ERVW-1 and tropical spastic paraparesis: We conclude that HBZ-specific antibody responses in CSF of HAM/TSP patients were significantly weaker than the response to other HTLV-1 antigens such as Gag, Env and Tax, because antibody responses against these molecules can be found in both serum and CSF; in certain patients the titers are higher in CSF than in plasma [25].