Adeno-associated virus integrates site-specifically into human chromosome 19 in either orientation and with equal kinetics and frequency

Adeno-associated virus type 2 (AAV-2) establishes latency by site-specific integration into a unique locus, AAVS1, on human chromosome 19 (chr19). To study the kinetics and frequency of chr19-specific integration, a rapid, sensitive and quantitative real-time PCR assay specific for AAV inverted terminal repeat (ITR)-chr19 junction sequences was developed. Since the assay only detected right-hand AAV ITR-specific integration events, the development of a complementary left-hand ITR-specific real-time PCR assay is described. The time-course of left-hand ITR-dependent AAV integration at AAVS1 of chr19 was determined in AAV-2-infected HeLa cells. Both the kinetics and frequencies of left-hand ITR-dependent integration were found to be similar to those of the right-hand ITR. In addition, left-hand ITR-specific fusion sequences and chromosomal breakpoints within AAVS1 were variable, yet were the same as those found in right-hand ITR-chr19 junction sequences. Thus, the AAV-2 genome integrates site-specifically into chr19 with similar efficiency in either orientation.