IFNA1 and tropical spastic paraparesis: First, we confirm that exacerbated IFN signaling is a hallmark of HAM/TSP disease status [32], being significantly higher in incident HAM/TSP (Fig. 5A), as compared to healthy controls (fivefold, p = 0.022) and AS (fourfold p = 0.0085), when quantified ex vivo by nCounter.