Development of subtype-specific and heterosubtypic antibodies to the influenza A virus hemagglutinin after primary infection in children.

Children undergoing primary infection with an H1N1 or H3N2 influenza A virus developed subtype-specific hemagglutination inhibition antibodies and enzyme-linked immunosorbent assay antibodies to purified hemagglutinin (HA) of the infecting virus subtype. They also developed lower titered ELISA antibodies to the noninfecting H1 or H3 HA and to H8 (an avian strain) HA. Thus, after primary infection with an influenza A virus, children develop enzyme-linked immunosorbent assay, but not hemagglutination inhibition, antibodies reactive with heterosubtypic HAs. These heterosubtypic antibodies could influence the response to infection with other wild-type or attenuated vaccine strains of influenza A virus.