Influenza vaccines

Abstract

Pharmaceutical compositions and combined preparations comprising a first optimised haemagglutinin (HA) amino acid sequence, and a second, different, optimised HA amino acid sequence, are described, as well as pharmaceutical compositions and combined preparations comprising nucleic acid encoding the same, and their use as vaccines to induce an immune response against viruses of the influenza virus family. The first optimised HA amino acid sequence, and a second optimised HA amino acid sequence together synergistically elicit a broader, more potent immune response to influenza virus infection than the additive effect obtained by use of the first and second HA amino acid sequences (or their encoding nucleic acid) alone. Also described are vectors, cells, fusion proteins, polynucleotides, polypeptides, and messenger RNAs (mRNAs), their use as vaccines to induce an immune response against viruses of the influenza virus family, and methods of treatment.

Description

[0001] Influenza Vaccines This invention relates to pharmaceutical compositions, combined preparations, vectors, cells, fusion proteins, polynucleotides, polypeptides, and their use as vaccines against influenza infection. Influenza is a highly contagious respiratory illness caused by the influenza virus infecting the epithelial cells within the upper respiratory tract. The infection is characterised by a sudden onset of high fever, headache, muscle ache and fatigue, sore throat, cough and rhinitis. For the majority of cases, influenza rarely lasts for over a week and is usually restricted to the upper respiratory tract. However, in medically vulnerable people, such as people over 65 years old and people with certain chronic medical conditions, influenza can cause complications and even result in death. There are around 9 million-45 million human infections. WHO estimates that seasonal influenza may result in 290000-650000 deaths each year due to respiratory diseases alone. Thus, the development of an effective flu vaccine is critical to the health of millions of people around the world. The fundamental principal of a vaccine is to prepare the immune system for an encounter with a pathogen. A vaccine triggers the immune system to produce antibodies and T-cell responses, which helps to combat infection. Historically, once a pathogen was isolated and grown, it was either mass produced and killed or attenuated, and used as a vaccine. Later recombinant genes from isolated pathogens were used to generate recombinant proteins that were mixed with adjuvants to stimulate immune responses. More recently the pathogen genes were cloned into vector systems (attenuated bacteria or viral delivery systems) to express and deliver the antigen in vivo. All of these strategies are dependent on pathogens isolated from past outbreaks to prevent future ones. For pathogens which do not change significantly, or slowly, this conventional technology is effective. However, some pathogens, are prone to accelerated mutation rate and previously generated antibodies do not always recognise evolved strains of the same pathogen. New emerging and re-emerging pathogens often hide or disguise their vulnerable antigens from the immune system to escape the immune response. Influenza is one of the best characterised re-emerging pathogens, and re-emerges each season infecting up to 100 million people worldwide. Influenza is a member of the Orthomyxoviridae family and has a single-stranded negative sense RNA genome. RNA viruses generally have very high mutation rates compared to DNA viruses, because viral RNA polymerases lack the proofreading ability of DNA polymerases. This contributes towards antigenic drift, a continuous process of the accumulation of mutations in the genome of an infectious agent resulting in minor changes in antigens presented to the immune system of the host organism. Changes to antigenic regions of the proteins on the influenza virion result in its evasion of the host immune system and potentially increased pathogenicity and infectiousness. This is one reason why it is difficult to make effective vaccines to prevent influenza. Influenza can undergo antigenic shift, a process wherein there is a dramatic change in the antigens presented on the influenza virus. Gene segments from different subtypes of influenza can reassort and package into a new virion particle containing the genetic information from both of the subtypes. This can result in a virus that has antigenic characteristics not before seen in a human setting, to which we are naïve immunologically. The new quasi-species of the virus can cause a pandemic if no neutralising, or inhibitory antibodies to the new influenza virus are present in the human population. There are multiple types of influenza viruses, the most common in humans being influenza A, influenza B, and influenza C. Influenza A viruses infect a wide variety of birds and mammals, including humans, horses, marine mammals, pigs, ferrets, and chickens. In their natural reservoirs in aquatic birds and bats, influenza A viruses show minimal evolution and cause unapparent disease; but once they transfer to a different species, influenza A viruses can evolve rapidly as they adapt to the new host, possibly causing pandemics or epidemics of acute respiratory disease in domestic poultry, lower animals and humans. In animals, most influenza A viruses cause mild localized infections of the respiratory and intestinal tract. However, highly pathogenic influenza A strains, such as some within the H5N1 subtype, can cause systemic infections in poultry with spill-over human cases, which can have high mortality rates. Influenza B and C are restricted to infecting humans, with no known animal reservoirs. Influenza B causes epidemic seasonal infections, with similar pathogenicity as influenza A. Influenza C viruses are usually associated with very mild or asymptomatic infections in humans. At just over 100 years since the devastating 1918 influenza pandemic, there is still no optimal preventative or treatment against influenza A and B. Although they share some degree of similarity with antigen presentation on their surface, the highly heterologous nature of these antigens presents significant challenges in developing vaccines and treatments. During the 2019-2020 seasonal flu epidemic, quadrivalent vaccines were widely distributed. These gave protection against two influenza A viruses and two influenza B viruses. However, to prevent a potential outbreak of influenza in which the virus has rapidly evolved and hence unrecognisable by the host immune system, it is crucial that an influenza vaccine protects against many if not all potential influenza strains. Influenza A has an outer envelope that is studded with three integral membrane proteins: hemagglutinin (HA); neuraminidase (NA); and matrix ion channel (M2), which overlay a matrix protein (M1). The organisation of influenza B is similar, with HA and NA scattered across the lipid envelope, but with NB and BM2 transmembrane ion channels instead of M2. Influenza A viruses are subtyped based on their combination of surface glycoproteins (GPs) namely HA and NA. Influenza B viruses, having much less antigenic variation than influenza A, are not. HA and NA are membrane bound envelope GPs, responsible for virus attachment, penetration of the viral particles into the cell, and release of the viral particle from the cell. They are the sources of the major immunodominant epitopes for virus neutralisation and protective immunity. Hence, both HA and NA proteins are considered the most important components for prophylactic influenza vaccines. During HA-mediated entry, binding of the GP to sialic acid-containing receptors on the host cell membrane initiates endocytosis of the virion into the cell. The low pH within the endosome induces a conformational change in HA to expose a hydrophobic region, termed the fusion peptide. The newly exposed fusion peptide then inserts into the endosomal membrane, thereby bringing the viral and endosomal membranes in close contact to allow membrane fusion and entry of the virus into the cytoplasm. This release into the cytoplasm allows viral proteins and RNA molecules to enter the nucleus for viral transcription and subsequent replication. Transcribed, positive sense mRNAs are exported from the nucleus to be translated into viral proteins, and replicated negative sense RNA is exported from the nucleus to re-assemble with the newly synthesised viral proteins to form a progeny virus particle. The virus buds from the apical cell membrane, taking with it host membrane to form a virion capable of infecting another cell. HA exists as a homo-trimer on the virus surface, forming a cylinder-shaped molecule which projects externally from the virion and forms a type I transmembrane glycoprotein. Each monomer of the HA molecule consists of a single HA0 polypeptide chain with HA1 and HA2 regions linked by two disulphide bridges. Each HA0 polypeptide forms a globular head domain and a stem domain. The globular head domain comprises the most dominant epitopes, while the stem domain has less dominant, but important epitopes for broader antibody recognition. The amino acid sequence of these epitopes determines the binding affinity and specificity towards antibodies. The globular head domain consists of a part of HA1, including a receptor binding domain and an esterase domain, whereas the stem domain consists of parts of HA1 and HA2. Amino acid residues of HA1 that form the globular head domain fold into a motif of eight stranded antiparallel β-sheets which sits in a shallow pocket at the distal tip acting as the receptor binding site which is surrounded by antigenic sites. The remaining parts of the HA1 domain run down to the stem domain mainly comprising β-sheets. HA2 forms the majority of the stem domain and is folded into a helical coiled-coil structure forming the stem backbone. HA2 also contains the hydrophobic region required for membrane fusion, and a long helical chain anchored to the surface membrane and a short cytosolic tail. There are 18 different HA subtypes and 11 different NA subtypes within influenza A. Theoretically, there are potentially 198 different influenza A subtype combinations, some of which may be virulent in humans and other animals. As a result, there is significant concern that viruses from these subtypes could reassort with human transmissible viruses and initiate the next pandemic. In recent years, avian viruses of the H5, H7, H9, and H10 subtypes have caused zoonotic infections with H5 and H7 viruses often causing severe disease. The highly pathogenic Asian influenza (HPAI) outbreak of H5N1 of 1997 resulted in the killing of the entire domestic poultry population within Hong Kong. This panzootic also resulted in 860 confirmed infections and 454 fatalities in humans, demonstrating the ability of the avian-derived virus to transmit to humans and result in a high mortality rate. This HPAI of the H5N1 subtype frequently re-emerges and is of particular concern because of its 60% mortality rate, and because it continues to evolve and diversify. The last influenza pandemic in humans, in 2009, was caused by a novel H1N1 influenza A virus, generated by circulating human influenza reassorting with human, porcine, and avian influenza. The virus was very different from H1N1 viruses that were circulating at the time of the pandemic. As a result, very few young people had any existing immunity to the virus, and around a third of people over the age of 60 had antibodies against the virus from past exposure of similar H1N1 viruses. The CDC (Centre for Disease Control and Prevention) estimate that the total number of deaths worldwide caused by the 2009 outbreak is ranged between 150,000 to 575,400. In the case of the influenza virus, a clade is a further subdivision of influenza viruses based on the similarity of their HA gene sequences. In phylogenetic trees, clades and subclades are viewed as groups of viruses that usually have similar genetic changes. The sorting of viruses into clades and subclades enables the proportion of viruses from different clades in circulation to be tracked. The cladogram (a visual representation of the phylogenetic relationships) has the oldest (most basal) common ancestor found in a clade positioned close to the base / trunk of the evolutionary tree. Newly evolved species form the tree branches farthest from the tree trunk. The magnitude of the genetic difference between viruses is proportional to the length of the branches in the phylogenetic tree. Although clades and subclades are genetically distinct, they may not be antigenically distinct (that is, containing altered proteins or carbohydrates on their surface). Viruses whose genetic sequence share the same genetic changes and a common ancestor are grouped into “clades” and “subclades.” A node demonstrates a common ancestor. Only two influenza A virus subtypes A(H1N1)pdm09, and A(H3N2), are currently circulating among people, however H5N1 clade 2.3.4.4b is currently showing high risk of human spillover. Figure 1 shows a representation of Influenza A H5 phylogenetic tree featuring various clades. Since late 2020, clade 2.3.4.4b of a strain of highly pathogenic avian influenza virus A (H5N1), has been circulating globally, leading to more than 50 million dead wild birds and culled poultry. The virus has also started to be detected in mammals. Cases of H5N1 infection have been previously noted in species such as minks in Spain and dolphins in South America. More recently (June 2022), an outbreak of influenza A(H5N1) virus infections was reported among harbour and grey seals in New England, USA, that was concurrent with a large number of avian infections in the region. The outbreak in the seal population, thought to have resulted from environmental transmission of shed virus, caused an unusual mortality event in a seal population. There was also evidence of mammalian adaptation of the virus in a few seals, indicating the potential for zoonotic spillover into other species and possibly including humans. Influenza A is constantly evolving in multiple species and to prepare for this, virus characterization and translation into effective vaccines must be done in a timely manner. Although they have less antigenic variation than influenza A viruses, influenza B viruses have recently emerged into two antigenically distinct lineages (B / Victoria / 2 / 1987-like and B / Yamagata / 16 / 1988-like), illustrating the fluidity with which influenza B can evolve, and how it is also now imperative to include viruses of both type A and B in seasonal flu vaccinations. There is a need to provide improved influenza vaccines that elicit a broader, more potent immune response to influenza infection. In particular, there is a need to protect against more influenza strains than current vaccines, and to provide more potent protection against those strains. In particular, there is a need to provide improved vaccines that elicit more broadly neutralising immune responses to influenza A H5 viruses, and emerging influenza viruses derived from zoonotic spillover from animals to humans. Particularly, there is also a need to provide neutralising antibody protection across viruses of the H5Nx subtype of influenza A, especially clade 2.3.4.4 including 2.3.4.4b. There is also a need to provide vaccines with stronger neutralising capacity against viruses of a given type, subtype, clade or sub-clade. We have found that combined administration of vaccines comprising different influenza HA antigens (or nucleic acid encoding the antigens) surprisingly elicits a broader, more potent immune response to influenza virus infection than the additive effect obtained by use of the HA antigens (or their encoding nucleic acid) alone, i.e. there is a synergy. The HA antigens (or their encoding nucleic acid) may be co-administered, or administered sequentially such that the therapeutic effect of the combined use of the HA antigens (or nucleic acid encoding them) is greater than the additive effect obtained by use of the HA antigens (or nucleic acid encoding them) separately. This effect has been shown by combined administration of a first digitally immune optimised synthetic (DIOS) H5 antigen, and a second different DIOS H5 antigen, designed by the Applicant, against a panel of influenza H5 pseudoviruses (PVs). Thus, we have appreciated that such broadly effective, more potent vaccines are provided by use of a combination of different optimised influenza HA antigen vaccines, administered according to the invention. Such vaccines may be provided as nucleic acid vaccines, encoding a first HA polypeptide and a second, different HA polypeptide. The different polynucleotides may be administered as a mixture together (such as in a pharmaceutical composition comprising the different polynucleotides), or separate polynucleotides may be administered simultaneously, or administered sequentially in any order (in which case, the different polynucleotides may be provided as a combined preparation for simultaneous administration or sequential administration). Alternatively, the encoding polynucleotides may be provided as a single polynucleotide sequence (for example, as part of a vector comprising a first nucleotide sequence encoding a first HA polypeptide, and a second nucleotide sequence encoding a second, different HA polypeptide). Nucleic acid vaccines may be provided as DNA, RNA, or mRNA vaccines. In other embodiments, the vaccines may be provided as polypeptide vaccines, comprising a first HA polypeptide and a second, different HA polypeptide. Again, the different polypeptides may be administered as a mixture together (for example, as a pharmaceutical composition comprising the different polypeptides), or separate polypeptides may be administered simultaneously, or administered sequentially in any order (in which case, the different polypeptides may be provided as a combined preparation for simultaneous administration or sequential administration). The Applicant has also appreciated that broader and more potent immune responses can also be provided by combined administration of subunit-based vaccines (whether as a mixture as part of a pharmaceutical composition, or separately for simultaneous administration or sequential administration, for example as a combined preparation). Such vaccines may comprise a first and a second polynucleotide, wherein each polynucleotide encodes subunits comprising a different DIOS influenza HA antigen and one or more further influenza antigens. For example, each polynucleotide may comprise nucleic acid encoding a combination of different influenza antigens that are pieced together in a string. Described herein is a first polynucleotide encoding a first influenza HA antigen, an influenza neuraminidase (NA) antigen, and an influenza Matrix-2 (M2) antigen (a first string sequence), and a second polynucleotide encoding a second, different HA antigen, an influenza NA antigen, and an influenza M2 antigen (a second string sequence). Polynucleotides According to the invention there is provided a pharmaceutical composition which comprises: (a) a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence; and (c) a pharmaceutically acceptable carrier, excipient, or diluent. There is also provided according to the invention a combined preparation which comprises: (a) a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. The term “optimised” is used herein to refer to sequences that have been identified by carrying out a multiple sequence alignment of amino acid sequences (and / or encoding nucleotide sequences) of a haemagglutinin polypeptide of different influenza isolates, and identifying from the multiple sequence alignment amino acid sequence (or encoded amino acid sequence) that is highly conserved between the polypeptides of the different isolates. Optionally ancestral amino acid sequence is identified from the multiple sequence alignment, and included in an optimized HA sequence. Ancestral sequence reconstruction (ASR) is discussed in Randall et al. (Nat. Commun. 7:12847 doi: 10.1038 / ncomms 12847 (2016)). The authors reference a definition of ASR as “the process of analyzing modern sequences within an evolutionary / phylogenetic context to infer the ancestral sequences at particular nodes of a tree”. Ancestral sequence reconstruction (ASR) is used in the study of molecular evolution. Unlike conventional evolutionary approaches to studying proteins, by horizontal comparison of related protein homologues from different branch ends of a phylogenetic tree, ASR probes the statistically inferred ancestral proteins within the nodes of the tree in a vertical manner. A phylogenetic tree is a branching diagram showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. In a rooted phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of those descendants. In ASR, several related homologues of a protein of interest are selected and aligned in a multiple sequence alignment (MSA), a phylogenetic tree is constructed with statistically inferred sequences at the nodes of the branches. These sequences are the so-called 'ancestors'. The process of synthesising the corresponding DNA, transforming it into a cell and producing a protein is the so-called 'reconstruction'. Ancestral sequences are typically calculated by maximum likelihood, however Bayesian methods are also implemented. Because the ancestors are inferred from a phylogeny, the topology and composition of the phylogeny plays a major role in the output ASR sequences. ASR does not claim to recreate the actual sequence of the ancient protein / DNA, but rather a sequence that is likely to be similar to the one that was at the node. Maximum likelihood (ML) methods work by generating a sequence where the residue at each position is predicted to be the most likely to occupy that position by the method of inference used. Typically, this is a scoring matrix (similar to those used in BLASTs or MSAs) calculated from extant sequences. Alternate methods include maximum parsimony (MP) that construct a sequence based on a model of sequence evolution, usually the idea that the minimum number of nucleotide sequence changes represents the most efficient route for evolution to take and the most likely. MP is often considered the least reliable method for reconstruction as it arguably oversimplifies evolution to a degree that is not applicable on the billion year scale. Other methods include Bayesian methods, which involve the consideration of residue uncertainty. Such methods are sometimes used to compliment ML methods, but typically produce more ambiguous sequences (i.e. sequences which include residue positions where no clear substitution can be predicted). Often in such cases, several ASR sequences are produced, encompassing most of the ambiguities, and compared to one-another. Suitable methods and algorithms for ASR (including Maximum Parsimony, Maximum Likelihood, Bayesian Interference) are described in WO 2020 / 065349 (the contents of which are incorporated herein by reference; see in particular pages 28-40), and in Joy et al., 2016, PLOS Computational Biology 12(7): DOI:10.1371 / journal.pcbi.1004763. Any suitable method of ARS may be used to identify amino acid sequence or encoded amino acid sequence that is ancestral amino acid sequence from the multiple sequence alignment. Optionally identification of ancestral amino acid sequence from the multiple sequence alignment comprises performing a maximum parsimony ancestral sequence reconstruction (MP-ASR). Optionally identification of ancestral amino acid sequence from the multiple sequence alignment comprises performing a maximum likelihood ancestral sequence reconstruction (ML-ASR). Optionally identification of ancestral amino acid sequence from the multiple sequence alignment comprises performing a Bayesian inference ancestral sequence reconstruction (BI- ASR). There are many software packages available that perform ancestral sequence reconstruction. The following table (taken from Joy et al., 2016, PLOS Computational Biology 12(7): DOI:10.1371 / journal.pcbi.1004763) provides a representative sample of the extensive variety of packages that implement methods of ancestral reconstruction with different strengths and features: The majority of these software packages are designed for analyzing genetic sequence data. For example, PAML (Yang Z. PAML 4: phylogenetic analysis by maximum likelihood. Molecular biology and evolution. 2007;24(8):1586–91) is a collection of programs for the phylogenetic analysis of DNA and protein sequence alignments by ML. Ancestral reconstruction can be performed using the codeml program. HyPhy, Mesquite, and MEGA are also software packages for the phylogenetic analysis of sequence data, but are designed to be more modular and customizable. HyPhy (Pond SLK, Muse SV. HyPhy: hypothesis testing using phylogenies. Statistical methods in molecular evolution: Springer; 2005. p. 125–81) implements a joint ML method of ancestral sequence reconstruction (Pupko T, Pe I, Shamir R, Graur D. A fast algorithm for joint reconstruction of ancestral amino acid sequences. Molecular Biology and Evolution. 2000;17(6):890–6) that can be readily adapted to reconstructing a more generalized range of discrete ancestral character states such as geographic locations by specifying a customized model in its batch language. Mesquite (Maddison W, Maddison D. Mesquite: a modular system for evolutionary analysis. 2.75 ed20011) provides ancestral state reconstruction methods for both discrete and continuous characters using both maximum parsimony and ML methods. It also provides several visualization tools for interpreting the results of ancestral reconstruction. MEGA (Tamura K, Dudley J, Nei M, Kumar S. MEGA4: molecular evolutionary genetics analysis (MEGA) software version 4.0. Molecular biology and evolution. 2007;24(8):1596–9) is a modular system, too, but places greater emphasis on ease-of-use than customization of analyses. As of version 5, MEGA allows the user to reconstruct ancestral states using maximum parsimony, ML, and empirical Bayes methods. The Bayesian analysis of genetic sequences may confer greater robustness to model misspecification. MrBayes (Huelsenbeck JP, Ronquist F. MRBAYES: Bayesian inference of phylogenetic trees. Bioinformatics.2001;17(8):754–5) allows inference of ancestral states at ancestral nodes using the full hierarchical Bayesian approach. The PREQUEL program distributed in the PHAST package performs comparative evolutionary genomics using ancestral sequence reconstruction (Hubisz MJ, Pollard KS, Siepel A. PHAST and RPHAST: phylogenetic analysis with space / time models. Briefings in bioinformatics.2011;12(1):41–51). SIMMAP stochastically maps mutations on phylogenies (Bollback JP. SIMMAP: stochastic character mapping of discrete traits on phylogenies. BMC bioinformatics. 2006;7(1):88). BayesTraits (Pagel M. The maximum likelihood approach to reconstructing ancestral character states of discrete characters on phylogenies. Systematic biology.1999;48(3):612– 22) analyses discrete or continuous characters in a Bayesian framework to evaluate models of evolution, reconstruct ancestral states, and detect correlated evolution between pairs of traits. Other software packages are more oriented towards the analysis of qualitative and quantitative traits (phenotypes). For example, the ape package (Paradis E. Analysis of phylogenetics and evolution with R. New York: Springer; 2006) in the statistical computing environment R also provides methods for ancestral state reconstruction for both discrete and continuous characters through the ace function, including ML. Note that ace performs reconstruction by computing scaled conditional likelihoods instead of the marginal or joint likelihoods used by other ML-based methods for ancestral reconstruction, which may adversely affect the accuracy of reconstruction at nodes other than the root. Phyrex implements a maximum parsimony-based algorithm to reconstruct ancestral gene expression profiles in addition to a ML method for reconstructing ancestral genetic sequences (by wrapping around the baseml function in PAML) (Rossnes R, Eidhammer I, Liberles DA. Phylogenetic reconstruction of ancestral character states for gene expression and mRNA splicing data. BMC bioinformatics. 2005;6(1):127). Several software packages also reconstruct phylogeography. BEAST (Bayesian Evolutionary Analysis by Sampling Trees (Bouckaert R, Heled J, Kühnert D, Vaughan T, Wu C- H, Xie D, et al. BEAST 2: a software platform for Bayesian evolutionary analysis. PLoS Comput Biol. 2014;10(4):e1003537)) provides tools for reconstructing ancestral geographic locations from observed sequences annotated with location data using Bayesian MCMC sampling methods. Diversitree (FitzJohn RG. Diversitree: comparative phylogenetic analyses of diversification in R. Methods in Ecology and Evolution.2012;3(6):1084–92) is an R package providing methods for ancestral state reconstruction under Mk2 (a continuous time Markov model of binary character evolution (Pagel M. Detecting Correlated Evolution on Phylogenies—a General- Method for the Comparative-Analysis of Discrete Characters. Proceedings of the Royal Society of London Series B-Biological Sciences.1994;255(1342):37–45)) and BiSSE models. Lagrange performs analyses on reconstruction of geographic range evolution on phylogenetic trees (Ree RH, Smith SA. Maximum likelihood inference of geographic range evolution by dispersal, local extinction, and cladogenesis. Systematic Biology. 2008;57(1):4–14). Phylomapper (Lemmon AR, Lemmon EM. A likelihood framework for estimating phylogeographic history on a continuous landscape. Systematic Biology.2008;57(4):544–61) is a statistical framework for estimating historical patterns of gene flow and ancestral geographic locations. RASP (Yu Y, Harris AJ, Blair C, He X. RASP (Reconstruct Ancestral State in Phylogenies): a tool for historical biogeography. Molecular Phylogenetics and Evolution. 2015;87:46–9) infers ancestral state using statistical DIVA, Lagrange, Bayes- Lagrange, BayArea, and BBM methods. VIP (Arias JS, Szumik CA, Goloboff PA. Spatial analysis of vicariance: a method for using direct geographical information in historical biogeography. Cladistics. 2011;27(6):617–28) infers historical biogeography by examining disjunct geographic distributions. Genome rearrangements provide valuable information in comparative genomics between species. ANGES (Jones BR, Rajaraman A, Tannier E, Chauve C. ANGES: reconstructing ANcestral GEnomeS maps. Bioinformatics. 2012;28(18):2388–90) compares extant-related genomes through ancestral reconstruction of genetic markers. BADGER (Larget B, Kadane JB, Simon DL. A Bayesian approach to the estimation of ancestral genome arrangements. Molecular phylogenetics and evolution. 2005;36(2):214–23) uses a Bayesian approach to examining the history of gene rearrangement. Count (Csűös M. Count: evolutionary analysis of phylogenetic profiles with parsimony and likelihood. Bioinformatics. 2010;26(15):1910–2) reconstructs the evolution of the size of gene families. EREM (Affre L, Thompson JD, Debussche M. Genetic structure of continental and island populations of the Mediterranean endemic Cyclamen balearicum (Primulaceae). American Journal of Botany.1997;84(4):437– 51) analyses the gain and loss of genetic features encoded by binary characters. PARANA (Patro R, Sefer E, Malin J, Marçais G, Navlakha S, Kingsford C. Parsimonious reconstruction of network evolution. Algorithms for Molecular Biology. 2012;7(1):1) performs parsimony- based inference of ancestral biological networks that represent gene loss and duplication. There are also several web server-based applications that allow investigators to use ML methods for ancestral reconstruction of different character types without having to install any software. For example, Ancestors (Diallo AB, Makarenkov V, Blanchette M. Ancestors 1.0: a web server for ancestral sequence reconstruction. Bioinformatics.2010;26(1):130–1) is a web server for ancestral genome reconstruction by the identification and arrangement of syntenic regions. FastML (Ashkenazy H, Penn O, Doron-Faigenboim A, Cohen O, Cannarozzi G, Zomer O, et al. FastML: a web server for probabilistic reconstruction of ancestral sequences. Nucleic acids research. 2012;40(W1):W580–W4) is a web server for probabilistic reconstruction of ancestral sequences by ML that uses a gap character model for reconstructing indel variation. MLGO (Hu F, Lin Y, Tang J. MLGO: phylogeny reconstruction and ancestral inference from gene-order data. BMC bioinformatics. 2014;15(1):1) is a web server for ML gene order analysis. Optionally nucleic acid encoding an optimized HA amino acid sequence includes one or optimizing codons for optimal expression of the encoded optimized HA amino acid in an expression system. Codon optimization takes advantage of the degeneracy of the genetic code, and does not alter the amino acid sequence of the encoded polypeptide. Because of degeneracy, one protein can be encoded by many alternative nucleic acid sequences. Codon preference (codon usage bias) differs in each organism, and this can create challenges for expressing recombinant proteins in heterologous expression systems, resulting in low and unreliable expression. Any suitable expression system may be used. Several suitable examples are well known to the skill person, including expression in a mammalian, yeast, insect, or bacterial cell. Optionally the expression system comprises a mammalian cell. Optionally the expression system comprises a yeast, an insect, or a bacterial cell. Methods of codon-optimization are well known to those of ordinary skill in the art. A codon optimization algorithm may be used to design a codon-optimized nucleotide sequence encoding an amino acid sequence. Such algorithms are aimed at providing codon-optimized sequences which maximise expression of a polypeptide or protein in a desired expression system. Examples of suitable codon optimization algorithms include GeneOptimizer™ algorithm (ThermoFisher), OptimumGene™ algorithm (GenScript), and GeneGPS®(ATUM). Optionally other sequence optimization is included to maximise protein expression in a desired expression system. Such gene optimization takes account of codon usage bias, as well as other sequence-related parameters involved in gene expression, such as transcription, splicing, translation, and mRNA degradation. Examples of such sequence-related parameters are given below (the parameters are classed below as affecting transcriptional efficiency, translational efficiency, or protein refolding, but several of the parameters may influence more than one of these steps): Transcriptional Efficacy: • GC content • SD sequence • CpG dinucleotides content • TATA boxes • Cryptic splicing sites • Terminal signal • Negative CpG islands • Artificial recombination sites Translational Efficiency: • RNA instability motif (ARE) • Codon usage bias • Stable free energy of mRNA • GC content • Internal chi sites and ribosomal binding • mRNA secondary structure sites • Premature PolyA sites • Repetitive sequences Protein Refolding: • Codon usage bias • Codon-context • Interaction of codon and anti-codon • RNA secondary structures Gene optimization algorithms, such as GeneOptimizer™ and OptimumGene™, take account of several of these parameters. Gene optimization for expression of human proteins in E.coli is discussed by Maertens et al. (Protein Science 2010 Vol.19:1312—1326). Optionally ancestral amino acid sequence is identified from the multiple sequence alignment, and included in an optimized HA amino acid sequence for use according to the invention. Optionally an optimized HA amino acid sequence for use according to the invention (or nucleic acid encoding an optimized HA amino acid sequence) is optimized for antigenicity of the amino acid sequence. Antigenic optimization may include any of the following: (a) deletion or modification of nucleic acid sequence encoding amino acid sequence believed to inhibit production and / or function of anti-pathogen polypeptide antibody (for example, deletion or modification of a mucin-like domain – see Reynard et al., Journal of Virology, 2009, 9596-9601); (b) region swapping to recover one or more potential lost encoded epitopes; (c) site-specific mutation, for example of N-linked glycosylation sites. Typically site- specific mutation is designed to delete N-linked glycosylation sites, although there may be situations where additional sites might be desired to be introduced, for instance to mask epitopes that elicit non-neutralizing antibodies. The ability of glycosylation to sterically block antibody binding to HA and thus provide protection against the host immune response has been demonstrated for influenza viruses. Sun et al. (Journal of Virology, 2013, 87(15):8756-8766) demonstrate that antibodies induced by viruses with a high number of glycosylation sites have a broader neutralizing activity than the antibodies induced by the viruses with fewer glycosylation sites; (d) changes to enhance stability (e.g. disulphide bond formation, reduce degradation of the encoded polypeptide by a serine protease); (e) removal of glycans (improve access for B-cells); (f) insertion of nucleic acid sequence, for example to insert nucleic acid sequence encoding a desired epitope. Antigenic optimization of the outer domain of HIV-1 gp120 is described by Joyce et al. (J Virol. 