Avirulent Wh6 strain of Toxoplasna gondii genotype Chinese 1 induced complete protective immunity against the challenge of high virulent Wh3 strain in mice
School of Basic Medical Sciences, Anhui Medical University, Department of Microbiology and Parasitology, Anhui Provincial Laboratory of Pathogen Biology and Anhui Key Laboratory of Zoonoses, Hefei 230032, China
Abstract：The aim of this study was to explore the protective effect of Toxoplasma gondii avirulent Wh6 strain infection on the challenge of the high virulent strain in BALB/c mice, to find a new attenuated vaccine of viable parasite. Thirty BALB/c female mice were randomly divided into three groups, GroupI, GroupII and Group III. BALB/c mice in Group I were intragastrically infected with 25-35 cysts of Wh6 strains while mice in GroupII treated, with PBS, and additional 10 mice were used as normal control. At 35 days post infection, the brain tissues of mice inoculated with avirulent Wh6 strain were examined for Toxo plasma cysts under microscope. Subsequently the mice of Group I and II were challenged with 3000 tachyzoites of high virulent Wh3 strain. One week after challenge, the survival of mice and parasite burden in the peritoneal cavity were evaluated, spleen cell suspensions were prepared and Th1 and Th2 cells for 3 groups were detected by flow cytometry. Quantitation of Th1 and Th2 cytokines in spleen tissue by qRT-PCR and enzyme-linked immunosorbent assay respectively. All mice in Group I survived for more than 15 days until the experiments ended but the animals in Group II totally died after one week of Wh3 strain infection. The levels of Th1 and Th2 cytokines of IFN-γ, IL-10 and IL-12 in the spleen cell culture supernatant of group II were significantly higher than those in group I (P< 0.001).Conclusions:These results indicated that BALB/c mice inoculated with avirulent Wh6 strain may survive the lethal infection of Wh3 strain, suggesting a potential significant role of Wh6 strain in novel approach of viable attenuated parasite vaccine against toxoplasmosis.
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2020, Vol. 36 
