Although the exact causes of multiple sclerosis still remain unknown, it is assumed that the disease is triggered by a combination of genetic and environmental risk factors. But which? In a mouse model of the disease, researchers at the University of Geneva (UNIGE) and the Geneva University Hospitals (HUG), Switzerland, studied the potential link between transient cerebral viral infections in early childhood and the development of this cerebral autoimmune disease later in life. Indeed, the brain area affected by viral infection during childhood undergoes a change that can call, a long time later, on the immune system to turn against itself at this precise location, triggering autoimmune lesions. These results, which are published in the journal Science Translational Medicine, provide a first step in answering one of the possible environmental causes of this serious disease.
Multiple sclerosis affects one in 1,000 people in Switzerland, two-thirds of whom are women. It is the most common auto-immune disease affecting the brain. Up to date, there is still neither a cure available, nor a clear understanding of the factors that trigger this disease at around 30 years of age. “We asked ourselves whether brain viral infections that could be contracted in early childhood were among the possible causes,” says Doron Merkler, a professor in the Department of Pathology and Immunology in UNIGE’s Faculty of Medicine and senior consultant in the Clinical Pathology Service of the HUG. Such transient brain infections can be controlled quickly by the immune system, without the affected individual even noticing any symptoms. “But these transient infections may, under certain circumstances, leave a local footprint, an inflammatory signature, in the brain,” continues the researcher.
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