2013 Feb;87(4):2294-306). An example of a suitable method of optimization to provide an optimized HA amino acid sequence for use according to the invention is as follows: Primary sequences are downloaded, for example, from GenBank (and from any other available sources, such as outbreak data), and are filtered to remove identical sequences, sequences that do not span the protein of interest, and sequences that have a high number of ambiguous nucleotides. A multiple sequence alignment of the filtered sequences is generated (typically using MAFFT), and checked manually to ensure that sequences are in the correct open reading frame. A maximum likelihood phylogeny is generated using IQTREE, with automated model selection, and rooted using one of several methods; an outgroup sequence, midpoint rooting, centre-of-the-tree, or a tree that maximises the association between root-to-tip distance and sampling time. Ancestral sequences are generated using HyPhy assuming a MG94 by F3x4 model of codon substitution, and are checked to ensure that known epitopes have been preserved. A phylogenetic tree with both primary and ancestral sequences is generated using IQTREE to check the placement of the ancestral strains. Ancestral sequences are then modified in a number of ways: deletion of regions (e.g. removal of the mucin-like domain); region swapping (to recover potential lost epitopes); mutation of specific sites (e.g. in the fusion domain of the filoviruses), including editing of N-linked glycosylation sites and introduction of mutations to enhance stability”. Optionally an optimised HA amino acid sequence is a non-naturally occurring HA amino acid sequence. A combined preparation of the invention may be provided as a pharmaceutical combined preparation for administration to a mammal, preferably a human. Component (a) may optionally be provided together with a pharmaceutically acceptable carrier, excipient, or diluent, and / or component (b) may optionally be provided together with a pharmaceutically acceptable carrier, excipient, or diluent. There is also provided according to the invention a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use as a medicament, wherein the first isolated polynucleotide is to be administered before, with, or after administration of the second isolated polynucleotide. There is further provided according to the invention a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polynucleotide is to be administered before, with, or after administration of the second isolated polynucleotide. There is also provided according to the invention use of a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polynucleotide is to be administered before, with, or after administration of the second isolated polynucleotide. There is also provided according to the invention a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use as a medicament, wherein the first isolated polynucleotide is to be administered before, with, or after administration of a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. There is further provided according to the invention a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polynucleotide is to be administered before, with, or after administration of a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. There is further provided according to the invention use of a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polynucleotide is to be administered before, with, or after administration of a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence encoding an optimised haemagglutinin H5 amino acid sequence, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence encoding an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and which has the following amino acid residues at positions corresponding to positions 156, 157, 171, 172, and 205 of SEQ ID NO:1: • 156: R; • 157: S; • 171: N; • 172: A; and • 205: R, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:2, or a nucleotide sequence that is at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical over its entire length with SEQ ID NO:2, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:2, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:4, or a nucleotide sequence that is at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical over its entire length with SEQ ID NO:4, or the complement thereof. Optionally the first and / or the second isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:4, or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof, and the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or the complement thereof, and the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof, and the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof, and the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof, and the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof, and the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or the complement thereof. Optionally the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1) and the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof. Optionally the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1.), or the complement thereof. Optionally the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3) and the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or the complement thereof. Optionally the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (nucleic acid sequence encoding T2_HA_9 amino acid sequence), or the complement thereof. Optionally the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (nucleic acid sequence encoding T4_HA_2 amino acid sequence), or the complement thereof. Optionally the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (nucleic acid sequence encoding T2_HA_9 amino acid sequence), or the complement thereof. Optionally the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (nucleic acid sequence encoding T4_HA_2 amino acid sequence), or the complement thereof. Optionally the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (nucleic acid sequence encoding T2_HA_9 amino acid sequence) and the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (nucleic acid sequence encoding T4_HA_2 amino acid sequence), or the complement thereof. Optionally the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (nucleic acid sequence encoding T4_HA_2 amino acid sequence) and the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (nucleic acid sequence encoding T2_HA_9 amino acid sequence), or the complement thereof. Vectors There is also provided according to the invention a vector which comprises a polynucleotide comprising: (a) a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. Optionally the vector further comprises a promoter operably linked to the first and second nucleotide sequences. Optionally the vector further comprises a first promoter operably linked to the first nucleotide sequence of the vector, and a separate, second promoter operably linked to the second nucleotide sequence. There is also provided according to the invention a pharmaceutical composition which comprises a vector of the invention, and a pharmaceutically acceptable carrier, excipient, or diluent. There is also provided according to the invention a pharmaceutical composition which comprises: (a) a first vector comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; (b) a second vector comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (c) a pharmaceutically acceptable carrier, excipient, or diluent, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. There is further provided according to the invention a combined preparation which comprises: (a) a first vector comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second vector comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. There is also provided according to the invention a first vector which comprises a polynucleotide comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second vector which comprises a polynucleotide comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use as a medicament, wherein the first vector is to be administered before, with, or after administration of the second vector. There is also provided according to the invention a first vector which comprises a polynucleotide comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second vector which comprises a polynucleotide comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first vector is to be administered before, with, or after administration of the second vector. There is also provided according to the invention use of a first vector which comprises a polynucleotide comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second vector which comprises a polynucleotide comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection, wherein the first vector is to be administered before, with, or after administration of the second vector. There is also provided according to the invention a first vector which comprises a polynucleotide which comprises a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use as a medicament, wherein the vector is to be administered before, with, or after administration of a second vector which comprises a polynucleotide which comprises a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. There is further provided according to the invention a first vector which comprises a polynucleotide which comprises a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first vector is to be administered before, with, or after administration of a second vector which comprises a polynucleotide which comprises a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. There is further provided according to the invention use of a first vector which comprises a polynucleotide which comprises a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection, wherein the first vector is to be administered before, with, or after administration of a second vector which comprises a polynucleotide which comprises a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence. Optionally the first vector further comprises a first promoter operably linked to the first nucleotide sequence, and the second vector further comprises a second promoter operably linked to the second nucleotide sequence. Optionally the first nucleotide sequence of the first vector and / or second nucleotide sequence of the second vector comprises a nucleotide sequence encoding an optimised haemagglutinin (HA) H5 amino acid sequence, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence encoding an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and which has the following amino acid residues at positions corresponding to positions 156, 157, 171, 172, and 205 of SEQ ID NO:1: • 156: R; • 157: S; • 171: N; • 172: A; and • 205: R, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence of SEQ ID NO:2, or a nucleotide sequence that is at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical over its entire length with SEQ ID NO:2, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence of SEQ ID NO:2, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence of SEQ ID NO:4, or a nucleotide sequence that is at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical over its entire length with SEQ ID NO:4, or the complement thereof. Optionally the first and / or the second nucleotide sequence comprises a nucleotide sequence of SEQ ID NO:4, or the complement thereof. Optionally the first nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof, and the second nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the first isolated nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or the complement thereof, and the second nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the first nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof, and the second nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof. Optionally the first nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof, and the second nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the first nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or the complement thereof, and the second nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the first nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, or the complement thereof, and the second nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or the complement thereof. Optionally the first nucleotide sequence of the first vector comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof. Optionally the second nucleotide sequence of the second vector comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof. Optionally the first nucleotide sequence of the first vector comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1) and the second nucleotide sequence of the second vector comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof. Optionally the first nucleotide sequence of the first vector comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof. Optionally the second nucleotide sequence of the second vector comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof. Optionally the first nucleotide sequence of the first vector comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), the second nucleotide sequence of the second vector comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof. Optionally the nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1) comprises the nucleotide sequence of SEQ ID NO:2, or the complement thereof. Optionally the nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3) comprises the nucleotide sequence of SEQ ID NO:4, or the complement thereof. Optionally the, or each promoter is for expression of a polypeptide encoded by the polynucleotide in mammalian cells. Optionally the, or each promoter is for expression of a polypeptide encoded by the polynucleotide in yeast or insect cells. Optionally the, or each vector is a vaccine vector. Optionally the, or each vaccine vector is a viral vaccine vector, a bacterial vaccine vector, an RNA vaccine vector, an mRNA vaccine vector, or a DNA vaccine vector. There is also provided according to the invention an isolated cell comprising or transfected with a vector of the invention. Nucleic acid subunit vaccines Subunit-based vaccines may be provided, for example, as nucleic acid vaccines, either as separate polynucleotides, each encoding a different subunit (for administration together or separately) or pieced together in a string as a single polynucleotide encoding all of the subunits. Separate polynucleotides may be administered as a mixture together (for example, as a pharmaceutical composition comprising the separate polynucleotides), or administered simultaneously or sequentially in any order (in which case, the separate polynucleotides may be provided as a combined preparation for co-administration or sequential administration). Nucleic acid vaccines may be provided as DNA, RNA, or mRNA vaccines. According to the invention the subunits of a nucleic acid subunit vaccine may comprise nucleic acid encoding an optimised HA polypeptide and an influenza neuraminidase (NA) polypeptide and / or a Matrix-2 (M2) polypeptide. Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, and / or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence of a pharmaceutical composition, a combined preparation, a first and a second isolated polynucleotide for use, a first isolated polynucleotide for use, or a vector, according to the invention, further comprises a nucleotide sequence encoding an influenza neuraminidase (NA) and / or a Matrix-2 (M2) polypeptide. Optionally the or each nucleotide sequence encoding the influenza NA polypeptide is a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:5, and the or each nucleotide sequence encoding the influenza M2 polypeptide is a nucleotide sequence encoding a T2_M2_1 amino acid sequence (SEQ ID NO:7), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:7. Optionally the or each nucleotide sequence encoding the influenza NA polypeptide is a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the or each nucleotide sequence encoding the influenza M2 polypeptide is a nucleotide sequence encoding a T2_M2_1 amino acid sequence (SEQ ID NO:7). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1).Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1). Optionally the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1). Strategies for multigene co-expression include introduction of multiple vectors, use of multiple promoters in a single vector, fusion proteins, proteolytic cleavage sites between genes, internal ribosome entry sites (IRES), and “self-cleaving” 2A peptides. Multicistronic vectors (for example, where the subunits are provided in a string as a single polynucleotide) based on IRES nucleotide sequence and self-cleaving 2A peptides are reviewed in Shaimardanova et al. (Pharmaceutics 2019, 11, 580; doi:10.3390 / pharmaceutics11110580). 2A self-cleaving peptides are 18–22 amino-acid-long viral oligopeptides that mediate “cleavage” of polypeptides during translation in eukaryotic cells (Liu et al., Scientific Reports 7, Article number: 2193 (2017)). The designation “2A” refers to a specific region of the viral genome and different viral 2As have generally been named after the virus they were derived from. The first discovered 2A was F2A (foot-and-mouth disease virus), after which E2A (equine rhinitis A virus), P2A (porcine teschovirus-12A), and T2A (thosea asigna virus 2A) were also identified. The mechanism of 2A-mediated “self-cleavage” is ribosome skipping the formation of a glycyl-prolyl peptide bond at the C-terminus of the 2A. A highly conserved sequence GDVEXNPGP is shared by different 2As at the C-terminus, and is essential for the creation of steric hindrance and ribosome skipping. There are three possibilities for a 2A- mediated skipping event: (1) Successful skipping and recommencement of translation results in two “cleaved” proteins: the protein upstream of the 2A is attached to the complete 2A peptide except for the C-terminal proline, and the protein downstream of the 2A is attached to one proline at the N-terminus; (2) Successful skipping but ribosome fall-off and discontinued translation results in only the protein upstream of 2A; (3) Unsuccessful skipping and continued translation resulting in a fusion protein. Overall, 2A peptides lead to relatively high levels of downstream protein expression compared to other strategies for multi-gene co-expression, and they are small in size thus bearing a lower risk of interfering with the function of co- expressed genes. Examples of suitable 2A self-cleaving peptide sequences which may be encoded by nucleic acid between nucleic acid sequences encoding different subunits include: GSGEGRGSLLTCGDVEENPGP (SEQ ID NO:13) GSGATNFSLLKQAGDVEENPGP (SEQ ID NO:14) Messenger RNA (mRNA) vaccines A polynucleotide of the invention, or a polynucleotide of a pharmaceutical composition, a combined preparation, or a vector, of the invention, may be provided as part of an mRNA vaccine. There is also provided according to the invention an mRNA vaccine which comprises a polynucleotide of the invention, a vector of the invention, or a pharmaceutical composition or a combined preparation of the invention which comprises one or more polynucleotides, wherein the or each polynucleotide comprises an mRNA molecule. Messenger RNA (mRNA) vaccines are a new form of vaccine (recently reviewed in Pardi et al., Nature Reviews Drug Discovery Volume 17, pages 261–279(2018); Wang et al., Molecular Cancer (2021) 20:33: mRNA vaccine: a potential therapeutic strategy). The first mRNA vaccines to be approved for use were BNT162b2 (BioNTech’s vaccine manufactured by Pfizer) and mRNA-1273 (manufactured by Moderna) against SARS-CoV-2 during the COVID- 19 pandemic. Since then, mRNA-based vaccines have been developed for seasonal influenza and are currently in clinical trials, such as mRNA-1010, a quadrivalent seasonal influenza vaccine encoding membrane-bound HA surface glycoproteins of four influenza strains (A / H1N1, A / H3N2, B / Victoria, and B / Yamagata). mRNA vaccines have a unique feature of temporarily promoting the expression of antigen (typically days). The expression of the exogenous antigen is controlled by the lifetime of encoding mRNA, which is regulated by cellular degradation pathways. While this transient nature of protein expression requires repeated administration for the treatment of genetic diseases and cancers, it is extremely beneficial for vaccines, where prime or prime-boost vaccination is sufficient to develop highly specific adaptive immunity without any exposure to the contagion. mRNA based vaccines trigger an immune response after the synthetic mRNA which encodes viral antigens transfects human cells. The cytosolic mRNA molecules are then translated by the host’s own cellular machinery into specific viral antigens. These antigens may then be presented on the cell surface where they can be recognised by immune cells, triggering an immune response. The structural elements of a vaccine vector mRNA molecule are similar to those of natural mRNA, comprising a 5’ cap, 5’ untranslated region (UTR), coding region (for example, comprising an open reading frame encoding a polypeptide of the invention), 3’ UTR, and a poly(A) tail. The 5′ UTR (also known as a leader sequence, transcript leader, or leader RNA) is the region of an mRNA that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript. In many organisms, the 5′ UTR forms complex secondary structure to regulate translation. The 5′ UTR begins at the transcription start site and ends one nucleotide (nt) before the initiation sequence (usually AUG) of the coding region. In eukaryotes, the length of the 5′ UTR tends to be anywhere from 100 to several thousand nucleotides long. The differing sizes are likely due to the complexity of the eukaryotic regulation which the 5′ UTR holds as well as the larger pre-initiation complex that must form to begin translation. The eukaryotic 5′ UTR contains the Kozak consensus sequence (ACCAUG (initiation codon underlined) (SEQ ID NO:11), which contains the initiation codon AUG. An elongated Kozak sequence: GCCACCAUG (initiation codon underlined) (SEQ ID NO:12) may also be used for mRNA vaccine constructs. The 5′ and 3′ UTR elements flanking the coding sequence profoundly influence the stability and translation of mRNA, both of which are critical concerns for vaccines. These regulatory sequences can be derived from viral or eukaryotic genes and greatly increase the half-life and expression of therapeutic mRNAs. For example, a 5’UTR of an mRNA of the invention may comprise, with an initiation codon of the mRNA, a Kozak consensus sequence, or an elongated Kozak sequence. Optionally a 5’UTR of an mRNA of the invention comprises the following sequence: GGAGACGCCACC immediately upstream of an initiation codon sequence. A 5′ cap structure is required for efficient protein production from mRNA. Various versions of 5′ caps can be added during or after the transcription reaction using a vaccinia virus capping enzyme, or by incorporating synthetic cap or anti-reverse cap analogues (see Pardi et al., supra). Anti-Reverse Cap Analog (ARCA) is a cap analog used during in vitro transcription for the generation of capped transcripts. ARCA is modified in a way that ensures incorporation in the forward orientation only. Anti-Reverse Cap Analog (ARCA) is a modified cap analog in which the 3' OH group (closer to m7G) is replaced with –OCH3: Conventional Cap Analog: R=H, m7G(5’)pppG; ARCA: R=CH3, 3’-0-Me-m7G(5’)pppG Because of this substitution, the RNA polymerase can only initiate transcription with the remaining hydroxyl group thus forcing ARCA incorporation in the forward orientation. As a result, unlike transcripts synthesized with conventional cap analog, 100% of the transcripts synthesized with ARCA at the 5' end are translatable leading to a strong stimulatory effect on translation. The poly(A) tail also plays an important regulatory role in mRNA translation and stability; thus, an optimal length of poly(A) must be added to mRNA either directly from the encoding DNA template or by using poly(A) polymerase (see Pardi et al., supra). An example of a suitable length of poly(A) tail is poly(~A120). The codon usage additionally has an impact on protein translation. Replacing rare codons with frequently used synonymous codons that have abundant cognate tRNA in the cytosol is a common practice to increase protein production from mRNA. Enrichment of G:C content constitutes another form of sequence optimization that has been shown to increase steady- state mRNA levels in vitro and protein expression in vivo (see Pardi et al., supra). Two major types of RNA are currently studied as vaccines: non-replicating mRNA and virally derived, self-amplifying RNA. While both types of vaccines share a common structure in mRNA constructs, self-amplifying RNA vaccines contain additional sequences in the coding region for RNA replication, including RNA-dependent RNA polymerases. A nucleic acid vaccine (for example, a mRNA) of the invention may be formulated in a lipid nanoparticle (LNP). Betacoronavirus vaccine constructs BNT162b2, mRNA-1273, and mRNA-1010 all comprise a LNP encapsulated mRNA molecule encoding the respective viral antigens. BNT162b2 vaccine construct comprises a lipid nanoparticle (LNP) encapsulated mRNA molecule. The mRNA is encapsulated in 80 nm ionizable cationic lipid nanoparticles. mRNA-1273 vaccine construct is also based on an LNP vector. US Patent No. 10,702,600 B1 (ModernaTX) describes betacoronavirus mRNA vaccines, including suitable LNPs for use in such vaccines. There is also provided according to the invention an mRNA vaccine, which comprises an mRNA of the invention (or mRNAs of the invention, or a pharmaceutical composition or a combined preparation of the invention comprising mRNAs), or an mRNA vaccine vector (or mRNA vaccine vectors, or a pharmaceutical composition or a combined preparation of the invention comprising mRNA vectors) of the invention, encapsulated in a lipid nanoparticle (LNP). mRNA vaccines have several advantages in comparison with conventional vaccines containing inactivated (or live attenuated) disease-causing organisms. Firstly, mRNA-based vaccines can be rapidly developed due to design flexibility and the ability of the constructs to mimic antigen structure and expression as seen in the course of a natural infection. mRNA vaccines can be developed within days or months based on sequencing information from a target virus, while conventional vaccines often take years and require a deep understanding of the target virus to make the vaccine effective and safe. Secondly, these novel vaccines can be rapidly produced. Due to high yields from in vitro transcription reactions, mRNA production can be rapid, inexpensive and scalable (due to chemical synthesis rather than biological growth of cells or bacteria). Thirdly, vaccine risks are low. mRNA does not contain infectious viral elements or cell debris that pose risks for infection and insertional mutagenesis (as the mRNA is generated synthetically). Anti-vector immunity is also avoided as mRNA is the minimally immunogenic genetic vector, allowing repeated administration of the vaccine. The challenge for effective application of mRNA vaccines lies in cytosolic delivery. mRNA isolates are rapidly degraded by extracellular RNases and cannot penetrate cell membranes to be transcribed in the cytosol. However, efficient in vivo delivery can be achieved by formulating mRNA into carrier molecules, allowing rapid uptake and expression in the cytoplasm. To date, numerous delivery methods have been developed including lipid-, polymer-, or peptide-based delivery, virus-like replicon particle, cationic nanoemulsion, naked mRNAs, and dendritic cell- based delivery (each reviewed in Wang et al., supra). Decationic lipid nanoparticle (LNP) delivery is the most appealing and commonly used mRNA vaccine delivery tool. Exogenous mRNA may be highly immunostimulatory. Single-stranded RNA (ssRNA) molecules are considered a pathogen associated molecular pattern (PAMP), and are recognised by various Toll-like receptors (TLR) which elicit a pro-inflammatory reaction. Although a strong cellular and humoral immune response is desirable in response to vaccination, the innate immune reaction elicited by exogenous mRNA may cause undesirable side-effects in the subject. The U-rich sequence of mRNA is a key element to activate TLR (Wang et al., supra). Additionally, enzymatically synthesised mRNA preparations contain double stranded RNA (dsRNA) contaminants as aberrant products of the in vitro transcription (IVT) process. dsRNA is a potent PAMP, and elicits downstream reactions resulting in the inhibition of translation and the degradation of cellular mRNA and ribosomal RNA (Pardi et al., supra). Thus, the mRNA may suppress antigen expression and thus reduce vaccine efficacy. Studies over the past decade have shown that the immunostimulatory effect of mRNA can be shaped by the purification of IVT mRNA, the introduction of modified nucleosides, complexing the mRNA with various carrier molecules (Pardi et al., supra), adding poly(A) tails or optimising mRNA with GC-rich sequence (Wang et al., supra). Chemical modification of uridine is a common approach to minimise the immunogenicity of foreign mRNA. Incorporation of pseudouridine (ψ) and N1- methylpseudouridine (m1ψ) to IVT mRNA prevents TLR activation and other innate immune sensors, thus reducing pro-inflammatory signalling in response to the exogenous mRNA. Such nucleoside modification also suppresses recognition of dsRNA species (Pardi et al., supra) and can reduce innate immune sensing of exogenous mRNA translation (Hou et al. Nature Reviews Materials, 2021, https: / / doi.org / 10.1038 / s41578-021- 00358-0). Other nucleoside chemical modifications include, but are not limited to, 5-methylcytidine (m5C), 5-methyluridine (m5U), N1-methyladenosine (m1A), N6- methyladenosine (m6A), 2- thiouridine (s2U), and 5-methoxyuridine (5moU) (Wang et al., supra). The IVT mRNA molecules used in the mRNA-1273 and BNT162b2 COVID-19 vaccines were prepared by replacing uridine with m1ψ, and their sequences were optimized to encode a stabilized pre- fusion spike protein with two pivotal proline substitutions (Hou et al., supra). However, CureVac’s mRNA vaccine candidate, CVnCoV, uses unmodified nucleosides and relies on a combination of mRNA sequence alterations to allow immune evasion without affecting the expressed protein. Firstly, CVnCoV has a higher GC content (63%) than rival vaccines (BNT162b2 has 56%) and the original SARS-CoV-2 virus itself (37%). Secondly, the vaccine comprises C-rich motifs which bind to poly(C)-binding protein, enhancing both the stability and expression of the mRNA. A further modification of CVnCoV is that it contains a histone stem-loop sequence as well as a poly(A) tail, to enhance the longevity and translation of the mRNA (Hubert, B., 2021. The CureVac Vaccine, and a brief tour through some of the wonders of nature. URL https: / / berthub.eu / articles / posts / curevac-vaccine-and-wonders-of- biology / .(accessed 15.09.21). CureVac and Acuitas Therapeutics delivered erythropoietin (EPO)-encoding mRNA, which has rich GC codons, to pigs with lipid nanoparticles (LNPs). Their results indicated EPO-related responses were elicited without immunogenicity (Wang et al., supra). A polynucleotide of the invention may comprise an mRNA molecule. The or each polynucleotide of a pharmaceutical composition, a combined preparation, or a vector, of the invention may comprise an mRNA molecule. A vector of the invention may be an mRNA vector. The or each vector of a pharmaceutical composition or a combined preparation of the invention may be an mRNA vector. A polynucleotide of the invention, or a polynucleotide of a pharmaceutical composition, a combined preparation, or a vector, of the invention, may be provided as part of an mRNA vaccine. There is also provided according to the invention an mRNA vaccine which comprises a polynucleotide of the invention, a vector of the invention, or a pharmaceutical composition or a combined preparation of the invention which comprises one or more polynucleotides, wherein the or each polynucleotide comprises an mRNA molecule. RNA or mRNA of a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention may be produced by in vitro transcription (IVT). A polynucleotide of the invention, or a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention may comprise one or more modified nucleosides. The one or more modified nucleosides may be present in DNA or RNA of a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention. Optionally, at least one chemical modification is selected from pseudouridine, N1- methylpseudouridine, N1-ethylpseudouridine, 2-thiouridine, 4′-thiouridine, 5-methylcytosine, 5-methyluridine, 2-thio-1-methyl-1-deaza-pseudouridine, 2-thio-1-methyl-pseudouridine, 2- thio-5-aza-uridine, 2-thio-dihydropseudouridine, 2-thio-dihydrouridine, 2-thio-pseudouridine, 4-methoxy-2-thio-pseudouridine, 4-methoxy-pseudouridine, 4-thio-1-methyl-pseudouridine, 4-thio-pseudouridine, 5-aza-uridine, dihydropseudouridine, 5-methoxyuridine and 2′-O-methyl uridine. In some embodiments, the chemical modification is in the 5-position of the uracil. In some embodiments, the chemical modification is a N1-methylpseudouridine. In some embodiments, the chemical modification is a N1-ethylpseudouridine. For example, an RNA or an mRNA of a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention may comprise one or more of the following modified nucleosides: pseudouridine (ψ); N1- methylpseudouridine (m1ψ) 5-methylcytidine (m5C) 5-methyluridine (m5U) N1-methyladenosine (m1A) N6- methyladenosine (m6A) 2-thiouridine (s2U) 5- methoxyuridine (5moU) In some embodiments, 100% of the uracil in the open reading frame have a chemical modification. In some embodiments, a chemical modification is in the 5-position of the uracil. In some embodiments, a chemical modification is a N1-methyl pseudouridine. In some embodiments, 100% of the uracil in the open reading frame have a N1-methyl pseudouridine in the 5-position of the uracil. The polynucleotide may contain from about 1% to about 100% modified nucleotides (or nucleosides) (either in relation to overall nucleotide content, or in relation to one or more types of nucleotide, i.e., any one or more of A, G, U or C) or any intervening percentage (e.g., from 1% to 20%, from 1% to 25%, from 1% to 50%, from 1% to 60%, from 1% to 70%, from 1% to 80%, from 1% to 90%, from 1% to 95%, from 10% to 20%, from 10% to 25%, from 10% to 50%, from 10% to 60%, from 10% to 70%, from 10% to 80%, from 10% to 90%, from 10% to 95%, from 10% to 100%, from 20% to 25%, from 20% to 50%, from 20% to 60%, from 20% to 70%, from 20% to 80%, from 20% to 90%, from 20% to 95%, from 20% to 100%, from 50% to 60%, from 50% to 70%, from 50% to 80%, from 50% to 90%, from 50% to 95%, from 50% to 100%, from 70% to 80%, from 70% to 90%, from 70% to 95%, from 70% to 100%, from 80% to 90%, from 80% to 95%, from 80% to 100%, from 90% to 95%, from 90% to 100%, and from 95% to 100%). Any remaining percentage is accounted for by the presence of unmodified A, G, U, or C. Optionally at least 50% of the uridines in the ORF have been modified. Optionally at least 50% of the uridines in the ORF have been modified to m1ψ. Optionally a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention, comprises an RNA molecule in which the nucleic acid sequence of the polynucleotide is the same as that recited in the respective SEQ ID, or the complement thereof, but with each ‘U’ replaced by m1ψ. Optionally a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention, comprises an mRNA molecule in which the nucleic acid sequence of the polynucleotide is the same as that recited in the respective SEQ ID, or the complement thereof, but with each ‘U’ replaced by m1ψ. Optionally a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention, comprises an RNA molecule in which the nucleic acid sequence of the polynucleotide is the same as that recited in the respective SEQ ID, or the complement thereof, but with at least 50% of the ‘U’s replaced by m1ψ. The remaining ‘U’s may all be unmodified, or may comprise unmodified and one or more other modified nucleosides. Optionally a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention, comprises an mRNA molecule in which the nucleic acid sequence of the polynucleotide is the same as that recited in the respective SEQ ID, or the complement thereof, but with at least 50% of the ‘U’s replaced by m1ψ. The remaining ‘U’s may all be unmodified, or may comprise unmodified and one or more other modified nucleosides. Optionally a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention, comprises an RNA molecule in which the nucleic acid sequence of the polynucleotide is the same as that recited in the respective SEQ ID, or the complement thereof, but with at least 90% of the ‘U’s replaced by m1ψ. The remaining ‘U’s may all be unmodified, or may comprise unmodified and one or more other modified nucleosides. Optionally a polynucleotide of the invention, or of a polynucleotide of a pharmaceutical composition, a combined preparation, a vector, or a vaccine, of the invention, comprises an mRNA molecule in which the nucleic acid sequence of the polynucleotide is the same as that recited in the respective SEQ ID, or the complement thereof, but with at least 90% of the ‘U’s replaced by m1ψ. The remaining ‘U’s may all be unmodified, or may comprise unmodified and one or more other modified nucleosides. mRNA vaccines of the invention may be co-administered with an immunological adjuvant, for example MF59 (Novartis), TriMix, RNActive (CureVac AG), RNAdjuvant (again reviewed in Wang et al., supra). Thus, in preferred embodiments, each vector of a pharmaceutical composition, or combined preparation, of the invention is an mRNA vaccine vector. Polypeptides Vaccines of the invention may be provided as polypeptide vaccines, comprising a first HA polypeptide and a second, different HA polypeptide. Again, the different polypeptides may be administered as a mixture together (for example, as a pharmaceutical composition