These SIV-infected cohorts demonstrated a decline in CD4+ T cell counts from pre-SIV infection through acute and chronic SIV-infection (with mean CD4+ T cell counts of 758 cells/μl for pre-, 325 cells/μl acute-, and 127 cells/μl chronic-SIV timepoints) (Supplemental Tables 2-3). Here, CD4 is linked to infection.