The class 1 HLA genotype of the host, which determines the antigen specificity and quality of the CTL response, therefore determines the proviral load and the risk of HAM/TSP [44]; in southern Japan, HLA-A*02 and Cw*08 are associated with protection against HAM/TSP, whereas HLA-B*54 is associated with a higher risk of the disease [58]. Here, HLA-A is linked to tropical spastic paraparesis.