Nanoemulsion adjuvanted COBRA HA vaccine enhances protective antibody titers against H1N1 and H3N2 influenza viruses

Adjuvants can enhance the elicited immune responses to recombinant hemagglutinin (HA) proteins following intramuscular vaccination. In this study, computationally optimized broadly reactive antigen (COBRA) designed HA proteins were adjuvanted with the W805EC oil-in-water nanoemulsion (“NE01”) and used to vaccinate mice. The elicited influenza-specific humoral and cellular immune responses were evaluated. Mice vaccinated with adjuvanted COBRA H1 and H3 HA vaccine candidates had higher antibody titers compared to mice vaccinated with unadjuvanted HA proteins. Mice administered COBRA HA plus NE01 had higher hemagglutination inhibition (HAI) specific antibody titers against a panel of H1N1 and H3N2 influenza viruses, as well as higher levels of interferon-gamma (IFN-γ) secreting splenocytes. Mice vaccinated with adjuvanted COBRA HA proteins had statistically less weight loss following challenge, as well as undetectable viral lung titers compared to mice administered unadjuvanted vaccine.