Neutralizing antibodies for Helicobacter pylori urease inhibit bacterial colonization in the murine stomach in vivo.

Helicobacter pylori (H. pylori) urease is a key protein for persistent infection of the bacteria in the stomach. Although H. pylori generally induce anti-H. pylori-specific antibodies (Abs), these Abs do not usually work for eradication or prevention of the H. pylori infection. In our previous study, we identified a linear epitope composed of 19-mer peptides termed UB-33, CHHLDKSIKEDVQFADSRI, within the large subunit of H. pylori urease. Anti-UB-33-specific Abs neutralized the enzymatic activity of H. pylori urease in vitro. In the present study, we evaluated the effect of immunization of BALB/c mice with H. pylori UB-33 peptide. After confirming the production of anti-UB-33-specific Abs, mice were challenged orally with H. pylori Sydney Strain-1 (SS-1). Mice producing anti-UB-33-specific Abs were not infected with SS-1, and the amount of SS-1 isolate in their stomach was significantly reduced. Also, the urease-negative mutant of H. pylori, HPP1801, did not colonize in the stomach, indicating that H. pylori urease was a critical element for infection of H. pylori in the gastric mucosa. Moreover, mice producing UB-33-specific Abs apparently suppressed H. pylori infection in the stomach where anti-UB-33 Abs were secreted in the gastric juice, indicating that H. pylori colonization was inhibited in the presence of anti-UB-33 Abs. In addition, the neutralization activity of sera from mice immunized with purified urease was less potent than that in the sera from mice immunized with UB-33. Furthermore, the recognition of epitope UB-33 was mediated through Toll-like receptor 2 (TLR2) on the B-1 cells using TLR2-knockout BALB/c mice in vivo. These results indicate that liner peptide UB-33 should be used for immunization to induce neutralizing Abs instead of purified H. pylori urease to prevent H. pylori infection and their colonization in the stomach.