ISG15 and tropical spastic paraparesis: Integrating the data from Tattermusch et al. (2012), Dos Santos et al. (2018), Sawada et al. (2017) and this study, we hypothesize that an “IFN-beta like/TRIM5” gene signature vs. a “non-IFN-beta like/ISG15” gene signature might be predictive of HAM/TSP disease progression, as well as of therapeutic outcome with immunomodulatory and/or antiproliferative drugs (IFNs, glucocorticoids and others).