Figure 6. HTLV-1–infected trophoblasts induce de novo infection in humanized mice.

(A) Schematic of the experimental schedule. After humanization, 9 mice were inoculated i.p. with HTLV-1–harboring placental cells at 0 dpi (VT, n = 3; VMF, n = 3; PVEC, n = 3). Arrowheads indicate the time points of blood collection. All mice were observed carefully during the experimental period at 42 dpi. (B) Cell surface expression level of HTLV-1 envelope glycoprotein was analyzed in primary placental cells cocultured with MT-2 cells. The cells were stained with anti–HTLV-1 gp46 mAb or mouse IgG1 mAb as an isotype control. Representative cells (left) and the percentages of HTLV-1 gp46–positive cells (right) are shown. Data are means ± SD of 3 independent experiments. (C) Quantification of HTLV-1 PVL in the peripheral blood of inoculated mice. HTLV-1 PVL was determined by real-time PCR at 14, 28, and 42 dpi. One dot represents the result of an individual mouse. Undetected samples were given an arbitrary value of 10⁰. (D and E) Human CD45⁺ leucocytes, CD3⁺ lymphocytes, total CD4⁺ T cells, and CD25⁺ T cells were routinely analyzed by flow cytometry. One dot represents the result of an individual mouse. The absolute numbers of human CD45⁺ leucocytes are shown in D. Frequencies of lymphocytes positive for the indicated marker are shown in E. CD3⁺ lymphocytes were gated to analyze the populations of CD4⁺ and CD25⁺ T cells. Asterisks represent significant differences versus the data for VTs in B, or PVEC-inoculated mice in C–E. *P < 0.05, **P < 0.01 by 1-way ANOVA followed by Dunnett’s multiple-comparisons test. ND, not detected.