title: Characterization of a discontinuous neutralizing epitope on glycoprotein B of human cytomegalovirus.
abstract: Human cytomegalovirus (HCMV) is a ubiquitously distributed pathogen that causes severe disease in immunosuppressed patients and newborn infants infected in utero. The viral envelope glycoprotein B (gB) is an attractive molecule for active vaccination and passive immunoprophylaxis and therapy. Using human monoclonal antibodies (MAbs), we have recently identified antigenic region 4 (AD-4) on gB as an important target for neutralizing antibodies. AD-4 is formed by a discontinuous sequence comprising amino acids 121 to 132 and 344 to 438 of gB of HCMV strain AD169. To map epitopes for human antibodies on this protein domain, we used a three-dimensional (3D) model of HCMV gB to identify surface-exposed amino acids on AD-4 and selected juxtaposed residues for alanine scans. A tyrosine (Y) at position 364 and a lysine (K) at position 379 (the YK epitope), which are immediate neighbors on the AD-4 surface, were found to be essential for binding of the human MAbs. Recognition of AD-4 by sera from HCMV-infected individuals also was largely dependent on these two residues, indicating a general importance for the antibody response against AD-4. A panel of AD-4 recombinant viruses harboring mutations at the crucial antibody binding sites was generated. The viruses showed significantly reduced susceptibility to neutralization by AD-4-specific MAbs or polyclonal AD-4-specific antibodies, indicating that the YK epitope is dominant for the AD-4-specific neutralizing antibody response during infection. To our knowledge, this is the first molecular identification of a functional discontinuous epitope on HCMV gB. Induction of antibodies specific for this epitope may be a desirable goal following vaccination with gB.
authors.affiliation: Institut für Klinische und Molekulare Virologie, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Nadja
authors.initials: N
authors.lastname: Spindler
authors.forename: Pia
authors.initials: P
authors.lastname: Rücker
authors.forename: Sonja
authors.initials: S
authors.lastname: Pötzsch
authors.forename: Uschi
authors.initials: U
authors.lastname: Diestel
authors.forename: Heinrich
authors.initials: H
authors.lastname: Sticht
authors.forename: Luis
authors.initials: L
authors.lastname: Martin-Parras
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Winkler
authors.forename: Michael
authors.initials: M
authors.lastname: Mach
mesh_terms: D019943:Amino Acid Substitution; D000911:Antibodies, Monoclonal / Q000276:immunology; D057134:Antibodies, Neutralizing / Q000276:immunology*; D003587:Cytomegalovirus / Q000737:chemistry / Q000276:immunology*; D004252:DNA Mutational Analysis; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D018985:Epitopes, B-Lymphocyte; D014759:Viral Envelope Proteins; C040495:glycoprotein B, Simplexvirus