Antibodies to several conformation-dependent epitopes of gp120/gp41 inhibit CCR-5-dependent cell-to-cell fusion mediated by the native envelope glycoprotein of a primary macrophage-tropic HIV-1 isolate.
The beta-chemokine receptor CCR-5 is essential for the efficient entry of primary macrophage-tropic HIV-1 isolates into CD4(+) target cells. To study CCR-5-dependent cell-to-cell fusion, we have developed an assay system based on the infection of CD4(+) CCR-5(+) HeLa cells with a Semliki Forest virus recombinant expressing the gp120/gp41 envelope (Env) from a primary clade B HIV-1 isolate (BX08), or from a laboratory T cell line-adapted strain (LAI). In this system, gp120/gp41 of the "nonsyncytium-inducing," primary, macrophage-tropic HIV-1BX08 isolate, was at least as fusogenic as that of the "syncytium-inducing" HIV-1LAI strain. BX08 Env-mediated fusion was inhibited by the beta-chemokines RANTES (regulated upon activation, normal T cell expressed and secreted) and macrophage inflammatory proteins 1beta (MIP-1beta) and by antibodies to CD4, whereas LAI Env-mediated fusion was insensitive to these beta-chemokines. In contrast soluble CD4 significantly reduced LAI, but not BX08 Env-mediated fusion, suggesting that the primary isolate Env glycoprotein has a reduced affinity for CD4. The domains in gp120/gp41 involved in the interaction with the CD4 and CCR-5 molecules were probed using monoclonal antibodies. For the antibodies tested here, the greatest inhibition of fusion was observed with those directed to conformation-dependent, rather than linear epitopes. Efficient inhibition of fusion was not restricted to epitopes in any one domain of gp120/gp41. The assay was sufficiently sensitive to distinguish between antibody- and beta-chemokine-mediated fusion inhibition using serum samples from patient BX08, suggesting that the system may be useful for screening human sera for the presence of biologically significant antibodies.
Verrier
F C
FC
Département de Virologie Moléculaire, Institut Pasteur, Paris, France.
Charneau
P
P
Altmeyer
R
R
Laurent
S
S
Borman
A M
AM
Girard
M
M
D000914:Antibodies, Viral / Q000276:immunology* / Q000494:pharmacology; D000918:Antibody Specificity; D002459:Cell Fusion / Q000187:drug effects / Q000276:immunology; D000939:Epitopes / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000276:immunology*; D015497:HIV-1; D006367:HeLa Cells; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000473:pathology / Q000821:virology*; D011487:Protein Conformation; D019713:Receptors, CCR5; D018121:Receptors, Cytokine / Q000276:immunology*; D015728:Receptors, HIV / Q000276:immunology*
D000914:Antibodies, Viral; D000939:Epitopes; D015699:HIV Envelope Protein gp120; D019713:Receptors, CCR5; D018121:Receptors, Cytokine; D015728:Receptors, HIV