Iranian

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The Immunogenicity of γ-irradiated tachyzoites of a highly virulent strain of Toxoplasma gondii (RH strain) was investigated. Immunized mice survived challenge infection and displayed increased interferon gamma (INF-γ ) production. On the other hand, nonimmunized controls died after 10 days and displayed a significantly decreased lymphoproliferative response to Concanavalin A (Con A). No tachyzoites were detected in peritoneal exudates of the immunized mice 10 days after challenge. These results indicate that the vaccination with γ-irradiated tachyzoites not only protects the mice against challenge infection, but may circumvent the danger of the vaccine being life-threatening because of remaining tachyzoites inside macrophages posing as a latent infection.