[HTLV-1: Recent topics in epidemiologic, basic and clinical research]

Human T-cell leukemia virus type 1 (HTLV-1) belongs to Delta Retorviridae, and induces a malignancy of CD4+CD25+ T-cells, adult T-cell leukemia (ATL), and several chronic inflammatory diseases, such as HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) and HTLV-1 uveitis. A nationwide survey of HTLV-1-infected subjects, which was recently conducted by Japanese government, revealed that the numbers of HTLV-1 carriers and patients with HTLV-1-associated diseases have not decreased much over the last two decades in Japan. In contrast, novel findings on HTLV-1 dynamics in vivo and molecular mechanisms of its pathogenesis are accumulating by detailed analysis of newly identified viral and cellular factors, novel technologies such as next-generation sequencing, and appropriate animal models for HTLV-1 research. In this review, we summarize the recent progress of HTLV-1 research.