein, the term "host cell" refers to a cell into which a vector can be introduced, including but not limited to, prokaryotic cell such as Escherichia coli or Bacillus subtilis, fungal cell such as yeast cell or Aspergillus cell, insect cell such as S2 Drosophila cell or Sf9 cell, or animal cell such as fibroblast, CHO cell, COS cell, NSO cell, HeLa cell, BHK cell, HEK 293 cell, or human cell. As known to those skilled in the art, codons have degeneracy. That is, during protein translation, each amino acid can correspond to one or more codons, for example, up to 6 codons. Different species exhibit great variation in their use of degenerate codons encoding a particular amino acid, a phenomenon known as "codon bias." Therefore, as used herein, the term "codon bias" refers to the preference of a particular species for using certain specific codons to encode amino acids. Optimizing the sequence of a nucleic acid molecule based on codon bias can be particularly advantageous in some cases, for example, it may help increase the expression level of the protein encoded by the nucleic acid molecule. For example, when using E. coli (or human cells) to express a protein or fragment thereof, it would be potentially advantageous to optimize the nucleic acid sequence encoding the protein or fragment thereof for the codon bias of E. coli (or human cells). As used herein, the term "virus-like particle (VLP)" is a multimeric particle whose structure is similar or dissimilar to that of a native viral particle. In certain embodiments, VLPs are native viral particles. In certain embodiments, VLPs are virus-like particles assembled from proteins. It has been demonstrated that after recombinant expression in appropriate expression systems, proteins from some viruses (e.g., RSV, HBV, HEV, HPV) (e.g., capsid proteins, surface proteins, envelope proteins) can spontaneously form VLPs. As used herein, the term "pharmaceutically acceptable" means that which is recognized in the pharmaceutical field as suitable for use in animals, particularly humans. As used herein, the term "pharmaceutically acceptable carrier and / or excipient" refers to a carrier and / or excipient that is compatible with the subject and active ingredient pharmacologically and / or physiologically, and is well known in the art (see, e.g., Remington's Pharmaceutical Sciences. Edited by Gennaro AR, 19th ed. Pennsylvania: Mack Publishing Company, 1995), and includes, but is not limited to: pH adjuster (including but not limited to phosphate buffer), surfactant (including but not limited to cationic, anionic, or non-ionic surfactant, such as Tween-80), adjuvant, ionic strength enhancer (including but not limited to sodium chloride), diluent, excipient, medium for containing or administering therapeutic agent, and any combination thereof. As used herein, the pharmaceutically acceptable carrier can be a sterile liquid, such as water and oil, including oil derived from petroleum, animal, or plant, or synthetic oil, for example, peanut oil, soybean oil, mineral oil, sesame oil, and the like. When the pharmaceutical composition is administered intravenously, physiological saline is a preferred carrier. Saline solutions, as well as aqueous dextrose and glycerol solutions, can also be used as liquid carriers, particularly for injectable solutions. As used herein, the pharmaceutically acceptable excipient can include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glyceryl monostearate, talc, sodium chloride, skim milk powder, glycerol, propylene, glycol, water, ethanol, and the like. If desired, the pharmaceutical composition may also contain a wetting agent or an emulsifying agent, such as sodium hyaluronate, or pH buffering agent. The pharmaceutical composition may take the form of solution, suspension, emulsion, tablet, pill, capsule, powder, sustained-release formulation, and the like. As used herein, the term "subject" refers to a mammal, including but not limited to, human, rodent (mouse, rat, guinea pig), dog, horse, cow, cat, pig, monkey, chimpanzee, etc. Preferably, the subject is a human. As used herein, the term "effective amount" refers to an amount sufficient to obtain, or at least partially obtain, the desired effect. For example, a prophylactically effective amount for a disease refers to an amount sufficient to prevent, arrest, or delay the onset of the disease; a therapeutically effective amount for a disease refers to an amount sufficient to cure or at least partially arrest the disease and its complications in a patient already suffering from the disease. Determining such an effective amount is well within the capability of those skilled in the art. For example, an effective amount for therapeutic use will depend on the severity of the disease to be treated, the overall state of the patient's own immune system, the patient's general condition such as age, weight, and sex, the mode of administration of the drug, and other treatments being administered simultaneously, etc. Beneficial Effects of the Invention The recombinant RSV F protein of the present application comprises an amino acid mutation that stabilizes the pre-fusion (pre-F) conformation of the RSV F protein, and therefore has increased stability compared to the wild-type RSV F protein. Furthermore, compared to the wild-type RSV F protein, it also has a higher proportion of pre-F protein, higher protein expression level, and better thermal stability. Further, the recombinant RSV F protein of the present application also has good immunogenicity and is capable of inducing neutralizing antibodies. In summary, the recombinant RSV F protein of the present application exhibits good protective effects and safety, making it suitable for various vaccine platforms, such as nucleic acid vaccines, recombinant protein vaccines, viral vector vaccines, and particulate vaccines. Therefore, the recombinant RSV F protein of the present application has great potential in inducing an immune response against RSV in a subject, as well as preventing and / or treating RSV infection or diseases and / or symptoms caused by RSV infection. Brief Description of the Drawings Fig. 1 exemplarily shows a predicted structure diagram of one recombinant RSV F protein of the present application. Fig. 2 exemplarily shows the SDS-PAGE results of nRSVF79 protein and nRSVF116 protein, where M: protein marker; reducing: under reducing conditions; non-reducing: under non-reducing conditions. Fig. 3 exemplarily shows the thermal stability test results of 7 recombinant RSV F proteins of the present application. Fig. 4 shows the titers of specific antibodies produced after immunizing mice with 10 recombinant RSV F proteins of the present application, as well as control pre-F and post-F proteins. Fig. 5 shows the titers of neutralizing antibodies produced after immunizing mice with 10 recombinant RSV F proteins of the present application, as well as control pre-F and post-F proteins. The embodiments of the present invention will be described in detail below in conjunction with the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. Various objects and advantageous aspects of the present invention will become apparent to those skilled in the art according to the following detailed description of the preferred embodiments. Sequence Information Information on some sequences related to the present invention is provided in Table 1 below. Table 1: Description of sequences SEQ ID NO: Description Sequence 1 RSV A2 wild-type F protein sequence MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNRARRELPRFMNYTLNNAKKTNVTLSKKRKRRFLGFLL GVGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLT SKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQKNNRLLEITREFSV NAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSY SIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLT RTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNL CNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNR GIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINF YDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLHNVNAGKSTTNIM ITTIIIVIIVILLSLIAVGLLLYCKARSTPVTLSKDQLSGINNIAFSN 2 RSV B18537 wild-type F protein sequence MELLIHRSSAIFLTLAVNALYLTSSQNITEEFYQSTCSAVSRGYFSALR TGWYTSVITIELSNIKETKCNGTDTKVKLIKQELDKYKNAVTELQLLM QNTPAANNRARREAPQYMNYTINTTKNLNVSISKKRKRRFLGFLLGV GSAIASGIAVSKVLHLEGEVNKIKNALLSTNKAVVSLSNGVSVLTSKV LDLKNYINNRLLPIVNQQSCRISNIETVIEFQQMNSRLLEITREFSVNAG VTTPLSTYMLTNSELLSLINDMPITNDQKKLMSSNVQIVRQQSYSIMSI IKEEVLAYVVQLPIYGVIDTPCWKLHTSPLCTTNIKEGSNICLTRTDRG WYCDNAGSVSFFPQADTCKVQSNRVFCDTMNSLTLPSEVSLCNTDIF NSKYDCKIMTSKTDISSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFS NGCDYVSNKGVDTVSVGNTLYYVNKLEGKNLYVKGEPIINYYDPLV FPSDEFDASISQVNEKINQSLAFIRRSDELLHNVNTGKSTTNIMITTIIIVI IVVLLSLIAIGLLLYCKAKNTPVTLSKDQLSGINNIAFSK 3 Foldon-containing A2 F protein ectodomain MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNRARRELPRFMNYTLNNAKKTNVTLSKKRKRRFLGFLL GVGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLT SKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQKNNRLLEITREFSV NAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSY SIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLT RTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNL CNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNR GIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINF YDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAIGGYIPEAPRDG QAYVRKDGEWVLLSTFLGGLVPRGSHHHHHH 4 Amino acid sequence of nRSVF6 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGELPRFMNYTLNNAKKTNVTLSKKRKRFLGSAIAS GVAVSKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLTSKVLDLKN YIDKQLLPIVNKQSCSISNIETVIEFQQKNNRLLEITREFSVNAGVTTPV STYMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSYSIMSIIKEEV LAYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLTRTDRGWYC DNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNLCNVDIFNPK YDCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFSNGC DYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINFYDPLVFPSD EFDASISQVNEKINQSLAFIRKSDELLSAIGGYIPEAPRDGQAYVRKDG EWVLLSTFL 5 Amino acid sequence of nRSVF7 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 6 Amino acid sequence of nRSVF8 MELLILKANAITTILTAVTFCFASGQNITEEFYQYTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 7 Amino acid sequence of nRSVF11 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLIYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 8 Amino acid sequence of nRSVF14 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFLVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 9 Amino acid sequence of nRSVF26 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLLSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 10 Amino acid sequence of nRSVF31 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTIKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 11 Amino acid sequence of nRSVF61 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 12 Amino acid sequence of nRSVF66 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLVSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 13 Amino acid sequence of nRSVF67 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTLKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 14 Amino acid sequence of nRSVF71 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLISKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQKN NRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMS NNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCTT NTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 15 Amino acid sequence of nRSVF73 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLVSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 16 Amino acid sequence of nRSVF74 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTIKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 17 Amino acid sequence of nRSVF75 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTLKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 18 Amino acid sequence MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR of nRSVF76 TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTMKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 19 Amino acid sequence of nRSVF77 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTVKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 20 Amino acid sequence of nRSVF78 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTYKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 21 Amino acid sequence of nRSVF79 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK LNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 22 Amino acid sequence of nRSVF80 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFIVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 23 Amino acid sequence of nRSVF82 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFTVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 24 Amino acid sequence of nRSVF83 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFVVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 25 Amino acid sequence of nRSVF94 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSSLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 26 Amino acid sequence of nRSVF96 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSVLC TTNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDT MNSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYG KTKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEG KSLYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLS AIGGYIPEAPRDGQAYVRKDGEWVLLSTFL 27 Amino acid sequence of nRSVF100 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNEKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 28 Amino acid sequence of nRSVF105 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIFLSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 29 Amino acid sequence of nRSVF106 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIYLSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 30 Amino acid sequence of nRSVF109 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPRVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 31 Amino acid sequence of nRSVF110 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVFEKINQSLAFIRKSDELLSAIG GYIPEAPRDGQAYVRKDGEWVLLSTFL 32 Amino acid sequence of nRSVF111 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVYEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 33 Amino acid sequence of nRSVF112 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTTLQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 34 Amino acid sequence of nRSVF113 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTVLQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 35 Amino acid sequence of nRSVF114 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTMLQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 36 Amino acid sequence of nRSVF115 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTILQLLM QSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKAV VSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQKN NRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMS NNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCTT NTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 37 Amino acid sequence of nRSVF116 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLLKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 38 Amino acid sequence of nRSVF72 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNGGGPGGSAIASGVAVSKVLHLEGEVNKIKSALLSTNKA VVSLSNGVSVLLSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQK NNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLM SNNVQIVRQQSYSIMSIIKEEVLLYVVQLPLYGVIDTPCWKLHTSPLCT TNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTM NSLTLPSEVNLCNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGK TKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKS LYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAI GGYIPEAPRDGQAYVRKDGEWVLLSTFL 39 Amino acid sequence of Foldon GYIPEAPRDGQAYVRKDGEWVLLSTFL 40 D25 heavy chain variable region amino acid sequence QVQLVQSGAEVKKPGSSVMVSCQASGGPLRNYIINWLRQAPGQGPE WMGGIIPVLGTVHYAPKFQGRVTITADESTDTAYIHLISLRSEDTAMY YCATETALVVSTTYLPHYFDNWGQGTLVTVS S 41 D25 light chain variable region amino acid sequence DIQMTQSPSSLSAAVGDRVTITCQASQDIVNYLNWYQQKPGKAPKLL IYVASNLETGVPSRFSGSGSGTDFSLTISSLQPEDVATYYCQQYDNLPL TFGGGTKVEIKR 42 palivizumab heavy chain variable region amino acid sequence QVTLRESGPALVKPTQTLTLTCTFSGFSLSTSGMSVGWIRQPPGKALE WLADIWWDDKKDYNPSLKSRLTISKDTSKNQVVLKVTNMDPADTAT YYCARSMITNWYFDVWGAGTTVTVSS 43 palivizumab light chain variable region amino acid sequence QVTLRESGPALVKPTQTLTLTCTFSGFSLSTSGMSVGWIRQPPGKALE WLADIWWDDKKDYNPSLKSRLTISKDTSKNQVVLKVTNMDPADTAT YYCARSMITNWYFDVWGAGTTVTVSS 44 AM14 heavy chain variable region amino acid sequence EVQLVESGGGVVQPGRSLRLSCAASGFSFSHYAMHWWRQAPGKGLE WWAVISYDGENTYYADSVKGRFSISRDNSKNTVSLQMNSLRPEDTAL YYCARDRIVDDYYYYGMDVWGQGATVTVSS 45 AM14 light chain variable region amino acid sequence DIQMTQSPSSLSASVGDRVTITCQASQDIKKYLNWYHQKPGKVPELL MHDASNLETGVPSRFSGRGSGTDFTLTISSLQPEDIGTYYCQQYDNLP PLTFGGGTKVEIKRTV 46 MPE8 heavy chain variable region amino acid sequence EVQLVESGGGLVKPGGSLRLSCAASGFTFSSYSMNWVRQAPGKGLE WWSSISASSSYSDYADSAKGRFTISRDNAKTSLFLQMNSLRAEDTAIY FCARARATGYSSITPYFDIWGQGTLVTVSS 47 MPE8 light chain variable region amino acid sequence QSVVTQTPSVSGAPGQRVTISCTGSSSNIGAGYDVHWYQQLPGTAPK LLIYDNNNRPSGVPDRFSASKSGTSASLAITGLQAEDEADYYCQSYDR NLSGVFGTGTKVTVL 48 101F heavy chain variable region amino acid sequence QVTLKESGPGILQPSQTLSLTCSFSGFSLSTSGMGVSWIRQPSGKGLE WLAHIYWDDDKRYNPSLKSRLTISKDTSRNQVFLKITSVDTADTATY YCARLYGFTYGFAYWGQGTLVTVSA 49 101F light chain variable region amino acid sequence DIVLTQSPASLAVSLGQRATIFCRASQSVDYNGISYMHWFQQKPGQPP KLLIYAASNPESGIPARFTGSGSGTDFTLNIHPVEEEDAATYYCQQIIED PWTFGGGTKLEIK 50 hRSV90 heavy chain variable region amino acid sequence EVQLVESGGGLVQPRRSLRLSCAASGFTFDDYTIHWVRQAPGKGLE WVSGITWNSGYIGYADSVKGRFTISRDNARNSLYLQMNSLRAEDTAL YYCVRDAYVSGSDYYYYGLDVWGRGTLVTVSS 51 hRSV90 light chain variable region amino acid sequence EIVMTSSPATLSVSPGERVTLFCRASQSVISNLAWYQQKSGQAPRLLI YGASTRATGIPSRFSGSGSGTEFTLTISSLQSEDFAVYFCQQYNNWPLT FGGGTQVNVQ 52 Amino acid sequence of DS-Cav1 MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNRARRELPRFMNYTLNNAKKTNVTLSKKRKRRFLGFLL GVGSAIASGVAVCKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLT FKVLDLKNYIDKQLLPILNKQSCSISNIETVIEFQQKNNRLLEITREFSV NAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSY SIMCIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLT RTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNL CNVDIFNPKYDCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNR GIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINF YDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLSAIGGYIPEAPRDG