The role of the immune response in patients with HTLV-1 associated myelopathy/ tropical spastic paraparesis (HAM/TSP)

Human T-lymphotropic virus type I (HTLV-1) is a type C retrovirus which is associated with two major types of diseases known; adult T-cell leukemia/lymphoma (ATLL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is a chronic inflammatory of the central nervous system (CNS) that causes weakness, muscle spasms, and sensory disturbance.The virus is endemic in different parts of Iran, including northeast Iran, Mashhad, Sabzevar, and Neishabour. It is not fully understood why a small portion of HTLV-1-infected individuals develop HAM/TSP and majority remains lifelong asymptomatic carriers. The different outcome of HTLV-1 infection may be explained by the existence of viral agents, genetic background or even viral factors. High titers of HTLV-1 antibody, high proviral load and high frequency of HTLV-1 specific CTL in HAM/TSP patients distinguish them from HTLV-1 carriers. Data have shown that the interaction between the virus and the host plays a critical role in determining the risk of HTLV-1-associated diseases among HTLV-1 carriers. The quality of immune response, especially cytotoxic T lymphocytes (CTL) are critical in controlling or limiting and also the efficacy of the host response to HTLV-1.