Before injections of TCID5O for SIVmac239 infection, the average scores of CD4 T-cell count, CD8 T-cell count, and CD4/CD8 ratio were 1120.79 ± 514.25, 605.81 ± 201.47, and 1.96 ± 0.78, respectively. The gene discussed is CD8A; the disease is infection.