Detection of IgA specific for toxoplasmosis in serum and cerebrospinal fluid using a non-enzymatic IgA-capture assay.

A non-enzymatic immuno assay was optimized for detection of immunoglobulin A in serum and cerebrospinal fluid specific in acquired and congenital toxoplasmosis. An antihuman IgA monoclonal antibody was coated onto a polystyrene to capture total IgA. Suspensions of Toxoplasma gondii were used as a visible antigen. Eight hundred specimens (sera, cord blood serum, and cerebrospinal fluid) were tested. These were collected from 300 patients with acquired toxoplasmosis and from 28 children with congenital toxoplasmosis. In acquired toxoplasmosis, the assay allowed early detection of specific IgA, with kinetics similar to those of specific IgM expression. In congenital toxoplasmosis, anti-T. gondii IgA could be detected in the neonatal period. This assay was useful for diagnosis, follow-up, and posttherapeutic evaluation of toxoplasmosis. Specific IgA was also detected in the cerebrospinal fluid of infected newborn children. This simple IgA capture assay improves serological diagnosis of acquired and congenital toxoplasmosis when used in combination with analysis of T. gondii specific IgG and IgM.