Traversal of a Polarized Epithelium by Pathogenic Neisseriae: Facilitation by Type IV Pili and Maintenance of Epithelial Barrier Function

Abstract

Background: Gonococci (GC) and meningococci (MC) are gram-negative bacterial pathogens that infect human mucosal epithelia. We would like to understand the functions of specific bacterial components at each stage of mucosal colonization: adhesion, cell invasion, and traversal into subepithelial tissues. As no animal model of mucosal colonization by GC or MC is available, increasingly sophisticated in vitro approaches have been used to address these issues.Materials and Methods: We adapted the polarized T.4 human epithelial cell system to study GC and MC colonization. Epithelial barrier function was monitored by permeability to soluble tracers and with electrical resistance measurements. Polarized cells were used to assay bacterial traversal of the monolayers, and cells grown on plastic were used to assay adhesion and cell invasion. Results: All pathogenic Neisseriae examined traversed the monolayers. The traversal times were species specific and identical to times established previously in organ culture studies. In contrast to experiments with some enteric pathogens, transmigration by GC and MC was not accompanied by disruption of the epithelial barrier. GC mutants lacking type IV pili were compromised in adhesion, invasion, and traversal of T84 cells. Conclusions: Experiments with polarized T84 cells mimic key features of organ culture infections and reveal additional aspects of neisserial infection. Epithelial barrier function can be retained during bacterial traversal. Experiments with a nonpiliated GC mutant and its wildtype parent indicated an unexpected role for pili in cell invasion. Our results are consistent with the hypothesis that bacterial adhesion, invasion, or both are rate-limiting for traversal across the epithelium.

Influence of type IV pilus retraction on the architecture of the Neisseria gonorrhoeae-infected cell cortex

“…1a, iii). MS11pilE, a non-piliated isogenic mutant of MS11, adheres to epithelial cells at a much lower frequency than Tfp-expressing GC (Merz et al, 1996). Of those MS11pilE that adhered, few microvilli were observed associated with them (Fig.…”

“…It produced non-retractable Tfp and was non-motile Wolfgang et al, 1998). MS11pilE (clone 307) was a non-piliated (DpilE1, DpilE2) strain of MS11 (Ayala et al, 2001;Merz et al, 1996). Bacteria were grown on GCB agar (Difco) with Kellogg's supplements I and II, and maintained at 37 uC, 5 % CO 2 .…”

Rho GTPases as pathogen targets: Focus on curable sexually transmitted infections

“…Pilus retraction 50 triggers a tight association between the bacterial opacityassociated (Opa) outer membrane proteins and the host cell receptors, which promotes invasion. 48,[50][51][52][53] A single gonococcal strain can harbour 11 opa genes that can be switched on and off independently. These genes contain 5 0 tandem repeats [CTCTT]n that cause high-frequency, phase-variable expression, 54 in addition to intra-and inter-genomic recombination events.…”

Invasion of endothelial cells by Neisseria meningitidis requires cortactin recruitment by a phosphoinositide-3-kinase/Rac1 signalling pathway triggered by the lipo-oligosaccharide

“…a colony at their site of attachment on the cell surface. When adhering to the apical membrane of epithelial cells, N. meningitidis induces the local elongation of microvilli towards the bacteria, leading to their engulfment and internalization (Merz et al, 1996;Pujol et al, 1997). Adhesion of N. meningitidis to endothelial cells promotes the local formation of membrane protrusions reminiscent of epithelial microvilli structures that surround bacteria and provoke their internalization within intracellular vacuoles .…”