Bacterial secreted proteins are required for the internalization of Campylobacter jejuni into cultured mammalian cells

Abstract

Presented here is the first evidence that Campylobacter jejuni secrete proteins upon co‐cultivation with host cells and in INT 407 cell‐conditioned medium. A C. jejuni gene designated ciaB for Campylobacter invasion antigen B was identified, using a differential screening technique, which is required for this secretion process and the efficient entry of this bacterium into a host cell. The C. jejuni ciaB gene encodes a protein of 610 amino acids with a calculated molecular mass of 73 154 Da. The deduced amino acid sequence of the CiaB protein shares similarity with type III secreted proteins associated with the invasion of host cells from other more extensively characterized bacterial pathogens. In vitro binding and internalization assays revealed that the binding of C. jejuni ciaB null mutants was indistinguishable from that of the parental isolate, whereas a significant reduction was noted in internalization. Confocal microscopic examination of C. jejuni‐infected cells revealed that CiaB was translocated into the cytoplasm of the host cells. Culturing C. jejuni with INT 407 cells or in INT 407‐conditioned medium resulted in the secretion of at least eight proteins, ranging in size from 12.8 to 108 kDa, into the culture medium. C. jejuni ciaB null mutants were deficient in the secretion of all eight proteins, indicating that CiaB is required for the secretion process. The identification of the C. jejuni ciaB gene represents a significant advance in understanding the molecular mechanism of C. jejuni internalization and the pathogenesis of C. jejuni‐mediated enteritis.

Energy Taxis Drives Campylobacter jejuni toward the Most Favorable Conditions for Growth

“…However, examination of C. jejuni's aggregation and biofilm formation showed no significant difference between the mutants and the wild-type strain (results not shown), indicating that the impaired invasion of the four tlp mutants was not caused by major modifications of global surface structures. We further examined whether the reduced invasion was mediated by altered gene expression of known virulence factors by studying the transcriptional expression of cadF, ciaB, and csrA, encoding a fibronectin binding protein, a host cell internalization protein, and a putative global regulator, respectively (16,26,27). However, Northern blot experiments revealed no change in the expression profiles of cadF, ciaB, and crsA for the invasion-deficient tlp1 and docB mutants (results not shown).…”

Virulence genes and cytokine profile in systemic murineCampylobacter coliinfection

“…18,[30][31][32] One of these is the cadF gene, which encodes a protein belonging to the group of outer-membrane proteins that facilitates the binding of Campylobacter spp. in the host cells, 33 as was confirmed by Campylobacter spp colonisation using a chicken model. 34 Another virulence gene linked with Campylobacter spp.…”

Identification and Characterization of an Invasion Antigen B Gene from the Oral Pathogen Campylobacter rectus

“…Among the best studied virulence factors of campylobacters is the invasion antigen gene B (ciaB) of C. jejuni, which has been shown to play a key role in host cell invasion [18][19][20]. In C. jejuni, CiaB has been shown to be a secreted protein, although it lacks a predictable signal peptide [19].…”

“…Among the best studied C. jejuni virulence factors is the ciaB gene, which has been shown to play a critical role in host cell invasion; and therefore pathogenesis [18][19][20]. In addition, ciaB genes have been identified from additional campylobacters including Campylobacter lari, Campylobacter coli, and Campylobacter upsaliensis [21,22].…”