comprising the different polypeptides), or separate polypeptides may be administered simultaneously, or administered sequentially in any order (in which case, the different polypeptides may be provided as a combined preparation for simultaneous administration or sequential administration). Accordingly, there is also provided according to the invention a pharmaceutical composition which comprises: (a) a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence; and (b) a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence; and (c) a pharmaceutically acceptable carrier, excipient, or diluent. There is further provided according to the invention a combined preparation which comprises: (a) a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence; and (b) a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence. There is also provided according to the invention a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, and a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence, for use as a medicament, wherein the first isolated polypeptide is to be administered before, with, or after administration of the second isolated polypeptide. There is also provided according to the invention a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, and a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polypeptide is to be administered before, with, or after administration of the second isolated polypeptide. There is also provided according to the invention use of a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, and a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polypeptide is to be administered before, with, or after administration of the second isolated polypeptide. There is also provided according to the invention a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, for use as a medicament, wherein the first isolated polypeptide is to be administered before, with, or after administration of a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence. There is also provided according to the invention a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polypeptide is to be administered before, with, or after administration of a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence. There is also provided according to the invention use of a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polypeptide is to be administered before, with, or after administration of a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence. There is also provided according to the invention an isolated polypeptide which comprises: (a) a first optimised haemagglutinin (HA) amino acid sequence; and (b) a second optimised haemagglutinin (HA) amino acid sequence, wherein the first HA amino acid sequence is different to the second amino acid sequence. Optionally the first and / or second optimised HA amino acid sequence comprises a haemagglutinin H5 amino acid sequence. Optionally the first and / or the second optimised HA amino acid sequence, comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1. Optionally the first and / or the second optimised HA amino acid sequence comprises an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and which has the following amino acid residues at positions corresponding to positions 156, 157, 171, 172, and 205 of SEQ ID NO:1: • 156: R; • 157: S; • 171: N; • 172: A; and • 205: R. Optionally the first and / or the second optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3. Optionally the first optimised HA amino acid sequence comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and the second optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3. Optionally the first optimised HA amino acid sequence comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), and the second optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3. Optionally the first optimised HA amino acid sequence comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and the second optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3). Optionally the first optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, and the second optimised HA amino acid sequence comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1. Optionally the first optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), and the second optimised HA amino acid sequence comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1. Optionally the first optimised HA amino acid sequence comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, and the second optimised HA amino acid sequence comprises a T2_HA_9 amino acid sequence (amino acid SEQ ID NO:1). Optionally the first optimised HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1). Optionally the second optimised HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3). Optionally the first optimised HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1), and the second optimised HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3). Optionally the first optimised HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3). Optionally the second optimised HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1). Optionally the first optimised HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3), and the second optimised HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1). There is also provided according to the invention a fusion protein comprising a polypeptide of the invention. Polypeptide subunit vaccines Nucleic acid subunit vaccines are discussed above. Alternatively, the subunits may be provided as polypeptides for a polypeptide subunit vaccine. Optionally the first isolated polypeptide, comprising the first optimised HA amino acid sequence, and / or the second isolated polypeptide comprising the second optimised HA amino acid sequence, further comprises an amino acid sequence of an influenza neuraminidase (NA) polypeptide and / or a Matrix-2 (M2) polypeptide. Optionally the amino acid sequence of the or each influenza NA polypeptide is a T2_NA_3 amino acid sequence (SEQ ID NO:5), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:5, and the amino acid sequence of the or each M2 polypeptide is a T2_M2_1 amino acid sequence (SEQ ID NO:7), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:7. Optionally the amino acid sequence of the or each influenza NA polypeptide is a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the amino acid sequence of the or each M2 polypeptide is a T2_M2_1 amino acid sequence (SEQ ID NO:7). A suitable linker may be present between each different polypeptide in the first isolated polypeptide and / or the second isolated polypeptide. Alternatively, a self-cleaving peptide may be present between each different polypeptide, thereby allowing processing of the polypeptide under suitable conditions to provide separate subunits (i.e. the first optimised HA polypeptide and the influenza neuraminidase (NA) polypeptide and / or Matrix-2 (M2) polypeptide, or the second optimised HA polypeptide and the influenza neuraminidase (NA) polypeptide and / or Matrix-2 (M2) polypeptide). In other embodiments, the polypeptide subunits may be provided as individual polypeptides for administration as a mixture in a pharmaceutical composition, or separately for simultaneous or sequential administration as a combined preparation. Pharmaceutical compositions The ratio of the amount of a pharmaceutical composition component (a) to a pharmaceutical composition component (b) can be varied, for example in order to cope with the needs of a patient sub-population to be treated, or the needs of the single patient, which can be due, for example, to the particular disease, age, sex, or body weight of the patient. Preferably, there is at least one beneficial effect, for example an enhancing of the effect of component (a), or an enhancing of the effect of component (b), or a mutual enhancing of the effect of the composition components (a) and (b), for example a more than additive effect, additional advantageous effects, fewer side effects, less toxicity, or a combined therapeutic effect compared with an effective dosage of one or both of the composition components (a) and (b), and very preferably a synergism of the composition components (a) and (b). For example, there may be a broader immune response and / or a greater immune response (including, for example, a greater neutralising antibody response) to different influenza types, subtypes, clades, or sub-clades. For example, there may be greater neutralising antibody protection across viruses of the H5Nx subtype of influenza A, especially clade 2.3.4.4 including 2.3.4.4b. For example, there may be a broader immune response and / or a greater immune response (including, for example, a greater neutralising antibody response) to different H5 clades (including, for example, any, or any combination, of the following H5 clades: 1, 2.1.3.2, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1a, 2.3.4.4a, 2.3.4.4b, 2.3.4.4c, 2.3.4.4h, EU non-GS-GD, such as the following H5 clades: 1, 2.1.3.2, 2.3.4.4a, 2.3.4.4b (avian or human), 2.3.4.4c, and 2.3.4.4h; or 1, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1a, 2.3.4.4a, 2.3.4.4b (avian or human), 2.3.4.4c, 2.3.4.4h, and EU non-GS-GD. Combined preparations The term "combined preparation" as used herein refers to a "kit of parts" in the sense that the combination components (a) and (b) as defined above can be dosed independently or by use of different fixed combinations with distinguished amounts of the combination components (a) and (b). The components can be administered simultaneously or one after the other. If the components are administered one after the other, preferably the time interval between administration is chosen such that the therapeutic effect of the combined use of the components is greater than the effect which would be obtained by use of only any one of the combination components (a) and (b). The components of the combined preparation may be present in one combined unit dosage form, or as a first unit dosage form of component (a) and a separate, second unit dosage form of component (b). The ratio of the total amounts of the combination component (a) to the combination component (b) to be administered in the combined preparation can be varied, for example in order to cope with the needs of a patient sub-population to be treated, or the needs of the single patient, which can be due, for example, to the particular disease, age, sex, or body weight of the patient. Preferably, there is at least one beneficial effect, for example an enhancing of the effect of component (a), or an enhancing of the effect of component (b), or a mutual enhancing of the effect of the combination components (a) and (b), for example a more than additive effect, additional advantageous effects, fewer side effects, less toxicity, or a combined therapeutic effect compared with an effective dosage of one or both of the combination components (a) and (b), and very preferably a synergism of the combination components (a) and (b). For example, there may be a broader immune response and / or a greater immune response (including, for example, a greater neutralising antibody response) to different influenza types, subtypes, clades, or sub-clades. For example, there may be greater neutralising antibody protection across viruses of the H5Nx subtype of influenza A, especially clade 2.3.4.4 including 2.3.4.4b. For example, there may be a broader immune response and / or a greater immune response (including, for example, a greater neutralising antibody response) to different H5 clades (including, for example, any, or any combination, of the following H5 clades: 1, 2.1.3.2, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1a, 2.3.4.4a, 2.3.4.4b, 2.3.4.4c, 2.3.4.4h, EU non-GS-GD, such as the following H5 clades: 1, 2.1.3.2, 2.3.4.4a, 2.3.4.4b (avian or human), 2.3.4.4c, and 2.3.4.4h; or 1, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1a, 2.3.4.4a, 2.3.4.4b (avian or human), 2.3.4.4c, 2.3.4.4h, and EU non-GS-GD. String sequences The subunit nucleic acid vaccines discussed above provide first and second polynucleotides, each polynucleotide comprising nucleotide sequence encoding an optimised HA polypeptide amino acid sequence and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence (referred to herein as a nucleic acid “string” sequence). Similarly, the subunit polypeptide vaccines described above provide first and second polypeptides, each polypeptide comprising amino acid sequence of an optimised HA polypeptide and an influenza neuraminidase (NA) polypeptide, and / or a Matrix-2 (M2) polypeptide (referred to herein as a polypeptide “string” sequence). According to the invention there is provided an isolated polynucleotide which comprises a nucleotide sequence encoding a T2_HA_9 amino acid sequence (SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and a nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence encoding an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and which has the following amino acid residues at positions corresponding to positions 156, 157, 171, 172, and 205 of SEQ ID NO:1: • 156: R; • 157: S; • 171: N; • 172: A; and • 205: R, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence encoding an amino acid sequence of SEQ ID NO:1, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:2, or a nucleotide sequence that is at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical over its entire length with SEQ ID NO:2, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:2, or the complement thereof. According to the invention there is provided an isolated polynucleotide which comprises a nucleotide sequence encoding a T2_HA_9 amino acid sequence (SEQ ID NO:1), and a nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence, or the complement thereof. According to the invention there is also provided an isolated polynucleotide which comprises a nucleotide sequence encoding a T4_HA_2 amino acid sequence (SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, and a nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a nucleotide sequence encoding a Matrix-2 (M2) polypeptide amino acid sequence, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence encoding an amino acid sequence of SEQ ID NO:3, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:4, or a nucleotide sequence that is at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical over its entire length with SEQ ID NO:4, or the complement thereof. Optionally the isolated polynucleotide comprises a nucleotide sequence of SEQ ID NO:4, or the complement thereof. According to the invention there is also provided an isolated polynucleotide which comprises a nucleotide sequence encoding a T4_HA_2 amino acid sequence (SEQ ID NO:3), and a nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a nucleotide sequence encoding a Matrix-2 (M2) polypeptide amino acid sequence, or the complement thereof. Optionally the nucleotide sequence encoding an influenza NA polypeptide is a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:5. Optionally the nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence comprises a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5). Optionally the nucleotide sequence encoding an influenza M2 polypeptide is a nucleotide sequence encoding a T2_M2_1 amino acid sequence (SEQ ID NO:7), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:7. Optionally the nucleotide sequence encoding a Matrix-2 (M2) polypeptide amino acid sequence comprises a nucleotide sequence encoding a T2_M2_1 polypeptide amino acid sequence (SEQ ID NO:7). Optionally the nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence comprises a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the nucleotide sequence encoding a Matrix-2 (M2) polypeptide amino acid sequence comprises a nucleotide sequence encoding a T2_M2_1 polypeptide amino acid sequence (SEQ ID NO:7). Optionally, an isolated polynucleotide of the invention comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), or the complement thereof. Optionally, an isolated polynucleotide of the invention comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), or the complement thereof. Optionally, an isolated polynucleotide of the invention comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), or the complement thereof. Optionally, an isolated polynucleotide of the invention comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), or the complement thereof. According to the invention there is also provided an isolated polypeptide which comprises a T2_HA_9 amino acid sequence (SEQ ID NO:1), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence. Optionally the isolated polypeptide comprises an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:1, and which has the following amino acid residues at positions corresponding to positions 156, 157, 171, 172, and 205 of SEQ ID NO:1: • 156: R; • 157: S; • 171: N; • 172: A; and • 205: R. Optionally the isolated polypeptide comprises an amino acid sequence of SEQ ID NO:1. There is also provided according to the invention an isolated polypeptide which comprises a T2_HA_9 amino acid sequence (SEQ ID NO:1), and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence. According to the invention there is also provided an isolated polypeptide which comprises a T4_HA_2 amino acid sequence (amino acid SEQ ID NO:3), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:3, and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence. Optionally the isolated polypeptide comprises an amino acid sequence of SEQ ID NO:3. There is also provided according to the invention an isolated polypeptide which comprises a T4_HA_2 amino acid sequence (SEQ ID NO:3), and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence. Optionally the NA polypeptide amino acid sequence comprises a T2_NA_3 amino acid sequence (SEQ ID NO:5), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:5. Optionally the influenza neuraminidase (NA) polypeptide amino acid sequence comprises a T2_NA_3 amino acid sequence (SEQ ID NO:5). Optionally the M2 polypeptide amino acid sequence comprises a T2_M2_1 amino acid sequence (SEQ ID NO:7), or an amino acid sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity along its entire length with the amino acid sequence of SEQ ID NO:7. Optionally the Matrix-2 (M2) polypeptide amino acid sequence comprises a T2_M2_1 amino acid sequence (SEQ ID NO:7). Optionally the influenza neuraminidase (NA) polypeptide amino acid sequence comprises a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the Matrix-2 (M2) polypeptide amino acid sequence comprises a T2_M2_1 amino acid sequence (SEQ ID NO:7). There is also provided according to the invention a pharmaceutical composition which comprises an isolated polynucleotide of the invention, or an isolated polypeptide of the invention, and a pharmaceutically acceptable carrier, excipient, or diluent. There is also provided according to the invention a vector which comprises an isolated polynucleotide of the invention, and a separate promoter operably linked to each different nucleotide sequence of the polynucleotide. There is further provided according to the invention a fusion protein comprising an isolated polypeptide of the invention. There is also provided according to the invention a pseudotyped virus particle comprising an isolated polypeptide of the invention. There is also provided according to the invention an isolated polynucleotide of the invention, an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, for use as a medicament. There is also provided according to the invention an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, for use in the prevention, treatment, or amelioration of an influenza infection. There is also provided according to the invention use of an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection. There is also provided according to the invention an isolated polynucleotide of the invention, an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, for use in inducing an immune response to an influenza virus in a subject. There is also provided according to the invention use of an isolated polynucleotide of the invention, an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, in the manufacture of a medicament for inducing an immune response to an influenza virus in a subject. There is also provided according to the invention an isolated polynucleotide of the invention, an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, for use in immunising a subject against an influenza virus. There is also provided according to the invention use of an isolated polynucleotide of the invention, an isolated polypeptide of the invention, a pharmaceutical composition of the invention, or a vector of the invention, in the manufacture of a medicament for immunising a subject against an influenza virus. There is also provided according to the invention a method of inducing an immune response to an influenza virus in a subject, which comprises administering to the subject an effective amount of: isolated polynucleotide of the invention; an isolated polypeptide of the invention; a pharmaceutical composition of the invention; or a vector of the invention. There is also provided according to the invention a method of immunising a subject against an influenza virus, which comprises administering to the subject an effective amount of: isolated polynucleotide of the invention; an isolated polypeptide of the invention; a pharmaceutical composition of the invention; or a vector of the invention. Methods of treatment and medical uses There is also provided according to the invention a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, for use as a medicament. There is also provided according to the invention a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, for use in the prevention, treatment, or amelioration of an influenza infection. There is also provided according to the invention use of a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, in the manufacture of a medicament for the prevention, treatment, or amelioration of an influenza infection. There is also provided according to the invention a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, for use in inducing an immune response to an influenza virus in a subject. There is also provided according to the invention use of a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, in the manufacture of a medicament for inducing an immune response to an influenza virus in a subject. There is also provided according to the invention a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, for use in immunising a subject against an influenza virus. There is also provided according to the invention use of a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention, in the manufacture of a medicament for immunising a subject against an influenza virus. There is also provided according to the invention a method of inducing an immune response to an influenza virus in a subject, which comprises administering to the subject an effective amount of a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention. There is also provided according to the invention a method of immunising a subject against an influenza virus, which comprises administering to the subject an effective amount of a pharmaceutical composition of the invention, a combined preparation of the invention, a vector of the invention, or a polypeptide of the invention. Component (a) and component (b) of a combined preparation of the invention, or for use according to the invention, may be administered to the subject sequentially, in any order, for example within 96 hours, 72 hours, 48 hours, 24 hours, or 12 hours, of each other. Alternatively, component (a) and component (b) may be co-administered to the subject, for example as a composition comprising component (a) and component (b), or by simultaneous administration of separate doses of component (a) and component (b). According to some embodiments, a plurality of doses of component (a), and / or a plurality of doses of component (b), is administered to the subject. According to some embodiments, a dose of component (a), is administered before, with, or after each administration of two or more doses of component (b). For example, a dose of component (a), may be administered within 96 hours, 72 hours, 48 hours, 24 hours, or 12 hours, of each administration of two or more doses of component (b). According to some embodiments, a dose of component (b), is administered before, with, or after each administration of two or more doses of component (a). For example, a dose of component (b), may be administered within 96 hours, 72 hours, 48 hours, 24 hours, or 12 hours, of each administration of two or more doses of component (a). The choice of appropriate dosages of the components used in combination therapy according to the present invention can be determined and optimized by the skilled person, for example, by observation of the patient, including the patient's overall health, and the response to the combination therapy. Optimization, for example, may be necessary if it is determined that a patient is not exhibiting the desired therapeutic effect or conversely, if the patient is experiencing undesirable or adverse side effects that are too many in number or are of a troublesome severity. The doses of the components used in combination therapy according to the invention should be chosen to provide a therapeutically effective amount of the components in combination. An “effective amount” of the combination therapy may be an amount that results in a reduction of at least one pathological parameter associated with influenza infection. For example, in some embodiments, an effective amount of the combination therapy is an amount that is effective to achieve a reduction of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, in the pathological parameter, compared to the expected reduction in the parameter associated with the influenza infection without the combination therapy. For example, the pathological parameter may be viral load (for example, the number of influenza viral particles or amount of viral DNA per ml of blood). Suitable methods of measuring viral load are well-known to those of ordinary skill in the art. For example, methods of measuring viral load by ELISA are compared in Goldschmidt et al. (Clinical and Diagnostic Laboratory Immunology, July 1998, p. 513–518). Methods of measuring viral load using different commercial assays for detection of viral nucleic acid are compared in Holguin et al. (Eur J Clin Microbiol Infect Dis. 1999 Apr;18(4):256-9) and Swenson et al. (J. Clin. Microbiol. 2014 Feb; 52(2): 517–523). A list of FDA-approved screening assays to measure viral loads can be found on the FDA website at: www.fda.gov / BiologicsBloodVaccines / BloodBloodProducts / ApprovedProducts / LicensedProd uctsBLAs / BloodDonorScreening / InfectiousDisease / ucm080466.htm. Alternatively, an “effective amount” of the combination therapy may be an amount that results in an increase in a clinical benefit associated with prevention or treatment of infection. For example, in some embodiments, an “effective amount” of the combination therapy is an amount that is effective to achieve an increase of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, in the clinical benefit, compared to the expected clinical benefit without the combination therapy. Alternatively, an “effective amount” of the combination therapy may be an amount that results in a change of at least one beneficial parameter relating to prevention or treatment of infection. For example, in some embodiments, an “effective amount” of the combination therapy is an amount that is effective to achieve a change of at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, in the parameter, compared to the expected change in the parameter relating to treatment without the combination therapy. For example, the parameter may be an increase in the number of circulating antigen-specific CD8+T cells, or a reduction in the number of antigen-specific regulatory T cells, or an increase in the number of activated T cells, in particular activated CD8+T cells, a reduction in the number of exhausted antigen-specific CD8+T cells, or an increase in the number of circulating functional (i.e. non-exhausted) antigen-specific CD8+T cells. According to the invention, combination treatment may be employed to increase the therapeutic effect of component (a), or component (b), compared with the effect of the component (a) or component (b), as a monotherapy, or to decrease the doses of the individual components in the resulting combinations while preventing or further reducing the risk of unwanted or harmful side effects of the individual components. In one embodiment, component (a) and component (b) are each prescribed at a dose that is within a typically prescribed dose range for each component as a monotherapy. The components may be prescribed as separate dosages or as a combination dosage. Such combinations provide increased efficacy compared with the effect of either component as a monotherapy. In another embodiment, component (a) and component (b) are each prescribed at a dose that is below a typically prescribed dose for each component as a monotherapy, but at doses that have therapeutic efficacy in combination. The components may be prescribed as separate dosages or as a combination dosage. The dosages of the components in combination may be selected to provide a similar level of therapeutic efficacy as component (a) or component (b) as a monotherapy, but with the advantage that the lower doses of component (a) and component (b) reduce the risk of adverse side effects compared to the prescribed dosages of each component as a monotherapy. In another embodiment, the prescribed dosage of component (a) is within a typically prescribed dose range for monotherapy, and component (b) is prescribed at a dosage that is below a typically prescribed dose for monotherapy. In a further embodiment, the prescribed dosage of component (a) is below a typically prescribed dose for monotherapy, and component(b) is prescribed at a dosage that is within a typically prescribed dose range for monotherapy. Preferred dosages below the typically prescribed dose for monotherapy are doses that are up to 50%, or up to 25%, of the typically prescribed dose. For example, dosages below the typically prescribed dose for monotherapy may be doses that are 1-50%, 1-25%, 1-10%, 2- 50%, 2-25%, 2-10%, of the typically prescribed dose of component (a) and / or component (b). In particular embodiments of combined preparations or compositions of the invention, the prescribed dosage of component (a) or component (b) is below a typically prescribed dose for monotherapy, for example 1-50%, 1-25%, 1-20%, 1-10%, 2-50%, 2-25%, 2-20%, 2-10%, 0.1- 50%, 0.1-25%, 0.1-20%, 0.1-10%, <20%, <10%, 0.1-<20%, 0.1-<10%, 0.01-<20%, or 0.01- <10% of the typically prescribed dose of component (a) or component (b). The term “prevention” is used herein to refer to an immune response that is elicited in a subject that is sufficient to inhibit (i.e. reduce), neutralise or prevent influenza virus infection, and / or progress of influenza virus infection in the subject, or to inhibit (i.e. reduce), neutralise or prevent any symptom of influenza virus infection in the subject. The term “treatment” is used herein to refer to at least a reduction of one or more, or all, of the symptoms associated with an influenza infection in the subject. Treatment also includes situations where the influenza infection, or at least one or more, or all, of the symptoms associated therewith, are completely stopped from happening, such that the subject no longer suffers from the influenza infection, or at least from one or more, or all, of the symptoms associated with the influenza infection. The term “amelioration” is used herein to refer to a reduction of one or more of the symptoms associated with an influenza infection in the subject. Broadly neutralising immune responses Polynucleotides, polypeptides, pharmaceutical compositions, combined preparations, and vaccines of the invention may induce a broadly neutralising immune response to protect against disease caused by influenza viruses. The term “broadly neutralising immune response” is used herein to mean an immune response elicited in a subject that is sufficient to inhibit (i.e. reduce), neutralise or prevent infection, and / or progress of infection, of multiple viruses of the influenza family of viruses, particularly across the H5 subtype. Optionally a broadly neutralising immune response is sufficient to inhibit, neutralise or prevent infection, and / or progress of infection, of more than one type of influenza, for example influenza type A and influenza type B. Optionally a broadly neutralising immune response is sufficient to inhibit, neutralise or prevent infection, and / or progress of infection, of more than one type of subtype of influenza A, for example influenza H1 and influenza H5. Optionally a broadly neutralising immune response is sufficient to inhibit, neutralise or prevent infection, and / or progress of infection, of more than one type of clade of influenza A H5 (for example, clades 1, 2.1.3.2, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1, 2.3.4, 2.3.4.4, and 7.1). Optionally a broadly neutralising immune response is sufficient to inhibit, neutralise or prevent infection, and / or progress of infection, of most or all different H5 clades. For example, there may be an immune response (including, for example, a neutralising antibody response) to different influenza types, subtypes, clades, or sub-clades. For example, there may be neutralising antibody protection across viruses of the H5Nx subtype of influenza A, especially clade 2.3.4.4 including 2.3.4.4b. For example, there may be an immune response (including, for example, a neutralising antibody response) to different H5 clades (including, for example, any, or any combination, of the following H5 clades: 1, 2.1.3.2, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1a, 2.3.4.4a, 2.3.4.4b, 2.3.4.4c, 2.3.4.4h, EU non-GS-GD, such as the following H5 clades: 1, 2.1.3.2, 2.3.4.4a, 2.3.4.4b (avian or human), 2.3.4.4c, and 2.3.4.4h; or 1, 2.2, 2.2.1, 2.2.1.1, 2.3.2.1a, 2.3.4.4a, 2.3.4.4b (avian or human), 2.3.4.4c, 2.3.4.4h, and EU non-GS-GD. The immune response may be humoral and / or a cellular immune response. A cellular immune response is a response of a cell of the immune system, such as a B-cell, T-cell, macrophage or polymorphonucleocyte, to a stimulus such as an antigen or vaccine. An immune response can include any cell of the body involved in a host defence response, including for example, an epithelial cell that secretes an interferon or a cytokine. An immune response includes, but is not limited to, an innate immune response or inflammation. Optionally a polynucleotide, polypeptide, pharmaceutical composition, combined preparation, or vaccine of the invention of the invention induces a protective immune response. A protective immune response refers to an immune response that protects a subject from infection or disease (i.e. prevents infection or prevents the development of disease associated with infection). Methods of measuring immune responses are well known in the art and include, for example, measuring proliferation and / or activity of lymphocytes (such as B or T cells), secretion of cytokines or chemokines, inflammation, or antibody production. Optionally a polynucleotide, polypeptide, pharmaceutical composition, combined preparation, or vaccine of the invention is able to induce the production of antibodies and / or a T-cell response in a human or non-human animal to which the polypeptide has been administered (either as a polypeptide or, for example, expressed from an administered nucleic acid expression vector). Administration Any suitable route of administration may be used. Methods of administration include, but are not limited to, intradermal, intramuscular, intraperitoneal, parenteral, intravenous, subcutaneous, vaginal, rectal, intranasal, inhalation or oral. Parenteral administration, such as subcutaneous, intravenous or intramuscular administration, is generally achieved by injection. Injectables can be prepared in conventional forms, either as liquid solutions or suspensions, solid forms suitable for solution or suspension in liquid prior to injection, or as emulsions. Injection solutions and suspensions can be prepared from sterile powders, granules, and tablets of the kind previously described. Administration can be systemic or local. Routes for systemic administration in general include, for example, transdermal, oral, parenteral routes, including subcutaneous, intravenous, intramuscular, intraarterial, intradermal and intraperitoneal injections and / or intranasal administration routes. Routes for local administration in general include, for example, topical administration routes but also intradermal, transdermal, subcutaneous, or intramuscular injections or intralesional, intracranial, intrapulmonal, intracardial, and sublingual injections. For lipid nanoparticles, the administration route is often determined by the properties of the nanoparticles and therapeutic indications. After intravenous (i.v.) administration, many lipid nanoparticles can accumulate in the liver. The liver is inherently capable of producing secretory proteins and, therefore, i.v. administration of lipid nanoparticle–mRNA formulations can be used to produce proteins that are missing in inherited metabolic and haematological disorders, or to produce antibodies to neutralize pathogens or target cancer cells. These applications require protein translation without stimulation of an immune response, which may limit the efficiency of repeated dosing. However, i.v. administration may also lead to accumulation of lipid nanoparticles in multiple lymph nodes throughout the body, which could increase immune responses to mRNA vaccines. For example, i.v. administration of mRNA vaccines has been shown to induce stronger antigen-specific cytotoxic T cell responses compared with local injection. Broad distribution of mRNA vaccines in the body may lead to systemic adverse effects, and, thus, it may be necessary to develop lipid nanoparticles that allow targeted delivery of mRNA vaccines into tissues with abundant immune cells. Topical administration routes have also been explored for mRNA therapeutics. Topical administration aims at achieving local therapeutic effects; for example, local injection of lipid nanoparticle–mRNA formulations enables supplementation of therapeutic proteins in specific tissues, such as heart, eyes and brain. Moreover, lipid nanoparticle–mRNA formulations can be administered into the lungs by inhalation. Local administration of mRNA vaccines can also prime systemic responses; for example, intradermal (i.d.), intramuscular (i.m.) and subcutaneous (s.c.) injection are commonly used for vaccination, because resident and recruited antigen-presenting cells (APCs) are present in the skin and muscle, which can internalize and process mRNA-encoded antigens. Furthermore, the vascular and lymphatic vessels of these tissues help APCs and mRNA vaccines to centre the draining lymph nodes to stimulate T cell immunity. Indeed, both i.m. and i.d. administration of lipid nanoparticle–mRNA vaccines produce robust immune responses at a well-tolerated dose in human trials. Vaccination can also be done by intranasal administration, because APCs in the peripheral lymph nodes can readily endocytose administered lipid nanoparticle–mRNA formulations. mRNA vaccines delivered by lipid nanoparticle may comprise cationic lipids and / or ionisable lipids, see review: Lipid Nanoparticles for mRNA Delivery, Nature Reviews Materials, 61078- 1094, 2021. In addition to cationic or ionizable lipids, lipid nanoparticle–mRNA formulations typically contain other lipid components, such as phospholipids (for example, phosphatidylcholine and phosphatidylethanolamine), cholesterol or polyethylene glycol (PEG)-functionalized lipids (PEG-lipids). These lipids can improve nanoparticle properties, such as particle stability, delivery efficacy, tolerability and biodistribution. Compositions of the invention may be administered in any suitable manner, such as with pharmaceutically acceptable carriers. Pharmaceutically acceptable carriers are determined in part by the particular composition being administered, as well as by the particular method used to administer the composition. Preparations for parenteral administration include sterile aqueous or nonaqueous solutions, suspensions, and emulsions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, alcoholic / aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer’s dextrose, dextrose and sodium chloride, lactated Ringer’s, or fixed oils. