CONICET | Buscador de Institutos y Recursos Humanos

Outer membrane vesicles (OMVs), naturally produced by Gram-negative bacteria, were found involved in pathogenesis and host response manipulation. It was demonstrated that B. pertussis produces OMVs during infection. We had previously found that B. pertussis is able to modulate the macrophage response eventually favoring its intracellular survival. In order to investigate whether the presence of OMVs affects the outcome of this interaction we isolated OMVs from the late exponential growth phase of Bp cultures and employed them in macrophages infection studies. Human macrophages were incubated with or without OMVs prior to bacterial infection. Confocal microscopy studies confirmed the OMVs association with macrophages at the time of bacterial infection and showed that the presence of OMVs led to a significant decrease in both bacterial uptake and in the number of bacteria trafficked to lysosomes. Accordingly, macrophage pre-incubation with OMVs led to an increase in bacterial intracellular survival. Previous studies have demonstrated that B. pertussis adenylate cyclase toxin (CyaA) modulates macrophage defense response. Since we confirmed the presence of CyaA in the OMVs used in this study, we investigated whether this toxin plays a role in the observed effect on the intracellular survival. To that end, we isolated OMVs from a B. pertussis CyaA defective mutant strain and used them in the same experimental setup. Our results showed that the CyaA present on the OMVs is indeed involved in the observed effect on the bacterial survival inside the cell since the lack of this toxin in OMVs determined a significant decrease in the intracellular survival. Altogether, these results indicate that OMVs from B. pertussis exert cellular effects, mainly through the CyaA present in these vesicles, that modulate the innate immune response of macrophages to B. pertussis infection. These effects may favor the persistence of B. pertussis within host cells.