Adhesin Receptors for Helicobacter pylori in the Salivary Proteome

Because gastric infection by Helicobacter pylori presumably takes place via the oral route, possible interactions with proteins in human saliva could influence the adhesion of this bacterium. Objectives: By using a combination of modified far Western analyses based on bacterial overlay and proteomics techniques, binding of H. pylori adhesins BabA and SabA to an extensive range of salivary proteins was investigated. Methods: Proteins of human whole saliva and glandular secretions were separated by one-dimensional and two-dimensional gel electrophoresis and transferred onto nitrocellulose membranes. Binding of H. pylori strain J99 to transferred salivary proteins was detected with fluorescence-labeled H. pylori bacterial cells. Potential salivary receptor molecules were identified by matrix-assisted laser desorption/ionization mass spectrometry and by comparison to previously established proteome maps of whole and glandular salivas. Results: By use of isogenic adhesin-deficient mutants, binding of H. pylori to MUC7 and gp-340 was attributed to the SabA and BabA adhesins, respectively, whereas binding to MUC5B involved both adhesins. Binding of H. pylori to the proline-rich glycoprotein was newly detected and assigned to the BabA adhesin whereas the SabA adhesin was found responsible for binding to novel receptor molecules, including carbonic anhydrase VI, secretory component and heavy chain of secretory IgA1, parotid secretory protein and zinc-a2-glycoprotein. Conclusions: Interactions between H. pylori surface adhesins and these salivary receptors may modify the adhesive or surface properties of this organism. This two-dimensional overlay technique represents an useful approach to adhesion studies of bacteria with complex protein mixtures.