CONICET | Buscador de Institutos y Recursos Humanos

Bordetella pertussis (Bp) is a strictly human pathogen and the etiological agent whooping cough, a reemerging respiratory disease. Current vaccines fail to prevent host colonization and previous findings indicated that Bp establishes intracellular niches of persistence within the host, which might have implications for the current epidemiological scenario. Results from our group showed that Bp adapts its phenotype and persists in phagosomes with early endosomal characteristics inside human macrophages, modulating the cellular bactericidal response through pertussis toxin (PT) and adenylate cyclase toxin (CyaA). We recently showed that Bp is also able to remain alive inside polarized respiratory epithelial cells in compartments with late endosomal characteristics in which it has access to extracellular nutrients. Comparative proteomics of intracellular bacteria isolated from macrophages and epithelial cells, together with in vitro assays using mutant strains lacking the expression of selected bacterial factors evidenced the differences between these two potential niches of persistence, and helped to explain the higher intracellular survival rate observed in the epithelial cells. Briefly, our results showed that, unlike macrophages, neither PT nor CyaA are needed to establish an intracellular niche in epithelial cells. The absence of either of these toxins did not impact bacterial intracellular trafficking or survival, as addressed through confocal studies and polymyxin B protection assays, respectively. The proteomic investigation of Bp residing inside the epithelial cells revealed the lack of activation of a bacterial stress response and essential metabolic proteins previously identified as crucial for Bp survival within these immune cells. In vitro experiments conducted using specific mutant strains corroborated the lack of relevance of these factors for intracellular survival within respiratory cells. The changes induced at protein level in bacteria residing in the epithelial cells were mainly related to proteins involved in metabolic processes, and indicated a deceleration of intracellular bacterial metabolism, which is consistent with a persistent phenotype. Collectively, these findings stress the capacity of the pathogen to adapt and survive in different intracellular environments. They, additionally, highlight that airway epithelial cells potentially offer a more favorable environment for Bp survival as compared to immune cells. Given the substantial abundance of these cells within the human host, these results identify these cells as potential key determinants in the pathogen´s persistence.

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