A genetic scientist based at University College, London, Suzanne Buckley, has successfully used HIV as a genetical material carrier or “vector” to correct faulty cystic fybrosis genes in the cells of the lungs of mice.
Suzanne Buckley is presenting her findings on Wednesday 21st March at this week’s British Society for Gene Therapy conference in Warwick. The title of her paper is “Significant lung transduction after in utero and neonatal 30 administration of lentiviral vectors”.
Cystic Fibrosis affects about 7,500 people in the UK, and is the UK’s most common life-threatening inherited disease. Its symptoms include a sticky mucous that clogs up the lungs. Lung damage is the major cause of illness and death for people with CF, and there is no cure.
Over 2 million people in the UK, approximately 4 per cent of the population, carry the gene that causes Cystic Fibrosis. If both parents are carriers, the there is a 1 in 4 chance their offspring will have the disease. To have the disease the child must inherit the faulty gene from both parents.
In 1989 an international team of scientists identified the CF gene, and established that it sits on chromosone number 7. Each human cell has 23 pairs of chromosones, each in the pair coming from each parent and carrying about 30,000 genes.
The CF gene instructs the production of a protein called CFTCR (Cystic Fibrosis Transmembrane Conductance Regulator) which moves salt and water in and out of cells lining the lungs and the digestive tract. However, in people with cystic fibrosis the CF gene is faulty and causes too much salt and too little water to be transported which produces the sticky mucous that clogs the lungs.
Gene therapy introduces the hope that a person can be treated by removing the cause of the sticky mucous, by targetting the faulty CF genes in the lungs, rather than treating the result of the disease.
The idea is to remove faulty genes and insert the correct ones, so that future generations of the cell and the organism inherit the correct code and eliminate the disease.
Viruses are used in gene therapy as “vectors” to carry corrective genes to the target host cells. They are ideal because in their natural state they invade cells of living organisms, hijack their DNA and make it obey instructions that help the virus to replicate. Retroviruses like HIV go one step further, they insert a DNA copy of their RNA and merge it with the genetic material of the host cell.
The key is to make the virus do this according to what the scientist wants to happen. This involves deactivating the dangerous part of the virus or retrovirus while keeping its ability to invade and merge with the host DNA.
Gene therapy is still a young science, and presents many challenges and risks to doctors. For instance, what if the carrier virus regains its previous potency and reverts to causing disease?
Or, what if the vector inserts the new genetic material into the wrong part of the genome, and disrupts an essential function like tumour suppression? A gene therapy trial to treat severe combined immunodeficiency (SCID) was stopped in the US when some of the patients developed leukemia.
The British Society for Gene Therapy conference in Warwick this week will also hear about a new gene therapy trial to treat SCID where it is believed some of the early days problems have been overcome.
Written by: Catharine Paddock
Writer: Medical News Today