Presence of high concentrations of circulating Toxoplasma antigens during acute Toxoplasma infection in athymic nude mice.

In mice infected with an avirulent strain of Toxoplasma gondii, circulating Toxoplasma antigens were detectable in the sera during weeks 1 to 3 of infection by a simple agglutination test that uses latex particles coated with anti-Toxoplasma antibodies. An infection in athymic nude mice resulted in high agglutination titers in the anti-Toxoplasma antibody-coated latex particle test and the absence of anti-Toxoplasma antibodies in sera during the acute phase, suggesting that the detection of circulating Toxoplasma antigens is a good tool for the diagnosis of acute toxoplasmosis, especially in severely immunocompromised hosts.