How Gene Therapy Works

Our cells contain chromosomes which are made up of strings of information recorded as DNA. The cell uses sections of this DNA called genes to make proteins. Providing a cell with a new gene can alter what proteins the cell makes. Viruses are naturally efficient at introducing a new gene into a cell. Scientists have produced viral vectors from some viruses by making them safe and unable to multiply. Gene therapy uses a viral vector to infect human cells and introduce new genes. The cell then uses these genes to make new proteins. Sometimes this replaces a protein the cell is missing, sometimes it makes an extra protein which has a useful action.

This study uses an adenovirus to infect cells. Adenoviruses normally cause coughs and colds and are very common. The virus has been changed into a viral vector so it cannot copy itself once it infects a cell. Instead it will introduce into the cell a gene for a protein called Vascular Endothelial Growth Factor (VEGF).

The viral vector will be injected into the uterine arteries of the mother, which supply the womb with blood. The cells lining the arteries will then produce more of the VEGF protein. In FGR there is a relative lack of available VEGF in the circulation. VEGF is important for protecting vessels, it causes blood vessels to dilate and new blood vessels to be formed, meaning more blood is supplied to the womb and so more nutrients and oxygen goes to the baby. Over the following month the introduced VEGF gene and the viral vector are cleared, meaning the protein is not produced forever. Studies so far suggest that the cells make VEGF for about a month, giving the baby time to grow and develop. Importantly studies also show that neither the viral vector nor the protein cross the placenta to the baby.