Acinetobacter baumannii as a Model for the Study and Application of Gram-Negative Outer Membrane Vesicles: A Systematic Review.

Outer membrane vesicles (OMVs) are extracellular nanostructures released from Gram-negative bacteria. Acinetobacter baumannii OMVs (AbOMVs) have been extensively studied and can thus be used as a model for understanding multiple aspects of OMV biology. In this systematic review, we comprehensively assess the relevant literature covering AbOMVs and present these studies in the context of OMV biology in general. An overview of current knowledge regarding AbOMV biogenesis is presented, focusing on the cellular, intrinsic and extracellular factors that induce AbOMV production. In addition, the components that form the AbOMVs, with an emphasis on protein content, are described. Different methodologies that have been used to isolate and purify the AbOMVs for different studies and applications are discussed. In addition, we provide a synthesis of the different roles played by AbOMVs in bacterial pathobiology, including the delivery of virulence factors, activation of immune response, gene transfer and antibiotic resistance. Finally, we detail the biotechnological applications that have employed AbOMVs, focusing on the development of AbOMV-based vaccines. Altogether, this systematic review offers a perspective of current knowledge of AbOMV and serves as a case study of Gram-negative OMVs in general.