Abstract
Bordetella pertussis is a highly contagious pathogen which causes whooping cough in humans. A major pathophysiology of infection is the extrusion of ciliated cells and subsequent disruption of the respiratory mucosa. Tracheal cytotoxin (TCT) is the only virulence factor produced by B. pertussis that has been able to recapitulate this pathology in animal models. This pathophysiology is well characterized in a hamster tracheal model, but human data are lacking due to scarcity of donor material. We assessed the impact of TCT and lipopolysaccharide (LPS) on the functional integrity of the human airway mucosa by using in vitro airway mucosa models developed by co-culturing human tracheobronchial epithelial cells and human tracheobronchial fibroblasts on porcine small intestinal submucosa scaffold under airlift conditions. TCT and LPS either alone and in combination induced blebbing and necrosis of the ciliated epithelia. TCT and LPS induced loss of ciliated epithelial cells and hyper-mucus production which interfered with mucociliary clearance. In addition, the toxins had a disruptive effect on the tight junction organization, significantly reduced transepithelial electrical resistance and increased FITC-Dextran permeability after toxin incubation. In summary, the results indicate that TCT collaborates with LPS to induce the disruption of the human airway mucosa as reported for the hamster tracheal model.
Highlights
Bordetella pertussis is a gram-negative bacterium that causes whooping cough mainly in humans
The scanning electron micrographs revealed that the surface of the human tracheobronchial mucosa models (hTBM) incubated with a combination of tracheal cytotoxin (TCT) and LPS was largely covered with cell debris and extruded cells
The aim of this study was to assess the potential contribution of TCT to cytopathology of infection in a human in vitro airway model developed from primary tracheobronchial epithelial cells and fibroblasts (Steinke et al, 2014; Schweinlin et al, 2017)
Summary
Bordetella pertussis is a gram-negative bacterium that causes whooping cough mainly in humans. B. pertussis produces several virulence factors known to modulate host defense mechanisms required for an efficient colonization of the airway mucosa. These factors include several adhesins and toxins (Weiss et al, 1984; Anderton et al, 2004; Kilgore et al, 2016). As shown for the close relative Bordetella bronchiseptica in a canine model, infection leads to the dysfunction of the mucociliary clearance mechanism and mucosa damage allowing the bacteria to colonize the epithelium (Anderton et al, 2004). TCT has been implicated in the destruction of the ciliated epithelia of the airway in animal models and in human nasal biopsies (Goldman & Cookson, 1988; Wilson et al, 1991; Luker et al, 1993), hindering the mucociliary clearance mechanism and indicating that TCT may be a potentially important virulence factor of B. pertussis
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