Lentiviral-vector-mediated gene therapy for X-linked lymphoproliferative disease restores humoral and cellular functions

Abstract

BackgroundX-linked lymphoproliferative disease (XLP) arises from mutations in the gene encoding SAP, an intracellular adaptor protein expressed in T cells, natural killer (NK) cells, and natural killer T (NKT) cells. SAP deficiency causes abnormalities of NK cell cytotoxicity, NKT cell development, and T-cell-dependent humoral function. Clinical manifestations are characterised by haemophagocytic lymphohistiocytosis (HLH), lymphoma, and dysgammaglobulinaemia. Curative treatment is limited to allogeneic haemopoietic stem-cell transplantion (HSCT). Somatic gene therapy offers a potential cure in XLP. We have developed a lentiviral mediated gene therapy strategy to correct immune defects in XLP. MethodsWe designed a lentiviral vector incorporating codon-optimised human SAP cDNA and green fluorescent protein (GFP) driven by the elongation factor-1 short (EFS) promoter. Haemopoietic stem-cell progenitors from SAP-deficient mice were transduced with SAP-GFP (n=10) or GFP only (n=9) vectors before transplantation into irradiated SAP-deficient recipients. Animals were sacrificed 3 months later, 10 days post vaccination with NP-CGG to assess functional humoral reconstitution. FindingsBoth SAP and GFP expression was evident in bone marrow, thymus, spleen, and peripheral blood cells. NK cell cytotoxicity was restored to wild type levels in mice receiving the SAP-GFP vector, and NKT cell development was seen in SAP-GFP transduced mice at levels significantly higher than those seen in SAP-deficient or control mice. Baseline IgG, IgM, IgG1, and IgG3 levels were significantly increased and T-cell-dependent humoral responses were also restored, with SAP-GFP transduced mice having levels of NP-specific immunoglobulin that were significantly higher than SAP-deficient mice or controls. InterpretationWe demonstrate correction of cellular and humoral defects in SAP-deficient mice through lentiviral-vector-mediated gene transfer into haemopoietic progenitor cells, providing proof of concept for gene therapy in XLP. FundingWellcome Trust and Leukaemia Lymphoma Research.