Can a Tuberculosis Vaccine Combat Type 1?
Human trials show the vaccine might repair the pancreas in those who have long had Type 1.
Sometimes, promising Type 1 diabetes treatments are developed from treatments for other conditions. If you have Type 1 diabetes, there’s good reason to be interested in what’s happening with the BCG vaccine, a treatment used to curb the spread of tuberculosis.
BCG stands for “bacillus Calmette-Guerin,” a weakened strain of bacteria that has been used in humans for over 90 years, typically for the prevention of tuberculosis. In the US, we don’t routinely give the BCG vaccine because there’s a relatively low risk of contracting this lung disease. Around the world, however, infants are routinely immunized with this safe and well-tested drug. Although BCG therapy has had mixed results in treating Type 1 diabetes in past trials, more recent studies show promise, especially in people who have been living with the disease for some time.
One of the things that BCG does is stimulate the production of a hormone called tumor necrosis factor (TNF). Studies conducted in our lab at Massachusetts General Hospital over a decade ago showed that temporarily elevating TNF helps to reverse Type 1 diabetes in mice, in part by stopping the autoimmune attack on the pancreas. This allows the pancreas to heal, regenerate, and begin to produce some insulin again.
We were able to translate these findings into human clinical trials using the BCG vaccine. Our Phase I study showed that repeat BCG vaccination in people who had been living with Type 1 diabetes for an average of 15 years could kill the “bad” white blood cells that attack the pancreas, leading to early signs of pancreatic repair, accompanied with a temporary boost in insulin production. Following these positive results, a Phase II trial will soon start to see if BCG might be an effective treatment for those with advanced diabetes. We hope to show long-term beneficial effects, including greater blood sugar control, less insulin use, and fewer diabetic complications.
BCG is being studied around the world as a treatment for autoimmune conditions. An institute in Turkey is now looking more closely at repeat BCG vaccination in early life, after seeing evidence that such a regimen might help prevent Type 1 diabetes. In the United States, trials are being planned to investigate the vaccine as a treatment for Sjögren’s syndrome, an autoimmune condition characterized by dry eyes and dry mouth. And in Italy, researchers have shown in a Phase II trial that repeat BCG vaccination may be able to reverse the effects of multiple sclerosis.
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