Use of defined mutants to assess the role of the Campylobacter rectus S-layer in bacterium-epithelial cell interactions.
Campylobacter rectus is a periodontal pathogen with a 150-kDa protein on its cell surface. This protein forms a paracrystalline lattice, called the S-layer, surrounding the outer membrane of this gram-negative bacterium. To initiate a genetic analysis of the possible role of the S-layer in the initial interaction of C. rectus with host epithelial cells, C. rectus strains lacking the S-layer protein gene (crsA) were constructed by allelic exchange mutagenesis. Surprisingly, the lack of the S-layer had only a minor effect on the interaction of C. rectus with HEp-2 epithelial cells; CrsA(+) cells were 30 to 50% more adherent than were CrsA(-) bacteria. Since the host cell expression of cytokines appears to play an important role in the pathogenesis of periodontal diseases, the effect of the S-layer on the epithelial cell cytokine response was also examined by quantitative reverse transcriptase PCR and enzyme-linked immunosorbent assay. Although there were no changes in the mRNA levels for the anti-inflammatory cytokines interleukin-1 receptor agonist (IL-1ra), IL-13, and transforming growth factor beta, the expression and secretion of the proinflammatory cytokines IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) were significantly induced by both wild-type C. rectus and CrsA(-) bacteria. Interestingly, the kinetics of cytokine induction differed for the CrsA(+) and CrsA(-) bacteria. At early time points, the HEp-2 cells challenged with CrsA(-) bacteria produced higher levels of IL-6, IL-8, and TNF-alpha mRNA and protein than did cells challenged with CrsA(+) bacteria. We conclude that C. rectus may help initiate periodontitis by increasing the expression of proinflammatory cytokines and that the S-layer may temper this response to facilitate the survival of C. rectus at the site of infection.
Wang
B
B
Department of Microbiology, University of Texas Health Science Center, San Antonio, Texas 78229, USA.
Kraig
E
E
Kolodrubetz
D
D
D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000502:physiology*; D002167:Campylobacter / Q000502:physiology*; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology; D006801:Humans; D009154:Mutation; D010518:Periodontitis / Q000209:etiology; D012333:RNA, Messenger / Q000032:analysis
D001426:Bacterial Proteins; D016207:Cytokines; D012333:RNA, Messenger