HTLV-I and chronic nervous diseases: present status and a look into the future.

Three entities--multiple sclerosis, tropical spastic paraparesis, and human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM)--may represent manifestations of the same disease, with HTLV-I-like virus playing a role in their etiology. Tests for the presence of antibodies reacting with either HTLV-I-like virions or with p24 (gag) antigen, expression of HTLV-I antigen by cells of peripheral blood lymphocytes or cerebrospinal fluid, and viral sequences detected by in situ hybridization are essential to establish the role of HTLV-I-like virus in the disease. It is not yet known whether an incomplete form of the virus persists in the tissue following initial infection or whether the virus in question shares the gag protein with HTLV-I but carries the envelope of a different virus. It is recommended that investigative units comprising neurologists and laboratory workers be established as soon as possible to pursue vigorously the leads that may throw some light on the etiology of chronic neurological diseases such as multiple sclerosis.