title: Sensitivity of HIV-1 to entry inhibitors correlates with envelope/coreceptor affinity, receptor density, and fusion kinetics.
abstract: HIV entry inhibitors include coreceptor antagonists and the fusion inhibitor T-20. T-20 binds the first helical region (HR1) in the gp41 subunit of the viral envelope (Env) protein and prevents conformational changes required for membrane fusion. HR1 appears to become accessible to T-20 after Env binds CD4, whereas coreceptor binding is thought to induce the final conformational changes that lead to membrane fusion. Thus, T-20 binds to a structural intermediate of the fusion process. Primary viruses exhibit considerable variability in T-20 sensitivity, and determinants outside of HR1 can affect sensitivity by unknown mechanisms. We studied chimeric Env proteins containing different V3 loop sequences and found that gp120coreceptor affinity correlated with T-20 and coreceptor antagonist sensitivity, with greater affinity resulting in increased resistance to both classes of entry inhibitors. Enhanced affinity resulted in more rapid fusion kinetics, reducing the time during which Env is sensitive to T-20. Reduced coreceptor expression levels also delayed fusion kinetics and enhanced virus sensitivity to T-20, whereas increased coreceptor levels had the opposite effect. A single amino acid change (K421D) in the bridging sheet region of the primary virus strain YU2 reduced affinity for CCR5 and increased T-20 sensitivity by about 30-fold. Thus, mutations in Env that affect receptor engagement and membrane fusion rates can alter entry inhibitor sensitivity. Because coreceptor expression levels are typically limiting in vivo, individuals who express lower coreceptor levels may respond more favorably to entry inhibitors such as T-20, whose effectiveness we show depends in part on fusion kinetics.
authors.affiliation: Department of Microbiology, University of Pennsylvania, 225 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, USA. jreeves@mail.med.upenn.edu
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Reeves
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Gallo
authors.forename: Navid
authors.initials: N
authors.lastname: Ahmad
authors.forename: John L
authors.initials: JL
authors.lastname: Miamidian
authors.forename: Phoebe E
authors.initials: PE
authors.lastname: Harvey
authors.forename: Matthew
authors.initials: M
authors.lastname: Sharron
authors.forename: Stefan
authors.initials: S
authors.lastname: Pohlmann
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Sfakianos
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Derdeyn
authors.forename: Robert
authors.initials: R
authors.lastname: Blumenthal
authors.forename: Eric
authors.initials: E
authors.lastname: Hunter
authors.forename: Robert W
authors.initials: RW
authors.lastname: Doms
mesh_terms: D016475:3T3 Cells; D000577:Amides / Q000494:pharmacology*; D019943:Amino Acid Substitution; D000818:Animals; D019380:Anti-HIV Agents / Q000494:pharmacology*; D065100:CCR5 Receptor Antagonists; D015704:CD4 Antigens / Q000378:metabolism; D024882:Drug Resistance, Viral; D000077560:Enfuvirtide; D015752:Genes, env; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008561:Membrane Fusion / Q000187:drug effects / Q000235:genetics; D051379:Mice; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D019713:Receptors, CCR5 / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000577:Amides; D019380:Anti-HIV Agents; D065100:CCR5 Receptor Antagonists; D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments; D000644:Quaternary Ammonium Compounds; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; D011993:Recombinant Fusion Proteins; D000077560:Enfuvirtide; C119369:TAK 779