Two HIV-1 Variants Resistant to Small Molecule CCR5 Inhibitors Differ in How They Use CCR5 for Entry

Reem Berro,John P Moore,Per J Klasse,Min Lu,Rogier W Sanders,Michael Farzan

doi:10.1371/journal.ppat.1000548

Abstract

HIV-1 variants resistant to small molecule CCR5 inhibitors recognize the inhibitor-CCR5 complex, while also interacting with free CCR5. The most common genetic route to resistance involves sequence changes in the gp120 V3 region, a pathway followed when the primary isolate CC1/85 was cultured with the AD101 inhibitor in vitro, creating the CC101.19 resistant variant. However, the D1/86.16 escape mutant contains no V3 changes but has three substitutions in the gp41 fusion peptide. By using CCR5 point-mutants and gp120-targeting agents, we have investigated how infectious clonal viruses derived from the parental and both resistant isolates interact with CCR5. We conclude that the V3 sequence changes in CC101.19 cl.7 create a virus with an increased dependency on interactions with the CCR5 N-terminus. Elements of the CCR5 binding site associated with the V3 region and the CD4-induced (CD4i) epitope cluster in the gp120 bridging sheet are more exposed on the native Env complex of CC101.19 cl.7, which is sensitive to neutralization via these epitopes. However, D1/86.16 cl.23 does not have an increased dependency on the CCR5 N-terminus, and its CCR5 binding site has not become more exposed. How this virus interacts with the inhibitor-CCR5 complex remains to be understood.

Highlights

Small molecule drugs or drug candidates bind to the cell surface CCR5 protein and prevent human immunodeficiency virus type 1 (HIV-1) from using it as a coreceptor for entry into CD4-positive target cells [1,2]
We have recently shown that this alternative pathway involves three sequence changes in the fusion peptide (FP) region of the gp41 transmembrane glycoprotein
HIV-1 entry into target cells is triggered by the interaction of the viral envelope glycoproteins with a cell-surface receptor (CD4) and a coreceptor (CCR5), and culminates in fusion of the viral and cell membranes

Summary

Introduction

Small molecule drugs or drug candidates bind to the cell surface CCR5 protein and prevent human immunodeficiency virus type 1 (HIV-1) from using it as a coreceptor for entry into CD4-positive target cells [1,2] These compounds, which include the licensed drug maraviroc (MVC) and the clinical candidate vicriviroc (VVC, known as SCH-D), bind within the transmembrane helices of CCR5 and stabilize the protein in a conformation that cannot be recognized efficiently by the HIV-1 gp120 surface glycoprotein [3,4,5,6,7]. We have recently shown that this alternative pathway involves three sequence changes in the fusion peptide (FP) region of the gp transmembrane glycoprotein These changes exert broadly similar effects to the more conventional V3 changes, in that the resistant virus was able to use the inhibitor-CCR5 complex for entry [22]

Methods

Discussion

Conclusion