Tandem repeat protein as potential diagnostic antigen for Trypanosoma evansi infection

Trypanosoma evansi infection (surra) causes significant losses in livestock production in tropical and sub-tropical areas. The current ELISA recommended by OIE for diagnosis of the disease is based on trypanosome lysate antigen. However, antigenic variation and unstable nature of cell lysate antigen make it difficult to standardize the assay. Thus, there are needs to develop recombinant antigen-based ELISA that improve stability, sensitivity, and specificity of the test. Since tandem repeat (TR) proteins of trypanosomatid parasites generally possess high antigenicity, they have been considered to be the promising antigens for trypanosomosis and leishmaniosis. In this study, IgG responses against 14 recombinant TR proteins of trypanosomes were examined by ELISA. Serum samples were obtained from three water buffaloes experimentally infected with T. evansi. Since Trypanosoma congolense GM6 (TcoGM6) elicited highest IgG responses to all water buffaloes, we further bioinformatically and molecular biologically identified Trypanosoma brucei brucei GM6 (TbbGM6) and T. evansi GM6 (TeGM6) TR genes, respectively. As expected, predicted amino acid sequences of TbbGM6 and TeGM6 were identical while the nucleic acid sequence homology between TbbGM6 and TcoGM6 was 63.8%. All buffaloes became clearly positive in recombinant TbbGM6 (rTbbGM6)-based ELISA at 48 days post-infection, suggesting that rTbbGM6 is usable as a serodiagnostic antigen for chronic T. evansi infection.