Thus, the possible uncoupling of HBZ mRNA and protein expression in CD4+CD25+ Tregs as well as in other CD4+ T cell subpopulations in both AC and HAM/TSP patients (Yamano et al., 2009; Leal et al., 2013; Araya et al., 2014; Billman et al., 2017) certainly requires further investigation. This evidence concerns the gene HBZ and tropical spastic paraparesis.