Bacterial Outer Membrane Vesicles (OMVS) Provide Broad and Immediate Protection against Influenza Infection

Influenza has been a serious health problem due to the high mutation and transmission rates as well as the pathogenicity of the influenza viruses. Since the conventional vaccines are type-specific and require several weeks for the induction of protective immunity, novel antiviral agents are needed to overcome the shortage of the current vaccines. In this study, we evaluated the antiviral potential of bacterial outer membrane vesicles (OMVs) using a murine influenza model. OMVs stimulated diverse Toll-like receptors on and in the cells in vitro. Additionally, intranasal administration of OMV conferred rapid protection against various subtypes of influenza viruses, whereas the conventional vaccine exhibited subtype or strain-specific efficacy. Pretreatment of OMVs rapidly activated innate immune response in the lungs: production of pro-inflammatory cytokines and recruitment of neutrophils and monocytes. These results demonstrate that OMV could be an active and immediate immunomodulator capable of controlling influenza virus infection.