HBZ and tropical spastic paraparesis: Namely, HBZ mRNA expression was significantly higher in patients with HAM/TSP with tax subgroup-B than in those with tax subgroup-A in HTLV-1-infected cells, and there is a positive correlation between the expression of HBZ mRNA and its target Foxp3 mRNA in patients with HAM/TSP with tax subgroup-B, but not in patients with tax subgroup-A.