Spontaneous In Vivo Reversion of an Inherited Mutation in the Wiskott-Aldrich Syndrome

Abstract

The Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency disease, arising from mutations of the WAS-protein (WASP) gene. Previously, we have reported that mononuclear cells from WAS patients showed lack/reduced of the intracellular WASP (WASPdim) by flow cytometric analysis, and analysis of WASP by flow cytometry (FCM-WASP) was useful for WAS diagnosis. In this study, we report a WAS patient who showed the unique pattern of FCM-WASP. The patient had the small population of normal expression of WASP (WASPbright) mononuclear cells together with the major WASPdim population. The WASPbright cells were detected in T cells, not in B cells or in monocytes. Surprisingly, the molecular studies of the WASPbright cells revealed that the inherited mutation of WASP gene was reversed to normal. His mother was proved as a WAS carrier, and HLA studies and microsatellite polymorphic studies proved that the WASPbright cells were derived from the patient himself. Therefore, we concluded that the WASPbright cells were resulted from spontaneous in vivo reversion of the inherited mutation. Furthermore, the scanning electron microscopic studies indicated that WASP-positive cells from the patient restored the dense microvillus surface projections that were hardly observed in the WASPdim cells. This case might have significant implications regarding the prospects of the future gene therapy for WAS patients.

Gene therapy for Wiskott-Aldrich syndrome: rescue of T-cell signaling and amelioration of colitis upon transplantation of retrovirally transduced hematopoietic stem cells in mice

“…[38][39][40][41] More recently, 2 groups reported that spontaneous reversions of the WASP mutation in hematopoietic cells from WAS patients led to significant somatic mosaicism in T cells but not B cells. 42,43 We now extend these studies by providing direct evidence for a selective advantage of WASP-expressing cells following HSCT.…”

Lentiviral vectors transcriptionally targeted to hematopoietic cells by WASP gene proximal promoter sequences

“…The proximal WASP gene promoter in the context of a SIN lentiviral vector may have useful characteristics for clinical trials of gene therapy for WAS as it achieves hematopoietic-specific and physiologically relevant levels of WASp. Expression of the WASP transgene confers a selective growth advantage to transduced T cells as described in spontaneous reversions of WAS patients [29][30][31] as well as in other models of CD3-activated WASp + cells. 32,33 This observation indicates that the protein expressed in WW-transduced cells is functional.…”

“…[29][30][31][32][33] Therefore, HVS-WAS/1 cells were transduced with the WW lentiviral vector at MOIs of 0.01, 0.1 and 1 and kept in culture for 39 days. The percentage of WASpexpressing cells was analyzed by flow cytometry at days 7, 27 and 39 after transduction.…”

Functional correction of T cells derived from patients with the Wiskott–Aldrich syndrome (WAS) by transduction with an oncoretroviral vector encoding the WAS protein

“…In support of the critical role of T-cell dysfunction in WAS, two recent reports of clinical improvement in patients whose peripheral T cells had been partially repopulated by spontaneous revertant wild-type populations suggest that gene-corrected T cells have a significant, and efficacious, proliferative advantage over WASP-deficient cells. 12,13 Both patients survived longer than would be otherwise expected, and in one patient clinical improvement was attributed to emergence of the revertant T-cell population. Efforts at correction of T-cell function by gene transfer are therefore a logical first step toward genetic correction of WAS.…”