A method to induce an immune response in a host in need thereof, comprises administering to the host, recombinant lentiviral vector particles comprising:a) a GAG polypeptide or a functional GAG-polypeptide derivativeb) a POL polypeptide or a functional POL-polypeptide derivative c) an ENV polypeptide or a functional ENV-polypeptide derivative andd) a recombinant polynucleotide.The recombinant polynucleotide comprises a transgene placed under the control of regulatory signals for transcription and expression, regulatory signals, of lentiviral origin, for reverse transcription, expression and packaging, and a polynucleotide comprising a cis-acting central initiation region (cPPT) and a cis-acting termination region (CTS). The regions are of lentiviral origin and are inserted in a functional orientation with the regulatory signals of lentiviral origin. The polynucleotide forms a DNA triplex during reverse transcription.
