title: Monoclonal antibody m18 paratope leading to dual receptor antagonism of HIV-1 gp120.
abstract: We sought to identify sequences in the monoclonal antibody m18 complementarity determining regions (CDRs) that are responsible for its interaction with HIV-1 gp120 and inhibition of the envelope receptor binding sites. In the accompanying paper (DOI 10.1021/bi101160r), we reported that m18 inhibits CD4 binding through a nonactivating mechanism that, at the same time, induces conformational effects leading to inhibition of the coreceptor site. Here, we sought to define the structural elements in m18 responsible for these actions. Direct binding and competition analyses using surface plasmon resonance showed that YU-2 gp120 binding is stabilized by a broad paratope of residues in the m18 CDRs. Additionally, several m18 residues were identified for which mutants retained high affinity for gp120 but had suppressed CD4 and 17b inhibition activities. A subset of these mutants did, however, neutralize HXBc2 viral infection. The results obtained in this work demonstrate that the combined m18 paratope contains subsets of residues that are differentially important for the binding and inhibition functions of the m18 neutralizing antibody. The data also add to prior observations that high-affinity antibodies that do not inhibit monomeric gp120 receptor site interactions may still exhibit significant antiviral activity.
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States.
authors.forename: Syna Kuriakose
authors.initials: SK
authors.lastname: Gift
authors.forename: Karyn
authors.initials: K
authors.lastname: McFadden
authors.forename: Isaac J
authors.initials: IJ
authors.lastname: Zentner
authors.forename: Srivats
authors.initials: S
authors.lastname: Rajagopal
authors.forename: Mei-Yun
authors.initials: MY
authors.lastname: Zhang
authors.forename: Dimiter S
authors.initials: DS
authors.lastname: Dimitrov
authors.forename: Irwin M
authors.initials: IM
authors.lastname: Chaiken
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057134:Antibodies, Neutralizing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D015704:CD4 Antigens / Q000276:immunology / Q000378:metabolism*; D022801:Complementarity Determining Regions / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015483:HIV Antibodies / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015497:HIV-1 / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D015704:CD4 Antigens; D022801:Complementarity Determining Regions; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D007140:Immunoglobulin Fab Fragments