IgA antibodies for diagnosis of acute congenital and acquired toxoplasmosis.

An ELISA for IgA toxoplasma antibodies was positive in 12 pregnant women who seroconverted during gestation. Positive IgA titers were also noted in 10 individuals with biopsy-proven toxoplasmic lymphadenitis; the highest titers were noted in the first months following onset of clinical signs. Toxoplasma IgA antibodies were also demonstrable in 8 of 9 infants/fetuses with congenital toxoplasma infection. In some, IgM antibodies could not be demonstrated. Among 20 patients with AIDS and biopsy-proven toxoplasmic encephalitis, only 1 had IgA antibodies. None of 20 individuals with chronic toxoplasma infection had demonstrable IgA antibodies. Demonstration of IgA toxoplasma antibodies should be useful for diagnosis of recently acquired infection and for diagnosis of the infection in the fetus and newborn.