Induction of cellular and humoral immune responses against HTLV-1 in infected IBMI-huNOG mice. (A) Detection of HTLV-1–specific HLA-A*24:02-restricted CTLs. Splenocytes from HTLV-1–infected mice at 8 wpi were stained with human CD8 and Tax301-309 tetramer or HIV-1 env gp160 tetramer as a negative control, respectively. Representative results of tetramer-positive CD8 T cells in vivo (left) and ex vivo culture with Tax peptide (right) are shown. (B) Inverse correlation between PVL and the frequency of Tax301-309–specific CTLs. The percentages of tetramer-positive CD8 T cells and PVL in the spleens of 18 HTLV-1–infected mice are shown. One dot represents the result of an individual HTLV-1–infected mouse. Spearman’s rank-correlation coefficient (r²) was used to identify statistically significant correlations. (C) HTLV-1–specific antibody responses in HTLV-1–infected mice. HTLV-1–specific antibody titers in plasma were monitored by the particle agglutination method. Each bar represents an individual mouse. The plasma of indicated mice prior to infection were used as negative-controls (shown as 0 wpi), and these titers were undetectable level (<16). Mice with daggers (mouse ID: X207 and X214) showed biphasic induction of antibody responses; titers peaked at 8 wpi. (D) Detection of HTLV-1–specific IgM or IgG antibody. Antibody depletion was performed by addition of goat antibodies against human IgG or IgM and anti-goat antibody conjugated magnetic beads to the plasma of two mice, as shown in panel C (indicated by daggers). Bars represent antibody titers in the individual X207 and X214 mice. Ab, antibody.