QAYVRKDGEWVLLSTFLGGLVPRGSHHHHHHSAWSHPQFEK 53 Amino acid sequence of Post-F MELLILKANAITTILTAVTFCFASGQNITEEFYQSTCSAVSKGYLSALR TGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTELQLL MQSTPATNNRARRELPRFMNYTLNNAKKTNVTLSKKRKRRAIASGV AVSKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLTSKVLDLKNYI DKQLLPIVNKQSCSISNIETVIEFQQKNNRLLEITREFSVNAGVTTPVST YMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSYSIMSIIKEEVL AYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLTRTDRGWYCD NAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNLCNVDIFNPKY DCKIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFSNGCD YVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINFYDPLVFPSDE FDASISQVNEKINQSLAFIRKSDELLGLEVLFQGPHHHHHHHHSAWSH PQFEK 54 Linker 1 GGPG 55 Linker 2 GPGGG 56 Linker 3 EAAAK 57 Linker 4 PAAAK 58 Linker 5 GGG 59 Linker 6 GGGPG 60 Multimerization domain-1 EDKIEEILSKIYHIENEIARIKKLIGEA 61 Second linking peptide SAIG 62 Furin cleavage site-1 RARR 63 Furin cleavage site-2 RKRR 64 RSV wild-type F protein sequence MELLIHRSSAIFLTLAVNALYLTSSQNITEEFYQSTCSAVSRGYFSALR TGWYTSVITIELSNIKETKCNGTDTKVKLIKQELDKYKNAVTELQLLM QNTPAANNRARREAPQYMNYTINTTKNLNVSISKKRKRRFLGFLLGV GSAIASGIAVSKVLHLEGEVNKIKNALLSTNKAVVSLSNGVSVLTSKV LDLKNYINNRLLPIVNQQSCRISNIETVIEFQQMNSRLLEITREFSVNAG VTTPLSTYMLTNSELLSLINDMPITNDQKKLMSSNVQIVRQQSYSIMSI IKEEVLAYVVQLPIYGVIDTPCWKLHTSPLCTTNIKEGSNICLTRTDRG WYCDNAGSVSFFPQADTCKVQSNRVFCDTMNSLTLPSEVSLCNTDIF NSKYDCKIMTSKTDISSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFS NGCDYVSNKGVDTVSVGNTLYYVNKLEGKNLYVKGEPIINYYDPLV FPSDEFDASISQVNEKINQSLAFIRRSDELLHNVNTGKSTTNIMITTIIIVI IVVLLLLIAIGLLLYCKAKNTPVTLSKDQLSGINNIAFSK Specific Models for Carrying Out the Invention The present invention is described below with reference to the following examples, which are intended to illustrate, but not to limit, the present invention. Unless otherwise indicated, the experiments and methods described in the examples were performed substantially according to conventional methods well known in the art and described in various references. For example, the conventional techniques used in the present invention in immunology, biochemistry, chemistry, molecular biology, microbiology, cell biology, genomics, and recombinant DNA can be found in Sambrook, Fritsch, and Maniatis, Molecular Cloning: A Laboratory Manual, 2nd edition (1989); Current Protocols in Molecular Biology (F.M. Ausubel et al., eds., (1987)); Methods in Enzymology series (Academic Press, Inc.); PCR 2: A Practical Approach (M.J. MacPherson, B.D. Hames, and G.R. Taylor, eds. (1995)); and Animal Cell Culture (R.I. Freshney, ed. (1987)). Additionally, where conditions were not specified in the examples, they were carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturer was not indicated were conventional products commercially available. Those skilled in the art will appreciate that the examples are provided by way of illustration and are not intended to limit the scope of the claimed invention. All publications and other reference materials mentioned herein are incorporated by reference in their entirety. Example 1. Design of Recombinant RSV F Proteins In this example, various schemes for designing and preparing recombinant RSV F proteins were provided. These recombinant RSV F proteins comprised the F2 fragment, F1 fragment of the RSV F protein, and the trimeric foldon domain of T4 phage fibritin. These recombinant RSV F proteins also comprised a linker connecting the F2 and F1 fragments, and could comprise one or more amino acid mutations (e.g., mutations for enhancing expression level and / or stability). A total of 116 recombinant RSV F proteins were prepared in the present application, and these prepared recombinant RSV F proteins were sequentially named nRSVF1, nRSVF2, ... nRSVF116. Furthermore, the structures of these proteins were predicted by software, and it was found that the structures of these proteins were relatively similar. Fig. 1 exemplarily shows a predicted structural diagram of one of the proteins. Briefly, the design and preparation of the recombinant RSV F proteins in the present application were based on the amino acid sequences as set forth in SEQ ID NO: 3 and SEQ ID NO: 1. Amino acid residues 1 to 513 in SEQ ID NO: 3 were identical to amino acid residues 1 to 513 of the wild-type RSV A2 F0 precursor polypeptide (see SEQ ID NO: 1). Compared to SEQ ID NO: 1, SEQ ID NO: 3 had the transmembrane and intracellular regions removed and was linked to the trimeric foldon domain and His tag via SAIG and GS linker peptides. Each recombinant RSV F protein consisted of an F2 polypeptide, an F1 polypeptide, and an intervening linker. Among which, the F2 polypeptide comprised amino acids 26 to 105 of SEQ ID NO: 3, and the F1 polypeptide comprised amino acids 137 to 513 of SEQ ID NO: 3 (except where mutations or truncations are specifically noted). The signal peptide (amino acids 1-26 of SEQ ID NO: 3) and pep27 (amino acids 110-136 of SEQ ID NO: 3) were deleted during expression or when using the linker. The plasmid construction and expression / purification processes for these recombinant RSV F proteins are described in Examples 2 and 3. The specific design and screening process for the recombinant RSV F proteins were as follows: 1) Design and Screening of Linker between F2 and F1 By introducing a covalent linker between the C-terminus of F2 and the N-terminus of F1, the release of the fusion peptide could be prevented, thereby promoting the formation and stabilization of the pre-F conformation. Eight recombinant RSV F proteins were specifically synthesized, where: nRSVF0 was the wild-type RSV A2 F0 precursor polypeptide without a linker (SEQ ID NO: 1); nRSVF1 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 54), and the F1 fragment (amino acids 137-513 of SEQ ID NO: 1); nRSVF2 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 55), and the F1 fragment (amino acids 137-513 of SEQ ID NO: 1); nRSVF3 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 56), and the F1 fragment (amino acids 137-513 of SEQ ID NO: 1); nRSVF4 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 57), and the F1 fragment (amino acids 137-513 of SEQ ID NO: 1); nRSVF5 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 58), and the F1 fragment (amino acids 110-513 of SEQ ID NO: 1); nRSVF6 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 58), and the F1 fragment (amino acids 110-513 of SEQ ID NO: 1); wherein, compared to nRSVF5, nRSVF6 lacked the N-terminal 6 amino acids of the hydrophobic fusion peptide (FP) (amino acids 140-145 of SEQ ID NO: 1: FLLGVG); nRSVF7 was a recombinant RSV F protein comprising the F2 fragment (amino acids 1-105 of SEQ ID NO: 1), a linker (SEQ ID NO: 59), and the F1 fragment (amino acids 145-513 of SEQ ID NO: 1); As shown in Table 2, several different linkers were tried in this example. The effects of these recombinant RSV F proteins containing linkers were primarily evaluated by three indicators in Table 2: the first indicator characterized expression level by evaluating the binding strength of the recombinant RSV F protein to the co-reactive antibody palivizumab (expression level) of F protein, wherein higher value indicated higher expression level; the second indicator characterized whether the recombinant RSV F protein retained the pre-F conformation by evaluating the binding strength of the recombinant RSV F protein to the pre-F protein-specific antibody D25, wherein higher value indicated more retained pre-F; the third indicator calculated the relative proportion of pre-F protein in total F protein by calculating the ratio of D25 to palivizumab (i.e., D / P), wherein higher value indicated a higher proportion. Therein, the VH sequence of antibody D25 is set forth in SEQ ID NO: 40, and the VL sequence is set forth in SEQ ID NO: 41; the VH sequence of antibody palivizumab is set forth in SEQ ID NO: 42, and the VL sequence is set forth in SEQ ID NO: 43; the specific evaluation process is described in Example 4. Compared to F0 (SEQ ID NO: 3), the relative proportion of pre-F protein in several recombinant RSV F proteins containing different linkers was increased. The expression level of nRSVF6 was comparable to that of F0, and the pre-F proportion was also significantly increased. Although the expression level of nRSVF7 was lower than that of F0, it was still at a relatively high level, and its pre-F proportion was very effectively increased. In summary, the linker design schemes in nRSVF6 (SEQ ID NO: 4) and nRSVF7 (SEQ ID NO: 5) were more advantageous schemes. Table 2. Results of recombinant RSV F proteins No. Linker Palivizumab (Expression Level) D25 (Conformation) D / P nRSVFO None 2.713 0.345 0.13 nRSVF1 . .PATNNGGPGFLGFLL. 0.162 0.132 0.81 nRSVF2 . .PATNNGPGGGFLGFLL. 0.192 0.176 0.92 nRSVF3 .. .PATNNEAAAKFLGFLL... 0.082 0.075 0.91 nRSVF4 .. .PATNNPAAAKFLGFLL... 0.093 0.090 0.97 nRSVF5 .. .PATNNGGGELPRFMNYTLNN AKKTNVTLSKKRKRFLGFLL. 3.441 1.266 0.37 nRSVF6 . .PATNNGGGELPRFMNYTLNN AKKTNVTLSKKRKRFLGSAIA . 2.765 1.921 0.69 nRSVF7 .PATNNGGGPGGSAIA. 1.415 1.195 0.84 2) Introducing Point Mutation to Improve Expression Level and Pre-F Protein Proportion From the above example, it is known that nRSVF7 has a higher pre-F proportion and is a promising linker modification scheme, but its expression level still has room for optimization. Therefore, based on the F2 fragment, linker, and F1 fragment contained in nRSVF7, point mutations were introduced to try to alter the expression level of the protein. In this example, various mutation schemes were further designed to optimize the expression level of recombinant RSV F proteins. The relative positions of the mutation sites of these recombinant RSV F proteins were based on SEQ ID NO: 1. The specific recombinant RSV F proteins synthesized and the mutations they contain are shown in Table 3. The effects of the recombinant RSV F proteins carrying point mutations were evaluated using three indicators: expression level, binding strength to pre-F-specific antibody (D25), and pre-F proportion (D / P). The results showed that the mutations in nRSVF8, nRSVF11, nRSVF26, and nRSVF31 significantly increased the expression level of the recombinant RSV F protein, while nRSVF14 slightly increased the expression level. Furthermore, to increase the proportion of pre-F, based on the mutation sites corresponding to nRSVF8 (SEQ ID NO: 6), nRSVF11 (SEQ ID NO: 7), nRSVF14 (SEQ ID NO: 8), nRSVF26 (SEQ ID NO: 9), and nRSVF31 (SEQ ID NO: 10), mutation schemes for other amino acids were attempted. The specific mutation schemes and results are shown in Table 4. Most of the expanded mutations based on nRSVF26 and nRSVF11 resulted in a significant increase in expression level, indicating that the mutation sites contained in these two recombinant RSV F proteins had a greater impact on expression level. In summary, the recombinant RSV F proteins nRSVF31, nRSVF61 (SEQ ID NO: 11), nRSVF66 (SEQ ID NO: 12), and nRSVF67 (SEQ ID NO: 13) simultaneously retained the advantages of high expression level and high pre-F proportion. Table 3. Results of recombinant RSV F proteins No. Mutation Palivizumab (Expression level) D25 (Conformation) D / P nRSVF7 None 1.415 1.195 0.84 nRSVF8 S35Y 2.838 1.854 0.65 nRSVF9 E60Y 0.141 0.323 2.30 nRSVF10 G71T 0.184 0.258 1.41 nRSVF11 A298I 4.187 2.235 0.53 nRSVF12 N208L 0.209 0.079 0.38 nRSVF13 N227L 0.264 0.308 1.17 nRSVF14 S238L 1.940 0.238 0.12 nRSVF15 K42F 0.067 0.097 1.45 nRSVF16 S287V 0.170 0.142 0.83 nRSVF17 R49I 0.168 0.152 0.91 nRSVF18 H317F 0.262 0.178 0.68 nRSVF19 P320A 0.182 0.352 1.94 nRSVF20 T326D 0.195 0.213 1.09 nRSVF21 D344Y 0.186 0.266 1.43 nRSVF22 A346D 0.207 0.288 1.39 nRSVF23 S377P 0.133 0.154 1.16 nRSVF24 N380K 0.209 0.229 1.10 nRSVF25 S405V 0.154 0.257 1.67 nRSVF26 T189L 3.980 2.015 0.51 nRSVF27 N437R 0.235 0.330 1.40 nRSVF28 L481R 0.202 0.251 1.24 nRSVF29 N496F 0.243 0.361 1.49 nRSVF30 L512T 0.153 0.159 1.04 nRSVF31 S190I 3.882 3.195 0.82 nRSVF32 N88V 0.203 0.253 1.25 nRSVF33 E92I 0.250 0.505 2.02 nRSVF34 I79V 0.111 0.147 1.33 nRSVF35 G51W 0.062 0.082 1.33 nRSVF36 A74R 0.062 0.085 1.38 nRSVF37 L96W 0.147 0.142 0.96 nRSVF38 N104R 0.158 0.216 1.37 nRSVF39 G145W 0.220 0.297 1.35 nRSVF40 A149R 0.223 0.167 0.75 nRSVF41 E218R 0.538 0.446 0.83 nRSVF42 A241F 0.393 0.252 0.64 nRSVF43 N254R 0.269 0.392 1.46 nRSVF44 T455R 0.265 0.641 2.42 nRSVF45 Q202I 0.209 0.363 1.73 nRSVF46 E218N 0.389 0.475 1.22 nRSVF47 G151W 0.075 0.062 0.83 nRSVF48 G162P 0.069 0.036 0.51 nRSVF49 G242P 0.154 0.095 0.62 nRSVF50 D310P 0.040 0.047 1.18 nRSVF51 G340P 0.046 0.051 1.12 nRSVF52 G347P 0.057 0.095 1.65 nRSVF53 G411I 0.174 0.164 0.95 nRSVF54 G430P 0.410 0.052 0.13 nRSVF55 G438P 0.061 0.139 2.30 nRSVF56 G464F 0.063 0.107 1.71 Table 4. Results of recombinant RSV F proteins No. Mutation Palivizumab (Expression level) D25 (Conformation) D / P nRSVF8 S35Y 2.838 1.854 0.65 nRSVF57 S35F 0.219 0.397 1.82 nRSVF11 A298I 4.187 2.235 0.53 nRSVF58 A298H 3.653 0.515 0.14 nRSVF59 A298M 4.252 2.622 0.62 nRSVF60 A298P 0.032 0.026 0.81 nRSVF61 A298L 4.453 3.710 0.83 nRSVF14 S238L 1.940 0.238 0.12 nRSVF62 S238I 0.147 0.165 1.12 nRSVF63 S238T 2.200 0.522 0.24 nRSVF64 S238V 0.247 0.234 0.95 nRSVF26 T189L 3.980 2.015 0.51 nRSVF65 T189I 4.014 2.597 0.65 nRSVF66 T189V 3.276 2.668 0.81 nRSVF31 S190I 3.882 3.195 0.82 nRSVF67 S190L 4.026 3.331 0.83 nRSVF68 S190M 0.251 0.258 1.03 nRSVF69 S190V 0.201 0.323 1.61 nRSVF70 S190Y 0.222 0.329 1.49 3) Combined Mutations and Stability Testing In addition to protein expression level and pre-F proportion, stability is also a very important indicator for evaluating the quality of mutant proteins. Since the mutation in nRSVF61 significantly improved expression level and also had a high pre-F proportion, this recombinant RSV F protein was used as a basis to further add mutations and test the freeze-thaw stability and temperature stability of the resulting recombinant RSV F proteins. The stability of the recombinant RSV F proteins was evaluated by the retention binding rate of D25 after ten freeze-thaw cycles or after treatment at 60°C for 1 hour. A higher retention binding rate indicates better stability. The specific evaluation process for stability is described in detail in Example 5. As shown in Table 5, the recombinant RSV F proteins with combined mutants generally retained high freeze-thaw stability. In particular, the recombinant RSV F proteins nRSVF71 (SEQ ID NO: 14), nRSVF78, nRSVF79 (SEQ ID NO: 21), nRSVF80 (SEQ ID NO: 22), nRSVF82 (SEQ ID NO: 23), nRSVF83 (SEQ ID NO: 24), nRSVF105, and nRSVF109 to nRSVF116 had D25 retention binding rates greater than 0.9 after ten freeze-thaw cycles, demonstrating good freeze-thaw stability. The temperature stability was generally weaker than the freeze-thaw stability. Some recombinant RSV F proteins had a D25 retention binding rate below 0.5 after heat treatment at 60°C for one hour. However, nRSVF73 to nRSVF78 (SEQ ID NOs: 15-20), nRSVF94 (SEQ ID NO: 25), nRSVF96 (SEQ ID NO: 26), nRSVF100 (SEQ ID NO: 27), nRSVF105 (SEQ ID NO: 28), nRSVF106 (SEQ ID NO: 29), and nRSVF116 (SEQ ID NO: 37) had a D25 retention binding rate still greater than 0.8, demonstrating good thermal stability. nRSVF78, nRSVF105, and nRSVF116 simultaneously retained high freeze-thaw stability and thermal stability. Table 5. Results of recombinant RSV F proteins No. Mutation 1 Mutation 2 Freeze-thaw stability Temperature stability nRSVF71 A298L T189I 0.984 0.346 nRSVF72 A298L T189L 0.831 0.318 nRSVF73 A298L T189V 0.823 0.949 nRSVF74 A298L S190I 0.785 0.847 nRSVF75 A298L S190L 0.782 1.187 nRSVF76 A298L S190M 0.829 1.097 nRSVF77 A298L S190V 0.782 1.079 nRSVF78 A298L S190Y 0.903 0.967 nRSVF79 A298L N227L 0.951 0.579 nRSVF80 A298L S238I 0.938 0.405 nRSVF81 A298L S238L 0.803 0.615 nRSVF82 A298L S238T 0.900 0.584 nRSVF83 A298L S238V 0.984 0.560 nRSVF84 A298L P320A 0.847 0.601 nRSVF85 A298L P320F 0.754 0.734 nRSVF86 A298L P320H 0.797 0.623 nRSVF87 A298L P320I 0.767 0.668 nRSVF88 A298L P320K 0.751 0.545 nRSVF89 A298L P320L 0.833 0.388 nRSVF90 A298L P320M 0.853 0.486 nRSVF91 A298L P320N 0.826 0.797 nRSVF92 A298L P320Q 0.832 0.778 nRSVF93 A298L P320R 0.812 0.562 nRSVF94 A298L P320S 0.841 0.840 nRSVF95 A298L P320T 0.747 0.506 nRSVF96 A298L P320V 0.850 0.929 nRSVF97 A298L P320W 0.761 0.586 nRSVF98 A298L P320Y 0.758 0.670 nRSVF99 A298L T326D 0.786 0.741 nRSVF100 A298L T326E 0.759 0.840 nRSVF101 A298L T326P 0.764 0.665 nRSVF102 A298L S377P 0.866 0.669 nRSVF103 A298L S377Q 0.847 0.568 nRSVF104 A298L S405V 0.776 0.585 nRSVF105 A298L E60F 0.926 1.001 nRSVF106 A298L E60Y 0.758 0.960 nRSVF107 A298L N437R 0.748 0.363 nRSVF108 A298L N437Y 0.810 0.747 nRSVF109 A298L L481R 1.151 0.690 nRSVF110 A298L N496F 1.041 0.454 nRSVF111 A298L N496Y 1.098 0.410 nRSVF112 A298L E92T 1.032 0.412 nRSVF113 A298L E92V 1.070 0.363 nRSVF114 A298L E92M 1.039 0.324 nRSVF115 A298L E92I 1.083 0.228 nRSVF116 A298L I79L 0.948 0.864 4) Evaluation of trimeric pre-F proportion Although the degree of binding to D25 can characterize the proportion of pre-F, some monomeric forms of pre-F can also bind well to D25. It is unclear whether this monomeric form of pre-F impairs the immunogenicity of the recombinant RSV F protein. The binding effect of the recombinant RSV F proteins to the trimer-specific antibody AM14 (the VH sequence of antibody AM14 is set forth in SEQ ID NO: 44, and the VL sequence is set forth in SEQ ID NO: 45) was further evaluated. The specific evaluation process is described in Example 4. The results are shown in Table 6. Some recombinant RSV F proteins showed no binding to AM14 at all (<0.1), but nRSVF79 showed a very high ability to bind to AM14 (>3). In addition, nRSVF72 (SEQ ID NO: 38), nRSVF74, nRSVF78 to nRSVF80, nRSVF82, nRSVF83, and nRSVF112 to nRSVF116 also showed some binding to AM14 (>0.2, <1). Table 6. Results of recombinant RSV F proteins No. Mutation 1 Mutation 2 AM14 (trimer) nRSVF71 A298L T189I 0.016 nRSVF72 A298L T189L 0.623 nRSVF73 A298L T189V 0.02 nRSVF74 A298L S190I 0.211 nRSVF75 A298L S190L 0.124 nRSVF76 A298L S190M 0.173 nRSVF77 A298L S190V 0.088 nRSVF78 A298L S190Y 0.321 nRSVF79 A298L N227L 3.392 nRSVF80 A298L S238I 0.324 nRSVF81 A298L S238L 0.016 nRSVF82 A298L S238T 0.308 nRSVF83 A298L S238V 0.521 nRSVF84 A298L P320A 0.011 nRSVF85 A298L P320F 0.006 nRSVF86 A298L P320H 0.01 nRSVF87 A298L P320I 0.01 nRSVF88 A298L P320K 0.009 nRSVF89 A298L P320L 0.015 nRSVF90 A298L P320M 0.018 nRSVF91 A298L P320N 0.017 nRSVF92 A298L P320Q 0.032 nRSVF93 A298L P320R 0.01 nRSVF94 A298L P320S 0.024 nRSVF95 A298L P320T 0.008 nRSVF96 A298L P320V 0.007 nRSVF97 A298L P320W 0.006 nRSVF98 A298L P320Y 0.005 nRSVF99 A298L T326D 0.018 nRSVF100 A298L T326E 0.018 nRSVF101 A298L T326P 0.021 nRSVF102 A298L S377P 0.013 nRSVF103 A298L S377Q 0.017 nRSVF104 A298L S405V 0.022 nRSVF1O5 A298L E60F 0.081 nRSVF106 A298L E60Y 0.028 nRSVF107 A298L N437R 0.012 nRSVF108 A298L N437Y 0.005 nRSVF109 A298L L481R 0.018 nRSVF110 A298L N496F 0.009 nRSVF111 A298L N496Y 0.011 nRSVF112 A298L E92T 0.261 nRSVF113 A298L E92V 0.309 nRSVF114 A298L E92M 0.357 nRSVF115 A298L E92I 0.263 nRSVF116 A298L I79L 0.605 Example 2. Construction of Expression Vectors for Recombinant RSV F Proteins (F Protein Mutants) This example provides the specific experimental procedures carried out in Example 1, with the relevant experimental results presented in Example 1. The amino acid sequence of the precursor (nRSVF0) of the recombinant RSV F protein (hereinafter also referred to as F protein mutant) is set forth in SEQ ID NO: 3, which comprises a signal peptide (amino acid residues 1-25), an F2 polypeptide chain (amino acid residues 26-109), pep27 (amino acid residues 110-136), an F1 polypeptide chain (amino acid residues 137-513), a foldon domain (amino acid residues 518-544), a thrombin cleavage site (amino acid residues 547-552), a His purification tag (amino acid residues 553-558), and flexible linker sequences (amino acid residues 514-517, 545, 546). The amino acid sequence of SEQ ID NO: 3 was submitted to Genscript™ for mammalian codon optimization and synthesis. The synthesized gene fragment was inserted into the commercially available expression vector pcDNA3.1, which contained a CMV promoter and ampicillin resistance. Based on the amino acid sequence of nRSVF0, substitutions, insertions, or deletions of nucleotide sequences were performed using QuikChange® Lightning Site-Directed Mutagenesis Kits (Agilent, 210519) to obtain different F protein mutants. The target sequences of the F protein mutants were confirmed by DNA sequencing. Plasmids for transfection were extracted using an endotoxin-free plasmid maxi kit (TianGen, DP120), and DNA concentration and purity were determined by measuring OD260 and OD280 with a spectrophotometer. Plasmids were stored at -20°C. All commercial reagents were used according to the manufacturer's instructions. Example 3. Expression and Purification of Recombinant RSV F Proteins (F Protein Mutants) This example provides the specific experimental procedures carried out in Example 1, with the relevant experimental results presented in Example 1. Fig. 2 exemplarily shows the SDS-PAGE results of nRSVF79 protein and nRSVF116 protein, wherein, M: protein marker; reducing: under reducing conditions; non-reducing: under non-reducing conditions. Suspension ExpiCHO™ cells in the logarithmic growth phase were prepared and cultured in a cell shaker at 125 rpm, 37°C, 8% CO2 until the density reached 6*106 cells / mL with a viability >98%. 