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers (such as those based on Ringer’s dextrose), and the like. Preservatives and other additives may also be present such as, for example, antimicrobials, anti-oxidants, chelating agents, and inert gases and the like. Some of the compositions may potentially be administered as a pharmaceutically acceptable acid- or base-addition salt, formed by reaction with inorganic acids such as hydrochloric acid, hydrobromic acid, perchloric acid, nitric acid, thiocyanic acid, sulfuric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, propionic acid, glycolic acid, lactic acid, pyruvic acid, oxalic acid, malonic acid, succinic acid, maleic acid, and fumaric acid, or by reaction with an inorganic base such as sodium hydroxide, ammonium hydroxide, potassium hydroxide, and organic bases such as mono-, di-, trialkyl and aryl amines and substituted ethanolamines. Administration can be accomplished by single or multiple doses. The dose administered to a subject in the context of the present disclosure should be sufficient to induce a beneficial therapeutic response in a subject over time, or to inhibit or prevent infection. The dose required will vary from subject to subject depending on the species, age, weight and general condition of the subject, the severity of the infection being treated, the particular composition being used and its mode of administration. An appropriate dose can be determined by one of ordinary skill in the art using only routine experimentation. Multiple doses may be administered to a subject with a period of several days or a few weeks between consecutive administrations. For example, a polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention may be administered as a first dose, and a second dose of the polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation administered 3 to 12 weeks after the first dose. For example, a polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention may be administered at weeks 0, 4, and 12. Optionally a vaccine, polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention may be administered as a booster. Optionally a vaccine, polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention may be administered as part of a heterologous prime- boost protocol. For example, a first vaccine may be administered as a priming step, followed by vaccination using a vaccine, polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention vaccine as a booster. The first vaccine is a different vaccine to the booster. The first vaccine may be any suitable influenza vaccine. The booster may be administered at any suitable time after the first vaccine, for example within 4 weeks, 6 weeks, 8 weeks, 12 weeks, 6 months or more after the first vaccine. Optionally two or more doses of the first vaccine may be administered before administration of the booster. The booster may be administered at any suitable time after the second, third (or further) dose of the first vaccine, for example after 6 weeks, 8 weeks, 12 weeks, 6 months or more after the second (or further) dose of the first vaccine. Each dose of the first vaccine may be separate by at least 2 weeks, 3 weeks, 4 weeks, 6 weeks, 8 weeks, 12 weeks, 6 months or a year. Optionally a polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention is administered intramuscularly. Optionally a polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention is administered intramuscularly, intradermally, or subcutaneously, for example by needle or by gene gun, or electroporation, or by needle-free injection (for example, using a needle-free injection device of Pharmajet). Optionally a vaccine, polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention is administered by needle-free injection. Optionally a vaccine, polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention is administered intradermally by needle-free injection. Optionally a vaccine of the invention is administered intradermally by needle-free injection. Optionally a vector of the invention is administered intradermally by needle-free injection. Optionally a pharmaceutical composition of the invention comprising a vector or a polynucleotide is administered intradermally by needle-free injection. Optionally a polynucleotide of the invention is administered intradermally by needle-free injection. A vaccine of the invention may comprise any polypeptide, polynucleotide, vector, pharmaceutical composition, or combined preparation of the invention. The present disclosure includes methods comprising administering an RNA vaccine, an mRNA vaccine, or a DNA vaccine to a subject in need thereof. The exact amount required will vary from subject to subject, depending on the species, age, and general condition of the subject, the severity of the disease, the particular composition, its mode of administration, its mode of activity, and the like. The RNA or DNA is typically formulated in dosage unit form for ease of administration and uniformity of dosage. It will be understood, however, that the total daily usage of the RNA may be decided by the attending physician within the scope of sound medical judgment. The specific therapeutically effective, prophylactically effective, or appropriate imaging dose level for any particular patient will depend upon a variety of factors including the disorder being treated and the severity of the disorder; the activity of the specific compound employed; the specific composition employed; the age, body weight, general health, sex and diet of the patient; the time of administration, route of administration, and rate of excretion of the specific compound employed; the duration of the treatment; drugs used in combination or coincidental with the specific compound employed; and like factors well known in the medical arts. The effective amount of the RNA or DNA, as provided herein, may be as low as 20 pg, administered for example as a single dose or as two 10 pg doses. In some embodiments, the effective amount is a total dose of 20 μg-300 μg or 25 μg-300 μg. For example, the effective amount may be a total dose of 20 μg, 25 μg, 30 μg, 35 μg, 40 μg, 45 μg, 50 μg, 55 μg, 60 μg, 65 μg, 70 μg, 75 μg, 80 μg, 85 μg, 90 μg, 95 μg, 100 μg, 110 μg, 120 μg, 130 μg, 140 μg, 150 μg, 160 μg, 170 μg, 180 μg, 190 μg, 200 μg, 250 μg, or 300 μg. In some embodiments, the effective amount is a total dose of 20 μg. In some embodiments, the effective amount is a total dose of 25 pg. In some embodiments, the effective amount is a total dose of 50 μg. In some embodiments, the effective amount is a total dose of 75 μg. In some embodiments, the effective amount is a total dose of 100 μg. In some embodiments, the effective amount is a total dose of 150 μg. In some embodiments, the effective amount is a total dose of 200 μg. In some embodiments, the effective amount is a total dose of 250 pg. In some embodiments, the effective amount is a total dose of 300 μg. The RNA or DNA described herein can be formulated into a dosage form described herein, such as an intranasal, intratracheal, or injectable (e.g., intravenous, intraocular, intravitreal, intramuscular, intradermal, intracardiac, intraperitoneal, and subcutaneous). Optionally, an RNA (e.g., mRNA) or DNA vaccine is formulated in an effective amount to produce an antigen specific immune response in a subject. In some embodiments, the effective amount is a total dose of 25 μg to 1000 μg, or 50 μg to 1000 μg. In some embodiments, the effective amount is a total dose of 100 μg. In some embodiments, the effective amount is a dose of 25 μg administered to the subject a total of two times. In some embodiments, the effective amount is a dose of 100 μg administered to the subject a total of two times. In some embodiments, the effective amount is a dose of 400 μg administered to the subject a total of two times. In some embodiments, the effective amount is a dose of 500 μg administered to the subject a total of two times. Optionally, an effective amount is a dose of 100-300 μg administered to the subject at least two times. Optionally, an effective amount is a dose of 300-500 μg administered to the subject at least two times. Optionally, an effective amount is a dose of 500-700 μg administered to the subject at least two times. Optionally, an effective amount is a dose of 700-900 μg administered to the subject at least two times. Optionally, an effective amount is a dose of 900-1100 μg administered to the subject at least two times. Optionally, an effective amount is a dose of 1100-1300 μg administered to the subject at least two times. Optionally a first dose is administered to the subject at least two weeks before a second dose. Optionally a first dose is administered to the subject at least three weeks before a second dose. Optionally a dosage of between 10 μg / kg and 400 μg / kg of the nucleic acid vaccine is administered to the subject. In some embodiments the dosage of the RNA or DNA polynucleotide (or nucleic acid) is 1-5 μg, 5-10 μg, 10-15 μg, 15-20 μg, 10-25 μg, 20-25 μg, 20-50 μg, 30-50 μg, 40-50 μg, 40-60 μg, 60-80 μg, 60-100 μg, 50-100 μg, 80-120 μg, 40-120 μg, 40-150 μg, 50-150 μg, 50-200 μg, 80-200 μg, 100-200 μg, 120-250 μg, 150-250 μg, 180- 280 μg, 200-300 μg, 50-300 μg, 80-300 μg, 100-300 μg, 40-300 μg, 50-350 μg, 100-350 μg, 200-350 μg, 300-350 μg, 320-400 μg, 40-380 μg, 40-100 μg, 100-400 μg, 200-400 μg, or 300- 400 μg per dose. In some embodiments, the nucleic acid vaccine is administered to the subject by intradermal or intramuscular injection. In some embodiments, the nucleic acid vaccine is administered to the subject on day zero. In some embodiments, a second dose of the nucleic acid vaccine is administered to the subject on day twenty one. In a strategy called “prime-boost”, a first dose of a vaccine (for example, a nucleic acid vaccine, or mRNA vaccine) is given as a priming step, followed by a second dose as a booster. The prime-boost strategy aims to provide a stronger overall immune response. The boost may be administered at least a day, at least a week, or at least two, three, four, five, six, or seven weeks, or at least two, three, four, five, or six months after the primer. For example, the boost may be administered at least three weeks after the primer. Pharmaceutically acceptable carriers, excipients, diluents Pharmaceutical compositions of the invention may be administered in any suitable manner, such as with pharmaceutically acceptable carriers, excipients or diluents. Pharmaceutically acceptable carriers, excipients or diluents are determined in part by the particular composition being administered, as well as by the particular method used to administer the composition. Preparations for parenteral administration include sterile aqueous or nonaqueous solutions, suspensions, and emulsions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers, excipients or diluents include water, alcoholic / aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer’s dextrose, dextrose and sodium chloride, lactated Ringer’s, or fixed oils. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers (such as those based on Ringer’s dextrose), and the like. Preservatives and other additives may also be present such as, for example, antimicrobials, anti-oxidants, chelating agents, and inert gases and the like. Preservatives and other additives may also be present such as, for example, antimicrobials, anti-oxidants, chelating agents, and inert gases and the like. An aqueous carrier, excipient, or diluent for parenteral administration (for example intradermal, or subcutaneous administration) may comprise phosphate-buffered saline (PBS). Some of the compositions may potentially be administered as a pharmaceutically acceptable acid- or base-addition salt, formed by reaction with inorganic acids such as hydrochloric acid, hydrobromic acid, perchloric acid, nitric acid, thiocyanic acid, sulfuric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, propionic acid, glycolic acid, lactic acid, pyruvic acid, oxalic acid, malonic acid, succinic acid, maleic acid, and fumaric acid, or by reaction with an inorganic base such as sodium hydroxide, ammonium hydroxide, potassium hydroxide, and organic bases such as mono-, di-, trialkyl and aryl amines and substituted ethanolamines. Pharmaceutically acceptable carriers, excipients, or diluents include, but are not limited to, saline, buffered saline, dextrose, water, glycerol, ethanol, and combinations thereof. The carrier and composition can be sterile, and the formulation suits the mode of administration. The composition can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. A pharmaceutically acceptable composition can be a liquid solution, suspension, emulsion, tablet, pill, capsule, sustained release formulation, or powder. The composition can be formulated as a suppository, with traditional binders and carriers such as triglycerides. Oral formulations can include standard carriers such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, and magnesium carbonate. Any of the common pharmaceutical carriers, such as sterile saline solution or sesame oil, can be used. The medium can also contain conventional pharmaceutical adjunct materials such as, for example, pharmaceutically acceptable salts to adjust the osmotic pressure, buffers, preservatives and the like. Other media that can be used with the compositions and methods provided herein are normal saline and sesame oil. In some embodiments, the compositions comprise a pharmaceutically acceptable carrier and / or an adjuvant. For example, the adjuvant can be alum, Freund’s complete adjuvant, a biological adjuvant or immunostimulatory oligonucleotides (such as CpG oligonucleotides). Pharmaceutically acceptable carriers (vehicles) useful in this disclosure are conventional. Remington’s Pharmaceutical Sciences, by E. W. Martin, Mack Publishing Co., Easton, PA, 15thEdition (1975), describes compositions and formulations suitable for pharmaceutical delivery of one or more therapeutic compositions, such as one or more influenza vaccines, and additional pharmaceutical agents. In general, the nature of the carrier will depend on the particular mode of administration being employed. For instance, parenteral formulations usually comprise injectable fluids that include pharmaceutically and physiologically acceptable fluids such as water, physiological saline, balanced salt solutions, aqueous dextrose, glycerol or the like as a vehicle. For solid compositions (for example, powder, pill, tablet, or capsule forms), conventional non-toxic solid carriers can include, for example, pharmaceutical grades of mannitol, lactose, starch, or magnesium stearate. In addition to biologically-neutral carriers, pharmaceutical compositions to be administered can contain minor amounts of non-toxic auxiliary substances, such as wetting or emulsifying agents, preservatives, and pH buffering agents and the like, for example sodium acetate or sorbitan monolaurate. A pharmaceutical composition of the invention may further comprise an adjuvant for enhancing an immune response in a subject to a polypeptide, or to a polypeptide encoded by a nucleotide, of the composition. Viral Pseudotypes There is also provided according to the invention a pseudotyped virus particle comprising a polypeptide of the invention. Pseudotyping is the process of producing viruses or viral vectors in combination with foreign viral envelope proteins. The result is a pseudotyped virus particle. Pseudotyped particles do not carry the genetic material to produce additional viral envelope proteins, so the phenotypic changes cannot be passed on to progeny viral particles. A “pseudotype” may be defined as a hybrid virus particle comprising a protein nucleocapsid (‘core’) encasing a nucleic acid (RNA or DNA) genome, with the core itself being encapsulated in a lipid ‘envelope’ membrane derived from the host cell. This envelope gained when cores exit from the cell by ‘budding’ includes proteins derived from other viruses. Many of these heterologous envelope proteins are antigenic targets for the host immune system. In pseudotypes, one or more of these envelope proteins may derive from study viruses. Many pseudotypes also carry foreign genes, called ‘transfer’ genes, engineered into their genome. When in the presence of susceptible cells, the envelope proteins bind to cell receptors permitting cellular entry, eventually resulting in transfer gene expression. Rhabdoviruses (e.g. Vesicular Stomatitis Virus, VSV) and Retroviruses (e.g. Lentiviruses) have been extensively exploited as cores for pseudotyping. In the case of retroviruses, their key characteristic is the ability to reverse transcribe their dimeric single-stranded RNA genome into a double-stranded deoxyribonucleic acid (dsDNA) copy, which is subsequently integrated into the cell genome via the use of viral and cellular enzymes. For retroviral pseudotypes, this usually leads to expression of the transfer / reporter gene, the latter being readily quantifiable. Reporter gene expression directly correlates with efficiency of viral envelope / receptor interaction, and conversely whether individual antibody responses or antiviral agents could interfere with the entry and replication process of the native virus. Binding of viral pseudotypes to broadly neutralizing antigen-binding molecules may be measured using any suitable technique known to the skilled person, for example by haemagglutination inhibition (HI) assay, or by enzyme-linked immunosorbent assay (ELISA). ELISA analysis of antibody binding to glycoprotein (GP) is described in Saphire et al., 2018 (Cell 174(4): 938-952) in relation to analysis of monoclonal antibodies against Ebola virus GP. Production of retroviral pseudotypes, and their use in pseudotype neutralisation assays and immunogenicity testing, is reviewed in detail in Temperton et al., 2015 (Retroviral Pseudotypes – From Scientific Tools to Clinical Utility. In: eLS. John Wiley & Sons, Ltd: Chichester. DOI: 10.1002 / 9780470015902.a0021549.pub2). Representatives of all seven genera of retroviruses have been employed in pseudotyping studies but to date only gammaretroviral or lentiviral pseudotypes are widely used. Lentiviruses are a genus of the Retroviridae family, which unlike gammaretroviruses, can infect non-proliferating cells, which makes them amenable for gene therapy applications involving highly differentiated or quiescent cells (e.g. in G0 cell cycle phase) including muscle or neurons. The most common lentivirus vector used for pseudotyping is HIV-type 1 (HIV-1), although simian immunodeficiency virus has also been employed. Generation of retroviral pseudotypes is achieved through the introduction of cloned versions of foreign envelope protein gene(s), core retroviral genes and transfer gene (e.g. reporter or therapeutic gene) concurrently into producer cells, normally highly transfectable cell lines such as human embryo kidney (HEK) 293 clone 17 T cells (American Type Culture Collection #CRL-11268) (Pear et al., 1993, PNAS USA 90: 8392-8396). 1. The envelope plasmid. Envelope gene(s) of the study virus are cloned into an appropriate expression plasmid. Genes are usually derived via polymerase chain reaction amplification of viral cDNA using specific primers or from custom gene synthesis. Some expression vectors are commercially available and utilise different, usually strong constitutive gene promoters (e.g. from the human cytomegalovirus (CMV) immediate early gene), which can influence the efficacy of pseudotype generation. 2. The retroviral gag–pol plasmid. The gag and pol genes encode polyproteins which are subsequently cleaved to release structural proteins (including matrix, capsid and nucleocapsid) found within the core, and proteins involved in viral replication (protease, reverse transcriptase and integrase) responsible for processing the structural proteins, converting the ssRNA viral genome into dsDNA and ensuring integration (of the transfer gene) into the host cell genome. In addition, in a lentiviral gag–pol construct, the rev gene is included. The Rev protein is involved in the export of viral mRNAs from nucleus to cytosol for translation. 3. The transfer / reporter plasmid. This is the gene that is stably integrated into the host cell DNA, from where the gene is expressed via various cis-acting transcriptional elements. The transfer plasmid contains a packaging signal upstream of the gene to ensure incorporation of viral RNA containing the gene into the viral core during pseudotype generation. Once the cellular machinery has transcribed and translated the transfected genes, an RNA dimer of the transfer gene (region between the long terminal repeats; LTR) is incorporated into the pseudotype via the packaging signal. As the transfer plasmid is the only one engineered to contain a packaging signal, no other nucleic acids are incorporated into the mature pseudotype particle. A domain at the N-terminus of Gag targets the nucelocapsid to the cell plasma membrane, into which the envelope protein(s) has been inserted. The pseudotype particles budding from the cell are encapsulated in the cell membrane, which forms the viral envelope. Pseudotyped viruses are released into the producer cell culture medium. This supernatant can be titrated onto target cells to measure the concentration of functional particles. These attach to the cells via envelope protein–receptor interaction, followed by membrane fusion and internalisation. The pseudotype genome, bearing the transfer / reporter gene is integrated into the host cell DNA, from where it is expressed. The level of reporter gene expression correlates with the level of transduction by viable particles. As only the transfer gene is present in the pseudotype, no viral proteins are produced in target cells, so further pseudotype production and propagation does not occur. This provides safety in working with pseudotypes compared to working with the wildtype virus. Green fluorescent protein (GFP)-based pseudotypes are readily titrated using fluorescence microscopy or flow cytometry, luciferase pseudotypes by luminometry, and beta-galactosidase (β-gal) pseudotypes by colour reaction. Many standard serological assays measure only antibody binding (hemagglutination inhibition (HI) and ELISA), rather than the inhibition of viral infectivity. Neutralisation assays allow for sensitive detection of functional antibody responses. For high-containment viruses (such as Ebola), however, these assays are not widely applicable owing to the requirement for high biosafety laboratory facilities and specially trained personnel. Using retroviral and lentiviral particles pseudotyped with the envelopes of such pathogens as ‘surrogate viruses’ for use in neutralisation assays is one way of circumventing this issue. Using a pseudotype strategy, only the envelope protein(s) of the virus is required, with no possibility of recombination or native virus escape. These pseudotypes undergo abortive replication and are unable to give rise to replication-competent progeny. Pseudotypes are excellent serological reagents for virus neutralisation assays as the virions can contain a reporter gene and bear heterologous viral envelope proteins on the surface. The transfer of these reporter genes to target cells depends on the function of the viral envelope protein; therefore, the titre of neutralising antibodies against the envelope can be measured by a reduction in reporter gene transfer and expression. PV neutralisation assays have now been developed for a wide range of RNA viruses, from numerous virus families (see Table 1 of Temperton et al., supra). Pseudotype-based influenza neutralisation assays have been shown to be highly efficient for the measurement of broadly-neutralising antibodies making them ideal serological tools for the study of cross-reactive responses against multiple subtypes with pandemic potential (Corti et al., 2011, Science 333 (6044): 850-856). Production of lentiviral vectors pseudotyped with filoviral glycoproteins is described in Sinn et al., 2017 (Methods Mol Biol.2017;1628:65-78). An example of a suitable general method for production of viral pseudotypes is as follows: For transfection, 5x106HEK-293T cells are plated 24 h prior to addition of a complex comprising plasmid DNA and PEI, which facilitates DNA transport into the cells. A retroviral gag-pol plasmid and a reporter plasmid are transfected concurrently with the required envelope plasmid. An example of a suitable neutralization assay is as follows: In a 96-well plate, ~100xTCID50 pseudotyped virus that resulted in an output of 1x105relative light units (RLU) is incubated with dilutions of sera for 1 h at 37% (5% CO2) before the addition of 1x104target cells. These are incubated for a further 48 h, after which the media is removed and replaced with a 50:50 mix of fresh media and luciferase reagent. Luciferase activity is detected 2.5 min later by reading the plates on a luminometer. For all results, background RLU (virus alone or DEnv) is deducted before analysis. Saphire et al. (supra) describes three independent assays for evaluation of mAb neutralization in relation to analysis of monoclonal antibodies against Ebola virus GP: i) biologically contained EBOV (ΔVP30) (Halfmann et al., 2008, Proc Natl Acad Sci USA.2008; 105:1129–1133); and ii) authentic EBOV performed under BSL-2+, BSL-3 and BSL-4 containment; and iii) replication-competent vesicular stomatitis virus bearing EBOV GP (rVSV). Conservative Amino acid Substitutions A polypeptide of the invention, or for use in the invention, may include one or more conservative amino acid substitutions. Conservative amino acid substitutions are those substitutions that, when made, least interfere with the properties of the original polypeptide, that is, the structure and especially the function of the protein is conserved and not significantly changed by such substitutions. Examples of conservative substitutions are shown below: Original Residue Conservative Substitutions Ala Ser Arg Lys Asn Gln, His Asp Glu Cys Ser Gln Asn Glu Asp His Asn; Gln Ile Leu, Val Leu Ile; Val Lys Arg; Gln; Met Leu; Ile Phe Met; Leu; Tyr Ser Thr Thr Ser Trp Tyr Tyr Trp; Phe Val Ile; Leu Conservative substitutions generally maintain (a) the structure of the polypeptide backbone in the area of the substitution, for example, as a sheet or helical conformation, (b) the charge or hydrophobicity of the molecule at the target site, or (c) the bulk of the side chain. The substitutions which in general are expected to produce the greatest changes in protein properties will be non-conservative, for instance changes in which (a) a hydrophilic residue, for example, serine or threonine, is substituted for (or by) a hydrophobic residue, for example, leucine, isoleucine, phenylalanine, valine or alanine; (b) a cysteine or proline is substituted for (or by) any other residue; (c) a residue having an electropositive side chain, for example, lysine, arginine, or histidine, is substituted for (or by) an electronegative residue, for example, glutamate or aspartate; or (d) a residue having a bulky side chain, for example, phenylalanine, is substituted for (or by) one not having a side chain, for example, glycine. Sequence identity The similarity between amino acid or nucleic acid sequences is expressed in terms of the similarity between the sequences, otherwise referred to as sequence identity. Sequence identity is frequently measured in terms of percentage identity (or similarity or homology); the higher the percentage, the more similar the two sequences are. Homologs or variants of a given gene or protein will possess a relatively high degree of sequence identity when aligned using standard methods. Methods of alignment of sequences for comparison are well known in the art. Various programs and alignment algorithms are described in: Smith and Waterman, Adv. Appl. Math.2:482, 1981; Needleman and Wunsch, J. Mol. Biol.48:443, 1970; Pearson and Lipman, Proc. Natl. Acad. Sci. U.S.A.85:2444, 1988; Higgins and Sharp, Gene 73:237- 244, 1988; Higgins and Sharp, CABIOS 5:151-153, 1989; Corpet et al., Nucleic Acids’ Research 16:10881-10890, 1988; and Pearson and Lipman, Proc. Natl. Acad. Sci. U.S.A. 85:2444, 1988. Altschul et al., Nature Genet. 6:119-129, 1994. The NCBI Basic Local Alignment Search Tool (BLASTTM) (Altschul et al., J. Mol. Biol.215:403-410, 1990) is available from several sources, including the National Center for Biotechnology Information (NCBI, Bethesda, MD) and on the Internet, for use in connection with the sequence analysis programs blastp, blastn, blastx, tblastn and tblastx. Sequence identity between nucleic acid sequences, or between amino acid sequences, can be determined by comparing an alignment of the sequences. When an equivalent position in the compared sequences is occupied by the same nucleotide, or amino acid, then the molecules are identical at that position. Scoring an alignment as a percentage of identity is a function of the number of identical nucleotides or amino acids at positions shared by the compared sequences. When comparing sequences, optimal alignments may require gaps to be introduced into one or more of the sequences to take into consideration possible insertions and deletions in the sequences. Sequence comparison methods may employ gap penalties so that, for the same number of identical molecules in sequences being compared, a sequence alignment with as few gaps as possible, reflecting higher relatedness between the two compared sequences, will achieve a higher score than one with many gaps. Calculation of maximum percent identity involves the production of an optimal alignment, taking into consideration gap penalties. Suitable computer programs for carrying out sequence comparisons are widely available in the commercial and public sector. Examples include MatGat (Campanella et al., 2003, BMC Bioinformatics 4: 29; program available from http: / / bitincka.com / ledion / matgat), Gap (Needleman & Wunsch, 1970, J. Mol. Biol.48: 443-453), FASTA (Altschul et al., 1990, J. Mol. Biol.215: 403-410; program available from http: / / www.ebi.ac.uk / fasta), Clustal W 2.0 and X 2.0 (Larkin et al., 2007, Bioinformatics 23: 2947-2948; program available from http: / / www.ebi.ac.uk / tools / clustalw2) and EMBOSS Pairwise Alignment Algorithms (Needleman & Wunsch, 1970, supra; Kruskal, 1983, In: Time warps, string edits and macromolecules: the theory and practice of sequence comparison, Sankoff & Kruskal (eds), pp 1-44, Addison Wesley; programs available from http: / / www.ebi.ac.uk / tools / emboss / align). All programs may be run using default parameters. For example, sequence comparisons may be undertaken using the “needle” method of the EMBOSS Pairwise Alignment Algorithms, which determines an optimum alignment (including gaps) of two sequences when considered over their entire length and provides a percentage identity score. Default parameters for amino acid sequence comparisons (“Protein Molecule” option) may be Gap Extend penalty: 0.5, Gap Open penalty: 10.0, Matrix: Blosum 62. The sequence comparison may be performed over the full length of the reference sequence. Corresponding positions Sequences described herein include reference to an amino acid sequence comprising an amino acid residue “at a position corresponding to an amino acid residue position” of another sequence. Such corresponding positions may be identified, for example, from an alignment of the sequences using a sequence alignment method described herein, or another sequence alignment method known to the person of ordinary skill in the art. The terms “polynucleotide”, “nucleotide”, and “nucleic acid” are used interchangeably herein. Embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a representation of Influenza A H5 phylogenetic tree featuring various clades; Figure 2(i) shows a study schedule of immunisation of DIOS (i.e. optimised) H5 vaccines in chickens. Chickens from Groups 1-2 (Table 1) were administered with 100 µg DNA of the indicated construct on days 0 and 14. For Group 3, chickens were administered with 50 µg of each of the two constructs indicated, for a total of 100 µg. Bleeds were taken pre-immunisation and on day 28. Figure 2(ii) shows neutralisation of a panel of influenza H5 PVs in chickens (n=10) after 2 vaccinations (day 28). Chickens were immunised with vaccines indicated in Table 1 according to bleed schedule shown in Figure 2(i), and the antisera generated was assayed against a panel of H5 PVs; Figure 3 shows a heatmap illustrating number of chickens (n=10) that elicited an immune response above the threshold values against representative H5 PV from various clades. Heatmap legend (number of chickens): Black=10, White=0; Figure 4 shows a representation of influenza H5 clade 2.3.4.4 phylogenetic tree; Figure 5 shows a neuraminidase inhibition activity in chickens (n=10) after 2 vaccinations (day 28). Chickens were immunised with vaccines indicated in table 1 according to bleed schedule shown in Figure 2(i), and the antisera generated was assayed against various N1 PVs; Figure 6 shows a heatmap illustrating number of chickens (n=10) that elicited an immune response above the threshold values against representative N1 PV from different species. Heatmap legend (number of chickens): Black=10, White=0; Figure 7 shows a study schedule of immunisation of DIOS H5 vaccines in mice. Mice from Groups 1-3 (Table 3) were administered with 50 µg DNA of the indicated construct on days 0, 28, and 56. Bleeds were taken pre-immunisation, on day 26, 54, and terminally at day 84; Figure 8 shows neutralisation of a panel of influenza H5 PVs in mice (n=6) after 3 vaccinations (day 84). Mice were immunised with vaccines indicated in Table 3 according to bleed schedule shown in Figure 7, and the antisera was assayed against a panel of H5 PVs; and Figure 9 shows a heatmap illustrating number of mice (n=6) that elicited an immune response above the threshold values against representative H5 PV from various clades Heatmap legend number of mice: Black=6, White=0 Sequence listing Table SEQ ID NO: Description 1 T2_HA_9 amino acid sequence (also referred to by the Applicant as T2_HA_1 in other patent applications) 2 T2_HA_9 nucleic acid sequence 3 T4_HA_2 amino acid sequence 4 T4_HA_2 nucleic acid sequence 5 T2_NA_3 amino acid sequence 6 T2_NA_3 nucleic acid sequence 7 T2_M2_1 amino acid sequence 8 T2_M2_1 nucleic acid sequence 9 S3_T2_3 (T2_HA_9 – T2_NA_3 – T2_M2_1) nucleic acid sequence 10 S3_T2_12 (T4_HA_2 – T2_NA_3 – T2_M2_1) nucleic acid sequence 11 Consensus Kozak sequence 12 Elongated Kozak sequence 13 2A self-cleaving peptide sequence GSGEGRGSLLTCGDVEENPGP 14 2A self-cleaving peptide sequence GSGATNFSLLKQAGDVEENPGP 15 Additional S3_T2_3 (T2_HA_9 – T2_NA_3 – T2_M2_1) nucleic acid sequence 16 Additional S3_T2_12 (T4_HA_2 – T2_NA_3 – T2_M2_1) nucleic acid sequence

