Vaccine for diabetes is step nearer

THE PROSPECT of a vaccine against type 1 diabetes has come a step closer with a discovery that might explain why tens of thousands of Britons have developed the disease.

Scientists have identified key events that lead to the destruction of insulin-producing cells in the pancreas by the body's own immune defences. Sufferers of type 1 diabetes, sometimes called insulin- dependent diabetes, need daily injections of the hormone to control their blood-sugar levels, or risk blindness, loss of limbs and death.

The discovery could lead to a "therapeutic" vaccine that might prevent the disease in people at risk of developing it.

Diabetes often occurs in childhood and is thought to result from inheriting a genetic predisposition triggered by some unknown environmental factor, causing development of an auto-immune response - when the immune system attacks its own tissues.

It has been known for years that type 1 diabetes can occur as a result of the immune system's "killer" white blood cells attacking the islet cells in the pancreas, which are responsible for insulin production.

But scientists did not know until now what was the biochemical trigger in the pancreas. Researchers at Yale University have now found that the trigger is insulin itself. Susan Wong, head of the research team, found that the killer cells are stimulated into an attack by recognising parts of the insulin molecule sticking to the surface of the islet cells.

Research published in the journal Nature Medicine showed the trigger stimulates the early destruction of pancreas cells in a strain of laboratory mouse that suffers from the human form of diabetes. "I think ultimately we will [develop a vaccine] but when is difficult to predict. Hopefully in a few years it might be possible," Dr Wong said.

The research has not, however, shed light on why some people develop the disease. "Diabetes type 1 occurs as a result of a combination of genetic susceptibility and an environmental trigger. We don't yet know what this trigger is," Dr Wong said.

More than 20,000 young people under 20 are thought to have developed type 1 diabetes and studies suggest the number of new cases has grown several fold over the past 40 years.

The British Diabetic Association (BDA) said a number of environmental factors, such as viruses and chemicals, are being investigated for their possible role in triggering type 1 diabetes.

Scientists have also identified a number of genes - as many as six - that appear to be involved in conferring susceptibility. "If a person possesses these genes, it does not necessarily mean that they will actually develop diabetes; it is only if they encounter the environmental trigger that the auto- immune destruction of the islet cells will be initiated," the BDA said.