A modified human immunodeficiency virus genome vector is disclosed characterised in that the vector is replication-incompetent in a living cell which is free from the wt-HIV virus, but replication-competent in a cell infected with the wild-type HIV virus, due to the wild-type virus providing the mutant virus with viral components essential for viral replication, which are mutated in the modified virus. Nucleic acids in the modified HIV vector may encode mutated viral components such as reverse transcriptase, integrase, proteases, matrix and capsid proteins, infectivity and regulatory factors or viral nucleic acids. Preferably, the modified HIV vector can be used to treat or prevent an infection caused by any genetic variant of HIV. Preferably, the conditionally replicative HIV vector eradicates wild-type HIV-positive (HIV+) cells by promoting host cell apoptosis and suppressing the assembly and/or maturation of the wild-type virus through competition for the aforementioned viral components required for replication. The modified HIV vector is a defective-interfering virus (also called defective-interfering particle, DIP, therapeutic-interfering particle, TIP), may be used to eradicate latent HIV infection and may encode antisense RNAs against viral nucleic acids and/or proteins. Methods of the invention may also be used to treat other viruses.
