Abstract
Inactivated vaccines prepared form influenza virus strains obtained by the recombination of A/PR/8/34 (H1N1) or A/FM/1/47 (H1N1) viruses with A/Victoria/3/75 (H3N2) virus, were tested for their antigenicity in hamsters. The parental origin of the genes of each cloned recombinant virus was determined by polyacrylamide gel electrophoresis, and vaccines prepared from each strain by concentration, purification on sucrose density gradients and inactivation with formalin. All the recombinant strains used in these studies possessed surface haemagglutinin and neuraminidase antigens derived from the A/Victoria/75 parent strain. On inoculation into hamsters, at equivalent concentrations, these vaccines varied in their ability to induce haemagglutination-inhibiting (HI) antibodies in the serum. This variation was not dependent on concentration and was observed using neutralization and single radial haemolysis, as well as HI. The possible reasons for the findings are discussed.