title: Identification of neutralizing conformational epitopes on the human papillomavirus type 31 major capsid protein and functional implications.
abstract: The aim of this study was to characterize the conformational neutralizing epitopes of the major capsid protein of human papillomavirus type 31. Analysis of the epitopes was performed by competitive epitope mapping using 15 anti-HPV31 and by reactivity analysis using a HPV31 mutant with an insertion of a seven-amino acid motif within the FG loop of the capsid protein. Fine mapping of neutralizing conformational epitopes on HPV L1 was analyzed by a new approach using a system displaying a combinatorial library of constrained peptides exposed on E. coli flagella. The findings demonstrate that the HPV31 FG loop is dense in neutralizing epitopes and suggest that HPV31 MAbs bind to overlapping but distinct epitopes on the central part of the FG loop, in agreement with the exposure of the FG loop on the surface of HPV VLPs, and thus confirming that neutralizing antibodies are mainly located on the tip of capsomeres. In addition, we identified a crossreacting and partially crossneutralizing conformational epitope on the relatively well conserved N-terminal part of the FG loop. Moreover, our findings support the hypothesis that there is no correlation between neutralization and the ability of MAbs to inhibit VLP binding to heparan sulfate, and confirm that the blocking of virus attachment to the extracellular matrix is an important mechanism of neutralization.
authors.affiliation: INSERM U618, Université François Rabelais, Tours, France.
authors.forename: Maxime J J
authors.initials: MJ
authors.lastname: Fleury
authors.forename: Antoine
authors.initials: A
authors.lastname: Touzé
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Maurel
authors.forename: Thierry
authors.initials: T
authors.lastname: Moreau
authors.forename: Pierre
authors.initials: P
authors.lastname: Coursaget
mesh_terms: D052685:Alphapapillomavirus / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000378:metabolism; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018604:Epitope Mapping / Q000379:methods; D005109:Extracellular Matrix / Q000378:metabolism; D006497:Heparan Sulfate / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009500:Neutralization Tests / Q000379:methods*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014771:Virion / Q000378:metabolism; D053585:Virus Attachment
chemical_list: D000911:Antibodies, Monoclonal; D036022:Capsid Proteins; D006497:Heparan Sulfate; D011994:Recombinant Proteins