Differential inhibition of human immunodeficiency virus type 1 fusion, gp120 binding, and CC-chemokine activity by monoclonal antibodies to CCR5.
The CC-chemokine receptor CCR5 mediates fusion and entry of the most commonly transmitted human immunodeficiency virus type 1 (HIV-1) strains. We have isolated six new anti-CCR5 murine monoclonal antibodies (MAbs), designated PA8, PA9, PA10, PA11, PA12, and PA14. A panel of CCR5 alanine point mutants was used to map the epitopes of these MAbs and the previously described MAb 2D7 to specific amino acid residues in the N terminus and/or second extracellular loop regions of CCR5. This structural information was correlated with the MAbs' abilities to inhibit (i) HIV-1 entry, (ii) HIV-1 envelope glycoprotein-mediated membrane fusion, (iii) gp120 binding to CCR5, and (iv) CC-chemokine activity. Surprisingly, there was no correlation between the ability of a MAb to inhibit HIV-1 fusion-entry and its ability to inhibit either the binding of a gp120-soluble CD4 complex to CCR5 or CC-chemokine activity. MAbs PA9 to PA12, whose epitopes include residues in the CCR5 N terminus, strongly inhibited gp120 binding but only moderately inhibited HIV-1 fusion and entry and had no effect on RANTES-induced calcium mobilization. MAbs PA14 and 2D7, the most potent inhibitors of HIV-1 entry and fusion, were less effective at inhibiting gp120 binding and were variably potent at inhibiting RANTES-induced signaling. With respect to inhibiting HIV-1 entry and fusion, PA12 but not PA14 was potently synergistic when used in combination with 2D7, RANTES, and CD4-immunoglobulin G2, which inhibits HIV-1 attachment. The data support a model wherein HIV-1 entry occurs in three stages: receptor (CD4) binding, coreceptor (CCR5) binding, and coreceptor-mediated membrane fusion. The antibodies described will be useful for further dissecting these events.
Olson
W C
WC
Progenics Pharmaceuticals, Inc., Tarrytown, New York 10591, USA.
Rabut
G E
GE
Nagashima
K A
KA
Tran
D N
DN
Anselma
D J
DJ
Monard
S P
SP
Segal
J P
JP
Thompson
D A
DA
Kajumo
F
F
Guo
Y
Y
Moore
J P
JP
Maddon
P J
PJ
Dragic
T
T
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000302:isolation & purification; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018946:Chemokine CCL5 / Q000276:immunology; D019742:Chemokines, CC / Q000378:metabolism*; D018604:Epitope Mapping; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D008561:Membrane Fusion; D016296:Mutagenesis; D019713:Receptors, CCR5 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
D000911:Antibodies, Monoclonal; D018946:Chemokine CCL5; D019742:Chemokines, CC; D015699:HIV Envelope Protein gp120; D019713:Receptors, CCR5; D000409:Alanine