BST2 and tropical spastic paraparesis: In conclusion, our integrated ex vivo approach reveals that antiretroviral genes in HTLV-1 infection and HAM/TSP cluster in two distinct “proviral/antiviral” classes, of which the TRIM5α/TRIM22/BST2 antiviral subset, selected during recent primate evolution, is selectively up-regulated by IFN-β signaling in HAM/TSP.