Abstract: The present invention relates to compositions and methods for producing an immune response or reaction, as well as to vaccines, kits, processes, cells and uses thereof. This invention more particularly relates to compositions and methods of using a synthetic viral particle to produce, modify or regulate an immune response in a subject. In a more preferred embodiment, the invention is based, generally, on compositions using synthetic viral particles as an adjuvant and/or vehicle to raise an immune response against selected antigen(s) or epitopes, in particular a cellular and/or a humoral immune response.