Expression of β-globin in primary erythroid progenitors of β- thalassemia patients using an SV40-based gene delivery system

SV40-based vectors are very efficient in gene delivery into human hematopoietic cells. In the present work, we investigated the expression of constructs carrying the human β-globin gene that were delivered as β-globin pseudovirions. Expression studies were performed by RNA analysis of primary human erythroid progenitors cultivated from peripheral blood of β⁰- thalassemia patients who are unable to produce normal β-globin RNA. This erythroid culture system recapitulates in vitro the process of growth, differentiation, and maturation of authentic erythroid precursors. The progenitors were induced to differentiate by the addition of erythropoietin (EPO). Five days later, the cells were infected with pseudovirions containing the normal β-globin gene, and RNA was harvested on day 8. The results showed significant levels of normal β-globin gene mRNA. A small DNA fragment derived from the 5'-region of the HSII element of the human β-globin locus control region (LCR) enhanced expression of the linked β-globin gene 20-30- fold. Normal β-globin mRNA expression was in direct correlation to the multiplicity of infection. These studies suggest the potential feasibility of using the β-globin delivery system for gene therapy of β-thalassemia.