Outcome of repeated marginal dose SIVmac239 IR challenges.

<p>A) Challenge scheme. Macaques were exposed to SIV on day 0 and subsequently bled on days 7 and 10. Plasma collected at these two occasions was assayed for the presence of SIV RNA and a decision was made as to whether or not challenge the animals on day 14. Macaques that remained aviremic on both days 7 and 10 were re-challenged, whereas monkeys with a positive VL on either of these days were not re-challenged. For logistical reasons, vaccinees in Groups 1 and 2, as well as four monkeys in Group 5 (r04156, r02116, r05027, and r09027) were challenged for the first time at wk 14 post rRRV. The Group 3 and Group 4 vaccinees, as well as the remaining monkeys in Group 5 (r08037, r08040, r05092, and rh2313) were challenged for the first time at wk 20 post rRRV. B) Kinetics of SIVmac239 acquisition in macaques in Groups 1–5. Individual animals in each of Groups 1–4 are depicted along with the challenge that infected them (filled circles). Animal r09046 was challenged 11 times because it was aviremic on days 7 and 10 following the 10^th SIV exposure. However, a subsequent analysis revealed that this animal was viremic on day 14 post challenge #10 (i.e., also the day of the 11^th SIV challenge), indicating that it likely acquired SIV infection after the 10^th exposure. This is depicted in panel B as an additional empty circle (non-infecting exposure) placed in front of r09046 at challenge #11. Animal r08030 in Group 3 resisted 22 IR challenges with SIVmac239 (the last three at 2,000 TCID₅₀).