Detection of circulating antigens by latex particles coated with anti-Toxoplasma antibodies during acute infections with Toxoplasma gondii in mice

An appearance of Toxoplasma antigens in sera of infected mice was measured by an agglutination test using anti-Toxoplasma antibody-coated latex particles. In the primary infections with the virulent RH strain of T. gondii, c-Ag could be detected earlier than the appearance of anti-Toxoplasma antibodies regardless of infectious doses of T. gondii. High concentrations of c-Ag were still detected by the Ag-LA test after the start of production of anti-Toxoplasma IgM antibodies. On the other hand, in the secondary infection with the virulent organisms, c-Ag was not observed although the mice died of acute toxoplamosis. These results suggest that detection of c-Ag by the Ag-LA test would be available for a rapid etiological diagnosis in human cases of primary acute toxoplasmosis.