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Inhibition of virus attachment to CD4+ target cells is a major mechanism of T cell line-adapted HIV-1 neutralization.

Ugolini S, Mondor I, Parren PW, Burton DR, Tilley SA, Klasse PJ, Sattentau QJ - J. Exp. Med. (1997)

Bottom Line: Here we show, by the use of a novel virus-cell binding assay, that soluble CD4 and monoclonal antibodies to all confirmed glycoprotein (gp)120 neutralizing epitopes, including the CD4 binding site and the V2 and V3 loops, inhibit the adsorption of two T cell line-adapted HIV-1 viruses to CD4+ cells.By contrast, antibodies specific for regions of gp120 other than the CD4 binding site showed little or no inhibition of either soluble gp120 binding to CD4+ cells or soluble CD4 binding to HIV-infected cells, implying that this effect is specific to the virion-cell interaction.However, inhibition of HIV-1 attachment to cells is not a universal mechanism of neutralization, since an anti-gp41 antibody did not inhibit virus-cell binding at neutralizing concentrations, implying activity after virus-cell binding.

View Article: PubMed Central - PubMed

Affiliation: Centre d'Immunologie de Marseille-Luminy, France.

ABSTRACT
Antibody-mediated neutralization of human immunodeficiency virus type-1 (HIV-1) is thought to function by at least two distinct mechanisms: inhibition of virus-receptor binding, and interference with events after binding, such as virus-cell membrane fusion. Here we show, by the use of a novel virus-cell binding assay, that soluble CD4 and monoclonal antibodies to all confirmed glycoprotein (gp)120 neutralizing epitopes, including the CD4 binding site and the V2 and V3 loops, inhibit the adsorption of two T cell line-adapted HIV-1 viruses to CD4+ cells. A correlation between the inhibition of virus binding and virus neutralization was observed for soluble CD4 and all anti-gp120 antibodies, indicating that this is a major mechanism of HIV neutralization. By contrast, antibodies specific for regions of gp120 other than the CD4 binding site showed little or no inhibition of either soluble gp120 binding to CD4+ cells or soluble CD4 binding to HIV-infected cells, implying that this effect is specific to the virion-cell interaction. However, inhibition of HIV-1 attachment to cells is not a universal mechanism of neutralization, since an anti-gp41 antibody did not inhibit virus-cell binding at neutralizing concentrations, implying activity after virus-cell binding.

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Inhibition of HIV-1 binding and infectivity by mAbs to  other, non-CD4bs epitopes. The following antibodies were tested for  their ability to inhibit infectivity and cell binding of Hx10 virus; (A) 48d,  (B) 2G12, (C) anti-gp41 2F5, (D) C108G or MN virus, (E) 48d, and (F)  2F5. The experiment was carried out as described in Fig. 3, and results are  represented as percentage of binding versus reduction in infectivity.
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Figure 6: Inhibition of HIV-1 binding and infectivity by mAbs to other, non-CD4bs epitopes. The following antibodies were tested for their ability to inhibit infectivity and cell binding of Hx10 virus; (A) 48d, (B) 2G12, (C) anti-gp41 2F5, (D) C108G or MN virus, (E) 48d, and (F) 2F5. The experiment was carried out as described in Fig. 3, and results are represented as percentage of binding versus reduction in infectivity.

Mentions: Inhibition of HIV-1–cell binding by CD4bs-specific mAbs was anticipated, since it has previously been shown that such antibodies are efficient inhibitors of sgp120 binding to sCD4 and CD4+ cells. We next tested neutralizing mAbs specific for other gp120 epitopes for their ability to interfere with virus–cell binding. Several other confirmed TCLA virus neutralization epitopes have been identified: the hypervariable V2 and V3 loops, the CD4-induced (CD4i) epitopes recognized by mAbs 48d and 17b, and the unique 2G12 epitope. Fig. 5 shows the effect of V3 loop–specific mAbs on virion binding. Unexpectedly, these mAbs interfered with both Hx10– and MN–cell binding; maximum inhibition of virion attachment at 200 nM by 110.5, ICR41, and 447-52D was ∼46, 47, and 85%, respectively, with Hx10. The effect of V3 loops on MN–cell binding was more pronounced than on Hx10; 447D, Loop 2, and the Fab fragment of Loop 2 inhibited MN–cell binding maximally at 200 nM by 96, 65, and 56%, respectively. Similarly, C108G, 48d, and 2G12 at the same concentration inhibited Hx10 binding by 83, 81, and 76%, respectively, and 48d reduced MN attachment by 79% (Fig. 6). Thus, all anti-gp120 neutralizing mAbs tested were able to interfere with the binding of two TCLA viruses to a CD4+ T cell line. To determine whether the inhibition of virus-cell binding was general to all anti–envelope glycoprotein mAbs, we carried out binding and neutralization analyses with the neutralizing anti-gp41 mAb 2F5. By contrast with the results obtained with the anti-gp120 mAbs, 2F5 did not inhibit HIV–cell binding at any concentration tested, but potently interfered with HIV infection; at a concentration of 200 nM, 2F5 reduced Hx10 and MN infectivity by ∼80- and 30-fold, respectively (Fig. 6).


