Cross-sectional analysis of the HAM/TSP cohort by Western Blot demonstrated that 69.4% (25/36) were positive for HTLV-1 Tax in exosomes isolated from cultured PBMCs, while no Tax positive (Tax+) exosomes were produced from cultured PBMC of HTLV-1 seronegative controls (0/12) (Fisher exact test: p-value = 0.0001). The gene discussed is CNTN2; the disease is tropical spastic paraparesis.