title: Glycan masking of Plasmodium vivax Duffy Binding Protein for probing protein binding function and vaccine development.
abstract: Glycan masking is an emerging vaccine design strategy to focus antibody responses to specific epitopes, but it has mostly been evaluated on the already heavily glycosylated HIV gp120 envelope glycoprotein. Here this approach was used to investigate the binding interaction of Plasmodium vivax Duffy Binding Protein (PvDBP) and the Duffy Antigen Receptor for Chemokines (DARC) and to evaluate if glycan-masked PvDBPII immunogens would focus the antibody response on key interaction surfaces. Four variants of PVDBPII were generated and probed for function and immunogenicity. Whereas two PvDBPII glycosylation variants with increased glycan surface coverage distant from predicted interaction sites had equivalent binding activity to wild-type protein, one of them elicited slightly better DARC-binding-inhibitory activity than wild-type immunogen. Conversely, the addition of an N-glycosylation site adjacent to a predicted PvDBP interaction site both abolished its interaction with DARC and resulted in weaker inhibitory antibody responses. PvDBP is composed of three subdomains and is thought to function as a dimer; a meta-analysis of published PvDBP mutants and the new DBPII glycosylation variants indicates that critical DARC binding residues are concentrated at the dimer interface and along a relatively flat surface spanning portions of two subdomains. Our findings suggest that DARC-binding-inhibitory antibody epitope(s) lie close to the predicted DARC interaction site, and that addition of N-glycan sites distant from this site may augment inhibitory antibodies. Thus, glycan resurfacing is an attractive and feasible tool to investigate protein structure-function, and glycan-masked PvDBPII immunogens might contribute to P. vivax vaccine development.
authors.affiliation: Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
authors.forename: Sowmya
authors.initials: S
authors.lastname: Sampath
authors.forename: Chris
authors.initials: C
authors.lastname: Carrico
authors.forename: Joel
authors.initials: J
authors.lastname: Janes
authors.forename: Sairam
authors.initials: S
authors.lastname: Gurumoorthy
authors.forename: Claire
authors.initials: C
authors.lastname: Gibson
authors.forename: Martin
authors.initials: M
authors.lastname: Melcher
authors.forename: Chetan E
authors.initials: CE
authors.lastname: Chitnis
authors.forename: Ruobing
authors.initials: R
authors.lastname: Wang
authors.forename: William R
authors.initials: WR
authors.lastname: Schief
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Smith
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000276:immunology; D000913:Antibodies, Protozoan / Q000276:immunology; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D004375:Duffy Blood-Group System / Q000235:genetics / Q000276:immunology; D006031:Glycosylation; D017780:Malaria Vaccines / Q000235:genetics / Q000276:immunology*; D051379:Mice; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology*; D011485:Protein Binding; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D051381:Rats; D011956:Receptors, Cell Surface / Q000235:genetics / Q000276:immunology*
chemical_list: C473745:ACKR1 protein, human; D057134:Antibodies, Neutralizing; D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D004375:Duffy Blood-Group System; C066001:Duffy antigen binding protein, Plasmodium; D017780:Malaria Vaccines; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface