title: Toward effective HIV vaccination: induction of binary epitope reactive antibodies with broad HIV neutralizing activity.
abstract: We describe murine monoclonal antibodies (mAbs) raised by immunization with an electrophilic gp120 analog (E-gp120) expressing the rare ability to neutralize genetically heterologous human immunodeficiency virus (HIV) strains. Unlike gp120, E-gp120 formed covalent oligomers. The reactivity of gp120 and E-gp120 with mAbs to reference neutralizing epitopes was markedly different, indicating their divergent structures. Epitope mapping with synthetic peptides and electrophilic peptide analogs indicated binary recognition of two distinct gp120 regions by anti-E-gp120 mAbs, the 421-433 and 288-306 peptide regions. Univalent Fab and single chain Fv fragments expressed the ability to recognize both peptides. X-ray crystallography of an anti-E-gp120 Fab fragment revealed two neighboring cavities, the typical antigen-binding cavity formed by the complementarity determining regions (CDRs) and another cavity dominated by antibody heavy chain variable (V(H)) domain framework (FR) residues. Substitution of the FR cavity V(H) Lys-19 residue by an Ala residue resulted in attenuated binding of the 421-433 region peptide probe. The CDRs and V(H) FR replacement/silent mutation ratios exceeded the ratio for a random mutation process, suggesting adaptive development of both putative binding sites. All mAbs studied were derived from V(H)1 family genes, suggesting biased recruitment of the V gene germ line repertoire by E-gp120. The conserved 421-433 region of gp120 is essential for HIV binding to host CD4 receptors. This region is recognized weakly by the FR of antibodies produced without exposure to HIV, but it usually fails to induce adaptive synthesis of neutralizing antibodies. We present models accounting for improved CD4-binding site recognition and broad HIV neutralizing activity of the mAbs, long sought goals in HIV vaccine development.
authors.affiliation: Department of Pathology and Laboratory Medicine, Chemical Immunology Research Center, University of Texas-Houston Medical School, Houston, Texas 77030, USA.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Stephanie
authors.initials: S
authors.lastname: Planque
authors.forename: Yukie
authors.initials: Y
authors.lastname: Mitsuda
authors.forename: Giovanni
authors.initials: G
authors.lastname: Nitti
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Taguchi
authors.forename: Lei
authors.initials: L
authors.lastname: Jin
authors.forename: Jindrich
authors.initials: J
authors.lastname: Symersky
authors.forename: Stephane
authors.initials: S
authors.lastname: Boivin
authors.forename: Marcin
authors.initials: M
authors.lastname: Sienczyk
authors.forename: Maria
authors.initials: M
authors.lastname: Salas
authors.forename: Carl V
authors.initials: CV
authors.lastname: Hanson
authors.forename: Sudhir
authors.initials: S
authors.lastname: Paul
mesh_terms: D016915:AIDS Vaccines / Q000276:immunology* / Q000592:standards; D019943:Amino Acid Substitution; D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism; D018360:Crystallography, X-Ray; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology; D015483:HIV Antibodies / Q000276:immunology / Q000627:therapeutic use*; D006801:Humans; D007128:Immunoglobulin Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D011487:Protein Conformation
chemical_list: D016915:AIDS Vaccines; D015704:CD4 Antigens; D000939:Epitopes; D015483:HIV Antibodies; D007128:Immunoglobulin Fragments