Animal models for Toxoplasma gondii infection.

Toxoplasma gondii is an obligate intracellular protozoan that commonly infects mammals and birds throughout the world. This unit describes murine models of acute T. gondii infection and toxoplasmic encephalitis. T. gondii infection in severe combined immunodeficient (SCID) mice, which lack T and B cells, has allowed for the study of T cell-independent mechanisms of defense against intracellular organisms, as described here. The establishment of temperature-sensitive mutant strains of T. gondii has allowed adoptive-transfer experiments without the concern for the transfer of the parasite at the same time. The temperature-sensitive mutant ts-4 strain disappears from tissues of immunocompetent mice without forming tissue cysts and induces protection against challenge with virulent strains of the parasite, and a protocol is provided for infection with this mutant strain. Support protocols present methodology for evaluation of progression of infection and immune response to the parasite, maintenance of T. gondii tissue cysts and tachyzoites, as well as preparation of T. gondii lysate antigens.