Naturally secreted outer membrane vesicles (OMVs) from gut microbes carry diverse cargo, including proteins, nucleic acids, toxins, and many unidentified secretory factors. Bacterial OMVs can shuttle molecules across different cell types as a generalised secretion system, facilitating bacterial pathogenicity and survival. Numerous mucosal pathogens, including Campylobacter jejuni (C. jejuni), share a mechanism of harmonised secretion of major virulence factors. Intriguingly, as a common gut pathogen, C. jejuni lacks some classical virulence-associated secretion systems; alternatively, it often employs nanosized lipid-bound OMVs as an intensive strategy to deliver toxins, including secretory proteins, into the target cells. My research focused on understanding how the biophysical and compositional attributes of natural OMVs of C. jejuni regulate their cellular interactions to induce a biologically relevant host response, and to check the vaccine potential of OMVs against C. jejuni in chickens model.