A monoclonal antibody to the gp120-CD4 complex has differential effects on HIV-induced syncytium formation and viral infectivity

Konopka, Krystyna; Pretzer, Elizabeth; Celada, Franco; Düzgüneş, Nejat

doi:10.1099/0022-1317-76-3-669

Cited by 15 publications

(13 citation statements)

References 42 publications

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“…These results confirmed that treatment of THP-1 cells with differentiating agents induced changes in cell-cell fusion that parallel changes in susceptibility to infection with the HIV-1 IIIB isolate. Consistent with our earlier report, 40 we found that significant differences existed among various uninfected cells in supporting cell-cell fusion. For example, HIV-1 IIIB -induced syncytium formation with H9 cells that tested highly positive (, 87%; MFI 5 3.1) for CD4, but expressed relatively low levels (18%; MFI 5 0.9) of CXCR4, was considerably greater than that observed with THP-1 cells expressing high CD4 and CXCR4 (Table 3).…”

Section: Hiv-1-induced Syncytium Formationsupporting

confidence: 94%

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Expression of CD4 Controls the Susceptibility of THP-1 Cells to Infection by R5 and X4 HIV Type 1 Isolates

Konopka

Düzgüneş

2002

AIDS Research and Human Retroviruses

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The monocytic THP-1 cell line has been used to study HIV-monocyte/macrophage interactions and the relationship between differentiation, virus production, and virus latency. Undifferentiated THP-1 cells are susceptible to infection by T-tropic human immunodeficiency virus type 1 (HIV-1) isolates that use the coreceptor CXCR4 (X4 strains). Treatment with phorbol 12-myristate 13-acetate (PMA) induces differentiation of THP-1 cells into adherent macrophage-like cells, which are susceptible to M-tropic, CCR5-dependent isolates (R5 strains). The aim of this study was to determine whether variabilities observed in the susceptibility of THP-1 cells to HIV-1 infection may be related to the differential expression of CD4, CCR5, and CXCR4. Both propagation and PMA treatment of THP-1 cells resulted in a marked decrease in CD4-positive cells, whereas the expression of CCR5 and CXCR4 was not reduced during propagation. Both coreceptors were also relatively "resistant" to PMA-induced downregulation when compared with the low percentage of CD4-positive cells in differentiated cultures. In undifferentiated THP-1 cells, low CD4 expression significantly reduced the susceptibility of the cells to infection with the R5 HIV-1(BaL) isolate, whereas a PMA-induced decrease in CD4 expression reduced permissiveness of the cells to the X4 HIV-1(IIIB) isolate. Thus, cell surface CD4 plays a primary role in determining how efficiently THP-1 cells can be infected with the X4 and the R5 isolates.

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Section: Hiv-1-induced Syncytium Formationsupporting

confidence: 94%

“…39,40 After 16-20 hr of cocultivation, syncytium formation was evaluated by inverted phase-contrast microscopy at 325 magnification. Extensive cell fusion was assigned a score of 31.…”

Section: Assay For Cd4-dependent Hiv-1-induced Cell Fusionmentioning

confidence: 99%

Expression of CD4 Controls the Susceptibility of THP-1 Cells to Infection by R5 and X4 HIV Type 1 Isolates

Konopka

Düzgüneş

2002

AIDS Research and Human Retroviruses

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“…Nevertheless, Mab F-91-55 inhibited both the infectivity of HIV-1 in H9 cells, and syncytium formation between these cells and chronically infected H9 cells. We proposed earlier that cellular systems used for syncytium assays differ in their susceptibility to antibodies, and that the interaction of gp120/gp41 with cell membrane CD4 may be different in cell-cell and virus-cell membrane fusion [29]. This difference may also explain our current results.…”

Section: Discussionsupporting

confidence: 54%

“…We showed previously that a monoclonal antibody to the gp120-CD4 complex (Mab F-91-55) that bound the D1/D2 domains of CD4 inhibited syncytium formation between chronically HIV-1-infected H9 cells and either A3.01 or Sup-T1 cells, even at a concentration of 0.1 µg/ml [29]. However, the antibody had a very limited effect on HIV-1 infection of A3.01 or Sup-T1 cells.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of HIV-1 Env-Mediated Cell-Cell Fusion by Lectins, Peptide T-20, and Neutralizing Antibodies

