Enhanced antigenicity of a four-contact-residue epitope of the measles virus hemagglutinin protein by phage display libraries: evidence of a helical structure in the putative active site.
Antigenicity and conformational propensities of synthetic peptides corresponding to the sequential epitope H236-255 of the measles virus hemagglutinin protein were investigated. This epitope corresponds to the neutralising and protective monoclonal antibody BH129 and includes Arg243, implicated in CD46-down-regulation and Arg253 that has been mapped to the putative enzymatic site. Fine mapping with truncation-, elongation-, Gly- and Ala-substitution analogues defined EL-QL as the critical residues of the minimal epitope S244ELSQL249. CD spectra of peptides, comparison with the 3D-structure of homologous sequences, and prediction algorithms suggested a helical structure with the contact residues E245L-QL249 located on the protein surface. Mimotopes obtained with a 6-mer phage display library contained a consensus Pro (important for binding) instead of Ser247 of the wild-type sequence (irrelevant for binding). The kink induced by Pro seemed to be essential to bring the 4 contact-residues in the mimotopes and in the corresponding short peptides together. CD analysis and prediction algorithms suggested that non-helical conformations of the phage insert and of the peptides may favourably mimic the antigenic helical turns of the wild-type sequence, resulting in an up to 135 times higher antigenicity of the mAb towards the mimotope peptides.
Deroo
S
S
Laboratoire National de Santé, Luxembourg, Luxembourg.
El Kasmi
K C
KC
Fournier
P
P
Theisen
D
D
Brons
N H
NH
Herrmann
M
M
Desmet
J
J
Muller
C P
CP
D000818:Animals; D000937:Antigen-Antibody Reactions / Q000235:genetics; D001435:Bacteriophages / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites / Q000502:physiology; D000939:Epitopes / Q000096:biosynthesis / Q000737:chemistry / Q000276:immunology*; D006389:Hemagglutinins, Viral / Q000276:immunology*; D008459:Measles virus / Q000737:chemistry*; D051379:Mice; D018716:Molecular Mimicry / Q000235:genetics; D019151:Peptide Library; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
D000939:Epitopes; D006389:Hemagglutinins, Viral; D019151:Peptide Library