EFFICIENT RETROVIRUS-MEDIATED TRANSFER AND EXPRESSION OF A HUMAN ADENOSINE-DEAMINASE GENE IN DIPLOID SKIN FIBROBLASTS FROM AN ADENOSINE DEAMINASE-DEFICIENT HUMAN

Skin fibroblasts might be considered suitable recipients for therapeutic genes to cure several human genetic diseases; however, these cells are resistant to gene transfer by most methods. We have studied the ability of retroviral vectors to transfer genes into normal human diploid skin fibroblasts. Retroviruses carrying genes for neomycin or hygromycin B resistance conferred drug resistance to to greater than 50% of the human fibroblasts after a single exposure to virus-containing medium. This represents at least a 500-fold increase in efficency over other methods. Transfer was achieved in the absence of helper virus by using amphotropic retrovirus packaging cells. A retrovirus vector containing a human adenosine deaminase (ADA) cDNA was constructed and used to infect ADA- fibroblasts from a patient with ADA deficiency. The infected cells produced 12-fold more ADA enzyme than fibroblasts from normal individuals and were able to rapidly metabolize exogenous deoxyadenosine and adenosine, metabolites that accumulate in plasma in ADA-deficient patients and are responsible for the severe combined immunodeficiency in these patients. These experiments indicate the potential of retrovirus-mediated gene transfer into human fibroblasts for gene therapy.