Influence of outer membrane vesicles of Bordetella pertussis on bacterial interaction with macrophages

BLANCÁ, BRUNO; ALVAREZ HAYES, JIMENA; RODRIGUEZ, MARÍA EUGENIA

Mar del Plata

Congreso; LXIV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA; 2016

Sociedad Argentina de Inmunología

Outer membrane vesicles (OMVs) are naturally produced bacterial vesicles released by Gram negative bacteria. These vesicles contain adhesins, toxins, lipoproteins, LPS, among other bacterial factors, and interact with host cells acting as virulence factor delivery vehicles. OMVs usually modulate the host immune response by enhancing the virulence of the infection. Bordetella pertussis, the causative agent of whopping cough, is able to produce OMVs not only during in vitro growth but also during infection inside host. In the present study we isolated OMVs from B. pertussis culture grown until late log phase using sterile filtration followed by an ultracentrifugation step and plated in Bordet-Gengou agar to test for the presence of viable bacteria. OMVs purity and morphology was analyzed by transmission electron microscopy. We next study the interaction of B. pertussis OMVs with macrophages, a kind of cells in which we previously showed that this pathogen is able to develop intracellular infections. Human macrophages were obtained from fresh buffy coats using a Ficoll hypaque density gradient centrifugation. Fluorescence microscopy showed that OMVs are associated with macrophages after 4 h of incubation. We further observed that pre-incubation with vesicles before bacterial infection lead to a significant reduced bacterial uptake (12 bacteria/cell) as compare with control macrophages not treated with OMVs (33 bacteria/cell). However, confocal microcopy analysis showed no difference in bacterial co-localization with lysosomes, indicating that the evolution of infection is not altered. Altogether these results suggest that B. pertussis OMVs might induce changes in macrophages response that represent an advantage to immune cells bacterial evasion