Lentiviruses are also part of the Retroviridaeย family and are structurally similar to ฮณ-retroviruses. The main difference (and advantage) of lentiviruses is that they are able to transduce both dividing and non-dividing cells. To increase the safety of lentiviral vectors, the components necessary for virus production are split across multiple plasmids (3 for 2nd-generation systems, 4 for 3rd-generation systems). Third-generation, self-inactivating lentiviral vectors have recently been used in multiple clinical trials to introduce genes into hematopoietic stem cells. These vectors have also been used to introduce genes into mature T cells to generate immunity to cancer through the delivery of chimeric antigen receptors (CARs) or cloned T-cell receptors.