AAV serotype 2 vectors preferentially integrate into active genes in mice

Area of Science:

• * Molecular Biology
• * Gene Therapy
• * Virology

Background:

• * Recombinant adeno-associated virus serotype 2 (rAAV2) is a key vector for gene therapy, enabling stable transgene expression.
• * While primarily extrachromosomal, rAAV2 vector genomes can integrate into host chromosomes in hepatocytes, raising concerns about insertional mutagenesis.
• * Previous studies on retroviral insertional mutagenesis highlight the need to understand rAAV2 integration effects.

Purpose of the Study:

• * To characterize the chromosomal integration sites of rAAV2 in hepatocytes from vector-injected mouse livers.
• * To investigate the host chromosomal effects, specifically deletions and gene targeting, associated with rAAV2 integration.
• * To provide insights into the nature of rAAV2 integration in quiescent somatic cells.

Main Methods:

• * Isolation and characterization of rAAV2-targeted chromosomal integration sites from hepatocytes of vector-injected mice.
• * Analysis of integration sites for chromosomal deletions and targeted genes.
• * Assessment of the expression status of targeted genes in the liver.

Main Results:

• * Frequent chromosomal deletions, up to 2 kb (100% of analyzed integrations), were observed at rAAV2 integration sites.
• * rAAV2 showed a preference for integrating into genes (72% of integrations).
• * All targeted genes analyzed (100%) were actively expressed in the liver.

Conclusions:

• * rAAV2 integration into host chromosomes in mouse hepatocytes is associated with significant chromosomal deletions.
• * Integration preferentially occurs within actively expressed genes in the liver.
• * This study provides the first characterization of host chromosomal effects of rAAV2 integration in animals, offering crucial insights for gene therapy safety.