December 1, 1998
Researchers discover new treatment for deadly heart virus
TORONTO - Researchers at The Hospital for Sick Children (SickKids), the Toronto Hospital and the University of Toronto (U of T) have carried out studies which could lead to a new way to treat viral myocarditis, an inflammation of the heart leading to heart failure and, ultimately, the need for a transplant. Their research is reported in the December issue of the scientific journal Nature Medicine.
"When this virus attacks the heart it triggers the production of an enzyme called elastase that destroys heart cells and creates scar tissue. The scar tissue makes the heart less flexible, reducing its ability to pump blood. Within a year, the heart fails entirely. We've identified a drug that cuts elastase off at the pass, preventing it from carrying out its destructive work," explains Dr. Marlene Rabinovitch, head of Cardiovascular Research at The Hospital for Sick Children and a Professor of Paediatrics at the University of Toronto.
Myocarditis is caused by a strain of the virus that is associated with common gastroenteritis. Researchers don't yet know why the virus has such a variable effect on patients, but some of their work suggests that this might be related to the body's natural ability to produce inhibitors of elastase in various tissues such as the intestine or the heart.
Dr. Rabinovitch carried out her research in mice, using an animal model developed and characterized by co-investigator Dr. Peter Liu of the Centre for Cardiovascular Research at the Toronto Hospital and Professor of Medicine at U of T. When the mice are inoculated with the myocarditis virus, they develop features which reproduce those seen in patients with myocarditis. Following inoculation, some mice were treated orally with an elastase inhibitor. The treated mice had no or minimal scarring and their heart function and structure were maintained.
Myocarditis affects infants and children as well as adults. Approximately 12 cases of viral myocarditis are seen annually at SickKids. Up to one third of those patients will develop severe heart dysfunction. Two or three of those patients will require transplantation. Dr. Rabinovitch hopes that these studies will soon lead to clinical trials using elastase inhibitors in patients with viral myocarditis. An intravenous elastase inhibitor has already been proven safe for premature infants with chronic lung disease.
This research was funded by The Heart and Stroke Foundation of Ontario, the Medical Research Council of Canada, and The Hospital for Sick Children Foundation.
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