Outer membrane vesicles shape the interaction of Bordetella pertussis with neutrophils

BLANCÁ, BRUNO; ALVARES HAYES JIMENA; BAROLI, CARLOS; LAMBERTI, YANINA; RODRIGUEZ, MARIA EUGENIA

Congreso; Reunión de Sociedades de Biociencias 2021. LXVI Reunión Anual de la Sociedad Argentina de Investigación Clínica (SAIC). LXIX Reunión Anual de la Sociedad Argentina de Inmunología (SAI). LIII Reunión Anual de la Asociación Argentina de Farmacología Experim; 2021

Outer membrane vesicles (OMVs) secreted by pathogenic bacteria are usually loaded with virulence factors that get to the host cell without close contact with the bacteria. Bordetella pertussis (Bp), the etiologic agent of pertussis, releases OMVs during infection. By proteomics analysis we confirmed the presence of most of Bp virulence factors in OMVs, adenylate cyclase toxin (CyaA, a strong immunomodulatory toxin) among them. In this study we investigated whether the presence of OMVs affects the outcome of Bp encounter with neutrophils (PMN), the main defense of the host against invading pathogens. We first studied the effect of the OMVs in the innate encounter of Bp with PMN. The presence of OMVs led to a significant decrease in bacterial uptake, which proved to be dependent on the delivery of CyaA from these vesicles, as determined by studies performed with OMVs isolated from a Bp CyaA deficient mutant (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 a bactericidal modulating effect of CyaA. Our results further showed that OMVs might protect Bp from PMN even in immune hosts. By means of double immune staining and fluorescence microscopy in combination with the use of cytochalasin D, we here observed that in the presence of specific antibodies the OMVs get opsonized and compete with opsonized bacteria for FcgR on PMN, leading to a significant 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 with opsonized 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 delivery should be considered within the immune evasion mechanisms of Bp