25 mL of the cells were taken and placed in a new cell culture flask as one transfection system. Tube A: 1 mL of ExpiCHO™ Expression Medium containing 25 pg of plasmid; Tube B: 1 mL of ExpiCHO™ Expression Medium containing 80 pL of transfection reagent from ExpiFectamine™ CHO Transfection Kit (Thermo Scientific, Cat. No.: A29129). The contents of Tube A and Tube B were mixed and allowed to stand at room temperature for 2 min. After 2 min, the mixture was poured into the prepared 25 mL cell transfection system. The cells were cultured in a cell shaker at 125 rpm, 37°C, 8% CO2 for 18 to 22 hours. 150 pL of enhancer and 4 mL of supplement from the ExpiFectamine™ CHO Transfection Kit were added to each flask, and the cells were cultured in a cell shaker at 125 rpm, 32°C, 5% CO2 for 8 to 15 days. After culture, the cells were centrifuged at 4000 rpm for 10 min at 4°C, and the cell supernatant was collected. The above supernatant was filtered through a 0.22 pm filter. The AKTA instrument was turned on, and the A line and B line were first rinsed with Buffer A (200 mM disodium hydrogen phosphate dodecahydrate) and Buffer B (100 mM citric acid monohydrate), respectively. The Protein A column was then mounted. The column was equilibrated with Buffer A at a flow rate of 8 mL / min for more than 15 min, and the next step was proceeded only after the UV value, pH, and conductivity detected by the instrument had stabilized. The sample was loaded at a flow rate of 6 to 10 mL / min, after which the UV value was observed to rise. This peak was identified as the flow-through peak, and the column was continued to be washed with Buffer A while the flow-through peak fractions were collected for later testing. After the pH had ceased to change, Buffer B was introduced at a flow rate of 6 to 10 mL / min, following which the pH was decreased and the UV value was increased, and this peak was identified as the elution peak, while the antibody was mainly found in this elution peak. The elution peak fractions were collected for later testing. The column was equilibrated with Buffer A, and then the line and the Protein A column were filled with 20% ethanol. The column was removed and stored at 4°C. The flow-through peak and elution peak samples were purified, and their concentrations were determined by ultraviolet spectrophotometry. Example 4. Analysis of Expression Level and Epitope Characteristics of Recombinant RSV F Proteins (F Protein Mutants) This example provides the specific experimental procedures carried out in Example 1, with the relevant experimental results presented in Example 1. Five days after transfection, aliquots of the transfection supernatants from F protein mutant plasmids were collected. Cell debris was removed by low-speed centrifugation, and the binding of the expression supernatants to palivizumab, D25, or AM14 (sequence) was detected using a Nickel Coated plate (PIERCE, 15442). The nickel-coated plate was first washed once with PBST (20 mM PB pH 7.4, 150 mM NaCl, 0.1% Tween 20). The expression supernatants were diluted 5-fold with blank cell culture supernatant, and then 100 pL of the diluted sample was taken and added to the nickel-coated plate, which was incubated at 37°C for 60 minutes. The detection antibodies were diluted to a concentration of 2.5 pg / mL with 2% non-fat dry milk (Wondersun). The nickel-coated plate was washed five times with PBST wash buffer, and then 100 pL of the diluted detection antibody was added to each well, followed by incubation at 37°C for 60 minutes. The nickel-coated plate was washed five times with PBST wash buffer, and then 100 pL of horseradish peroxidase (HRP)-conjugated goat anti-human IgG (Abcam, ab97225) reaction solution was added to each well, which was incubated at 37°C for 30 minutes. After the enzyme conjugate reaction step was completed, the plate was washed five times with PBST wash buffer, and then 50 pL of TMB color developing agent (purchased from Beijing Wantai Biological Pharmacy Enterprise Co., Ltd.) was added to each well, followed by incubation at 37°C for 15 minutes. After the color development step was completed, 50 pL of stop solution (purchased from Beijing Wantai Biological Pharmacy Enterprise Co., Ltd.) was added to each well of the reacted plate, and the OD450 / 630 values of each well were measured on a microplate reader. The expression level was represented by the absorbance value of palivizumab, the pre-F content was represented by the absorbance value of D25, the trimer content was represented by the absorbance value of AM14, and the D / P ratio was obtained by dividing the absorbance value of D25 by the absorbance value of palivizumab. Example 5. Stability Analysis of Recombinant RSV F Proteins (F Protein Mutants) This example provides the specific experimental procedures carried out in Example 1, with the relevant experimental results presented in Example 1. Five days after transfection, aliquots of the transfection supernatant containing the F protein mutant plasmids were collected. Cell debris was removed by low-speed centrifugation, after which the supernatants were subjected to either freeze-thaw cycling or heat treatment. For the freeze-thaw test, the transfected supernatants were frozen in a dry ice-ethanol mixture and then rapidly thawed in a 37°C water bath; this procedure was repeated ten times. For the thermal stability testing, the transfected supernatants were placed in a 60°C water bath for one hour. Untreated samples were kept on ice-water at 4°C and served as controls. The D25 retention binding rate was obtained by testing the cell supernatant before and after treatment in a palivizumab-coated plate. The specific method was as follows: palivizumab at a concentration of 2.5 pg mL was added to blank ELISA plates at a volume of 100 pL per well, and the plates were incubated at 37°C for 60 minutes, and washed 5 times with PBST. Then, 200 pL of 5% non-fat dry milk was added to each well, and the plates were blocked at 37°C for 2 hours. After blocking reaction was completed, the plates were washed five times with PBST, and 100 gL of biotinylated D25 antibody was added to each well, followed by incubation at 37°C for 60 minutes. After the reaction was completed, the plates were washed five times with PBST, and 100 gL of streptavidin Poly-HRP Streptavidin (PIERCE, N200) was added to each well, followed by incubation at 37°C for 1 hour. After the reaction steps were completed, the plates were washed five times with PBST wash buffer, and 50 gL of TMB color developing agent (purchased from Beijing Wantai Biological Pharmacy Co., Ltd.) was added to each well, after which the plates were incubated in a incubator at 37°C for 15 minutes. After the color development reaction step was completed, 50 gL of stop solution (purchased from Beijing Wantai Biological Pharmacy Co., Ltd.) was added to each well, and the OD450 / 630 values of each well were read on a microplate reader. The retention binding rate of D25 was calculated as the ratio of the absorbance of the supernatant after freeze-thaw treatment or heat treatment to the absorbance of the untreated supernatant. Example 6. Affinity Analysis of Recombinant RSV F Proteins (Mutated F Proteins) with Antibody Panel The binding affinities of F protein mutants to F protein-specific antibodies palivizumab, D25, AM14, and hRSV90 were determined by surface plasmon resonance (SPR) analysis. The His-tagged F protein mutant was immobilized onto an NTA sensor chip (Cytiva) at a concentration of approximately 100 nM using a Biacore-8K (Cytiva). Serially diluted antibodies (concentrations ranging from 200 to 0.78 nM) were then added. The RU data were fitted to a 1:1 binding model using the BiacoreTM Insight software. The affinity results for some exemplary F protein mutants are shown in Table 7. These F protein mutants containing single point mutations or double point mutations had affinity at nanomolar or picomolar level for the co-reactive antibody palivizumab, demonstrating that the mutants could fold and express correctly. Furthermore, these mutants also had good affinity for the pre-F-specific antibodies D25, AM14, and hRSV90, demonstrating that introducing these single point mutations or double point mutations, or any combination thereof, could have a similar or stronger effect on stabilizing the pre-F structure. Table 7. Affinity analysis of recombinant RSV F proteins with antibodies No. KD (nM) palivizumab D25 AM14 hRSV90 nRSVF13 0.008 0.13 0.24 0.024 nRSVF61 0.019 0.056 0.83 0.044 nRSVF64 0.025 0.089 0.13 0.091 nRSVF71 0.022 0.044 1.2 0.096 nRSVF72 0.074 0.11 0.08 0.067 nRSVF78 0.027 0.091 0.12 0.045 nRSVF79 0.031 0.043 0.02 0.013 nRSVF83 0.035 0.025 0.09 0.086 nRSVF114 0.009 0.076 0.24 0.12 nRSVF116 0.011 0.023 0.045 0.077 Example 7. Thermal Stability Testing of Recombinant RSV F Proteins (F Protein Mutants) by Differential Scanning Fluorimetry The thermal stability of F protein mutants was analyzed using Differential Scanning Fluorimetry (DSF). First, the test protein sample was diluted to a concentration of 1 mg / mL with sterile PBS solution. A 2-fold serial dilution was performed for 8 gradients to determine the appropriate sample concentration. Blank PBS was used as a control. The dye SYPRO Orange (Sigma-Aldrich, Cat. No.: S5692-500UL) was diluted with deionized water to a final concentration of 50X. 45 pL of the diluted test protein sample was added to a Bio-Rad PCR plate, followed by 5 pL of 50X SYPRO Orange dye. The above prepared system was placed in a real-time PCR instrument (BIO-RAD). The excitation and emission wavelengths were set to the corresponding wavelengths for the fluorescent dye. The heating rate was set to 0.5°C / 10 s, and the temperature range was from 0°C to 100°C. BIO-RAD manager software was used to process the data, plot the fluorescence intensity as a function of temperature, and calculate the Tm value of the protein sample by fitting the Boltzmann transport equation (BTE). The experimental results are shown in Fig. 3. Several exemplary F protein mutants had similar unfolding temperatures, with Tm values ranging from 56°C to 60°C. Among them, the Tm temperatures of nRSVF61 and nRSVF116 reached 57.8°C and 59.3°C, respectively. This indicated that introducing these single point mutations or double point mutations, or any combination thereof, enabled the F protein to have good thermal stability. Example 8. Immunogenicity Analysis of Recombinant RSV F Proteins (F Protein Mutants) 1) Mouse Immunization Experiment The care and experimental manipulation of the experimental animals were carried out according to the procedures established by the Laboratory Animal Use and Care Committee of Xiamen University. The experimental animals were BALB / c female mice, 6-8 weeks old, purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd., and housed in the Laboratory Animal Center of Xiamen University. The immunization protocol was designed by mixing each of the 10 F protein mutants, along with the control proteins pre-F and post-F proteins, with aluminum adjuvant at a 1:1 volume ratio, and the mixtures were used to immunize mice. The pre-F and post-F proteins used for immunization were constructed as follows: the sequences of pre-F and post-F proteins were downloaded from GenBank (GenBank ID: LY628284.1, GenBank ID: 6APB_A), and the nucleotide sequences encoding the two proteins were cloned into the pcDNA3.1 eukaryotic expression vector. They were expressed using the CHO eukaryotic expression system, and the pre-F protein (SEQ ID NO:52) and post-F protein (SEQ ID NO:53) were purified by affinity chromatography, with the steps carried out consistently as described in Example 2 and Example 3. Each group consisted of 6 mice, and the immunization was performed by unilateral intramuscular injection into the thigh, with a dose of 2 pg protein / mouse. A two-dose immunization regimen was administered, and on day 14 after the booster immunization, orbital blood was collected from the mice, and sera were separated. The serum samples were inactivated at 56°C for 30 minutes and were then stored at 4°C for later use. (2) Evaluation of Pre-F-Specific Antibody Titers in Serum The pre-F protein used for coating was constructed as described above. On the first evening, the pre-F protein was diluted with PBS and coated onto a 96-well plate at 100 ng / well, and allowed to stand overnight at 4°C. The coating protein solution was discarded, and the plate was washed once with PBST. Blocking solution containing 5% fetal bovine serum was added at an amount of 200 pl / well, and the plate was placed at 37°C for 2 hours. The blocking solution was discarded, and the plate was washed once with PBST. Serially diluted mouse serum (first well 200-fold, 5-fold gradient) was added at 100 pL / well, and the plate was incubated at 37°C for 1 hour. The serum dilutions were discarded, and the plate was washed five times with PBST. Horse radish peroxidase-labeled goat anti-mouse IgG antibody (Abcam, ab97265) diluted 1:5000 was added at 100 pl / well, and the plate was incubated at 37°C for 1 hour. The secondary antibody was discarded, and the plate was washed five times with PBST. Color developing agent solution was added at 100 pl / well, and the plate was incubated at room temperature in the dark for 10 minutes. Stop solution was added at 50 pl / well, and the absorbance values at OD450 / 630 were measured using a microplate reader. The criterion for determining the endpoint titer was 3 times the reading of the negative control wells. The experimental results are shown in Fig. 4. The F protein mutants containing single point mutations or double point mutations all could induce pre-F-binding antibody titers comparable to those of the pre-F control protein, and the pre-F-binding antibody titers of these mutants were approximately 100 times higher than those of the post-F protein. This indicated that when single point mutations or double point mutations are introduced, the F protein could be maintained in the pre-F conformation, and this conformation was also stable in animals. (3) Evaluation of Serum Neutralizing Antibody Titers Serum was serially diluted: the first well 10-fold, then 4-fold gradient dilution for a total of 10 gradients. An equal volume of rRSV-mkatushka2 (MOI=0.1) was then added, mixed, and incubated at 37°C for 1 hour. The serum-virus mixture was transferred at a volume of 100 pL / well to a 96-well plate seeded with a monolayer of HeLa cells, and the plate was incubated at 37°C. Virus control wells containing no serum were set as negative controls. After 24 hours of culture, the plate was read using a SpectraMax Paradigm Multi-Mode Microplate Reader. The neutralizing antibody titer of the serum was defined as the highest serum dilution at which the mean fluorescence intensity was less than 50% of that in the negative control wells. The experimental results are shown in Fig. 5. When certain stabilizing single point mutations were introduced, the average neutralizing antibody titers reached approximately 200, which were about 5 times higher than that of the post-F control protein. When double point mutations were introduced, the neutralizing antibody titers of most mutants reached above 500, indicating that combined mutations had a greater advantage in stabilizing the conformation of the pre-F protein in animals. These immunogens, with single point mutations or double point mutations, all had good immunogenicity effects and can provide strong candidate antigens for the development of RSV recombinant protein vaccines. Although the specific embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and variations can be made to the details based on all the teachings disclosed, and such changes are within the scope of the present invention. The full scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. A recombinant respiratory syncytial virus (RSV) fusion (F) protein, comprising the F2 domain and F1 domain of a wild-type RSV F protein; and, compared to the wild-type RSV F protein, further comprising at least one amino acid mutation that stabilizes the pre-fusion (pre-F) conformation of the RSV F protein.

2. The recombinant RSV F protein according to claim 1, which has one or more characteristics selected from the following compared to the wild-type RSV F protein:(1) having increased stability; preferably, the stability is measured by the binding of the recombinant RSV F protein to antibody D25;(2) having a higher proportion of pre-F protein;preferably, the recombinant RSV F protein comprises pre-fusion conformation (pre-F) protein, post-fusion conformation (post-F) protein, or a mixture thereof;preferably, the proportion of pre-F protein is measured by the ratio of antibody D25 to antibody palivizumab bound to the recombinant RSV F protein;(3) having a higher protein expression level;(4) comprising an insertion, deletion, and / or mutation of one or more amino acids;(5) the position of the amino acid mutation comprised in the recombinant RSV F protein is selected from any one or more of the following: positions corresponding to positions 35, 60, 79, 92, 189, 190, 227, 238, 298, 320, 326, 377, 405, 437, 481, and 496 of the wild-type RSV F protein;(6) lacking at least one furin cleavage site, or lacking one or more amino acids in a furin cleavage site;(7) lacking one or more (e.g., 1-5, 5-10, 10-15, 15-20, 20-27) amino acids of pep27 domain.

3. The recombinant RSV F protein according to claim 1 or 2, wherein the wild-type RSV is a subtype A strain, a subtype B strain, or a strain derived from subtype A or subtype B;preferably, the wild-type RSV is selected from strain A2, strain Ontario, strain Buenos Aires, or strain B18537;preferably, the wild-type RSV F protein comprises a sequence selected from the following, or consists of a sequence selected from the following:(i) the sequence as set forth in SEQ ID NO: 1, 2, or 64;(ii) a sequence having a substitution, deletion, and / or addition of one or more amino acids (e.g., a substitution, deletion, and / or addition of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids) compared to the sequence as set forth in SEQ ID NO: 1, 2, or 64;(iii) a sequence having at least 90% (e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%) sequence identity to the sequence as set forth in SEQ ID NO: 1, 2, or 64.

