THE B-CELL EPITOPE OF PARAMYOSIN RECOGNIZED BY A PROTECTIVE MONOCLONAL IGE ANTIBODY TO SCHISTOSOMA-JAPONICUM

Passive immunization of mice with a monoclonal IgE antibody to Schisto soma japonicum (SJ18 epsilon.1) induces significant protection to a ch allenge infection and the target molecule of SJ18 epsilon.1 is paramyo sin. In the present study, we demonstrate the B cell epitope of paramy osin recognized by SJ18 epsilon.1 by using a series of deletion mutant s expressed in Escherichia coli SJ18 epsilon.1 reacted with the recomb inant paramyosin containing 113 amino acids (Glu(301)-Ala(413)) but no t with a shorter peptide (Glu(301)-Asp(343)). Further epitope mapping carried out by a multi-pin system using heptameric peptides synthesize d sequentially from 71 amino acids of paramyosin (Asp(343)-Ala(413)) d emonstrated significant binding of SJ18 epsilon.1 to the sequence, (35 9)Ile-Arg-Arg-Ala(362). Replacement set analysis of the pentameric pep tide, (358)Leu-Ile-Arg-Arg-Ala(362), revealed that replacement of each residue with a hydrophobic or hydrophilic amino acid did not inhibit binding of SJ18 epsilon.1, whereas replacement of positively charged A rg, or hydrophobic Ala with a charged amino acid, Glu, showed reductio n in binding of the antibody. Moreover, replacement of each amino acid including Arg with a positively charged amino acid, Lys, resulted in a drastic loss of the binding, indicating that binding of the antibody was markedly affected by the change of charges of the peptide as well as by the conformational alteration. The target epitope of SJ18 epsil on.1 was common among paramyosins of S. mansoni, Taenia solium and Ech inococcus granulosus but not among nematode paramyosins, suggesting th at the epitope is specific for platyhelminthes. Copyright (C) 1997 Els evier Science Ltd.