[0002] The following amino acid and nucleic acid (nucleotide sequences) are referred to herein: > T2_HA_9 (SEQ ID NO:1) Amino acid sequence: MEKIVLLLAIVSLVKSDQICIGYHANNSTEQVDTIMEKNVTVTHAQDILEKTHNGKLCDLDGVKPLIL RDCSVAGWLLGNPMCDEFINVPEWSYIVEKANPANDLCYPGNFNDYEELKHLLSRINHFEKIQIIPKS SWSDHEASSGVSSACPYQGRSSFFRNVVWLIKKNNAYPTIKRSYNNTNQEDLLVLWGIHHPNDAAEQT RLYQNPTTYISVGTSTLNQRLVPKIATRSKVNGQSGRMEFFWTILKPNDAINFESNGNFIAPEYAYKI VKKGDSAIMKSELEYGNCNTKCQTPMGAINSSMPFHNIHPLTIGECPKYVKSNRLVLATGLRNSPQRE RRRKKRGLFGAIAGFIEGGWQGMVDGWYGYHHSNEQGSGYAADKESTQKAIDGVTNKVNSIIDKMNTQ FEAVGREFNNLERRIENLNKKMEDGFLDVWTYNAELLVLMENERTLDFHDSNVKNLYDKVRLQLRDNA KELGNGCFEFYHKCDNECMESVRNGTYDYPQYSEEARLKREEISGVKLESIGTYQILSIYSTVASSLA LAIMVAGLSLWMCSNGSLQCRICI > T2_HA_9 (SEQ ID NO:2) Nucleic acid sequence: atggaaaagattgtgctgctgctggccatcgtgtccctggtcaagagcgatcaaatctgcatcggcta ccacgccaacaacagcaccgaacaggtggacaccattatggaaaagaacgtgaccgtgacacacgccc aggacatcctggaaaagacccacaacggcaagctgtgcgacctggatggcgtgaagcctctgatcctg agagattgctctgtggccggctggctgctgggcaatcctatgtgcgacgagttcatcaacgtgcccga gtggtcctatatcgtggaaaaggccaatcctgccaacgacctgtgctaccccggcaacttcaacgact acgaggaactgaaacatctgctgagccggatcaaccacttcgagaagatccagatcatccccaagtcc tcttggagcgatcacgaggcctctagcggagtgtctagcgcctgtccttaccaaggcagaagcagctt cttccggaacgtcgtgtggctgatcaagaagaacaacgcttaccccaccatcaagcggagctacaaca acaccaatcaagaggacctgctggtgctgtggggcatccaccatcctaatgatgccgccgagcagacc cggctgtaccagaatcctacaacctacatcagcgtgggcaccagcacactgaaccagagactggtgcc taagatcgccaccagatccaaagtgaacggccagagcggccggatggaattcttctggaccatcctga agcctaacgacgccatcaacttcgagagcaacggcaactttatcgcccctgagtacgcctacaagatc gtgaagaagggcgacagcgccatcatgaagtccgagctggaatacggcaactgcaacaccaagtgtca gacccctatgggcgccatcaatagcagcatgcccttccacaacattcaccctctgaccatcggcgagt gccccaaatacgtgaagtccaacagactggtcctggccaccggcctgagaaattctccacagagagag cggcgcagaaagaagagaggcctgtttggagccattgccggctttatcgaaggcggctggcaaggcat ggttgacggatggtacggctatcaccacagcaatgagcaaggctctggctacgccgccgacaaagaga gcacacagaaagccatcgacggcgtgaccaacaaagtgaatagcatcatcgacaagatgaacacccag ttcgaggccgtgggcagagagttcaacaacctggaaagacggatcgagaacctgaacaagaagatgga ggacggcttcctggacgtgtggacctataatgccgagctgctggtcctgatggaaaacgagagaaccc tggacttccacgacagcaacgtgaagaacctgtacgacaaagtgcggctccagctgcgggacaatgcc aaagaactcggcaacggctgcttcgagttctaccacaagtgcgacaacgagtgcatggaaagcgtgcg gaacggcacctacgactaccctcagtactctgaggaagcccggctgaagagagaagagatcagcggag tgaagctggaatccatcggcacataccagatcctgagcatctacagcaccgtggcctcttctctggcc ctggctattatggtggctggcctgagcctgtggatgtgctctaatggcagcctccagtgccggatctg catc >T4_HA_2 (SEQ ID NO:3) Amino acid sequence: MEKIVLLLAIVSLVKSDQICIGYHANNSTEQVDTIMEKNVTVTHAQDILEKTHNGKLCDLNGVKPLIL KDCSVAGWLLGNPMCDEFIRVPEWSYIVERANPANDLCFPGNLNDYEELKHLLSRINHFEKILIIPKS SWPNHETSLGVSAACPYQGTPSFFRNVVWLIKKNDAYPTIKISYNNTNREDLLILWGIHHSNNAAEQT NLYKNPTTYISVGTSTLNQRLVPKIATRSQVNGERGRMDFFWTILKPNDAIHFESNGNFIAPEYAYKI VKKGDSTIMKSEVEYGHCNTKCQTPIGAINSSMPFHNIHPLTIGECPKYVKSNKLVLATGLRNSPLRE KRRRKKRGLFGAIAGFIEGGWQGMVDGWYGYHHSNEQGSGYAADKESTQKAIDGVTNKVNSIIDKMNT QFEAVGREFNNLERRIENLNKKMEDGFLDVWTYNAELLVLMENERTLDFHDSNVKNLYDKVRLQLRDN AKELGNGCFEFYHKCDNECMESVRNGTYDYPQYSEEARLKREEISGVKLESIGTYQILSIYSTVASSL ALAIMVAGLSLWMCSNGSLQCRICI >T4_HA_2 (SEQ ID NO:4) Nucleic acid sequence: GTACCGCCACCATGGAAAAGATCGTGCTGCTGCTGGCCATCGTGTCCCTGGTCAAGAGCGACCAAATC TGCATCGGCTACCACGCCAACAACAGCACCGAACAGGTGGACACCATTATGGAAAAGAACGTCACCGT GACACACGCCCAGGACATCCTGGAAAAGACCCACAACGGCAAGCTGTGCGACCTGAACGGCGTGAAGC CTCTGATCCTGAAGGATTGCTCTGTGGCCGGATGGCTGCTGGGCAATCCCATGTGCGACGAGTTCATC AGAGTGCCCGAGTGGTCCTACATCGTGGAAAGAGCCAATCCTGCCAACGACCTGTGCTTCCCCGGCAA CCTGAACGACTACGAGGAACTGAAGCACCTCCTGAGCCGGATCAACCACTTCGAGAAGATCCTGATCA TCCCCAAGAGCAGCTGGCCCAACCACGAGACATCTCTGGGAGTGTCTGCCGCATGTCCATACCAGGGC ACCCCTAGCTTTTTCCGGAACGTCGTGTGGCTGATCAAGAAGAACGACGCTTACCCCACCATCAAGAT CAGCTACAACAACACCAACCGCGAGGACCTGCTGATCCTGTGGGGAATCCACCACAGCAACAATGCCG CCGAGCAGACCAACCTGTACAAGAACCCCACCACCTACATCAGCGTGGGCACCAGCACACTGAACCAG AGACTGGTGCCTAAGATCGCCACACGGTCCCAAGTGAATGGCGAGAGGGGCAGAATGGACTTCTTCTG GACCATCCTGAAGCCTAACGACGCCATCCACTTTGAGAGCAACGGCAACTTTATCGCCCCTGAGTACG CCTACAAGATCGTGAAGAAGGGCGACAGCACCATCATGAAGTCCGAGGTGGAATACGGCCACTGCAAC ACCAAGTGTCAGACCCCTATCGGCGCCATCAACTCCAGCATGCCCTTCCACAACATTCACCCTCTGAC CATCGGCGAGTGCCCCAAATACGTGAAGTCCAACAAGCTGGTGCTGGCTACCGGCCTGAGAAACAGCC CTCTGAGAGAGAAGCGCAGACGGAAGAAGAGAGGCCTGTTTGGCGCCATTGCCGGCTTTATCGAAGGC GGCTGGCAAGGCATGGTGGACGGATGGTACGGCTACCATCACAGCAACGAGCAAGGCTCTGGATACGC CGCCGACAAAGAGAGCACCCAGAAAGCCATTGACGGCGTGACCAACAAAGTGAACAGCATCATCGACA AGATGAACACCCAGTTCGAGGCCGTGGGCAGAGAGTTCAACAACCTGGAACGGCGGATCGAGAATCTG AACAAGAAGATGGAGGACGGCTTCCTGGACGTGTGGACCTACAATGCCGAGCTGCTGGTCCTGATGGA AAACGAGAGAACCCTGGACTTCCACGACTCCAACGTGAAGAACCTGTACGACAAAGTGCGGCTCCAGC TGCGGGACAACGCCAAAGAACTCGGCAACGGCTGCTTCGAGTTCTACCACAAGTGCGACAACGAGTGC ATGGAAAGCGTGCGGAACGGCACCTACGACTACCCTCAGTACAGCGAGGAAGCCCGGCTGAAGAGAGA AGAGATCAGCGGAGTGAAGCTGGAATCCATCGGCACATACCAGATCCTGTCCATCTACAGCACCGTGG CCTCTTCTCTGGCCCTGGCCATTATGGTGGCTGGCCTGTCTCTGTGGATGTGCAGCAATGGCAGCCTC CAGTGCCGGATCTGCATCTGAGCGGCC > T2_NA_3 (SEQ ID NO:5) Amino acid sequence: MNPNQKIITIGSICMVVGIISLILQIGNIISIWVSHSIQTGNQNQPETCNQSIITYENNTWVNQTYVN ISNTNFVAEQAVASVALAGNSSLCPISGWAIYSKDNGIRIGSKGDVFVIREPFISCSHLECRTFFLTQ GALLNDKHSNGTVKDRSPYRTLMSCPVGEAPSPYNSRFESVAWSASACHDGISWLTIGISGPDNGAVA VLKYNGIITDTIKSWRNNILRTQESECACINGSCFTIMTDGPSNGQASYKIFKIEKGKVVKSVELNAP NYHYEECSCYPDAGEVMCVCRDNWHGSNRPWVSFNQNLEYQIGYICSGVFGDNPRPNDGTGSCGPVSS NGAYGVKGFSFKYGKGVWIGRTKSTSSRSGFEMIWDPNGWTETDSSFSVKQDIVAITDWSGYSGSFVQ HPELTGLDCMRPCFWVELIRGRPKENTIWTSGSSISFCGVNSDTVGWSWPDGAELPFTIDK >T2_NA_3 (SEQ ID NO:6) Nucleic acid sequence: atgaatccaaatcagaaaataataaccattgggtcaatctgtatggtagttggaataatcagcctaat attacaaattgggaacataatctcaatatgggttagccattcaattcagactggaaatcaaaaccaac ctgaaacatgcaaccaaagcatcattacttatgaaaacaacacttgggtgaatcaaacatatgttaac atcagcaataccaattttgttgctgaacaggctgtagcttcagtggcattagcgggcaattcctctct ctgccccattagtgggtgggctatatacagcaaggacaatggcataaggattggttccaagggagatg tatttgtcataagagagccattcatttcatgctcccacttggaatgcaggaccttttttctgactcaa ggagccttgttgaatgacaaacattccaatggaaccgttaaagacagaagcccctacagaaccttaat gagctgtcctgttggtgaggctccctctccatacaattcaaggtttgagtcggttgcttggtcagcaa gtgcttgccatgatggcattagctggttgacaattggaatttccgggccagacaatggggcagtggct gtattgaaatacaatggcataataacagacactatcaaaagttggagaaacaacatattgaggacaca agagtctgaatgtgcctgcataaatggttcttgctttactataatgaccgatggaccaagtaatgggc aggcctcatacaagattttcaagatagagaaggggaaggtagtcaaatcagtcgagttgaatgcccct aattaccactacgaggaatgttcctgttatcctgatgctggcgaagtaatgtgtgtgtgcagggataa ttggcatggttcgaatcgaccatgggtgtctttcaatcaaaatctggagtatcaaataggatacatat gcagtggggttttcggagacaatccacgccccaatgatggaacaggcagctgtggtccagtgtcttct aatggagcatatggagtaaagggattttcatttaagtacggcaagggtgtttggatagggagaactaa gagcactagttccaggagtggatttgagatgatttgggatcccaatggatggacagagacagatagta gtttctcagtgaagcaagatattgtagcaataactgattggtcaggatatagcgggagttttgtccaa catccagaattaacagggctggactgcatgaggccttgcttctgggttgaactaatcagaggacggcc taaggagaacacaatctggactagtgggagcagcatttccttctgtggtgtaaatagcgacactgtgg gttggtcttggccagacggtgctgagttgccattcaccattgacaag > T2_M2_1 (SEQ ID NO:7) Amino acid sequence: MSLLTEVETPTRNGWECRCSDSSDPLVIAASIIGILHLILWILDRLFFKCIYRRLKYGLKRGPSTEGV PESMREEYRQKQQSAVDVDDGHFVNIELE > T2_M2_1 (SEQ ID NO:8) Nucleic acid sequence: ATGTCTCTGCTGACCGAGGTGGAAACCCCTACCAGAAATGGCTGGGAGTGCAGATGCAGCGACAGCAG CGATCCTCTGGTTATCGCCGCCAGCATCATCGGCATCCTGCACCTGATCCTGTGGATCCTGGACCGGC TGTTCTTCAAGTGCATCTACCGGCGGCTGAAGTACGGCCTGAAGAGAGGCCCTTCTACAGAGGGCGTG CCCGAGAGCATGCGGGAAGAGTACAGACAGAAACAGCAGAGCGCCGTGGACGTGGACGATGGCCACTT CGTGAACATCGAGCTGGAA >S3_T2_3 (SEQ ID NO:9) Nucleic acid sequence: ATGGAAAAGATTGTGCTGCTGCTGGCCATCGTGTCCCTGGTCAAGAGCGATCAAATCTGCATCGGCTA CCACGCCAACAACAGCACCGAACAGGTGGACACCATTATGGAAAAGAACGTGACCGTGACACACGCCC AGGACATCCTGGAAAAGACCCACAACGGCAAGCTGTGCGACCTGGATGGCGTGAAGCCTCTGATCCTG AGAGATTGCTCTGTGGCCGGCTGGCTGCTGGGCAATCCTATGTGCGACGAGTTCATCAACGTGCCCGA GTGGTCCTATATCGTGGAAAAGGCCAATCCTGCCAACGACCTGTGCTACCCCGGCAACTTCAACGACT ACGAGGAACTGAAACATCTGCTGAGCCGGATCAACCACTTCGAGAAGATCCAGATCATCCCCAAGTCC TCTTGGAGCGATCACGAGGCCTCTAGCGGAGTGTCTAGCGCCTGTCCTTACCAAGGCAGAAGCAGCTT CTTCCGGAACGTCGTGTGGCTGATCAAGAAGAACAACGCTTACCCCACCATCAAGCGGAGCTACAACA ACACCAATCAAGAGGACCTGCTGGTGCTGTGGGGCATCCACCATCCTAATGATGCCGCCGAGCAGACC CGGCTGTACCAGAATCCTACAACCTACATCAGCGTGGGCACCAGCACACTGAACCAGAGACTGGTGCC TAAGATCGCCACCAGATCCAAAGTGAACGGCCAGAGCGGCCGGATGGAATTCTTCTGGACCATCCTGA AGCCTAACGACGCCATCAACTTCGAGAGCAACGGCAACTTTATCGCCCCTGAGTACGCCTACAAGATC GTGAAGAAGGGCGACAGCGCCATCATGAAGTCCGAGCTGGAATACGGCAACTGCAACACCAAGTGTCA GACCCCTATGGGCGCCATCAATAGCAGCATGCCCTTCCACAACATTCACCCTCTGACCATCGGCGAGT GCCCCAAATACGTGAAGTCCAACAGACTGGTCCTGGCCACCGGCCTGAGAAATTCTCCACAGAGAGAG CGGCGCAGAAAGAAGAGAGGCCTGTTTGGAGCCATTGCCGGCTTTATCGAAGGCGGCTGGCAAGGCAT GGTTGACGGATGGTACGGCTATCACCACAGCAATGAGCAAGGCTCTGGCTACGCCGCCGACAAAGAGA GCACACAGAAAGCCATCGACGGCGTGACCAACAAAGTGAATAGCATCATCGACAAGATGAACACCCAG TTCGAGGCCGTGGGCAGAGAGTTCAACAACCTGGAAAGACGGATCGAGAACCTGAACAAGAAGATGGA GGACGGCTTCCTGGACGTGTGGACCTATAATGCCGAGCTGCTGGTCCTGATGGAAAACGAGAGAACCC TGGACTTCCACGACAGCAACGTGAAGAACCTGTACGACAAAGTGCGGCTCCAGCTGCGGGACAATGCC AAAGAACTCGGCAACGGCTGCTTCGAGTTCTACCACAAGTGCGACAACGAGTGCATGGAAAGCGTGCG GAACGGCACCTACGACTACCCTCAGTACTCTGAGGAAGCCCGGCTGAAGAGAGAAGAGATCAGCGGAG TGAAGCTGGAATCCATCGGCACATACCAGATCCTGAGCATCTACAGCACCGTGGCCTCTTCTCTGGCC CTGGCTATTATGGTGGCTGGCCTGAGCCTGTGGATGTGCTCTAATGGCAGCCTCCAGTGCCGGATCTG CATCGGATCTGGCGAAGGCAGAGGCAGCCTGCTGACATGCGGAGATGTGGAAGAGAATCCCGGACCTA TGAATCCCAACCAGAAGATCATCACCATCGGCAGCATCTGCATGGTCGTGGGCATCATCAGCCTGATC CTCCAGATCGGCAACATCATCTCCATCTGGGTGTCCCACAGCATCCAGACCGGCAATCAGAACCAGCC TGAGACATGCAACCAGTCCATCATCACCTACGAGAACAACACCTGGGTCAACCAGACCTACGTGAACA TCAGCAACACCAACTTCGTGGCCGAACAGGCCGTGGCTTCTGTTGCCCTGGCCGGAAATAGCTCTCTG TGCCCTATTAGCGGCTGGGCCATCTACAGCAAGGACAACGGCATCCGGATCGGCTCTAAGGGCGACGT GTTCGTGATCAGAGAGCCCTTCATCAGCTGCTCCCACCTGGAATGCCGGACATTCTTTCTGACCCAAG GCGCCCTGCTGAACGACAAGCACAGCAATGGCACCGTGAAGGACAGAAGCCCCTACAGAACCCTGATG AGCTGCCCTGTGGGAGAAGCCCCATCTCCTTACAACAGCAGATTCGAGTCCGTGGCTTGGAGCGCCTC TGCCTGTCACGATGGAATCAGCTGGCTGACAATCGGCATCAGCGGCCCTGATAATGGCGCTGTGGCCG TGCTGAAGTACAACGGAATCATCACCGACACCATCAAGAGCTGGCGGAACAACATCCTGCGGACCCAA GAGTCCGAGTGCGCCTGTATCAATGGCAGCTGCTTCACCATCATGACAGACGGCCCTAGCAATGGCCA GGCCAGCTACAAGATTTTCAAGATCGAGAAGGGCAAAGTGGTCAAGAGCGTGGAACTGAACGCCCCTA ACTACCACTACGAGGAATGCAGCTGCTACCCCGATGCCGGCGAAGTGATGTGCGTGTGCAGAGACAAT TGGCACGGCAGCAACAGACCTTGGGTGTCCTTCAACCAGAACCTGGAATATCAGATCGGCTATATCTG CTCCGGCGTGTTCGGCGACAACCCCAGACCTAATGATGGCACAGGCAGCTGTGGCCCCGTGTCATCTA ATGGCGCCTATGGCGTGAAGGGCTTCAGCTTTAAGTACGGCAAAGGCGTGTGGATCGGCCGGACCAAG AGCACCTCTAGCAGATCCGGCTTCGAGATGATCTGGGACCCCAACGGCTGGACCGAGACAGATAGCAG CTTCAGCGTGAAGCAGGACATCGTGGCCATCACCGATTGGAGCGGCTACAGCGGAAGCTTCGTGCAGC ACCCTGAACTGACAGGCCTGGACTGCATGAGGCCCTGCTTTTGGGTCGAGCTGATCCGGGGCAGACCC AAAGAGAACACCATCTGGACAAGCGGCAGCAGCATCAGCTTTTGCGGCGTGAACAGCGATACCGTCGG CTGGTCTTGGCCTGATGGTGCCGAGCTGCCTTTCACCATCGACAAAGGATCCGGCGCCACCAACTTTA GTCTGCTGAAACAGGCCGGCGACGTCGAAGAGAACCCAGGTCCTATGTCTCTGCTGACCGAGGTGGAA ACCCCTACCAGAAATGGCTGGGAGTGCAGATGCAGCGACAGCAGCGATCCTCTGGTTATCGCCGCCAG CATCATCGGCATCCTGCACCTGATCCTGTGGATCCTGGACCGGCTGTTCTTCAAGTGCATCTACCGGC GGCTGAAGTACGGCCTGAAGAGAGGCCCTTCTACAGAGGGCGTGCCCGAGAGCATGCGGGAAGAGTAC AGACAGAAACAGCAGAGCGCCGTGGACGTGGACGATGGCCACTTCGTGAACATCGAGCTGGAATGA >S3_T2_12 (SEQ ID NO:10) Nucleic acid sequence: ATGGAAAAGATCGTGCTGCTGCTGGCCATCGTGTCCCTGGTCAAGAGCGACCAAATCTGCATCGGCTA