4. The recombinant RSV F protein according to any one of claims 1 to 3, comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more amino acid mutations compared to the wild-type RSV F protein;preferably, the position of the amino acid mutation comprised in the recombinant RSV F protein is selected from: positions corresponding to positions 35, 189, 190, 227, 238, or 298 of the wild-type RSV F protein;preferably, the position of the amino acid mutation comprised in the recombinant RSV F protein is the position corresponding to position 298 of the wild-type RSV F protein; and one or more positions selected from: positions corresponding to positions 60, 79, 92, 189, 190, 227, 238, 320, 326, 377, 405, 437, 481, and 496 of the wild-type RSV F protein.

5. The recombinant RSV F protein according to any one of claims 1 to 4, which has one or more characteristics selected from the following:(1) the amino acid at position corresponding to position 35 of the wild-type RSV F protein in the recombinant RSV F protein is Y or F;preferably, the amino acid mutation at position 35 is a S to Y or F mutation;(2) the amino acid at position corresponding to position 298 of the wild-type RSV F protein in the recombinant RSV F protein is I, H, M, P, or L;preferably, the amino acid mutation at position 298 is an A to I, H, M, P, or L mutation;(3) the amino acid at position corresponding to position 238 of the wild-type RSV F protein in the recombinant RSV F protein is L, I, T, or V;preferably, the amino acid mutation at position 238 is an S to L, I, T, or V mutation;(4) the amino acid at position corresponding to position 189 of the wild-type RSV F protein in the recombinant RSV F protein is L, I, or V;preferably, the amino acid mutation at position 189 is a T to L, I, or V mutation;(5) the amino acid at position corresponding to position 190 of the wild-type RSV F protein in the recombinant RSV F protein is I, L, M, V, or Y;preferably, the amino acid mutation at position 190 is an S to I, L, M, V, or Y mutation;(6) the amino acid at position corresponding to position 227 of the wild-type RSV F protein in the recombinant RSV F protein is L;preferably, the amino acid mutation at position 227 is an N to L mutation;(7) the amino acid at position corresponding to position 320 of the wild-type RSV F protein in the recombinant RSV F protein is A, F, H, I, K, L, M, N, Q, R, S, T, V, W, or Y;preferably, the amino acid mutation at position 320 is a P to A, F, H, I, K, L, M, N, Q, R, S, T, V, W, or Y mutation;(8) the amino acid at position corresponding to position 326 of the wild-type RSV F protein in the recombinant RSV F protein is D, E, or P;preferably, the amino acid mutation at position 326 is a T to D, E, or P mutation;(9) the amino acid at position corresponding to position 377 of the wild-type RSV F protein in the recombinant RSV F protein is P or Q;preferably, the amino acid mutation at position 377 is an S to P or Q mutation;(10) the amino acid at position corresponding to position 405 of the wild-type RSV F protein in the recombinant RSV F protein is V;preferably, the amino acid mutation at position 405 is an S to V mutation;(11) the amino acid at position corresponding to position 60 of the wild-type RSV F protein in the recombinant RSV F protein is F or Y;preferably, the amino acid mutation at position 60 is an E to F or Y mutation;(12) the amino acid at position corresponding to position 437 of the wild-type RSV F protein in the recombinant RSV F protein is R or Y;preferably, the amino acid mutation at position 437 is an N to R or Y mutation;(13) the amino acid at position corresponding to position 481 of the wild-type RSV F protein in the recombinant RSV F protein is R;preferably, the amino acid mutation at position 481 is an L to R mutation;(14) the amino acid at position corresponding to position 496 of the wild-type RSV F protein in the recombinant RSV F protein is F or Y;preferably, the amino acid mutation at position 496 is an N to F or Y mutation;(15) the amino acid at position corresponding to position 92 of the wild-type RSV F protein in the recombinant RSV F protein is T, V, M, or I;preferably, the amino acid mutation at position 92 is an E to T, V, M, or I mutation;(16) the amino acid at position corresponding to position 79 of the wild-type RSV F protein in the recombinant RSV F protein is L;preferably, the amino acid mutation at position 79 is an I to L mutation.

