Evaluation of Immunogenic Effect of Toxoplasma gondii RecombinantSAG-1 Antigen with Propranolol as Adjuvant in BALB/c Mice

Abstract

Purpose: Propranolol as a novel adjuvant, was used to evaluate the immunogenic effect of threedoses of recombinant SAG-1 (rSAG-1) antigen of Toxoplasma gondii in BALB/c mice for findingthe optimal dose, and was compared with efficacy of tachyzoite lysate antigen (TLA).Methods: Eight different groups of 15 BALB/c mice received different volumes of theimmunogenic material (three doses of r SAG-1 and one dose of TLA antigens), with or withoutpropranolol adjuvant, subcutaneously. The control group mice received only PBS. Three weeksafter the last immunization, the serum levels of IgG2a, IgG1 and IgG total antibodies againstTLA, splenic interleukin-5 (IL-5) and Interferon-gamma (IFN-γ) (produced against TLA) and thesplenic lymphocyte proliferation after adding TLA were measured to evaluate humoral andcellular immune responses. Challenge test was performed by subcutaneously injection of 1000alive and active tachyzoites in to five mice per each group and survival days for each group ofmice were recorded.Results: The mice group that received propranolol adjuvant and 20 μg of r SAG-1 antigenper dose of injection showed significantly more IFN-γ production, more proliferation ofsplenic lymphocytes and higher anti-TLA-specific IgG2a production (three main indexes forcell mediated immunity) in comparison with other groups. Moreover, in the challenge test,this group of mice had a significantly increased survival time, indicating the positive effect ofpropranolol in the more stimulating of cellular immunity that is necessary for toxoplasmosisprevention or suppress.Conclusion: Our results showed that T. gondii rSAG-1 antigen in combination with propranololas adjuvant (which can induce Th1 related responses) are good candidates for further study toa vaccine design.<br />