Novel nucleic acids include non-integrative chimeric retroviral genomes including the 5′ and 3′ long terminal repeat sequences (LTRs) of the caprine lentivirus: the Caprine Arthritis Encephalitis Virus (CAEV) or of another retrovirus not integrating human cells and at least one viral gene of another retrovirus. A vector including such a nucleic acid, an immunogenic or vaccinal composition including the vector or the nucleic acid, as well as their use for treating and/or preventing an infection by a retrovirus or a disease induced by a pathogenic agent are also described.
