A clinical trial for a Type 1 diabetes vaccine has resulted in promising findings, suggesting there may be a future where we can prevent people from getting the disease.
Researchers completed a 12-week trial on a DNA-based vaccine on 80 subjects with Type 1 diabetes. The patients were able to maintain levels of a blood-borne intermediary that can stimulate insulin production, and some subjects were able to increase levels. That suggests the cellular changes that occur in patients with Type 1 diabetes may be shut down.
"We're very excited by these results, which suggest that the immunologist's dream of shutting down just a single subset of dysfunctional immune cells without wrecking the whole immune system may be attainable," study author Dr. Lawrence Steinman, professor of pediatrics and neurological sciences at Stanford University in Calif., said in a press release. "This vaccine is a new concept. It's shutting off a specific immune response, rather than turning on specific immune responses as conventional vaccines for, say, influenza or polio aim to do."
Type 1 diabetes affects up to 3 million Americans, the study authors noted. While it isn't as common as Type 2 diabetes, it typically manifests at an earlier age and requires multiple daily injections of insulin throughout life.
In Type 1 diabetes, the immune system attacks its own beta cells, a cell found in the pancreas. Beta cells store and release insulin, which is a hormone necessary to turn sugar -- or glucose -- into energy for the body's use. It is unknown what causes Type 1 diabetes.
The experimental vaccine works by targeting and suppressing a set of immune cells called CD8, which are thought to attack insulin-producing beta cells. When different cells make proteins, they put small segments of the protein called peptides on their surfaces so "patrolling" CD8 cells can inspect them. CD8 ignores most peptides on healthy cells, but when a peptide looks out of the ordinary, it attacks the cell.
One hypothesis about Type 1 diabetes is that a patient has confused CD8 cells that incorrectly read a protein called proinsulin -- which the body uses to make insulin out of -- as foreign. The proinsulin-targeting CD8 cells then attack the beta cells that the proinsulin is resting on.
The vaccine that is being tested, called TOL-302, contains DNA that codes for proinsulin. When the body processes the vaccine, it sends an anti-inflammatory signal to only the CD8 cells. This then tells the proinsulin-targeting CD8 to leave the beta cells alone.
The researchers tested the vaccine through weekly shots in Type 1 diabetic patients. They were randomized to receive four different doses and a placebo shot. Researchers measured the levels of C-peptide, a portion of proinsulin that gets removed when insulin is made, in the patients' blood stream. Levels were measured during the fifth and 15th weeks and then six, nine, 12, 18 and 24 months after starting on the vaccination regimen. Each time, researchers took blood samples 30, 60, 90 and 120 minutes after patients drank a modified milkshake.
Since C-peptide remains in the body longer than insulin, it can serve as a good intermediary between beta cells and further insulin production. C-peptide has also been shown to stop or reduce some of the long-term effects of diabetes including eye, kidney and nerve damage.
This trial was initially done to find out about dosing and the safety of the vaccine. However, the results revealed more. The researchers found that amounts of proinsulin-targeting CD8 cells -- but not any other Types of immune cells -- were much lower in people who had received the vaccine, compared with those who got the placebo. However, C-peptide remained the same or even increased in some cases.
A DNA-based vaccine has never been approved by the Food and Drug Administration (FDA), and many more trials with more subjects need to occur, the researchers said. In addition, the vaccine's effectiveness dropped after the 12-week period, so the current formula may not offer long-term protection. Experts say a working vaccine is still years away, but this trial's results are promising and a good start.
"For the first time we have evidence that this particular type of vaccine has an effect in preserving insulin production in humans. This is a significant step forward on the journey towards a world without Type 1 diabetes," Karen Addington, the UK chief executive of the Type 1 diabetes charity Juvenile Diabetes Research Foundation, said to the BBC. "We will build on this exciting DNA vaccine approach."
The study was published on June 26 in Science Translational Medicine.