Gene therapy for Wiskott-Aldrich syndrome in a severely affected adult

Abstract

Until recently, hematopoietic stem cell transplantation was the only curative option for Wiskott-Aldrich syndrome (WAS). The first attempts at gene therapy for WAS using a ϒ-retroviral vector improved immunological parameters substantially but were complicated by acute leukemia as a result of insertional mutagenesis in a high proportion of patients. More recently, treatment of children with a state-of-the-art self-inactivating lentiviral vector (LV-w1.6 WASp) has resulted in significant clinical benefit without inducing selection of clones harboring integrations near oncogenes. Here, we describe a case of a presplenectomized 30-year-old patient with severe WAS manifesting as cutaneous vasculitis, inflammatory arthropathy, intermittent polyclonal lymphoproliferation, and significant chronic kidney disease and requiring long-term immunosuppressive treatment. Following reduced-intensity conditioning, there was rapid engraftment and expansion of a polyclonal pool of transgene-positive functional T cells and sustained gene marking in myeloid and B-cell lineages up to 20 months of observation. The patient was able to discontinue immunosuppression and exogenous immunoglobulin support, with improvement in vasculitic disease and proinflammatory markers. Autologous gene therapy using a lentiviral vector is a viable strategy for adult WAS patients with severe chronic disease complications and for whom an allogeneic procedure could present an unacceptable risk. This trial was registered at www.clinicaltrials.gov as #NCT01347242.

Figure 1.

Persistent gene marking post-GT. Longitudinal results of gene marking in peripheral blood and bone marrow after GT as expressed by vector copy number per PBMC, peripheral blood purified cell lineage, or bone marrow–derived CD34⁺ cell. BM, bone marrow; NK, natural killer; VCN, vector copy number.

Figure 2.

Correction of WASp expression post-GT. (A) WASp protein expression in T cells, B cells, and natural killer cells. (B) Western blot demonstrating WASp expression in the patient’s platelets (Pt) compared with a healthy control (con). NB, patient received no platelet transfusions at any time. (C) WASp expression in purified naive CD4⁺ and CD8⁺ T cells at 20 months post-GT.

Figure 3.

Improvement of T-cell repertoire and thymic output post-GT. (A) T-cell repertoire analysis by TCR spectratyping pre- and post-GT in CD4⁺ and CD8⁺ T cells. (B) sjTREC content in CD4⁺ (red line) and CD8⁺ (blue line) T cells (dotted line corresponds to the tenth centile for the patient’s age group). TRECs, T cell receptor excision circles.

Figure 4.

Relative abundance of cell clones. Stacked bar graphs showing the relative sonic abundance, scaled as a proportion of the total. Data are separated by cell type with side-by-side comparison of time points for visualization of longitudinal changes. The 10 most abundant integration sites for each cell type are emphasized by uniquely colored bars and named by the nearest gene, indicated in the “GeneNames” key. The genes are marked with symbols to indicate further information about the integration site/gene as follows: *, the site is within a transcription unit; ∼, the site is within 50 kb of a cancer related gene; !, the gene is associated with lymphoid cancers in humans. The remaining low-abundance integration sites are indicated in gray (LowAbund). The cutoff values for binning clones as low abundance are indicated at the top of each cell-type panel.

Figure 5.

Reduction in serum cytokine levels post-GT. Multiple cytokines associated with predominantly lymphoid (A, top) and myeloid (B, bottom) cells were measured by luminex in the patient (Pt) pre- and 18 months post-GT and compared with healthy controls (HC1 and HC2).

Figure 6.

Clinical course pre- and post-GT showing a reduction in serum C-reactive protein over time. *Prednisolone 30 mg daily for 3 days; ankle swelling and cutaneous tenderness, vasculitis (?). **Prednisolone 30 mg daily for 4 days; admitted with lymphadenopathy, pyrexia of unknown origin. ***Prednisolone 30 mg daily for 3 days; foot swelling and cutaneous tenderness (self-medicated). ****Prednisolone 30 mg daily for 3 days; cutaneous tenderness and nodules (self-medicated). bd, twice daily; CRP, C-reactive protein; MMF, mycophenolate mofetil; od, once daily.