Restoration of Lymphoid Populations in a Murine Model of X-Linked Severe Combined Immunodeficiency by a Gene-Therapy Approach

Abstract

X-linked severe combined immunodeficiency (XSCID) is a life-threatening syndrome in which both cellular and humoral immunity are profoundly compromised. This disease results from mutations in theIL2RG gene, which encodes the common cytokine receptor γ chain, γc. Previously, we generated γc-deficient mice as a murine model of XSCID. We have now used lethally irradiated γc-deficient mice to evaluate a gene therapeutic approach for treatment of this disease. Transfer of the human γc gene to repopulating hematopoietic stem cells using an ecotropic retrovirus resulted in an increase in T cells, B cells, natural killer (NK) cells, and intestinal intraepithelial lymphocytes, as well as normalization of the CD4:CD8 T-cell ratio and of serum Ig levels. In addition, the restored cells could proliferate in response to interleukin-2 (IL-2). Thus, our results provide added support that gene therapy is a feasible therapeutic strategy for XSCID. Moreover, because we used a vector directing expression of human γc to correct a defect in γc-deficient mice, these data also indicate that human γc can cooperate with the distinctive cytokine receptor chains such as IL-2Rβ and IL-7R to mediate responses to murine cytokines in vivo.