CD4 and tropical spastic paraparesis: HTLV-1 is the etiological agent of Adult T-cell Leukemia/Lymphoma (ATLL), a malignant lymphoproliferation of T CD4+ cells [2], [3] and of HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis, a chronic neurological inflammatory disease (HAM/TSP) [4], [5], [6].