HIV Type 1 from a Patient with Baseline Resistance to CCR5 Antagonists Uses Drug-Bound Receptor for Entry

Abstract

CCR5 antagonists are a new class of antiretroviral drugs that block viral entry by disrupting interactions between the viral envelope (Env) glycoprotein and coreceptor. During the CCR100136 (EPIC) Phase IIb study of the CCR5 antagonist aplaviroc (APL) in treatment-naive individuals, a patient was identified who harbored virus strains that exhibited partial resistance to APL at the time of virologic failure. Retrospectively, it was found that APL resistance was present at baseline as well. To investigate the mechanism of APL resistance in this patient, we cloned HIV-1 env genes from plasma obtained at baseline and after virologic failure. Approximately 85% of cloned Envs were functional, and all exhibited partial resistance to APL. All Envs were R5-tropic, were partially resistant to other CCR5 antagonists including maraviroc on cells with high CCR5 expression, but remained sensitive to the fusion inhibitor enfuvirtide. Competition studies with natural CCR5 ligands revealed that the mechanism of drug resistance entailed the use of the drug-bound conformation of CCR5 by the Env proteins obtained from this individual. The degree of drug resistance varied between Env clones, and also varied depending on the cell line used or the donor from whom the primary T cells were obtained. Thus, both virus and host factors contribute to CCR5 antagonist resistance. This study shows that R5 HIV-1 strains resistant to CCR5 inhibitors can arise in patients, confirming a mechanism of resistance previously characterized in vitro. In addition, some patients can harbor CCR5 antagonist-resistant viruses prior to treatment, which may have implications for the clinical use of this new class of antiretrovirals.

HIV-1 Resistance to CCR5 Antagonists Associated with Highly Efficient Use of CCR5 and Altered Tropism on Primary CD4 + T Cells

“…We previously described Env proteins derived from a patient treated with the CCR5 antagonist aplaviroc that exhibited resistance to all CCR5 antagonists tested (48). This patient (P5) harbored resistant Envs both prior to and after treatment with aplaviroc, designated pre5 and post5 clones, respectively.…”

“…Previous experiments have demonstrated that the pre5.2 Env exclusively utilizes the CCR5 receptor for entry and does not infect primary CD4 ϩ T cells from ⌬32ccr5-homozygous patients (48). Consistent with a dependence on CCR5 for entry, treatment of cells with 62.5 M of the CXCR4 antagonist AMD3100 did not significantly de- a Pseudotyped viruses bearing the pre5.2 Env were used to infect 293 cells expressing CD4 and wild-type CCR5 or one of a panel of CCR5 mutants.…”

“…Thus, there is some variability in the relative importance of the CCR5 NЈ-terminal domain and ECL2 in supporting infection by different HIV-1 strains (41). This underlying plas- ticity can lead to rare, unexpected outcomes: we identified a patient whose virus exhibited baseline resistance to all CCR5 antagonists tested, which likely contributed to this individual's subsequent virologic failure on an antiviral regimen that included aplaviroc (21,48). This finding poses two central questions: by what mechanism(s) does resistance to CCR5 antagonists occur, and what are the implications of drug resistance for viral tropism?…”

“…We previously described a panel of Envs isolated from a patient (P5) that were resistant to complete inhibition by aplaviroc and other CCR5 antagonists (48). Two representative Envs from this panel, pre5.2 and post 5.1, were chosen for the present study.…”

“…Resistant viruses that utilize drug-bound CCR5 have been identified following in vitro passaging with multiple CCR5 antagonists (1,2,22,33,36,51,56). Recently, we identified a panel of viral Envs able to use aplaviroc (APL)-bound CCR5 that were isolated from a patient (21,48). The Envs from this patient were cross resistant to the CCR5 antagonists AD101, TAK779, SCH-C, and maraviroc.…”