6. The recombinant RSV F protein according to any one of claims 1 to 5, wherein there is no furin cleavage site and / or pep27 domain between the F2 domain and the F1 domain;preferably, the F2 domain has one or more characteristics selected from the following:(1) the F2 domain comprises the complete F2 domain of the wild-type RSV F protein (e.g., a portion corresponding to positions 1-109 of the wild-type RSV F protein) or a fragment thereof;(2) the F2 domain comprises a portion corresponding to positions 1-95, 5-95, 10-95, 1-100, 5-100, 10-100, 1-105, 5-105, 10-105, 1-110, 5-110, or 10-110 of the wild-type RSV F protein;(3) the F2 domain comprises a portion corresponding to positions 1-105 of the wild-type RSV F protein;(4) the F2 domain has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more amino acid residues deleted from the N-terminus and / or C-terminus compared to the F2 domain of the wild-type RSV F protein;for example, the F2 domain has 5 or 25 amino acids deleted from the N-terminus and 4 amino acids deleted from the C-terminus compared to the F2 domain of the wild-type RSV F protein;preferably, the F1 domain has one or more characteristics selected from the following:(1) the F1 domain comprises the complete F1 domain of the wild-type RSV F protein (e.g., a portion corresponding to positions 137-574 of the wild-type RSV F protein) or a fragment thereof;(2) the F1 domain comprises the ectodomain, transmembrane domain, and / or cytoplasmic tail of the wild-type RSV F protein;(3) the F1 domain comprises a portion corresponding to positions 135-503, 140-503, 145-503, 135-508, 140-508, 145-508, 135-513, 140-513, 145-513, 135-518, 140-518, or 145-518 of the wild-type RSV F protein;(4) the F1 domain comprises a portion corresponding to positions 145-513 of the wild-type RSV F protein;(5) the F1 domain has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more (e.g., 30-50, 50-100, 100-150, 150-200, 200-250, 250-300) amino acid residues deleted from the N-terminus and / or C-terminus compared to the F1 domain of the wild-type RSV F protein;for example, the F1 domain has 8 amino acids deleted from the N-terminus and 252 or 268 amino acids deleted from the C-terminus compared to the F1 domain of the wild-type RSV F protein.

