A Scalable and Accurate Method for Quantifying Vector Genomes of Recombinant Adeno-Associated Viruses in Crude Lysate

Abstract

Increasing interest and application of recombinant adeno-associated viruses (rAAVs) in basic and clinical research have urged efforts to improve rAAV production quality and yield. Standard vector production workflows call for genome titration of purified vectors at the endpoint of production to assess yield. Unfortunately, quality control measures for preparations during mid-production steps and economical means to assess the fidelity of multiple batches of rAAV preparations are lacking. Here we describe a scalable and accurate method for the direct quantitative polymerase chain reaction (qPCR) titration of rAAV genomes in crude lysate. Lysate samples are pretreated with DNase I to remove vector and packaging plasmid DNAs, followed by proteinase K to release endonuclease-resistant packaged viral genomes and to proteolyze factors inherent to crude lysates that can impinge upon quantitative PCR efficiencies. We show that this method is precise, scalable, and applicable for vector genome titrations of both single-stranded and self-complementary AAV genomes irrespective of serotype differences—a major limitation for standard lysate transduction methods that indirectly screen for vector packaging efficiency. Our described method therefore represents a significant improvement to rAAV vector production in terms of alleviating time and cost burdens, in-process quality control assessment, batch/lot monitoring in large-scale preparations, and good manufacturing practices.