The numbers of RNA viral copies in plasma, CD4⁺/CD8⁺ T-cell ratios in the spleen, and p24 detection in the immunohistochemistry of HIV/SHIV-infected mice. (A) Viral copy numbers of 8 mice inoculated with a high infectious dose of HIV-1_JRCSF (65 000 TCID₅₀) and killed on days 33 and 43 after inoculation. (B) Viral copy numbers of 8 mice inoculated with a high infectious dose of SHIV-C2/1 (50 000 TCID₅₀) and killed on days 18 and 42 after inoculation. Note that all the mice showed high levels of viremia that lasted more than 40 days after inoculation. (C) CD4/CD8 cell ratios in the spleens of 16 infected mice and 9 uninfected control mice. Control mice were not inoculated with HIV/SHIV and were killed on days 105 to 166 after stem cell transplantation. There was no significant rapid loss of CD4⁺ cells in HIV-1_JRCSF–infected mice, while a decline of the CD4/CD8 ratio was detected in SHIV-C2/1–infected mice on day 42 after infection compared with uninfected control mice (*P < .05). The short bars indicate the means of each group. (D) P24⁺ cells are clearly observed in the spleen, LNs, and lungs. Arrow indicates p24 positive for macrophage-like cells. Original magnification, ×100.