Abstract: The invention provides a recombinant virus vector for use as an immunotherapeutic or vaccine. The recombinant virus vector comprises at least one pair of nucleotide sequences heterologous to the virus and which have sufficient sequence homology that recombination between them might be expected. The pair of nucleotide sequences are arranged in the virus vector such that they are inverted with respect to each other. The virus vector is able to infect a mammalian host cell and express as polypeptide the heterologous nucleotide sequences in the host cell. For infection thought to be caused by HPV infection, the pair of nucleotide sequences encode part or all of human papillomavirus (HPV) wild-type proteins or mutant proteins immunologically cross-reactive therewith. For an immunotherapeutic or vaccine against cervical cancer, the recombinant virus vector encodes part or all of the HPV wild-type proteins HPV16E7 and HPV18E7 or mutant proteins immunologically cross-reactive therewith.