HLA-B and tropical spastic paraparesis: On the other side, molecular data from southern Japan indicates that the alleles HLA-A*02 and Cw*08 (HLA class I) are associated with a significant reduction in both HTLV-1 proviral load and the risk of HAM/TSP, whereas HLA-B*5401 (HLA class I) and HLA-DRB1*0101 (HLA class II) predispose to HAM/TSP in the same population [9,10].