VALUE OF SPECIFIC IMMUNOGLOBULIN-A DETECTION BY 2 IMMUNOCAPTURE ASSAYS IN THE DIAGNOSIS OF TOXOPLASMOSIS

The diagnosis of Toxoplasma gondii infection is currently based on imm unological tests, but tests for IgG and IgM antibodies alone are often insufficient to assess the risk of active disease, especially during pregnancy and in immunodeficient subjects, The supplementary diagnosti c value of testing for antitoxoplasmic IgA in cases of acute, chronic, congenital and reactivated toxoplasmosis, relative to classical immun ological tests, was evaluated using two immunocapture tests, one based on tachyzoite agglutination and the other on an immunoenzymatic compl ex recognizing the membrane protein P30 of Toxoplasma gondii A total o f 4,541 sera from 395 uninfected subjects, 468 immunized subjects with chronic infection, 117 subjects with acute infection and 403 children , 103 of whom had congenital toxoplasmosis, was tested. Specific IgA t ests were negative in the nonimmune population, but tests for this imm unoglobulin subtype became positive very rapidly during primary infect ion, and IgA disappeared more rapidly than IgM. In the children infect ed in utero, specific IgA was detected more frequently than IgM. In co ntrast, in a population of HIV-seropositive subjects with clinical tox oplasmosis, tests for IgA were poorly sensitive. The two tests for spe cific IgA produced similar results, except in the early stages of prim ary infection, in which immunoenzymatic testing for anti-P30 IgA was l ess sensitive than the agglutination method.