Functional Mimicry of a Discontinuous Antigenic Site by a Designed Synthetic Peptide

Abstract

Functional reproduction of the discontinuous antigenic site D of foot-and-mouth disease virus (FMDV) has been achieved by means of synthetic peptide constructions that integrate each of the three protein loops that define the antigenic site into a single molecule. The site D mimics were designed on the basis of the X-ray structure of FMDV type C-S8c1 with the aid of molecular dynamics, so that the five residues assumed to be involved in antigenic recognition are located on the same face of the molecule, exposed to solvent and defining a set of native-like distances and angles. The designed site D mimics are disulfide-linked heterodimers that consist of a larger unit containing VP2(71-84), followed by a polyproline module and by VP3(52-62), and a smaller unit corresponding to VP1(188-194) (VP=viral protein). Guinea pig antisera to the peptides recognized the viral particle and competed with site D-specific monoclonal antibodies, while inoculation with a simple (not covalently joined to one another) admixture of the three VP1-VP3 sequences yielded no detectable virus-specific serum conversion. Similar results have been reproduced in two bovines. Antisera to the peptides also moderately neutralize FMDV in cell cultures and partially protect guinea pigs against challenge with the virus. These results demonstrate functional mimicry of the discontinuous site D by the peptides, which are therefore obvious candidates for a multicomponent, peptide-based vaccine against FMDV.

Identification of a Dantrolene-binding Sequence on the Skeletal Muscle Ryanodine Receptor

“…The relatively high concentrations (Ͻ1:50 dilution) of mouse ascites required to bring about inhibition of specific photolabeling is likely due to the low antigen affinities of IgM antibodies, which are part of the early immune response of the body, relative to mature IgG antibodies (29). These data also strengthen the experimental evidence that, in vitro, synthetic domain peptides are capable of assuming the native conformation(s) of domains present in the parent protein, RyR1 in this case (35)(36)(37).…”

Crystal Structure of an Anti-meningococcal Subtype P1.4 PorA Antibody Provides Basis for Peptide–Vaccine Design

“…These restraints, such as cyclisations, disulphide bonding or synthetic mimics of hydrogen bonds, are often introduced by trialand-error, and in a few cases based on a structural design. 17,[39][40][41][42][43][44][45] The structure-based design of cyclic peptides presented here yielded two peptides that elicited titres in mice, which recognised bacterial cells of subtype P1.7-2,4. In a subset of the mice tested, the peptide-elicited antibodies were capable of complement-mediated killing of the bacteria.…”

“…In the first case, a peptide vaccine candidate may be designed mimicking the structure of the cognate protein. 39,40 In the latter case, the structure of the epitope bound to a Fab fragment of an effective antibody may be the aspired conformation of the vaccine peptide 17,41,42 (this study). For both scenarios, conformational restraints to restrict conformational possibilities of the peptides are generally needed to obtain a cross-reactive immune response.…”

“…Similar variations between individual animals from a group that was immunised with peptide vaccines were found in protection to viral challenges. 39,42 Cabezas et al 42 found two reasons for the lower functional antibody titres in two individual animals. In one animal, a high concentration of antibodies specific for the antigenic protein was found, but the antibodies had a lower potency because of a different specificity.…”

Carbohydrate Mimotopes in the Rational Design of Cancer Vaccines

“…3) The crystallization of antigens with and without corresponding receptors provides information relevant to identifying topographic features that need to be retained in engineered peptides [80,81]. Generally, structure assisted approaches involve (i) determining the three-dimensional structure of an antigen, (ii) identifying reactive epitopes, (iii) generation of an antigen fragment that contains the targeted epitope, and (iv) compensation for destabilization [82,83].…”