Biochemical characterization and localization of Fasciola hepatica 26-28 kDa diagnostic coproantigen

We have previously reported the usefulness of a 26-28 kDa coproantigen of F asciola hepatica for diagnosis of infection, In this study, the 26-28 kDa c oproantigen was biochemically characterized with the aid of monoclonal anti bodies (MoAb) in an effort to better understand the biology of the antigen. Differential staining of chromatographically-purified 26-28 kDa coproantig en on SDS-PAGE, under reducing and nan-reducing conditions indicated that t he coproantigen was a monomeric, highly glycosylated glycoprotein. Alkaline treatment of the purified coproantigen resulted in an 8 kDa protein core w hich still contained the epitope recognized by the MoAb. No protease activi ty was associated with the 26-28 kDa coproantigen. The coproantigen could b e cleaved by trypsin without altering the reactive epitope recognized by th e MoAb, but was resistant to pepsin digestion. Further, the coproantigen wa s stable under several different storage conditions. Indirect immunofluores cence on tissue sections of adult flukes indicated that the coproantigen wa s present in gut cells and tegument, Taken together these results confirm t he stability of the 26-28 kDa coproantigen and its usefulness in diagnostic tests for F. hepatica infections.