BACK PEPTIDE VACCINE

Abstract

The present invention relates to vaccine compositions containing peptides encoded by an open reading frame (ORF) encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation, and the use of such compositions for the treatment and prevention of viral infections.

Description

Description BACK PEPTIDE VACCINE Invention Engineering Field The invention relates to vaccine compositions containing peptides encoded by an open reading frame (ORE) encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to a positive sense RNA capable of translation, and the use of such compositions for the treatment and prevention of viral infections. Background of the Invention Influenza is a significant global health problem, infecting up to 20% of the world's population each year, causing up to 5 million cases of severe illness and >300,000 deaths worldwide. In the United States alone, an estimated >30,000 deaths and nearly 300,000 hospitalizations are associated with influenza infection each year. With the current emergence of new, severe, and potentially recurrent seasonal illnesses, widespread vaccination campaigns to reduce the incidence of influenza-induced pneumonia are being encouraged by the World Health Organization (WHO). Effectively reducing influenza incidence will require continued intensive surveillance, increased use of currently available influenza vaccines, and the bioavailability of alternative vaccines and antiviral drugs that can provide broader protection against shift-and-drift influenza strains.A successful influenza vaccination campaign can have enormous economic and social impact. The immune response to influenza is governed by both innate and adaptive immunity. The innate immune response to influenza limits initial viral replication but is relatively nonspecific. Efficient clearance of influenza viruses requires a robust adaptive immune response. Conventional influenza vaccines aim to elicit this adaptive immune response by inducing humoral immunity to influenza viruses. Humoral immunity, mediated by secretory IgA and IgM antibodies, provides protection against the initial infection, while IgG antibodies neutralize newly replicating viruses that establish an infection. CD4+ T cell responses can foster humoral immunity and play a role in isotype switching to IgG and in the formation of higher-affinity antibodies and CTL memory.This is emphasized by the finding that hemagglutinin (HA)-specific CD4+ T cells proliferate following influenza vaccination in humans and foster the development of heterosubtypic influenza antibody responses. Despite their ability to induce humoral immunity, conventional influenza vaccines are not fully protective. This is due, at least in part, to antigenic variation. Furthermore, it is thought that cell-mediated immunity may play a key role in influenza protection. CD8+ cytotoxic T lymphocytes (CTLs) mediate viral clearance and have been shown to have cross-reactive responses to different subtypes of influenza A virus. This may help explain the relatively less disease among older individuals who have been vaccinated against influenza or have been exposed to influenza viruses multiple times. Influenza vaccines currently on the market are updated annually. They are designed based on the WHO's annual strain recommendations, and they are manufactured prior to the onset of the influenza season or pandemic. Current influenza vaccines induce a protective humoral immune response against the HA and neuraminidase (NA) glycoproteins on the virion surface. However, the viral HA and NA glycoproteins are highly susceptible to frequent and unpredictable antigenic drift and, less frequently, but more severe, shear mutations, which lead to loss of antibody recognition. This necessitates the frequent development of new vaccines to match the current viral serotypes infecting the human population. Therefore, existing influenza vaccines are expensive to produce and unlikely to protect against new strains emerging mid-season (e.g., H1N1 swine flu). 2009, H5N1, H7N9). In addition, these vaccines are designed to provide antibody-based protection, with little consideration given to the induction of cell-mediated immunity which is essential for eliminating virus-infected cells from the body. Several quadrivalent vaccines (protecting against two influenza A and two influenza B viruses) have been approved by the FDA. While these vaccines provide broader protection than conventional influenza vaccines, they still tend not to protect against new strains emerging mid-season or emerging pandemic strains, and are expensive to produce. Furthermore, like conventional influenza vaccines, quadrivalent vaccines are not designed to elicit cell-mediated immunity, which is essential for eliminating virus-infected cells from the body. A universal influenza vaccine would provide broad protection against all seasonal and pandemic influenza strains for several years, if not lifelong, and is therefore desirable. Developing an effective universal influenza vaccine would reduce the fear of future influenza pandemics and would be more cost-effective than developing, manufacturing, and administering annual seasonal influenza vaccines as currently done. Brief Description of the Invention The present invention relates to a vaccine composition containing an immunogenic peptide encoded by an open reading frame (ORF) encoded by at least a portion of the genome of an ssRNA virus, such as influenza virus, in a sense opposite to a positive-sense RNA capable of translation. The immunogenic peptide containing an epitope capable of recognition by CD8+ T cells. The inventors have unexpectedly identified a number of peptides that are presented by MHC class I molecules on cells infected with influenza viruses and that are encoded by ORFs encoded by the negative-strand genomic region of influenza virus segment 8. These ORFs are widely conserved among human influenza viruses and are therefore thought to confer a selective advantage to these viruses. Including one or more peptides encoded by these conserved ORFs in a vaccine composition may provide protective ability against multiple strains of human influenza viruses, overcoming problems caused by their propensity for antigenic drift and shift. Including a plurality of such peptides, each capable of binding to different HLA supertypes, in a vaccine composition may provide a broad-spectrum vaccine that is effective in individuals possessing different HLA types. The inventor envisages that cells infected with other ssRNA viruses, such as filoviruses or flaviviruses, may also contain peptides encoded by conserved ORFs encoded by regions of the genome in the sense opposite to positive sense RNA capable of translating MHC class I molecules. Including one or more of these peptides in a vaccine composition may provide protective capabilities against multiple virus species, strains or serotypes, providing cross-protection within the virus family. Thus, the present invention provides a vaccine composition comprising an immunogenic peptide containing a CD8+ T cell epitope from a polypeptide encoded by an open reading frame (ORF) encoded by at least a portion of the genome of an ssRNA virus in the opposite sense to a positive sense RNA capable of translation. The present invention further provides: - methods for preventing or treating viral infections, comprising administering a vaccine composition of the invention to an individual infected with, or at risk of infection with, an ssRNA virus; - a method for identifying immunogenic peptides comprising CD8+ T cell epitopes from ORFs encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to a positive sense RNA capable of translation by: (a) identify the ORFs encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to the positive sense RNA capable of translation; (b) predicting the sequence of the polypeptide encoded by the ORF; and (c) assessing whether the peptide that binds the MHC class I molecule includes sequences contained in the predicted sequence, thereby identifying immunogenic peptides containing epitopes capable of being recognized by CD8+ T cells; - an immunogenic peptide containing a CD4+ T cell epitope from a polypeptide encoded by an ORF encoded by at least part of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation; and - a method for determining the pandemic potential of an Influenza A virus, the method comprising the steps of: (i) identifying a first ORF encoded by at least a portion of segment 8 of the Influenza A virus genome in the opposite sense of translation-capable positive-sense RNA; (ii) determining the number of codons contained in the first ORF; and (iii) comparing the number of codons contained in the first ORF with the number of codons contained in a second ORF encoded by at least a portion of segment 8 of the known pandemic Influenza A virus genome in the opposite sense of translation-capable positive-sense RNA, wherein the difference in the number of codons in the first ORF compared to the second ORF is an indication of pandemic potential. Short Description of Image Figure 1: Comparison of IAPSSVKALS mass spectra from Influenza A virus-infected cells (A) and synthetic IAPSSVKALS peptides (B). Some common ions in each spectrum are circled to emphasize the identity of the peptides from infected cells to the synthesized ones. Figure 2: Comparison of the mass spectra of LMQRGPSTF from cells infected with Influenza A virus (A) and the synthetic LMQRGPSTF peptide (B). Some common ions in each spectrum are circled to emphasize the identity of the peptide from infected cells to the synthesized one. Figure 3: Comparison of KITLKFAFNMM mass spectra from Influenza A virus-infected cells (A) and synthetic KITLKFAFNMM peptide (B). Some common ions in each spectrum are circled to emphasize the identity of the peptide from infected cells to the synthesized one. Figure 4: Alignment of NEG8 polypeptide sequences from SEQ ID NO: 1 and 3 to 15. Figure 5: ORF length by year. The graph shows the number of Influenza A viruses collected (Y-axis) by year and month of collection (X-axis). The color code indicates the ORF length present in the viruses collected at each time point. Figure 6: ORF identity by year. Color coding indicates the serotype of each virus plotted. Figure 7: ORF identity by year. Color coding indicates the serotype of each virus plotted. Figure 8: Prevalent ORF length in different species of Influenza A virus. Complete Description of the Invention Vaccine composition The present invention provides a vaccine composition comprising an immunogenic peptide containing a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to a translationally capable positive-sense RNA. This vaccine composition has a number of advantages that will become apparent from the discussion below. The main advantages are summarized here. First, the vaccine composition of the invention superiorly contains peptides containing CD8+ T cell epitopes, such as the epitopes set forth in SEQ ID NO: 5 to 41 and newly identified by the inventor. The vaccine composition is therefore capable of stimulating a cellular immune response (e.g., a CD8+ T cell response) against ssRNA viruses. The viral clearance is mediated by CD8+ cytotoxic T lymphocytes (CTLs) through their cytotoxic activity against infected cells. The stimulated cellular immunity may therefore provide a beneficial defense against viral infections, such as influenza virus, flavivirus, or filovirus infections. Second, the ORF encoding the epitope contained in the immunogenic peptide may be conserved between multiple viruses. The epitope itself may therefore be conserved between multiple viruses. For example, the ORF and / or epitope may be conserved between human influenza A viruses. The vaccine composition may therefore provide cross-protection against a plurality of human influenza A viruses. In this way, the vaccine composition of the invention is suitable for providing broad-spectrum prophylaxis against human influenza A viruses, counteracting problems caused by antigenic shift and antigenic drift to which human influenza A viruses are susceptible. In other words, a single vaccine composition of the invention may induce protective immunity against a wide variety of existing and emerging human influenza A viruses, reducing or eliminating the need for a seasonal influenza vaccine developed annually. ORFs and / or epitopes may be conserved between human influenza A viruses and swine, equine, and / or avian influenza A vaccines. In this way, the vaccine composition of the invention may prevent swine, equine, and / or avian influenza A viruses from establishing in the human population. In other words, in addition to protecting against the presence and emergence of human influenza A viruses, the vaccine composition of the invention may prevent swine, equine, and / or avian influenza A viruses from crossing the species divide. This may prevent the emergence of pandemic influenza A virus strains. Third, the immunogenic peptides contained in the vaccine composition of the invention are capable of binding to different HLA supertypes. The inclusion of multiple peptides, each encompassing a CD8+ T cell epitope capable of binding to a different HLA supertype, results in a vaccine composition that is effective in individuals with different HLA types. In this manner, a single vaccine composition can be used to provide protection against ssRNA viruses in a large proportion of the human population. This provides a cost-effective way to control the incidence and spread of viral infections. Fourth, the polypeptide encoded by the ORF can enhance the fitness of ssRNA viruses in humans. In other words, the polypeptide can confer a selective advantage to the ssRNA virus with which it is encoded. The vaccine composition of the invention can therefore target epitopes associated with the ssRNA virus with a selective advantage. The vaccine composition of the invention can therefore be designed to provide effective prophylaxis against emerging and / or potentially pandemic strains of ssRNA viruses. Fifth, the immunogenic peptides contained in the vaccine composition of the invention can be attached to nanoparticles, such as gold nanoparticles. As explained in more detail below, attachment to nanoparticles reduces or eliminates the need for adjuvants in the vaccine composition. Thus, the vaccine composition of the invention is less likely to cause adverse clinical effects after administration to individuals. Reverse peptide vaccine Single-stranded RNA (ssRNA) viruses are classified as positive-sense or negative-sense depending on the sense or polarity of their genomic RNA. In negative-sense ssRNA viruses, the negative-sense genomic RNA (3' to 5') is complementary to the mRNA and generally must be converted to positive-sense RNA by RNA polymerase before translation. In positive-sense ssRNA viruses, the positive-sense genomic RNA (5' to 3') can also function as mRNA and can be translated into protein in the host cell. That is, replication of negative-sense ssRNA viruses generally occurs after transcription of the genome to form mRNA complementary to the genome, and translation of the mRNA. Replication in positive-sense ssRNA viruses generally occurs after translation of the genomic RNA that doubles as mRNA. Traditionally, it has been assumed that the negative-sense RNA of ssRNA viruses is non-coding. However, non-canonical translation may be possible. It appears that the negative-sense genomic RNA of influenza viruses may actually be capable of translation in the 5' to 3' direction, resulting in gene products different from those obtained by canonical translation (i.e., 3' to 5' transcription forming a complementary mRNA, and 5' to 3' translation of the mRNA). Similarly, RNA complementary to the genome of positive-sense ssRNA viruses may actually be translatable. The inventor has obtained data demonstrating that polypeptides derived from non-canonical translation in ssRNA viruses may contain peptides that are recognized by the immune system of individuals infected with the ssRNA virus. For example, polypeptides derived from non-canonical translation in ssRNA viruses may contain peptides capable of presentation by MHC class I molecules and of recognition by T cell receptors (TCRs) present on CD8+ T cells. In other words, polypeptides derived from non-canonical translation in ssRNA viruses may contain peptides that are CD8+ T cell epitopes. Such immunogenic peptides may be administered to individuals, for example in a vaccine composition, to induce an immune response against the ssRNA virus. In this manner, prophylaxis and / or therapy may be achieved. Thus, the present invention provides a vaccine composition comprising an immunogenic peptide comprising a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation. Immunogenic peptides Immunogenic peptides are peptides capable of eliciting an immune response. The vaccine composition of the invention comprises immunogenic peptides comprising CD8+ T cell epitopes from polypeptides encoded by ORFs encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to its positive sense RNA capable of translation. The vaccine composition may comprise from about one to about 50 such immunogenic peptides, such as from about 2 to 40, 3 to 30, 4 to 25, 5 to 20, 6 to 15, 7, 8, 9 or 10 such immunogenic peptides. Immunogenic peptides containing CD8+ T cell epitopes. CD8+ T cell epitopes are peptides capable of (i) presentation by MHC class I molecules and (ii) recognition by the T cell receptor (TCR) present on CD8+ T cells. Preferably, recognition by the TCR results in activation of CD8+ T cells. Activation of CD8+ T cells can lead to increased proliferation, cytokine production, and / or cytotoxic effects. Typically, CD8+ T cell epitopes are approximately 9 amino acids in length. CD8+ T cell epitopes, however, can be shorter or longer. For example, CD8+ T cell epitopes can be approximately 8, 9, 10, 11, 12, 13, 14, or 15 amino acids in length. CD8+ T cell epitopes can be approximately 8 to 15, 9 to 14, or 10 to 12 amino acids in length. The CD8+ T cell epitopes contained in immunogenic peptides are from polypeptides encoded by ORFs encoded by at least a portion of the genome of ssRNA viruses in the sense opposite to the translationally capable positive-sense RNA. In other words, CD8+ T cell epitopes, in nature, can be contained in or form part of polypeptides encoded by ORFs encoded by at least a portion of the genome of ssRNA viruses in the sense opposite to the translationally capable positive-sense RNA. Polypeptides can be expressed on the surface of ssRNA viruses, or intracellularly within ssRNA viruses. Expression of polypeptides by viruses can be transient, that is, they can only be expressed by ssRNA viruses at specific points in their life cycle and / or under specific environmental conditions. Alternatively, ssRNA viruses can have sustained polypeptide expression.Polypeptides can be structural or functional peptides, such as those involved in the metabolism or replication of ssRNA viruses. In some cases, however, the purpose and / or function of the polypeptide may be unknown. Polypeptides that express CD8+ T cell epitopes can enhance the fitness of ssRNA viruses in humans. For example, polypeptides can enhance viral survival and / or replication in human host cells. Thus, polypeptides can confer a selective advantage to ssRNA viruses. In other words, polypeptide expression can enable ssRNA viruses to survive and / or reproduce better than ssRNA viruses that do not express polypeptides. In this case, evolutionary selective processes can select for viruses in which at least part of the genome encodes, in a positive-sense RNA as opposed to a translation-capable ORF, the ORF encoding the polypeptide. The ORF (and, consequently, the polypeptide) may therefore be conserved among different ssRNA viruses of a particular type.For example, ORFs and / or polypeptides may be conserved between different strains of Influenza A virus, or differ between flaviviruses (e.g., between Zika virus and Dengue virus). ORFs (and, consequently, polypeptides) are conserved between two or more different ssRNA viruses if there is at least 20% (such as at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%) identity between the ORFs encoded by at least part of the genome of each virus, in the opposite sense of the translation-capable positive-sense RNA. An immunogenic peptide may contain only one CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a positive-sense RNA capable of translation. Alternatively, an immunogenic peptide may contain two or more, such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, fifteen or more, or twenty or more such epitopes. As well as