682. Correction of CTLs Cytotoxic Function Defect by SIN-lentiviral Mediated Expression of Munc13-4 in Type 3 Familial Hemophagocytic Lymphohistiocytosis

Abstract

Patients with mutations in UNC13D gene, coding for Munc13-4 protein, suffer from type 3 Familial hemophagocytic lymphohistiocytosis (FHL3), a life-threatening disorder of the immune system. Munc13-4 controls docking of lytic granules before they fused with the plasma membrane in cytotoxic T and NK lymphocytes and it's defect results in defective cytotoxic function of these cells. Hematopoietic stem and progenitor cell (HSPC) transplantation, which is the only curative treatment for FHL3 to date, is partially successful even when a compatible donor is available because of the important inflammatory background of patients. In this context gene therapy could be a promising therapeutic option especially for those patients without any compatible donor. As Munc13-4's function is to allow proper cytotoxic activity in mature cytotoxic CD8+ T cells we proposed that these laters may constitute target for gene correction. We constructed a self-inactivating HIV-1 derived lentiviral vector encoding human Munc13-4 in two different pseudotypes, the high tropism VSV-G and the measles virus glycoproteins (H/F) envelope which target more efficiently lymphoid cells through the signaling lymphocyte activation molecule (SLAM) as described by Verhoeyen et al. 2011. We demonstrated that both vectors are able to stably transduce FHL3 CD8+ T cells resulting in correction of defective degranulation capacity of these cells. However comparative analysis showed that H/F pseudotyped vector was more efficient than VSV-G vector to transduce FHL3 T cells. Adoptive transfer of the gene-corrected FHL3 T cells in SCID mice bearing autologous B-LCL lymphoma led to significant tumor regression due to an efficient homing into the tumor mass and long persistence of corrected T cells in peripheral blood as compared to non-corrected T cells receiving mice. Our study shows for the first time that a lentiviral mediating gene transfer in T cells could be proposed to treat a hemophagocytic lymphohistiocytosis disorder.