OUTER MEMBRANE VESICLES SHAPE THE INTERACTION OF BORDETELLA PERTUSSIS WITH NEUTROPHILS

BLANCÁ, BRUNO; ALVAREZ HAYES, JIMENA; BAROLI, CARLOS; LAMBERTI, YANINA; RODRIGUEZ, MARÍA EUGENIA

Congreso; REUNIÓN DE SOCIEDADES DE BIOCIENCIAS 2021; 2021

Outer membrane vesicles (OMVs) secreted by pathogenic bacteriaare usually loaded with virulence factors that get to the host cellwithout close contact with the bacteria. Bordetella pertussis (Bp),the etiologic agent of pertussis, releases OMVs during infection. Byproteomics analysis we confirmed the presence of most of Bp virulence factors in OMVs, adenylate cyclase toxin (CyaA, a strongimmunomodulatory toxin) among them. In this study we investigatedwhether the presence of OMVs affects the outcome of Bp encounter with neutrophils (PMN), the main defense of the host againstinvading pathogens. We first studied the effect of the OMVs in theinnate encounter of Bp with PMN. The presence of OMVs led to asignificant decrease in bacterial uptake, which proved to be dependent on the delivery of CyaA from these vesicles, as determinedby studies performed with OMVs isolated from a Bp CyaA deficientmutant (OMVs-CyaA-). Confocal microscopy studies showed a significant decrease in bacterial colocalization with the late endosomal/lysosomal marker LAMP-1 in PMN incubated with OMVs as compared with PMN treated with media or OMVsCyaA-, suggesting abactericidal modulating effect of CyaA. Our results further showedthat OMVs might protect Bp from PMN even in immune hosts. Bymeans of double immune staining and fluorescence microscopy incombination with the use of cytochalasin D, we here observed thatin the presence of specific antibodies the OMVs get opsonized andcompete with opsonized bacteria for FcgR on PMN, leading to asignificant decrease in the number of bacteria taken up by PMN.Confocal microscopy studies also showed that bacterial colocalization with LAMP-1 was significantly lower in PMN incubated withopsonized OMVs as compared with PMN treated with media alone,favoring the odds of bacterial survival also in immunized individuals.Taken together, these results seem to indicate that OMVs deliveryshould be considered within the immune evasion mechanisms of Bp