Bordetella parapertussis adenylate cyclase toxin grants the bacterial invasion of and persistence within respiratory epithelial cells

GORGOJO, JUAN PABLO; CARRICA MARIELA; BAROLI CARLOS; RODRIGUEZ, MARÍA EUGENIA

VANCOUVER

Congreso; 13th International Symposium on Bordetella; 2022

The Bordetella Symposim Organizing Committee

The airway epithelium plays a crucial role in the host defense although it also constitutes a niche of persistence for some facultative intracellular pathogens. In this study we investigated B. parapertussis interaction with respiratory epithelium using an in vitro model of polarized 16HBE14o- cells. These human bronchial epithelial cells retained most of the functions of the primary cells and develop tight junctions in vitro. Using a subconfluent model of polarized 16HBE14o- cells we found that B. parapertussis mainly attached to the basolateral membrane. Around 90% of these attached bacteria were rapidly internalized and followed a non-bactericidal pathway as determined by confocal microscopy. Accordingly, Polymyxin B protection assays showed that most of the internalized bacteria were still alive 48 h after infection. Tight junctions would restrict the access to the basolateral membrane in the intact epithelium. However, using closed monolayers of 16HBE14o- cells we observed that B. parapertussis mostly attached around the tight junctions that, after a few hours, were disrupted in an adenylate cyclase dependent way. The monolayer infection with the wild type but not with a CyaA deficient mutant of B. parapertussis led to the disruption of the integrity of the occludin network, as observed by confocal microscopy. Together, these results suggest that during B. parapertussis interaction with the intact epithelium, the action of CyaA might open the tight junctions between cells enabling the bacterial access to the basolateral membrane of epithelial cells and, therefore, to the protective intracellular environment where it can persist.