Mecanismos de proteção induzidos pela imunização com TgHSP70 e de controle da inflamação pelo tratamento com STAg na infecção por Toxoplasma gondii

Abstract

Toxoplasma gondii is an obligatory protozoan parasite that present several antigens capable of activating immune responses. In this work, we aimed to study two immunomodulatory antigens in pre-treatment for acute and immunization for chronic infection. The first was to evaluate the role of soluble tachyzoite antigen (STAg) on epithelial cells to control intestinal inflammation during acute infection. It was demonstrated STAg treatment was able to preserve Paneth cell numbers during infection, and to maintain epithelial integrity and function. We also observed that STAg treated and infected C57BL/6 mice produce secretory IgA against pathogenic bacteria, controlling microbiota and diminishing intestinal inflammation. The second objective was to evaluate the role of T. gondii heat shock protein of 70 kDa (TgHSP70) as a vaccinal antigen in murine chronic infection. It was observed that immunization with alum-adsorbed TgHSP70 reduced cyst numbers and diminished inflammation in the brain, and also induced high titers of TgHSP70-specific antibodies. We demonstrated that these antibodies do not act directly on the parasite, but seem to neutralize free TgHSP70 that induce nitric oxide production in RAW264.7 cells. In summary, this work demonstrated action mechanisms of two T. gondii immunomodulatory antigens, STAg and TgHSP70, and strengthens the use of these antigens as tools for vaccination or pre-treatment in order to control infection and intestinal inflammation.