DNA vaccination with genes encoding Toxoplasma gondii antigens ROP5 and GRA15 induces protective immunity against toxoplasmosis in Kunming mice.

OBJECTIVES

To evaluate the protective efficacy of a DNA vaccine encoding Toxoplasma gondii rhoptry protein 5 (ROP5) and GRA15 antigens.

METHODS

We constructed eukaryotic plasmids expressing pVAX-ROP5 and pVAX-GRA15, and measured the immune responses to these DNA vaccines.

RESULTS

Kunming mice immunized with pVAX-ROP5 or pVAX-GRA15 showed significantly increased serum IgG2a titers; Th1 responses association with the production of IFN-γ, IL-2, IL12 p40 and IL-12 p70; cell-mediated cytotoxic activity with increased frequencies of IFN-γ secreting CD8(+) T cells (CD8(+) IFN-γ+ T cells), as well as prolonged survival time (19.4 ± 4.9 days for ROP5; 17.8 ± 3.8 days for GRA15) and brain cyst reduction (57.4% for ROP5; 65.9% for GRA15) compared to control mice. Co-administration with pVAX-ROP5 and pVAX-GRA15 boosted the cellular and humoral immune responses, and significantly increased cyst reduction (79%) and prolonged the survival of immunized mice (22.7 ± 7.2 days).

CONCLUSION

Co-immunization of pVAX-ROP5 and pVAX-GRA15 increase the protective efficacy.