Abstract

Toxoplasmosis is a zoonotic disease caused by the protozoan Toxoplasma gondii, which infects humans and most warm-blooded animals throughout the world. Although human toxoplasmosis in healthy adults is usually asymptomatic, a serious disease can occur in the case of congenital infection and immunocompromised individuals. Among food animals, sheep, along with goats and pigs, possess the highest incidence of T. gondii cysts in meat, and play a major role as a source of human infection. Moreover, prevention and control of T. gondii infection is of economic importance in sheep production, because it also causes abortions and neonatal deaths of sheep. The diagnosis of toxoplasmosis in sheep is usually based on the detection of specific antibodies. Most commercial kits use prepared tachyzoites grown in mice or tissue culture to prepare Toxoplasma lysate antigen (TLA) for antibody detection. These antigens may contain varying amounts of host material and therefore affect the specificity and reproducibility of the test results. The use of recombinant antigens could avoid these drawbacks and permit the development of an improved diagnostic test. This study is the first evaluation of the use of T. gondii MIC1-MAG1-SAG1 recombinant chimeric antigen for the serodiagnosis of ovine toxoplasmosis. Previously, this recombinant protein has been successfully used for detection of T. gondii infection in humans (1). The diagnostic efficiency of MIC1-MAG1-SAG1 antigen was assessed in IgG ELISA test with the use of 150 reference sheep sera (100 seropositive and 50 seronegative) previously tested using a commercial agglutination test (Toxo-ScreenDA, bioMérieux). The results obtained for chimeric antigen were compared with those of IgG ELISAs using a TLA and a combination of three recombinant antigens (MIC1+MAG1+SAG1). The sensitivity of the IgG ELISA calculated from all of the positive serum samples was the same for the chimeric antigen and the TLA (100%), whereas the sensitivity of the mixture of recombinant proteins used were definitely lower (78%). Therefore, the present study shows that the MIC1-MAG1-SAG1 chimeric antigen is a very useful tool for the detection of anti-T. gondii IgG antibodies in sheep sera, giving far better results than a mixture of three antigens.

Authors (2)