Prospects for human gene therapy

Retroviral vectors containing marker genes and the sequence for human proteins have been used to transduce cultured lymphocytes, which have then been reinfused into patients. Circulating hematopoietic progenitor cells from human fetal cord blood obtained at the time of term and premature deliveries as early as 19 weeks of gestation have been shown to express such transduced genes in vitro. Cord blood cells from fetal sheep sampled and transduced ex vivo and transfused back in utero expressed marker genes up to two years after birth. Although the efficiency of gene transfer into cells and their long-term expression need to be improved, the potential exists for treating some genetic diseases after prenatal diagnosis either in utero or shortly after birth.