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 (reviewed in [28]) as well as HBZ mRNA expression levels comparable to those observed in ATL [29], the results presented in this paper indicate that in HAM/TSP patients HBZ protein expression can be easily found in CD4+ T cells not displaying the classical phenotype of Treg cells. This evidence concerns the gene CD4 and tropical spastic paraparesis.