Molecular Cloning of aBacteroides caccaeTonB-Linked Outer Membrane Protein Identified by an Inflammatory Bowel Disease Marker Antibody

Abstract

Commensal enteric bacteria are a required pathogenic factor in inflammatory bowel disease (IBD), but the identity of the pertinent bacterial species is unresolved. Using an IBD-associated pANCA monoclonal antibody, a 100-kDa protein was recently characterized from an IBD clinical isolate of Bacteroides caccae (p2Lc3). In this study, consensus oligonucleotides were designed from 100-kDa peptides and used to identify a single-copy gene from the p2Lc3 genome. Sequence analysis of the genomic clone revealed a 2,844-bp (948 amino acid) open reading frame encoding features typical of the TonB-linked outer membrane protein family. This gene, termed ompW, was detected by Southern analysis only in B. caccae and was absent in other species of Bacteroides and gram-negative coliforms. The closest homologues of OmpW included the outer membrane proteins SusC of Bacteroides thetaiotaomicron and RagA of Porphyromonas gingivalis. Recombinant OmpW protein was immunoreactive with the monoclonal antibody, and serum anti-OmpW immunoglobulin A levels were elevated in a Crohn's disease patient subset. These findings suggest that OmpW may be a target of the IBD-associated immune response and reveal its structural relationship to a bacterial virulence factor of P. gingivalis and periodontal disease.Human inflammatory bowel disease (IBD) represents a set of a chronic, relapsing, and remitting intestinal inflammatory disorders involving T-cell-mediated mucosal and mural destruction and polygenic familial susceptibility (34,35). Several spontaneous and transgenic mouse strains have been established with susceptibility for chronic colitis similar to human IBD (4,5,18,20,26,32). In all evaluated models, normal resident enteric bacteria were found to be required for disease pathogenesis (13,27,40). Similarly, in human IBD several lines of evidence implicate enteric bacteria as a pathogenic factor in clinical disease, particularly in Crohn's disease (CD) (3,33,48).Immunologic studies have demonstrated that antibody and T-cell reactivity to commensal enteric bacteria is a distinguishing feature of colitic mouse strains (6, 10). However, the bacterial species and antigens recognized by colitigenic T cells have not yet been defined. Moreover, monoassociation studies have not yet revealed pathogenic bacterial species for colitisprone mouse strains (27). A systematic approach to this issue is hampered by the limited understanding of gastrointestinal microflora ecosystem. In addition, immune recognition of this commensal microflora in normal individuals is attenuated or undetectable. Accordingly, it has been difficult to highlight bacterial species or antigens for evaluation in IBD pathogenesis.Marker antibodies have been used successfully to identify disease-relevant antigenic targets in several immune-mediated diseases (38,45). In IBD, approximately 60 to 70% of ulcerative colitis (UC) patients and 25% of CD patients have elevated levels of pANCA, an antineutrophil cytoplasmic antibody with distinctive morphological and antigenic fine specificity ...

Intestinal microbiota contributes to individual susceptibility to alcoholic liver disease

“…Several OTUs correspond to bacterial species associated with inflammatory diseases or insulin resistance, including Bilophila wadsworthia, 16 Bacteroides caccae 17 or Escherichia coli. 18 Moreover, 21 belonged to the Lachnospiraceae family, which is increased in alcoholic patients with high gut permeability 9.…”

DLG5 R30Q Is Not Associated With IBD in Hungarian IBD Patients but Predicts Clinical Response to Steroids in Crohn's Disease

“…Our preliminary studies in mice have also brought evidence of the role of P fluorescens in the pathogenesis of IBD (S.I. 15 Furthermore, several studies have provided evidence of seroreactivity against Saccharomyces cerevisiae in adult and pediatric series. I2-expressing bacteria are localized in mucosal lesions in humans with CD, and the I2-encoded protein is the target of a disease-associated antibody.…”

“…pANCAs in IBD have been shown to be reactive with determinants of E coli, B caccae, and mycobacteria. 15 In experimental animal models, it has been demonstrated that anaerobic bacteria present in the colonic flora can cause deep colonic lesions and induce a severe inflammatory response when the mucosal barrier is broken. Anti-OmpC antibodies have been detected in 24% of children with CD and 11% of children with UC.…”

Early Microbial Markers of Celiac Disease

“…The cut-off level for positivity was set at 0.5 for I2 and 0.6 (children) and 1.0 (adults) for OmpW. 39 …”