the CD8+ T cell epitope(s) of the polypeptide encoded by the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive sense RNA, the immunogenic peptide may contain one or more other CD8+ T cell epitopes, one or more CD4+ T cell epitopes and / or one or more B cell epitopes. For example, the immunogenic peptide may contain one or more, such as two or more, three or more, four or more, five or more, ten or more, fifteen or more, or twenty or more CD8+ T cell epitopes that are not CD8+ T cell epitopes of the polypeptide encoded by the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive sense RNA.Immunogenic peptides may contain one or more, such as two or more, three or more, four or more, five or more, ten or more, fifteen or more, or twenty or more CD4+ T cell epitopes. Immunogenic peptides may contain one or more, such as two or more, three or more, four or more, five or more, ten or more, fifteen or more, or twenty or more B cell epitopes. Preferably, immunogenic peptides containing one or more of the sequences set forth in SEQ ID NO: 5 to 41. The vaccine composition may contain two or more immunogenic peptides, such as about one to about 50, 2 to 40, 3 to 30, 4 to 25, 5 to 20, 6 to 15, 7, 8, 9 or 10 immunogenic peptides. In this case, each of the two or more immunogenic peptides may, for example, be an immunogenic peptide containing a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a translation-capable positive sense RNA. Alternatively, the vaccine composition may contain a mixture of (i) immunogenic peptides containing a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a translation-capable positive sense RNA and (ii) other immunogenic peptides. The vaccine composition may contain two or more immunogenic peptides each containing a distinct CD8+ T cell epitope of a polypeptide encoded by an ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive-sense RNA. In other words, the vaccine composition may contain two or more immunogenic peptides each containing a distinct fragment of a polypeptide encoded by an ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive-sense RNA. Preferably, the fragments are immunogenic.The vaccine composition may contain from one to about 50, 2 to 40, 3 to 30, 4 to 25, 5 to 20, 6 to 15, 7, 8, 9 or 10 immunogenic peptides each containing a different CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to a translation-capable positive sense RNA. In some aspects, each immunogenic peptide may interact with a different HLA subtype, as described in detail below. The vaccine composition may contain (i) one or more (such as about 2 to 40, 3 to 30, 4 to 25, 5 to 20, 6 to 15, 7, 8, 9 or 10) immunogenic peptides each of which contains a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive sense RNA, and (ii) one or more other immunogenic peptides (i.e., immunogenic peptides that do not contain a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive sense RNA). Other immunogenic peptide(s) may therefore contain one or more epitopes, such as approximately 2 to 40, 3 to 30, 4 to 25, 5 to 20, 6 to 15, 7, 8, 9 or 10 epitopes. The epitopes may be B cell epitopes, CD4+ T cell epitopes and / or CD8+ T cell epitopes.A CD4+ T cell epitope, for example, may be a peptide expressed by one or more ssRNA viruses and capable of (i) presentation by MHC class II molecules and (ii) recognition by the T cell receptor (TCR) present on the CD4+ T cell. Alternatively, a CD4+ T cell epitope may be a CD4+ T cell epitope that is not expressed by one or more ssRNA viruses. A CD8+ T cell epitope, for example, may be a peptide expressed by one or more ssRNA viruses and capable of (i) presentation by MHC class I molecules and (ii) recognition by the T cell receptor (TCR) present on the CD8+ T cell. Preferably, a CD8+ T cell epitope is a CD8+ T cell epitope that is not a CD8+ T cell epitope of a polypeptide encoded by an ORF encoded by at least a portion of the genome of the ssRNA virus in a positive sense as opposed to a translation-capable positive sense RNA. CD8+ T cell epitopes can be CD8+ T cell epitopes that are not expressed by one or more ssRNA viruses. Many B cell epitopes, CD4+ T cell epitopes, and CD8+ T cell epitopes (such as B cell epitopes, CD4+ T cell epitopes, and CD8+ T cell epitopes of ssRNA viruses) are known in the art. Methods for identifying B cell epitopes, CD4+ T cell epitopes, and CD8+ T cell epitopes are known in the art. Epitope mapping methods include X-ray co-crystallography, array-based oligopeptide scanning (sometimes called overlapping peptide scan or pepscan analysis), site-directed mutagenesis, high-throughput mutagenesis mapping, hydrogen-deuterium exchange, cross-linking-coupled mass spectrometry, phage modeling, and limited proteolysis. MHC motif prediction methodologies can also be used. CD8+ T cell epitopes presented by cells infected with ssRNA viruses can be identified to directly identify CD8+ T cell epitopes for inclusion in vaccine compositions, as described below. Any of the immunogenic peptides described here may contain any number of amino acids, i.e., any length. Typically, immunogenic peptides are about 8 to about 30, 35 or 40 amino acids in length, such as about 9 to about 29, about 10 to about 28, about 11 to about 27, about 12 to about 26, about 13 to about 25, about 13 to about 24, about 14 to about 23, about 15 to about 22, about 16 to about 21, about 17 to about 20, or have a length of about 18 to about 29 amino acids. Any of the immunogenic peptides described herein may be chemically derived from a polypeptide antigen, for example by proteolytic cleavage. More generally, immunogenic peptides may be synthesized using methods well known in the art. The term peptide encompasses not only molecules in which amino acid residues are joined by a peptide linkage (-CO-NH-) but also molecules in which the peptide bond is inverted. Retro-inverse peptidomimetics can be prepared using well-known methods, for example as described in Meziere et al. (1997) J. Immunol. 159, 3230-3237. This approach involves the creation of pseudopeptides that involve changes involving the backbone, rather than the orientation of the side chains. Meziere et al. (1997) showed that, at least for MHC class II and helper T cell responses, these pseudopeptides are useful. Retro-inverse peptides, which contain an NH-CO bond instead of a CO-NH peptide bond, are much more resistant to proteolysis. Similarly, the peptide bond can be removed entirely provided that a suitable linker moiety maintains the distances between the carbon atoms of the amino acid residues used; it is particularly desirable if the linker moiety has essentially the same charge distribution and essentially the same planarity as the peptide bond. It will also be appreciated that peptides can be suitably blocked at their N- or C-terminus to help reduce susceptibility to exoproteolytic digestion. For example, the N-terminal amino group of a peptide can be protected by reaction with a carboxylic acid and the C-terminal carboxyl group of a peptide can be protected by reaction with an amine. Other examples of modifications include glycosylation and phosphorylation. Another potential modification is that the hydrogen on the side-chain amine of R or K can be replaced by a methylene group (-NH2 can be modified to -NH(Me) or -N(Me)2). The term peptide also includes peptide variants that increase or decrease the half-life of the peptide in vivo. Examples of analogs capable of increasing the half-life of the peptide used according to the invention include peptoid peptide analogs, D-amino acid derivatives of peptides, and peptide-peptoid hybrids. Further embodiments of the polypeptide variants used according to the invention include D-amino acid forms of the polypeptide. Preparation of the polypeptide using D-amino acids rather than L-amino acids greatly reduces any undesirable breakdown of the agent by normal metabolic processes, reducing the amount of the agent that needs to be administered, along with the frequency of administration. Open reading frame (ORF) The CD8+ T cell epitopes contained in immunogenic peptides are from polypeptides encoded by ORFs encoded by at least part of the genome of ssRNA viruses in the sense as opposed to positive sense RNA capable of translation. A reading frame is a grouping of three consecutive nucleotides in a nucleic acid sequence, such as an RNA sequence, that are codons for the amino acids encoded by the nucleic acid sequence. An ORF is the translatable portion of the reading frame. An ORF is a continuous stretch of codons containing a start codon and a stop codon. Within an ORF, an initiation codon (e.g., ATG) can serve as the initiation site for translation of RNA into protein. In the present invention, an ORF encoded by at least a portion of the genome of an ssRNA virus, in the opposite sense to the positive sense RNA, is capable of translation. In negative sense ssRNA viruses, the ORF is contained in the genomic RNA (usually considered negative sense) and, for example, can be translated without interfering with transcription. In positive sense ssRNA viruses, the viral genomic RNA is the same sense as the mRNA and can be translated without interfering with transcription, i.e., the genomic RNA doubles as the mRNA. Thus, the ORF encoded in the opposite sense to the viral genomic RNA and, therefore, the mRNA. An ORF, for example, may be encoded by the entire genome of an ssRNA virus in the sense opposite to a translation-capable positive-sense RNA. Alternatively, an ORF may be encoded by only a portion of the genome of an ssRNA virus in the sense opposite to a translation-capable positive-sense RNA. For example, an ORF may be encoded by approximately 1% to approximately 99%, such as approximately 2% to approximately 98%, approximately 3% to approximately 97%, approximately 5% to approximately 95%, approximately 10% to approximately 90%, approximately 15% to approximately 85%, approximately 20% to approximately 80%, approximately 25% to approximately 75%, approximately 30% to approximately 70%, approximately 40% to approximately 60%, or approximately 50% of the genome of an ssRNA virus in the sense opposite to a translation-capable positive-sense RNA. Some ssRNA viruses have segmented genomes. An ORF may be encoded by all or part of a genome segment, in a sense that is opposite to the positive-sense RNA capable of translation. For example, an ORF may be encoded by approximately 1% to about 99%, such as about 2% to about 98%, about 3% to about 97%, about 5% to about 95%, about 10% to about 90%, about 15' % to about 85%, about 20% to about 80%, about 25' % to about 75%, about 30% to about 70%, about 40' % to about 60%, or about 50% of a genomic segment, in the opposite sense to positive sense RNA capable of translation. The genomic segment, for example, may be segment 1, segment 2, segment 3, segment 4, segment 5, segment 6, segment 7 or segment 8 of the genome of the Influenza A virus. Preferably, the genome segment is segment 8 of the Influenza A virus genome. ORFs can be any length. For example, ORFs can be anywhere from 8 to 300, such as around 9 to around 290, around 10 to around 280, around 11 to around 275, around 12 to around 270, around 13 to around 260, around 14 to around 250, around 15 to around 240, around 16 to around 230, around 17 to around 225, around 18 to around 220, around 19 to around 210, around 20 to around 200, around 25 to around 190, around 30 to around 180, around 35 to around 175, around 40 to around 170, around 45 to around 160, around 50 to around 150, around 55 to around 140, around 60 to around 130, around 65 to around 125, around 70 to around 120, around 75 to about 110, about 80 to about 100, about 85 to about 95, about 167 to about 216, or about 90 codons. ORFs can be as long as 8, as long as 9, as long as 10, as long as 11, as long as 12, as long as 13, as long as 14, as long as 15, as long as 20, as long as 30, as long as 40, as long as 50, as long as 60, as long as 70, as long as 80, as long as 90, as long as 100, as long as 125, as long as 150, as long as 175, as long as 200, as long as 225, as long as 250 or as long as 275 codons. ORFs, for example, can be as long as 31, as long as 36, as long as 100, as long as 100, as long as 125, as long as 150, as long as 175, as long as 200, as long as 225, as long as 250, as long as 275 codons. at least 37, at least 39, at least 40, at least 41, at least 45, at least 48, at least 49, at least 50, at least 53, at least 58, at least 60, at least 63, at least 73, at least 74, at least 80, at least 81, at least 84, at least 85, at least 87, at least 88, at least 89, 92, 93, at least 94, at least 105, 1 at least 21, at least 135, at least 140, at least 167, at least 170, at least 178, at least 197, at least 216 or at least 246 codons. An ORF, for example, can be as long as 85 codons. An ORF, for example, can be as long as 167 codons. An ORF, for example, can be as long as 216 codons. ORFs may include the sequence: TTAAATAAGCTGAAACGAGAAAGTTCTTATCTCTTGCTCCACTTCAAGCAATAGTTGTA AGGCTTGCATAAATGTTATTTGCTCAAAACTATTCTCTGTTACTTCAGTCTATGTCTCACTTC TTCAATCAACCATCTTATTTCTTCAAACTTCTGACTTAATTGTTCTCGCCATTTTCCGTTTCTG TTTTGGAGGGAGTGGAGGTCTCCCATTCTCATTACTGCTTCTCCAAGCGAATCTCTGTAGAGTT TCAGAGACTCGAACTGTGTTATATTCCATTCAAGTCCTCCGATGAGGACCCCAACTGCATTTT TGACATCCTCATCAGTATGTCCTGGAAGAGAAGGCAATGGTGAAATTTCGCCAACAATTGCTCC CTCTTCGGTGAAAGCCCTTAGTAGTATTAGAGTCTCCAGCCGGTCGAAAATCACACTGAAGTTC GCTTTCAGTATGATGTTCTTATCCATGATCGCCTGGTCCATTCTGATACAAAGAGAGCCTGCCA CTTTCTGCTTGGGCATGAGCATGAACCAGTCCCTTGACATCTCCTCAAGAGTCATGTCAGTTAG GTAGCGCGAAGCAGGTACAGAGGCAATGGTCATTTTAAGTGCCTCATCGGATTCTTCCTTCAGA ATCCGCTCCACTATCTTGCTTTCCAGCACGGGTGGCTGTCTCGATGTCCAGACCAAGAGTGCTGC CTCTTCTCTTAGGGACTTCTGATCTCGGCGAAGCCGATCAAGGAATGGGGCATCACCCAGTTC TTGGTCTGCAAACCGTTTGCGGACATGCCAAAGAAAGCAGTCTACCTGAAAGCTTGACACAGTG TTGGAATCCAT (SEQ ID NO: 56). ORFs can encode polypeptides that include the sequences: MLFAQNYSLLSSVYVSLLQSTILFLQTSDLIVLAIFRFFCFGGSGGLPFSLLLLQANLCR VSETRTVLSFHSSPPMRTPTAFLTSSSVCPGREGNGEISPTIAPSSVKALSSIRVSSRSKITLK FAFSMMFLSMIAWSILIQREPATFCLGMSMNQSLDISSRVMSVR (SEQ ID NO: 1). ORFs may include sequences: TATCATTAAATAAGCTGAAATGAGAAAGTTCTTATCTCCTGTTCCACTTCAAACAGCAG TTGTAATGCTTGCATGAATGTTATTTGTTCAAAGCTATTTTCCGTTGTTTTTAGTCTGTGTCTC ACTTCTTCAATCAGCCATCTTATCTCTTCAAACTTTTTGACCTAGCTGTTCTCGCCATTTTCCGT TTCTGTTTTGGAGTAAGTGGAGGTCCCCCCATTCTCATTACTGCTTCTCCAAGCGAATCTCTGTA GATTTTTAGAGACTCGAACTGTGTTATCATCCATTCAAGTCCTCCGATGAGGACCCCAATTGC ATTTTTGACATCCTCAATAGTATGTCCTGGAAAAGAAGGCAATGGTGAGATTTCGCCAACAATT GCTCCCTCTTCGGTGAAAGCCCTTAGTAATAACTATGGTCTCTAGTCGGTCAAAAATCACACTGA AATTCGCTTTCAATATGATGTTTTTCTCCATGATTGCCTGGTCCATTCTGATGCAAAGAGGTCC TTCCACTTTCTGCTTGGGCATTAGCATGAACCAGTTTCTTGACAATTCCTCAATAGTCATGTCA GTTATGTATCGCGAAGCAGGTGTGGAGACCATGGTCATTTTAAGTGCCTCATCAGATTCTTCTT TCAGAATCTTTCTACAATTTGCTTTCCAACATGGGTGGCTGCTTTGATGTCTAGACCGAGAGT ATTGCCTCTTCCCCTTAGGGACCTCTGATCTCGGCGAAGCCGATCAAGGAATGGGGCATCACTC AGTTCTTGGTCTACAACTTGTTTCGGATATGCCAAAGAAAGCAATCTACCTGGAAACTTGACA CAGTGTTGGAATCCATTATGT (SEQ ID NO: 57). ORFs can encode polypeptides that include the sequences: MLFVQSYFPLFLVCVSLLQSAILSLQTFDLAVLAIFRFFCFGVSGGPPFSLLLLQANLCR FLETRTVLSFHSSPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRSKITLK FAFNMMFFSMIAWSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVETMVILSASSDSSF RIFSTICFPTWVAALMSRPRVLPLPLRDL (SEQ ID NO: 2). ORFs can encode polypeptides that include the sequences: MLFARNYSLLSSIYVSLLQSTTLFLQTSDSIVLAIFRFCFGGSGGLLSSLLLLQANLCR VSETRTVLSFHSSPPMRTPIAFLTSSSVCPGREGTGEISPTIAPSSVKALSSIRVSNRSKIILK FAFSVMFLSMIAWSILIQREPATFCLGMSMNQSLDISSRVMSVR (SEQ ID NO: 3). ORF can encode polypeptides that include the sequence: MLFAQNYSLLSSVCVSLLQSTILFLQTSDLIVPAISRFCFGVSCGLPFSLLLLQANLCR VSETRTVLSFHSSPPMRTPTAFLTSSAVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLK FAFSMMFLSMIAWSILIQRGPATFCLGMSMDQSLDISSRVMSVR (SEQ ID NO: 4). ORF can encode polypeptides that include the sequence: MLFAQNYSLLFSICVSLLQSTILFLRTSDLIVLAIFRFCFGVSGGLPVSLLLLQANLCR VLETRTVLSFHSSPPMRTPIAFLTSSLVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLK FAFSMMLLSMIAWSILIQRGPATFCLGMSMNQSLDISSIVMSVR (SEQ ID NO: 5). ORF can encode polypeptides that include the sequence: MLFAQNYSLLFSICASLLQSTILFLRTSDLIVLAIFRFCFGVSGGLPVSLLLLQANLCR VLETRTVLSFHSSPPMRTPIAFLTSSLVCPGREGNGEISPYIAPSSVKALSNIRVSSRSKITLK FAFSMMLLSMIAWSILIQRGPATFCLGMSMNQSLDISSIVMSVR (SEQ ID NO: 6). ORF can encode polypeptides that include the sequence: MLFAQNYSLLSSICVSLLQSAILFLRTFDLIVLAIFRFFCFGVSGGLPFSLLLLQANLCR VLETRTVLSFHSSPPMRTPIAFLTSSLVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLK FAFNMMFLSMIAWSILIQRGPATFCLGISMNQSLDISSIVMSVRYREAGAEAMVILSASSDSSF RILSTICFPTRVAVSMFRPRVLPLPLRDF (SEQ ID NO: 7). ORFs can encode polypeptides that include the sequences: MLFAQNYSLLSSICVSLLQSAILFLRTFDLIVLAIFRFYFGVSGGLPFSSLLLQANLCR VLETRTVLSFHSSPPMRTPIAFLTSSLVCPGREGNGEISPTIAPASVKALSNIRVSSRSKITLK FAFNMMFLSMIAWSILIQRGPATFCLGISMNQSLDISSIVMSBRYREAGAEAMVILSASSDSSF RILSTICFPTRVAVSMFRPRVLPLPLRDF (SEQ ID NO: 8). ORFs can encode polypeptides that include the sequences: Mlfaq RILSTICFPTRVAASMFRPRVLPLPLRDF(SEQ ID NO: 9). ORFs can encode polypeptides that include the sequences: Mlfaq RILSTICFPTRVAASMFRPRVLPLPLRDF (SEQ ID NO: 10). ORFs can encode polypeptides that include the sequences: MLFAQNYSQLFSVCVSLLQSAILSLRTFDLAVLAIFRFFCFGVSGGPPFSLLLPQANLCR VLETRTVLSFHSSPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTRVSSRSKITLK FAFNMMFFSMIAWSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVEAMVILSASSDSSF RIFSTICFPTWVAALMSRPRVLPLPLRDL (SEQ ID NO: 11). ORFs can encode polypeptides that include the sequences: MLFAQNYSQLFLVCVSLLQSAILSLRTFDLAVLAIFRFFCFGVSGGPPFSLLLPQANLCR FLETRTVLSFHSSPPMRTPIAFLTSSIVCPGKEGNGEISPYIAPSSVKALSNTRVSSRSKITLK FAFNMMFFSMIAWSILMQRGPSTFCLGISMNQFLDNSSIVISVMYREAGVEAMVILSASSDSSF RIFSTICFPTWVAALMSRPRVLPLPLRDL (SEQ ID NO: 12). ORFs can encode polypeptides that include the sequences: MLFAQNYSQLFLVCVSLLQSAILSLQTFDLAVLAIFRFFCFGVSGGPPFSLLLLQANLCR FLETRTVLSFHSSPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRSKTTLK FAFNMMFFSMIAWSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVEAMVILSASSDSSF RIFSTICFPTWVAALISRPRVLPLPLRDL (SEQ ID NO: 13). ORFs can encode polypeptides that include the sequences: MLFVQSYFQLFLICVSLLQLAILSLQTFDLAVLAISRFCFGVSGGPPFSLLLLQANLCR FLETRTVLSFHSSPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTIVSSRSKITLK FAFNVMFFSMIAWSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVETMVILSASSDSSF RIFSTICFPTWVAALMSRPRVLPLPLRDL (SEQ ID NO: 14). ORFs can encode polypeptides that include the sequences: MLFVQSYFQLFLICVSPLQLAILSLQTSDLAVLAISRFCFGVSGGPPFSLLLLQANLCR FLETRTVLSFHSSPPMRTPIAFLTASIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRPKITLK FAFNMIFFSMIAWSILMQRGPSTFCLGISMNQFLDSSSIVMSVMYREAGVETMVILSASSDSSF RIFSIICFPAWVAALVSRPRVLPLPLRDL (SEQ ID NO: 15). ORFs can encode polypeptides that include the sequences: MLFVRNYSLSLSICAAFLQLTTLFPQISVPIALATFHFCSGGSEGLPFSSQFLQANLCI FSETRTVLPFHSSPPMRTPTAFLTSS (SEQ ID NO: 58). As mentioned above, the ORF encoding the epitope contained in the immunogenic peptide may be conserved between different ssRNA viruses, such as different ssRNA viruses of the same type. An ORF may be conserved between two or more different ssRNA viruses if there is at least 50% (such as at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%) identity between the ORFs encoded by at least part of the genome of each virus in the sense as opposed to the positive sense RNA capable of translation.For example, an ORF may be conserved between two or more different ssRNA viruses if there is approximately 75% (such as approximately 70% to approximately 80%, e.g., approximately 71%, approximately 72%, approximately 73%, approximately 74%, approximately 76%, approximately 77%, approximately 78%, or approximately 79%) identity between the ORFs encoded by at least part of the genome of each virus, in the sense opposite to the positive-sense RNA capable of translation. The polypeptides encoded by the ORFs may enhance the fitness of the ssRNA viruses in humans, i.e., confer a selective advantage to the ssRNA viruses. ORFs may be conserved between two or more (such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) Influenza A viruses. Influenza A viruses between which ORFs are conserved may be of the same serotype. Influenza A viruses between which ORFs are conserved may be of different serotypes.For example, an ORF may be conserved between two or more viruses each belonging to one of the following serotypes: H1N1, H2N2, H3N2, H5N1, H7N7, H1N2, H9N2, H7N2, H7N3, H10N7, H7N9, H6N1, An ORF may be conserved between two or more (such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) human Influenza A viruses.ORFs may be conserved between one or more (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) human Influenza A viruses and one or more (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) swine