David Limal

Delineation of a neutralizing subregion within the immunodominant epitope (GH loop) of foot-and-mouth disease virus VP1 which does not contain the RGD motif

The major immunogenic site of foot-and-mouth disease virus (FMDV) is contained in a disordered loop comprising residues 134-158 of capsid protein VP1, located on the surface of the viral particle. Peptides corresponding to this sequence generally elicit protective levels of neutralizing antibodies in guinea pigs. In some instances, however, the level of neutralizing antibodies is low although the level of antibodies against the peptide, determined by ELISA, is as high as that in the sera with high neutralizing antibody titres. In an attempt to ascertain the reason for this difference, we have synthesized on a cellulose membrane 10 overlapping decapeptides, offset by one residue, covering the segment 141-159 of VP1 of two viruses belonging to serotypes A12 and O1, and tested them with guinea pig antisera raised against peptide 141-159, VP1 and FMDV particles (SPOTscan method). With type A, some peptides which were strongly positive with highly neutralizing antisera did not include the RGD triplet located at residues 145-147. In contrast, antisera with low neutralization titres reacted only with decapeptides which included the RGD motif. Moreover, peptide 147-156 coupled to keyhole limpet haemocyanin, but not peptide 141-149 coupled to the same carrier, elicited high levels of neutralizing antibodies in guinea pigs. In the case of serotype O, highly neutralizing antisera to virus reacted in ELISA with peptides 141-150 (containing the RGD motif) and 135-144 (located upstream from the RGD motif). The results suggest that the RGD triplet is not an indispensable constituent of peptides able to elicit a neutralizing antibody response against the virus.

The semicarbazone peptidomimetic group in imino aza peptides

Abstract The semicarbazone moiety (CCHNNRCONHC), either obtained by coupling a peptide aldehyde with a semicarbazide, or by action of an alkylisocyanate on a peptide hydrazone, is a dipeptide isostere. The structure of four imino aza dipeptides, analogues of the Pro-Gly, Pro-Ala and Pro-Phe dipeptides, has been studied in solution by 1 H-NMR and IR spectroscopy, and in the solid state by X-ray diffraction.

Direct synthesis of N-protected β-amino dimethylhydroxamates: Application to the solid-phase synthesis of a peptide incorporating a new amide bond surrogate Ψ[CH2CH2NH]

Abstract A rapid and efficient one-step synthesis of N-protected β-amino dimethylhydroxamates starting from diazo ketones is reported. A Fmoc-protected β-amino aldehyde obtained by reduction of its corresponding dimethylhydroxamate was incorporated during solid phase assembly of an antigenic peptide. The resulting pseudopeptide containing an ethylene amino bond Ψ[CH 2 CH 2 NH] was efficiently recovered.

Do Bioactive Peptides Display Native-Like Conformations When Bound to a Solid Support?

High-resolution magic angle spinning (HRMAS) NMR spectroscopy is a very promising technique in the field of solid phase organic chemistry for the analysis of resin-bound compounds, including small molecules and peptides [1,2]. We have successfully applied HRMAS NMR to the conformational study of bioactive peptides covalently attached to different resins [3]. The combination of the swelling and solvation properties of resin-bound peptides with the chemico-physical nature of the solid supports plays a fundamental role in the characterization of such conjugates by HRMAS technique. The secondary structure adopted by the sequence 141GSGVRGDFGSLAPRVARQL159, which delineates the major antigenic site of the viral protein VP1 of foot-and-mouth disease virus (FMDV), bound to three different types of resin, namely MBHA, PEGA and POEPOP, has been determined and compared with that of the same peptide free in solution.