Fig. 2: Agreement between predicted versus experimental serum neutralization ID₈₀ titer.

Sera from samples from the last visit (and for a subset from the last two visits) and before the first positive HIV-1 RNA PCR test were assayed against autologous isolates from 64 VRC01 recipients who acquired HIV-1 infection (cases) (90 isolates, 164 titers). PT₈₀ values are plotted against experimental ID₈₀ for each sample and each isolate (Lin’s concordance correlation coefficient³³ = 0.90 (95% CI 0.56–0.98)). PT₈₀ was calculated as popPK model-predicted concentration divided by IC₈₀. Nine of 164 experimental ID₈₀ titers were below the limit of detection at PT₈₀ > 10 (range 10.6–25.1). One of 164 experimental ID₈₀ titers was at or above the limit of detection at PT₈₀ < 10 (8.7). Dashed horizontal and vertical lines at a PT₈₀ = 10 show the experimental ID₈₀ limit of detection; concordance of predicted versus experimental values above versus below 10 was 154/164 (94%). Sera with PT₈₀ < 1.0 were not experimentally tested, as this would have required concentration of sera.