Like all retroviruses, lentiviruses can integrate into a host genome by converting their single stranded RNA genome into double-stranded DNA. However, unlike other retroviruses, lentiviruses can transduce nondividing and quiescent cells, which make lentiviral vectors a popular choice for gene transfer within cell therapy.
Specifically, lentiviral vectors are often used for the development of ex vivo cell therapies including chimeric antigen receptor (CAR-T) cell therapies, where they represent a useful tool for gene delivery . This is at least in part because introducing lentiviral vectors to cells outside the body reduces the risk of insertional mutagenesis in off-target populations and improves targeting compared with in vivo use.
Lentiviral vectors encode the necessary components to deliver gene transfer to cells and are usually constructed from plasmids. Approaches for building lentiviral vectors have changed over time, with third-generation vectors that contain only a fraction of the original viral genes considered safer than previous iterations. Third-generation lentiviral packaging systems comprise four plasmids, and some systems have been further modified, for example OXGENE’s lentiviral packaging plasmids have been engineered to improve packaging efficiency, transgene expression and overall viral yield. In addition to the evolving approaches for building lentiviral vectors, manufacturing processes and testing requirements also change over time.