Background and Aim: All type of gram positive and gram negative bacteria release the discrepant extracellular vesicles during the different growth phase of their life. This vesicles are known as outer membrane vesicles and exosomes in gram negative bacteria and gram positive one, respectively. These vesicles contain various type of proteins, mRNAs and antigens surrounding with lipid layer with different contents. However, these vesicles act as a bottle of message spreading the infection in the host body.
Methods: The presence of general and specific antigens on the surface of them lead to emerge the new properties such as immunogenicity and self - adjuvantation . When these vesicles present to immune system, they are up taken by immune cells that trigger potent specific immune responses against infections. These vesicles could deliver the antigens both passively and actively.
Results: Nowadays, an outer membrane vesicle based vaccine was approved by international agencies. These types of vaccines have some advantages and disadvantages compared with traditional microbial vaccines.
Conclusion: They are not live or attenuated microorganisms but contain key antigens. In addition modified genetic engineered microorganism can produce an exosomes containing desired antigens along with targeted therapy. Furthermore, packaging the proteins and other small molecules in lipid layer leads to resist the exsosome contents agains t the enzymatic degradation and other environmental factors. However, the presence of the large number of antigens on the surface of exosomes could cause anergy.