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In the present study,we constructed a DNA vaccine expressing T.gondii CDPK3 (TgCDPK3) and evaluated its protective efficacy against T.gondii in Kunming mice.The gene sequence encoding TgCDPK3 was inserted into the eukaryotic expression vector pVAX I,and immunized mice intramuscularly.The results showed that mice immunized with pVAX:CDPK3 developed a high level of.speci?c antibodies and a strong lymphoproliferative response.The signi?cantly increased levels ofIFN: γ,IL:2,IL: 12 (p70) and IL:23 and high ratio of IgG2a to IgG1 antibody titers indicated that a Th 1 type response was elicited after immunization with pVAX:CDPK3.Furthermore,the percentage ofCD4+ T cells in mice vaccinated with pVAX:CDPK3 was significantly increased.After lethal challenge using the virulent RH strain ofT.gondii tachyzoites,the mice immunized with pVAX:CDPK3 prolonged the survival time from 10 days to24 days (13.5 ± 4.89) compared to untreated mice or those received PBS or pVAX I within 7 days (P < 0.05).In chronic infection model (10 cysts ofT.gondii PRU strain),the numbers of brain cysts of the mice in pVAX:CDPK3 group reduced signi?cantly when compared with those in control groups (P < 0.05),and the rate of reduction could reach to about 50%.TgCDPK3 can generate protective immunity against T.gondii infection in Kunming mice and is a promising vaccine candidate for further development of an effective vaccine against T.gondii.