Influenza A viruses.ORFs may be conserved between one or more (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) human Influenza A viruses and one or more (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) avian influenza A viruses.ORFs may be conserved between one or more (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) human Influenza A viruses and one or more (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 20 or more, 50 or more, 100 or more, 250 or more, 500 or more, 750 or more, or 1000 or more) equine Influenza A viruses. An ORF may be conserved between two or more (such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, or 20 or more) flaviviruses. For example, an ORF may be conserved between two or more serotypes of Dengue virus selected from DENV-1, DENV-2, DENV-3 and DENV-4. An ORF may be conserved between two or more strains of Zika virus, such as African Zika virus and Asian Zika virus. An ORF may be conserved between one or more serotypes of Dengue virus (e.g., one or more of DENV-1, DENV-2, DENV-3 and DENV4) and one or more strains of Zika virus (e.g., one or both of African Zika virus and Asian Zika virus). An ORF may be conserved between two or more (such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, or 20 or more) filoviruses. For example, an ORF may be conserved between two or more ebolaviruses selected from Zaire ebola virus (ZEBOV), Bundibugyo ebola virus (BDBV), Reston ebola virus (RESTV), Sudan ebola virus (SUDV), and Tai Forest ebola virus (TAFV). An ORF may be conserved between two or more Marburgviruses, such as Marburg virus (MARV) and Ravn virus (RAVV). An ORF may be conserved between one or more ebolaviruses (e.g., one or more of ZEBOV, BDBV, RESTV, SUDV, and TAFV) and one or more Marburgviruses (e.g., one or both of MARC and RAVV). The polypeptide encoded by the ORF, and / or the epitope encompassing it, may similarly be conserved between two or more viruses. The vaccine composition may therefore be capable of providing cross-protection against multiple viruses. A single vaccine composition of the invention is therefore capable of inducing protective immunity against a variety of existing and emerging ssRNA viruses, such as influenza A viruses, flaviviruses, or filoviruses. For example, in one aspect, the polypeptide and / or epitope may be conserved between two or more human influenza A viruses. In this case, the vaccine composition of the invention may be capable of providing protection against two or more human influenza A viruses. In another aspect, the polypeptide and / or epitope may be conserved between human influenza A viruses and swine, equine, and / or avian influenza A viruses.In this case, the vaccine composition of the invention may be capable of protecting a human subject against infection with swine, equine and / or avian influenza A viruses, preventing the swine, equine and / or avian influenza A viruses from crossing the species divide. In any case, the two or more human influenza A viruses may be of the same or different serotypes. Each of the two or more human influenza A viruses may be of serotype H1N1, H2N2, H3N2, H5N1, H7N7, H1N2, H9N2, H7N2, H7N3, H10N7, H7N9 or H6N1. Virus ssRNA viruses that have genomes encoding, in the sense as opposed to positive-sense RNA capable of translating RNA, the ORF encoding the polypeptide can be either negative-sense ssRNA viruses or positive-sense ssRNA viruses. ssRNA viruses can be any negative-sense ssRNA virus. Negative-sense ssRNA viruses are well known in the art and include viruses from the orders Mononegavirales and Bunyvirales. The order Mononegavirales includes the families Bornaviridae, Filoviridae, Mymonaviridae, Nyamiviridae, Paramyxoviridae, Pneumoviridae, Rhabdoviridae, and Sunviridae, and the genera Anphevirus, Arlivirus, Chengtivirs, Crustavirus, and Wastrivirus. The order Bunyavirales includes the families Feraviridae, Fimoviridae, Hantaviridae, Jonviridae, Nairoviridae, Peribunyaviridae, Phasmaviridae, Phenuiviridae, and Tospoviridae. Other negative-sense ssRNA viruses include the families Arenaviridae, Ophioviridae, and Orthomyxoviridae, and the genus Deltavirus. ssRNA viruses can be Orthomyxoviruses. For example, ssRNA viruses can be influenza viruses. The hundreds of strains of influenza viruses that exist can be classified into three main categories, Influenza A, Influenza B, or Influenza C, based on the HA and NA proteins they express. ssRNA viruses can be Influenza A, Influenza B, or Influenza C viruses of any strain. Thus, the ORF encoding the polypeptide containing the CD8+ T-cell epitope can be encoded by at least part of the genome of Influenza A, Influenza B, and / or Influenza C viruses in the sense opposite to the positive-sense RNA capable of translation. Preferably, the ssRNA virus is Influenza A virus. Influenza A viruses can be of any serotype. Preferably, Influenza A viruses are serotypes H1N1, H2N2, H3N2, H5N1, H7N7, H1N2, H9N2, H7N2, H7N3, H10N7, H7N9 or H6N1. Influenza viruses and the ORFs they can encode are discussed in more detail below. ssRNA viruses can be filoviruses. Several species of filoviruses exist in two main genera, Ebolavirus and Marburgvirus. Ebolavirus species include Zaire Ebolavirus (ZEBOV), Bundibugyo Ebolavirus (BDBV), Reston Ebolavirus (RESTV), Sudan Ebolavirus (SUDV), and Tai Forest Ebolavirus (TAFV). Marburgvirus species include Marburg virus (MARV) and Ravn virus (RAVV). A third genus, Cuevavirus, includes the Lloviu virus species. Preferably, ssRNA viruses are Ebolavirus or Marburgvirus. ssRNA viruses can be any positive-sense ssRNA virus. Positive-sense ssRNA viruses are well known in the art and include the families Picornaviridae, Astroviridae, Caliciviridae, Hepeviridae, Flaviviridae, Togaviridae, Arteriviridae, and Coronaviridae. ssRNA viruses can be Flaviviruses. Several species of flaviviruses exist, including Zika virus, Dengue virus, West Nile virus, and yellow fever virus, as well as St. Louis encephalitis virus, Japanese encephalitis virus, Murray Valley encephalitis virus, tick-borne encephalitis virus, Kunjin encephalitis virus, Rocio encephalitis virus, Russian Spring Summer encephalitis virus, Negeishi virus, Kyasanur Forest virus, Omsk hemorrhagic fever virus, Powassan virus, Louping Ill virus, Rio Bravo virus, Tyuleniy virus, Ntaya virus, and Modoc virus. There are four serotypes of Dengue virus (DENV-1, DENV-2, DENV-3, and DENV-4) and two strains of Zika virus (African Zika virus and Asian Zika virus). Preferably, ssRNA viruses are Dengue virus or Zika virus. Influenza virus As described above, the ssRNA virus may be a negative sense ssRNA virus. For example, the ssRNA virus may be an Orthomyxovirus, such as an influenza virus. The influenza virus, for example, may be an Influenza A virus, and an influenza B virus or an influenza C virus. Preferably, the ssRNA virus is an Influenza A virus. The influenza A virus, for example, may be a human influenza A virus, a porcine influenza A virus, an equine influenza A virus, or an avian influenza A virus. The influenza A virus may be a zoonotic influenza A virus. An influenza virus, for example, could be a Spanish flu virus, such as the Influenza A H1H1 virus responsible for the 1918 flu pandemic (“1918 influenza virus”). The complete coding sequence of the 1918 influenza virus is known in the art. An influenza virus, for example, could be a reconstructed Spanish flu virus. A reconstructed Spanish flu virus is an influenza virus that carries coding sequences from eight gene segments from the 1918 influenza virus. For example, a reconstructed Spanish flu virus includes the known coding sequences from the 1918 influenza virus and non-coding regions corresponding to non-coding regions from closely related viruses. Closely related viruses, for example, could be an influenza A H1N1 virus, such as the A / WSN / 33 (H1N1) virus. The genome of the influenza A virus is segmented, containing 8 segments of negative-sense ssRNA. While many structural and genetic similarities exist between human, swine, equine, and avian influenza A viruses, cross-species infection tends to be infrequent and inefficient. However, co-infection of a single host with multiple different influenza A viruses can result in the segmented genome being sorted, giving rise to new strains with pandemic potential. When translated normally (i.e., after transcription to complementary mRNA), segment 8 of the influenza A virus genome encodes two proteins, NS1 and NEP. In human influenza A viruses, segment 8 also encodes a positive-sense ORF opposite the translationally capable positive-sense RNA. This ORF is known as NEG8, as it is encoded by so-called negative strains of segment 8. Nearly all human influenza A viruses isolated in the first half of the 20th century possess a 167-codon NEG8 ORF. The conservation of the 167-codon NEG8 ORF in human influenza A viruses over a period of approximately 50 years suggests that the 167-codon NEG8 ORF confers a selective advantage to human influenza A viruses. This is emphasized by the fact that viruses that have lost the 167-codon NEG8 ORF do not persist in the human population for more than a few years.Around the middle of the 20th century, a mutation of the stop codon TAG of the 167-codon ORF NEG8 to TAT (which encodes tyrosine) occurred, giving rise to an extended, 216-codon ORF NEG8. The mutation had no effect on the rest of the protein encoded by segment 8, due to degeneracy in the amino acid coding. Essentially all human influenza A viruses isolated after 1947 have the 216-codon ORF NEG8, suggesting that this ORF also confers a selective advantage to human influenza A viruses. Currently, the 85-codon ORF NEG8 has also been observed in several human influenza A viruses. The 167-codon and 216-codon ORFs have also been observed in a number of swine and avian influenza A viruses, respectively. ORFs of other lengths have also been observed in human, avian, equine, and swine influenza A viruses (see Example 5). For example, the 93 codon ORF (or less commonly, the 135 codon ORF) has been observed in avian, swine-like, and equine influenza A viruses.ORF 140 codon and ORF 167 codon have been observed in swine influenza A virus. The presence of conserved 85-, 167-, or 216-codon NEG8 ORFs that confer a selective advantage (i.e., increase fitness) to human influenza A viruses has important implications for the emergence of new influenza A virus strains. In particular, co-infection of a host with two or more influenza A viruses can lead to reassortment of the viral genome. Essentially, segments can switch between viruses, giving rise to viruses that have new combinations of genome segments. For example, co-infection with virus X and virus Y can result in the formation of new viruses that have, for example, segments 1 to 7 from virus X and segment 8 from virus Y. This is of concern because segment 8 of human influenza A viruses that have the 216-codon NEG8 ORF can recombine with segments from avian influenza A viruses (e.g., H5N1), equine influenza A viruses, or swine influenza A viruses (e.g., H1N1).Generally, avian influenza A viruses lack the NEG8 ORF, and have limited pathogenicity and / or poor transmissibility in humans. Acquisition of the NEG8 ORF through reassortment with human influenza A viruses could increase the fitness of avian, equine, or swine influenza A viruses in humans, potentially resulting in the development of new pandemic strains. Furthermore, analysis of segment 8 of swine, equine, or avian influenza A viruses has shown that, for a given strain, only a few mutations are required to give rise to the 167-codon or 216-codon NEG8 ORFs that confer viral fitness in humans. For example, only two stop condons need to be removed (each with a single nucleotide change) from segment 8 of the swine-derived H1N1 genome to give rise to the 216-codon NEG8 ORF found in human influenza A viruses. Only one nucleotide change is required to arrive at the 167-codon NEG8 ORF historically found in human influenza A viruses. It is clear, therefore, that a vaccine composition effective against Influenza A virus infection is needed. In one aspect, the vaccine composition of the invention is a vaccine composition against Influenza A virus infection. Preferably, the immunogenic peptide contained in the vaccine composition comprises a CD8+ T cell epitope of a polypeptide encoded by an ORF encoded by at least a portion of segment 8 of the Influenza A virus genome, in a sense opposite to a translation-capable positive sense RNA. Thus, the ORF may be a NEG8 ORF, an ORF encoded by all or a portion of segment 8, in a sense opposite to a translation-capable positive sense RNA.For example, an ORF may be encoded by approximately 1% to approximately 99%, such as approximately 2% to approximately 98%, approximately 3% to approximately 97%, approximately 5% to approximately 95%, approximately 10% to approximately 90%, approximately 15% to approximately 85%, approximately 20% to approximately 80%, approximately 25% to approximately 75%, approximately 30% to approximately 70%, approximately 40% to approximately 60%, or approximately 50% of segment 8, in the sense opposite to the positive sense RNA capable of translation. ORFs can be of any length, as described above. For example, an ORF can be about 8 up to about 300, like about 9 to about 290, about 10 to about 280, about 11 to about 275, about 12 to about 270, about 13 to about 260, about 14 to about 250, about 15 to about 240, about 16 to about 230, about 17 to about 225, around 18 to around 220, around 19 to around 210, around 20 to around 200, around 25 to around 190, around 30 to around 180, around 35 to around 175, around 40 to around 170, around 45 to around 160, around 50 to around 150, around 55 to around 140, around 60 to around 130, around 65 to around 125, around 70 to around 120, around 75 to around 110, around 80 to around 100, around 85 to around 95, around 167 to around 216, or around 90 codons. ORFs can be as long as 8, as long as 9, as long as 10, as long as 11, as long as 12, as long as 13, as long as 14, as long as 15, as long as 20, as long as 30, as long as 40, as long as 50, as long as 60, as long as 70, as long as 80, as long as 90, as long as 100, as long as 125, as long as 150, as long as 175, as long as 200, as long as 225, as long as 250 or as long as 275 codons.An ORF, for example, can have a length of at least 31, at least 36, at least 37, at least 39, at least 40, at least 41, at least 45, at least 48, at least 49, at least 50, at least 53, at least 58, at least 60, at least 63, at least 73, at least 74, at least 80, at least 81, at least 84, at least 85, at least 87, at least 88, at least 89, 92, 93, at least 94, at least 105, 1 at least 21, at least 135, at least 140, at least 167, at least 170, at least 178, at least 197, at least 216 or at least 246 codons. An ORF, for example, can be as long as 85 codons. Preferably, an ORF is at least 167 codons long. Preferably, an ORF is at least 216 codons long. In some aspects, ORFs may include sequences: TTAAATAAGCTGAAACGAGAAAGTTCTTATCTCTTGCTCCACTTCAAGCAATAGTTGTAAGGCT TGCATAAATGTTATTTGCTCAAAACTATTCTCTTGTTATCTTCAGTCTATGTCTCACTTCTTCAA TCAACCATCTTATTTCTTCAAACTTCTGACTTAATTGTTCTCGCCATTTTCCGTTTCTGTTTTG GAGGGAGTGGAGGTCTCCCATTCTCATTACTGCTTCTCCAAGCGAATCTCTGTAGAGTTTCAGA GACTCGAACTGTGTTATCATTCATTCAAGTCCTCCGATGAGGACCCCAACTGCATTTTTGACA TCCTCATCAGTATGTCCTGGAAGAGAAGGCAATGGTGAAATTTCGCCAACAATTGCTCCCTCTT CGGTGAAAGCCCTTAGTAGTATTAGAGTCTCCAGCCGGTCGAAAATCACACTGAAGTTCGCTTT CAGTATGATGTTCTTATCCATGATCGCCTGGTCCATTCTGATACAAAGAGAGCCTGCCACTTTC TGCTTGGCATGAGCATGAACCAGTCCCTTGACATCTCCTCAAGAGTCATGTCAGTTAGGTAGC GCGAAGCAGGTACAGAGGCAATGGTCATTTTAAGTGCCTCATCGGATTCTTCCTTCAGAATCCG CTCCACTATCTGCTTTCCAGCACGGGTGGCTGTCTCGATGTCCAGACCAAGAGTGCTGCCTCTT CCTCTTAGGGACTTCTGATCTCGGCGAAGCCGATCAAGGAATGGGGCATCACCCAGTTCTTGGT CTGCAAACCGTTTGCGGACATGCCAAAGAAAGCAGTCTACCTGAAAGCTTGACACAGTGTTGGA ATCCAT (SEQ ID NO: 56) or a variant of SEQ ID NO: 56. In some aspects, ORFs may include sequences: TATCATTAAATAAGCTGAAATGAGAAAGTTCTTATCTCCTGTTCCACTTCAAACAGCAGTTGTA ATGCTTGCATGAATGATTATTTGTTCAAAGCTATTTTCCGTTGTTTTTAGTCTGTGTCTCACTTC TTCAATCAGCCATCTTATCTCTTCAAACTTTTGACCTAGCTGTTCTCGCCATTTTCCGTTTCTG TTTTGGAGTAAGTGGAGGTCCCCCCATTCTCATTACTGCTTCTCCAAGCGAATCTCTGTAGATTT TTAGAGACTCGAACTGTGTTATCATTCCATTCAAGTCCTCCGATGAGGACCCCAATTGCATTTT TGACATCCTCAATAGTATGTCCTGGAAGAAGGCAATGGTGAGATTTCGCCAACAATTGCTCC CTCTTCGGTGAAAGCCCTTAGTAATACTATGGTCTCTAGTCGGTCAAAAATCACACTGAAATTC GCTTTCAATATGATGTTTTTCTCCATGATTGCCTGGTCCATTCTGATGCAAAGAGGTCCTTCCA CTTTCTGCTTGGGCATTAGCATGAACCAGTTTCTTGACAATTCCTCAATAGTCATGTCAGTTAT GTATCGCGAAGCAGGTGTGGAGACCATGGTCATTTTAAGTGCCTCATCAGATTCTTCTTTCAGA ATTCTTTTCTACAATTTGCTTTCCAACATGGGTGGCTGCTTTTGATGTCTAGACCGAGAGTATTGC CTCTCTCCCCTTAGGGACCTCTGATCTCGGCGAAGCCGATCAAGGAATGGGGCATCACTCAGTTC TTGGTCTACAACTTGTTTCCGGATATGCCAAAGAAAGCAATCTACCTGGAAACTTGACACAGTG TTGGAATCCATTATGT (SEQ ID NO: 57) or a variant of SEQ ID NO: 57. Over the entire length of the nucleotide sequence of SEQ ID NO: 56 or SEQ ID NO: 57, the variant will preferably be at least 50% identical to that sequence based on nucleotide identity. Preferably, the variant may be at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% and more preferably at least 95%, 97% or 99% identical based on nucleotide identity to the nucleotide sequence of SEQ ID NO: 56 or SEQ ID NO: 57 over the entire sequence. There may be at least 80%, for example at least 85%, 90% or 95%, nucleotide identity over a stretch of 100 or more, for example 125, 150, 175 or 200 or more, contiguous nucleotides. As described above, ORFs can be conserved between two or more human influenza A viruses. ORFs can be conserved between one or more human influenza A viruses and one or more avian influenza A viruses. ORFs can be conserved between one or more human influenza A viruses and one or more equine influenza A viruses. ORFs can be conserved between one or more human influenza A viruses and one or more avian influenza A viruses. Swine influenza A. Conserved between two or more viruses Influenza A, ORFs in each of two or more viruses Influenza A preferably has at least 50% (such as at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%) identity over the entire sequence with the ORF in each of the other Influenza A viruses. For example, an ORF may be conserved between two or more Influenza A viruses if there is about 75% (such as about 70% to about 80%, for example about 71%, about 72%, about 73%, about 74%, about 76%, about 77%, about 78%, or about 79%) identity between the ORFs in each virus. The ORF may encode a polypeptide that includes the sequence MLFAQNYSLLSSVYVSLLQSTILFLQTSDLIVLAIFRFCFGGSGGLPFSLLLLQANLCRVSETR TVLSFHSSPPMRTPTAFLTSSSVCPGREGNGEISPTIAPSSVKALSSIRVSSRSKITLKFAFSM MFLSMIAWSILIQREPATFCLGMSMNQSLDISSRVMSVR (SEQ ID NO: 1) or its variants. SEQ ID NO: 1 is a sequence of 167 amino acids encoded by the nucleotide sequence of SEQ ID NO: 56. ORF may encode a polypeptide that includes the sequence MLFVQ SYFPLFLVCVSLLQSAILSLQTFDLAVLAIFRFCFGVSGGPPFSLLLLQANLCRFLETRTVLSF HSSPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRSKITLKFAFNMMFFSM IAWSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVETMVILSASSDSSFRIFSTICFPT WVAALMSRPRVLPLPLRDL( SEQ ID NO: 2) or variants thereof. SEQ ID NO: 2 is a 216 amino acid sequence encoded by the nucleotide sequence of SEQ ID NO: 57. The ORF may encode a polypeptide that includes the sequence MLFARNYS LLSSIYVSLLQSTTLFLQTSDSIVLAIFRFCFGGSGGLLSSLLLLQANLCRVSETRTVLSFHSS PPMRTPIAFLTSSSVCPGREGTGEISPTIAPSSVKALSSIRVSNRSKIILKFAFSVMFLSMIAW SILIQREPATFCLGMSMNQSLDISSRVMSVR (SEQ ID NO: 3) or variants thereof. The ORF may encode a polypeptide that includes the sequence MLFAQNYSL LSSVCVSLLQSTILFLQTSDLIVPAISRFCFGVSCGLPFSLLLLQANLCRVSETRTVLSFHSSP PMRTPTAFLTSSAVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLKFAFSMMFLSMIAWS ILIQRGPATFCLGMSMDQSLDISSRVMSVR (SEQ ID NO: 4) or variants thereof. The ORF can encode a polypeptide that includes the sequence MLFAQNYSL LFSICVSLLQSTILFLRTSDLIVLAIFRFCFGVSGGLPVSLLLLQANLCRVLETRTVLSFHSSP PMRTPIAFLTSSLVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLKFAFSMMLLSMIAWS ILIQRGPATFCLGMSMNQSLDISSIVMSVR (SEQ ID NO: 5) or its variants. The ORF can encode a polypeptide that includes the sequence MLFAQNYSL LFSICASLLQSTILFLRTSDLIVLAIFRFCFGVSGGLPVSLLLLQANLCRVLETRTVLSFHSSP PMRTPIAFLTSSLVCPGREGNGEISPYIAPSSVKALSNIRVSSRSKITLKFAFSMMLLSMIAWS ILIQRGPATFCLGMSMNQSLDISSIVMSVR (SEQ ID NO: 6) or its variants. The ORF can encode a polypeptide that includes the sequence MLFAQNYSL LSSICVSLLQSAILFLRTFDLIVLAIFRFCFGVSGGLPFSLLLLQANLCRVLETRTVLSFHSSP PMRTPIAFLTSSLVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLKFAFNMMFLSMIAWS ILIQRGPATFCLGISMNQSLDISSIVMSVRYREAGAEAMVILSASSDSSFRILSTICFPTRVAV SMFRPRVLPLPLRDF (SEQ ID NO: 7) or its variants. The ORF can encode a polypeptide that includes the