Pathogenic mechanisms of Campylobacter jejuni : Characterization and identification of the role of CadF in Campylobacter-mediated enteritis.

摘要

Campylobacter jejuni, a Gram-negative, spiral shaped bacterium is currently recognized as the leading cause of gastroenteritis in humans worldwide. Despite this prevalence, little is known regarding the mechanism by which C. jejuni causes disease. Researchers have proposed a multifactorial infection process whereby motility, chemotaxis, host cell-translocation, host cell-adherence, host cell-invasion, and toxin production function in a coordinated manner resulting in disease. The primary goal of the research described herein was to characterize the role of adherence in establishment of a successful infection in a human host using in vitro model systems. More specifically, work focussed on characterizing the role of the C. jejuni adhesin CadF, C&barbelow;ampylobacter adhesion to f&barbelow;ibronectin, in C. jejuni-mediated enteritis. The CadF adhesin is a 37 kDa outer membrane protein which facilitates the adherence of C. jejuni to the host extracellular matrix component fibronectin. The results generated revealed that the CadF adhesin functions to localize C. jejuni to specific receptors on host-cells thereby maximizing invasion. Furthermore, the CadF adhesin enables the bacterium to adhere to fibronectin localized at the basolateral surface of host-cells following translocation via a paracellular route. This interaction prevents the organism from translocation completely across an intact epithelial barrier and therefore allows the bacterium to subsequently invade host cells. I hypothesize that C. jejuni association with fibronectin leads to integrin (alpha5beta 1) occupancy and clustering. This hypothesis is supported by data which revealed that host-cell signalling events, such as phosphorylation of paxillin, were dependent upon the CadF adhesin. Following the binding of C. jejuni to fibronectin, data further indicate that C. jejuni is taken up by host cells via cooperative interaction between both microfilaments and microtubules. Additional studies using the C. jejuni CadF amino acid sequence and synthesized peptides with overlapping regions revealed that the CadF adhesin possesses a single fibronectin binding domain. These results provide a more detailed model of C. jejuni-mediated enteritis and support the hypothesis that the CadF adhesin contributes to the virulence of C. jejuni by maximizing the organism's adherence to appropriate host-cell receptors. In turn, this binding increases the organism's invasive potential.