Galβ1-6Gal, antigenic epitope which accounts for serological cross-reaction in diagnosis of Echinococcus multilocularis infection

Parasitic helminths express various antigenic carbohydrates, which often account for serological cross-reactions. In serodiagnosis, it is essential to inspect cross-reactivity between the target parasite and other parasites in order to assess diagnostic performance. Our previous study showed that the Galβ1-6Gal sequence was a common epitope between Echinococcus multilocularis (Em) and E. granulosus (Eg). Furthermore, compounds with this sequence from Fasciola hepatica (Fh) reportedly were recognized by sera with Eg infection. Our aim is to investigate whether this sequence is one of the widely common epitopes in many kinds of parasites. For various parasites, sera with Fh infection cross-reacted at the highest frequency (71·4%) against Em antigen. In patients with other parasitic infections, sera showed cross-reactions against Fh antigen bound to Em antigen with a high frequency (23·7%). Binding inhibition tests with commercial Galβ1-6Gal disaccharide showed that Galβ1-6Gal was the common epitope between not only Em, Eg and Fh, but also between various other parasites. Furthermore, the presence of the Galβ1-6Gal epitope in Em antigen was confirmed by immunoblot testing with the specific antibody for this sequence. This study showed that the Galβ1-6Gal sequence is one of the antigenic epitopes that accounts for serological cross-reactivity between Em and various other parasites.