Development of Lentiviral Packaging Cells and Scale Up of Production to Meet the Growing Demand in Cell and Gene Therapy.

Gamma-Retroviral (RVVs) and lentiviral vectors (LVVs) represent indispensable tools in somatic gene therapy, mediating the efficient, stable transfer of therapeutic genes into a variety of human target cells. LVVs, in contrast to RVVs, are capable of stably genetically modifying non-proliferating target cells, making them the superior instrument in cell and gene therapy. To date, the LVV manufacturing process employs human embryonic kidney cells (HEK293) and derivatives thereof transiently transfected with multiple plasmids encoding the required viral vector components. Alternatively, stable packaging cell lines were developed and engineered to express all vector components in trans. Currently, these cells are mostly cultured in cell stacks, where they grow adherently in 2D layers, limiting the scale-up of vector production. The production of viral vectors using stable suspension cell lines enables larger-scale production and higher yields under controlled conditions. Here, we review the improvements made to enhance vector safety and production yield. Current advancements in the establishment of stable packaging cell lines enabling inducible and constitutive LVV production are summarized and discussed. Manufacturing processes for lentiviral vectors using bioreactors with perfusion systems are required to meet the growing demand in cell and gene therapy and to reduce production and therapy costs.