HTLV-1 infection and the viral etiology of multiple sclerosis.

The HTLV-1 virus produces a progressive inflammatory, and then degenerative, myelopathy which evolves progressively from onset. HTLV-1 in endemic in populations which are recognized as having low risk of multiple sclerosis . Multiple sclerosis generally evolves as a relapsing-remitting disease and affects predominantly Caucasians. In Caucasians, HAM/TSP can be marked by fluctuations as well as relapses. In Asians MS affects preferentially the spinal cord. The author hypothesizes that population selection through environmental factors has pushed the immune response of Caucasians towards generating relapsing-remitting disease and that of Primordial populations towards progressive disease. HTLV-1 endemicity being the marker of Primordial populations and its absence that of Caucasians.