Retroviral gene transfer and sustained expression of human arylsulfatase A

Transduction of mouse hematopoietic stem cells and their progeny was studied using a recombinant retroviral vector (MFG-ASA) which incorporates the human arylsulfatase A gene (ASA; EC 3.1.6.8). Successful transduction was demonstrated in spleen colonies of mice that received bone marrow transplantation, cultured bone marrow-derived macrophages, visceral tissues and brain of long-term reconstituted mice, and also the spleen colonies of secondarily transplanted mice. The efficiency of transduction in primary spleen colonies was 90%. Expression of the ASA transgene exceeded endogenous levels in spleen colonies and in cultured macrophages by 50-100%. Enzyme activity in the visceral tissues of long-term reconstituted mice consistently showed elevated ASA activity, greater than three-fold in the spleen and lung of one animal. Increased activity of ASA also could be detected in secondary spleen colonies. These data demonstrate the usefulness of the MFG-ASA vector for efficient gene transfer and expression in mouse hematopoietic stem cells and their differentiated progeny. The presence of vector DNA in the brain 4 months after transplantation suggests a role for gene transfer and stem cell transplantation in the treatment strategies for metachromatic leukodystrophy.