Characterization of antibody and cytotoxic T lymphocyte responses to human influenza virus H3 haemagglutinin expressed from the haemagglutinin locus of vaccinia virus.

Antibody and cytotoxic T lymphocyte (CTL) responses to the haemagglutinin (HA) of human H3N2 influenza virus were analysed, using recombinant vaccinia viruses containing the influenza HA gene inserted into the HA gene locus of vaccinia virus. The recombinant vaccinia viruses elicited a high haemagglutination inhibiting (HI) antibody response to the homologous influenza virus in mice. In addition, HI antibody generated by the recombinant vaccinia virus reacted with antigenic variants of human H3N2 influenza virus in a manner similar to that elicited by the HA vaccine. Mice with a high response to influenza virus HA vaccine were highly responsive to the HA expressed from the recombinant vaccinia virus, as measured by HI antibody production. The immunogenicity of the influenza virus HA expressed by the recombinant seems to be attributable to the intrinsic immunogenicity of the HA molecule. The recombinants primed mice for an influenza virus H3-specific CTL response and primed CTLs recognized the target cells in a subtype-specific manner. The results indicate that a recombinant vaccinia virus derived by the insertion of a foreign gene into its HA gene locus is a potent live vaccine not only for eliciting a high antibody response but also for priming a specific CTL response.