Protective efficacy of two novel DNA vaccines expressing Toxoplasma gondii rhomboid 4 and rhomboid 5 proteins against acute and chronic toxoplasmosis in mice

Objectives: To evaluate the protective efficacy of two novel DNA vaccines expressing Toxoplasma gondii rhomboid 4 (ROM4) and rhomboid 5 (ROM5) proteins against acute and chronic toxoplasmosis. Methods: DNA vaccines (pVAX-TgROM5 and pVAX-TgROM4) were constructed and their immunogenicity evaluated in Kunming mice. Results: Mice vaccinated with pVAX-TgROM5 or pVAX-TgROM4 elicited strong Th1-type humoral and cellular responses, with higher level of IgG antibody titers (the predominance of IgG2a production), and increased levels of CD4(+) and CD8(+) T cells and cytokines IFN-gamma, IL-2, IL-12 (p70) and IL-23. Mice vaccinated with pVAX-TgROM5 (11 days) showed a significantly longer survival time compared with controls (8 days) (p < 0.05) after lethal challenge. Brain cyst numbers of mice vaccinated with pVAX-TgROM5 and pVAX-TgROM4 reduced significantly (p < 0.05) (72.04 and 44.08%, respectively) compared with control groups after chronic challenge. Conclusion: The pVAX-TgROM5 showed a better protective efficacy against acute and chronic toxoplasmosis compared to pVAX-TgROM4.