AAV breakpoint detection and security monitoring based on high-throughput sequencing

Adeno-associated virus (AAV) has been widely used in gene therapy due to its high-efficiency gene delivery capability. However, its complex genomic structure, particularly the importance of inverted terminal repeats (ITRs) in viral replication and packaging, poses significant challenges for quality control. To ensure the safety and efficacy of AAV products, precise genomic analysis is essential.

Next-generation sequencing (NGS), as a well-established high-throughput sequencing technology, plays a crucial role in AAV analysis due to its high throughput, deep coverage, and quantitative analytical capabilities. Compared to traditional detection methods, NGS enables the rapid generation of large-scale genomic data, facilitating comprehensive analysis of AAV from multiple aspects, including mutation profiling, residual impurity assessment, and structural integrity evaluation.

Comprehensive AAV Analysis Using NGS

By leveraging NGS technology, researchers and manufacturers can conduct in-depth assessments of AAV products across multiple dimensions, such as sequence accuracy, residual impurity analysis, structural evaluation, and safety monitoring, ensuring the quality and safety of gene therapy products.

1. Genomic Integrity and Mutation Detection

Genomic integrity is critical for the safety and efficacy of AAV-based gene therapies. Even minor mutations or deletions can impact vector replication efficiency, functional stability, and potentially trigger immune responses. Therefore, verifying AAV genomic accuracy and mutation rates is essential.

NGS enables comprehensive analysis of the entire AAV genome, detecting low-frequency mutations and ensuring the validation of critical regions, including ITRs. This allows researchers and manufacturers to precisely monitor the genomic status of AAV vectors.

2. Structural and Functional Evaluation of the ITR Region

The ITR region serves as a fundamental structural component of the AAV genome, playing a pivotal role in viral replication and packaging. In particular, self-complementary AAV (scAAV) and other specialized vector designs rely on ITR structural stability. Any recombination or mutation in the ITR region can lead to functional failure. Therefore, evaluating the structure and functionality of ITRs is a key focus in AAV quality control.

Figure 1. Schematic diagram of AAV replication

Next-generation sequencing (NGS), through short-read assembly, enables precise detection of minor mutations and structural variations within the ITR region. Compared to Sanger sequencing, NGS offers significant advantages in analyzing complex structures, such as inverted repeat regions. Additionally, NGS can identify low-frequency recombination events, helping researchers uncover unexpected variations in the AAV genome, thereby improving product consistency and stability.

3. Detection of AAV Genome Terminal Structure Integrity

The integrity of the AAV genome’s terminal structure is critical for its replication and packaging efficiency. Any terminal breakage or deletion can impair AAV functionality in vivo, diminishing the intended therapeutic effect. This is particularly important for self-complementary AAV (scAAV) or AAV vectors with specific ITR modifications (such as mITR), where any ITR incompleteness can directly affect vector stability and function.

Therefore, breakpoint analysis—especially assessing the integrity of the 3' and 5' terminal sequences—has become a key step in AAV quality control.

Fig. 2. Schematic of AAV 3' end breakpoint detection

The high-throughput AAV breakpoint detection service launched by Levostar focuses on the precise analysis of AAV genome termini. It provides quantitative detection, breakpoint identification, and analysis of abnormal structures such as large-scale insertions, deletions, or inversions. This service enables rapid detection of unexpected structural changes in specially designed vectors, ensuring the integrity of all functional regions in AAVs. By continuously monitoring genomic breakpoints, Levostar‘s breakpoint detection service offers strong support for the consistency and integrity of AAV products, enhancing the safety and efficacy of gene therapy.

4. AAV Safety Testing: Production Residues and Host Genome Integration Detection

The production purity and safety of AAV are crucial for the clinical application of gene therapy. During production, residual plasmid scaffolds and host cell genomes may affect the biosafety of AAV products. Plasmid residues may trigger immune responses, while host genome residues could cause adverse reactions in clinical settings, and potentially pose a cancer risk. Additionally, although AAV is generally considered a non-integrating virus, under certain conditions, it may integrate into the host genome, leading to genomic instability and increasing the risk of tumors. Therefore, AAV quality control must not only strictly monitor production residues but also closely track its integration into the host genome.

By designing specific primers or using target enrichment techniques, NGS can focus on detecting plasmid and host genome sequences, identifying and quantifying the specific components and proportions of residues, offering a more comprehensive residual detection compared to traditional qPCR methods. Moreover, NGS can sensitively identify small amounts of AAV-host chimeric sequences, helping to detect potential genomic integration events and accurately pinpoint insertion sites.

Thanks to its high sensitivity and coverage, next-generation sequencing (NGS) has become the ideal choice for AAV genomic analysis. Whether for genomic integrity, production residues, or breakpoint detection, NGS meets the multifaceted quality control needs. Particularly in breakpoint detection, NGS’s precise recognition of AAV structures ensures vector functionality and stability in gene therapy, providing solid safety assurances for clinical AAV applications.