The CCR5 inhibitor maraviroc (MVC) exerts its antiviral activity by binding to- and altering the conformation of the CCR5 extracellular loops such that HIV-1 gp120 no longer recognizes CCR5. Viruses that have become resistant to MVC through long-term in vitro culture, or from treatment failure in vivo, can use the MVCbound form of CCR5 for HIV-1 entry via adaptive alterations in gp120. Partial baseline resistance to another CCR5 inhibitor through this mechanism, AD101, has been noted recently in one subject (1). Here, we identified and characterized envelope (Env) clones with baseline resistance to MVC that persisted (as a subset of the viral quasispecies) for approximately 12 months in an antiretroviral therapy-naïve subject infected with HIV-1 subtype C (C-HIV). From a large, longitudinal study of C-HIV Envs (n=323) cloned from 21 subjects experiencing progressive C-HIV infection (see related abstract by Jakobsen et al., “Preferential CCR5-usage by R5X4 subtype C HIV-1 imparts sensitivity to maraviroc and tempers disease progression”), nine subjects persistently harboured CCR5-using (R5) Envs to late stages of infection. Virus inhibition assays in NP2-CD4/CCR5 cells using Env-pseudotyped luciferase reporter viruses identified one subject (thus far) who harboured R5 Env variants in sequential plasma samples that were only partially inhibited by 10μM MVC (n=4 clones). The maximal percent inhibition (MPI) of these Envs by MVC ranged from 80 to 90% in NP2-CD4/CCR5 cells and PBMC. In contrast, sensitive Envs from the same subject were completely inhibited by MVC (MPI=100%). MPI’s by the resistant Envs steadily decreased when MVC inhibition assays were performed in cells expressing increasing levels of CCR5, indicating that the resistant Envs use the MVC-bound form of CCR5 for entry more efficiently when there is more MVC-CCR5 complex on the cell surface. Comparison of vector angles calculated by mathematical modelling of 293-Affinofile cell experiments between a representative resistant and sensitive Env revealed a highly efficient CCR5 interaction associated with baseline MVC resistance, which became much less efficient in the presence of MVC. Sequence analysis identified alterations within the V2, V3, C3, V4 and C4 regions of gp120 that were associated with baseline MVC resistance. These alterations predominantly involve a redistribution of charged amino acids or alteration of glycosylation patterns. Together, our study shows that some untreated subjects with C-HIV infection may harbour virus with baseline resistance to MVC, which may have implications for the clinical use of MVC. 1. Tilton et al., AIDS Research and Human Retroviruses, 26:13-24, 2010.
HIV; Resistance; Envelope; Maraviroc
Main Research Area:
Keystone Symposia - HIV Evolution, Genomics and Pathogenesis, 2011