Effect of post-challenge passive NAb immunization on primary SIV infection.

<p>(A) List of naive controls and NAb-immunized macaques. Experiments using macaques indicated by asterisk have previously been performed <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000540#pone.0000540-Matano2" target="_blank">[6]</a>. (B) Plasma viral loads after SIVmac239 challenge (SIV RNA copies/ml). Left panel, naive controls; right panel, NAb-immunized macaques shown by red lines and naive controls by gray lines for comparison. (C) Statistical analysis of plasma viral loads around 3 months post-challenge between naive controls (n = 7) and NAb-immunized macaques (n = 4). The geometric mean (indicated by the longer bar) of viral loads in naive controls is 6.5×10⁴ copies/ml, and its 95% confidence interval (indicated by the shorter bars) is 1.1×10⁴−4.0×10⁵ copies/ml. The geometric mean in NAb-immunized macaques is 9.1×10² copies/ml, and its 95% confidence interval is 1.6×10²−5.1×10³ copies/ml. The difference between the two groups was statistically significant by unpaired two-tailed t test (<i>p</i> = 0.0033) and by non-parametric Mann-Whitney U test (<i>p</i> = 0.0061). Viral loads of macaques NA1 and NA4 were calculated as the lower limit of detection shown as the dashed line (400 copies/ml). (D) Plasma NAb responses after challenge. (+), positive; (−), negative. All detected titers were no more than 1:2.