Development of an enzyme immunoassay using recombinant invariant surface glycoprotein (rISG) 75 for serodiagnosis of bovine trypanosomosis.

Trypanosomosis or surra is caused by the haemoflagellate parasite, Trypanosoma evansi and is an important disease of animals, including domestic and wild herbivores and carnivores, in tropical countries. The invariant surface glycoproteins (ISGs) are blood stream stage specific and are uniformly distributed over the entire surface of the trypanosomes. In the present study, the extracellular domain (ED) region of ISG-75 from T. evansi, consisting of 1320 nt, encoding a polypeptide of 440 amino acids, has been heterologously expressed in Escherichia coli. Further, the immunoreactivity of recombinant ISG-75 (rISG-75) was characterized in immunoblot and ELISA using T. evansi hyper immune sera raised in experimental animals. The protein was found immunoreactive when compared with a panel of antigens (VSG RoTat 1.2 and whole cell lysate) using bovine serum samples from field. The diagnostic potential of rISG-75 was evaluated in ELISA with large number of bovine field serum samples. The optimum sensitivity and specificity were 98.47 and 99.1, respectively. The present finding showed that the expressed protein has potential use in the serodiagnosis of trypanosomosis.