Is avian adeno-associated virus an endogenous virus of chicken cells?

The adeno-associated viruses (AAV) are defective parvoviruses which produce infective progeny only in cells co-infected with a 'helper' adenovirus (Ad). Both human and simian AAV have been recovered from human and simian primary cell cultures following their inoculation with 'AAV-free' Ad. Whereas some studies have suggested that AAV exists in a latent state in these cells, others have indicated that the AAV genome is capable of establishing and maintaining a latent state in defined laboratory conditions which mimic the situation proposed for the 'latent' AAV recovered from human and simian tissues. Here, avian adeno-associated virus (AAAV) was consistently recovered from limiting dilutions of purified and unpurified avian Ad stocks propagated in embryonating chicken eggs derived from two independently raised flocks of White Leghorn (WL) chickens but not when these Ad stocks were propagated in duck cells. These observations suggest that AAAV is a latent endogenous virus of at least some flocks of WL chickens.