title: Strain specificity and binding affinity requirements of neutralizing monoclonal antibodies to the C4 domain of gp120 from human immunodeficiency virus type 1.
abstract: The binding properties of seven CD4-blocking monoclonal antibodies raised against recombinant gp120 of human immunodeficiency virus type 1 strain MN (HIV-1MN) and two CD4-blocking monoclonal antibodies to recombinant envelope glycoproteins gp120 and gp160 of substrain IIIB of HIVLAI were analyzed. With a panel of recombinant gp120s from seven diverse HIV-1 isolates, eight of the nine antibodies were found to be strain specific and one was broadly cross-reactive. Epitope mapping revealed that all nine antibodies bound to epitopes located in the fourth conserved domain (C4) of gp120. Within this region, three distinct epitopes could be identified: two were polymorphic between HIV-1 strains, and one was highly conserved. Studies with synthetic peptides demonstrated that the conserved epitope, recognized by antibody 13H8, was located between residues 431 and 439. Site-directed mutagenesis of gp120 demonstrated that residue 429 and/or 432 was critical for the binding of the seven antibodies to gp120 from HIV-1MN. Similarly, residues 423 and 429 were essential for the binding of monoclonal antibody 5C2 raised against gp120 from HIV-1IIIB. The amino acids located at positions 423 and 429 were found to vary between strains of HIV-1 as well as between molecular clones derived from the MN and LAI isolates of HIV-1. Polymorphism at these positions prevented the binding of virus-neutralizing monoclonal antibodies and raised the possibility that HIV-1 neutralization serotypes may be defined on the basis of C4 domain sequences. Analysis of the binding characteristics of the CD4-blocking antibodies demonstrated that their virus-neutralizing activity was directly proportional to their gp120-binding affinity. These studies account for the strain specificity of antibodies to the C4 domain of gp120 and demonstrate for the first time that antibodies to this region can be as effective as those directed to the principal neutralizing determinant (V3 domain) in neutralizing HIV-1 infectivity.
authors.affiliation: Department of Immunology, Genentech, Inc., South San Francisco, California 94080.
authors.forename: G R
authors.initials: GR
authors.lastname: Nakamura
authors.forename: R
authors.initials: R
authors.lastname: Byrn
authors.forename: D M
authors.initials: DM
authors.lastname: Wilkes
authors.forename: J A
authors.initials: JA
authors.lastname: Fox
authors.forename: M R
authors.initials: MR
authors.lastname: Hobbs
authors.forename: R
authors.initials: R
authors.lastname: Hastings
authors.forename: H C
authors.initials: HC
authors.lastname: Wessling
authors.forename: M A
authors.initials: MA
authors.lastname: Norcross
authors.forename: B M
authors.initials: BM
authors.lastname: Fendly
authors.forename: P W
authors.initials: PW
authors.lastname: Berman
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D001665:Binding Sites; D001666:Binding Sites, Antibody; D015704:CD4 Antigens / Q000276:immunology / Q000378:metabolism*; D002460:Cell Line; D003429:Cross Reactions; D004220:Disulfides / Q000032:analysis; D000939:Epitopes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007700:Kinetics; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009500:Neutralization Tests; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017433:Protein Structure, Secondary; D013045:Species Specificity
chemical_list: D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D004220:Disulfides; D000939:Epitopes; D015699:HIV Envelope Protein gp120