Gene therapy in the central nervous system: the use of recombinant retroviruses

Only a handful of the hundreds of known vertebrate retroviruses have been deliberately subverted for use as carriers of recombinant genetic material. Retroviruses receive their name from the fact that their genome undergoes conversion from RNA to DNA following infection of a host cell. Also characteristic of retroviruses and uncommon for most other types of viruses is that the genome of the retrovirus integrates itself permanently into the DNA of the host cell. Once integrated into the host genome, the inserted provirus acts as a factory for producing more retroviral RNA genomes and expressing retroviral packaging proteins. Both components combine to form viral particles that bud from the surface of the infected cells.