Solution Structure of a Retro-inverso Peptide Analogue Mimicking the Foot-and-Mouth Disease Virus Major Antigenic Site

Abstract

The antigenic activity of a 19-mer peptide corresponding to the major antigenic region of foot-and-mouth disease virus and its retro-enantiomeric analogue was found to be completely abolished when they were tested in a biosensor system in trifluoroethanol. This suggests that the folding pattern, which is ␣-helix in trifluoroethanol (confirmed by CD measurement), does not correspond to the biologically relevant conformation(s) recognized by antibodies. The NMR structures of both peptides were thus determined in aqueous solution. These studies showed that the two peptides exhibit similar folding features, particularly in their C termini. This may explain in part the cross-reactive properties of the two peptides in aqueous solution. However, the retro-inverso analogue appears to be more rigid than the parent peptide and contains five atypical ␤-turns. This feature may explain why retro-inverso foot-andmouth disease virus peptides are often better recognized than the parent peptide by anti-virion antibodies.The major immunogenic site of foot-and-mouth disease virus (FMDV), 1 which is contained in the so-called G-H loop comprising amino acid residues 135-158 of capsid protein VP1 (viral capsid protein 1), is located in a disordered region on the surface of the particle (1). A single inoculum of a peptide corresponding to this region usually elicits levels of neutralizing antibodies that protect guinea pigs against a severe challenge with the cognate virus (2). In some instances, however, although the total reactivity of antibodies evaluated in immunochemical tests such as enzyme-linked immunosorbent assay is high, the level of neutralizing antibodies is low. This important problem has generated numerous studies aimed at enhancing the immunogenicity of this peptide with the hope of developing a peptide construct that could be used successfully as a synthetic vaccine (3). Recently, we have shown that antisera raised in rabbits against peptides corresponding to the sequence 141-159 of two variants of serotype A cross-reacted strongly with the corresponding retro-inverso analogue peptides. Most importantly, the retro-inverso analogues, also called retro all-D or retro-enantio peptides (4, 5), induced greater and longer-lasting antibody titers than did the respective parent peptides (6). Moreover, we showed with the FP variant analogue (which contains Phe and Pro residues at positions 148 and 153, respectively) that a single inoculation of the retro-inverso peptide elicited high levels of neutralizing antibodies that persisted longer than those induced against the corresponding L-peptide and protected guinea pigs challenged with the cognate virus (7). The enhanced immunogenic reactivities of retro-inverso analogues may result from their higher resistance to proteolysis in biological fluids (7). However, this property does not explain why in immunochemical assays, retro-inverso peptides are often better recognized than the parent peptide by anti-virus, anti-protein, or anti-peptide antibodies with equilibrium affinity cons...

Mapping the anatomy of a Plasmodium falciparum MSP-1 epitope using pseudopeptide-induced mono- and polyclonal antibodies and CD and NMR conformation analysis

“…Both isomer L L -and Retro-inverso peptides presented a typical helical pattern in TFE solution; such pattern can be assigned to an a-helix-like conformation having opposite orientation, similar to other studied cases (Petit et al, 1999). It is important to bear in mind that the parent all-L L 1513 peptide is constituted by L L -amino acids and Retro-inverso peptide by D D -amino acids; however, the latter has N !…”

“…CD and NMR studies were performed with peptides having no additional Cys residues as monomer forms for each molecule. Regarding native peptide sequence, the N-terminus Ala 61 on all-Retro and all-Retro-inverso analogues was carboxamidated and a 2-substituted malonic acid derivative was employed to replace the native C-terminus residue as previously reported (Petit et al, 1999). AllRetro 1513 was synthesised by using L L -amino acids and all-Retro-inverso by employing their corresponding enantiomer D D -residues.…”

“…The non-modified MSP-1 42-61 all-L L 1513 peptide and its reduced amide pseudopeptides were used for proton nuclear magnetic resonance ( 1 H NMR) analysis, as described (Petit et al, 1999).…”

Three-dimensional structure of foot-and-mouth disease virus and its biological functions

“…One of them corresponds to the GH loop of VP1 and has high variability and flexibility. A conserved Arg-Gly-Asp (RGD) motif is present in the highly variable GH loop and serves as the integrin-binding site [6,8,118]. So far, the VP1 GH loops in all native viruses are present in a disordered ''up'' conformation when examined using X-ray crystal diffraction, whereas that of the O1BFS strain soaked in dithiothreitol shows a well-ordered ''down'' conformation [1,35,56,83,84,89].…”

Mimicry of Native Peptide Antigens by the Corresponding Retro-Inverso Analogs Is Dependent on Their Intrinsic Structure and Interaction Propensities

“…This is a plausible hypothesis considering that the extended conformation is more likely to be flexible and would provide substantial leeway in optimizing common interactions. However, there are two cases where it has been shown that the ri analog does possess turn-like structures similar to the native peptide (19,20). In one of the cases, the presence of a number of glycine residues (three of nine) could be imparting flexibility to the two versions of the peptide allowing the conformational propensities to overlap (19).…”