sequence MLFAQNYSL LSSICVSLLQSAILFLRTFDLIVLAIFRFYFGVSGGLPFSSLLLQANLCRVLETRTVLSFHSSP PMRTPIAFLTSSLVCPGREGNGEISPTIAPASVKALSNIRVSSRSKITLKFAFNMMFLSMIAWS ILIQRGPATFCLGISMNQSLDISSIVMSBRYREAGAEAMVILSASSDSSFRILSTICFPTRVAV SMFRPRVLPLPLRDF (SEQ ID NO: 8) or its variants. The ORF can encode a polypeptide that includes the sequence MLFAQNYSL LSSICVSLLQSAILSLRTFDLTVLAIFRFCFGVSGGLPFSLLLPQANLCRVLETRTVLSFHSSP PMRTPIAFLTSSIVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLKFAFNMTFLSMIAWS ILMQRGPSTFCLGISMNQSLDNSSIVMSVRYREAGAEAMVILSASSDSSFRILSTICFPTRVAA SMFRPRVLPLPLRDF(SEQ ID NO: 9) or its variants. The ORF can encode a polypeptide that includes the sequence MLFAQNYSL LSSICVSLLQSAILSLRTFDLIVLAIYRFCFGVSGCLPFSLLLLQANLCRFLETRTVLSFHSSP PMRTPIAFLTSSIVCPGREGNGEISPTIAPSSVKALSNIRVSSRSKITLKFAFNMMFLSMIAWS ILMQRGPSTFCLGISMNQSLDNSSIVMSVRYREAGAEAMVILSASSDFSFRILSTICFPTRVAA SMFRPRVLPLPLRDF (SEQ ID NO: 10) or its variants. The ORF can encode a polypeptide that includes the sequence MLFAQNYSQ LFSVCVSLLQSAILSLRTFDLAVLAIFRFFCFGVSGGPPFSLLLPQANLCRVLETRTVLSFHSSP PMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTRVSSRSKITLKFAFNMMFFSMIAWS ILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVEAMVILSASSDSSFRIFSTICFPTWVAA LMSRPRVLPLPLRDL (SEQ ID NO: 11) or its variants. The ORF may encode a polypeptide that includes the sequence MLFAQNYS QLFLVCVSLLQSAILSLRTFDLAVLAIFRFCFGVSGGPPFSLLLPQANLCRFLETRTVLSFHSS PPMRTPIAFLTSSIVCPGKEGNGEISPYIAPSSVKALSNTRVSSRSKITLKFAFNMMFFSMIAW SILMQRGPSTFCLGISMNQFLDNSSIVISVMYREAGVEAMVILSASSDSSFRIFSTICFPTWVA ALMSRPRVLPLPLRDL (SEQ ID NO: 12) or variants thereof. The ORF may encode a polypeptide that includes the sequence MLFAQNYS QLFLVCVSLLQSAILSLQTFDLAVLAIFRFCFGVSGGPPFSLLLLQANLCRFLETRTVLSFHSS PPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRSKTTLKFAFNMMFFSMIAW SILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVEAMVILSASSDSSFRIFSTICFPTWVA ALISRPRVLPLPLRDL (SEQ ID NO: 13) or variants thereof. The ORF may encode a polypeptide that includes the sequence MLFVQSY FQLFLICVSLLQLAILSLQTFDLAVLAISRFCFGVSGGPPFSLLLLQANLCRFLETRTVLSFHS SPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTIVSSRSKITLKFAFNVMFFSMIA WSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVETMVILSASSDSSFRIFSTICFPTWV AALMSRPRVLPLPLRDL (SEQ ID NO: 14) or variants thereof. The ORF may encode a polypeptide that includes the sequence MLFVQSYF QLFLICVSPLQLAILSLQTSDLAVLAISRFCFGVSGGPPFSLLLLQANLCRFLETRTVLSFHSS PPMRTPIAFLTASIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRPKITLKFAFNMIFFSMIAW SILMQRGPSTFCLGISMNQFLDSSSIVMSVMYREAGVETMVILSASSDSSFRIFSIICFPAWVA ALVSRPRVLPLPLRDL (SEQ ID NO: 15) or variants thereof. On the entire length of the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO: 15, the variant will preferably be at least 50% identical to that sequence based on amino acid identity. More preferably, the variant can be at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% and more preferably at least 95%, 97% or 99% identical based on amino acid identity to the amino acid sequences of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO: 15 over the entire sequence. There can be at least 80%, for example at least 85%, 90% or 95%, amino acid identity over a stretch of 100 or more, for example 125, 150, 175 or 200 or more, adjacent amino acids. The polypeptide encoded by an ORF may be conserved between two or more human influenza A viruses. The polypeptide may be conserved between one or more human influenza A viruses and one or more avian influenza A viruses. The polypeptide may be conserved between one or more viruses. Human influenza A and one or more equine influenza A viruses. Polypeptides may be conserved between one or more viruses. Human influenza A and one or more swine influenza A viruses. Conserved between two or more influenza A viruses, the polypeptide encoded by an ORF in each of the two or more influenza A viruses preferably has at least 50% (such as at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%) identity over its entire sequence with the polypeptide encoded by an ORF in each of the other influenza A viruses. For example, a polypeptide may be conserved between two or more Influenza A viruses if there is about 75% (such as about 70% to about 80%, e.g., about 71%, about 72%, about 73%, about 74%, about 76%, about 77%, about 78%, or about 79%) identity between the polypeptides encoded by the ORFs in each virus. CD8+ T cell epitopes of polypeptides may be conserved between two or more human influenza A viruses. Epitopes may be conserved between one or more human influenza A viruses and one or more avian influenza A viruses. Epitopes may be conserved between one or more human influenza A viruses and one or more equine influenza A viruses. Epitopes may be conserved between one or more human influenza A viruses and one or more swine influenza A viruses. Conserved between two or more Influenza A viruses, the epitope encoded by an ORF in each of the two or more Influenza A viruses preferably has at least 50% (such as at least 60%, at least 70%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%) identity over the entire sequence with the epitope encoded by an ORF in each of the other Influenza A viruses.For example, an epitope may be conserved between two or more Influenza A viruses if there is approximately 75% (such as approximately 70% to approximately 80%, e.g., approximately 71%, approximately 72%, approximately 73%, approximately 74%, approximately 76%, approximately 77%, approximately 78%, or approximately 79%) identity between the epitopes encoded by the ORFs in each virus. ORFs, polypeptides and / or epitopes may be conserved in between human Influenza A H1H1 viruses. ORFs, polypeptides and / or epitopes may be conserved among human Influenza A H5N1 viruses. ORFs, polypeptides and / or epitopes may be conserved among human Influenza A H3N2 viruses. ORFs, polypeptides and / or epitopes may be conserved among human Influenza A H2N2 viruses. ORFs, polypeptides and / or epitopes may be conserved among human Influenza A H7N7 viruses. ORFs, polypeptides and / or epitopes may be conserved among human Influenza A H7N9 viruses. ORFs, polypeptides and / or epitopes may be conserved among avian Influenza A H1N1 viruses. ORFs, polypeptides and / or epitopes may be conserved among avian Influenza A H5N1 viruses. ORFs, polypeptides and / or epitopes may be conserved among avian Influenza A H3N2 viruses. ORFs, polypeptides and / or epitopes may be conserved among avian Influenza A H2N2 viruses. ORFs, polypeptides and / or epitopes may be conserved among avian Influenza A H7N7 viruses.ORFs, polypeptides and / or epitopes may be conserved among avian H7N9 influenza A viruses. ORFs, polypeptides and / or epitopes may be conserved among swine H1N1 influenza A viruses. ORFs, polypeptides and / or epitopes may be conserved among swine H5N1 influenza A viruses. ORFs, polypeptides and / or epitopes may be conserved among swine Influenza A H3N2 viruses. ORFs, polypeptides and / or epitopes may be conserved among swine Influenza A H2N2 viruses. ORFs, polypeptides and / or epitopes may be conserved among swine Influenza A H7N7 viruses. ORFs, polypeptides and / or epitopes may be conserved among swine Influenza A H7N9 viruses. ORFs, polypeptides and / or epitopes may be conserved among equine Influenza A H1N1 viruses. ORFs, polypeptides and / or epitopes may be conserved among equine Influenza A H5N1 viruses. ORFs, polypeptides and / or epitopes may be conserved among equine Influenza A H3N2 viruses. ORFs, polypeptides, and / or epitopes may be conserved among equine Influenza A H2N2 viruses. ORFs, polypeptides, and / or epitopes may be conserved among equine Influenza A H7N7 viruses. ORFs, polypeptides, and / or epitopes may be conserved among equine Influenza A H7N9 viruses. ORFs are conserved between (i) human Influenza A H1N1 viruses, (ii) human Influenza A H5N1 viruses, (iii) human Influenza A H5N1 viruses. Human influenza A H3N2, (iv) human influenza A H2N2 virus, (v) human influenza A H7N7 virus, (vi) human influenza A H7N9 virus, (vii) avian influenza A H1N1 virus, (viii) viruses Avian influenza A H5N1, (ix) avian influenza A H3N2 virus, (x) avian influenza A H2N2 virus, (xi) avian influenza A H7N7 virus, (xii) avian influenza A H7N9 virus, (xiii) avian influenza A virus Swine influenza A H1N1, (xiv) swine influenza A H5N1 virus, (xv) swine influenza A H3N2 virus, (xvi) swine influenza A H2N2 virus, (xvii) swine influenza A H7N7 virus, (xviii) swine influenza A H7N9 virus, (xix) equine influenza A H1N1 virus, (xx) equine influenza A H5N1 virus, (xxi) equine influenza A H3N2 virus, (xxii) equine influenza A H2N2 virus, (xxiii) equine influenza A H7N7 virus and / or (xxiv) equine influenza A H7N9 virus, singly or in any combination. Polypeptides can be conserved between (i) human Influenza A H1N1 virus, (ii) human Influenza A H5N1 virus, (iii) human Influenza A H3N2 virus, (iv) human Influenza A H2N2 virus, (v) human Influenza A H7N7 virus, (vi) human Influenza A H7N9 virus, (vii) avian Influenza A H1N1 virus, (viii) avian Influenza A H5N1 virus, (ix) avian Influenza A H3N2 virus, (x) avian Influenza A H2N2 virus, (xi) avian Influenza A H7N7 virus, (xii) avian Influenza A H7N9 virus, (xiii) swine Influenza A H1N1 virus, (xiv) swine Influenza A H5N1 virus, (xv) swine Influenza A H3N2 virus, (xvi) swine influenza A H2N2 virus, (xvii) swine influenza A H7N7 virus, (xviii) swine influenza A H7N9 virus, (xix) equine influenza A H1N1 virus, (xx) equine influenza A H5N1 virus, (xxi) equine influenza A H3N2 virus, (xxii) equine influenza A H2N2 virus, (xxiii) equine influenza A H7N7 virus and / or (xxiv) equine influenza A H7N9 virus, singly or in any combination. Epitopes can be conserved between (i) human H1N1 influenza A virus, (ii) human H5N1 influenza A virus, (iii) human H3N2 influenza A virus, (iv) human H2N2 influenza A virus, (v) human H7N7 influenza A virus, (vi) human H7N9 influenza A virus, (vii) avian influenza A virus, (ii avian, (ix) avian Influenza A H3N2 virus, (x) avian influenza A H2N2 virus, (xi) avian influenza A H7N7 virus, (xii) avian influenza A H7N9 virus, (xiii) swine influenza A H1N1 virus, (xiv) swine influenza A H5N1 virus, (xv) influenza A virus H3N2, (xv) swine, (xvii) swine H7N7 influenza A virus, (xviii) swine H7N9 influenza A virus, (xix) equine H1N1 influenza A virus, (xx) equine H5N1 influenza A virus, (xxi) equine H3N2 influenza A virus, (xxii) equine H2N2 influenza A virus, (xxiii) equine influenza A virus (xxiii) A H7N9 equine, singly or in any combination. Conservation of epitopes between two or more influenza A viruses may enable a vaccine composition to provide protection against multiple influenza A viruses. For example, upon administration to an individual, the vaccine composition may induce a protective immune response against infection with some or all influenza A viruses possessing conserved epitopes. In this manner, a single vaccine composition may be used to prevent or treat infection with a wide variety of influenza A viruses. This may help to overcome some of the problems associated with existing influenza A virus vaccines. In particular, targeting conserved epitopes may avoid the need to frequently develop new vaccines to match the current viral serotype(s) infecting the human population. The vaccine composition of the invention may be used to prevent or treat new strains of infection that emerge mid-season, such as strains with pandemic potential.The vaccine composition of the invention can be used to prevent or treat infections with strains arising from the selection of segments of swine, equine and / or avian influenza A viruses with segment 8 of human influenza A viruses. In one aspect, a CD8+ T cell epitope contained in an ORF is predicted to be at least 85, at least 167, or at least 216 codons long in swine, equine, and / or avian influenza A viruses, such as swine influenza A viruses of serotype H1N1. For example, a CD8+ T cell epitope contained in an ORF having a length of at least 85, at least 167, or at least 216 codons would appear in swine, equine, and / or avian influenza A viruses should segment 8 be mutated. For example, a CD8+ T cell epitope contained in an ORF of at least 85, at least 167 or at least 216 codons that will appear in swine, equine and / or avian Influenza A viruses must have one or more nucleotides (such as two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more or ten or more nucleotides) in segment 8 substituted for a different nucleotide.Substitutions for different nucleotides can change the stop codon encoded by segment 8 in the opposite sense to the positive-sense RNA capable of translating into a codon encoding an amino acid. For example, a single nucleotide substitution in the stop codon UAG can give rise to the codons UAU, UAC, UUG, UCG, UGG, CAG, AAG, or GAG, which encode amino acids. By incorporating immunogenic peptides containing CD8+ T cell epitopes contained within an ORF predicted to be at least 85, at least 167 or at least 216 codons long in swine, equine and / or avian influenza A viruses into a vaccine composition, the ability of the vaccine composition to protect against potentially pandemic strains of influenza A viruses may be enhanced. For example, it may be possible for the vaccine composition to induce a protective immune response against swine, equine or avian influenza A viruses that possess the 85 codon, 167 codon or 216 codon NEG8 ORF found in human influenza A viruses and confer virus fitness in humans. NEG8 peptide As set forth in the Examples, the present inventor has identified a number of peptides that are (i) from a polypeptide encoded by an ORF encoded by segment 8 of human Influenza A virus in the sense opposite to a translation-capable positive-sense RNA (ORF NEG8), and (ii) presented by MHC class I molecules on cells infected with human influenza A virus. Accordingly, the present inventor has identified a number of CD8+ T cell epitopes encoded by the ORE NEG8, the Epitopes being set forth in Tables 1 and 2 below. Table 1 SEQ ID NO: Sekuens Protein ID Modifikasi Kepercayaan 486,79718 19 PMRTPIAFL NEG8 Medium 1.74 349,20383 20 ISMNQFLDNS NEG8 M3(Oksidasi) Medium 1.67 592,77045 21 LMQRGPSTF NEG8 Medium 1.66 518,77515 22 FHSSPPMRTP NEG8 Medium 1,65 386,18805 23 KITLKFAFNMM NEG8 M10 (Oksidasi); M11 (Oksidasi) Medium 1,60 688,34729 24 LVCVSLLQSAIL SL NEG8 Medium 1,48 729,93231 Tabel 2 SEQ ID NO: Sekuens Protein Motif Xcorr m / z 25 AFNMMFLSM NSP A2 4 1.35 554.24 26 AILSLQTFD NSP A2 4 1.10 504.26 27 DNSSIVISV NSP 1.40 467.24 28 IAWSILIQ NS1 1.22 472.28 29 IVMSVMYR NSP A3 1.17 507.75 30 FLICVSPLQL NSP A2 / 24 1.76 566.81 31 GGLPFSLLL NS1 1.82 458.78 32 LFLICVSLL NSP A2 4 1.74 510.81 33 SPLQLAILSL NSP B7 1,90 527,82 34 IFRFCFGGSG PB2 polymerase 1,49 545,76 35 VAASMFRP NSP 1,45 447,74 36 LSLQTSDLA NSP 1, 11 474,25 37 SIRVSNRS PB2 polymerase 1, 08 459,76 38 FSVMFLSM NS1 1, 17 489,22 39 SVKALSSI HA A2 / 24 1, 15 402,74 40 ALMSRPRV NSP A2 1,24 465,27 41 EGNGEISPT NSP 1, 02 452,21 42 AFNMMFFS NSP 1, 06 505.69 43 PAISRFCF HA A2 4 1.48 470.73 44 AFSVMFLSM NSP A2 4 1.36 516.74 45 LIQRGPATFC L Protein matriks A2 / 24 1.36 609.83 46 LIQRGPATF Protein matriks 47 AILSLQTFD NSP A2 4 1.10 504.26 48 ALSSIRVSS PB2 polymerase A2 B7 1.10 460.25 49 FSMMLLSMI PB1 polymerase 1.00 560.76 50 SPPMRTPT Protein PA-X 1.13 451.72 51 LIVLAIYRFC NSP A2 4 1.11 605.86 52 SLRTFDLA NSP A2 1, 09 461,74 53 MLFVQSYFQ NSP 1, 05 581,79 Compose the vaksin dapat mengandung satu atau lebih peptida yang ditetapkan dalam SEQ ID NO: 5 sampai 41. or more, eight or more, nine or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 or more, 23 or more, 24 or more, 25 or more, 26 or more, 27 or more, 28 or more, 29 or more, 30 or more, 31 or more, 32 or more, 33 or more, 34 or more, 35 or more, or 36 or more peptides set forth in SEQ ID NO: 5 to 41, in any combination. The vaccine composition can contain all the peptides set forth in SEQ ID NO: 5 to 41. The vaccine composition, for example, may contain one or more peptides each comprising one of the peptides set forth in SEQ ID NO: 5 to 41. The vaccine composition, for example, may contain one or more peptides each comprising one of the peptides set forth in SEQ ID NO: 5 to 41. The peptide comprising the peptide set forth in one of SEQ ID NO: 5 to 41 may contain the peptide set forth in one of SEQ ID NO: 5 to 41 and any other number of amino acids at the N terminus and / or C terminus of the peptide set forth in one of SEQ ID NO: 5 to 41.For example, a vaccine composition may contain a peptide specified in any one of SEQ ID NO: 5 to 41 and one or more, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, 15 or more, 20 or more or 25 or more amino acids at the N terminal of the peptide specified in any one of SEQ ID NO: 5 to 41. For example, a vaccine composition may contain a peptide specified in any one of SEQ ID NO: 5 to 41 and one or more, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, 15 or more, 20 or more or 25 or more amino acids at the C terminal of the peptide specified in any one of SEQ ID NO: 5 to 41.The number of amino acids at the N terminal and C terminal of the peptides specified in any of SEQ ID NO: 5 to 41 may be the same or different. Since the NEG8 ORF is highly conserved among human Influenza A viruses, SEQ ID NO: 5 to 41 should also be conserved among human Influenza A viruses. Vaccine compositions containing one or more of the peptides specified in SEQ ID NO: 5 to 41 may therefore have advantages related to the inclusion of the conserved and specified epitopes above. Any one of SEQ ID NO: 5 to 41 may be present in an ORF predicted to be at least 167 or more long. 216 codons in swine, equine and / or avian Influenza A viruses. Vaccine compositions containing one or more of the peptides specified in SEQ ID NO: 5 to 41 may therefore have the advantages set out above. Cross-protection vaccine composition As established above, the NEG8 ORF is highly conserved among human influenza A viruses, and is also present in avian, equine, and / or swine influenza A viruses. Other ssRNA viruses may therefore have ORFs encoded by at least a portion of the genome in the sense opposite to the translation-capable positive-sense RNA, and which are conserved among viruses of the same genus or family. The polypeptide encoded by the ORF, and the CD8+ T-cell epitope(s) it contains, may also be conserved. For example, ORFs, polypeptides and / or epitopes may be conserved among influenza B viruses. ORFs, polypeptides and / or epitopes may be conserved among influenza C viruses. ORFs, polypeptides, and / or epitopes may be conserved among flaviviruses, such as Ebolavirus and / or Marburgvirus. For example, ORFs, polypeptides, and / or epitopes may be conserved between two or more of ZEBOV, BDBV, RESTV, SUDV, and TAFV. ORFs, polypeptides, and / or epitopes may be conserved between Marburgvirus. For example, ORFs, polypeptides, and / or epitopes may be conserved between MARV and RAVV. ORFs, polypeptides, and / or epitopes may be conserved between Ebolavirus and Marburgvirus. For example, ORFs, polypeptides, and / or epitopes may be conserved between one or more of ZEBOV, BDBV, RESTV, SUDV, and TAFV and one or more of MARV and RAVV. ORFs, polypeptides, and / or epitopes may be conserved among flaviviruses. For example, ORFs, polypeptides, and / or epitopes may be conserved between two or more of Zika virus, Dengue virus, West Nile virus, and yellow fever virus, as well as St. Louis encephalitis virus, Japanese encephalitis virus, Murray Valley encephalitis virus, tick-borne encephalitis virus, Kunjin encephalitis virus, Rocio encephalitis virus, Russian Spring Summer encephalitis virus, Negeishi virus, Kyasanur Forest virus, Omsk hemorrhagic fever virus, Powassan virus, Louping Ill virus, Rio Bravo virus, Tyuleniy virus, Ntaya virus, and Modoc virus. For example, ORFs, polypeptides, and / or epitopes may be conserved between Zika virus and Dengue virus, or Zika virus, Dengue virus, and West Nile virus. ORFs, polypeptides, and / or epitopes may be conserved among Zika viruses. For example, ORFs, polypeptides and / or epitopes may be conserved between African Zika virus and Asian Zika virus.ORFs, polypeptides, and / or epitopes may be conserved among dengue viruses. For example, ORFs, polypeptides, and / or epitopes may be conserved between two or more of DENV-1, DENV-2, DENV-3, and DENV-4. As mentioned, incorporating conserved epitopes into a vaccine composition can provide protective properties against multiple viral species, strains, or serotypes, providing cross-protection within a genus and / or genus family. Thus, a single vaccine composition can be used to provide protection against a variety of different ssRNA viruses. This provides a cost-effective way to control the spread of ssRNA viral