IFNL3 and tropical spastic paraparesis: On the other hand, IL-28B is an essential part of antiviral immunity through intracellular signaling and several antiviral factors activated in cells; although there are few studies on the association with HTLV-1, it has been demonstrated that polymorphisms in IL-28B, specifically, rs8099917 and rs12979860 are related to the progression of the infection and play a role in the origin of HAM.