Induction of neutralizing antibodies to influenza A virus H7N9 by inactivated whole virus in mice and nonhuman primates

•The immunogenicity of hemagglutinin (HA) of newly emerged influenza A virus H7N9 need to be known.•Inactivated whole-virion containing HA and NA of H7N9 in the PR8 background was evaluated.•Antibody titers were assessed in different doses of HA alone, or with alum, and/or with a booster.•Immunization could produce neutralizing antibodies in mice and rhesus macaques.•Mice received sera from immunized animals could be protected from lethal challenge of H7N9 virus.

We evaluated the immunogenicity of hemagglutinin (HA) in the context of inactivated H7N9/AH/1/13-PR8 whole-virion. At 4 weeks after immunization with 15 μg HA, mice produced hemagglutination inhibition (HI) titers of 1:192 and neutralizing antibodies of 1:317. Aluminum hydroxide (alum), or a booster immunization, or both increased HI to 1:768, 1:384, 1:896 and neutralizing antibodies to 1:1868, 1:2302, 1:10,000, respectively. Macaques generated HI of 1:190 or 1:360 and virus neutralizing titers of 1:280 or 1:658 at 3 weeks after immunization with HA alone or with alum. Sera from immunized mice and macaques protected mice from infection of A/Anhui/1/2013 (H7N9), suggesting an H7N9 vaccine is immunologically feasible.