Immunogenicity and effectiveness of a bivalent influenza A/H1N2 vaccine strain against seasonal human influenza A viruses in mice.

Background: Recent studies and reports have documented the ability of the co-circulating seasonal influenza A/H1N1 (ancestor: 2009 pandemic H1N1) and A/H3N2 to exchange their genetic segments, generating a novel H1N2 strain in different geographical localities around the world with an ability to infect human. This raises concerns and triggers alarms to develop a multivalent vaccine that can protect against the documented H1- and H3-type human influenza A viruses (IAVs).

Results: Here, we generated a PR8-based vaccine strain that carries the HA gene segment from the contemporary H1N1 virus while the NA gene segment was derived from a currently circulating influenza A/H3N2 strain. A recombinant PR8-based H1N2 vaccine strain (rgH1N2), engineered by reassortment between influenza A/H1N1 and A/H3N2 to mimic the documented human influenza A/H1N2, was used for immunization to provoke immunogenicity and cross-antigenicity against the H1- and H3-type human IAVs and was evaluated for its immunogenicity and effectiveness in mice. Following challenge infection of rgH1N2-vaccinated mice with contemporary influenza A/H1N1 and A/H3N2, results revealed that rgH1N2-vaccinated mice showed less viral shedding, more survival, and less body weight loss compared to control unvaccinated groups and vaccinated mice with rgH1N1 and rgH3N2.

Conclusions: This study highlights the applicability of the PR8-based H1N2 vaccine strain to protect against seasonal IAVs and emphasizes the role of both surface proteins, HA and NA, to stimulate protective and neutralizing antibodies against circulating influenza A/H1N1 and A/H3N2 strains.