In light of our results, the fact that only a small percentage of HTLV-1 infected individuals eventually develop HAM/TSP might be partially attributed to the neuro-protective nature of the HTLV FP, demonstrated here by its ability to specifically downregulate IFN-γ secretion from pathogenic T-cells in EAE and to alleviate and delay disease onset. Here, IFNG is linked to tropical spastic paraparesis.