Plasma viral RNA levels in RT-SHIV infected macaques. Panel A shows viral RNA (copies/ml) from four macaques that were pretreated with a single 30 mg dose of DMPA (depot medroxyprogesterone acetate, Depo Provera®) for 30 days before intravaginal challenge with 500 or 1000 TCID50 of RT-SHIV. Panel B shows viral RNA from four macaques that were not pretreated with DMPA before virus challenge. Panel C represents the mean viral loads of four RT-SHIV infected macaques in the DMPA-treated or in the untreated group. In the non-DMPA group, viral RNA data from macaque 03042 were not available after 14 weeks post infection because this macaque was euthanized. The viral load of each plasma sample collected at various weeks pi (x-axis) was tested by standard branched chain DNA amplification assay.