Adeno-associated Virus Genome Population Sequencing Achieves Full Vector Genome Resolution and Reveals Human-Vector Chimeras
Tai, Phillip W. L. ; Xie, Jun ; Fong, Kaiyuen ; Seetin, Matthew ; Heiner, Cheryl ; Su, Qin ; Weiand, Michael ; Wilmot, Daniella ; Zapp, Maria L ; Gao, Guangping
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Abstract
Recombinant adeno-associated virus (rAAV)-based gene therapy has entered a phase of clinical translation and commercialization. Despite this progress, vector integrity following production is often overlooked. Compromised vectors may negatively impact therapeutic efficacy and safety. Using single molecule, real-time (SMRT) sequencing, we can comprehensively profile packaged genomes as a single intact molecule and directly assess vector integrity without extensive preparation. We have exploited this methodology to profile all heterogeneic populations of self-complementary AAV genomes via bioinformatics pipelines and have coined this approach AAV-genome population sequencing (AAV-GPseq). The approach can reveal the relative distribution of truncated genomes versus full-length genomes in vector preparations. Preparations that seemingly show high genome homogeneity by gel electrophoresis are revealed to consist of less than 50% full-length species. With AAV-GPseq, we can also detect many reverse-packaged genomes that encompass sequences originating from plasmid backbone, as well as sequences from packaging and helper plasmids. Finally, we detect host-cell genomic sequences that are chimeric with inverted terminal repeat (ITR)-containing vector sequences. We show that vector populations can contain between 1.3% and 2.3% of this type of undesirable genome. These discoveries redefine quality control standards for viral vector preparations and highlight the degree of foreign products in rAAV-based therapeutic vectors.
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Mol Ther Methods Clin Dev. 2018 June 15;9:130-141. doi: 10.1016/j.omtm.2018.02.002. eCollection 2018 Jun 15. Link to article on publisher's site