Serological characterization of guinea pigs infected with H3N2 human influenza or immunized with hemagglutinin protein

Bushnell, Ruth V; Tobin, John K; Long, Jinxue; Schultz-Cherry, Stacey; Chaudhuri, A Ray; Nara, Peter L; Tobin, Gregory J

BACKGROUND: Recent and previous studies have shown that guinea pigs can be infected with, and transmit, human influenza viruses. Therefore guinea pig may be a useful animal model for better understanding influenza infection and assessing vaccine strategies. To more fully characterize the model, antibody responses following either infection/re-infection with human influenza A/Wyoming/03/2003 H3N2 or immunization with its homologous recombinant hemagglutinin (HA) protein were studied. RESULTS: Serological samples were collected and tested for anti-HA immunoglobulin by ELISA, antiviral antibodies by hemagglutination inhibition (HI), and recognition of linear epitopes by peptide scanning (PepScan). Animals inoculated with infectious virus demonstrated pronounced viral replication and subsequent serological conversion. Animals either immunized with the homologous HA antigen or infected, showed a relatively rapid rise in antibody titers to the HA glycoprotein in ELISA assays. Antiviral antibodies, measured by HI assay, were detectable after the second inoculation. PepScan data identified both previously recognized and newly defined linear epitopes. CONCLUSIONS: Infection and/or recombinant HA immunization of guinea pigs with H3N2 Wyoming influenza virus resulted in a relatively rapid production of viral-specific antibody thus demonstrating the strong immunogenicity of the major viral structural proteins in this animal model for influenza infection. The sensitivity of the immune response supports the utility of the guinea pig as a useful animal model of influenza infection and immunization.