Research ArticleImmunodeficiency

Long-Term Persistence of a Polyclonal T Cell Repertoire After Gene Therapy for X-Linked Severe Combined Immunodeficiency

Science Translational Medicine  24 Aug 2011:
Vol. 3, Issue 97, pp. 97ra79
DOI: 10.1126/scitranslmed.3002715

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Abstract

X-linked severe combined immunodeficiency (SCID-X1) is caused by mutations in the common cytokine receptor γ chain. These mutations classically lead to complete absence of functional T and natural killer cell lineages as well as to intrinsically compromised B cell function. Although human leukocyte antigen (HLA)–matched hematopoietic stem cell transplantation (HSCT) is highly successful in SCID-X1 patients, HLA-mismatched procedures can be associated with prolonged immunodeficiency, graft-versus-host disease, and increased overall mortality. Here, 10 children were treated with autologous CD34+ hematopoietic stem and progenitor cells transduced with a conventional gammaretroviral vector. The patients did not receive myelosuppressive conditioning and were monitored for immunological recovery after cell infusion. All patients were alive after a median follow-up of 80 months (range, 54 to 107 months), and a functional polyclonal T cell repertoire was restored in all patients. Humoral immunity only partially recovered but was sufficient in some patients to allow for withdrawal of immunoglobulin replacement; however, three patients developed antibiotic-responsive acute pulmonary infection after discontinuation of antibiotic prophylaxis and/or immunoglobulin replacement. One patient developed acute T cell acute lymphoblastic leukemia because of up-regulated expression of the proto-oncogene LMO-2 from insertional mutagenesis, but maintained a polyclonal T cell repertoire through chemotherapy and entered remission. Therefore, gene therapy for SCID-X1 without myelosuppressive conditioning effectively restored T cell immunity and was associated with high survival rates for up to 9 years. Further studies using vectors designed to limit mutagenesis and strategies to enhance B cell reconstitution are warranted to define the role of this treatment modality alongside conventional HSCT for SCID-X1.

Footnotes

  • Citation: H. B. Gaspar, S. Cooray, K. C. Gilmour, K. L. Parsley, S. Adams, S. J. Howe, A. Al Ghonaium, J. Bayford, L. Brown, E. G. Davies, C. Kinnon, A. J. Thrasher, Long-Term Persistence of a Polyclonal T Cell Repertoire After Gene Therapy for X-Linked Severe Combined Immunodeficiency. Sci. Transl. Med. 3, 97ra79 (2011).

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