infections. Inclusion of conserved peptides into a vaccine composition can provide protective properties against emerging ssRNA viral strains, aiding in long-term infection control. Furthermore, if the ssRNA virus is a flavivirus, incorporating conserved epitopes into the vaccine composition may beneficially prevent or minimize the development of antibody-dependent increases in Dengue virus infection following administration of the vaccine composition. Interaction with HLA supertypes The vaccine composition may contain at least one immunogenic peptide containing a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation, and that interacts with at least two different HLA supertypes. This allows the vaccine composition to elicit a CD8+ T cell response in a greater proportion of individuals to whom the vaccine composition is administered. This is because the vaccine composition must be capable of eliciting a CD8+ T cell response in all individuals of the HLA supertypes that interact with the CD8+ T cell epitope.The vaccine composition may contain at least two, at least three, at least four, at least five, at least ten, at least fifteen, or at least twenty immunogenic peptides each comprising a CD8+ T cell epitope of a polypeptide encoded by an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to the positive sense RNA capable of translating and interacting with at least two different HLA supertypes. Each immunogenic peptide may interact with at least two, at least three, at least four, at least five, at least six, at least 7, at least 8, at least 9 or at least 10 different HLA supertypes. Each immunogenic peptide may interact with two or more of HLA-A1, HLA-A2, HLA-A3, HLA-A24, HLA-B7, HLA-B8, HLA-B27, HLA-B44, HLA-B58 or HLA-B62, or any other HLA supertype known in the art, in any combination. A vaccine composition may contain two or more immunogenic peptides where (i) each contains a distinct CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to a translation-capable positive-sense RNA, and (ii) each interacts with a distinct HLA supertype. Incorporating two or more such immunogenic peptides in a vaccine composition may enable the vaccine composition to elicit a CD8+ T cell response in a greater proportion of individuals to whom the vaccine composition is administered. This is because the vaccine composition must be capable of eliciting a CD8+ T cell response in all individuals of the HLA supertype that interacts with any of the CD8+ T cell epitopes contained in the two or more immunogenic peptides.Each CD8+ T cell epitope can interact with HLA-A1, HLA-A2, HLA-A3, HLA-A24, HLA-B7, HLA-B8, HLA-B27, HLAB44, HLA-B58 or HLA-B62, or any other HLA supertype known in the art. Any combination of immunogenic peptides containing such CD8+ T cell epitopes is possible. CD8+ T cell epitopes CD8+ T cell epitopes presented by cells infected with ssRNA viruses can be directly identified to identify CD8+ T cell epitopes for inclusion in vaccine formulations. This is an efficient and reasonable method that can be used alone or to confirm the utility of potential CD8+ T cell epitopes identified by MHC motif prediction methodologies. To perform this method, cells are infected with an ssRNA virus and maintained in culture for approximately 72 hours at approximately 37°C. After culture, the cells are harvested and washed. Next, the cells are lysed, for example by homogenization, and frozen / thawed in buffer containing 1% NP40. The lysate is clarified by centrifugation at 2000 rpm for 30 minutes to remove cell debris. MHC / peptide complexes were then isolated from the lysate by immunoaffinity chromatography using protein A / G beads (UltraLink Immobilized Protein A / G, Pierce, Rockford, IL) coated with W6 / 32 (a monoclonal antibody that recognizes pan MHC class I molecules). To coat the beads with antibody, the beads were washed with low pH buffer followed by a PBS rinse, incubated with 0.5 mg of antibody at room temperature for 2 hours, and washed three times to remove unbound antibody. For immunoaffinity chromatography, the coated beads were incubated with the lysate for 2 hours at room temperature with continuous shaking. The beads were then separated from the lysate by centrifugation at 1000 rpm for 5 minutes. The bound MHC complex was eluted from the beads by the addition of 0.1% trifluoroacetic acid (TFA), pH 1.5. The eluate is then heated at 85°C for 15 minutes to dissociate the bound peptides from the MHC molecules. After cooling to room temperature, the peptides are separated from the antibodies by centrifugation using, for example, a 3 kDa molecular mass cutoff membrane filter (Millipore). The filtrate is concentrated using vacuum centrifugation and reconstituted to a final volume of 100 μl. The purified peptide mixture is fractionated, for example, using a C-18 reverse-phase (RP) column (e.g., 4.6 mm diameter x 150 mm length) using offline HPLC. For this step, mobile phase A can be 2% acetonitrile (CAN) and 0.1% formic acid (FA) in water, while mobile phase B can be 0.1% FA and 90% CAN in water. The peptide-containing fraction is then eluted from the column, vacuum-dried, and analyzed by mass spectrometry to identify the sequences of the fractions. The obtained spectral data can then be searched against the entire protein database for ssRNA viruses to identify peptide sequences related to ssRNA viruses. Synthetic peptides can then be prepared from the identified sequences and subjected to mass spectrometry to confirm their identity to the peptides in the peptide-containing fractions. In this method, any cell type can be infected with any type of ssRNA virus. The ssRNA viruses are described in detail below. The cells can be any antigen-presenting cell. They can be hepatoma cells such as HepG2 cells, EBV-transformed lymphoblastoid B cells such as JY cells, or lymphoblasts such as T2 cells. Direct identification of CD8+ T cell epitopes presented by ssRNA virus-infected cells is advantageous compared to MHC motif prediction methodologies. The immune epitope database (IEDB; http: / / www.iedb.org) was generated by motif prediction methods, rather than functional methods, and includes a number of predicted HLA-specific ssRNA virus T cell epitopes, including some shared epitopes with high MHC binding scores and limited CTL characteristics. As both dominant and subdominant epitopes can be presented by ssRNA virus-infected cells, it is difficult to sort out the dominance hierarchy of naturally presented epitopes using the database. Thus, it is unclear from a single immune epitope database which of the listed epitopes can be expected to efficiently induce a CD8+ T cell response when included in a vaccine composition.The direct identification methods established above provide a mechanism for confirming the usefulness of epitopes. Vaccine composition based on epitopes presented by cells infected with ssRNA viruses is superior to vaccines based on viral protein subunits or predicted epitope motifs. Protein processing by the immune system tends to alter native viral epitopes. Basing vaccine composition on peptides demonstrated to be presented by infected cells eliminates this source of uncertainty, as the peptides have already undergone protein processing. CD4+ T cell epitopes As set forth above, the vaccine composition of the invention may contain immunogenic peptides containing CD4+ T cell epitopes. The vaccine composition may contain two or more, such as three or more, four or more, five or more, ten or more, fifteen or more or twenty or more immunogenic peptides containing CD4+ T cell epitopes. CD4+ T cell epitopes are peptides capable of (i) presentation by MHC class II molecules and (ii) recognition by the T cell receptor (TCR) present on CD4+ T cells. Preferably, recognition by the TCR results in activation of CD4+ T cells. Activation of CD4+ T cells may result in increased proliferation and / or cytokine production. CD4+ T cell epitopes can be CD4+ T cell epitopes of ssRNA viruses. That is, CD4+ T cell epitopes can be peptides expressed by one or more ssRNA viruses (such as Influenza A virus, Dengue virus, Zika virus, Ebola virus or Marburg) and which is capable of (i) presentation by MHC class II molecules and (ii) recognition by the T cell receptor (TCR) present on CD4+ T cells. Such peptides are known in the art. CD4+ T cell epitopes can be CD4+ T cell epitopes other than ssRNA virus CD4+ T cell epitopes. For example, CD4+ T cells can be expressed by organisms other than ssRNA viruses. CD4+ T cell epitopes, for example, can be expressed by Clostridium tetani. For example, CD4+ T cell epitopes can be derived from tetanus toxin. The CD4+ T cell epitope may be a CD4+ T cell epitope that reacts with all HLA class II types, i.e., a so-called “indiscriminate” epitope. The inclusion of an indiscriminate epitope in a vaccine composition may enhance the ability of the vaccine composition to induce an immune response to an immunogenic peptide containing a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least a portion of the genome of a ssRNA virus in the sense opposite to a positive sense RNA capable of translation. The CD4+ T cell epitope, for example, may include the sequence FKLQTMVKLFNRIKNNVA (SEQ ID NO: 54) and / or the sequence LQTMVKLFNRIKNNVAGGC (SEQ ID NO: 55). SEQ ID NOs 54 and 55 are indiscriminate epitopes derived from tetanus toxin. The peptide containing the CD4+ T cell epitope may be a peptide different from the immunogenic peptide containing the CD8+ T cell epitope of the polypeptide encoded by the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the positive sense RNA capable of translation. The CD4+ T cell epitope, for example, may be contained in another peptide in the vaccine composition, namely in a peptide that does not contain the CD8+ T cell epitope of the polypeptide encoded by the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the positive sense RNA capable of translation. As mentioned above, the other peptide may contain one or more CD8+ T cell epitopes and / or one or more B cell epitopes as well as CD4+ T cell epitopes. The peptide containing the CD4+ T cell epitope may be the same peptide as the immunogenic peptide containing the CD8+ T cell epitope from the polypeptide encoded by the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive-sense RNA. That is, the immunogenic peptide containing the CD8+ T cell epitope from the polypeptide encoded by the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to the translation-capable positive-sense RNA may further contain the CD4+ T cell epitope. If a peptide containing a CD4+ T cell epitope also contains a CD8+ T cell epitope (such as a CD8+ T cell epitope from a polypeptide encoded by an ORF encoded by at least part of the genome of a ssRNA virus in the sense opposite to a positive sense RNA capable of translation), the CD8+ epitope can be nested within the CD4+ T cell epitope. CD4+ T cell epitopes are typically longer than CD8+ T cell epitopes. Therefore, extending one or both termini of a CD8+ T cell epitope can result in a longer CD4+ T cell epitope whose sequence still contains the CD8+ T cell epitope. Therefore, CD4+ T cell epitopes may contain CD8+ T cell epitopes, such as CD8+ T cell epitopes of polypeptides encoded by ORFs encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a translationally capable positive sense RNA (e.g., epitopes designated in SEQ ID NO: 5 to 41), extended at the N-terminus or C-terminus.CD8+ T cell epitopes can be extended by 1, 2, 3, 4, or 5 amino acids at their N terminus. CD8+ T cell epitopes can be extended by 1, 2, 3, 4, or 5 amino acids at their C terminus. Preferably, CD8+ T cell epitopes are extended by 3 amino acids at their N terminus, and 3 amino acids at their C terminus. However, CD8+ T cell epitopes do not need to be extended by the same number of amino acids at each terminus. CD8+ T cell epitopes nested within CD4+ T cell epitopes may be capable of generating a strong CTL response. Extended peptides (CD4+ T cell epitopes) may be capable of inducing T helper-mediated cytokine responses. Thus, inclusion of viral ssRNA peptides containing CD8+ T cell epitopes and CD4+ T cell epitopes in a vaccine composition may enable the vaccine composition to induce both cytotoxic and helper T cell responses. B cell epitopes The vaccine composition of the invention may contain immunogenic peptides containing B cell epitopes. The vaccine composition may contain two or more, such as three or more, four or more, five or more, ten or more, fifteen or more or twenty or more peptides containing B cell epitopes. B cell epitopes are peptides capable of being recognized by the B cell receptor (BCR) present on B cells. Preferably, recognition by BCR results in activation and / or maturation of B cells. B cell activation can lead to increased proliferation, and / or antibody production. B cell epitopes can be ssRNA B cell epitopes. That is, B cell epitopes can be peptides expressed by one or more ssRNA viruses and capable of being recognized by the B cell receptor (BCR) present on B cells. Such peptides are known in the art. B cell epitopes can be linear epitopes, defined by the primary amino acid sequence of a specific region of the ssRNA viral protein. Alternatively, epitopes can be conformational epitopes, defined by the conformational structure of the native ssRNA viral protein. In this case, the epitope can be continuous (i.e., the components that interact with the antibody are located next to each other sequentially on the protein) or discontinuous (i.e., the components that interact with the antibody are located on different parts of the protein, adjacent to each other in the folded native protein structure). Typically, B cell epitopes are about 5 to 20 amino acids long, such as 6 to 19, 7 to 18, 8 to 17, 9 to 16, 10 to 15, 11 to 14 or 12 to 13 amino acids long. Methods for identifying B cell epitopes are also known in the art. For example, epitope mapping methods can be used to identify B cell epitopes. These methods include structural approaches, where known or modeled structures of proteins are used in algorithm-based approaches to predict surface epitopes, and functional approaches, where the binding of whole proteins, protein fragments, or peptides to antibodies can be quantified, for example, using an Enzyme-Linked Immunosorbent Assay (ELISA). Competition mapping, antigen modification, or protein fragmentation methods can also be used. Nanoparticles Any immunogenic peptide contained in the vaccine composition of the invention can be attached to the nanoparticle. Attachment to nanoparticles, for example gold nanoparticles, is beneficial. Attaching peptides to nanoparticles (such as gold nanoparticles) reduces or eliminates the need for virus-coupling or adjuvants in vaccine formulations. Nanoparticles can contain immune “danger signals” that help effectively induce an immune response to the peptide. Nanoparticles can induce the activation and maturation of dendritic cells (DCs), necessary for a robust immune response. Nanoparticles can contain nonself components that enhance the uptake of nanoparticles and thus peptides by cells, such as antigen-presenting cells. Attaching peptides to nanoparticles can therefore enhance the ability of antigen-presenting cells to stimulate virus-specific T and / or B cells. Attaching nanoparticles also facilitates delivery of vaccine formulations via subcutaneous, intradermal, transdermal, and oral / buccal routes, providing flexibility in administration. Nanoparticles are particles between 1 and 100 nanometers (nm) in size that can be used as substrates for immobilizing ligands. In the vaccine compositions of the invention, nanoparticles can have an average diameter of 1 to 100, 20 to 90, 30 to 80, 40 to 70, or 50 to 60 nm. Preferably, nanoparticles have an average diameter of 20 to 40 nm. An average diameter of 20 to 40 nm facilitates uptake of nanoparticles to the cytosol. The average diameter can be measured using techniques well known in the art such as transmission electron microscopy. Nanoparticles suitable for antigen delivery, such as immunogenic peptides, are known in the art. Methods for the production of such nanoparticles are also known. Nanoparticles, for example, can be polymeric nanoparticles, inorganic nanoparticles, liposomes, immune-stimulating complexes (ISCOMs), virus-like particles (VLPs), or self-assembling proteins. Preferred nanoparticles are calcium phosphate nanoparticles, silicon nanoparticles, or gold nanoparticles. Nanoparticles can be polymeric nanoparticles. Polymeric nanoparticles can contain one or more synthetic polymers, such as poly(d,l-lactide-co-glycolide) (PLG), poly(d,l-lactic-coglycolic acid) (PLGA), poly(g-glutamic acid) (g-PGA)m poly(ethylene glycol) (PEG), or polystyrene. Polymeric nanoparticles can contain one or more natural polymers such as polysaccharides, for example, pullulan, alginate, inulin, and chitosan. The use of polymeric nanoparticles can be advantageous due to the properties of the polymers that can be incorporated into the nanoparticles. For example, the natural and synthetic polymers described above can have good biocompatibility and biodegradability, non-toxic properties, and / or the ability to be manipulated into desired shapes and sizes. Polymeric nanoparticles can form hydrogen nanoparticles. Hydrogen nanoparticles are a type of nanosized hydrophilic three-dimensional polymer network. Hydrogen nanoparticles have favorable properties that include flexible network size, large surface area for multivalent conjugation, high water content, and high loading capacity for antigens. Polymers such as poly(L-lactic acid) (PLA), PLGA, PEG, and polysaccharides are particularly suitable for forming hydrogen nanoparticles. Nanoparticles can be inorganic nanoparticles. Typically, inorganic nanoparticles have a rigid structure and are not biodegradable. However, inorganic nanoparticles can be biodegradable. Inorganic nanoparticles can contain a shell in which antigens can be encapsulated. Inorganic nanoparticles can contain a core to which antigens can be covalently attached. The core can contain a metal. For example, the core can contain gold (Au), silver (Ag), or copper (Cu) atoms. The core can be composed of more than one type of atom. For example, the core can contain an alloy, such as an alloy of Au / Ag, Au / Cu, Au / Ag / Cu, Au / Pt, Au / Pd, or Au / Ag / Cu / Pd. The core can contain calcium phosphate (CaP). The core can contain a semiconductor material, such as cadmium selenide. Other examples of inorganic nanoparticles include carbon nanoparticles and silica-based nanoparticles. Carbon nanoparticles have good biocompatibility and can be synthesized into nanotubes and mesoporous spheres. Silica-based nanoparticles (SiNPs) are biocompatible and can be fabricated with fine-tuned structural parameters to suit their therapeutic applications. Nanoparticles can be silicon nanoparticles, such as elemental silicon nanoparticles. Nanoparticles can be mesoporous or have a honeycomb porous structure. Preferably, nanoparticles are elemental silicon particles that have a honeycomb core structure. Such nanoparticles are known in the art and provide tuned and controlled drug loading, targeting, and release that can be tailored to virtually any loading, administration route, target, or release profile. For example, such nanoparticles can enhance the bioavailability of their payload, and / or enhance intestinal permeability and absorption of orally administered active ingredients. Nanoparticles can have very high loading capacities due to their porous structure and large surface area. Nanoparticles can release their payload over days, weeks, or months, depending on their physical properties.Because silicon is a naturally occurring element in the human body, nanoparticles can elicit no immune response. This is advantageous for their in vivo safety. The SiNPs described above can be either biodegradable or non-biodegradable. Biodegradable SiNPs dissolve orthosilicic acid, a bioavailable form of silicon. Orthosilicic acid has been shown to benefit bone health, connective tissue, hair, and skin. Nanoparticles can be liposomes. Liposomes are typically formed from biodegradable, nontoxic phospholipids and contain a self-assembling phospholipid bilayer shell with an aqueous core. Liposomes can be unilamellar vesicles containing a single phospholipid bilayer, or multilamellar vesicles containing multiple concentric phospholipid shells separated by aqueous layers. Consequently, liposomes can be specifically designed to incorporate either hydrophilic molecules into the aqueous core or hydrophobic molecules within the phospholipid bilayer. Liposomes can encapsulate antigens within the core for delivery. Liposomes can incorporate