OR22

Viral restriction factors impede the transduction efficiency of gene therapy lentiviral vectors and may be blocked to achieve therapeutic levels of gene transfer

M Dewannieux(1) M Mormin(1) K Hamon(1) C Fournier(1) A Galy(1)

1:INSERM US35 - ART-TG

Gene therapy is used to treat a growing number of pathologies. HIV-1-derived lentiviral vectors (LV) are particularly versatile tools for genetic modifications to treat different diseases with engineered hematopoietic stem/progenitor cells (HSPC) or with T cells (e.g. CAR T cells). Major improvements in strategies and vector design have facilitated LV usage. However, LV remain sensitive to restriction factors, innate immune proteins that inhibit the transduction of specific cell lineages. In particular, the protein IFITM3 is a major blockage for LV-mediated transduction. Using overexpressing cells, we showed that IFITM 3 restriction effects are dependent on the pseudotype of the vector and affect the commonly used VSVG pseudotype. We also studied IFITM3 effects in HSPC that are used for gene therapy treatments. IFITM3 is expressed in HSPCs all along the transduction process. We successfully used cyclosporin H to counteract IFITM3 in HSPC and other cells transduced with VSVG LV. Cyclosporin H reduces IFITM3 levels and enables the use of low concentrations of vectors to reach therapeutically-relevant levels of transduction. Thus, understanding the role of restriction factors in target cells enables the design of more effective vectors and transduction protocols that reduce vector doses and optimize the efficacy and safety of gene therapy.