IgG, IgM, and IgA response to HIV in infants born to HIV-1 infected mothers. Swiss Neonatal HIV Study Group.

Children born to HIV-1-positive mothers were prospectively tested for HIV-reactive IgG, IgM, and IgA by Western blot, in order to study the children's humoral immune response in the background of passively transferred maternal IgG. In infected infants, a response was first seen at 1-3 months for env-reactive IgM and IgA, as well as gag-reactive IgM and IgG. This was followed by production of IgG to env, IgA to pol and to gag p17 and p55 at 7-9 months, and IgG to pol at 10-12 months. IgG Western blot positivity by all interpretation guidelines in all infected infants was found by 10-12 months. Subsequently, only IgG to env and p24, and IgA to env were maintained in all, whereas IgG to pol and p17 disappeared again in a significant fraction. A considerable proportion of uninfected infants also produced gag-reactive antibodies: IgM at 1-3 months, followed by IgG, which persisted in 10-20% and were also found in children born to uninfected mothers. These antibodies were, however, present at lower titers than in infected infants and were apparently produced in response to agent(s) different from HIV. Maternal antibodies to env disappeared significantly faster in infected than uninfected infants. Traces of HIV-reactive IgG were present for up to 21 months in children who subsequently seroreverted completely.