Both macaques also developed a rapid decrease in peripheral blood levels of CD4+ T cells from an average of 914 ± 121 cells/μL (CD4:CD8 ratio of 0.715 + 0.2) before inoculation to persistently low levels of 75 – 150 cells/μL (CD4:CD8 ratio of 0.01 – 0.09) blood during primary infection (Fig 6). Here, CD4 is linked to infection.