Yee

Konopka²,

Balzarini³

et al. 2011

TOVJ

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Background:Broadly cross-reactive, neutralizing human monoclonal antibodies, including 2F5, 2G12, 4E10 and IgG1 b12, can inhibit HIV-1 infection in vitro at very low concentrations. We examined the ability of these antibodies to inhibit cell-cell fusion between Clone69TRevEnv cells induced to express the viral envelope proteins, gp120/gp41 (Env), and highly CD4-positive SupT1 cells. The cells were loaded with green and red-orange cytoplasmic fluorophores, and fusion was monitored by fluorescence microscopy.Results:Cell-cell fusion was inhibited completely by the carbohydrate binding proteins (CBPs), Hippeastrum hybrid (Amaryllis) agglutinin (HHA), and Galanthus nivalis (Snowdrop) agglutinin (GNA), and by the peptide, T-20, at relatively low concentrations. Anti-gp120 and anti-gp41 antibodies, at concentrations much higher than those required for neutralization, were not particularly effective in inhibiting fusion. Monoclonal antibodies b12, m14 IgG and 2G12 had moderate inhibitory activity; the IC50 of 2G12 was about 80 µg/ml. Antibodies 4E10 and 2F5 had no inhibitory activity at the concentrations tested.Conclusions:These observations raise concerns about the ability of neutralizing antibodies to inhibit the spread of viral genetic material from infected cells to uninfected cells via cell-cell fusion. The interaction of gp120/gp41 with cell membrane CD4 may be different in cell-cell and virus-cell membrane fusion reactions, and may explain the differential effects of antibodies in these two systems. The fluorescence assay described here may be useful in high throughput screening of potential HIV fusion inhibitors.

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“…In fact, researchers had found evidence to suggest this in previous studies. For instance Konopka, et al ., found that there was a difference in monoclonal antibody binding between cell-cell fusion and virus-cell membrane fusion with murine monoclonal antibody (MAb F-91-55) raised against the complex of CD4 and gp120 (23). In another study, additional monoclonal antibodies were found to be relatively ineffective at inhibiting cell-cell fusion as well (24).…”

mentioning

confidence: 99%

Significant Differences in Cell–Cell Fusion and Viral Entry between Strains Revealed by Scanning Mutagenesis of the C-Heptad Repeat of HIV gp41

Diaz-Aguilar

DeWispelaere

et al. 2013

Biochemistry

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The transmembrane subunit, gp41, of HIV envelope mediates the viral fusion step of entry into the host cell. The protein consists of an extracellular domain, a transmembrane domain, and a cytoplasmic tail. The extracellular domain contains a fusion peptide, an N-terminal heptad repeat (NHR), a loop region, a C-terminal heptad repeat (CHR), and a membrane-proximal external region (MPER). For this study we examined each amino acid in the CHR (623-659), by alanine scanning mutagenesis in two HIV strains; one CCR5-utilizing (strain JRFL) and one CXCR4-utilizing (strain HXB2). We studied the functional importance of each amino acid residue by measuring mutational effects in both cell-cell fusion and viral entry and assessing envelope expression and gp120/gp41 proteolytic processing. The transmembrane subunit of HIV envelope, gp41, is very sensitive to subtle changes, like alanine substitution, which severely affect envelope function at multiple sites. Two important general findings are apparent when the entire data set from this study is taken into account: 1) strain HXB2 is much more stable to mutagenesis than is strain JRFL and 2) viral entry is much more stable to mutagenesis than is cell-cell fusion. These findings strengthen our notion that gp41 is a vulnerable target for therapeutic and prophylactic intervention. Further structural studies to gain a full understanding of the intermediate states that drive HIV membrane fusion are imperative.

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A monoclonal antibody to the gp120-CD4 complex has differential effects on HIV-induced syncytium formation and viral infectivity

Cited by 15 publications

References 42 publications

Expression of CD4 Controls the Susceptibility of THP-1 Cells to Infection by R5 and X4 HIV Type 1 Isolates

Expression of CD4 Controls the Susceptibility of THP-1 Cells to Infection by R5 and X4 HIV Type 1 Isolates

Inhibition of HIV-1 Env-Mediated Cell-Cell Fusion by Lectins, Peptide T-20, and Neutralizing Antibodies

Significant Differences in Cell–Cell Fusion and Viral Entry between Strains Revealed by Scanning Mutagenesis of the C-Heptad Repeat of HIV gp41

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