Immunoglobulin G subclass antibody responses of mice to influenza virus antigens given in different forms.

Total IgG and IgG subclass antibody responses in mice were studied after infection with virulent and non-virulent influenza viruses, and after vaccination with inactivated whole virus or purified surface glycoproteins (HANA-flu). Infection induced high IgG2a, low IgG1 and IgG2b, and very low IgG3 levels of antibody in serum. Whole virus vaccine induced high IgG2a, moderate IgG2b, and very low IgG1 and IgG3 levels of antibody. In marked contrast, HANA-flu preparations induced high IgG1, low IgG2a, and very low IgG2b and IgG3 levels of antibody. Booster doses of whole virus and HANA-flu significantly elevated serum antibody levels, but the relative distribution of anti-influenzal antibody among the IgG subclasses was unchanged. Mice primed with HANA-flu prior to infection with mouse-adapted virus, produced high IgG2a, moderate IgG1, and low IgG2b and IgG3 levels of serum antibody. These data indicate that the physical form in which viral protein antigens are presented to the immune system can influence the subclass distribution of antibodies produced during primary immune responses and that once priming has occurred, responses to antigen presented in a different form are altered.