CCACGCCAACAACAGCACCGAACAGGTGGACACCATTATGGAAAAGAACGTCACCGTGACACACGCCC AGGACATCCTGGAAAAGACCCACAACGGCAAGCTGTGCGACCTGAACGGCGTGAAGCCTCTGATCCTG AAGGATTGCTCTGTGGCCGGATGGCTGCTGGGCAATCCCATGTGCGACGAGTTCATCAGAGTGCCCGA GTGGTCCTACATCGTGGAAAGAGCCAATCCTGCCAACGACCTGTGCTTCCCCGGCAACCTGAACGACT ACGAGGAACTGAAGCACCTCCTGAGCCGGATCAACCACTTCGAGAAGATCCTGATCATCCCCAAGAGC AGCTGGCCCAACCACGAGACATCTCTGGGAGTGTCTGCCGCATGTCCATACCAGGGCACCCCTAGCTT TTTCCGGAACGTCGTGTGGCTGATCAAGAAGAACGACGCTTACCCCACCATCAAGATCAGCTACAACA ACACCAACCGCGAGGACCTGCTGATCCTGTGGGGAATCCACCACAGCAACAATGCCGCCGAGCAGACC AACCTGTACAAGAACCCCACCACCTACATCAGCGTGGGCACCAGCACACTGAACCAGAGACTGGTGCC TAAGATCGCCACACGGTCCCAAGTGAATGGCGAGAGGGGCAGAATGGACTTCTTCTGGACCATCCTGA AGCCTAACGACGCCATCCACTTTGAGAGCAACGGCAACTTTATCGCCCCTGAGTACGCCTACAAGATC GTGAAGAAGGGCGACAGCACCATCATGAAGTCCGAGGTGGAATACGGCCACTGCAACACCAAGTGTCA GACCCCTATCGGCGCCATCAACTCCAGCATGCCCTTCCACAACATTCACCCTCTGACCATCGGCGAGT GCCCCAAATACGTGAAGTCCAACAAGCTGGTGCTGGCTACCGGCCTGAGAAACAGCCCTCTGAGAGAG AAGCGCAGACGGAAGAAGAGAGGCCTGTTTGGCGCCATTGCCGGCTTTATCGAAGGCGGCTGGCAAGG CATGGTGGACGGATGGTACGGCTACCATCACAGCAACGAGCAAGGCTCTGGATACGCCGCCGACAAAG AGAGCACCCAGAAAGCCATTGACGGCGTGACCAACAAAGTGAACAGCATCATCGACAAGATGAACACC CAGTTCGAGGCCGTGGGCAGAGAGTTCAACAACCTGGAACGGCGGATCGAGAATCTGAACAAGAAGAT GGAGGACGGCTTCCTGGACGTGTGGACCTACAATGCCGAGCTGCTGGTCCTGATGGAAAACGAGAGAA CCCTGGACTTCCACGACTCCAACGTGAAGAACCTGTACGACAAAGTGCGGCTCCAGCTGCGGGACAAC GCCAAAGAACTCGGCAACGGCTGCTTCGAGTTCTACCACAAGTGCGACAACGAGTGCATGGAAAGCGT GCGGAACGGCACCTACGACTACCCTCAGTACAGCGAGGAAGCCCGGCTGAAGAGAGAAGAGATCAGCG GAGTGAAGCTGGAATCCATCGGCACATACCAGATCCTGTCCATCTACAGCACCGTGGCCTCTTCTCTG GCCCTGGCCATTATGGTGGCTGGCCTGTCTCTGTGGATGTGCAGCAATGGCAGCCTCCAGTGCCGGAT CTGCATCGGATCTGGCGAAGGCAGAGGCAGCCTGCTGACATGCGGAGATGTGGAAGAGAATCCCGGAC CTATGAATCCCAACCAGAAGATCATCACCATCGGCAGCATCTGCATGGTCGTGGGCATCATCAGCCTG ATCCTCCAGATCGGCAACATCATCTCCATCTGGGTGTCCCACAGCATCCAGACCGGCAATCAGAACCA GCCTGAGACATGCAACCAGTCCATCATCACCTACGAGAACAACACCTGGGTCAACCAGACCTACGTGA ACATCAGCAACACCAACTTCGTGGCCGAACAGGCCGTGGCTTCTGTTGCCCTGGCCGGAAATAGCTCT CTGTGCCCTATTAGCGGCTGGGCCATCTACAGCAAGGACAACGGCATCCGGATCGGCTCTAAGGGCGA CGTGTTCGTGATCAGAGAGCCCTTCATCAGCTGCTCCCACCTGGAATGCCGGACATTCTTTCTGACCC AAGGCGCCCTGCTGAACGACAAGCACAGCAATGGCACCGTGAAGGACAGAAGCCCCTACAGAACCCTG ATGAGCTGCCCTGTGGGAGAAGCCCCATCTCCTTACAACAGCAGATTCGAGTCCGTGGCTTGGAGCGC CTCTGCCTGTCACGATGGAATCAGCTGGCTGACAATCGGCATCAGCGGCCCTGATAATGGCGCTGTGG CCGTGCTGAAGTACAACGGAATCATCACCGACACCATCAAGAGCTGGCGGAACAACATCCTGCGGACC CAAGAGTCCGAGTGCGCCTGTATCAATGGCAGCTGCTTCACCATCATGACAGACGGCCCTAGCAATGG CCAGGCCAGCTACAAGATTTTCAAGATCGAGAAGGGCAAAGTGGTCAAGAGCGTGGAACTGAACGCCC CTAACTACCACTACGAGGAATGCAGCTGCTACCCCGATGCCGGCGAAGTGATGTGCGTGTGCAGAGAC AATTGGCACGGCAGCAACAGACCTTGGGTGTCCTTCAACCAGAACCTGGAATATCAGATCGGCTATAT CTGCTCCGGCGTGTTCGGCGACAACCCCAGACCTAATGATGGCACAGGCAGCTGTGGCCCCGTGTCAT CTAATGGCGCCTATGGCGTGAAGGGCTTCAGCTTTAAGTACGGCAAAGGCGTGTGGATCGGCCGGACC AAGAGCACCTCTAGCAGATCCGGCTTCGAGATGATCTGGGACCCCAACGGCTGGACCGAGACAGATAG CAGCTTCAGCGTGAAGCAGGACATCGTGGCCATCACCGATTGGAGCGGCTACAGCGGAAGCTTCGTGC AGCACCCTGAACTGACAGGCCTGGACTGCATGAGGCCCTGCTTTTGGGTCGAGCTGATCCGGGGCAGA CCCAAAGAGAACACCATCTGGACAAGCGGCAGCAGCATCAGCTTTTGCGGCGTGAACAGCGATACCGT CGGCTGGTCTTGGCCTGATGGTGCCGAGCTGCCTTTCACCATCGACAAAGGATCCGGCGCCACCAACT TTAGTCTGCTGAAACAGGCCGGCGACGTCGAAGAGAACCCAGGTCCTATGTCTCTGCTGACCGAGGTG GAAACCCCTACCAGAAATGGCTGGGAGTGCAGATGCAGCGACAGCAGCGATCCTCTGGTTATCGCCGC CAGCATCATCGGCATCCTGCACCTGATCCTGTGGATCCTGGACCGGCTGTTCTTCAAGTGCATCTACC GGCGGCTGAAGTACGGCCTGAAGAGAGGCCCTTCTACAGAGGGCGTGCCCGAGAGCATGCGGGAAGAG TACAGACAGAAACAGCAGAGCGCCGTGGACGTGGACGATGGCCACTTCGTGAACATCGAGCTGGAATG A >Consensus Kozak sequence (SEQ ID NO:11) ACCAUG (initiation codon underlined) >Elongated Kozak sequence (SEQ ID NO:12) GCCACCAUG (initiation codon underlined) >2A self-cleaving peptide sequence (SEQ ID NO:13) GSGEGRGSLLTCGDVEENPGP >2A self-cleaving peptide sequence (SEQ ID NO:14) GSGATNFSLLKQAGDVEENPGP >Additional S3_T2_3 sequence (SEQ ID NO:15) Nucleic acid sequence: ATGGAAAAGATTGTGCTGCTGCTGGCCATCGTGTCCCTGGTCAAGAGCGATCAAATCTGCATCGGCTA CCACGCCAACAACAGCACCGAACAGGTGGACACCATTATGGAAAAGAACGTGACCGTGACACACGCCC AGGACATCCTGGAAAAGACCCACAACGGCAAGCTGTGCGACCTGGATGGCGTGAAGCCTCTGATCCTG AGAGATTGCTCTGTGGCCGGCTGGCTGCTGGGCAATCCTATGTGCGACGAGTTCATCAACGTGCCCGA GTGGTCCTATATCGTGGAAAAGGCCAATCCTGCCAACGACCTGTGCTACCCCGGCAACTTCAACGACT ACGAGGAACTGAAACATCTGCTGAGCCGGATCAACCACTTCGAGAAGATCCAGATCATCCCCAAGTCC TCTTGGAGCGATCACGAGGCCTCTAGCGGAGTGTCTAGCGCCTGTCCTTACCAAGGCAGAAGCAGCTT CTTCCGGAACGTCGTGTGGCTGATCAAGAAGAACAACGCTTACCCCACCATCAAGCGGAGCTACAACA ACACCAATCAAGAGGACCTGCTGGTGCTGTGGGGCATCCACCATCCTAATGATGCCGCCGAGCAGACC CGGCTGTACCAGAATCCTACAACCTACATCAGCGTGGGCACCAGCACACTGAACCAGAGACTGGTGCC TAAGATCGCCACCAGATCCAAAGTGAACGGCCAGAGCGGCCGGATGGAATTCTTCTGGACCATCCTGA AGCCTAACGACGCCATCAACTTCGAGAGCAACGGCAACTTTATCGCCCCTGAGTACGCCTACAAGATC GTGAAGAAGGGCGACAGCGCCATCATGAAGTCCGAGCTGGAATACGGCAACTGCAACACCAAGTGTCA GACCCCTATGGGCGCCATCAATAGCAGCATGCCCTTCCACAACATTCACCCTCTGACCATCGGCGAGT GCCCCAAATACGTGAAGTCCAACAGACTGGTCCTGGCCACCGGCCTGAGAAATTCTCCACAGAGAGAG CGGCGCAGAAAGAAGAGAGGCCTGTTTGGAGCCATTGCCGGCTTTATCGAAGGCGGCTGGCAAGGCAT GGTTGACGGATGGTACGGCTATCACCACAGCAATGAGCAAGGCTCTGGCTACGCCGCCGACAAAGAGA GCACACAGAAAGCCATCGACGGCGTGACCAACAAAGTGAATAGCATCATCGACAAGATGAACACCCAG TTCGAGGCCGTGGGCAGAGAGTTCAACAACCTGGAAAGACGGATCGAGAACCTGAACAAGAAGATGGA GGACGGCTTCCTGGACGTGTGGACCTATAATGCCGAGCTGCTGGTCCTGATGGAAAACGAGAGAACCC TGGACTTCCACGACAGCAACGTGAAGAACCTGTACGACAAAGTGCGGCTCCAGCTGCGGGACAATGCC AAAGAACTCGGCAACGGCTGCTTCGAGTTCTACCACAAGTGCGACAACGAGTGCATGGAAAGCGTGCG GAACGGCACCTACGACTACCCTCAGTACTCTGAGGAAGCCCGGCTGAAGAGAGAAGAGATCAGCGGAG TGAAGCTGGAATCCATCGGCACATACCAGATCCTGAGCATCTACAGCACCGTGGCCTCTTCTCTGGCC CTGGCTATTATGGTGGCTGGCCTGAGCCTGTGGATGTGCTCTAATGGCAGCCTCCAGTGCCGGATCTG CATCGGATCTGGCGAAGGCAGAGGCAGCCTGCTGACATGCGGAGATGTGGAAGAGAATCCCGGACCTA TGAATCCCAACCAGAAGATCATCACCATCGGCAGCATCTGCATGGTCGTGGGCATCATCAGCCTGATC CTCCAGATCGGCAACATCATCTCCATCTGGGTGTCCCACAGCATCCAGACCGGCAATCAGAACCAGCC TGAGACATGCAACCAGTCCATCATCACCTACGAGAACAACACCTGGGTCAACCAGACCTACGTGAACA TCAGCAACACCAACTTCGTGGCCGAACAGGCCGTGGCTTCTGTTGCCCTGGCCGGAAATAGCTCTCTG TGCCCTATTAGCGGCTGGGCCATCTACAGCAAGGACAACGGCATCCGGATCGGCTCTAAGGGCGACGT GTTCGTGATCAGAGAGCCCTTCATCAGCTGCTCCCACCTGGAATGCCGGACATTCTTTCTGACCCAAG GCGCCCTGCTGAACGACAAGCACAGCAATGGCACCGTGAAGGACAGAAGCCCCTACAGAACCCTGATG AGCTGCCCTGTGGGAGAAGCCCCATCTCCTTACAACAGCAGATTCGAGTCCGTGGCTTGGAGCGCCTC TGCCTGTCACGATGGAATCAGCTGGCTGACAATCGGCATCAGCGGCCCTGATAATGGCGCTGTGGCCG TGCTGAAGTACAACGGAATCATCACCGACACCATCAAGAGCTGGCGGAACAACATCCTGCGGACCCAA GAGTCCGAGTGCGCCTGTATCAATGGCAGCTGCTTCACCATCATGACAGACGGCCCTAGCAATGGCCA GGCCAGCTACAAGATTTTCAAGATCGAGAAGGGCAAAGTGGTCAAGAGCGTGGAACTGAACGCCCCTA ACTACCACTACGAGGAATGCAGCTGCTACCCCGATGCCGGCGAAGTGATGTGCGTGTGCAGAGACAAT TGGCACGGCAGCAACAGACCTTGGGTGTCCTTCAACCAGAACCTGGAATATCAGATCGGCTATATCTG CTCCGGCGTGTTCGGCGACAACCCCAGACCTAATGATGGCACAGGCAGCTGTGGCCCCGTGTCATCTA ATGGCGCCTATGGCGTGAAGGGCTTCAGCTTTAAGTACGGCAAAGGCGTGTGGATCGGCCGGACCAAG AGCACCTCTAGCAGATCCGGCTTCGAGATGATCTGGGACCCCAACGGCTGGACCGAGACAGATAGCAG CTTCAGCGTGAAGCAGGACATCGTGGCCATCACCGATTGGAGCGGCTACAGCGGAAGCTTCGTGCAGC ACCCTGAACTGACAGGCCTGGACTGCATGAGGCCCTGCTTTTGGGTCGAGCTGATCCGGGGCAGACCC AAAGAGAACACCATCTGGACAAGCGGCAGCAGCATCAGCTTTTGCGGCGTGAACAGCGATACCGTCGG CTGGTCTTGGCCTGATGGTGCCGAGCTGCCTTTCACCATCGACAAAGGATCCGGCGCCACCAACTTTA GTCTGCTGAAACAGGCCGGCGACGTCGAAGAGAACCCAGGTCCTATGTCTCTGCTGACCGAGGTGGAA ACCCCTACCAGAAATGGCTGGGAGTGCAGATGCAGCGACAGCAGCGATCCTCTGGTTATCGCCGCCAG CATCATCGGCATCCTGCACCTGATCCTGTGGATCCTGGACCGGCTGTTCTTCAAGTGCATCTACCGGC GGCTGAAGTACGGCCTGAAGAGAGGCCCTTCTACAGAGGGCGTGCCCGAGAGCATGCGGGAAGAGTAC AGACAGAAACAGCAGAGCGCCGTGGACGTGGACGATGGCCACTTCGTGAACATCGAGCTGGAA >Additional S3_T2_12 sequence (SEQ ID NO:16) Nucleic acid sequence: ATGGAAAAGATCGTGCTGCTGCTGGCCATCGTGTCCCTGGTCAAGAGCGACCAAATCTGCATCGGCTA CCACGCCAACAACAGCACCGAACAGGTGGACACCATTATGGAAAAGAACGTCACCGTGACACACGCCC AGGACATCCTGGAAAAGACCCACAACGGCAAGCTGTGCGACCTGAACGGCGTGAAGCCTCTGATCCTG AAGGATTGCTCTGTGGCCGGATGGCTGCTGGGCAATCCCATGTGCGACGAGTTCATCAGAGTGCCCGA GTGGTCCTACATCGTGGAAAGAGCCAATCCTGCCAACGACCTGTGCTTCCCCGGCAACCTGAACGACT ACGAGGAACTGAAGCACCTCCTGAGCCGGATCAACCACTTCGAGAAGATCCTGATCATCCCCAAGAGC AGCTGGCCCAACCACGAGACATCTCTGGGAGTGTCTGCCGCATGTCCATACCAGGGCACCCCTAGCTT TTTCCGGAACGTCGTGTGGCTGATCAAGAAGAACGACGCTTACCCCACCATCAAGATCAGCTACAACA ACACCAACCGCGAGGACCTGCTGATCCTGTGGGGAATCCACCACAGCAACAATGCCGCCGAGCAGACC AACCTGTACAAGAACCCCACCACCTACATCAGCGTGGGCACCAGCACACTGAACCAGAGACTGGTGCC TAAGATCGCCACACGGTCCCAAGTGAATGGCGAGAGGGGCAGAATGGACTTCTTCTGGACCATCCTGA AGCCTAACGACGCCATCCACTTTGAGAGCAACGGCAACTTTATCGCCCCTGAGTACGCCTACAAGATC GTGAAGAAGGGCGACAGCACCATCATGAAGTCCGAGGTGGAATACGGCCACTGCAACACCAAGTGTCA GACCCCTATCGGCGCCATCAACTCCAGCATGCCCTTCCACAACATTCACCCTCTGACCATCGGCGAGT GCCCCAAATACGTGAAGTCCAACAAGCTGGTGCTGGCTACCGGCCTGAGAAACAGCCCTCTGAGAGAG AAGCGCAGACGGAAGAAGAGAGGCCTGTTTGGCGCCATTGCCGGCTTTATCGAAGGCGGCTGGCAAGG CATGGTGGACGGATGGTACGGCTACCATCACAGCAACGAGCAAGGCTCTGGATACGCCGCCGACAAAG AGAGCACCCAGAAAGCCATTGACGGCGTGACCAACAAAGTGAACAGCATCATCGACAAGATGAACACC CAGTTCGAGGCCGTGGGCAGAGAGTTCAACAACCTGGAACGGCGGATCGAGAATCTGAACAAGAAGAT GGAGGACGGCTTCCTGGACGTGTGGACCTACAATGCCGAGCTGCTGGTCCTGATGGAAAACGAGAGAA CCCTGGACTTCCACGACTCCAACGTGAAGAACCTGTACGACAAAGTGCGGCTCCAGCTGCGGGACAAC GCCAAAGAACTCGGCAACGGCTGCTTCGAGTTCTACCACAAGTGCGACAACGAGTGCATGGAAAGCGT GCGGAACGGCACCTACGACTACCCTCAGTACAGCGAGGAAGCCCGGCTGAAGAGAGAAGAGATCAGCG GAGTGAAGCTGGAATCCATCGGCACATACCAGATCCTGTCCATCTACAGCACCGTGGCCTCTTCTCTG GCCCTGGCCATTATGGTGGCTGGCCTGTCTCTGTGGATGTGCAGCAATGGCAGCCTCCAGTGCCGGAT CTGCATCGGATCTGGCGAAGGCAGAGGCAGCCTGCTGACATGCGGAGATGTGGAAGAGAATCCCGGAC CTATGAATCCCAACCAGAAGATCATCACCATCGGCAGCATCTGCATGGTCGTGGGCATCATCAGCCTG ATCCTCCAGATCGGCAACATCATCTCCATCTGGGTGTCCCACAGCATCCAGACCGGCAATCAGAACCA GCCTGAGACATGCAACCAGTCCATCATCACCTACGAGAACAACACCTGGGTCAACCAGACCTACGTGA ACATCAGCAACACCAACTTCGTGGCCGAACAGGCCGTGGCTTCTGTTGCCCTGGCCGGAAATAGCTCT CTGTGCCCTATTAGCGGCTGGGCCATCTACAGCAAGGACAACGGCATCCGGATCGGCTCTAAGGGCGA CGTGTTCGTGATCAGAGAGCCCTTCATCAGCTGCTCCCACCTGGAATGCCGGACATTCTTTCTGACCC AAGGCGCCCTGCTGAACGACAAGCACAGCAATGGCACCGTGAAGGACAGAAGCCCCTACAGAACCCTG ATGAGCTGCCCTGTGGGAGAAGCCCCATCTCCTTACAACAGCAGATTCGAGTCCGTGGCTTGGAGCGC CTCTGCCTGTCACGATGGAATCAGCTGGCTGACAATCGGCATCAGCGGCCCTGATAATGGCGCTGTGG CCGTGCTGAAGTACAACGGAATCATCACCGACACCATCAAGAGCTGGCGGAACAACATCCTGCGGACC CAAGAGTCCGAGTGCGCCTGTATCAATGGCAGCTGCTTCACCATCATGACAGACGGCCCTAGCAATGG CCAGGCCAGCTACAAGATTTTCAAGATCGAGAAGGGCAAAGTGGTCAAGAGCGTGGAACTGAACGCCC CTAACTACCACTACGAGGAATGCAGCTGCTACCCCGATGCCGGCGAAGTGATGTGCGTGTGCAGAGAC AATTGGCACGGCAGCAACAGACCTTGGGTGTCCTTCAACCAGAACCTGGAATATCAGATCGGCTATAT CTGCTCCGGCGTGTTCGGCGACAACCCCAGACCTAATGATGGCACAGGCAGCTGTGGCCCCGTGTCAT CTAATGGCGCCTATGGCGTGAAGGGCTTCAGCTTTAAGTACGGCAAAGGCGTGTGGATCGGCCGGACC AAGAGCACCTCTAGCAGATCCGGCTTCGAGATGATCTGGGACCCCAACGGCTGGACCGAGACAGATAG CAGCTTCAGCGTGAAGCAGGACATCGTGGCCATCACCGATTGGAGCGGCTACAGCGGAAGCTTCGTGC AGCACCCTGAACTGACAGGCCTGGACTGCATGAGGCCCTGCTTTTGGGTCGAGCTGATCCGGGGCAGA CCCAAAGAGAACACCATCTGGACAAGCGGCAGCAGCATCAGCTTTTGCGGCGTGAACAGCGATACCGT CGGCTGGTCTTGGCCTGATGGTGCCGAGCTGCCTTTCACCATCGACAAAGGATCCGGCGCCACCAACT TTAGTCTGCTGAAACAGGCCGGCGACGTCGAAGAGAACCCAGGTCCTATGTCTCTGCTGACCGAGGTG GAAACCCCTACCAGAAATGGCTGGGAGTGCAGATGCAGCGACAGCAGCGATCCTCTGGTTATCGCCGC CAGCATCATCGGCATCCTGCACCTGATCCTGTGGATCCTGGACCGGCTGTTCTTCAAGTGCATCTACC GGCGGCTGAAGTACGGCCTGAAGAGAGGCCCTTCTACAGAGGGCGTGCCCGAGAGCATGCGGGAAGAG TACAGACAGAAACAGCAGAGCGCCGTGGACGTGGACGATGGCCACTTCGTGAACATCGAGCTGGAA

