Adeno-associated virus site-specifically integrates into a muscle-specific DNA region

The nonpathogenic human virus adeno-associated virus type 2 (AAV) has evolved the potentially unique strategy to establish latency by site-specifically integrating its genome into human chromosome 19 (19q13.3-qter) at a locus designated AAVS1, This nonhomologous, site-specific recombination of viral DNA with the human genome provides a basis for developing targeted gene therapy vectors. To assess whether the region surrounding AAVS1 might have contributed to the selection of the specific integration site, we have investigated this locus. Here, we show that AAVS1 is closely linked to the slow skeletal troponin T gene, TNNT1, which has been mapped previously to 19q13.4. In support of this idea, we demonstrate that site-specific AAV DNA integration can result in the formation of TNNT1-AAV junctions. The question now arises whether muscle represents a natural target tissue for latent AAV infection. This possibility is of additional interest in view of recent observations that muscle tissue is particularly well suited for AAV-mediated gene transfer. The question also occurs whether latent infection by AAV can lead to phenotypic changes of the multinucleated muscle fiber cells.