Figure 2.

Between latent infection and adult T‐cell leukemia/lymphoma (ATL). Human T‐lymphotropic virus type 1 (HTLV‐1)‐infected cells express viral antigens (VA), that is, all viral products including non‐structural proteins, and virions (V) to survive and spread under host immunity (left). However, once immortalization of infected cells is complete the risk of having VA might exceed the benefit. In this model, the developing ATL acquires several genetic/epigenetic changes including a defect or methylation on proviral 5′‐long terminal repeat (LTR), resulting in the absence of all 5′‐LTR‐operated VA. The chance of immune detection of such cells becomes smaller, from which ATL arises (right). The exact timing and mechanism for proviral defects remain elusive.