Identification of B-cell epitopes in urease B subunit of Helicobacter pylori bound by neutralizing antibodies.

To identify linear B-cell epitopes of urease B (UreB), a series of 19 partially overlapping fragments of the UreB gene were expressed. Three MAbs against UreB of Helicobacter pylori (H. pylori), A1H10, A3C10, and B3D9, were tested for their reactivity to the truncated proteins by Western blot and enzyme-linked immunosorbent assay (ELISA). Three linear B-cell epitopes were identified covering a stretch of 15 amino acid (aa) residues and localized in the aa regions 158-172, 181-195, and 349-363 of UreB. ELISA also showed that the three synthetic peptides containing epitope sequences (UP32: GGGTGPADGTNATTI, UP35: WMLRAAEEYSMNLGF, and UP38: TLHDMGIFSITSSDS) were recognized by the corresponding MAbs and H. pylori positive sera from H. pylori infected patients. Mice immunized with glutathione S-transferase (GST) fusion peptides showed that epitope-specific antibodies were capable of inhibiting urease enzymatic activity. These results should be useful in clinical applications and highlight the potential importance of these epitopes as the targets for development of epitope-based vaccines against H. pylori.