Figure 5. Time to infection and viral loads upon SIVmac251 challenges.

Vaccinated and control RMs were challenged 10 times with SIVmac251 given rectally. Viral titers were measured, and for SIVΔnef-vaccinated RMs, positive samples were retested by a nef-specific nested PCR. (A) Percent of animals that remained virus-free after each challenge. (B) Viral titers measured after each challenge. Transient viral spikes in SIVΔnef-immunized RMs and low titers at the end in BD20 and 4340 could not be amplified by the nef-specific PCR. The two animals of the SIVΔnef group that resisted infection are shown with dotted lines.