viral envelope glycoproteins into the shell to form virosomes. A number of liposome-based products are established in the art and approved for use in humans. Nanoparticles can be immune-stimulatory complexes (ISCOMs). ISCOMs are cage-like particles typically formed from micelles containing colloidal saponins. ISCOMs can contain cholesterol, phospholipids (such as phosphatidylethanolamine or phosphatidylcholine), and saponins (such as Quil A from the Quillaia saponaria tree). ISCOMs have been traditionally used to adsorb viral envelope proteins, such as those of herpes simplex virus type 1, hepatitis B, or influenza viruses. Nanoparticles can be virus-like particles (VLPs). VLPs are self-assembling nonparticles lacking infectious nucleic acid, which are formed by the self-assembly of biocompatible capsid proteins. VLPs are typically around 20 to 150 nm, such as around 20 to 40 nm, 30 to 140 nm, 40 to 130 nm, 50 to 120 nm, 60 to 110 nm, 70 to 100 nm, or 80 to 90 nm in diameter. VLPs advantageously exploit the strengths of evolved viral structures, which are naturally optimized for interaction with the immune system. The naturally optimized size and repetitive structural arrangement of nonparticles mean that VLPs induce potent immune responses, even in the absence of adjuvants. Nanoparticles can be self-assembling proteins. For example, nanoparticles can contain ferritin. Ferritin is a protein that can self-assemble into nearly spherical structures measuring 10 nm. Nanoparticles can contain major vault proteins (MVPs). Ninety-six MVP units can self-assemble into barrel-shaped vault nanoparticles, approximately 40 nm wide and 70 nm long. The nanoparticles may be calcium phosphate (CaP) nanoparticles. CaP nanoparticles may contain a core comprising one or more (such as two or more, 10 or more, 20 or more, 50 or more, 100 or more, 200 or more, or 500 or more) CaP molecules. CaP nanoparticles and methods for producing them are known in the art. For example, a stable nano suspension of CAP nanoparticles may be produced by mixing inorganic salt solutions of calcium and phosphate in a predetermined ratio with constant mixing. CaP nanoparticles can have an average particle size of approximately 80 to approximately 100nm, such as approximately 82 to approximately 98nm, approximately 84 to approximately 96nm, approximately 86 to approximately 94nm, or approximately 88 to approximately 92nm. These particle sizes may yield better performance in terms of immune cell uptake and immune response than other, larger particle sizes. Particle size can be stable (i.e., not showing significant changes), for example, when measured over a period of 1 month, 2 months, 3 months, 6 months, 12 months, 18 months, 24 months, 36 months, or 48 months. CaP nanoparticles can be co-formulated with one or multiple antigens either adsorbed on the nanoparticle surface or co-precipitated with CaP during particle synthesis. For example, peptides, such as immunogenic peptides, can be attached to CaP nanoparticles by dissolving the peptide in DMSO (e.g. at a concentration of approximately 10 mg / ml), adding a suspension of CaP nanoparticles together with N-acetylglucosamine (GlcNAc) (e.g. at 0.093 mol / L and ultrapure water), and mixing at room temperature for a period of approximately 4 hours (e.g., 1 hour, 2 hours, 3 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours). The composition of the vaccine may contain approximately 0.15 to approximately 0.8%, such as 0.2 to approximately 0.75%, 0.25 to approximately 0.7%, 0.3 to approximately 0.6%, 0.35 to approximately 0.65%, 0.4 to approximately 0.6%, or 0.45 to approximately 0.55%, CaP nanoparticles. Preferably, the vaccine composition contains approximately 0.3% CaP nanoparticles. CaP nanoparticles have a high degree of biocompatibility due to their chemical similarity to human hard tissues such as bones and teeth. Therefore, CaP nanoparticles are superiorly non-toxic when used for therapeutic applications. CaP nanoparticles are safe for administration via intramuscular, subcutaneous, oral, or inhalation routes. CaP nanoparticles are also simple to synthesize commercially. Furthermore, CaP nanoparticles can be linked to slow-release antigens, which can enhance the induction of immune responses to peptides attached to the nanoparticles. CaP nanoparticles can be used as adjuvants and as drug delivery vehicles. The nanoparticles may be gold nanoparticles. Gold nanoparticles are known in the art and are described in particular in WO 2002 / 32404, WO 2006 / 037979, WO 2007 / 122388, WO 2007 / 015105 and WO 2013 / 034726. The gold nanoparticles attached to each peptide may be gold nanoparticles described in any one of WO 2002 / 32404, WO 2006 / 037979, WO 2007 / 122388, WO 2007 / 015105 and WO 2013 / 034726. Gold nanoparticles contain a core containing gold (Au) atoms. The core may further contain one or more Fe, Cu, or Gd atoms. The core may be formed from a gold alloy, such as Au / Fe, Au / Cu, Au / Gd, Au / Fe / Cu, Au / Fe / Gd, or Au / Fe / Cu / Gd. The total number of atoms in the core may be 100 to 500 atoms, such as 150 to 450, 200 to 400, or 250 to 350 atoms. Gold nanoparticles may have an average diameter of 1 to 100, 20 to 90, 30 to 80, 40 to 70, or 50 to 60 nm. Preferably, gold nanoparticles have an average diameter of 20 to 40 nm. Nanoparticles may contain surfaces coated with alpha-galactose and / or beta-GlcNHAc. For example, nanoparticles may contain surfaces passivated with alpha-galactose and / or beta-GlcNHAc. In this case, the nanoparticles, for example, may be nanoparticles containing a core including metal and / or semiconductor atoms. For example, the nanoparticles may be gold nanoparticles. Beta-GlcNHAc is a bacterial pathogen-associated molecular pattern (PAMP), capable of activating antigen-presenting cells. In this way, nanoparticles containing surfaces coated or passivated with Beta-GlcNHAc may stimulate an immune response nonspecifically. Attachment of immunogenic peptides to such nanoparticles may therefore enhance the immune response elicited by administration of the vaccine composition of the invention to an individual. One or more ligands other than peptides may be linked to the nanoparticle, which may be any of the types of nanoparticles described above. The ligands may form a corona, a layer or coating that partially or completely covers the surface of the core. The corona may be considered an organic layer that surrounds or partially surrounds the nanoparticle core. The corona may provide or participate in passivating the nanoparticle core. Thus, in certain cases the corona may be a coating layer sufficiently dense to stabilize the core. The corona may facilitate solubility, such as solubility in water, of the nanoparticles of the present invention. Nanoparticles may contain at least 10, at least 20, at least 30, at least 40, or at least 50 ligands. Ligands may include one or more peptides, protein domains, nucleic acid molecules, lipid moieties, carbohydrate moieties, anionic or cationic moieties, glycolipids, and / or glycoproteins. The carbohydrate moieties may be polysaccharides, oligosaccharides, or monosaccharide moieties (e.g., glucose). One or more ligands may be non-self-associated, which makes the nanoparticle more likely to be taken up by antigen-presenting cells due to their similarity to pathogenic components. For example, one or more ligands may contain a carbohydrate moiety (such as a bacterial carbohydrate moiety), a surfactant moiety, and / or a glutathione moiety. Examples of ligands include glucose, N-acetylglucosamine (GlcNAc), glutathione, 2'-thioethyl-β-D-glucopyranoside, and 2'-thioethyl-D-glucopyranoside. Preferred ligands include glycoconjugates, which form glyconanoparticles. Ligand binding to the core can be facilitated by a linker. The linker can contain a thiol group, an alkyl group, a glycol group, or a peptide group. For example, the linker can contain a C2C15 alkyl and / or a C2-C15 glycol. The linker can contain a sulfur-containing group, an amino-containing group, a phosphate-containing group, or an oxygen-containing group capable of covalent attachment to the core. Alternatively, the ligand can be linked directly to the core, for example, through a sulfur-containing group, an amino-containing group, a phosphate-containing group, or an oxygen-containing group contained within the ligand. Attachment to nanoparticles Immunogenic peptides can be attached N-terminally to nanoparticles. Typically, immunogenic peptides can be attached to the nanoparticle core, but attachment to the corona or ligand is also possible. Peptides can be attached directly to nanoparticles, for example by covalent binding of atoms in sulfur-containing groups, amino-containing groups, phosphate-containing groups or oxygen-containing groups in peptides to atoms in the nanoparticle or its core. Linkers can be used to attach peptides to nanoparticles. Linkers can contain sulfur-containing groups, amino-containing groups, phosphate-containing groups, or oxygen-containing groups capable of covalently attaching to atoms in the nucleus. For example, linkers can contain thiol groups, alkyl groups, glycol groups, or peptide groups. The linker may contain a peptide portion and a non-peptide portion. The peptide portion may include the sequence X1X2Z1, where X1 is an amino acid selected from A and G; X2 is an amino acid selected from A and G; and Z1 is an amino acid selected from Y and F. The peptide portion may include the sequence AAY or FLAAY. The peptide portion of the linker may be linked to the N-terminus of the peptide. The non-peptide portion of the linker may contain a C2-C15 alkyl and / or C2-C15 glycol, such as a thioethyl group or a thiopropyl group. The linker can be (i) HS-(CH2h-CONH-AAY; (ii) HS-(CH2)2CONH-LAAY; (iii) HS-(CH2)3-CONH-AAY; (iv) HS-(CH2)3-CONH- FLAAY; (v) HS-(CH2)io-(CH20CH2)7-CONH-AAY; and (vi) HS-(CH2)io-(CH20CH2 )7CONH-FLAAY. In this case, the thiol group of the non-peptide portion of the linker anchors the linker to the core. Other suitable linkers for attaching peptides to nanoparticles are known in the art, and can be readily identified and implemented by those skilled in the art. As described above, a vaccine composition may contain multiple immunogenic peptides. If a vaccine composition contains more than one immunogenic peptide, two or more (such as three or more, four or more, five or more, ten or more, or twenty or more) immunogenic peptides may be attached to the same nanoparticle. Two or more (such as three or more, four or more, five or more, ten or more, or twenty or more) immunogenic peptides may each be attached to a different nanoparticle. The nanoparticles to which the immunogenic peptides are attached may be the same type of nanoparticle. For example, each immunogenic peptide may be attached to a gold nanoparticle. Each immunogenic peptide may be attached to a CaP nanoparticle. The nanoparticles to which the immunogenic peptides are attached may be different types of nanoparticles.For example, one immunogenic peptide can be attached to a gold nanoparticle, and another immunogenic peptide can be attached to a CaP nanoparticle. Drugs, methods and therapeutic uses The invention provides a method for preventing or treating viral infections, including administering a vaccine composition of the invention to an individual infected with, or at risk of infection with, an ssRNA virus. The invention also provides a vaccine composition of the invention for use in a method for preventing or treating ssRNA virus infections in an individual. An individual, for example, can be a human being. An individual, for example, can be a pig, a horse, or a bird. ssRNA virus infections can be caused by zoonotic viruses. ssRNA virus infection could end this pandemic An ssRNA virus infection, for example, can be an orthomyxoinfection. An orthomyxoinfection can be an influenza virus infection. Influenza viruses can be influenza A, influenza B, and / or influenza C viruses. Influenza A viruses, for example, can be serotypes H1N1, H5N1, H7N9, H7N7, H2N2, or H3N2. Influenza viruses can be human influenza viruses, swine influenza viruses, equine influenza viruses, or avian influenza viruses. Influenza viruses can be pandemic influenza viruses or influenza viruses with pandemic potential. An ssRNA virus infection, for example, can be a flavivirus infection. A flavivirus infection, for example, can be a Zika virus infection, a Dengue virus infection, a West Nile virus infection, a Yellow Fever virus infection, a St. Louis encephalitis virus infection, a Japanese encephalitis virus infection, a Murray Valley encephalitis virus infection, a tick-borne encephalitis virus infection, a Kunjin encephalitis virus infection, a Rocio encephalitis virus infection, a Russian Spring Summer encephalitis virus infection, a Negeishi virus infection, a Kyasanur Forest infection, an Omsk Horagi Fever virus infection, a Powassan virus infection, a Louping Ill virus infection, a Rio Bravo virus infection, a Tyuleniy virus infection, a Ntaya virus infection, or a Modoc virus infection. A Zika virus infection, for example, can be an African Zika virus infection or an Asian Zika virus infection. A Dengue virus, for example, can be a DENV-1 infection, a DENV-2 infection, a DENV-3 infection, or a DENV-4 infection. An ssRNA virus infection, for example, can be a filovirus infection. A filovirus infection, for example, can be an Ebola virus infection or a Marburg virus infection. Ebola virus infections, for example, can be an infection with Zaire Ebola virus (ZEBOV), Sudan Ebola virus (SUDV), Reston Ebola virus (RESTV), Tai Forest Ebola virus (TAFV), or Bundibugyo Ebola virus (BDBV). A Marburg virus infection, for example, can be an infection with Marburg virus (MARV) or Ravn virus (RAVV). Vaccine compositions may be provided as pharmaceutical compositions. Pharmaceutical compositions preferably contain pharmaceutically acceptable carriers or diluents. Pharmaceutical compositions may be formulated using any suitable method. Cell formulations with pharmaceutically acceptable standard carriers and / or excipients may be made using routine pharmaceutical methods. The exact nature of the formulation will depend on several factors including the cells administered and the desired route of administration. Suitable types of formulations are fully described in Remington's Pharmaceutical Sciences, 19th edition, Mack Publishing Company, Eastern Pennsylvania, USA. Vaccine compositions or pharmaceutical compositions may be administered by any route. Suitable routes include, but are not limited to, intravenous, intramuscular, intraperitoneal, subcutaneous, intradermal, transdermal, and oral / buccal routes. The compositions may be prepared in conjunction with any physiologically acceptable carrier or diluent. Typically, the compositions are prepared as aqueous suspensions of peptides and / or peptide-linked nanoparticles. The peptides and / or peptide-linked nanoparticles may be mixed with pharmaceutically acceptable excipients compatible with the active ingredient. Suitable excipients include, for example, water, saline, dextrose, glycerol, the like, and combinations thereof. In addition, if desired, the pharmaceutical composition may contain small amounts of excipients such as wetting or emulsifying agents, and / or pH buffering agents. Peptides or peptide-linked nanoparticles are administered in a manner consistent with the dosage formulation in amounts that will be therapeutically effective. The quantity administered depends on the subject being treated, the disease being treated, and the capacity of the subject's immune system. The exact number of nanoparticles to be administered can be at the discretion of the physician and can be specific to each individual patient. Any suitable amount of peptide or peptide-linked nanoparticles may be administered to the subject. For example, at least, or about, 0.2 x 106, 0.25 x 106, 0.5 x 106, 1.5 x 106, 4.0 x 106, or 5.0 x 106 of peptide or peptide-linked nanoparticles per kg of patient may be administered. For example, at least, or about, 105, 106, 107, 108, or 109 of peptide or peptide-linked nanoparticles may be administered. As a guide, the amount of peptide or peptide-linked nanoparticles administered may be from 105 to 109, preferably from 106 to 108. Method The invention provides a method for identifying immunogenic peptides comprising CD8+ T cell epitopes from the open reading frame of an ORF encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a translation-competent positive sense RNA by: (a) identifying the ORF encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to a translation-competent positive sense RNA; (b) predicting the sequence of the polypeptide encoded by the ORF; and (c) assessing whether the peptide that binds to an MHC class I molecule includes a sequence contained in the predicted sequence, thereby identifying the immunogenic peptide containing the CD8+ T cell epitope. The immunogenic peptide can be any of the immunogenic peptides discussed above. The CD8+ T cell epitope can be any of the CD8+ T cell epitopes discussed above. The ssRNA virus can be any of the ssRNA viruses discussed above. Preferably, the ssRNA virus is Influenza A virus. The ORF can be any of the ORFs discussed above. For example, it could be the ORF NEG8. In some instances, the ORF contains a stop codon. In this case, the predicted sequence is predicted based on the ORF being mutated to a codon encoding an amino acid, and the peptide includes a sequence containing a portion of the predicted sequence, C-terminal to the mutated codon. Methods for identifying ORFs encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a translation-competent positive-sense RNA are well known in the art. For example, an ORF can be identified by analyzing the sequence of the ssRNA virus genome in the sense opposite to a translation-competent positive-sense RNA. As defined above, an ORF is a continuous stretch of codons containing a start codon and a stop codon. If the sequence of the ssRNA virus genome in the sense opposite to a translation-competent positive-sense RNA includes such a stretch of codons, it may contain an ORF. Methods for predicting the polypeptide sequence encoded by an ORF are routine in the field. For example, with knowledge of the genetic code, an expert can easily determine the amino acid sequence of a polypeptide from the codons contained within the ORF. Methods for assessing whether peptides that bind to MHC class I molecules include sequences contained in the predicted sequence are also known. For example, peptides that bind to MHC class I molecules can be determined as described in the section “CD8+ T cell epitopes” above. Briefly, cells infected with an ssRNA virus are cultured, harvested, and washed. The cells are lysed, and MHC / peptide complexes are then isolated from the lysate by immunoaffinity chromatography. The MHC complex obtained by immunoaffinity chromatography is heated to dissociate the bound peptides from the MHC molecules. The peptide mixture is purified and analyzed by mass spectrometry to identify the peptide sequences. The peptide sequences can then be compared with the predicted sequences to determine whether or not the peptides include sequences contained in the predicted sequences.In other words, the predicted sequence can be compared with sequences known or recently shown to bind MHC class I molecules. If, for example, there is identity between the predicted sequence and the peptide over some (e.g. 10%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%, 95%, 97%, 98% or 99%) or the entire length of the peptide, the peptide may include sequences contained in the predicted sequence. There may be, for example, at least 50% identity (such as at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98% or at least 99% identity) between the peptide and the predicted sequence over some or all of the length of the peptide, based on amino acid identity. Such an immunogenic peptide containing a CD8+ T cell epitope is expected to be capable of inducing a CD8+ T cell response. The method of the invention may further include one or more steps that help to confirm whether or not this is the case. For example, the method may further include (d) contacting CD8+ T cells obtained from an individual infected with, or previously infected with, an ssRNA virus with the peptide; and (e) measuring the in vitro immune response to the peptide. In other words, CD8+ T cells obtained from an individual infected with, or previously infected with, an ssRNA virus are stimulated with the immunogenic peptide to determine whether the CD8+ T cell population contains CD8+ T cells specific for the epitope contained in the immunogenic