For 185F, the median Nab IC50 titer for the 0-month Envs was significantly greater than the contemporaneous Envs at every time point using a Mann-whitney test (Fig. 1A) . Using the criteria of at least a 100-fold decrease in sensitivity to neutralization compared to the median of the 0-month Envs, a resistant Env (highlighted in green) from each time point was selected for in-depth investigations into Nab escape. At 28-months, three different Nab resistant Envs were selected because the phylogenetic tree indicated that multiple lineages of resistance were circulating at this time point (Fig. S1A ). For 205F, the difference between 0-month and contemporaneous Envs reached significance at only two of the five time points, although there were Envs at each time point for which Nab activity was undetectable at the highest dilution of plasma tested (1:20, Fig. 1B ). These Envs, which were often 1000fold less sensitive to Nab than the median of the 0-month Envs, were selected for detailed studies of Nab escape. Two genetically diverse Envs from distinct lineages were also selected to represent the 20-month time point in 205F (Fig. S1B ).