title: Identification of an Immunogenic Mimic of a Conserved Epitope on the Plasmodium falciparum Blood Stage Antigen AMA1 Using Virus-Like Particle (VLP) Peptide Display.
abstract: We have developed a peptide display platform based on VLPs of the RNA bacteriophage MS2 that combines the high immunogenicity of VLP display with affinity selection capabilities. Random peptides can be displayed on the VLP surface by genetically inserting sequences into a surface-exposed loop of the viral coat protein. VLP-displayed peptides can then be isolated by selection using antibodies, and the VLP selectants can then be used directly as immunogens. Here, we investigated the ability of this platform to identify mimotopes of a highly conserved conformational epitope present on the Plasmodium falciparum blood-stage protein AMA1. Using 4G2, a monoclonal antibody that binds to this epitope and is a potent inhibitor of erythrocyte invasion, we screened three different VLP-peptide libraries and identified specific VLPs that bound strongly to the selecting mAb. We then tested the ability of a handful of selected VLPs to elicit anti-AMA1 antibody responses in mice. Most of the selected VLPs failed to reliably elicit AMA1 specific antibodies. However, one VLP consistently induced antibodies that cross-reacted with AMA1. Surprisingly, this VLP bound to 4G2 more weakly than the other selectants we identified. Taken together, these data demonstrate that VLP-peptide display can identify immunogenic mimics of a complex conformational epitope and illustrate the promise and challenges of this approach.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM 87131, United States of America.
authors.forename: Erin
authors.initials: E
authors.lastname: Crossey
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM 87131, United States of America.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Frietze
authors.affiliation: Laboratory of Malaria Immunology and Vaccinology, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, United States of America.
authors.forename: David L
authors.initials: DL
authors.lastname: Narum
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM 87131, United States of America.
authors.forename: David S
authors.initials: DS
authors.lastname: Peabody
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM 87131, United States of America.
authors.forename: Bryce
authors.initials: B
authors.lastname: Chackerian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000913:Antibodies, Protozoan / Q000276:immunology; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions; D000953:Antigens, Protozoan / Q000737:chemistry / Q000276:immunology*; D000954:Antigens, Surface / Q000737:chemistry / Q000276:immunology; D002850:Chromatography, Gel; D003429:Cross Reactions; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D017909:Levivirus; D017780:Malaria Vaccines / Q000276:immunology; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D010963:Plasmodium falciparum / Q000276:immunology*; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry / Q000276:immunology*; D020539:Sequence Analysis, Protein; D058425:Vaccines, Virus-Like Particle / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D000939:Epitopes; D017780:Malaria Vaccines; D008565:Membrane Proteins; D019151:Peptide Library; D010455:Peptides; D015800:Protozoan Proteins; D058425:Vaccines, Virus-Like Particle; C090077:apical membrane antigen I, Plasmodium