CCL1 and tropical spastic paraparesis: It is noteworthy that there was no correlation between serum CCL1 levels and HTLV-1 PVL or tax mRNA expression in PBMCs, and there was no statistical significance between plasma CCL1 levels and the disease severity (i.e., OMDS) of HAM/TSP patients, suggesting that the plasma CCL1 levels of HAM/TSP patients were not reflected by changes in levels of HTLV-1 PVL or tax mRNA expression in the systemic circulation.