Identification of a new neutralizing epitope conformationally affected by the attachment of CD4 to gp120.
We have developed a strategy to purify and characterize various anti-gp120 antibody populations in HIV+ sera by using anti-Id mAb. One preparation of human anti-gp120 antibody (ES+ Ab) isolated on an anti-Id mAb (ES)-conjugated immunoabsorbent exhibited a novel neutralizing epitope specificity. The ES+ Ab bound only to the native form of recombinant gp120SF2 and gp120IIIB and not to the third hypervariable region (V3) loop peptide. In contradistinction to other CD4-gp120-inhibiting and V3-specific neutralizing antibodies, ES+ Ab exhibited a dose-dependent enhancement of binding to recombinant gp120 in the presence of recombinant soluble CD4. In addition, flow cytometric analysis revealed a similar increase in the binding of ES+ Ab to the native form of gp120 expressed on the HIV-infected cells. The ES+ Ab competed with CD4 binding site- and V3-specific antibodies in binding to gp120, suggesting that the ES+ Ab epitope is located near the CD4 binding site epitope and the V3 region. The ES+ Ab neutralized six genetically distinct HIV-1 strains. The neutralizing activity of ES+ Ab on HIVIIIB was significantly increased in the presence of human anti-CD4 binding site mAb. These data suggest that the ES+ Ab epitope represents a conserved, conformational, neutralization target on gp120 that may be involved in viral infection in an event after the CD4-gp120 interaction and that is distinct from previously defined neutralizing epitopes of gp120. This finding may be important for the development of an AIDS vaccine and immunotherapy.
Kang
C Y
CY
IDEC Pharmaceuticals Corporation, La Jolla, CA 92037.
Hariharan
K
K
Posner
M R
MR
Nara
P
P
D000595:Amino Acid Sequence; D000918:Antibody Specificity; D015704:CD4 Antigens / Q000276:immunology*; D000939:Epitopes; D015483:HIV Antibodies / Q000276:immunology; D015488:HIV Antigens / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000276:immunology*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000276:immunology; D013329:Structure-Activity Relationship
D015704:CD4 Antigens; D000939:Epitopes; D015483:HIV Antibodies; D015488:HIV Antigens; D015699:HIV Envelope Protein gp120; D011994:Recombinant Proteins