Bacteria triggers type-1 diabetes

Bacterial infections could be the trigger for type-1 diabetes, finds new research by Cardiff University.

For the first time, scientists have found that proteins from bacteria can trigger the immune system to attack insulin-producing cells, leading to the development of type-1 diabetes.

The new research showed that killer T-cells - a type of white blood cell that’s involved in tackling bacterial infections - can cause type-1 diabetes when activated by bacteria. The researchers showed that proteins from bacterial species known to infect humans could generate killer T-cells that could kill insulin-producing cells.

This research, led by Professor Andrew Sewell at Cardiff University’s School of Medicine, expands on their previous studies, which demonstrated that killer T-cells play a major role in initiating type-1 diabetes by killing insulin-producing cells.

Professor Sewell said: “Type-1 diabetes is an autoimmune disease that usually affects children and young adults, where the cells that produce insulin are attacked by the patient’s own immune system. This leads to a lack of insulin, meaning that people living with type-1 diabetes need to inject insulin multiple times a day to control their blood sugar levels."

In laboratory experiments, the researchers introduced bacterial proteins into cell lines from healthy donors and monitored the reaction of killer T-cells from these donors. They found that strong interaction with the bacterial proteins triggered killer T-cells to attack cells that make insulin.

The clinical lead for this study, Dr Lucy Jones, said: "We observed this in relation to a specific HLA - human leukocyte antigen - a gene that codes for proteins that help the immune system differentiate between our own cells and invading cells.

“The specific HLA associated with the bacterial infection that triggers diabetes is only present in around 3% of the population in the UK. So the bacterial pathogens that can generate anti-insulin T-cells are caused by a rare infection in a small minority of people.”

The research, published in The Journal of Clinical Investigation, provides the first evidence of how proteins from bacterial germs can trigger the type of killer T-cells seen in patients with type-1 diabetes. The team hopes that knowing more about this process, will allow new ways to diagnose, prevent, or even halt the development of type-1 diabetes.

Dr Lucy Jones said: ‘’Thanks to patients and healthcare staff being research active,  this strong research collaboration between Cwm Taf Morgannwg University health board and Cardiff University has improved our understanding of diabetes.”

The research, HLA A*24:02-restricted T-cell receptors cross recognise bacterial and 2 preproinsulin peptides in type 1 diabetes, is published in The Journal of Clinical Investigation.

The study was funded by the Wellcome Trust and Health and Care Research Wales, using facilities provided by Diamond Light Source.