An evaluation of antigen B family of Echinococcus granulosus, its conformational propensity and elucidation of the agretope.

The present communication evaluates the antigen B (AgB) family of bubaline isolates of Echinococcus granulosus with respect to their conformational propensity and also discusses the stretches of agretope. AgB, which is abundantly present in hydatid cyst fluid, is encoded by a gene family, AgB1-AgB5. Hydatidosis is of zoonotic and economic importance in India. Buffaloes serve as the intermediate host. However, to date the AgB family has not been fully analysed. During the present study two different primers used for amplification of AgB1 revealed homology to Echinococcus canadensis (G8) as well as E. granulosus sensu stricto (G1/G2). The sequence of AgB3 is homologous to that of the well-defined species, Echinococcus ortleppi (G5), and the predicted amino acid sequence of AgB4 is homologous to bovine isolates identified earlier. alpha- and beta-amphipathic structures were recorded in all the antigens designated as T-cell receptor sites. The antigenic index of different stretches correlated with hydrophilicity because the hydrophobic residues are not accessible to the cells. In this study, we investigated the binding propensity of AgB to MHC II in order to determine stretches of agretope. Agretopes began with four hydrophilic residues. Two to three additional hydrophilic residues were present in the internal motif. This comparison of AgB and its family of bubaline isolates, with respect to their sequence information, alpha- and beta- amphipathic regions, antigenic index and stretches of agretope is the first such report from India.