Regions important for the adhesin activity of <it>Moraxella catarrhalis </it>Hag

<p>Abstract</p> <p>Background</p> <p>The <it>Moraxella catarrhalis </it>Hag protein, an Oca autotransporter adhesin, has previously been shown to be important for adherence of this respiratory tract pathogen to human middle ear and A549 lung cells.</p> <p>Results</p> <p>The present study demonstrates that adherence of <it>M. catarrhalis </it>isogenic <it>hag </it>mutant strains to the human epithelial cell lines Chang (conjunctival) and NCIH292 (lung) is reduced by 50–93%. Furthermore, expressing Hag in a heterologous <it>Escherichia coli </it>background substantially increased the adherence of recombinant bacteria to NCIH292 cells and murine type IV collagen. Hag did not, however, increase the attachment of <it>E. coli </it>to Chang cells. These results indicate that Hag directly mediates adherence to NCIH292 lung cells and collagen, but is not sufficient to confer binding to conjunctival monolayers. Several in-frame deletions were engineered within the <it>hag </it>gene of <it>M. catarrhalis </it>strain O35E and the resulting proteins were tested for their ability to mediate binding to NCIH292 monolayers, middle ear cells, and type IV collagen. These experiments revealed that epithelial cell and collagen binding properties are separable, and that residues 385–705 of this ~2,000 amino acid protein are important for adherence to middle ear and NCIH292 cells. The region of O35E-Hag encompassing aa 706 to 1194 was also found to be required for adherence to collagen. In contrast, β-roll repeats present in Hag, which are structural features conserved in several Oca adhesins and responsible for the adhesive properties of <it>Yersinia enterocolitica </it>YadA, are not important for Hag-mediated adherence.</p> <p>Conclusion</p> <p>Hag is a major adherence factor for human cells derived from various anatomical sites relevant to pathogenesis by <it>M. catarrhalis </it>and its structure-function relationships differ from those of other, closely-related autotransporter proteins.</p>

Abstract licence: CC BY-NC-ND

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