B-cell epitopes recognized by Chinese water buffaloes (Bos buffelus) on the 22 kDa tegumental membrane-associated antigen (Sj-22) of the Asiatic bloodfluke, Schistosoma japonicum.

The 22.6 kDa tegumental membrane-associated antigen of schistosomes is of recognized importance in immunity to schistosomiasis. In China, bovines are known to play an important role in the transmission of Schistosoma japonicum. Ten buffaloes (Bos buffelus) were vaccinated with a recombinant form (reSj-22) of the S. japonicum 22.6 kDa tegumental antigen (Sj-22) and the sera were used to identify and map possible linear B-cell epitopes on this molecule using a series of 18 overlapping synthetic peptides (P1-P18). Sera from all of the ten vaccinated buffaloes reacted strongly with Sj-22 in western blots and in ELISA, while sera from a further ten adjuvant (Quil A) control buffaloes did not. Four peptides (P3, P8, P9 and P10) were predominantly recognized by at least 90% of the buffalo sera. This pattern of recognition is similar to that obtained in a previous study we undertook in mice immunized with the same antigen whereby peptides 3, 8, 9 and 10 were recognized by over 80% of CBA strain mice. The peptide most frequently recognized by mice (peptide 6), and mapping to an EF-hand calcium binding domain, was recognized by six of the ten vaccinated buffaloes. The major difference between buffaloes and mice occurred with peptide 1 which was recognized very frequently by all three strains of mice tested but was only weakly recognized by three of the ten buffaloes. This study provides a valuable reference for further study on the immunity stimulated by the 22.6 kDa tegumental antigen in the murine model and a natural bovine host of Schistosomiasis japonica.