AAV integration has become an important safety consideration in gene therapy. However, accurately determining integration sites remains challenging due to biases introduced by library preparation methods, sequencing technologies, and bioinformatic pipelines. In this study, we developed a PCR-free amplification based on a CRISPR-Cas9 cleavage strategy for AAV DNA that overcomes the limitations of PCR amplification imposed by the ITR structure. When combined with long-read nanopore sequencing, this CRISPR-Cas9-based workflow preserves native AAV integration states and enables unbiased detection of integration junctions. We used AAV-transduced HeLa single-cell clones to evaluate the performance of this approach. To confirm integration site identification, AAV integration junctions were also detected using a probe hybridization capture strategy followed by Illumina short-read sequencing. Integration junctions identified by both methods were further confirmed by PCR. The results showed strong consistency between the two approaches in accurately identifying AAV integration sites in each clone. Overall, these findings demonstrate that the CRISPR-Cas9-enabled, PCR-free long-read sequencing workflow provides a promising tool for characterizing AAV integration events.
Zhang et al. (Tue,) studied this question.