Immunopathogenesis of HTLV-1-assoaciated myelopathy/tropical spastic paraparesis (HAM/TSP).

Human T-cell lymphotropic virus type 1 (HTLV-1) is associated with adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Only a limited percentage of infected individuals develop disease in response to the virus while the majority remain asymptomatic, and HAM/TSP is the most common clinical manifestation of the virus. HAM/TSP is an inflammatory disease of the central nervous system (CNS); however, the mechanism by which HTLV-1 induces HAM/TSP is not yet clear. CD4(+) T lymphocytes are the main reservoirs of HTLV-1 in vivo and perform an important role in the immunological response to this retrovirus. This virus-host interaction may provoke changes in the immunological response, such as the enhanced production of inflammatory cytokines and the spontaneous proliferation of T CD4(+) lymphocytes, which are implicated in the pathogenesis of HAM/TSP.