Association of viral load decrease with raltegravir treatment of SIVmac251-infected animals (Group 2). SIVmac251-infected rhesus macaques (Macaca mulatta) received 100 mg of raltegravir twice daily with food (bid). Monotherapy was continued for ten days. Comparison between pre- and post-raltegravir viral load measurements was done. Viral load values at Day 0, Day 7 and Day 10 were compared with viral loads at 27 and 166 days prior to treatment start. Significant differences (P < 0.05; Bonferroni's test following repeated-measures ANOVA; shown in the graph by the red asterisks) were found between both the values at 166 and 27 days prior to treatment start and the values at Day 7 and Day 10 of treatment. No significant differences, instead, were found between the values at 166 days, or 27 days, prior to treatment, and the values at Day 0. The dashed line parallel to the x axis marks the detection threshold of the technique adopted.