Investigations on strain-specific and common antigen antihemagglutinin antibodies oriented to the influenza virus H3N2 strains A/Hong Kong/1/68 and A/Port Chalmers/1/73.

Antisera raised by vaccination of chickens with the H3N2 influenza virus strains A/Hong Kong/1/68 and A/Port/Chalmers/1/73 were found to contain common antigen antibody (CAA), combining with both viruses, and strain-specific antibody (SSA), combining with homologous virus only. The reaction of CAA with homologous and heterologous viruses and of SSA with homologous virus was investigated by means of equilibrium filtration. CAA was found to be antibody of higher quality than was SSA. The virus strains tested were found not to contain identical common antigenic determinants, and CAA and SSA competed for the same antigenic sites when allowed to react simultaneously with homologous virus. The kinetics of reaction of CAA and SSA with the corresponding viruses was tested by means of the photometric antibody concentration unit method. It was found that SSA and CAA of a given strain have the same specificity and that the reaction of CAA with heterologous virus is registered as heterologous antigen-antibody interaction. These findings suggest that SSA and CAA are antibodies of the same specificity but with differences in quality.