CD4 and tropical spastic paraparesis: Although CD4+/CD25+ Tregs can be infected by HTLV-1 and HAM/TSP patients have been shown to have a high number of CD4+/CD25+ Tregs with impaired function and higher HBZ mRNA levels (Araya et al., 2011; Enose-Akahata et al., 2018), the results presented here indicate that in HAM/TSP patients, HBZ protein can be detected in CD4+ T cells not displaying the classical phenotype of Treg cells.