CNTN2 and adult T-cell leukemia/lymphoma: In the case of HTLV-1, the virally encoded Tax protein directs a multitude of intracellular functions promoting the survival and proliferation of infected cells, but it is also a powerful antigen in the evolution of an anti-HTLV-1 immune response; indeed, progression from chronic HTLV-1 infection to adult T-cell leukaemia often coincides with the reduced expression of the Tax protein (Kannagi, 2007).