A DOMINANT B-CELL EPITOPE ON THE 22 KDA TEGUMENTAL MEMBRANE-ASSOCIATED ANTIGEN OF SCHISTOSOMA-JAPONICUM MAPS TO AN EF-HAND CALCIUM-BINDING DOMAIN

The 22 kDA tegumental surface membrane-associated antigen of schistoso mes is of recognized importance in immunity to schistosomiasis. Here, we have defined linear B-cell epitopes on the recently cloned and expr essed recombinant Schistosoma japonicum 22 kDa antigen (reSj22), using mice immunized with this molecule. Sera from three strains of mice, C BA, c57BL/6 and BALB/c, representing different genetic backgrounds, we re reacted with a series of overlapping synthetic peptides in epitope- scanning studies. The predicted hydrophilic N-terminal domain was foun d to be highly immunogenic, containing several sequences that were str ongly recognized by all strains of mice. The most dominant epitope ide ntified, corresponding to peptide 6, was located in a region previousl y identified as an EF-hand calcium binding domain. In contrast, the mo re hydrophobic C-terminal region of the molecule was poorly recognized , with the exception of a single peptide encoding residues 121-140 tha t was recognized by CBA and C57BL/6 but not BALB/c mice, suggesting th at the latter epitope was genetically restricted between the strains. The data presented here describing the epitope mapping of this molecul e may prove important in research aimed at further defining immune res ponses to schistosomal antigens.