Therapeutic plasma concentrations of human factor IX in mice after gene delivery into the amniotic cavity: A model for the prenatal treatment of haemophilia B

Background Several groups including our own have reported gene delivery to fetal organs by Vector administration into the amniotic cavity. Based on th ese studies we hypothesised that the large surface of the fetal skin may be exploitable for high level production of systemically required gene produc ts to be released into the fetal circulation. Methods We administered E1/E3-deleted adenoviral vectors carrying a bacteri al beta-galactosidase gene or the human coagulation factor IX gene into the amniotic cavities of mid- to late-gestation mouse fetuses. The concentrati ons of human factor IX in the plasma of fetal or new-born mice were determi ned by ELISA. Reverse transcription PCR was used to identify sites of trans gene expression. Results Application of 5 x 10(8) infectious units of the factor M gene vect or in utero resulted in plasma concentrations of human factor IX of up to 1 .2 mu g/ml without significant decrease in fetal survival. Transgenic prote in was found to be produced in the fetal skin, mucosae and amniotic membran es and was shown to be present for several days after birth of healthy pups . Conclusion As ultrasound-guided amniocentesis in humans is a well-establish ed diagnostic procedure, delivery of the factor IX gene into the amniotic c avity appears to be a safe route for prenatal treatment of haemophilia B an d may prevent haemorrhagic complications such as intracranial bleeding duri ng delivery. Our study allowed for the first time a quantification of the e xpression of a potentially therapeutic transgene in rodents after prenatal gene delivery. It thus provides a model for the prenatal treatment of haemo philia B, but may also serve as a pathfinder to gene therapy of inheritable skin disorders such as epidermolysis bullosa. Copyright (C) 1999 John Wile y & Sons, Ltd.