[0003] Example 1 Immunogenicity of combined administration of antigen string constructs comprising different optimised influenza HA sequences Two different DIOS (i.e. optimised) H5 vaccine antigens, provided in a string construct, given at the same time induce broader more potent immune responses against a panel of H5 clades than immune responses when administered individually. This Example uses the specific case of H5N1 (avian) influenza. This Example shows the results of study FLU037, designed to follow up on the data generated in vivo from FLU024 and FLU033. The study uses antigens covering the most promising H5 ancestors targeting different H5 clades, including the 2.3.4.4 clade that is currently showing high risk of human spillover. Figure 1 shows a representation of influenza A H5 phylogenetic tree featuring various clades. The best DIOS H5 vaccine candidates (in DNA) for both human and zoonotic or pre-pandemic use were tested for immunogenicity in chickens, a known avian reservoir of H5 subtype viruses, to strengthen the claim that these DIOS H5 constructs can be made into pre-pandemic vaccines. The H5 antigens are delivered as string constructs comprising neuraminidase (NA) and Matrix-2 (M2) nucleic acid: S3_T2_3 (SEQ ID NO:9) and S3_T2_12 (SEQ ID NO:10). The components of the string constructs are detailed in Table 1 below. Figure 2(i) shows the study schedule of immunisation of DIOS (i.e. optimised) H5 vaccines in chickens. Chickens from Groups 1-3 (Table 1 below) were administered with 100 µg DNA of the indicated H5N1 string designed construct on days 0 and 14. Bleeds were taken pre- immunisation and on day 28. Table 1. Study plan for immunisation of DIOS (i.e. optimised) H5 vaccines (DNA) in chickens. Chickens from Groups 1-2 were administered with 100 µg of the indicated DNA construct on days 0 and 14. For Group 3, chickens were vaccinated with 50 µg of each construct. Results Figure 2(ii) shows immunogenicity of the DIOS (optimised) H5 constructs in chickens (n=10) after 2 vaccinations (day 28). The neutralisation of various H5 pseudotypes (PV): A / chicken / Mexico / 07 / 2007 (H5) AM non-GS-GD, A / mallard / Netherlands / 41 / 2015 (H5) EU non-GS-GD, A / chicken / Vietnam / NCVD-016 / 2008 (H5) clade 7.1, A / Vietnam / 1203 / 2004 (H5) clade 1, A / Indonesia / 5 / 2005 (H5) clade 2.1.3.2, A / whooper swan / Mongolia / 244 / 2005 (H5) clade 2.2, A / turkey / Turkey / 1 / 2005 (H5) clade 2.2.1, A / Egypt / 3300-NAMRU3 / 2008 (H5) clade 2.2.1.1, A / Hubei / 1 / 2010 (H5) clade 2.3.2.1a, A / Anhui / 1 / 2005 (H5) clade 2.3.4, A / Sichuan / 26221 / 2014 (H5) clade 2.3.4.4a, A / mute swan / England / 050354 / 2021 (H5) clade 2.3.4.4b avian, A / Hangzhou / 1 / 2021 (H5) clade 2.3.4.4b human, A / gyrfalcon / Washington / 41088-6 / 2014 (H5) clade 2.3.4.4c, and A / Anhui / 2021-00011 / 2020 (H5) clade 2.3.4.4h was demonstrated by antisera generated from immunisations as indicated in Table 1 above. Figure 2(ii) shows that immunisation with either S3_T2_3 construct (A) or with S3_T2_12 construct (B) show low to moderate neutralising antibody titres against the H5 PV tested. Immunisation with a combination of S3_T2_3 and S3_T2_12 constructs (C) boosts the neutralising antibody titres against the entire panel of H5 PV tested, improving the response against all clades including the more divergent clade 2.3.4.4h. Figure 3 shows a heatmap illustrating number of chickens (n=10) that elicited an immune response above the threshold values against representative H5 PVs from various clades, when vaccinated with S3_T2_3, S3_T2_12, or with S3_T2_3 in combination with S3_T2_12. Figure 4 shows H5 clade 2.3.4.4. phylogenetic tree representation. Figure 5 shows that immunisation with S3_T2_3 and S3_T2_12 string constructs (DIOS optimised H5 constructs containing an N1 component) elicited antibodies which show neuraminidase inhibition activity in chickens (n=10) after 2 vaccinations (day 28). The inhibition of various N1 PVs from different species: A / mute swan / England / 053054 / 2021 (N1) (mute swan N1), A / harbor seal / Maine / 2022 (N1) (harbor seal N1), and A / mink / China / CY / 2017 (N1) (mink N1), was demonstrated by antisera generated from immunisations as indicated in Table 1. Figure 5 is a heatmap showing number of chickens (n=10) that elicited an immune response above the threshold values against representative N1 PV from different species. Figure 5 shows that immunisation with S3_T2_3 construct (A) or with S3_T2_12 construct (B) show low to moderate neutralising antibody titres against the N1 PVs tested, with around 5-6 chickens not showing any anti-NA activity (Figure 6). Immunisation with the combination of S3_T2_3 and S3_T2_12 (C) boosts the NA inhibition titres against the entire panel of N1 PV, improving the response against N1 from all species tested. These data sets demonstrate that S3_T2_3 and S3_T2_12, when given in combination, produce higher and broader anti-H5 neutralising titres covering different clades, and anti-NA inhibition titres against N1 from different species, than when given separately. This Example, together with Example 2 below, suggests that immunisation with any different optimised HA combination results in a synergistic immune response compared with immunisation with the same HA antigens separately (in separate subjects). This Example uses the specific case of H5N1 (avian) influenza. Example 2 Synergistic immunological effect of combined administration of antigen string constructs comprising different optimised influenza HA sequences The Bliss independence model is widely used to analyse drug combination data when screening for candidate drug combinations. The method compares the observed combination response (YO) with the expected combination response (YP). The combination effect is declared synergistic if YO is greater than YP. The limitation of this approach is that it does not take into account the variability of the response measures. It is also often applied when the two drugs are believed to be targeting to different pathways. In Table 2, we have taken the ten IC50 Dilution values from FLU037 Bleed 2 for chickens vaccinated with S3_T2_3, S3_T2_12, and combined S3_T2_3 + S3_T2_12. The data was normalised by adjusting for a maximum value of 6000 (maximum dilution employed in the assay) and the median value was calculated. The predicted combined effect of the independent string experiment was calculated with the following equation where a is the single S3_T2_3 experiment and b is the single S3_T2_12 experiment: expected_combined_effect (YP) < median_a + median_b - (median_a * median_b) The expected combined effect is then compared to the observed combination response (the median of the mixed S3_T2_3 + S3_T2_12 experiment), and if the observed combination response is greater, a synergistic effect is indicated. Adjusted Median Adjus Median Expected H5 cladeMedianMedian S3_T2_3 ted Adjusted Median Media S3_T2_3 Combined S3_T2_3S3_T2_12 + n S3_T2_3 + Effect S3_T2_12 S3_T2_12 S3_T2_12 (YP) (YO) AM- 196.500 133.000 523.700 0.033 0.022 0.087 0.054 nonGsGD EU- 387.400 198.500 1692.000 0.065 0.033 0.282 0.096 nonGsGD 7.1 384.300 165.100 3429.000 0.064 0.028 0.572 0.090 1 222.000 136.500 4015.000 0.037 0.023 0.669 0.059 2.1.3.2 246.500 70.500 1322.000 0.041 0.012 0.220 0.052 2.2 841.300 1.000 1751.500 0.140 0.000 0.292 0.140 2.2.1 551.550 62.985 2520.000 0.092 0.010 0.420 0.102 2.2.1.1 204.800 68.865 447.900 0.034 0.011 0.075 0.045 2.3.2.1a 151.600 28.080 957.850 0.025 0.005 0.160 0.030 2.3.4 217.900 71.240 1381.000 0.036 0.012 0.230 0.048 2.3.4.4a 23.500 502.500 1743.500 0.004 0.084 0.291 0.087 2.3.4.4b 25.000 548.500 2860.500 0.004 0.091 0.477 0.095 avian 2.3.4.4b 112.500 570.000 2761.500 0.019 0.095 0.460 0.112 human 2.3.4.4c 215.500 700.500 3454.000 0.036 0.117 0.591 0.148 2.3.4.4h 69.000 142.500 975.000 0.012 0.024 0.163 0.035 Table 2. Raw and adjusted values for determining synergistic effect via the Bliss Independence Model for FLU037. YO indicating synergy is highlighted in grey (YO > YP). The data from FLU037 (Table 2) indicate that S3_T2_3 and S3_T2_12 are working in synergy against all the H5 PV tested. Example 3 Immunogenicity of combined administration of different optimised influenza HA sequences Two different DIOS (i.e. optimised) H5 vaccine antigens given at the same time induce broader more potent immune responses against a panel of H5 clades than immune responses when administered individually. This Example uses the specific case of H5N1 (avian) influenza. This Example shows the results of study FLU030, a study similar to FLU037 involving the most promising H5 ancestors targeting different H5 clades. However, the antigens here are presented in individual formats only covering the hemagglutunin (HA) component with no neuraminidase (NA) and M2 component as that found in the string. All antigens are delivered as DNA constructs. Figure 7 shows the study schedule of immunisation of DIOS H5 vaccines in mice. Mice from Groups 1-3 (Table 3 below) were administered with 50 µg DNA of the indicated construct on days 0, 28, and 56. Bleeds were taken pre-immunisation, on day 26, 54, and terminally at day Table 3. Study plan of immunisation of DIOS H5 vaccines (DNA) in mice. Mice from Groups 1-2 were administered with 50 µg of the indicated DNA construct on days 0, 28, and 56. Mice from Group 3 were given 25 µg of each individual antigen. Results Figure 8 shows immunogenicity of the DIOS (optimised) H5 constructs in mice (n=6) from terminal bleeds taken after 3 vaccinations (day 84). The neutralisation of various H5 pseudotypes (PV): A / Vietnam / 1203 / 2004 (H5) clade 1, A / Indonesia / 5 / 2005 (H5) clade 2.1.3.2, A / whooper swan / Mongolia / 244 / 2005 (H5) clade 2.2, A / turkey / Turkey / 1 / 2005 (H5) clade 2.2.1, A / Egypt / 3300-NAMRU3 / 2008 (H5) clade 2.2.1.1, A / Hubei / 1 / 2010 (H5) clade 2.3.2.1a, A / Anhui / 1 / 2005 (H5) clade 2.3.4, A / Sichuan / 26221 / 2014 (H5) clade 2.3.4.4a, A / mute swan / England / 050354 / 2021 (H5) clade 2.3.4.4b avian, A / Hangzhou / 1 / 2021 (H5) clade 2.3.4.4b human, A / gyrfalcon / Washington / 41088-6 / 2014 (H5) clade 2.3.4.4c, A / Anhui / 2021- 00011 / 2020 (H5) clade 2.3.4.4h, A / chicken / Vietnam / NCVD-016 / 2008 (H5) clade 7.1, A / chicken / Mexico / 07 / 2007 (H5) AM non-GS-GD, and A / mallard / Netherlands / 41 / 2015 (H5) EU non-GS-GD was demonstrated by antisera generated from immunisations as indicated in Table 3 above. Figure 8 shows that immunisation with T2_HA_9 construct (A) or T4_HA_2 construct (B) show low neutralising antibody titres against the H5 PV tested. T4_HA_2 has done better against H5 PV from the 2.3.4.4 clade but is poor against PV from all other clades. However, immunisation with the combination of T2_HA_9 and T4_HA_2 (C) boosts the neutralising antibody titres against the entire panel of H5 PV tested except for the AM non-GS-GD clade, improving the neutralising activity shown by the single antigens. Mice vaccinated with PBS did not show any neutralisation against all virus tested (data not shown). Figure 9 shows a heatmap illustrating number of mice (n=6) that elicited an immune response above the threshold values against representative H5 PV from various clades when immunised with T2_HA_9, T4_HA_2, or combination of T2_HA_9 and T4_HA_2, compared with immunisation with carrier. Heatmap legend number of mice: Black=6, White=0. Example 4 Synergistic immunological effect of combined administration of different optimised influenza HA sequences Similarly, in Table 4, we have taken the six IC50Dilution values from FLU030 Terminal Bleed for mice vaccinated with T2_HA_9, T4_HA_2, and combined T2_HA_9 + T4_HA_2. The data was normalised by adjusting for a maximum value of 5000 (maximum dilution employed in the assay) and the median value was calculated. The predicted combined effect of the independent string experiment was calculated with the following equation where a is the single T2_HA_9 experiment and b is the single T4_HA_2 experiment. expected_combined_effect (YP) < median_a + median_b - (median_a * median_b) The expected combined effect is then compared to the observed combination response (the median of the mixed T2_HA_9 + T4_HA_2 experiment), and if the observed combination response is greater, a synergistic effect is indicated. Adjusted Median Expected Adjusted Adjusted Median Median Median T2_HA_9 Combined H5 clade Median Median T2_HA_9 + T2_HA_9 T4_HA_2 + Effect T2_HA_9 T4_HA_2 T4_HA_2 T4_HA_2 (YP) (YO) 1 21 1 177 0.0041 0.0002 0.0354 0.0043 2.1.3.2 79 1 30 0.0157 0.0002 0.0059 0.0159 2.2 288 1 872 0.0576 0.0002 0.1744 0.0578 2.2.1 408 1 1811 0.0816 0.0002 0.3622 0.0818 2.2.1.1 20 1 102 0.0040 0.0002 0.0204 0.0042 2.3.2.1a 1 1 32 0.0002 0.0002 0.0064 0.0004 2.3.4 1 1 1 0.0002 0.0002 0.0002 0.0004 2.3.4.4a 1 284 407 0.0002 0.0567 0.0813 0.0569 2.3.4.4b 1 512 661 0.0002 0.1024 0.1321 0.1026 avian 2.3.4.4b 1 278 396 0.0002 0.0556 0.0791 0.0558 human 2.3.4.4c 1 473 574 0.0002 0.0946 0.1147 0.0948 2.3.4.4h 21 40 85 0.0042 0.0079 0.0169 0.0121 7.1 1 1 1 0.0002 0.0002 0.0002 0.0004 AM non- 1 1 1 0.0002 0.0002 0.0002 0.0004 GS-GD EU non- 200 1 1005 0.0400 0.0002 0.2010 0.0402 GS-GD Table 4. Raw and adjusted values for determining synergistic effect via the Bliss Independence Model for FLU030. YOindicating synergy is highlighted in grey. The data from FLU030 (Table 4) indicate that a synergistic effect is obtained when combining T2_HA_9 and T4_HA_2 against 11 of the H5 PV tested from representative clades. For both FLU037 and FLU030, combination of the best in class DIOS H5 antigens produce higher and broader serum neutralising titres than when given individually against most of the representative H5 clades tested.

