Protection in mice immunized with a heterologous prime-boost regime using DNA and recombinant pseudorabies expressing TgSAG1 against Toxoplasma gondii challenge.

An effective vaccine of animals can block transmission of Toxoplasma gondii to humans. In this study, mice have been protected against lethal T. gondii challenge by a prime-boost vaccination strategy using DNA vaccine pVAX/TgSAG1 and recombinant pseudorabies virus rPRV/TgSAG1, both expressing the major immunodominant surface antigen of T. gondii (TgSAG1). High levels of splenocyte proliferative responses and significant levels of IFN-gamma resulted, with strong cytotoxic T lymphocyte (CTL) responses in vitro. After lethal challenge, prime-boost vaccinated mice showed an increased survival time (15.4+/-5.0 days) and a 40% survival rate compared with controls who all died within 11 days of challenge. Results of the present study indicated that this novel immunization strategy is useful in enhancing immune protection in mice against lethal T. gondii infection, which would provide foundation for the development of effective vaccines against T. gondii.