Molecular mimicry turns viral infection into diabetes
Some children, who catch a common form of gastroenteritis, may be at risk of triggering the onset of diabetes through their body's reaction to the viral infection, Australian researchers have found.
The Melbourne study, reported in New Scientist, may provide new leads to understanding how some auto-immune diseases are triggered by environmental influences.
Margo Honeyman from the Walter and Eliza Hall Institute of Medical Research has found that infection with a rotavirus, a type of gastro-enteritis which infects almost all young children, may trigger type I (childhood) diabetes in susceptible individuals.
Dr Honeyman noticed that some parts of the virus proteins are very similar to proteins on the surface of pancreatic cells. Because of this similarity, the body's immune system could attack both the invading virus, and the body's own pancreatic tissues. Diabetes I develops when the immune system attacks pancreatic cells, stopping them from freely producing sugar-controlling insulin.
There is currently much scientific interest in identifying environmental factors which may trigger autoimmune diseases such as Lupus, Multiple Sclerosis and type I diabetes.
Dr Honeyman followed the development of 54 babies with a genetic predisposition for diabetes over six years to see how the rotavirus affected their immune system. She found that the 24 children who went on to develop diabetes experienced a big jump in anti-pancreatic anti-bodies every time they became infected with rotavirus. By contrast, the rest of the study group did not suffer an immune attack on the pancreas following a rotavirus infection.
At this stage it's not clear how the virus might induce diabetes. It may infect then damage pancreatic cells, or mimic the pancreatic proteins that cause the immune system to attack.
Last year one rotavirus vaccine was withdrawn from sale in the US after fears it caused bowel constrictions in young children. Now this Australian research raises questions about developing future rotavirus vaccines.
In a sense, introducing a vaccine in to the body is like introducing the infection. Both trigger an immune response. The fear is that if the virus is mimicking the body's own cells, it could be a problem: "if it's mimicry alone, or both infection and mimickry, the vaccines may be dangerous," Dr Honeywell said.