HBZ and tropical spastic paraparesis: The protein derived from the antisense transcripts produced from the 3′ LTR of HTLV-1, called HBZ, together with the hbz mRNA, has shown to play a crucial role in HTLV-1 replication and its associated pathologies (ATLL, HAM/TSP; Gaudray et al., 2002; Satou et al., 2006; Barbeau et al., 2013; Barbeau and Mesnard, 2015; Tagaya et al., 2019; Matsuoka and Mesnard, 2020).