Virologic and serologic aspects of human immunodeficiency virus infection in infants and children.

Serologic diagnosis of HIV infection in infants and children is made especially difficult by the universal presence of maternal antibodies in blood during the first year of life, technical difficulties associated with the measurement of virus-specific IgM antibodies (except, perhaps, when the mother and, hence, the child have been very recently infected), and the weaker and more limited antibody reactivities revealed by Western blot analysis. Infants in the first year of life who develop reactivities on a Western blot that are different from those of their mothers are almost certainly infected. In addition, infants whose lymphocytes can be stimulated in vitro to produce HIV-specific antibodies of both the IgG and IgM isotypes and whose viral-specific antibodies can be found in the IgG3 subclass are also likely to be infected. Finally, children older than 15 months of age who remain seropositive by Western blot and who have both clinical and immunologic abnormalities consistent with HIV infection are also, doubtlessly, infected.