Abstract: 　AIM: To explore the protective effect and cellular immune response of uv-attenuated ZS1 strain trophozoites of Toxoplasma gondii in mice. METHODS: The ZS1 strain trophozoites of T.gondii were irradiated by uv-light with 2537 \{°A\} wave length for 60 minutes. Mice were divided into 4 groups. Group 1 was vaccinated alone, group 2 was challenged with normal ZS1 trophozoites on d45 after vaccination, group 3 was infected alone, and group 4 was normal control. The changes in splenic T cell proliferation, level of CD4+ and CD8+ T cell, and NK cell activity were compared. RESULTS: Group1 mice survived normally, no trophozoite,pseudo-cyst or cyst was detected in the tissues on d49 after vaccination. Group 2 mice survived longer than those of group 3. The T lymphocyte proliferation in response to soluble antigen of T.gondii was significantly enhanced in group 2, and suppressed in group 3. The level of CD4+ T cell in group 2 was decreased, resulting in a reverse of CD4+/CD8+ ratio. The NK cell activities in groups 1, 2 and 3 were all significantly increased. CONCLUSION: The uv-attenuated vaccine of T.gondii ZS1 strain could induce certain protective immunity against challenge infection, in which CD8+ T cell and NK cell might play an important role.\;

Key words: Toxoplasma gondii, uv-attenuated, splenic lymphocyte proliferation, CD4+/CD8+ T cell, NK cell