Inhibition of virus attachment to CD4+ target cells is a major mechanism of T cell line-adapted HIV-1 neutralization.

Ugolini S, Mondor I, Parren PW, Burton DR, Tilley SA, Klasse PJ, Sattentau QJ - J. Exp. Med. (1997)

Inhibition of HIV-1 binding and infectivity by mAbs to  other, non-CD4bs epitopes. The following antibodies were tested for  their ability to inhibit infectivity and cell binding of Hx10 virus; (A) 48d,  (B) 2G12, (C) anti-gp41 2F5, (D) C108G or MN virus, (E) 48d, and (F)  2F5. The experiment was carried out as described in Fig. 3, and results are  represented as percentage of binding versus reduction in infectivity.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199094&req=5

Figure 6: Inhibition of HIV-1 binding and infectivity by mAbs to other, non-CD4bs epitopes. The following antibodies were tested for their ability to inhibit infectivity and cell binding of Hx10 virus; (A) 48d, (B) 2G12, (C) anti-gp41 2F5, (D) C108G or MN virus, (E) 48d, and (F) 2F5. The experiment was carried out as described in Fig. 3, and results are represented as percentage of binding versus reduction in infectivity.
Mentions: Inhibition of HIV-1–cell binding by CD4bs-specific mAbs was anticipated, since it has previously been shown that such antibodies are efficient inhibitors of sgp120 binding to sCD4 and CD4+ cells. We next tested neutralizing mAbs specific for other gp120 epitopes for their ability to interfere with virus–cell binding. Several other confirmed TCLA virus neutralization epitopes have been identified: the hypervariable V2 and V3 loops, the CD4-induced (CD4i) epitopes recognized by mAbs 48d and 17b, and the unique 2G12 epitope. Fig. 5 shows the effect of V3 loop–specific mAbs on virion binding. Unexpectedly, these mAbs interfered with both Hx10– and MN–cell binding; maximum inhibition of virion attachment at 200 nM by 110.5, ICR41, and 447-52D was ∼46, 47, and 85%, respectively, with Hx10. The effect of V3 loops on MN–cell binding was more pronounced than on Hx10; 447D, Loop 2, and the Fab fragment of Loop 2 inhibited MN–cell binding maximally at 200 nM by 96, 65, and 56%, respectively. Similarly, C108G, 48d, and 2G12 at the same concentration inhibited Hx10 binding by 83, 81, and 76%, respectively, and 48d reduced MN attachment by 79% (Fig. 6). Thus, all anti-gp120 neutralizing mAbs tested were able to interfere with the binding of two TCLA viruses to a CD4+ T cell line. To determine whether the inhibition of virus-cell binding was general to all anti–envelope glycoprotein mAbs, we carried out binding and neutralization analyses with the neutralizing anti-gp41 mAb 2F5. By contrast with the results obtained with the anti-gp120 mAbs, 2F5 did not inhibit HIV–cell binding at any concentration tested, but potently interfered with HIV infection; at a concentration of 200 nM, 2F5 reduced Hx10 and MN infectivity by ∼80- and 30-fold, respectively (Fig. 6).

Bottom Line: Here we show, by the use of a novel virus-cell binding assay, that soluble CD4 and monoclonal antibodies to all confirmed glycoprotein (gp)120 neutralizing epitopes, including the CD4 binding site and the V2 and V3 loops, inhibit the adsorption of two T cell line-adapted HIV-1 viruses to CD4+ cells.By contrast, antibodies specific for regions of gp120 other than the CD4 binding site showed little or no inhibition of either soluble gp120 binding to CD4+ cells or soluble CD4 binding to HIV-infected cells, implying that this effect is specific to the virion-cell interaction.However, inhibition of HIV-1 attachment to cells is not a universal mechanism of neutralization, since an anti-gp41 antibody did not inhibit virus-cell binding at neutralizing concentrations, implying activity after virus-cell binding.

View Article: PubMed Central - PubMed

Affiliation: Centre d'Immunologie de Marseille-Luminy, France.

ABSTRACT
Antibody-mediated neutralization of human immunodeficiency virus type-1 (HIV-1) is thought to function by at least two distinct mechanisms: inhibition of virus-receptor binding, and interference with events after binding, such as virus-cell membrane fusion. Here we show, by the use of a novel virus-cell binding assay, that soluble CD4 and monoclonal antibodies to all confirmed glycoprotein (gp)120 neutralizing epitopes, including the CD4 binding site and the V2 and V3 loops, inhibit the adsorption of two T cell line-adapted HIV-1 viruses to CD4+ cells. A correlation between the inhibition of virus binding and virus neutralization was observed for soluble CD4 and all anti-gp120 antibodies, indicating that this is a major mechanism of HIV neutralization. By contrast, antibodies specific for regions of gp120 other than the CD4 binding site showed little or no inhibition of either soluble gp120 binding to CD4+ cells or soluble CD4 binding to HIV-infected cells, implying that this effect is specific to the virion-cell interaction. However, inhibition of HIV-1 attachment to cells is not a universal mechanism of neutralization, since an anti-gp41 antibody did not inhibit virus-cell binding at neutralizing concentrations, implying activity after virus-cell binding.

Show MeSH
Related in: MedlinePlus