Ubiquitous high-level gene expression in hematopoietic lineages provides effective lentiviral gene therapy of murine Wiskott-Aldrich syndrome

Abstract

<jats:title>Abstract</jats:title><jats:p>The immunodeficiency disorder Wiskott-Aldrich syndrome (WAS) leads to life-threatening hematopoietic cell dysfunction. We used WAS protein (WASp)–deficient mice to analyze the in vivo efficacy of lentiviral (LV) vectors using either a viral-derived promoter, MND, or the human proximal WAS promoter (WS1.6) for human WASp expression. Transplantation of stem cells transduced with MND-huWASp LV resulted in sustained, endogenous levels of WASp in all hematopoietic lineages, progressive selection for WASp+ T, natural killer T and B cells, rescue of T-cell proliferation and cytokine production, and substantial restoration of marginal zone (MZ) B cells. In contrast, WS1.6-huWASp LV recipients exhibited subendogenous WASp expression in all cell types with only partial selection of WASp+ T cells and limited correction in MZ B-cell numbers. In parallel, WS1.6-huWASp LV recipients exhibited an altered B-cell compartment, including higher numbers of λ-light-chain+ naive B cells, development of self-reactive CD11c+FAS+ B cells, and evidence for spontaneous germinal center (GC) responses. These observations correlated with B-cell hyperactivity and increased titers of immunoglobulin (Ig)G2c autoantibodies, suggesting that partial gene correction may predispose toward autoimmunity. Our findings identify the advantages and disadvantages associated with each vector and suggest further clinical development of the MND-huWASp LV for a future clinical trial for WAS.</jats:p>

Development of gene therapy for blood disorders: an update

“…49 Full correction of the WAS phenotype was achieved in the murine model with the vector having a retroviral promoter, whereas only partial correction was achieved with the vector having the 1.6-kb WAS promoter fragment. 49 We have also found that the g-retroviral promoter is much stronger than either the EF1a or the WAS 1.6-kb promoter in various model systems.…”

“…49 Full correction of the WAS phenotype was achieved in the murine model with the vector having a retroviral promoter, whereas only partial correction was achieved with the vector having the 1.6-kb WAS promoter fragment. 49 We have also found that the g-retroviral promoter is much stronger than either the EF1a or the WAS 1.6-kb promoter in various model systems. 50 Several other studies suggested that a 1.6-kb promoter fragment from the WASp gene achieves adequate levels for correction in the preclinical model as well as normal levels of expression in human CD341 cells.…”

Recent Advances in Hematopoietic Stem Cell Gene Therapy

“…SIN lentiviral vectors using the minimal domain of the WAS promoter or other ubiquitous promoters, such as the PGK promoter, are currently being developed for WAS gene therapy. Preclinical studies using the HSCs obtained from mice or human patients have yield good results in terms of gene expression and genotoxicity [86][87][88][89][90].…”

Safe and Effective Gene Therapy for Murine Wiskott-Aldrich Syndrome Using an Insulated Lentiviral Vector

“…Because of the association between internal promoter strength and transformation potential, 19 internal promoters are selected for their ability to recapitulate endogenous expression levels and regulation, as well as for the lack of transactivation potential both in vitro and in vivo. These considerations are particularly important for treating WAS based on the following findings: sub-endogenous levels of WASp expression may hinder the reconstitution of murine B cell, T cell, and myeloid subsets and platelets; 20 insufficient WASp expression in B cells compared to T cells can drive acquisition of autoimmunity;21, 22, 23 and patients with WAS are predisposed to malignancies and clonal expansion 1, 3, 4. Current clinical trials for WAS utilize a SIN-LV with an internal promoter consisting of the proximal 1.6 kb of the endogenous WAS promoter (WS1.6) to drive human WASp (hWASp) expression 10, 12.…”