Toxoplasma antigens recognized by human immunoglobulin A antibodies.

The immunoglobulin A (IgA) antibody response to antigens of Toxoplasma gondii during the acute and chronic stages of T. gondii infection was studied by immunoblotting with a nonreduced antigen (NRA) preparation. Serum samples were from individuals with acute or chronic T. gondii infection, and sequential samples were from women who seroconverted during gestation or congenitally infected infants. IgA antibodies to a variety of antigens were present in sera from each of the groups, irrespective of the titer in an IgA enzyme-linked immunosorbent assay. The predominant NRA recognized by IgA antibodies in sera from each of the four groups had an approximate molecular weight of 30,000. Other prominent NRAs had approximate molecular weights of 35,000 and 5,000; however, the latter NRA was not present in sera of congenitally infected infants.