Therapeutic DNA vaccination reduces viral load and protects from viral rebound after drug is stopped.

<p>Plasma viral RNA load was determined by real time RT-PCR. Boxed areas (ART) indicate period of antiretroviral drug therapy. Arrows indicate DNA vaccine doses. (<b>A</b>) Response to ART (weeks 0–18). Shown are viral loads in 41 SIV-infected macaques before starting ART (weeks 0–6) and during the first 12 weeks of ART only (weeks 6–18). ART responders (black) had declining viral loads during ART only. ART low responders (red) had little or no decline in viral loads during ART only and maintained ≥5×10⁴ viral RNA copies/ml (dotted line). (<b>B</b>) Log-fold reduction in viral load during ART only. The change in viral load during ART in each animal was determined by dividing the mean viral load prior to initiating ART (weeks 4–6) by the mean viral load during the first 12 weeks of ART but prior to initiating the therapeutic vaccinations (weeks 8–18). Shown is the log-fold reduction in mean viral load during ART for each animal. ART low responders had <1 log-fold reduction. ART responders exhibited 1.6–4.9 log-fold reductions in viral load during ART. (<b>C</b>) Mean plasma viral loads in each group prior to initiating ART (week 6, Pre-ART) and after 12 weeks on ART but before starting therapeutic vaccinations (week 18, Pre-vaccine). (<b>D</b>) Mean plasma viral loads during vaccinations and after withdrawing ART. Differences in mean viral loads after withdrawing ART are significant starting at weeks 68 and 48 in the DNA (P = 0.019) and DNA+LT (P = 0.002) groups, respectively, and remained significant thereafter when compared to controls (Wilcoxon test). (<b>E</b>) Viral loads in each animal. Protection from viral rebound was defined as containment of viral load ≤100 viral RNA copies/ml (hashed line) for a period of at least 5 months after drug was withdrawn (weeks 45–66).