7. The recombinant RSV F protein according to any one of claims 1 to 6, wherein the recombinant RSV F protein further comprises a linker;preferably, the linker is located at the C-terminus of the F2 domain;preferably, the linker is located at the N-terminus of the F1 domain;preferably, the linker has 3 to 20 (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 15, 20) amino acids;preferably, the linker comprises at least 1 (e.g., 1, 2, 3, 4, 5, 6, 7) glycine;preferably, the linker further comprises at least 1 (e.g., 1, 2, 3) proline;preferably, the linker comprises a sequence selected from the following, or consists of a sequence selected from the following: the sequence as set forth in any one of SEQ ID NOs: 54-59.

8. A fusion protein, which comprises the recombinant RSV F protein according to any one of claims 1 to 7, wherein the fusion protein further comprises an additional protein or polypeptide;preferably, the additional protein or polypeptide is selected from the group consisting of: signal peptide, multimerization domain, tag, or any combination thereof.

9. The fusion protein according to claim 8, wherein the signal peptide has one or more characteristics selected from the following:(1) the signal peptide is a native signal peptide of RSV or a variant thereof, or a native signal peptide derived from another organism or a variant thereof;(2) the signal peptide is located at one end (e.g., the N-terminus) of the fusion protein;(3) the signal peptide is located at the N-terminus of the F2 domain;(4) the signal peptide is linked to the F2 domain with or without a first linking peptide.

10. The fusion protein according to claim 8 or 9, wherein the multimerization domain has one or more characteristics selected from the following:(1) the multimerization domain is a dimerization domain, a trimerization domain, a tetramerization domain, or a pentamerization domain;(2) the multimerization domain is derived from T4 phage fibritin (T4 fibritin);preferably, the multimerization domain has the sequence as set forth in SEQ ID NO: 39;(3) the multimerization domain is a leucine zipper or an isoleucine zipper;preferably, the multimerization domain has the sequence as set forth in SEQ ID NO: 60;(4) the multimerization domain is derived from pulmonary surfactant protein;(5) the multimerization domain is located at the C-terminus of the F1 domain;(6) the multimerization domain is linked to the F1 domain with or without a second linking peptide;preferably, the second linking peptide has the sequence as set forth in SEQ ID NO: 61.

11. The fusion protein according to any one of claims 8 to 10, wherein the tag has one or more characteristics selected from the following:(1) the tag is selected from the group consisting of polyhistidine tag, antigenic or epitope tag, enzyme tag, or any combination thereof;(2) the tag is located at the terminus (e.g., C-terminus) of the fusion protein;(3) the tag is located at the C-terminus of the F1 domain or the multimerization domain;(4) the tag is linked to the F1 domain or the multimerization domain with or without a third linking peptide.

12. The fusion protein according to any one of claims 8 to 11, wherein the fusion protein comprises sequentially from N-terminus to C-terminus: the F2 domain, a linker, the F1 domain;preferably, the fusion protein comprises sequentially from N-terminus to C-terminus: the F2 domain, a linker, the F1 domain, a multimerization domain; optionally, the multimerization domain is linked to the F1 domain with or without a second linking peptide;preferably, the fusion protein comprises sequentially from N-terminus to C-terminus: the F2 domain, a linker, the F1 domain, a second linking peptide, a multimerization domain; optionally, the fusion protein comprises or does not comprise a tag at its C-terminus; optionally, the fusion protein comprises or does not comprise a signal peptide at its N-terminus;preferably, the fusion protein has:(i) a sequence as set forth in any one of SEQ ID NOs: 4-38;(ii) a sequence having a substitution, deletion, and / or addition of one or more amino acids (e.g., a substitution, deletion, and / or addition of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids) compared to the sequence as set forth in any one of SEQ ID NOs: 4-38;(iii) a sequence having at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.5% sequence identity to the sequence as set forth in any one of SEQ ID NOs: 4-38;preferably, the fusion protein is in the form of a multimer (e.g., dimer, trimer, tetramer), a monomer, or a mixture thereof;preferably, the fusion protein is in the pre-fusion conformation (pre-F), the post-fusion conformation (post-F), or a mixture thereof.

