Improved serological diagnosis of Toxoplasma gondii infection by detection of immunoglobulin A (IgA) and IgM antibodies against P30 by using the immunoblot technique.

Immunoglobulin M (IgM) and IgA antibodies against the major surface protein of Toxoplasma gondii were determined in a total of 195 human sera and five human cerebrospinal fluids by using a P30 membrane extract and the immunoblot technique. By using two different T. gondii strains (RH and BK) simultaneously as antigens, we were able to demonstrate diagnostically important strain-specific human antibody responses in 4.5% of the samples tested. A comparison of the immunoblot technique with an IgM immunocapture enzyme-linked immunosorbent assay demonstrated that the IgM and IgA immunoblot seems to be of advantage in the diagnosis of acute toxoplasmosis in certain groups of patients, especially in the diagnosis of cerebral toxoplasmosis in patients with AIDS. The immunoblot technique described is easy to perform and might be useful as an additional serological assay for routine diagnosis of T. gondii infections.