In utero somatic gene therapy in the later stages of pregnancy may allow targeting of organ systems which are difficult to reach later in life and to prevent the development of tissue damage otherwise caused by the early onset of inherited diseases. We report here on the percutaneous delivery of two adenoviral vectors, containing the β-galactosidase reporter gene and the human Factor IX gene respectively, to the fetal liver and circulation by ultrasound-guided umbilical vein puncture similar to procedures used in human pregnancy. Vector spread, as detected by PCR analysis for the β-galactosidase encoding vector, was found in almost all fetal and neonatal organs and in the maternal liver. Expression of the β-galactosidase transgene was detected in many fetal tissues by RT-PCR. High β-galactosidase production was shown by immuno-histochemistry predominantly in the liver, where about 30% of the hepatocytes stained positive, and in the adrenal cortex. Production of factor IX was determined by ELISA in the plasma of treated fetuses and newborn lambs and reached at birth up to 80% of the normal human plasma concentration. This demonstrates a very hopeful proof of principle for the development of prenatal treatment of many genetic diseases but also requires more detailed investigations with respect to the observed systemic spread of the vector.

Background Several groups including our own have reported gene delivery to fetal organs by Vector administration into the amniotic cavity. Based on these studies we hypothesised that the large surface of the fetal skin may be exploitable for high level production of systemically required gene products to be released into the fetal circulation.Methods We administered E1/E3-deleted adenoviral vectors carrying a bacterial beta-galactosidase gene or the human coagulation factor IX gene into the amniotic cavities of mid- to late-gestation mouse fetuses. The concentrations of human factor IX in the plasma of fetal or new-born mice were determined by ELISA. Reverse transcription PCR was used to identify sites of transgene expression.Results Application of 5 x 10(8) infectious units of the factor M gene vector 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 protein was found to be produced in the fetal skin, mucosae and amniotic membranes and was shown to be present for several days after birth of healthy pups.Conclusion As ultrasound-guided amniocentesis in humans is a well-established diagnostic procedure, delivery of the factor IX gene into the amniotic cavity appears to be a safe route for prenatal treatment of haemophilia B and may prevent haemorrhagic complications such as intracranial bleeding during delivery. Our study allowed for the first time a quantification of the expression of a potentially therapeutic transgene in rodents after prenatal gene delivery. It thus provides a model for the prenatal treatment of haemophilia B, but may also serve as a pathfinder to gene therapy of inheritable skin disorders such as epidermolysis bullosa. Copyright (C) 1999 John Wiley & Sons, Ltd.

With the aim of developing foetal gene therapy for cystic fibrosis, we have investigated the possibility of gene targeting to the mouse foetus with two different viral vector systems and at different times of gestation. We report here that recombinant retrovirus producing cells administered into the intra-amniotic cavity of mid- to late-gestation mouse MF1 foetuses survive in the amniotic fluid and are able to engraft to a certain extent in foetal tissues. By production of infectious virus they mediate transduction and β-galactosidase transgene expression in neighbouring foetal tissues 24 to 72 h following injection. Retrovirus producer cells could, therefore, become a means to overcome the limitations of low retroviral titre, for in vivo foetal gene transfer. To investigate the developmental stage at which transduction of the airways and enteral systems can be obtained we also administered a highly infective first generation adenoviral vector (AdRSVβgal) into the amniotic cavity of foetal mice between 13 to 16 days post coitus, β-galactosidase activity was detected between 24 to 120 h after injection. The highest levels of transgene expression were generally observed between 48 to 72 h following injection of the adenoviral vector. We demonstrate that infection of the pulmonary airways is dependent on the developmental stage of the foetus and can be achieved on the 15th day of gestation.