Claims

Claims 1. A pharmaceutical composition which comprises: (a) a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence; and (c) a pharmaceutically acceptable carrier, excipient, or diluent.

2. A combined preparation which comprises: (a) a first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

3. A first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use as a medicament, wherein the first isolated polynucleotide is to be administered before, with, or after administration of the second isolated polynucleotide.

4. A first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polynucleotide is to be administered before, with, or after administration of the second isolated polynucleotide.

5. A first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use as a medicament, wherein the first isolated polynucleotide is to be administered before, with, or after administration of a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

6. A first isolated polynucleotide which comprises nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polynucleotide is to be administered before, with, or after administration of a second isolated polynucleotide which comprises nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

7. A pharmaceutical composition according to claim 1, a combined preparation according to claim 2, a first and a second isolated polynucleotide for use according to claim 3 or 4, or a first isolated polynucleotide for use according to claim 5 or 6, wherein the first and / or second isolated polynucleotide comprises a nucleotide sequence encoding an optimised haemagglutinin H5 amino acid sequence, or the complement thereof.

8. A pharmaceutical composition according to claim 1 or 7, a combined preparation according to claim 2 or 7, a first and a second isolated polynucleotide for use according to claim 3, 4, or 7, or a first isolated polynucleotide for use according to claim 5, 6, or 7, wherein the first isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof.

9. A pharmaceutical composition according to any of claims 1, 7 or 8, a combined preparation according to any of claims 2, 7 or 8, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, or 8, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, or 8, wherein the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof.

10. A pharmaceutical composition according to any of claims 1, 7, 8, or 9, a combined preparation according to any of claims 2, 7, 8, or 9, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, 8, or 9, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 8, or 9, wherein the first isolated polynucleotide comprisesa nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1) and the second isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof.

11. A pharmaceutical composition according to claim 1 or 7, a combined preparation according to claim 2 or 7, a first and a second isolated polynucleotide for use according to claim 3, 4, or 7, or a first isolated polynucleotide for use according to claim 5, 6, or 7, wherein the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof.

12. A pharmaceutical composition according to claim 1, 7, or 11, a combined preparation according to claim 2, 7, or 11, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, or 11, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, or 11, wherein the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1.), or the complement thereof.

13. A pharmaceutical composition according to any of claims 1, 7, 11, or 12, a combined preparation according to any of claims 2, 7, 11, or 12, a first and second isolated polynucleotide for use according to any of claims 3, 4, 7, 11, or 12, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 11, or 12, wherein the first isolated polynucleotide comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3) and the second isolated polynucleotide comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof.

14. A pharmaceutical composition according to any of claims 1, 7, 8, or 10, a combined preparation according to any of claims 2, 7, 8, or 10, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, 8, or 10, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 8, or 10, wherein the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (encoding T2_HA_9 amino acid sequence), or the complement thereof.

15. A pharmaceutical composition according to any of claims 1, 7, 8, 11, or 13, a combined preparation according to any of claims 2, 7, 11, or 13, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, 11, or 13, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 11, or 13, wherein the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (encoding T4_HA_2 amino acid sequence), or the complement thereof.

16. A pharmaceutical composition according to any of claims 1, 7, 12, or 13, a combined preparation according any of claims 2, 7, 12, or 13, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, 12, or 13, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 12, or 13, wherein the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (encoding T2_HA_9 amino acid sequence), or the complement thereof.

17. A pharmaceutical composition according to any of claims 1, 7, 9, or 10, a combined preparation according to any of claims 2, 7, 9, or 10, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, 9, or 10, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 9, or 10, wherein the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (encoding T4_HA_2 amino acid sequence), or the complement thereof.

18. A pharmaceutical composition according to claim 1, 7, 8, 9, or 10, a combined preparation according to claim 2, 7, 8, 9, or 10, a first and a second isolated polynucleotide for use according to claim 3, 4, 7, 8, 9, or 10 or a first isolated polynucleotide for use according to claim 5, 6, 8, 9, or 10, wherein the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (encoding T2_HA_9 amino acid sequence) and the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (encoding T4_HA_2 amino acid sequence), or the complement thereof.

19. A pharmaceutical composition according to any of claims 1, 7, 11, 12, or 13, a combined preparation according to any of claims 2, 7, 11, 12, or 13, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7, 11, 12, or 13, or a first isolated polynucleotide for use according to any of claims 5, 6, 7, 11, 12, or 13, wherein the first isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:4 (encoding T4_HA_2 amino acid sequence) and the second isolated polynucleotide comprises the nucleotide sequence of SEQ ID NO:2 (encoding T2_HA_9 amino acid sequence), or the complement thereof.

20. A vector which comprises a polynucleotide comprising: (a) a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

21. A vector according to claim 20, which further comprises a promoter operably linked to the first and second nucleotide sequences.

22. A vector according to claim 20, which further comprises, a first promoter operably linked to the first nucleotide sequence of the vector, and a separate, second promoter operably linked to the second nucleotide sequence.

23. A pharmaceutical composition which comprises a vector according to any of claims 20 to 22, and a pharmaceutically acceptable carrier, excipient, or diluent.

24. A pharmaceutical composition which comprises: (a) a first vector comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; (b) a second vector comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (c) a pharmaceutically acceptable carrier, excipient, or diluent, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

25. A combined preparation which comprises: (a) a first vector comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof; and (b) a second vector comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

26. A pharmaceutical composition according to claim 24, or a combined preparation according to claim 25, wherein the first vector comprises a first promoter operably linked to the first nucleotide sequence, and the second vector comprises a second promoter operably linked to the second nucleotide sequence.

27. A first vector which comprises a polynucleotide comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second vector which comprises a polynucleotide comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acidsequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use as a medicament, wherein the first vector is to be administered before, with, or after administration of the second vector.

28. A first vector which comprises a polynucleotide comprising a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, and a second vector which comprises a polynucleotide comprising a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded optimised HA amino acid sequence is different to the second encoded optimised HA amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first vector is to be administered before, with, or after administration of the second vector.

29. A first vector which comprises a polynucleotide which comprises a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use as a medicament, wherein the vector is to be administered before, with, or after administration of a second vector which comprises a polynucleotide which comprises a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

30. A first vector which comprises a polynucleotide which comprises a first nucleotide sequence encoding a first optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first vector is to be administered before, with, or after administration of a second vector which comprises a polynucleotide which comprises a second nucleotide sequence encoding a second optimised haemagglutinin (HA) amino acid sequence, or the complement thereof, wherein the first encoded HA amino acid sequence is different to the second encoded HA amino acid sequence.

31. A first vector and a second vector for use according to claim 27 or 28, or a first vector for use according to claim 29 or 30, wherein the first vector further comprises a first promoter operably linked to the first nucleotide sequence, and the second vector further comprises a second promoter operably linked to the second nucleotide sequence.

32. A vector according to any of claims 20 to 22, a pharmaceutical composition according to claim 23 , 24, or 26, a combined preparation according to claim 25 or 26, a first vector and a second vector for use according to any of claims 27, 28, or 31, or a first vector for useaccording to any of claims 29 to 31, wherein the first and / or second nucleotide sequence comprises a nucleotide sequence encoding an optimised haemagglutinin (HA) H5 amino acid sequence, or the complement thereof.

33. A vector according to any of claims 20 to 22, or 32, a pharmaceutical composition according to any of claims 23, 24, 26, or 32, a combined preparation according to claim 25, 26, or 32, a first vector and a second vector for use according to any of claims 27, 28, 31, or 32, or a first vector for use according to any of claims 29 to 32, wherein the first nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof.

34. A vector according to any of claims 20 to 22, 32, or 33, a pharmaceutical composition according to any of claims 23, 24, 26, 32, or 33, a combined preparation according to any of claims 25, 26, 32, or 33, a first vector and a second vector for use according to any of claims 27, 28, 31, 32, or 33, or a first vector for use according to any of claims 29 to 33, wherein the second nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof.

35. A vector according to any of claims 20 to 22, or 32 to 34, a pharmaceutical composition according to any of claims 23, 24, 26, or 32 to 34, a combined preparation according to any of claims 25, 26, or 32 to 34, a first vector and a second vector for use according to any of claims 27, 28, or 31 to 34, or a first vector for use according to any of claims 29 to 34, wherein the first nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1) and the second nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof.

36. A vector according to any of claims 20 to 22, or 32, a pharmaceutical composition according to any of claims 23, 24, 26, or 32, a combined preparation according to claim 25, 26 or 32, a first vector and a second vector for use according to any of claims 27, 28, 31, or 32, or a first vector for use according to any of claims 29 to 32, wherein the first nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), or the complement thereof.

37. A vector according to any of claims 20 to 22, 32, or 36, a pharmaceutical composition according to any of claims 23, 24, 26, 32, or 36, or a combined preparation according to claim 25, 26, 32, or 36, a first vector and a second vector for use according to any of claims 27, 28, 31, 32, or 36, or a first vector for use according to any of claims 29 to 32, or 36, wherein the second nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof.

38. A vector according to any of claims 20 to 22, 32, 36, or 37, a pharmaceutical composition according to any of claims 23, 24, 32, 36, or 37, a combined preparation according to claim 25, 26, 32, 36, or 37, a first vector and a second vector for use according to any of claims 27, 28, 31, 32, 36, or 37, or a first vector for use according to any of claims 29 to 32, 36, or 37, wherein the first nucleotide sequence comprises a nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3), the second nucleotide sequence comprises a nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1), or the complement thereof.

39. A vector, pharmaceutical composition, combined preparation, a first vector and a second vector for use, or a first vector for use, according to any of claims 33 to 35, 37, or 38, wherein the nucleotide sequence encoding T2_HA_9 amino acid sequence (SEQ ID NO:1) comprises the nucleotide sequence of SEQ ID NO:2, or the complement thereof.

40. A vector, pharmaceutical composition, combined preparation, a first vector and a second vector for use, or a first vector for use, according to any of claims 34 to 36, or 38, wherein the nucleotide sequence encoding T4_HA_2 amino acid sequence (SEQ ID NO:3) comprises the nucleotide sequence of SEQ ID NO:4, or the complement thereof.

41. A vector according to any of claims 21, 22, or 32 to 40, a pharmaceutical composition according to any of claims 23, 26, or 32 to 40, a combined preparation according to any of claims 26, or 32 to 40, a first vector and a second vector for use according to any of claims 31 to 40, or a first vector for use according to any of claims 31 to 40, wherein the, or each promoter is for expression of a polypeptide encoded by the polynucleotide in mammalian cells.

42. A vector according to any of claims 21, 22, or 32 to 40, a pharmaceutical composition according to any of claims 23, 26, or 32 to 40, a combined preparation according to any of claims 26, or 32 to 40, a first vector and a second vector for use according to any of claims 31 to 40, or a first vector for use according to any of claims 31 to 40, wherein the, or each promoter is for expression of a polypeptide encoded by the polynucleotide in yeast or insect cells.

43. A vector according to any of claims 20 to 22, or 32 to 42, a pharmaceutical composition according to any of claims 23, 24, 26, or 32 to 42, a combined preparation according to claim 25, 26, or 32 to 42, a first vector and a second vector for use according to any of claims 27, 28, or 31 to 42, or a first vector for use according to any of claims 29 to 42, wherein the, or each vector is a vaccine vector.

44. A vector, pharmaceutical composition, combined preparation, a first vector and a second vector for use, or a first vector for use, according to claim 43, wherein the, or eachvaccine vector is a viral vaccine vector, a bacterial vaccine vector, an RNA vaccine vector, an mRNA vaccine vector, or a DNA vaccine vector.

45. An isolated cell comprising a vector of any of claims 20 to 22, or 32 to 44.

46. A pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, or 32 to 44, a combined preparation according to any of claims 2, 7 to 19, 25, 26, or 32 to 44, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7 to 19, or 32 to 44, a first isolated polynucleotide for use according to any of claims 5 to 19, or 32 to 44, or a vector according to any of claims 20 to 22, or 27 to 44, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, and / or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, further comprises a nucleotide sequence encoding an influenza neuraminidase (NA) and / or a Matrix-2 (M2) polypeptide.

47. A pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, or 32 to 44, or 46, a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, or 46, a first and a second isolated polynucleotide for use according to any of claims 3, 4, 7 to 19, 32 to 44, or 46, a first isolated polynucleotide for use according to any of claims 5 to 19, 32 to 44, or 46, or a vector according to any of claims 20 to 22, 27 to 44, or 46, wherein the or each nucleotide sequence encoding the influenza NA polypeptide is a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the or each nucleotide sequence encoding the influenza M2 polypeptide is a nucleotide sequence encoding a T2_M2_1 amino acid sequence (SEQ ID NO:7).

48. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1).

49. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolatedpolynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1).

50. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1).

51. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, or the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1).

52. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1).

53. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HAamino acid sequence, comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1).

54. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1).

55. A pharmaceutical composition according to claim 46, or 47, a combined preparation according to claim 46, or 47, a first and a second isolated polynucleotide for use according to claim 46, or 47, a first isolated polynucleotide for use according to claim 46, or 47, or a vector according to claim 46, or 47, wherein the first isolated polynucleotide, or first nucleotide sequence, encoding a first optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), and the second isolated polynucleotide, or second nucleotide sequence, encoding a second optimised HA amino acid sequence, comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1).

56. A pharmaceutical composition which comprises: (a) a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence; and (b) a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence; and (c) a pharmaceutically acceptable carrier, excipient, or diluent.

57. A combined preparation which comprises: (a) a first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence; and (b) a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence.

58. A first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, and a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence, for use as a medicament, wherein the first isolated polypeptide is to be administered before, with, or after administration of the second isolated polypeptide.

59. A first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, and a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polypeptide is to be administered before, with, or after administration of the second isolated polypeptide.

60. A first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, for use as a medicament, wherein the first isolated polypeptide is to be administered before, with, or after administration of a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence.

61. A first isolated polypeptide which comprises a first optimised haemagglutinin (HA) amino acid sequence, for use in the prevention, treatment, or amelioration of an influenza infection, wherein the first isolated polypeptide is to be administered before, with, or after administration of a second isolated polypeptide which comprises a second optimised haemagglutinin (HA) amino acid sequence, wherein the first optimised HA amino acid sequence is different to the second optimised HA amino acid sequence.

62. An isolated polypeptide which comprises: (a) a first optimised haemagglutinin (HA) amino acid sequence; and (b) a second optimised haemagglutinin (HA) amino acid sequence, wherein the first HA amino acid sequence is different to the second amino acid sequence.

63. A pharmaceutical composition according to claim 56, or a combined preparation according to claim 57, a first and a second isolated polypeptide for use according to claim 58 or 59, a first isolated polypeptide for use according to claim 60 or 61, or an isolated polypeptideaccording to claim 62, wherein the first and / or second HA amino acid sequence comprises a haemagglutinin H5 amino acid sequence.

64. A pharmaceutical composition according to claim 56 or 63, a combined preparation according to claim 57 or 63, a first and a second isolated polypeptide for use according to claim 58, 59, or 63, a first isolated polypeptide for use according to claim 60, 61, or 63, or an isolated polypeptide according to claim 62 or 63, wherein the first HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1).

65. A pharmaceutical composition according to any of claims 56, 63, or 64, a combined preparation according to any of claims 57, 63, or 64, a first and a second isolated polypeptide for use according to claim 58, 59, 63, or 64, a first isolated polypeptide for use according to claim 60, 61, 63, or 64, or an isolated polypeptide according to claim 62, 63, or 64, wherein the second HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3).

66. A pharmaceutical composition according to any of claims 56, 63, 64, or 65, a combined preparation according to any of claims 57, 63, 64, or 65, a first and a second isolated polypeptide for use according to claim 58, 59, 63, 64, or 65, a first isolated polypeptide for use according to claim 60, 61, 63, 64, or 65, or an isolated polypeptide according to any of claims 62 to 65, wherein the first HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1), and the second HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3).

67. A pharmaceutical composition according to claim 56 or 63, a combined preparation according to claim 57 or 63, a first and a second isolated polypeptide for use according to claim 58, 59, or 63, a first isolated polypeptide for use according to any of claims 60, 61, or 63, or an isolated polypeptide according to claim 62, or 63, wherein the first HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3).

68. A pharmaceutical composition according to claim 56, 63, or 67, a combined preparation according to claim 57, 63, or 67, a first and a second isolated polypeptide for use according to claim 58, 59, 63, or 67, a first isolated polypeptide for use according to any of claims 60, 61, 63, or 67, or an isolated polypeptide according to claim 62, 63, or 67, wherein the second isolated polypeptide comprises T2_HA_9 amino acid sequence (SEQ ID NO:1).

69. A pharmaceutical composition according to claim 56, 63, 67, or 68, a combined preparation according to claim 57, 63, 67, or 68, a first and a second isolated polypeptide for use according to claim 58, 59, 63, 67, or 68, a first isolated polypeptide for use according to any of claims 60, 61, 63, 67, or 68, or an isolated polypeptide according to claim 62, 63, 67,or 68, wherein the first HA amino acid sequence comprises T4_HA_2 amino acid sequence (SEQ ID NO:3), and the second HA amino acid sequence comprises T2_HA_9 amino acid sequence (SEQ ID NO:1).

70. A pharmaceutical composition according to any of claims 1, 7-19, 23, 24, 26, 32 to 44, 46 to 56, or 63 to 69, which further comprises an adjuvant for enhancing an immune response in a subject to a polypeptide, or to a polypeptide encoded by a nucleotide, of the composition.

71. A fusion protein comprising a polypeptide according to any of claims 62 to 69.

72. A pseudotyped virus particle comprising a polypeptide according to any of claims 62 to 69.

73. A pharmaceutical composition according to any of claims 56, or 63 to 69, a combined preparation according to any of claims 57, or 63 to 69, a first and a second isolated polypeptide for use according to any of claims 58, 59, or 63 to 69, or a first isolated polypeptide for use according to any of claims 60, 61, or 63 to 69, wherein the first isolated polypeptide, comprising the first optimised HA amino acid sequence, and / or the second isolated polypeptide comprising the second optimised HA amino acid sequence, further comprises an amino acid sequence of an influenza neuraminidase (NA) and / or a Matrix-2 (M2) polypeptide.

74. A pharmaceutical composition according to any of claims 56, 63 to 69, or 73, a combined preparation according to any of claims 57, 63 to 69, or 73, a first and a second isolated polypeptide for use according to any of claims 58, 59, 63 to 69, or 73, or a first isolated polypeptide for use according to any of claims 60, 61, 63 to 69, or 73, wherein the amino acid sequence of the or each influenza NA polypeptide is a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the amino acid sequence of the or each M2 polypeptide is a T2_M2_1 amino acid sequence (SEQ ID NO:7).

75. A pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, 32 to 44, 46 to 56, 63 to 70, 73, or 74, a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, 46 to 55, 57, 63 to 69, 73, or 74, a vector according to any of claims 20 to 22, 32 to 44, or 46 to 55 or a polypeptide according to any of claims 62 to 69, for use as a medicament.

76. A pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, 32 to 44, 46 to 56, 63 to 70, 73, or 74, a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, 46 to 55, 57, 63 to 69, 73, or 74, a vector according to any of claims 20 to 22, 32 to 44, or 46 to 55, or a polypeptide according to any of claims 62 to 69, for use in the prevention, treatment, or amelioration of an influenza infection.

77. A pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, 32 to 44, 46 to 56, 63 to 70, 73, or 74, a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, 46 to 55, 57, 63 to 69, 73, or 74, a vector according to any of claims 20 to 22, 32 to 44, or 46 to 55, or a polypeptide according to any of claims 62 to 69, for use in inducing an immune response to an influenza virus in a subject.

78. A pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, 32 to 44, 46 to 56, 63 to 70, 73 or 74, a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, 46 to 55, 57, 63 to 69, 73, or 74, a vector according to any of claims 20 to 22, 32 to 44, or 46 to 55 or a polypeptide according to any of claims 62 to 69, for use in immunising a subject against an influenza virus.

79. A method of inducing an immune response to an influenza virus in a subject, which comprises administering to the subject an effective amount of: a pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, 32 to 44, 46 to 56, 63 to 70, 73, or 74; a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, 46 to 55, 57, 63 to 69, 73, or 74; a vector according to any of claims 20 to 22, 32 to 44, or 46 to 55; or a polypeptide according to any of claims 62 to 69.

80. A method of immunising a subject against an influenza virus, which comprises administering to the subject an effective amount of: a pharmaceutical composition according to any of claims 1, 7 to 19, 23, 24, 26, 32 to 44, 46 to 56, 63 to 70, 73, or 74; a combined preparation according to any of claims 2, 7 to 19, 25, 26, 32 to 44, 46 to 55, 57, 63 to 69, 73, or 74; a vector according to any of claims 20 to 22, 32 to 44, or 46 to 55; or a polypeptide according to any of claims 62 to 69.

81. An isolated polynucleotide which comprises a nucleotide sequence encoding a T2_HA_9 amino acid sequence (SEQ ID NO:1), and a nucleotide sequence encoding aninfluenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence, or the complement thereof.

82. An isolated polynucleotide which comprises a nucleotide sequence encoding a T4_HA_2 amino acid sequence (SEQ ID NO:3), and a nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a nucleotide sequence encoding a Matrix-2 (M2) polypeptide amino acid sequence, or the complement thereof.

83. An isolated polynucleotide according to claim 81 or 82, wherein the nucleotide sequence encoding an influenza neuraminidase (NA) polypeptide amino acid sequence comprises a nucleotide sequence encoding a T2_NA_3 amino acid sequence (SEQ ID NO:5), and the nucleotide sequence encoding a Matrix-2 (M2) polypeptide amino acid sequence comprises a nucleotide sequence encoding a T2_M2_1 polypeptide amino acid sequence (SEQ ID NO:7).

84. An isolated polynucleotide according to claim 81 or 83, which comprises a nucleotide sequence of SEQ ID NO:9 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), or the complement thereof.

85. An isolated polynucleotide according to claim 81 or 83, which comprises a nucleotide sequence of SEQ ID NO:15 (S3_T2_3: T2_HA_9 – T2_NA_3 – T2_M2_1), or the complement thereof.

86. An isolated polynucleotide according to claim 82 or 83, which comprises a nucleotide sequence of SEQ ID NO:10 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), or the complement thereof.

87. An isolated polynucleotide according to claim 82 or 83, which comprises a nucleotide sequence of SEQ ID NO:16 (S3_T2_12: T4_HA_2 – T2_NA_3 – T2_M2_1), or the complement thereof.

88. An isolated polypeptide which comprises a T2_HA_9 amino acid sequence (SEQ ID NO:1), and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence.

89. An isolated polypeptide which comprises a T4_HA_2 amino acid sequence (SEQ ID NO:3), and an influenza neuraminidase (NA) polypeptide amino acid sequence, and / or a Matrix-2 (M2) polypeptide amino acid sequence.

90. An isolated polypeptide according to claim 88 or 89, wherein the influenza neuraminidase (NA) polypeptide amino acid sequence comprises a T2_NA_3 amino acidsequence (SEQ ID NO:5), and the Matrix-2 (M2) polypeptide amino acid sequence comprises a T2_M2_1 amino acid sequence (SEQ ID NO:7).

91. A pharmaceutical composition which comprises an isolated polynucleotide according to any of claims 81 to 87, or an isolated polypeptide according to any of claims 88 to 90, and a pharmaceutically acceptable carrier, excipient, or diluent.

92. A vector which comprises an isolated polynucleotide according to any of claims 81 to 87, and a separate promoter operably linked to each different nucleotide sequence of the polynucleotide.

93. A fusion protein comprising a polypeptide according to any of claims 88 to 90.

94. A pseudotyped virus particle comprising a polypeptide according to any of claims 88 to 90.

95. An isolated polynucleotide according to any of claims 81 to 87, an isolated polypeptide according to any of claims 88 to 90, a pharmaceutical composition according to claim 91, or a vector according to claim 92, for use as a medicament.

96. An isolated polynucleotide according to any of claims 81 to 87, an isolated polypeptide according to any of claims 88 to 90, a pharmaceutical composition according to claim 91, or a vector according to claim 92, for use in the prevention, treatment, or amelioration of an influenza infection.

97. An isolated polynucleotide according to any of claims 81 to 87, an isolated polypeptide according to any of claims 88 to 90, a pharmaceutical composition according to claim 91, or a vector according to claim 92, for use in inducing an immune response to an influenza virus in a subject.

98. An isolated polynucleotide according to any of claims 81 to 87, an isolated polypeptide according to any of claims 88 to 90, a pharmaceutical composition according to claim 91, or a vector according to claim 92, for use in immunising a subject against an influenza virus.

99. A method of inducing an immune response to an influenza virus in a subject, which comprises administering to the subject an effective amount of: isolated polynucleotide according to any of claims 81 to 87; an isolated polypeptide according to any of claims 88 to 90; a pharmaceutical composition according to claim 91; ora vector according to claim 92.

94. A method of immunising a subject against an influenza virus, which comprises administering to the subject an effective amount of: isolated polynucleotide according to any of claims 81 to 87; an isolated polypeptide according to any of claims 88 to 90; a pharmaceutical composition according to claim 91; or a vector according to claim 92.