TaqMan real-time PCR was performed as described in Materials and Methods. The y-axis shows the relative unit of a given gene normalized to GAPDH and 18s rRNA. Data are expressed as means±SEM. In all cases, average values obtained during the first eight weeks of infection were compared between recovered (X0190) and chronically infected chimpanzees (X 0234, X0142 and X6412). * P<0.05, ** P<0.01, *** P<0.01, **** P<0.005.