A post mortem analysis of white matter of the brains of people with multiple sclerosis (MS) revealed that 12 of 15 were infected with human herpes virus type 6 (HHV-6). The virus had infected oligodendrocytes in the brain, cells that produce the myelin sheath that protects nerve fibers. The predominant characteristic of MS is loss of the myelin sheaths covering the nerve fibers. An examination of the brains of 41 individuals without MS showed no evidence of HHV-6 infection.
"A substantial body of evidence indicates that autoimmune mechanisms contribute to the pathology of MS," according to Peter Challoner, MD, and collegues at PathoGenesis Corporation in Seattle, Washington (Proceedings of the National Academy of Sciences: August 1, 1995). "HHV-6 infection early in life may establish a persistent infection in the central nervous system, with subsequent virus activation leading to cytopathic and/or immunological damage to oligodendrocytes," according to Challoner and others. The authors conclude on a cautionary note: "Although our observations demonstrate an association between HHV-6 and MS, they are insufficient to establish a causal link."