CXCL9 and tropical spastic paraparesis: In addition, higher CSF levels of Th1-related chemokines CXCL9 and CXCL10 are also present; they strongly correlate with the HTLV-1 proviral load (PVL) in peripheral blood mononuclear cells (PBMCs) and with the speed of HAM/TSP progression [10,11].