Adjuvant effect of bacterial outer membrane vesicles with penta-acylated lipopolysaccharide on antigen-specific T cell priming

► Gram-negative bacteria shed outer membrane vesicles (OMV). ► We studied adjuvant activity of OMV with penta-acylated LPS that is less endotoxic. ► The OMV with penta-acylated LPS has adjuvant activity on T cell priming. ► The adjuvant activity depends on Toll-like receptor-4. ► The OMV with penta-acylated LPS activates dendritic cells efficiently.