Retrovirus-mediated WASP gene transfer corrects defective actin polymerization in B cell lines from Wiskott-Aldrich syndrome patients carrying 'null'mutations

Boys affected with Wiskott-Aldrich syndrome (WAS) present with variable ass ociation of thrombocytopenia, eczema and immune deficiency. If untreated, W AS patients may succumb to intracerebral hemorrhages, severe infections or malignancies. Allogeneic bone marrow transplantation (BMT) can cure all asp ects of the disease, but HLA-identical donors are not available to all pati ents and mismatched BMTs are unfortunately associated with high mortality a nd morbidity. The good success of HLA-matched BMT, however, makes WAS a pot ential candidate for hematopoietic stem cell gene therapy. WAS patients car ry mutations of the Wiskott-Aldrich syndrome protein gene encoding WASP, a 502-amino acid proline-rich protein with demonstrated involvement in the or ganization of the actin cytoskeleton. To verify the feasibility of genetic correction for this disease, the WASP cDNA was expressed in EBV-immortalize d B cell lines obtained from WAS patients using a retroviral vector. Transd uced WAS cells showed levels of WASP expression similar to those found in c ells from normal donors, without detectable effects on viability or growth characteristics. In addition, retrovirus-mediated expression of WASP led to improvement of cytoplasmic F-actin expression and formation of F-actin-pos itive microvilli, a process shown to be defective in untransduced WAS cell lines. These preliminary results indicate a potential use for retrovirus-me diated gene transfer as therapy for WAS.