Collectively, the evidence positions the BCL-2 family as a critical determinant of deltaretroviral persistence and leukemogenesis, and as a promising therapeutic axis for the development of novel treatments for HTLV-1–Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) and BLV-associated leukosis. Here, BCL2 is linked to tropical spastic paraparesis.