In utero gene delivery by intraamniotic injection of a retroviral vector producer cell line in a nonhuman primate model

In utero gene therapy (IUGT) offers the promise of treating a wide variety of genetic diseases before the development of disease manifestations. The m ost convenient and potentially easiest method of targeting the fetus is thr ough injection into the amniotic cavity. For long-term correction of geneti c defects, retroviral vectors have great potential as a tool for gene thera py strategies. However, retroviral vectors are limited by growth to low tit ers. In an attempt to increase the amount of vector particles delivered and assess the potential of intraamniotic administration, we injected a retrov iral vector producer cell line encoding the lacZ gene into the amniotic flu id of a nonhuman primate model. After birth the infants were analyzed for v ector-mediated transduction. Two of four fetuses were successfully transduc ed, with transgene expression detected in the esophagus, trachea, and stoma ch. In some sections of tissue, nearly 100% of the cells lining the lumen o f these tissues were positive for transduction. Although successful, the li mited number of tissues in which transduction was observed led to an in vit ro analysis of the effects of amniotic fluid (AF). The presence of amniotic fluid inhibited transduction by 99%. AF affected both the transducing acti vity of the vector and the health of the packaging cells. The negative effe cts of AF were gestational age dependent; greater inhibition was observed f rom AF collected at later stages of pregnancy. The fact that transduction w as successful despite these negative effects indicates that this approach i s a promising strategy for gene therapy.