Stable cell lines for inducible production of rAAV virions

Production of recombinant adeno-associated virus (AAV) via the expression of a nucleic acid encoding Rep and Cap proteins and a second nucleic acid encoding adenoviral helper proteins, such as E2A and E4. Either nucleic acid is conditionally expressed. Exemplified is recombinant AAV production in HEK 293 cells via an inducible Cre/LoxP system wherein the Rep gene comprises an intron flanked by LoxP sites. Rep is conditionally expressed due to Rep toxicity. A second plasmid comprises E2A and E4 genes and an inducible Cre recombinase. Cre expression is induced via tamoxifen which excises the disruptive intron to induce Rep protein expression. There is also a plasmid comprises a transgene for packaging into the AAV, for example for gene therapy. The Rep intron may comprise a marker, such as GFP. The cells may also express VA genes and auxotrophic selection markers, such as DHFR. The DHFR sequence may be split across two sequences and functional DHFR formed via a leucine zipper for selection.