Protective Role of Antigens from Peritoneal Exudates of Infected Mice against Toxoplasmosis

Abstract

<b>Background</b>: Toxoplasma gondii is an obligate intracellular parasite that infects all mammalian cells. Several antigens such as excreted/secreted antigens have been identified as a potential vaccine candidate. <br/><b>Objective</b>: To determine how excreted/secreted antigens from peritoneal exudates of infected mice (mESA) stimulate cell-mediated immune responses and induce protective immunity against toxoplasmosis in the murine model. <br/><b>Methods</b>: The supernatants produced from the peritoneal fluids, were fractionated by precipitation in ammonium sulphate solution (30-80% saturated). For induction of cell-mediated immune responses, delayed type hypersensitivity was measured, in injected footpad. Response to purified antigen was measured by lymphocyte proliferation assay. Nitric oxide was measured by Griess method. For immunization, Balb/c mice were immunized 2 times with mESA, mESA-40% and Toxoplasma Lysate Antigen (TLA). The virulent RH strain of Toxoplasma gondii was used for challenging. <br/><b>Results</b>: The pattern of lymphocyte responsiveness was dependent on the antigen employed. In sensitized mice, those received mESA-40% displayed higher lymphocyte response than mice stimulated by mESA (p<0.05). The highest amounts of nitric oxide were observed in macrophages, which received mESA-40% and mESA (p<0.05). Mice immunized with mESA-40% survived longer than those immunized with mESA and other antigens (p<0.05). <br/><b>Conclusion</b>: As fraction 40% (mESA-40%) showed a good result in induction of cellmediated responses in the murine model, the purification and isolation of the mESA 40% is highly recommended for future study.