13. A nucleic acid molecule, which comprises a nucleotide sequence encoding the recombinant RSV F protein according to any one of claims 1 to 7 or the fusion protein according to any one of claims 8 to 12;preferably, the nucleotide sequence has been codon-optimized or not optimized according to the codon preference of a host cell;preferably, the nucleic acid molecule is DNA, or an RNA (mRNA) product transcribed from the DNA, or a mixture thereof.

14. A vector, which comprises the nucleic acid molecule according to claim 13;preferably, the vector is a viral vector;preferably, the viral vector is selected from the group consisting of: influenza virus vector, retrovirus vector, adenovirus vector, adeno-associated virus vector, herpesvirus vector, poxvirus vector, baculovirus vector, papillomavirus vector, or papovavirus vector.

15. A host cell, which comprises the recombinant RSV F protein according to any one of claims 1 to 7, or the fusion protein according to any one of claims 8 to 12, or the nucleic acid molecule according to claim 13, or the vector according to claim 14;preferably, the host cell is selected from prokaryotic cell (e.g., Escherichia coli cell) or eukaryotic cell;preferably, the eukaryotic cell is a mammalian cell, such as a mouse cell or a human cell;preferably, the recombinant RSV F protein or fusion protein is displayed on the surface of the cell membrane of the host cell.

16. A method for expressing or producing the recombinant RSV F protein according to any one of claims 1 to 7 or the fusion protein according to any one of claims 8 to 12, the method comprising culturing the host cell according to claim 15 under a condition that allows expression of the protein, and optionally, recovering or purifying the recombinant RSV F protein or fusion protein expressed by the host cell.

17. A vaccine, which comprises one or more selected from the following (1) to (4):(1) the recombinant RSV F protein according to any one of claims 1 to 7;(2) the fusion protein according to any one of claims 8 to 12;(3) the nucleic acid molecule according to claim 13;(4) the vector according to claim 14;preferably, the vaccine further comprises an adjuvant and / or a buffer;preferably, the adjuvant is selected from the group consisting of metal salt, 3-D-monophosphoryl lipid A (MPL), saponin, oil and water emulsion, liposome, nanoparticle, or any combination thereof;preferably, the fusion protein in the vaccine is in the form of a multimer (e.g., dimer, trimer, tetramer), a monomer, or a mixture thereof;preferably, the recombinant RSV F protein or fusion protein in the vaccine is in the pre-fusion conformation (pre-F), the post-fusion conformation (post-F), or a mixture thereof.

18. An immunogenic composition, comprising:(i) a first immunogenic component, wherein the first immunogenic component is selected from one or more of the following (1) to (4):(1) the recombinant RSV F protein according to any one of claims 1 to 7;(2) the fusion protein according to any one of claims 8 to 12;(3) the nucleic acid molecule according to claim 13;(4) the vector according to claim 14; and(ii) a second immunogenic component.

19. The immunogenic composition according to claim 18, wherein the immunogenic composition has one or more characteristics selected from the following:(1) the first immunogenic component and the second immunogenic component are each independently selected from the group consisting of protein component, nucleic acid component, or any combination thereof;(2) the second immunogenic component is an immunogen derived from another strain of RSV;for example, the first immunogenic component is an immunogen derived from an RSV subtype A strain, and the second immunogenic component is an immunogen derived from an RSV subtype B strain;(3) the second immunogenic component is an immunogen derived from another protein of RSV;for example, the first immunogenic component is an immunogen derived from RSV F protein, and the second immunogenic component is an immunogen derived from RSV attachment protein (G) protein or RSV small hydrophobic protein (SH) protein;(4) the second immunogenic component is an immunogen derived from a pathogenic organism different from RSV;for example, the first immunogenic component is an immunogen derived from RSV, and the second immunogenic component is an immunogen derived from a virus different from RSV (e.g., hepatitis B virus (HBV), parainfluenza virus (PIV), poliovirus, influenza virus);(5) the first immunogenic component and the second immunogenic component are formulated for simultaneous or separate administration;(6) the immunogenic composition further comprises more immunogenic components (e.g., a third immunogenic component, a fourth immunogenic component, and / or a fifth immunogenic component).

20. A kit, which comprises an immunogenic component, wherein the immunogenic component is selected from one or more of the following (1) to (4): (1) the recombinant RSV F protein according to any one of claims 1 to 7; (2) the fusion protein according to any one of claims 8 to 12; (3) the nucleic acid molecule according to claim 13; (4) the vector according to claim 14;preferably, the kit further comprises a carrier component capable of displaying the immunogenic component;preferably, the carrier component is selected from the group consisting of: nanomaterial (e.g., lipid nanoparticle, protein nanoparticle, polymer nanoparticle, inorganic nanocarrier, and biomimetic nanoparticle), bacterial outer membrane vesicles (OMVs), multimerization scaffold, virus-like particle (VLP), or any combination thereof;preferably, the immunogenic component and the carrier component in the kit are provided separately, or provided as a complex;preferably, the immunogenic component is in the form of a multimer (e.g., dimer, trimer, tetramer), a monomer, or a mixture thereof;preferably, the immunogenic component in the kit is provided in protein or nucleic acid form;preferably, the carrier component in the kit is provided in protein or nucleic acid form;preferably, the VLP is assembled from proteins obtained from RSV, hepatitis B virus (HBV), human papillomavirus (HPV), or human immunodeficiency virus (HIV).

21. A pharmaceutical composition, comprising:(i) any one or more selected from the following (1) to (8):(1) the recombinant RSV F protein according to any one of claims 1 to 7;(2) the fusion protein according to any one of claims 8 to 12;(3) the nucleic acid molecule according to claim 13;(4) the vector according to claim 14;(5) the host cell according to claim 15;(6) the vaccine according to claim 17;(7) the immunogenic composition according to claim 18 or 19;(8) the kit according to claim 20; and(ii) a pharmaceutically acceptable carrier, excipient, buffer, adjuvant, or any combination thereof;preferably, the pharmaceutical composition may further comprise an additional active ingredient; for example, an additional vaccine, antiviral agent, and / or monoclonal antibody;preferably, the additional vaccine, antiviral agent, and / or monoclonal antibody is an additional vaccine, antiviral agent, and / or monoclonal antibody against RSV; or a vaccine, antiviral agent, and / or monoclonal antibody against a pathogenic organism other than RSV.

22. Use of the recombinant RSV F protein according to any one of claims 1 to 7, or the fusion protein according to any one of claims 8 to 12, or the nucleic acid molecule according to claim 13, or the vector according to claim 14, or the host cell according to claim 15, or the vaccine according to claim 17, or the immunogenic composition according to claim 18 or 19, or the kit according to claim 20, in the manufacture of a pharmaceutical composition for inducing an immune response against RSV in a subject;preferably, the immune response comprises inducing the production of an antibody against RSV (e.g., neutralizing antibodies) in the subject;preferably, the subject is a mammal, e.g., a mouse, a human;preferably, the subject is selected from the group consisting of infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus.

23. Use of the recombinant RSV F protein according to any one of claims 1 to 7, or the fusion protein according to any one of claims 8 to 12, or the nucleic acid molecule according to claim 13, or the vector according to claim 14, or the host cell according to claim 15, or the vaccine according to claim 17, or the immunogenic composition according to claim 18 or 19, or the kit according to claim 20, in the manufacture of a pharmaceutical composition for preventing and / or treating RSV infection or a disease and / or symptom caused by RSV infection;preferably, the subject is a mammal, e.g., a mouse, a human;preferably, the subject is selected from the group consisting of infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus;preferably, the disease and symptom caused by RSV infection is selected from the group consisting of bronchitis, pneumonia, asthma, obstructive pulmonary disease, and cardiopulmonary complication.

24. A method for inducing an antibody against RSV, the method comprising administering an effective amount of the recombinant RSV F protein according to any one of claims 1 to 7, or the fusion protein according to any one of claims 8 to 12, or the nucleic acid molecule according to claim 13, or the vector according to claim 14, or the host cell according to claim 15, or the vaccine according to claim 17, or the immunogenic composition according to claim 18 or 19, or the kit according to claim 20, in a cell in vitro or in a subject;preferably, the mode of administration comprises intradermal, intramuscular, subcutaneous, transdermal, mucosal, or oral administration;preferably, the subject is a mammal, e.g., a mouse, a human;preferably, the subject is selected from the group consisting of infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus.

25. A method for detecting the presence of RSV infection in a subject in vitro, the method comprising: contacting a biological sample obtained from the subject with the recombinant RSV F protein according to any one of claims 1 to 7 or the fusion protein according to any one of claims 8 to 12; and detecting the presence of a complex formed by the recombinant RSV F protein or the fusion protein and an antibody;preferably, the subject is a mammal, e.g., a mouse, a human;preferably, the subject is selected from the group consisting of infant (e.g., up to 1 year old), child (e.g., 1 to 6 years old), adolescent (e.g., 7 to 17 years old), adult (e.g., 18 to 60 years old), old people (e.g., over 60 years old), and pregnant woman carrying a fetus;preferably, the biological sample is selected from the group consisting of whole blood, serum, plasma, or any combination thereof.

26. A method for screening a candidate drug capable of inhibiting RSV infection of cell, the method comprising contacting the host cell with the candidate drug before, simultaneously with, or after contacting the host cell with the recombinant RSV F protein according to any one of claims 1 to 7 or the fusion protein according to any one of claims 8 to 12.

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