A Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 Homologue Plays a Pivotal Role in Nontypeable Haemophilus influenzae Colonization of the Chinchilla Nasopharynx via the Outer Membrane Protein P5-Homologous Adhesin

Abstract

In vitro studies suggest an important role for CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1) in infection by multiple gram-negative bacteria. However, in vivo evidence supporting this role is lacking, largely because the bacterial adhesins involved in this host-microbe association do not bind to murine-derived CEACAM1. One of several adhesins expressed by nontypeable Haemophilus influenzae (NTHI), the outer membrane protein P5-homologous adhesin (or P5), is essential for colonization of the chinchilla nasopharynx and infection of the middle ear. Here we reveal that NTHI P5 binds to the chinchilla homologue of CEACAM1 and that rabbit anti-human carcinoembryonic antigen blocks NTHI colonization of the chinchilla nasopharynx, providing the first demonstration of a role for CEACAM receptor binding by any bacterial pathogen in vivo.The carcinoembryonic antigen-related cellular adhesion molecules (CEACAMs) are a subset of the immunoglobulin superfamily that mediate intercellular binding by homophilic and heterophilic interactions which influence a variety of normal and pathogenic processes, cellular growth, differentiation, and activation (reviewed in references 13, 16, 25, and 35). In vitro studies from several laboratories have now clearly established that adhesins expressed by a variety of important human-restricted bacterial pathogens bind specific members of the CEACAM family. For example, the evolutionarily unrelated colony opacity-associated (Opa) family of adhesins expressed by pathogenic and commensal Neisseria spp. (8, 10-12, 14, 15, 51-53), the Haemophilus influenzae outer membrane protein (OMP) P5 (20), and the Moraxella catarrhalis ubiquitous surface protein UspA1 (21) each bind CEACAMs. This interaction appears to mediate both attachment and engulfment of the bound bacteria by CEACAM-expressing epithelia (52, 54), endothelia (33, 34), and phagocytes (10,14,29,46,47,52). In the context of the epithelia, polarized monolayers of epithelia express CEACAM1, CEACAM5, and CEACAM6 on the apical surface and at cell-cell junctions (49, 54). Bacterial binding to these receptors is sufficient to mediate apical adherence and transcellular transcytosis across the monolayers, allowing the bacteria to emerge in the subepithelial spaces (54). Bacterial binding to CEACAM1 also causes the direct suppression of immune cell activity due to the coinhibitory function of CEACAM1 (9). While these studies suggest an essential role for CEACAM binding in host colonization and persistence, the exquisite specificity of the protein-protein interactions mediated by each of these adhesins has so far prevented their contribution to infection from being addressed in vivo.We previously demonstrated that nontypeable H. influenzae (NTHI) effectively colonizes the upper respiratory tract (URT) of chinchillas and that when this rodent host is also coinfected with a common human URT virus, NTHI can induce culturepositive otitis media (or middle ear infection) via a process that closely reflects the disease course in human...

Outer Membrane Protein P5 Is Required for Resistance of Nontypeable Haemophilus influenzae to Both the Classical and Alternative Complement Pathways

“…Previously, P5 was implicated in the pathogenesis of H. influenzae as an adherence factor for attachment of H. influenzae to host mucosal structures (42)(43)(44)(45)(46). The work presented here describes new functional roles for this abundant outer membrane protein, including limiting the binding of IgM to the bacterial surface and participating in the binding of fH.…”

“…Bioinformatic identification of putative DsbA substrates revealed a subset with potential roles in complement resistance (35); the outer membrane protein P5 was selected from this list as a candidate because it is ϳ50% identical to Escherichia coli outer membrane protein A (OmpA) (36), a factor previously shown to be important for complement resistance in E. coli (37)(38)(39). NTHi P5, a ␤-barrel protein with eight predicted transmembrane spans, four outer surface loops (40), and a predicted disulfide between C323 and C335, was shown to be required for virulence in a chinchilla ear infection model (41) and has also been implicated in adhesion of H. influenzae to various mucosal surface structures (42)(43)(44)(45)(46). However, a role for P5 in complement resistance has not been previously reported.…”

Transcutaneous Immunization with a Band-Aid Prevents Experimental Otitis Media in a Polymicrobial Model

“…Moreover, protection against experimental OM afforded by immunization with rsPilA, chimV4, and IHF was consistent with our understanding of the functions of NTHI OMP P5, Tfp, and IHF in bacterial adherence, pathobiology, and biofilm formation. For example, NTHI Tfp engages ICAM-1, and OMP P5 engages both ICAM-1 and CEACAM-1, molecules whose expression levels on respiratory tract epithelial cells are increased in response to respiratory tract viral infection, including adenovirus (33)(34)(35). Moreover, Tfp and OMP P5 are essential for NTHI to adhere to the mucosal surface.…”

Temporal upregulation of host surface receptors provides a window of opportunity for bacterial adhesion and disease

“…Also, NTHi adherence to A549 alveolar epithelial cells in vitro was shown to be inhibited in a dose-dependent manner with increasing concentrations of anti-ICAM-1 monoclonal antibodies [52]. An in vivo study conducted in chinchillas reported that anti-CEACAM-1 antibody YTH71.3 effectively blocked NTHi attachment to the nasopharynx [108].…”