title: Structural analysis of the synthetic Duffy Binding Protein (DBP) antigen DEKnull relevant for Plasmodium vivax malaria vaccine design.
abstract: The Plasmodium vivax vaccine candidate Duffy Binding Protein (DBP) is a protein necessary for P. vivax invasion of reticulocytes. The polymorphic nature of DBP induces strain-specific immune responses that pose unique challenges for vaccine development. DEKnull is a synthetic DBP based antigen that has been engineered through mutation to enhance induction of blocking inhibitory antibodies. We determined the x-ray crystal structure of DEKnull to identify if any conformational changes had occurred upon mutation. Computational and experimental analyses assessed immunogenicity differences between DBP and DEKnull epitopes. Functional binding assays with monoclonal antibodies were used to interrogate the available epitopes in DEKnull. We demonstrate that DEKnull is structurally similar to the parental Sal1 DBP. The DEKnull mutations do not cause peptide backbone shifts within the polymorphic loop, or at either the DBP dimerization interface or DARC receptor binding pockets, two important structurally conserved protective epitope motifs. All B-cell epitopes, except for the mutated DEK motif, are conserved between DEKnull and DBP. The DEKnull protein retains binding to conformationally dependent inhibitory antibodies. DEKnull is an iterative improvement of DBP as a vaccine candidate. DEKnull has reduced immunogenicity to polymorphic regions responsible for strain-specific immunity while retaining conserved protein folds necessary for induction of strain-transcending blocking inhibitory antibodies.
authors: Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, Saint Louis, Missouri, United States of America.
authors: Edwin
authors: E
authors: Chen
authors: Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, Saint Louis, Missouri, United States of America.
authors: Nichole D
authors: ND
authors: Salinas
authors: Global Health Infectious Disease Research, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America.
authors: Francis B
authors: FB
authors: Ntumngia
authors: Global Health Infectious Disease Research, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America.
authors: John H
authors: JH
authors: Adams
authors: Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, Saint Louis, Missouri, United States of America; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, Missouri, United States of America.
authors: Niraj H
authors: NH
authors: Tolia
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000953:Antigens, Protozoan / Q000235:genetics*; D018360:Crystallography, X-Ray; D018985:Epitopes, B-Lymphocyte / Q000235:genetics / Q000276:immunology; D006801:Humans; D017780:Malaria Vaccines / Q000276:immunology*; D016780:Malaria, Vivax / Q000276:immunology / Q000517:prevention & control*; D008958:Models, Molecular; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology*; D011485:Protein Binding; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; C066001:Duffy antigen binding protein, Plasmodium; D018985:Epitopes, B-Lymphocyte; D017780:Malaria Vaccines; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface