Recombinant outer membrane vesicles to augment antigen-specific live vaccine responses.

Release of outer membrane vesicles is a common feature of Gram negative bacteria. There is growing interest in the use of these vesicles in the development of affordable vaccines. However, to exploit their full potential a convenient system to generate recombinant vesicles would be highly desirable. Here, we report the design of a versatile system for preparation of recombinant outer membrane vesicles based on an engineered autotransporter. Two model vaccine antigens of Leishmania were expressed as fusion proteins with the transporter domain of AIDA, the Escherichia coli adhesin involved in diffuse adhesion. Single subcutaneous injections of recombinant vesicles boosted vaccine antigen-specific antibody responses in mice primed with live recombinant salmonella vaccines by 6-40-fold. The results further show an expansion of only the vaccine antigen-specific antibody response indicating a great potential of this approach for prime boost vaccination strategies.