The serum antibody response distributed in subclasses and isotypes after intranasal and subcutaneous immunization with influenza virus immunostimulating complexes.

Immunostimulating complexes (iscoms) were prepared from influenza virus glycoproteins (A/PR8(H1N1]. Mice were inoculated with iscoms by local (oral or intranasal) as well as by subcutaneous administration. It was shown that one subcutaneous or intranasal inoculation induced serum antibody responses of similar magnitude. The intranasal administration, however, induced somewhat higher IgA and IgM titres than that induced subcutaneously. After a second intranasal or subcutaneous inoculation a prominent increase of the IgG isotypes was found. The secondary IgA and IgM responses were of similar magnitude as those induced after the primary inoculation. The antibody responses induced were evenly distributed within the IgG isotypes, although the highest titres recorded were of the IgG1 and IgG2 isotypes.