To examine whether clonal expansion by antigen stimulation is detected in proliferating HTLV-1–infected T cells, TCR clustering was analyzed in the expanded clonotypes (≥ 8 UMIs) of paired CADM1–CD4+ T cells and CADM1+CD4+ T cells sorted from PBMCs of patients with HAM/TSP and ACs using the GLIPH2 algorithm. This evidence concerns the gene CD4 and tropical spastic paraparesis.