Lentiviruses are a subclass of retroviruses, which are a group of viruses that have the ability to integrate their RNA back into the human genome. Lentiviruses are distinctive because they can integrate into nondividing cells, which normal retroviruses cannot. This makes them good candidates for gene therapy vectors as they should be able to replace mutated genes with correct versions. Unfortunately lentiviruses include HIV and hepatitis, so persuading the public they are safe will be difficult.