Gene therapy used to treat canine blood disorder
The study has 'set the stage' for human clinical trials of the treatment. (stock photo)
Scientists have managed to treat a rare bleeding disorder in dogs using a single injection of gene therapy. The research offers significant potential for treating the same condition in humans.
Factor VII deficiency is caused by a gene mutation that inhibits normal production of the blood clotting factor.
It affects around one in 300,000 and one in 500,000 people and ranges in severity, with around 40 per cent of sufferers classed as having severe disease. Treatment usually involved regular infusions of the clotting factor.
Researchers from the Children's Hospital of Philadelphia used gene therapy on four dogs identified as having naturally occurring factor VII deficiency. This involved introducing DNA carrying the code to producing the specific clotting factor.
An adeno-associated virus which does not cause disease was bioengineered and used as a vector to deliver DNA to the cells where it can express enough factor to make the blood clot normally.
The team worked in collaboration with researchers from the University of North Carolina (UNC), who identified four dogs for the study from their established colony of dogs for haematology research.
The selected dogs were injected with varying dosages of the gene therapy and monitored over a period of several years. According to the findings published in the journal Blood, the dogs expressed levels of factor VII that would be therapeutic in humans with long-term stability. For one dog, the effects lasted for nearly three years.
"Our finding has great clinical relevance for patients with factor VII deficiency," said lead author Paris Margaritis, a haematology researcher at the Children’s Hospital of Philadelphia. "These dogs have the type of mutation found in the majority of patients with this disorder, so this approach could lead to a sustained gene therapy in people."
Based on kidney and liver function and blood measurements, the treatment proved safe and did not cause unwanted immune responses.
The study has 'set the stage' for human clinical trials of the treatment and researchers say it could be particularly beneficial for young children with severe bleeding due to factor VII defiency.
"This work is very exciting and promising…" said co-author Tim Nichols from the UNC School of Medicine. "In other related studies in dogs with hemophilia B, similar positive findings have translated to people with hemophilia B."
Both Prof Nichols and Margaritis agreed: "The table is now set to propose clinical trials that would treat people who suffer from FVII deficiency."
Veterinary practices are being urged to help owners safely dispose of any unused and expired pet medicines - not just antibiotics - during November's Animal Medicines Amnesty. 
