The present invention relates to compositions and methods for selectively expressing a polypeptide in a membrane vesicle. The invention also relates to genetic constructs and recombinant cells suitable to produce such membrane vesicles. This invention also relates to such functionalized membrane vesicles as well as to methods of making antibodies, methods of producing or regulating an immune response as well as to methods of screening or identifying binding partners using the same. The invention more particularly uses lactadherin or portions thereof to selectively express polypeptides in membrane vesicles, of natural or synthetic origin. This invention can be used in experimental, research, therapeutic, prophylactic or diagnostic areas.