The invention relates to an immunogenic composition comprising a recombinant vector characterized in that it comprises a polynucleotide comprising the cis-acting central initiation region (cPPT) and the cis-acting termination region (CTS), these regions being of retroviral or retroviral-like origin, said vector comprising in addition a defined nucleotide sequence (transgene or sequence of interest) and regulatory signals of retrotranscription, expression and encapsidation of retroviral or retroviral-like origin, wherein the composition is capable of inducing or of stimulating a cell-mediated response for instance a CTL (Cytotoxic T Lymphocytes) response or a CD4 response, against one or several epitopes encoded by the transgene sequence present in the vector.
