Differential effect of human immunodeficiency virus infection on the IgA and IgG antibody responses to pneumococcal vaccine.

The IgA, IgM, and IgG antibody responses to pneumococcal polysaccharide vaccine were analyzed in 35 asymptomatic or mildly symptomatic human immunodeficiency virus (HIV)-infected patients stratified according to their CD4 cell counts and in 12 healthy controls. Both the antibody titers in serum and saliva and the numbers of circulating antigen-specific antibody-producing cells (Elispot technique) were measured. At the peak of the antibody responses, HIV-infected patients mounted nearly normal IgG responses, while their IgM responses were significantly depressed, regardless of their CD4 cell counts. The IgA antibody response was decreased in patients with < 500 CD4 circulating cells/mm3. Most IgG antibodies belonged to the IgG2 subclass, and most IgA antibodies were dimeric IgA2 in both controls and patients. Anti-capsular pneumococcal polysaccharide IgG titers decreased much more rapidly in HIV-infected patients so that in all groups they were significantly lower than in controls 9 months after vaccination.