Conserved epitopes of influenza A virus inducing protective immunity and their prospects for universal vaccine development

Bioengineering of viruses and virus-like particles (VLPs) is a well-established approach in the development of new and improved vaccines against viral and bacterial pathogens. We report here that the capsid of a major avian pathogen, infectious bursal disease virus (IBDV), can accommodate heterologous proteins to induce protective immunity. The structural units of the ϳ70-nmdiameter T‫31؍‬ IBDV capsid are trimers of VP2, which is made as a precursor (pVP2). The pVP2 C-terminal domain has an amphipathic ␣ helix that controls VP2 polymorphism. In the absence of the VP3 scaffolding protein, 466-residue pVP2 intermediates bearing this ␣ helix assemble into genuine VLPs only when expressed with an N-terminal His 6 tag (the HT-VP2-466 protein). HT-VP2-466 capsids are optimal for protein insertion, as they are large enough (cargo space, ϳ78,000 nm 3 ) and are assembled from a single protein. We explored HT-VP2-466-based chimeric capsids initially using enhanced green fluorescent protein (EGFP). The VLP assembly yield was efficient when we coexpressed EGFP-HT-VP2-466 and HT-VP2-466 from two recombinant baculoviruses. The native EGFP structure (ϳ240 copies/virion) was successfully inserted in a functional form, as VLPs were fluorescent, and three-dimensional cryo-electron microscopy showed that the EGFP molecules incorporated at the inner capsid surface. Immunization of mice with purified EGFP-VLPs elicited anti-EGFP antibodies. We also inserted hemagglutinin (HA) and matrix (M2) protein epitopes derived from the mouse-adapted A/PR/8/34 influenza virus and engineered several HA-and M2-derived chimeric capsids. Mice immunized with VLPs containing the HA stalk, an M2 fragment, or both antigens developed full protection against viral challenge. IMPORTANCEVirus-like particles (VLPs) are multimeric protein cages that mimic the infectious virus capsid and are potential candidates as nonliving vaccines that induce long-lasting protection. Chimeric VLPs can display or include foreign antigens, which could be a conserved epitope to elicit broadly neutralizing antibodies or several variable epitopes effective against a large number of viral strains. We report the biochemical, structural, and immunological characterization of chimeric VLPs derived from infectious bursal disease virus (IBDV), an important poultry pathogen. To test the potential of IBDV VLPs as a vaccine vehicle, we used the enhanced green fluorescent protein and two fragments derived from the hemagglutinin and the M2 matrix protein of the human murine-adapted influenza virus. The IBDV capsid protein fused to influenza virus peptides formed assemblies able to protect mice against viral challenge. Our studies establish the basis for a new generation of multivalent IBDV-based vaccines.

Section: Discussionmentioning

confidence: 99%

Structural Basis for the Development of Avian Virus Capsids That Display Influenza Virus Proteins and Induce Protective Immunity

Pascual

Mata

Gómez-Blanco

et al. 2015

“…This frequent antigenic drift or shift requires regular updating of the vaccine composition (12). Therefore, several research teams and vaccine manufacturers are focusing on the design of new "universal" vaccine strategies, using the most conserved influenza antigenic motifs like those carried by influenza virus nucleoprotein (NP), M1, the stem domain of HA, and the ectodomain of M2 (M2e) (13).…”

mentioning

confidence: 99%

A Novel Subnucleocapsid Nanoplatform for Mucosal Vaccination against Influenza Virus That Targets the Ectodomain of Matrix Protein 2

Hervé

Raliou

Bourdieu

et al. 2014

In this study, subnucleocapsid nanorings formed by the recombinant nucleoprotein (N) of the respiratory syncytial virus were evaluated as a platform to anchor heterologous antigens. The ectodomain of the influenza virus A matrix protein 2 (M2e) is highly conserved and elicits protective antibodies when it is linked to an immunogenic carrier, making it a promising target to develop universal influenza vaccines. In this context, one or three M2e copies were genetically linked to the C terminus of N to produce N-M2e and N-3M2e chimeric recombinant nanorings. Mice were immunized intranasally with N-M2e or N-3M2e or with M2e or 3M2e control peptides. N-3M2e-vaccinated mice showed the strongest mucosal and systemic antibody responses. These mice presented a reduced viral load and minor weight loss, and all survived upon challenge with influenza virus A/PR8/34 (H1N1) (PR8). We compared the intranasal route to the subcutaneous route of N-3M2e immunization. Only the intranasal route induced a strong local IgA response and led to the protection of mice upon challenge. Finally, we demonstrated that the induction of anti-M2e antibodies by N-3M2e is not impaired by preexisting anti-N immunity. Overall, these results show that the N nanoring is a potent carrier for mucosal delivery of vaccinal antigens.

“…Efforts to develop such universal vaccines encompass a wide range of aspects, including the identification of previously unknown conserved regions or T cell epitopes and new antibodies with broad reactivity that, in turn, could expedite the development of new and more effective strategies (11,13,16,24,28,35,38,41). In addition, extensive studies of the humoral and cell-mediated immunity responsible for inducing cross-protection are being carried out (3,33). The potential importance of cross-protection also triggered many recent studies addressing the effect of either prior exposure to seasonal influenza viruses or vaccination against them on the immune responses to a pandemic virus, particularly the 2009 pandemic A H1N1 influenza virus (1,6,7,14,36,40).…”

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confidence: 99%

Cold-Adapted Pandemic 2009 H1N1 Influenza Virus Live Vaccine Elicits Cross-Reactive Immune Responses against Seasonal and H5 Influenza A Viruses

Jang

Byun

Lee

et al. 2012

The rapid transmission of the pandemic 2009 H1N1 influenza virus (pH1N1) among humans has raised the concern of a potential emergence of reassortment between pH1N1 and highly pathogenic influenza strains, especially the avian H5N1 influenza virus. Here, we report that the cold-adapted pH1N1 live attenuated vaccine (CApH1N1) elicits cross-reactive immunity to seasonal and H5 influenza A viruses in the mouse model. Immunization with CApH1N1 induced both systemic and mucosal antibodies with broad reactivity to seasonal and H5 strains, including HAPI H5N1 and the avian H5N2 virus, providing complete protection against heterologous and heterosubtypic lethal challenges. Our results not only accentuate the merit of using live attenuated influenza virus vaccines in view of cross-reactivity but also represent the potential of CApH1N1 live vaccine for mitigating the clinical severity of infections that arise from reassortments between pH1N1 and highly pathogenic H5 subtype viruses.