Type 1 Diabetes: Tuberculosis Vaccine Could Offer "Major Advancement" in Treatment

A diabetic injects insulin. It’s possible a century-old tuberculosis vaccine could present a “major advancement” against Type 1 diabetes. But critics urge caution. Getty Images

Every day, thousands of Americans prick their fingers and stab their legs, bellies and buttocks four, five—maybe even 10 times a day. The CDC estimates more than 30 million people in the U.S. have diabetes, and about 5 percent of these have Type 1.

Now, researchers writing in npj Vaccines have found evidence that a humble, century-old tuberculosis vaccine can send blood glucose levels dramatically down in a small but long-term study of patients with advanced Type 1 diabetes.

However, critics have questioned the size of the study, and urged the public to eye the results with caution.

Type 1 diabetes is an autoimmune disease in which the normally protective immune system switches sides and turns on its own body, destroying the insulin-secreting islet cells of the pancreas. Without this hormone, sugar can build up and languish in the bloodstream.

Day-to-day, patients and their families try to strike an impossible balance between the disease's fatiguing highs and debilitating lows, influenced by everything from exercise to diet to menstruation. Type 1 diabetes typically strikes in childhood or adolescence and, eventually, years of high sugar levels can damage everything from the eyes to the heart to the nerves at the tips of your toes.

In this trial, doctors gave diabetic subjects two doses of the bacillus Calmette-Guérin (BCG) vaccine one month apart. Invented nearly 100 years ago, it's considered extremely safe and has been used routinely in children around the world to prevent tuberculosis.

After three years, patients showed a fairly dramatic long-term reduction in average blood sugar levels—indicated by HbA1c test results—that were sustained for five more years. Improvements certainly weren't sudden, taking upward of three years to appear, but they were impressive, study author Denise Faustman told Newsweek.

Although the results sound promising for this cheap, low-tech vaccine, the patient cohort was very small. Only three patients with diabetes received the BCG at the start of the trial. After these first patients began to improve, researchers added another six to the study. One hundred and eleven more have since joined the phase-one trial, STAT reported. The npj Vaccines paper focuses on those who have reached five years of follow-up and included control and reference participants to strengthen the results.

Not only did patients' Hba1c results improve by more than 10 percent on average at eight years' follow-up, but participants were also able to reduce their insulin intake. This in itself, Faustman explained, is remarkable and potentially life-changing for the patients involved. "[Diabetes is] a tortuous disease. You're living on the edge every day, 24/7, and things can go wrong any single day, let alone the long-term complications," the researcher, based at Massachusetts General Hospital, added. "To be able to get blood sugars into the safe range with something that doesn't require an injection every day, doesn't require a pill, is extremely long-lasting and is something that will certainly be welcomed."

What's particularly distinctive about this study, Faustman said, is its participants. Most research focuses on prevention of diabetes or the treatment of early onset cases, but this study looked at patients with advanced diabetes who had lived with the disease for about 15 to 20 years. "No-one dared to go into people with the disease because if you can't cure new onset, you're never going to be able to make a dent in these people that have the disease," she said.

Although the results seem novel, Faustman's team built on a wealth of previous research, she explained. Rather than focusing on expensive and high-tech treatments, they turned to a cheap, well-studied antique.

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Scientists have previously observed the effect of the BCG vaccine on other autoimmune conditions and allergies in humans and in rodents. Published trials have linked certain BCG substrains to a slowdown in diabetes progression in new-onset cases, but others haven't shown the same benefits, Faustman and colleagues reported in npj Vaccines.

In this study, basic science analysis revealed hungry white blood cells could be behind the decline in blood sugar. In participants who'd taken the BCG vaccine, white blood cells seemed to be guzzling up excess sugar. "BCG is an organism that wants to live inside white blood cells, and it wants to have a lot of energy sources," Faustman said. "It takes those white blood cells and elevates the sugar utilization."

What's more, the hungry cells knew when to stop snacking. "Effectively, instead of having a pancreas to regulate blood sugar...their white blood cells are taking sugar out of the blood in a regulated fashion," Faustman said. This is important because Type 1 diabetics frequently experience low blood sugar when they inject too much insulin, or when factors like exercise make their body more responsive to the hormone.

Although the results seem promising, experts have highlighted the limits of the study.

Immunology professor Daniel Davis from the University of Manchester, in the U.K., said the public should be cautious about the results because of the small size of the cohort. He told the U.K.'s Science Media Centre (SMC): "This discovery does not yet lead to a definitive public health message for patients with diabetes—in part because relatively small numbers of patients have been studied here."

Andrew Hattersley, a professor of molecular medicine at the University of Exeter Medical School, in the U.K., told SMC the study involves "far too small a number of people studied to suggest this should be considered a potential treatment for people living with Type 1 diabetes."

More data, Faustman says, is on the way. A phase two clinical trial is taking place at Massachusetts General Hospital, testing BCG vaccines in 150 patients, STAT reported. Faustman told Newsweek she hopes to begin pediatric trials if her team can secure funding.

"I hate the word 'cure' because it means something different to everybody," Faustman added. "But I think it's a major advancement.... It has simplicity."

The trial reported in npj Vaccines is funded in large part by the Iacocca Family Foundation, which was started in 1984 by ex-Chrysler CEO Lee Iacocca, whose wife died of diabetes complications.