Transcellular Passage of Neisseria meningitidis across a Polarized Respiratory Epithelium

Abstract

Neisseria meningitidis is a major cause of sepsis and meningitis but is also a common commensal, present in the nasopharynx of between 8 and 20% of healthy individuals. During carriage, the bacterium is found on the surface of the nasopharyngeal epithelium and in deeper tissues, while to develop disease the meningococcus must spread across the respiratory epithelium and enter the systemic circulation. Therefore, investigating the pathways by which N. meningitidis crosses the epithelial barrier is relevant for understanding carriage and disease but has been hindered by the lack of appropriate models. Here, we have established a physiologically relevant model of the upper respiratory epithelial cell barrier to investigate the mechanisms responsible for traversal of N. meningitidis. Calu-3 human respiratory epithelial cells were grown on permeable cell culture membranes to form polarized monolayers of cells joined by tight junctions. We show that the meningococcus crosses the epithelial cell barrier by a transcellular route; traversal of the layer did not disrupt its integrity, and bacteria were detected within the cells of the monolayer. We demonstrate that successful traversal of the epithelial cell barrier by N. meningitidis requires expression of its type 4 pili (Tfp) and capsule and is dependent on the host cell microtubule network. The Calu-3 model should be suitable for dissecting the pathogenesis of infections caused by other respiratory pathogens, as well as the meningococcus.

Two Strikingly Different Signaling Pathways Are Induced by Meningococcal Type IV Pili on Endothelial and Epithelial Cells

“…On the other hand, there is no visible opening of tight-junction-forming epithelial monolayers of T84 or Caco2 cells. Our data are consistent with previously published works showing that the crossing of a tight-junction-forming epithelial monolayer occur via a transcytosis pathway and is not associated with a decrease in transepithelial resistance or a disruption of intercellular junctions (18,23,31). This is consistent with the low frequency of infection, although the opening of the endothelial wall seems to be very efficient and can participate in the peripheral symptoms observed in meningococcal infections.…”

“…Meningococcal interaction on epithelial cells is responsible as for endothelial cells for the formation of cortical plaque with accumulation under the colony of ezrin, actin, adhesion molecules and membrane receptors that are clustered in a honeycomb-like structure. However, previous reports obtained with capsulated and piliated N. meningitidis suggested that tight junctions were not altered by meningococcal interaction with epithelial cells and that bacteria were likely to cross epithelial monolayer using the transcellular route (23,31). We subsequently aimed at deciphering the discrepancies observed in meningococcal host cell interaction.…”

“…However, several reports have shown that N. meningitidis interaction with epithelial cells does not alter the junctions, and bacteria are believed to cross the epithelium using the transcellular route (18,23,31). The mechanism by which bacteria are internalized into eukaryotic cells is not fully understood but seems to involve the secondary adhesion molecules Opa and Opc (33,35,36).…”

Transcytosis ofListeria monocytogenesacross the intestinal barrier upon specific targeting of goblet cell accessible E-cadherin

“…In vitro studies have shown that bacteria can transcytose across cultured cell monolayers, including Campylobacter jejuni (Grant et al, 1993;Russell and Blake, 1994;Bacon et al, 2001;Kopecko et al, 2001;Hu et al, 2008;Watson and Galán, 2008), Neisseria gonorrhoeae and Neisseria meningitidis (Makino et al, 1991;Merz and So, 2000;Kuespert et al, 2006;Wang et al, 2008;Sutherland et al, 2010), Streptococcus pneumoniae (Zhang et al, 2000;Kaetzel, 2001), and Escherichia coli (Burns et al, 2001;Xie et al, 2004). Yet, with the exception of bacterial sampling by M cells (see next paragraph), this is the first time to our knowledge that a bacterium has been shown to translocate across an epithelial layer by transcytosis in vivo, resulting in its systemic dissemination.…”

Establishing a Liquid-covered Culture of Polarized Human Airway Epithelial Calu-3 Cells to Study Host Cell Response to Respiratory Pathogens <em>In vitro</em>

“…, pharmacological compounds [2][3][4][5][6] , and bacterial [7][8][9] and viral pathogens, including influenza virus, rhinovirus and severe acute respiratory syndrome -associated coronavirus [10][11][12][13][14] . Recently, we demonstrated that Calu-3 cells are susceptible to respiratory syncytial virus (RSV) infection in a manner consistent with NHBE 15,16 .…”