Successful expression of beta-galactosidase and factor IX transgenes in fetal and neonatal sheep after ultrasound-guided percutaneous adenovirus vector administration into the umbilical vein

In utero somatic gene therapy in the later stages of pregnancy may allow ta rgeting of organ systems which are difficult to reach later in life and to prevent the development of tissue damage otherwise caused by the early onse t of inherited diseases. We report here on the percutaneous delivery of two adenoviral vectors, containing the beta-galactosidase reporter gene and th e human Factor IX gene respectively, to the fetal liver and circulation by ultrasound-guided umbilical vein puncture similar to procedures used in hum an pregnancy. Vector spread, as detected by PCR analysis for the beta-galac tosidase encoding vector, was found in almost all fetal and neonatal organs and in the maternal liver Expression of the beta-galactosidase transgene w as detected in many fetal tissues by RT-PCR. High beta-galactosidase produc tion was shown by immuno-histochemistry predominantly in the liver, where a bout 30% of the hepatocytes stained positive, and in the adrenal cortex. Pr oduction of factor IX was determined by ELISA in the plasma of treated fetu ses and newborn lambs and reached at birth up to 80% of the normal human pl asma concentration. This demonstrates a very hopeful proof of principle for the development of prenatal treatment of many genetic diseases but also re quires more detailed investigations with respect to the observed systemic s pread of the vector.