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

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-gamma were estimated using the commercially available bovine IFN-gamma test kit (Bovigam, Prionics AG). Results: Administration of the recombinant GRA1 enhanced both IFN-gamma production from peripheral blood cells when cultured in vitro with Toxoplasma antigen, and GRA1-specific IgG2 antibody level present in serum. Unlike GRAI SAG1 did not stimulate IFN-gamma 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. (C) 2017 Elsevier B.V. All rights reserved.