Immunogenicity and protective efficacy of two recombinant pseudorabies viruses expressing Toxoplasma gondii SAG1 and MIC3 proteins.

Toxoplasma gondii is one of the most common parasitic pathogens in humans and warm-blooded animals, causing toxoplasmosis. One of the efficient ways to control this disease is immunization. In this study, two recombinant pseudorabies virus (PRV) expressing TgSAG1 (rPRV-SAG1) and TgMIC3 (rPRV-MIC3) based on the PRV vaccine strain were developed by homologous recombination and used for immunizing BALB/c mice. Ninety BALB/c mice were randomly divided into five groups including four experimental groups (inoculated twice in 4 weeks interval with PRV TK-/gG-/EGFP+, rPRV-SAG1, rPRV-MIC3, rPRV-SAG1+rPRV-MIC3, respectively) and one control group (inoculated with medium). All mice vaccinated with rPRV developed a high level of specific antibody responses against T. gondii lysate antigen (TLA), a strong increase of the splenocyte proliferative response, and significant levels of IFN-γ and IL-2 production. These results demonstrated that rPRV could induce significant humoral and cellular Th1 immune responses. Moreover, rPRV immunization induced partial protection against a lethal challenge with T. gondii RH strain, and neutralizing antibodies against PRV in a BALB/c mouse model. The mice immunized with the rPRV-SAG1 and rPRV-MIC3 cocktail could develop higher T. gondii-specific IgG antibodies and lymphocyte proliferative responses and conferred more efficient protection against T. gondii challenge. These results suggested that expression of protective antigens of T. gondii in PRV is a novel approach towards the development of a vaccine against both animal pseudorabies and toxoplasmosis.