Date Published: 19 July 2006

Aicardi Goutieres syndrome (AGS) reveals new insight into immune responses

Research into a rare genetic condition has unexpectedly shed new light on how the body defends itself against viral infections and the processes involved in autoimmune diseases like lupus. The work is published in two papers in Nature Genetics.

Babies affected with Aicardi Goutieres syndrome (AGS) have problems closely resembling those caused by viral infections such as rubella and cytomegalovirus when they are acquired during pregnancy. However, AGS is caused by abnormal genes rather than a virus.

In a collaboration led by Dr Yanick Crow, scientists from the University of Leeds Institute of Molecular Medicine, the Medical Research Council (MRC) and Cancer Research UK have identified four of the genes that cause AGS. These genes make enzymes called nucleases. The absence of these nucleases in AGS triggers an immune response in a baby like that seen following infection in the womb.

Dr Crow from the Leeds Institute of Molecular Medicine said:

" Aicardi Goutieres syndrome is a genetic disease that mimics congenital infection. Absence of the nucleases that cause AGS triggers an immune response to the baby's own DNA and RNA. This response is similar to that mounted against DNA and RNA carried by infectious agents such as viruses, hence the overlap in clinical features.

_ This immune response mechanism is also likely to be important in autoimmune diseases such as lupus. During the normal life-cycle of our cells, nucleases clean up naturally produced waste DNA and RNA. Failure of this process means that the body mounts an immune reaction against itself."

Dr Andrew Jackson of the MRC Human Genetics Unit explained:

" Nucleases are enzymes that are found in all cells in the body. Their job is to breakdown DNA and RNA into their component parts. Scientists have long understood how these particular nucleases work, but the discovery of their relationship to innate immune response was unexpected. The research results suggest that the genes that cause AGS may help us to understand more about the body's immune response to viruses like rubella and cytomegalovirus. Understanding exactly how the body defends itself will help in the long term to identify more effective treatments for viral infections and autoimmune diseases."

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