Correlation of HTLV-1 proviral load (PVL) and anti-HTLV-1 Ab levels by PA, CLIA, and CLEIA in serum or CSF. Upper plots show the correlations of anti-HTLV-1 Ab levels in serum by PA and PVL (A), CLIA and PVL (B), and CLEIA and PVL (C). Lower plots show the correlations of anti-HTLV-1 Ab levels in CSF by PA and PVL (D), CLIA and PVL (E), and CLEIA and PVL (F). Gray and white circles represent anti-HTLV-1 Ab levels in serum from HAM/TSP patients and HCs, respectively. Gray and white diamonds represent those in CSF from HAM/TSP patients and HCs, respectively. The vertical axis represents logarithmically transformed anti-HTLV-1 Ab levels in PA (log2 titer), CLIA (log10 S/CO), and CLEIA (log10 COI). The transverse axis represents HTLV-1 PVL in peripheral blood (copies/104 PBMCs). The line represents a simple linear regression between anti-HTLV-1 Ab levels and HTLV-1 PVL. R and P values in each plot represent Spearman’s rank correlation coefficient and the significance level of Spearman correlation analysis, respectively.