Changes in Binding Properties of  Helicobacter pylori Isolated over time from a Chronically Infected Patient

Abstract: Helicobacter pylori infects over 50 % of the world’s population, causing gastritis, and in some cases, peptic ulcer disease and gastric cancer. Adherence to the gastric surface occurs primarily through H. pylori outer membrane proteins (HOPs) and is essential for bacterial survival and establishment of infection. The Blood group Antigen-Binding Adhesin (BabA) is the best-characterized attachment protein, mediating adherence by binding to fucosylated carbohydrate structures on the surface of the gastric epithelium. H. pylori is highly adaptable to environmental changes that occur during stomach longterm infection, however little is known about the effect of such changes on the adaptability and functionality of BabA adherence properties. The aim of this study was to evaluate how BabA-mediated binding properties of H. pylori isolates were affected during 20 years of chronic infection. Two H. pylori clinical isolates collected from a single individual, 20 years apart were studied for their Leb-binding properties using a combination of radioimmunoassay (RIA) and in situ histo- and cytochemistry. Our results demonstrated that H. pylori isolated after 20 years of infection had lost its Lewis b binding ability due to a nucleotide deletion in the babA gene, resulting in a translational frame shift and hence, a non-functional BabA protein. We also showed that the non-adherent isolate contains sub-populations of bacteria that express BabA and have therefore maintained the ability to bind to Leb-conjugate and adhere to human gastric mucosa in vitro.   An additional adherence pattern was revealed when H. pylori bacterial cells were applied to human buccal epithelium cells (BEC), with all the isolates demonstrating attachment. These results suggest that H. pylori can express additional binding properties for adherence in the oral cavity which may contribute to re-infection as well as further transmission of the H. pylori infection.