A recombinant vector (A) is new and comprises a polynucleotide (I) that includes a cis-acting central initiation region (cPPT； polypurine track) and a cis-acting terminator (CTS), both of retroviral or retroviral-like origin. It also includes a selected nucleotide sequence (II), i.e. a transgene or gene of interest, and retroviral(-like) regulators of reverse transcription (RT), expression and packaging. Independent claims are also included for the following: (1) recombinant retroviral particles (B) containing (I), inserted in a functional orientation with respect to retroviral(-like) regulators of RT； (2) recombinant retroviral particles (C) containing a recombinant sequence (Ia) consisting of (I) and (II), plus gag, pol and envelope proteins； (3) recombinant vector particles (D) including a recombinant sequence (Ib) comprising a transgene (plus regulators) and (I)； (4) recombinant cells containing (A)-(D)； (5) therapeutic or immunogenic composition containing (A)-(D) or the cells of (d)； (6) polynucleotide (III), derived from a retroviral genome and containing 80-120, particularly 90-110, nucleotides (nt), flanked by cPPT and CTS； and (7) polynucleotides (IIIa) comprising (III) and (II). ACTIVITY : Antitumor； cytostatic； immunostimulant. MECHANISM OF ACTION : None given.
