HLA-DRB1 and tropical spastic paraparesis: Because HLA-C*07:02, HLA-B*07:02, DRB1*01:01, and HLA-DQB1*05:01 together constitute a haplotype, it is most likely that DRB1*01:01 is the susceptible allele to HAM/TSP, because it contains DRB1-GB-7-Leu.