The clonal expansion of human T lymphotropic virus type 1-infected T cells: A comparison between seroconverters and long-term carriers

Background. The clonal expansion of human T lymphotropic virus type 1 (HTLV-1)-infected T cells is considered to be important for the maintenance of infection. However, the process by which the clonality of HTLV-1 -infected T cells is established is not understood. Methods. HTLV-1 clonality in 4 adult seroconverters was analyzed by inverse long polymerase chain reaction (PCR) followed by cloning of the PCR products and evaluation of restriction fragment - length polymorphism. The results were compared with those for 8 long-term HTLV-1 carriers. Results. The clonality of HTLV-1 - infected T cells in the seroconverters arose stochastically and was variable 3 - 5 years after seroconversion. On the basis of the frequency with which clones of cells infected with unique HTLV-1 provirus integration sites appeared, it was clear that the seroconverters had a greater number of unique clones with fewer infected cells than did the long-term carriers. Conclusions. The clonality of the HTLV-1 - infected T cells in the adult seroconverters, who had been newly infected via HTLV-1 - carrier spouses, was more heterogeneous and less stable than that of the HTLV-1 - infected T cells in long-term carriers, who were more likely to have been infected during infancy. The mechanism for the selective maintenance of certain clones in asymptomatic HTLV-1 carriers likely plays a role in the initiation of leukemogenesis.