title: Alternative coreceptor requirements for efficient CCR5- and CXCR4-mediated HIV-1 entry into macrophages.
abstract: Macrophage tropism of human immunodeficiency virus type 1 (HIV-1) is distinct from coreceptor specificity of the viral envelope glycoproteins (Env), but the virus-cell interactions that contribute to efficient HIV-1 entry into macrophages, particularly via CXCR4, are not well understood. Here, we characterized a panel of HIV-1 Envs that use CCR5 (n = 14) or CXCR4 (n = 6) to enter monocyte-derived macrophages (MDM) with various degrees of efficiency. Our results show that efficient CCR5-mediated MDM entry by Env-pseudotyped reporter viruses is associated with increased tolerance of several mutations within the CCR5 N terminus. In contrast, efficient CXCR4-mediated MDM entry was associated with reduced tolerance of a large deletion within the CXCR4 N terminus. Env sequence analysis and structural modeling identified amino acid variants at positions 261 and 263 within the gp41-interactive region of gp120 and a variant at position 326 within the gp120 V3 loop that were associated with efficient CXCR4-mediated MDM entry. Mutagenesis studies showed that the gp41 interaction domain variants exert a significant but strain-specific influence on CXCR4-mediated MDM entry, suggesting that the structural integrity of the gp120-gp41 interface is important for efficient CXCR4-mediated MDM entry of certain HIV-1 strains. However, the presence of Ile326 in the gp120 V3 loop stem, which we show by molecular modeling is located at the gp120-coreceptor interface and predicted to interact with the CXCR4 N terminus, was found to be critical for efficient CXCR4-mediated MDM entry of divergent CXCR4-using Envs. Together, the results of our study provide novel insights into alternative mechanisms of Env-coreceptor engagement that are associated with efficient CCR5- and CXCR4-mediated HIV-1 entry into macrophages.
authors.affiliation: Center for Virology, Burnet Institute, Melbourne, Victoria, Australia.
authors.forename: Kieran
authors.initials: K
authors.lastname: Cashin
authors.forename: Michael
authors.initials: M
authors.lastname: Roche
authors.forename: Jasminka
authors.initials: J
authors.lastname: Sterjovski
authors.forename: Anne
authors.initials: A
authors.lastname: Ellett
authors.forename: Lachlan R
authors.initials: LR
authors.lastname: Gray
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Cunningham
authors.forename: Paul A
authors.initials: PA
authors.lastname: Ramsland
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Churchill
authors.forename: Paul R
authors.initials: PR
authors.lastname: Gorry
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D008264:Macrophages / Q000821:virology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D019713:Receptors, CCR5 / Q000235:genetics / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000235:genetics / Q000378:metabolism*; D015728:Receptors, HIV / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: C527276:CXCR4 protein, human; D015699:HIV Envelope Protein gp120; D050505:Mutant Proteins; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; D015728:Receptors, HIV; C514793:gp120 protein, Human immunodeficiency virus 1