Evaluation of immunogenicity and protective effect of DNA vaccine encoding surface antigen1 (SAG1) of Toxoplasma gondii and TLR-5 ligand as a genetic adjuvant against acute toxoplasmosis in BALB/c mice.

AIMS: Toxoplasma gondii is an obligate intracellular, protozoan that causes a high incidence of serious zoonotic parasitic disease in humans. In the present study the immune-protective efficacy of a DNA vaccine encoding SAG1 in combination with a gene sequence encoding FliC of Salmonella typhimurium (Toll-like receptor 5 agonist) was evaluated against acute T. gondii infection in mice.

METHODS AND

RESULTS

Ninety-nine female inbred BALB/c mice were divided into nine groups of 11 mice and were immunized intramuscularly three times at three-week intervals (days 0, 21 and 42) and challenged with virulent T. gondii RH strain 4 weeks later. The immunization of pVAX1-SAG1 administered with pVAX1-fliC in mice indicated specific humoral responses, with higher IgG antibody titers and a mixed IgG1/IgG2a response than in other groups (with a predominance of IgG2a over IgG2b and IgG1). Also, the cellular immune response elicited high levels of IFN-γ and IL-12 cytokines and low levels of IL-4 production compared to traditional adjuvants. Furthermore, the mice vaccinated with pVAX1-SAG1+pVAX1-fliC survived for slightly longer after the last immunization and challenge with the T. gondii.

CONCLUSION

This investigation indicated that cocktail DNA vaccine encoded SAG1 gene of T. gondii and FliC can protect against acute toxoplasmosis.