A packaging cell line is a specially engineered mammalian cell line that provides in trans the viral proteins and replication machinery required for the production of recombinant viral vectors — such as AAV, lentiviral, or adenoviral vectors — while the therapeutic genome is supplied by a separate transfer plasmid or expression construct. By separating the viral helper functions from the vector genome, packaging cell lines ensure that the resulting vectors are replication-incompetent and therefore biosafe for use in gene therapy applications. Commonly used packaging cell lines include HEK293, HEK293T, and stable producer cell lines developed for scalable GMP manufacturing.
