Toxoplasma gondii: Immunological response of sheep to injections of recombinant SAG1, SAG2, GRA1 proteins coupled to the non-toxic microparticle muramyl dipeptide

Abstract Background Toxoplasma gondii is an important cause of reproductive loss in sheep and has a large economic impact, worldwide, because of infections in humans and animals. The immune response in sheep was evaluated, following administration with four different combinations of recombinant proteins derived from T. gondii. Methods 25 three-year-old non-pregnant Coopworth ewes were vaccinated twice by intramuscular injection with either the recombinant surface antigen 1 (SAG1), 2 (SAG2) or excretory/secretory antigen (GRA1) each individually conjugated to non-toxic muramyl dipeptide (MDP). Blood samples were collected from all animals prior to the first injection and once per week until five weeks after the second injection. Immunoglobulins (Ig) G1 and IgG2 level were measured using an ELISA test. IFN-γ were estimated using the commercially available bovine IFN-gamma test kit (Bovigam, Prionics AG). Results Administration of the recombinant GRA1 enhanced both IFN-γ production from peripheral blood cells when cultured in vitro with Toxoplasma antigen, and GRA1-specific IgG2 antibody level present in serum. Unlike GRA1 SAG1 did not stimulate IFN-γ production in the same test system. Conclusion These results indicate the potential of recombinant GRA1, as a vaccine candidate to protect sheep against T. gondii infection.