The n-domain of the human CD66a adhesion molecule is a target for opa proteins of neisseria meningioitis and neisseria gonorrhoeae

Using Cos cells transfected with cDNAs encoding human cell surface adhesion molecules, we have identified human cellular receptors for meningococcal virulence-associated Opa proteins, which are expressed by the majority of disease and carrier isolates. These receptors belong to the Ig superfamily of adhesion molecules and are expressed on epithelial, endothelial and phagocytic cells. Using soluble chimaeric receptor molecules, we have demonstrated that meningococcal Opa proteins bind to the N-terminal domain of biliary glycoproteins or CD66a. Moreover, the Opa proteins of the related pathogen Neisseria gpnorrhoeae, responsible for urogenital infections, also interact with this receptor, making CD66a a common target for pathogenic neisseriae. Over 95% of Opa-expressing clinical and mucosal isolates of meningococci and gonococci were shown to bind to the CD66 N-terminal domain, demonstrating the presence of a conserved receptor-binding domain in the majority of neisserial Opa proteins. We have also investigated the roles of CD66 (carcinoembryonic antigen, CEA) family members expressed on human epithelial cells and neutrophils in adhesion mediated via Opa proteins. Using human colonie and lung epithelial cell lines known to express CD66 molecules, we have shown that these CD66 receptors are used by meningococci. The monoclonal antibody, YTH 71.3.2, against the N-terminal domain of CD66, but not3B10 against domain A1B1, inhibited meningococcal adhesion to host cells. When a capsulate bacteria expressing Opa proteins were used, large numbers of bacteria adhered to these epithelial cell lines and epithelial cells were invaded by Opa-expressing meningococci. Opa proteins on serogroup A strain C751 meningococci mediate non-opsonic domain of CD66. Thus, the Opa family of neisserial ligands may interact with several members of the CD66 family via their largely conserved N-terminal domains.