Researchers shed light on pathway from virus to brain disease

Why people on immunosuppressant drugs for autoimmune conditions have a higher incidence of an often-fatal brain disease may be linked to a mutation in a common virus, according to researchers at Penn State College of Medicine. Progressive multifocal leukoencephalopathy (PML) is a rare disease of the brain’s white matter caused by the John Cunningham polyomavirus (JCV), a usually harmless virus that infects up to 80 percent of healthy adults. In the past, the virus usually only developed into brain disease in individuals with suppressed immune systems, such as AIDS patients and organ transplant recipients on immunosuppressant medications. Over the past decade, however, new drugs for a variety of autoimmune conditions have been identified as a key risk factor for the brain disease. The disease is now most common in multiple sclerosis patients who have the virus and who receive an immunosuppressant therapy called natalizumab. Patients with Crohn’s disease, psoriasis, rheumatoid arthritis, B cell...