peptide. Methods for measuring the in vitro immune response are well known in the art. For example, CD8+ T cell proliferation may be measured.IFNy production can be measured, for example by spiking IFNy into culture supernatants or by investigating. Intracellular IFNγ using flow cytometry. Expression of CD107a, a marker of degranulation, can be measured using flow cytometry. Immunogenic peptides The invention provides immunogenic peptides comprising CD4+ T cell epitopes or B cell epitopes from polypeptides encoded by an open reading frame (ORF) encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation. CD4+ T cell epitopes are peptides capable of (i) presentation by MHC class II molecules and (ii) recognition by the T cell receptor (TCR) present on CD4+ T cells. Preferably, recognition by the TCR results in CD4+ T cell activation. Activation of CD4+ T cells can lead to increased proliferation and / or cytokine production. B cell epitopes are peptides that can be recognized by the B cell receptor (BCR) present on B cells. Preferably, recognition by the BCR results in activation and / or maturation of B cells. B cell activation can lead to increased proliferation, and / or antibody production. Immunogenic peptides may be used in vaccine compositions. Any of the aspects described above in relation to vaccine compositions containing immunogenic peptides containing CD8+ T cell epitopes or B cell epitopes from polypeptides encoded by ORFs encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to positive sense RNA capable of translation may apply equally to vaccine compositions containing immunogenic peptides containing CD4+ T cell epitopes or B cell epitopes from polypeptides encoded by ORFs encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to positive sense RNA capable of translation. Administration of a vaccine composition containing immunogenic peptides may induce a protective immune response against an ssRNA virus. For example, administration of the vaccine composition may induce a CD4+ T cell response against an ssRNA virus.Administration of the vaccine composition can induce a B cell response against ssRNA viruses. In this way, humoral immunity against ssRNA viruses can be induced. Immunogenic peptides can be used in assays to diagnose infection by ssRNA viruses. For example, immunogenic peptides can be used to detect antibodies to ssRNA viruses, such as antibodies specific for B cell epitopes contained in immunogenic peptides. Immunogenic peptides can be used to detect B cells specific to ssRNA viruses, such as B cells whose B cell receptors are specific for B cell epitopes contained in immunogenic peptides. Immunogenic peptides can be used to detect CD4+ T cells specific to ssRNA viruses, such as CD4+ T cells specific for CD4+ T cell epitopes contained in immunogenic peptides. Identifying potential pandemics Traditionally, influenza A virus pandemics have been associated with global changes in the HA serotype of the virus. However, inventors have noted that certain influenza A virus outbreaks are not associated with changes in the HA serotype, but rather with changes in the codon length of the ORF encoded by at least a portion of the influenza A virus genome in the sense as opposed to the translationally capable positive-sense RNA. Thus, the present invention provides a method for determining the pandemic potential of an Influenza A virus, the method comprising the steps of: (i) identifying a first ORF encoded by at least a portion of segment 8 of the genome of an Influenza A virus in the opposite sense of translation-capable positive sense RNA; (ii) determining the number of codons contained in the first ORF; and (iii) comparing the number of codons contained in the first ORF with the number of codons contained in a second ORF encoded by at least a portion of segment 8 of the genome of a known pandemic Influenza A virus in the opposite sense of translation-capable positive sense RNA, wherein the difference in the number of codons in the first ORF compared to the second ORF is indicative of the pandemic potential. In the context of the invention, pandemic potential refers to the ability of an influenza A virus to cause an influenza pandemic. An influenza pandemic occurs when a new influenza virus emerges and spreads worldwide. The first ORF can contain any nucleotide sequence. The first ORF can encode any polypeptide sequence. The second ORF can contain any nucleotide sequence. The second ORF can encode any polypeptide sequence. The first ORF can be of any length, i.e. contain any number of codons. The second ORF can be of any length, i.e. contain any number of codons. An example of an ORF length is the one discussed above. The first and second ORFs can differ in length by any number of codons. For example, a difference of one or more, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 60 or more, 70 or more, 75 or more, 80 or more, 90 or more, or 100 or more codons may be an indication of pandemic potential. It is understood that different applications of the disclosed products and methods may be tailored to specific needs in the art. It is also understood that the terminology used herein is for the purpose of describing specific embodiments of the invention only, and is not intended to be limiting. In addition, as used in this specification and the accompanying claims, the singular form of a (“a”, “an”, and “the”) includes plural references unless expressly stated otherwise. Thus, for example, a reference to “a peptide” includes peptides”, a reference to “a nanoparticle” includes two or more such nanoparticles, and the like. All publications, patents and patent applications cited herein, whether above or infra, are incorporated by reference in their entirety. The following examples illustrate the invention. Example 1 - Identification of CD8+ T cell epitopes Cell lines HepG2 hepatoma cells were obtained from ATCC and maintained in DMEM:F12 (Mediatech, Manassas, VA). The culture medium was supplemented with 10% fetal bovine serum, L-glutamine (300 mg / mL), non-essential amino acids (1x concentration), 0.5 mM sodium pyruvate, penicillin and streptomycin (1x concentration, supplements purchased from Mediatech) [complete medium]. The cells were maintained at 37°C in a humidified incubator with 5% CO2. Sample preparation for MHC peptide analysis HepG2 cells were grown to approximately 1E9 cells. These cells were then infected with influenza A virus strain PR8. After a 1-hour pulse, the virus was washed off, and the cells were incubated for 72 hours at 37°C. At this point, the cells were harvested and processed for MHC peptide analysis. Isolation, purification and fractionation of MHC class I bound peptides Infected cells were lysed by homogenization and frozen / thawed in buffer containing 1.0% NP40. The lysate was clarified by centrifugation at 2000 rpm for 30 min to remove cell debris. MHC / peptide complexes were isolated by immunoaffinity chromatography using W6 / 32 antibody (a monoclonal antibody recognizing pan MHC class I molecules) coated with protein A / G beads (UltraLink Immobilized Protein A / G, Pierce, Rockford, IL). A total of 400 μl of protein A / G beads were washed with low pH buffer followed by a PBS rinse. The beads were then incubated with 0.5 mg of antibody at room temperature for 2 h. The labeled beads were washed three times to remove unbound antibody, and the antibody-coated beads were added to the prepared cell lysate. After two hours of incubation at room temperature with continuous shaking, the beads were separated from the lysate by centrifuging at 1000 rpm for 5 minutes.The bound MHC complex was eluted from the beads by the addition of 0.1% trifluoroacetic acid (TFA), pH 1.5. Next, the eluate was heated at 85°C for 15 min to dissociate the bound peptides from the MHC molecules. After the solution was cooled to room temperature, the peptides were separated from the antibodies by centrifugation through an Amicon Ultra 3 kDa molecular mass cutoff membrane filter (Millipore). The filtrate was concentrated using vacuum centrifugation and reconstituted to a final volume of 100 μL. The purified peptide mixture was fractionated using a C-18 reverse-phase (RP) column (4.6 mm diameter x 150 mm length) using an offline HPLC ultimate 3000 (Dionex, Sunnyvale, CA). Mobile phase A was 2% acetonitrile (ACN) and 0.1% formic acid (FA) in water, while mobile phase B was 0.1% FA and 90% ACN in water. Peptides were then eluted from the column with an 80-minute linear gradient from 5 to 80% buffer B at a flow rate of 200 μL / minute.A total of 35 fractions were collected and dried to 6 μL in vacuum for LC / MS / MS analysis. Mass spectrometry analysis Mass spectrometry experiments were performed using an LTQ (Thermo) and an Orbitrap instrument interfaced with a nano ultimate HPLC (Dionex). Peptide fractions purified by reverse-phase HPLC were individually injected into the LC-MS / MS system to identify peptide sequences. As part of an on-line sample cleanup step, peptides were first concentrated using a 300 μm ID x 5mm C18 reverse-phase trap column (Dionex, Sunnyvale CA) and then separated using a 75 μm ID x 15 cm C18 reverse-phase analytical column (Dionex, Sunnyvale CA), equilibrated in 4% ACN / 0.1% FA at a flow rate of 250 nL / min. Mobile phase A was 2% ACN and 0.1% FA in water, while mobile phase B was 0.1% FA and 90% ACN in water. Peptides were separated with a gradient of 4% to 50% B in 60 minutes and 50% to 80% in 90 minutes and eluted directly into the mass spectrometer.The mass range in MS mode was 350 Da to 1500 Da and in MS / MS mode was set as 100 Da to 1500 Da. Peptides were analyzed using the Data-dependent method. The obtained spectral data were searched against the influenza A protein database using Proteome Discoverer (Thermo) to interpret the data and obtain peptide sequences. The sequences of the bound peptides were shown in Fig. MHC class I in PR8-infected cells was included in the database. Identification of MHC peptides in the NEG8 ORF The database of peptides found to bind to MHC class I in PR8-infected cells was searched against the polypeptide sequence (SEQ ID NO: 2; MLFVQSYFPLFLV CVSLLQSAILSLQTFDLAVLAIFRFCFGVSGGPPFSLLLLQANLCRFLETRTVLSFHSSPPMRT PIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRSKITLKFAFNMMFFSMIAWSILMQ RGPSTFCLGISMNQFLDNSSIVMSVMYREAGVETMVILSASSDSSFRIFSTICFPTWVAALMSR PRVLPLPLRDL) encoded by ORF NEG8. The NEG8 polypeptide was found to contain a number of peptides that bind to MHC class I in cells infected with Influenza A virus. Table 3 below shows the peptides encoded by ORF NEG8 that bind to MHC class I in cells infected with Influenza A virus. Table 3 SEQ ID NO: Protein Sequence ID Modification Confidence XCorr m / z [Da] 5 WSILMQRGP NEG8 High 2.14 544.29120 6 EAGVETMVIL NEG8 High 1.95 531.27979 7 IAPSSVKALS NEG8 High 1.88 486.79718 8 PMRTPIAFL NEG8 Medium 1.74 349.20383 9 ISMNQFLDNS NEG8 M3(Oxidation) Medium 1.67 592.77045 10 LMQRGPSTF NEG8 Medium 1.66 518.77515 11 FHSSPPMRTP NEG8 Medium 1.65 386.18805 12 KITLKFAFNM M NEG8 M10 (Oxidation); M11 (Oxidation) Medium 1.60 688.34729 13 LVCVSLLQSAI LSL NEG8 Medium 1.48 729.93231 Example 2 The identities of five peptides encoded by the NEG8 ORF and found to bind to MHC class I in Influenza A virus-infected cells were confirmed using mass spectrometric analysis of 5 synthetic peptides. The five peptides shown in Table 3 were synthesized and subjected to LC-MS / MS analysis under identical experimental conditions as described above. The spectra obtained for each peptide isolated from Influenza A virus-infected cells were compared with the spectra obtained for its 10 synthetic analogues to confirm the sequence of each peptide. The results are shown in Table 4 and Figures 1 to 3. Table 4 Sequence of Origin Motif Virus Origin Cell type Confirmation EAGVET MVIL Polypeptide A2 NEG8, NSP [Influenza A virus (A / Moscow / 343 / 2003(H3N2))], NSP [Influenza A virus (A / Moscow / 328 / 2003(H3N2))] Cells Infected with Flux PSIA Virus ALS infected with influenza virus No. NEG8, NSP [Influenza A virus (A / Moscow / 343 / 2003(H3N2))], NSP [Influenza A virus (A / Moscow / 328 / 2003(H3N2))] Cells infected with influenza virus Yes IAPSSVK ALS Transmembrane protein AEG8, Influenza A2 Nvirus [NSP ASP (A / Moscow / 343 / 2003(H3N2))], NSP [Influenza A virus (A / Moscow / 328 / 2003(H3N2))] Flu virus infected cells Yes PMRTPIA A2 / 24 protein NEG8, Infected cells No FL transmembrane NSP [Influenza A virus (A / Moscow / 343 / 2003(H3N2))], NSP [Influenza A virus (A / Moscow / 328 / 2003(H3N2))] influenza virus LMQRGP STF A24 transmembrane protein NEG8, NSP [Moscow Influenza A / A / 343 virus / 2003(H3N2))], NSP [Influenza A virus (A / Moscow / 328 / 2003(H3N2))] Cell infected with influenza virus Ya Figures 1 to 3 compare the mass spectra obtained for synthetic peptides with those obtained for peptides isolated from infected cells. Some common ions are circled in each spectrum to illustrate the identity of the peptides isolated from infected cells with their synthetic counterparts. The data confirm that the peptides IAPSSVKALS, LMQRGPSTF, and KITLKFAFNMM encoded by the NEG8 ORF are those actually found in cells infected with Influenza A virus. Example 3 The polypeptide sequence encoded by ORF NEG8 (SEQ ID NO: 2; MLFVQSYFPLFLVCVSLLQSAILSLQTFDLAVLAIFRFCFGVSGGPPFSLLLLQANLCRFLETR TVLSFHSSPPMRTPIAFLTSSIVCPGKEGNGEISPTIAPSSVKALSNTMVSSRSKITLKFAFNM MFFSMIAWSILMQRGPSTFCLGISMNQFLDNSSIVMSVMYREAGVETMVILSASSDSSFRIFST ICFPTWVAALMSRPRVLPLPLRDL) was used to search a dataset of T cell epitopes derived from influenza virus-infected cells. The NEG8 peptide described in Examples 1 and 2 was also identified using this search. The goal of performing the search was to determine whether any NEG8 peptide or sequence within the polypeptide encoded by the NEG8 ORF was shared with any other Influenza A virus protein.Table 5 presents T cell epitopes derived from Influenza A virus proteins other than NEG8 that are also contained in one or more of the NEG8 peptides identified in Examples 1 and 2 or polypeptides encoded by the NEG8 ORF. From these, a number of NEG8 peptides thought to bind to MHC in Influenza A virus-infected cells can be identified based on confidence levels, XCorr, and fragment mass spectra performance. Table 5: NEG8 peptides shared with other flu proteins Sekuens Protein Motif Galur Flu multipel data DNSSIVI SV NSP H3N2 (manusia) 1.40 467.24 multipel compulan data IAWSILIQ NS1 H1N1 (manusia) H7N7 (burung) H2N2 (manusia) 1.22 472.28 multipel compulan data IVMSVM YR NSP A3 H3N2 (manusia) 1.17 507.75 Multi-plume data FLICVSP LQL NSP A2 / 24 H3N2 (manusia) 1.76 566.81 A2:24 A24:13 VLS0670 ​​GGLPFS LLL NS1 H1N1 (manusia) 1.82 458.78 VLS0670 ​​LFLICVS NSP A24 H3N2 1.74 510.81 A2:18 VLS0670 LL (manusia) A24:21 SPLQLAI LSL NSP B7 H3N2 (manusia) 1,90 527,82 B7:22 VLS0670 ​​WSILMQ RGP NSP H3N2 (manusia) 2,14 544,29 VLS0670 ​​IFRFCFG GSG PB2 polymerase H7N7 (burung) H1N1 1.49 545.76 VLS3056 VAASMF RP NSP H3N2 1.45 447.74 459.76 VLS3056 FSVMFL SM NS1 H7N7 (burung) 1.17 489.22 VLS3056 VLS3063 SVKALS SI HA A2 / 24 H7N7 (burung) H1N1 (manusia) 1.15 402.74 VLS3056 VLS3063 ALMSRP RV NSP A2 H3N2 (manusia) 1.24 465.27 VLS3056 EGNGEI SPT NSP H3N2 H2N2 H1N1 (manusia) 1.02 452.21 VLS3056 AFNMMF FS NSP H3N2 (manusia) 1.06 505.69 VLS3056 PAISRFC F HA A24 H1N1 (manusia) 1.48 470.73 VLS3056 AFSVMF LSM NSP A24 H7N7 (burung) 1.36 516.74 A24:7 VLS3056 LIQRGPA TFCL Protein matrices A2 / 24 H2N2 H1N1 (manusia) 1.36 609.83 VLS3063 AILSLQT FD NSP A24 H3N2 (human) 1.10 504.26 A24:2 VLS3063 ALSSIRV SS PB2 polymerase A2 B7 H1N1 (human) 1.10 460.25 A2:16 B7:7 VLS3063 FSMMLL SMI PB1 polymerase H1N1 (human) 1.00 560.76 VLS3063 SPPMRT PT Protein PA-X H1N1 (human) 1.13 451.72 VLS3063 LIVLAIYR FC NSP A24 H3N2 (human) 1.11 605.86 VLS3063 SLRTFDL A NSP A2 H3N2 (human) 1.09 461.74 VLS3063 MLFVQS YFQ NSP H3N2 (human) 1.05 581.79 VLS3063 Example 4 Stimulation of CTL responses in vitro Peripheral blood mononuclear cells (PBMCs) from healthy (naive) human donors were stimulated with a peptide encoded by the NEG8 ORF and shown to bind to MHC class I in Influenza A virus-infected cells, (in a cytokine cocktail to induce antigen-specific CTL responses. PBMCs were stimulated with free aggregated peptide (FP) for a total of four stimulations at varying peptide loads. These stimulated PBMCs were then assayed by coculture with uninfected, infected, or peptide-loaded targets for antigen-specific responses. TAP-deficient (T2) cells were used for peptide loading, and blank T2 cells served as controls. Activated PBMCs were assayed for gamma interferon (IFN-γ) and the degranulation marker CD107a by flow cytometry. Dextramer research Fluorescently labeled dextramer reagents are used to detect antigen-specific T cells in cell suspensions and solid tissue samples. MHC dextramer is added to PBMCs or splenocytes. An optimal amount of anti-CD8 antibody conjugated to the relevant fluorochrome is then added. Other antibodies (e.g., anti-CD3 or anti-CD4 antibodies) conjugated to other relevant fluorochromes can also be added at this step. The cells are then analyzed using a flow cytometer. In vivo CTL research Transgenic mice (5-6 mice per group) were immunized with free synthetic peptide or nanoparticle-peptide conjugates mixed with and without montanide-51 adjuvant three times at 2-week intervals by subcutaneous and intradermal administration routes. Spleens and lymph node drainage were collected 7 days after the final boost for CTL analysis. Single-cell suspensions were prepared from lymphoid organs and cells were stimulated with antigen peptides in culture for 7 days. Reactivated T cells were assayed for epitope-specific CTL responses using NEG8 peptide-loaded T2 cells and HepG2 cells infected with Influenza A virus as targets in the following assays: IFN-γ and granzyme-B production by ELISpot; cytokine secretion by MAGPIX assay; CD107a co-expression by flow cytometry. Adoptive transfer trial Adoptive transfer experiments were conducted to investigate whether peptide-specific CTLs produced in transgenic mice have cytotoxic effects against Influenza A virus-infected cells in vivo in tan SCID mice. Infected liver tumor suspensions were injected s.c. or iv. into tan SCID mice, followed by single or multiple adoptive transfers of peptide-specific CTLs produced in A2 transgenic mice against peptide constructs or peptide-nanoparticle constructs. Appropriate controls were used. The survival of the mice was observed. Example 5 Major ORF length changes over time The international influenza database was used to obtain sequences of segment 8 for a number of human influenza A viruses. Negative sense genomic sequences were analyzed to determine the length of the The NEG8 ORF in each virus. The ORF length is calculated by determining the position of the first stop codon in the negative-sense sequence. For example, a virus with a NEG8 sequence with a stop codon at position 94 has an ORF with a length of 93 codons. Figure 5 shows the number of Influenza A viruses (Y-axis) analyzed by year and month of collection (X-axis). The color coding indicates the length of the ORF present in the viruses collected at each time point. The data show that from 1918 to 1947 the main ORF length in human Influenza A viruses was 167 codons. From 1947 to 2009, the 216-codon ORF was the main one. Since the 2009 flu pandemic, the main ORF has been 85 codons long. ORF length by serotype The relationship between serotype and ORF length was also considered. Figure 6 shows ORF identity by year. The color code indicates the serotype of each virus plotted. Between 1918 (Spanish flu - green) and 1957 (Asian flu - blue), the 167-codon ORF was predominantly present in serotype H1N1 viruses. The 167-codon ORF was predominantly present in serotype H2N2 viruses until 1968 (Hong Kong flu - yellow), at which point the 167-codon ORF was predominantly present in serotype H3N2 viruses. The 167-codon ORF was seen again in serotype H1N1 viruses in 1976 as the Russian flu (green). The results are confirmed in Figure 7, which plots the 167-codon ORF identity by year, with serotype indicated by the color code. These data indicate that ORF length can be maintained in the Influenza A virus population despite changes in serotype and associated constellation effects. ORF length by species Figure 8 shows the prevalent ORF lengths in different species of Influenza A virus. A 93-codon ORF (or less commonly, a 135-codon ORF) has been observed in avian, avian-like swine, and equine influenza A viruses. A 140-codon ORF and a 167-codon ORF have been observed in swine Influenza A viruses. In equine influenza A viruses, the NEG8 ORF is 93 codons long almost 100% of the time. Equine Influenza A viruses never contain human ORFs of 85, 167, or 216 codons.

