Characterization of outer membrane vesicle-carried proteins as pathogenicity factors from Acinetobacter baumannii

REPIZO G; VIALE, A. M; CEBRERO-CANGUIRO T; PACHÓN-IBAÑEZ ME; GIACONE, L; PACHÓN J; MORAN BARRIO, J

Buenos Aires

Workshop; International Society for Extracellular Vesicles 2020 Workshop. EVs in Immunology; 2020

Acinetobacter baumannii (Ab) is a nosocomial pathogen, of major concern due to its multi-drug resistance (MDR) and the recent appearance of hyper-virulent strains in the clinical setting. The World Health Organization included Ab as a critical priority pathogen for the development of novel antibiotics. Ab pathogenesis is associated with a multitude of potential virulence factors (VF) that remain poorly characterized. There is growing evidence that outer membrane vesicles (OMV) are used as vehicles to transport bacterial proteins that contribute to set up the conditions for the infections. In the present work we studied the physiopathology of MDR Ab. We focused on the contribution of non-characterized outer membrane proteins (OMPs) associated to OMVs, with special focus on lipoproteins (LP). We conducted a bioinformatic prediction using available datasets to construct a list of OMV-associated OMPs putatively acting as VF in AB5075. Eight genes were selected and the corresponding mutants were obtained from Manoil Lab collection. Biochemical analysis indicated similar growth rates in rich media, as well as similar levels of OMV production for all the mutants as compared to WT. Also, no differences in susceptibility to chaotropic agents were observed, indicating no alteration of the OM function as a general permeability barrier. The involvement of the selected proteins in Ab pathogenesis was evaluated by adherence, invasion, and cytotoxicity assays on human lung cells A549. All mutants reduced A549 cell viability similarly, but in less extend than the WT. Moreover, three of them exhibited less adhesion and invasion compared to the WT, and OMV isolated from these mutants displayed also less cytotoxicity. These results suggest roles for the mutant gene products in Ab pathogenesis and contribute to the better understanding of Ab virulence mechanisms, revealing novel possible targets for therapeutic development.