To define the effects of these potential glycan addition sites in V1 and V2 on sensitivity to the two Mabs, both sites were introduced into 0-month EnvPL6.3, which carried neither (Fig. 6B) . For Mab 13.6A, introduction of the V1 predicted glycan site into 0-month EnvPL6.3 resulted in a dramatic increase in neutralization sensitivity (Fig. 6C ). In contrast, for 6.4C, introduction of the V1 predicted glycan produced a moderate decrease in sensitivity (Fig. 6D) . Introduction of the V2 predicted glycan site into EnvPL6.3, with or without the V1 predicted glycan site, resulted in strong protection against both Mabs (Fig. 6C and D). Thus, predicted glycosylation at this site in V2 potentially tracked with protection against both Mabs (for a summary of longitudinal Envs and glycan sites see Table 2 ). These results also demonstrate that while both Mabs target a V1V2-dependent epitope, they recognize distinct structures.