Studies on immunoprophylactic potential of recombinant mature surface antigen 2 (rSAG2) protein against Toxoplasma gondii infection^†

The immunoprophylactic potential of recombinant mature surface antigen 2 (rSAG2) protein and the whole cell lysate antigen (TLA) of Toxoplasma gondii were assessed by cytokine profiling and assaying the humoral immune responses in mouse model. Profiles of a selected group of cytokines, viz., IL-4, IL-5, IL-10, IFN-γ and TNF-α were studied using sandwich ELISA, while the humoral response was assessed by measuring the serum IgG, IgG₁ and IgG_2a profiles. Following live challenge with T. gondii tachyzoites, the level of IFN- γ was found to increase significantly (1.5 to 2.0-fold) in vaccinated groups while the levels of IL-4 (4.0 to 6.0-fold), IL-5 (2.5 to 3.0-fold), IL-10 (2.5 to 45.0-fold) and TNF- α (1.5 to 1.8-fold) were significantly higher in control group. The IgG response was significantly higher (P<0.05) in immunized groups in comparison to the controls. The IgG₁ and IgG_2a sub-classes were also higher in the immunized group. However, decline in IgG_2a response was observed in rSAG2 as well as TLA immunized mice. Immunization with recombinant protein as immunogen, while resulting in a marginal increase in the survival period of the immunized mice did not confer total protection.