Using Lentiviral Vectors as Delivery Vehicles for Gene Therapy

Viral-vector-based gene therapy is a powerful tool that allows experimental studies of species that previously were not amenable to genetic manipulation. Nonhuman primates (NHPs) are an invaluable resource for the study of genetic regulation of disease mechanisms. The main disadvantage of using NHPs as a preclinical model of human disease is the difficulty of manipulating the monkey genome using conventional gene modifying strategies. Lentiviruses offer the possibility of circumventing this difficulty by infecting and transducing dividing or nondividing cells, without eliciting an immune response. In addition, lentiviruses can permanently integrate into the genome of host cells and are able to maintain long-term expression. In this chapter, we describe the lentiviral vectors that we use to both express transgenes and suppress expression of endogenous genes via RNA interference (RNAi) in NHPs. We also discuss the safety features of currently available vectors that are especially important when lentiviral vectors are used in a species as closely related to humans as NHPs. In addition, we describe in detail the lentiviral vector �production protocol we use and provide specific examples of how this vector can be employed to target peripheral tissues and the brain. Finally, we conclude by comparing and contrasting the use of lentiviral vectors with adeno-associated viral vectors with a particular emphasis on the use of these vectors in �preclinical and clinical studies.