Furthermore, direct ex vivo analysis of tetramer+CD4+ T cells from two unrelated DRB1*0101-positive HAM/TSP patients indicated that certain T-cell receptors (TCRs) Vβs were utilized and antigen-specific amino acid motifs were identified in complementarity determining region (CDR) 3 from both patients. Here, HLA-DRB1 is linked to tropical spastic paraparesis.