Complex Determinants in Human Immunodeficiency Virus Type 1 Envelope gp120 Mediate CXCR4-Dependent Infection of Macrophages

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.The gp120 glycoproteins of the human immunodeficiency virus type 1 (HIV-1) envelope (Env) initiate contact between the virus and the target cell (46). Viral attachment involves binding of gp120 to cellular CD4 and then to either CCR5 or CXCR4 as a coreceptor (reviewed in references 13 and 14). CD4 binding occurs with high affinity and triggers a conformational change in gp120 that exposes the coreceptor binding site. Current models of gp120 binding to coreceptor, supported recently by analysis of the crystal structure of CXCR4 (79), suggest that the crown of the V3 loop interacts principally with the coreceptor second extracellular loop (ECL2) region while the gp120 bridging sheet and the stem of the V3 loop interact with the coreceptor N terminus (7, 11,25,39). The interaction of CD4-bound gp120 with coreceptor induces additional conformational changes in gp120, which leads to a structural rearrangement in gp41 that enables fusion and virus entry (reviewed in reference 75).

Section: Fig 4 Env Sequence Alterations Associated With Efficient Csupporting

confidence: 82%

mentioning

confidence: 99%

Alternative Coreceptor Requirements for Efficient CCR5- and CXCR4-Mediated HIV-1 Entry into Macrophages

Cashin

Roche

Sterjovski

et al. 2011

“…2A). Consistent with previous studies, ADA and 89.6 Envs entered PBMC and MDM, whereas HXB2 Env entered PBMC but not MDM (18,19,34,42,43,(49)(50)(51). All C2 and DR Envs entered PBMC, but only C2-16 and DR-17 Envs entered MDM.…”

Section: Vol 80 2006supporting

confidence: 77%

Genetic and Functional Analysis of R5X4 Human Immunodeficiency Virus Type 1 Envelope Glycoproteins Derived from Two Individuals Homozygous for the CCR5Δ32 Allele

Gray

Churchill

Keane

et al. 2006

We characterized human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins (Env) isolated from two HIV-1-infected CCR5⌬32 homozygotes. Envs from both subjects used CCR5 and CXCR4 for entry into transfected cells. Most R5X4 Envs were lymphocyte-tropic and used CXCR4 exclusively for entry into peripheral blood mononuclear cells (PBMC), but a subset was dually lymphocyte-and macrophage-tropic and used either CCR5 or CXCR4 for entry into PBMC and monocyte-derived macrophages. The persistence of CCR5-using HIV-1 in two CCR5⌬32 homozygotes suggests the conserved CCR5 binding domain of Env is highly stable and provides new mechanistic insights important for HIV-1 transmission and persistence.

“…While many HIV-1 strains can use either CCR5 or CXCR4 (R5X4 viruses) to infect cell lines, the efficiency with which a given virus uses each coreceptor for infection can vary widely and does not always predict the mechanism of entry into human T cells or macrophages (18). Thus, some R5X4 viruses use only CXCR4 to infect certain primary cells, others use only CCR5, and some viruses use both coreceptors to infect multiple cell types (16,17,26,36,(59)(60)(61). The use of specific and potent coreceptor antagonists can be utilized to prevent entry via one coreceptor, revealing the efficiency with which the alternative coreceptor can support virus infection.…”

mentioning

confidence: 99%

Baseline Resistance of Primary Human Immunodeficiency Virus Type 1 Strains to the CXCR4 Inhibitor AMD3100

Harrison

Lynch²,

Sierra³

et al. 2008

We screened a panel of R5X4 and X4 human immunodeficiency virus type 1 (HIV-1) strains for their sensitivities to AMD3100, a small-molecule CXCR4 antagonist that blocks HIV-1 infection via this coreceptor. While no longer under clinical development, AMD3100 is a useful tool with which to probe interactions between the viral envelope (Env) protein and CXCR4 and to identify pathways by which HIV-1 may become resistant to this class of antiviral agents. While infection by most virus strains was completely blocked by AMD3100, we identified several R5X4 and X4 isolates that exhibited plateau effects: as the AMD3100 concentration was increased, virus infection and membrane fusion diminished to variable degrees. Once saturating concentrations of AMD3100 were achieved, further inhibition was not observed, indicating a noncompetitive mode of viral resistance to the drug. The magnitude of the plateau varied depending on the virus isolate, as well as the cell type used, with considerable variation observed when primary human T cells from different human donors were used. Structure-function studies indicated that the V1/V2 region of the R5X4 HIV-1 isolate DH12 was necessary for AMD3100 resistance and could confer this property on two heterologous Env proteins. We conclude that some R5X4 and X4 HIV-1 isolates can utilize the AMD3100-bound conformation of CXCR4, with the efficiency being influenced by both viral and host factors. Baseline resistance to this CXCR4 antagonist could influence the clinical use of such compounds.