Claims

1. A vaccine composition containing an immunogenic peptide containing a CD8+ T cell epitope from a polypeptide encoded by an open reading frame (ORF) encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation.

2. The vaccine composition of claim 1, comprising two or more immunogenic peptides.

3. The vaccine composition of claim 2, comprising two or more immunogenic peptides each containing different CD8+ T cell epitopes from polypeptides encoded by an open reading frame (ORF) encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to the positive sense RNA capable of translation.

4. A vaccine composition of any one of the foregoing claims, comprising at least one immunogenic peptide that interacts with at least two different HLA supertypes.

5. A vaccine composition of any of the foregoing claims, wherein the polypeptide enhances the fitness of an ssRNA virus in humans.

6. A vaccine composition of any one of the foregoing claims, wherein the ssRNA virus is a negative-sense ssRNA virus and the ORF is negative-sense.

7. The vaccine composition of claim 6, wherein the negative sense ssRNA virus is an Orthomyxovirus.

8. The vaccine composition of claim 7, wherein the Orthomyxovirus is an influenza virus.

9. The vaccine composition of claim 8, wherein the influenza virus is Influenza A virus. 102 10. The vaccine composition of claim 9, wherein the ORF is encoded by at least a portion of segment 8 of the Influenza A virus genome.

11. The vaccine composition of claim 10, wherein the ORF is at least 85 codons in length.

12. The vaccine composition of claim 10 or 11, wherein the ORF has a length of at least 167 codons.

13. The vaccine composition of any one of claims 10 to 12, wherein the ORF has a length of at least 216 codons.

14. The vaccine composition of claim 12 or 13, wherein the Influenza A virus is Spanish flu virus or a reconstructed Spanish flu virus.

15. The vaccine composition of claim 14, wherein the ORF comprises the sequence of SEQ ID NO. 56 or a variant thereof, or the sequence of SEQ ID NO: 57 or a variant thereof.

16. The vaccine composition of any one of claims 9 to 15, wherein the CD8+ T cell epitope is conserved among human Influenza A viruses.

17. The vaccine composition of any one of claims 9 to 16, wherein the CD8+ T cell epitope is conserved between human Influenza A virus and swine, equine and / or avian Influenza A viruses.

18. The vaccine composition of any one of claims 9 to 17, wherein the CD8+ T cell epitope contained in the ORF is predicted to be at least 85, at least 167 or at least 216 codons long in swine, horse and / or bird avian influenza A virus.

19. The vaccine composition of claim 17 or 18, wherein the swine influenza A virus is serotype H1N1. 103 20. A vaccine composition of any one of the preceding claims, containing one or more peptides set forth in SEQ ID NO: 16 to 53.

21. The vaccine composition of any one of claims 1 to 6, wherein the ssRNA virus is a filovirus.

22. The vaccine composition of claim 21, wherein the filovirus is an Ebola virus or a Marburg virus.

23. The vaccine composition of any one of claims 1 to 5, wherein the ssRNA virus is a positive-sense ssRNA virus and the ORF is a negative-sense virus.

24. The vaccine composition of claim 23, wherein the ssRNA virus is a flavivirus.

25. The vaccine composition of claim 24, wherein the flavivirus is Dengue virus or Zika virus.

26. A method for preventing or treating a viral infection, comprising administering a vaccine composition of any one of the foregoing claims to an individual infected with, or at risk of being infected with, an ssRNA virus.

27. A vaccine composition of any one of claims 1 to 25 for use in a method for preventing or treating a viral infection in an individual.

28. The method of claim 26 or the vaccine composition for use according to claim 27, wherein the viral infection is caused by a zoonotic virus.

29. The method of claim 26 or 28 or the vaccine composition for use according to claim 27 or 28, wherein the individual is a human being. 104 30. The method of claim 26 or the vaccine composition for use according to claim 27, wherein the viral infection is a pandemic viral infection.

31. A method for identifying immunogenic peptides comprising CD8+ T cell epitopes from ORFs encoded by at least a portion of the genome of an ssRNA virus in the sense opposite to a translation-competent positive-sense RNA by: (a) identifying ORFs encoded by at least a portion of the genome of the ssRNA virus in the sense opposite to a translation-competent positive-sense RNA; (b) predicting the sequence of a polypeptide encoded by the ORF; and (c) assessing whether peptides that bind MHC class I molecules include sequences contained in the predicted sequence, thereby identifying immunogenic peptides containing CD8+ T cell epitopes.

32. The method of claim 31, wherein the ORF includes a stop codon, the predicted sequence is predicted on the basis that the stop codon is mutated to a codon encoding an amino acid and the peptide includes a sequence contained in a portion of the predicted sequence that is C-terminal to the mutated codon.

33. The method of claim 31 or 32, further comprising: (d) contacting CD8+ T cells obtained from an individual infected with, or previously infected with, an ssRNA virus with the peptide; and (e) measuring in vitro the immune response to the peptide.

34. The method of claim 33, wherein the immune response is measured in vitro by determining the production of gamma interferon (IFNy).

35. An immunogenic peptide containing a CD4+ T cell epitope or a B cell epitope from a polypeptide encoded by an ORF encoded by at least part of the genome of an ssRNA virus in the sense opposite to a positive sense RNA capable of translation. 105 36. A method for determining the pandemic potential of an Influenza A virus, the method comprising the steps of: (i) identifying a first ORF encoded by at least a portion of segment 8 of the Influenza A virus genome in the opposite sense of translation-capable positive-sense RNA; (ii) determining the number of codons contained in the first ORF; and (iii) comparing the number of codons contained in the first ORF with the number of codons contained in a second ORF encoded by at least a portion of segment 8 of the known pandemic Influenza A virus genome in the opposite sense of translation-capable positive-sense RNA, wherein the difference in the number of codons in the first ORF compared to the second ORF is indicative of pandemic potential.

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