P35.03
Background: CD4MCs inhibit the gp120-CD4 interaction and can also expose masked epitopes of neutralizing antibodies on the gp120 protein. In this study, we investigated the phenotypic change in the CD4MCs resistant isolates against CD4MCs, other entry inhibitors and anti-Env neutralizing monoclonal antibodies (nMAbs).
Methods: Resistant variants were induced by five CD4MCs using the primary KP-5P virus (subtype B, R5) in PM1 cells. We constructed infectious clones with CD4MC-resistant mutation following in vitro selection. The susceptibility of the infectious clones to the inhibitors was evaluated using TZM-bl cells. We also simulated the gp120 3D structures by MD simulation model.
Results: Resistance against CD4MCs was associated with V255M, T375N/I, or M426I substitutions. We examined susceptibilities of these mutated clones to the CD4MCs, maraviroc (MVC), an entry inhibitor IC9564, CD4bs nMAb 3D6, and CD4i nMAb 4E9C. V255M, T375I, and M426I were associated with high level of resistance to all CD4MCs tested, while there was no substantial difference between the wild type and the mutated clones in sensitivity of MVC and IC9564. The V255M and M426I clones became resistant to 4E9C, whereas the clone with T375I showed low sensitivity to both 3D6 and 4E9C. MD simulations of KP-5P gp120 in complex with NBD-556 showed that (i) V255M mutation abolished the interaction of NBD-556 and gp120, and (ii) M426I mutation disconnected a hydrogen bond between Lys130 and Glu429, thus the NBD-556 binding site shifted different from the usual.
Conclusions: These data may give important knowledge for combination of NBD and other entry inhibitors or nMAbs.
