CNTN2 and tropical spastic paraparesis: HTLV-1-Tax-specific antibody is elevated in HAM/TSP patients compared with both ACs and ATLL patients (Lal et al., 1994; Chen et al., 1997), and HTLV-1 specific antibody could distinguish HAM/TSP from ACs and ATLL (Enose-Akahata et al., 2012).