Evidence by peptide mapping that the region CD4(81-92) is involved in gp120/CD4 interaction leading to HIV infection and HIV-induced syncytium formation.
Peptide fragments of the CD4 molecule were compared in their ability to 1) inhibit CD4-dependent HIV-induced cell fusion; 2) inhibit CD4-dependent HIV infection in vitro; and 3) block gp120 envelope glycoprotein binding to CD4. Peptides from the region CD4(81-92), although inactive when underivatized, were equipotent inhibitors of CD4-dependent virus infection, cell fusion, and CD4/gp120 binding when derivatized via benzylation and acetylation. Peptides of identical chemical composition, but altered sequence and derivatization pattern that blocked gp120 binding to either CD4-positive cells or solubilized CD4, also blocked infection and fusion with similar potencies. Those that did not block gp120/CD4 interaction were also inactive in HIV-1 infection and cell fusion assays. No other peptide fragments of the CD4 molecule inhibited fusion, infection, or CD4/gp120 interaction. The peptide CD4(23-56), derived from a region of CD4 implicated in binding of CD4 antibodies that neutralize HIV infection and cell fusion, had no effect on CD4-dependent cell fusion, HIV-1 infection, or CD4/gp120 binding, but did reverse OKT4A and anti-Leu 3a blockade of gp120 binding to CD4. These data provide evidence that the 81-92 region of CD4 is directly involved in gp120 binding leading to CD4-dependent HIV infection and syncytium formation. Previous observations with structural mutants of CD4 suggest that the CDR2-homologous region of CD4 is also involved, either directly or indirectly, in binding of gp120 to CD4. The CDR2- and CDR3-like domains of CD4 may both contribute to the binding of the HIV envelope necessary for HIV-1 infection and HIV-1-induced cell fusion.
Advanced Bioscience Laboratories, Inc., Kensington, MD 20895.
V S
VS
Kalyanaraman
D M
DM
Rausch
J
J
Osborne
M
M
Padgett
K M
KM
Hwang
J D
JD
Lifson
L E
LE
Eiden
D000911:Antibodies, Monoclonal / Q000276:immunology; D001667:Binding, Competitive; D015704:CD4 Antigens / Q000378:metabolism* / Q000648:ultrastructure; D002459:Cell Fusion; D000939:Epitopes; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015658:HIV Infections / Q000503:physiopathology*; D006801:Humans; D066298:In Vitro Techniques; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism*; D010449:Peptide Mapping; D011485:Protein Binding; D013329:Structure-Activity Relationship
D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D000939:Epitopes; D015699:HIV Envelope Protein gp120; D010446:Peptide Fragments