HIV cell fusion assay: phenotypic screening tool for the identification of HIV entry inhibitors via CXCR4.

The health and disease-related biology of the CXCR4 chemokine receptor presents the challenge of finding a small molecule that can bind CXCR4 and block T-cell tropic human immunodeficiency virus type 1 (HIV-1) cell entry, while preserving the ability of CXCR4 to respond to its native ligand, CXCL12. HIV entry into the host cell involves the interaction of the viral envelope glycoprotein gp120 binding to CD4, followed by a rearrangement in gp120, and subsequent interaction with the chemokine receptor CXCR4 or CCR5. These initial events can be re-created in a cell fusion assay that represents a surrogate system, mimicking the early stages of viral entry via these host cell receptors.

Analysis of boceprevir resistance associated amino acid variants (RAVs) in two phase 3 boceprevir clinical studies.

Background: We investigated the frequency of RAVs among patients failing to achieve SVR in two clinical trials. We also investigated the impact of interferon responsiveness on RAVs and specific baseline RAVs relationship with boceprevir treatment failure.

Methods: Data are from 1020 patients enrolled into either SPRINT-2 or RESPOND-2; patients received a 4-week PR lead-in prior to receiving boceprevir or placebo.

Resistance-associated amino acid variants associated with boceprevir plus pegylated interferon-α2b and ribavirin in patients with chronic hepatitis C in the SPRINT-1 trial.

Background: Resistance to direct-acting antivirals represents a new challenge in the treatment of chronic hepatitis C.

Methods: SPRINT-1 was a randomized study of treatment-naive patients with genotype (G) 1 hepatitis C infection (n=595) that evaluated the safety and efficacy of boceprevir (BOC) when added to pegylated interferon-α2b plus ribavirin (PR). Plasma samples collected at protocol-specified visits were analysed by population sequencing for detection of BOC-associated resistance-associated variants (RAVs).

Clinical resistance to vicriviroc through adaptive V3 loop mutations in HIV-1 subtype D gp120 that alter interactions with the N-terminus and ECL2 of CCR5.

The HIV-1 CCR5 co-receptor is a member of the chemokine receptor family of G-protein coupled receptors; for which a number of small molecule antagonists, such as vicriviroc (VCV), have been developed to inhibit HIV-1 R5-tropic replication. In this study, we analyzed an HIV-1 subtype D envelope gene from a clinical trial subject who developed complete resistance to VCV. The HIV-1 resistant envelope has six predominant amino acid changes in the V3 loop, together with one change in the C4 domain of gp120, which are fully responsible for the resistance phenotype.

Quantifying the relationship between HIV-1 susceptibility to CCR5 antagonists and virus affinity for antagonist-occupied co-receptor.

Previous studies have demonstrated that HIV-1 develops resistance to CCR5 antagonists by gaining the ability to use drug-occupied co-receptor. However, the effects of CCR5 antagonists on the affinity of virus-co-receptor interactions have been difficult to quantify. We developed a pharmacological model for allosteric interaction at G-protein coupled receptors to analyze the effect of different CCR5 antagonists on infection by three laboratory adapted viruses with low, moderate and high susceptibility to the inhibitors.

Structure-function analysis of human immunodeficiency virus type 1 gp120 amino acid mutations associated with resistance to the CCR5 coreceptor antagonist vicriviroc.

Vicriviroc (VCV) is a small-molecule CCR5 coreceptor antagonist currently in clinical trials for treatment of R5-tropic human immunodeficiency virus type 1 (HIV-1) infection. With this drug in development, identification of resistance mechanisms to VCV is needed to allow optimal outcomes in clinical practice. In this study we further characterized VCV resistance in a lab-adapted, VCV-resistant RU570 virus (RU570-VCV(res)).

Screening for antiviral inhibitors of the HIV integrase-LEDGF/p75 interaction using the AlphaScreen luminescent proximity assay.

Small-molecule inhibitors of HIV integrase (HIV IN) have emerged as a promising new class of antivirals for the treatment of HIV/AIDS. The compounds currently approved or in clinical development specifically target HIV DNA integration and were identified using strand-transfer assays targeting the HIV IN/viral DNA complex. The authors have developed a second biochemical assay for identification of HIV integrase inhibitors, targeting the interaction between HIV IN and the cellular cofactor LEDGF/p75.

Mapping resistance to the CCR5 co-receptor antagonist vicriviroc using heterologous chimeric HIV-1 envelope genes reveals key determinants in the C2-V5 domain of gp120.

Several small molecule drugs that bind to the host CCR5 co-receptor and prevent viral entry have been developed for the treatment of HIV-1 infection. The innate variability found in HIV-1 envelope and the complex viral/cellular interactions during entry makes defining resistance to these inhibitors challenging. Here we found that mapping determinants in the gp160 gene from a primary isolate RU570-VCV(res), selected in culture for resistance to the CCR5 entry inhibitor vicriviroc, was complicated by inactivity of the cloned envelope gene in pseudovirus assays.