Oh et al. evaluated the clinical and virological efficacy of escalating doses of IFN-β (30 μg once a week up to 60 μg twice a week) during a 28-week period in a small number of HAM/TSP patients (n = 12) whose disease duration ranged from 2 to 20 years [84]. This evidence concerns the gene IFNB1 and tropical spastic paraparesis.