TREX1 and tropical spastic paraparesis: Considering the unique characteristics of the genetics of the population investigated that result from interethnic crossings of Europeans, Indians, and Africans [25], this led us to the suggestion that the polymorphism (or possibly its haplotype in linkage disequilibrium) [12] may somehow influence TREX-1 regulation and HTLV-1 infection, contributing to increased proviral load and HAM/TSP pathogenesis in the tri-hybrid population investigated.