Evaluation of Anti-Toxoplasma gondii Immune Responses in BALB/c Mice Induced by DNA Vaccines Encoding Surface Antigen 1 (SAG1) and 3 (SAG3)

Abstract

DNA vaccine cocktail construction is one of the most important strategies for the development of new generation multiantigenic vaccine against toxoplasmosis. In the present study DNA cocktail vaccines containing SAG1 and SAG3 (from a native Iranian parasite, AN: JF312642) genes were constructed and their immune response and protective efficacy was evaluated in comparison with control groups in BALB/c mice. For this purpose, the plasmids containing complete SAG3, SAG1 genes were constructed and then the recombinant plasmids were administered via intramuscular injections according to immunized mice three times with three-week intervals. Both alum and MMT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) were used as an adjuvant to enhance the immune response. Both humeral and cellular immune response of the mice groups were evaluation. Finally, the mice in immunized and non-immunized groups were inoculated by the parasite and the mortality of the mice was evaluated on a daily basis. In cytokine assay, the INFγ were found higher in the mice that received the cocktail DNA containing recombinant plasmids. Evaluation of proliferation of splenocytes using the Alum and nano adjuvant MMT assay indicated induction of cellular response. Measurement of total IgG and the isotypes of IgG1 and IgG2a showed that the cocktail DNA stimulated IgG and IgG2a production in comparison with the control groups (P < 0.05). Furthermore, the survival rate of mice in the groups that received the cocktail DNA was significantly higher than that in the control groups (P < 0.05). Accordingly, administration of the cocktail DNA vaccine led to production of higher levels of IFNγ, confirmed by secretion of IgG2a, and the immune response was shifted toward Th1. Thus, the cocktail DNA containing the recombinant plasmids can be an appropriate candidate for immunization against toxoplasmosis.