A qPCR-Based Method for Quantification of Replication Competent Adenovirus (RCA) in Conditionally Replicating Oncolytic Adenoviruses

Production of conditionally replicating adenoviruses may unfortunately generate undesired replication-competent adenovirus (RCA) which raises safety concerns in clinical usage. Cell-based assays can detect RCA in batches of nonreplicating adenoviral vectors but cannot distinguish RCA from conditionally replicating oncolytic adenoviruses. Considering the great potential in using oncolytic viruses for cancer treatment, there is a need for comprehensive RCA-detection and -quantification methods. Here, we present a quantitative polymerase chain reaction (qPCR)-based assay that can be used to detect RCA particles in batches of conditionally replicating oncolytic adenoviruses. The assay is quantifying RCA by detection of the specific DNA sequence generated after a recombination event. Results showed that the method can successfully detect low levels of RCA, with a low limit of detection of ten viral particles.