Protective immunity against acute toxoplasmosis in BALB/c mice induced by a DNA vaccine encoding Toxoplasma gondii elongation factor 1-alpha

Background: Toxoplasma gondii can infect almost all warm-blood animals including human beings. The high incidence and severe damage that can be caused by T. gondii infection clearly indicates the need for the development of a vaccine. T. gondii elongation factor 1-alpha (TgEF-1 alpha) plays an important role in pathogenesis and host cell invasion for this parasite. The aim of this study was to evaluate the immune protective efficacy of a DNA vaccine encoding TgEF-1 alpha gene against acute T. gondii infection in mice. Methods: A DNA vaccine (pVAX-EF-1 alpha) encoding T. gondii EF-1 alpha (TgEF-1 alpha) gene was constructed and its immune response and protective efficacy against lethal challenge in BALB/c mice were evaluated. Results: Mice inoculated with the pVAX-EF-1 alpha vaccine had a high level of specific anti-T. gondii antibodies and produced high levels of IFN-gamma, interleukin (IL)-4, and IL-17. The expression levels of MHC-I and MHC-II molecules as well as the percentages of both CD4(+) and CD8(+) T cells in mice vaccinated with pVAX-EF-1 alpha were significantly increased (p < 0.05), compared with those in all the mice from control groups (blank control, PBS, and pVAXI). Immunization with pVAX-EF-1 alpha significantly (p < 0.05) prolonged mouse survival time to 14.1 +/- 1.7 days after challenge infection with the virulent T. gondii RH strain, compared with mice in the control groups which died within 8 days. Conclusions: DNA vaccination with pVAX-EF-1 alpha triggered strong humoral and cellular responses and induced effective protection in mice against acute T. gondii infection, indicating that TgEF-1 alpha is a promising vaccine candidate against acute toxoplasmosis.