HIV-1 replication and pathogenesis in DKO-hu HSC mice. Intravenous infection of HIV-R3A at high (A-B) and low (C-G) doses was performed in DKO-hu HSC mice. (A) NL4-R3A stock (5 ng p24 or 20 000 IU/mouse) was used to infect DKO-hu HSC mice (HIV DKO-HSC, solid diamond and square) and DKO mice (HIV DKO, crosses). Two DKO-hu HSC mice were also mock infected as controls (mock DKO-HSC, open diamond and square). Plasma samples were collected at 1, 2, 3, 4, and 12 weeks after infection and HIV genome copy numbers were determined. The sensitivity of detection is 500 copies/mL due to necessary sample dilution. (B) Human CD4⁺ T-cell number in the blood of DKO-hu HSC mice was determined at 15 weeks after HSPC transfer (1 week prior to HIV infection, −1 week after infection), and determined again at 1, 2, 3, 4, and 12 weeks after infection. (C) DKO-hu HSC mice were infected with low-dose NL4-R3A (1 ng p24 or 4000 IU/mouse). Plasma HIV genome (triangle, left Y axis) and CD4 cell counts (diamond, right Y axis) in mouse no. 3 (Table 1) are shown. (D) FACS analysis of CD45⁺ thymocytes by costaining p24 with CD4 or of CD45⁺CD4⁺ lymph node cells with CD45RO from mice infected with NL4-R3A (1 week after infection). (E) Immunohistochemistry was performed with anti-p24 antibody on paraffin sections of lymphoid tissues. Lymph node (i), thymus (ii), spleen (iii), and the hematoxylin and eosin (H&E) staining of adjacent section of the spleen (iv). Arrows in subpanels iii and iv indicate the CD45⁺ follicles in the spleen. Slides were observed under a Nikon Microphot FXA microscope equipped with a PlanApo 4×/0.20 numerical aperture (NA) i-ii) or a PlanApo 2×/0.08 NA (iii-iv) objective lens (Nikon, Garden City, NY). Images were captured using a QImaging Micropublisher 3.3 CCD digital camera and QCapture software version 3.0 (QImaging, Surrey, BC, Canada). (F) Depletion of CD4⁺ T cells in lymphoid organs. At 1 week after infection, human CD4 and CD8 in the thymus and lymph nodes of mock- or NL4-R3A–infected mice were analyzed by FACS. The percentage of each population is indicated. (G) Thymocytes (4500 CD45⁺ cells) or splenocytes (17 000 CD45⁺ cells) from mouse no. 4 (Table 1) harvested at 19 weeks after infection were cocultured with PHA-activated PBMCs to detect infectious HIV-1 (p24/mL). Similar results were observed with cells from mouse no. 3 at 14 weeks after infection.