Identification of two new Helicobacter pylori surface proteins involved in attachment to epithelial cell lines

Helicobacter pylori causes the development of gastritis, gastric ulcers and adenocarcinomas in humans. The establishment of infection is influenced by adherence to the gastric epithelium, and several bacterial adhesins and host cell receptors have been identified. H. pylori recognize the Lewis(b) receptor through the BabA adhesin but also readily adhere to epithelia in the absence of the Lewis(b) epitope, demonstrating the relevance of additional adhesive interactions. This study presents a novel method of identifying bacterial adhesins. Nickel beads were coated with H. pylori-derived, recombinantly expressed ORF proteins, and epithelial cells from the human stomach, intestine or urinary tract were allowed to adhere to those beads. The binding of epithelial cells to the protein-coated nickel beads was confirmed by electron microscopy or flow cytometry using antibodies directed towards the His-tags. Among the five ORFs tested, two new adhesive proteins (HP1188 and HP1430) were identified. Both were expressed on the surface of virulent H. pylori, with the HP1188 protein being most abundant. The purified HP1188 and HP1430 proteins bound more strongly to gastric than to other epithelial cell lines, suggesting that they may be involved in the colonization of the human gastric mucosa. In conclusion, this method facilitates the identification of ORFs of microbial origin involved in cellular interactions such as adherence.