Campylobacter jejuni survival within human epithelial cells is enhanced by the secreted protein CiaI

Abstract

Summary Although it is known that Campylobacter jejuni invade the cells that line the human intestinal tract, the bacterial proteins that enable this pathogen to survive within Campylobacter-containing vacuoles (CCV) have not been identified. Here, we describe the identification and characterization of a protein that we termed CiaI for Campylobacter invasion antigen involved in Intracellular survival. We show that CiaI harbors an amino-terminal type III secretion (T3S) sequence and is secreted from C. jejuni through the flagellar T3S system. In addition, the ciaI mutant was impaired in intracellular survival when compared to a wild-type strain, as judged by the gentamicin-protection assay. Fluorescence microscopy examination of epithelial cells infected with the C. jejuni ciaI mutant revealed that the CCV were more frequently co-localized with Cathepsin D (a lysosomal marker) than the CCV in cells infected with a C. jejuni wild-type strain. Ectopic expression of CiaI-GFP in epithelial cells yielded a punctate phenotype not observed with the other C. jejuni genes, and this phenotype was abolished by mutation of a dileucine motif located in the carboxy-terminus of the protein. Based on the data, we conclude that CiaI contributes to the ability of C. jejuni to survive within epithelial cells.

Campylobacter jejuni Translocation across Intestinal Epithelial Cells Is Facilitated by Ganglioside-Like Lipooligosaccharide Structures

“…So far, C. jejuni lysosomal escape has been visualized only with endosomal protein markers in nonintestinal epithelial cells (4,42). In our study, using Caco-2 cells we could clearly demonstrate that GM ϩ and GM Ϫ C. jejuni bacteria are located in an acidic intracellular compartment with endolysosome characteristics wherein most C. jejuni bacteria are killed.…”

“…In other words, for this isolate it was demonstrated that it was able to escape lysosomal degradation, contributing to its intracellular survival (42). Recently, Buelow and coworkers showed that intracellular survival of C. jejuni isolate NCTC11168 is enhanced by the secreted Cia protein (Cj1450) that was found to block fusion of lysosomes with the C. jejunicontaining endosome (4). The studies by Watson and Galan (42) and Buelow et al (4) did not show which specific bacterial invasion factor(s) facilitates endocytosis of C. jejuni into epithelial cells.…”

“…Factors involved in the escape from the endosomal pathway have been studied well for intracellular bacteria such as Salmonella enterica, Listeria monocytogenes, Mycobacterium tuberculosis, and Brucella abortus (16). Studies to better define such factors in C. jejuni have recently been initiated (4).…”

Campylobacter jejuni Outer Membrane Vesicles Play an Important Role in Bacterial Interactions with Human Intestinal Epithelial Cells

“…proteins CiaB, CiaC, and CiaI (11,15,42) were found to be associated with C. jejuni OMVs, suggesting that OMVs are not the mechanism by which these virulence factors are secreted. The identification of a large number of N-linked glycoproteins associated with C. jejuni OMVs is particularly significant.…”

A Cronobacter turicensis O1 Antigen-Specific Monoclonal Antibody Inhibits Bacterial Motility and Entry into Epithelial Cells

“…The flagellar secretion system is structurally related to T3SS, and virulence factors may be secreted into the extracellular medium or exposed on the bacterial cell surface, where they might influence the invasion of human intestinal cells (59,60). The protein CiaI of Campylobacter jejuni, for example, is involved in mediating cellular trafficking and plays a role in bacterial survival within cells (61). It was also reported that secretion of virulence proteins from C. jejuni is dependent on a functional flagellar export apparatus (62).…”