Neutralizing epitopes of type O foot-and-mouth disease virus. II. Mapping three conformational sites with synthetic peptide reagents
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N R Parry1, P V Barnett, E J Ouldridge
1Department of Virology, Wellcome Biotechnology Ltd, Beckenham, Kent, U.K.
Abstract:
Four neutralizing monoclonal antibodies (MAbs), recognizing three functionally independent, conformational sites on type O foot-and-mouth disease virus (FMDV) failed to react with immobilized structural proteins or synthetic peptides but bound to the isolated capsid protein VP1 and peptides in solution. Inhibition ELISA techniques were, therefore, applied using peptide antigens and anti-peptide sera to block MAb binding to virus particles, permitting the identification of those portions of the VP1 protein contributing to the epitopes. The binding site of one MAb, which neutralized a range of type O FMDV isolates, was shown to have components within regions 146 to 150 and 200 to 213 of VP1 with a critical involvement of the amino acids at positions 146 and 206 or 207. The determinants recognized by two other MAbs which were directed at similar, but not identical, epitopes from a second site included components from the 200 to 213 and 143 to 146 regions with amino acids 143 and 144, respectively, appearing critical for the inhibition of the virus binding of the two antibodies. These results demonstrate that the two previously identified immunogenic tracts of VP1 are brought into proximity in the quaternary structure of the virion to form an antigenic domain containing several conformational epitopes, some of which are functionally independent. A fourth, strain-specific MAb was effectively blocked from reacting with virus by peptides corresponding to residues 161 to 180 and 200 to 213.
Insights
Four neutralizing monoclonal antibodies (MAbs) targeting foot-and-mouth disease virus (FMDV) revealed that VP1 protein regions form distinct antigenic sites. These findings help understand FMDV immune responses and vaccine development.
Area of Science:
- Virology
- Immunology
- Structural Biology
Background:
- Foot-and-mouth disease virus (FMDV) poses a significant threat to livestock.
- Understanding FMDV antigenicity is crucial for vaccine development.
- Monoclonal antibodies (MAbs) are key tools for studying viral epitopes.
Purpose of the Study:
- To identify specific regions of the FMDV VP1 protein involved in antibody binding and neutralization.
- To characterize the conformational epitopes recognized by neutralizing MAbs.
- To investigate the structural organization of antigenic sites on the FMDV capsid.
Main Methods:
- Utilized neutralizing monoclonal antibodies (MAbs) against type O FMDV.
- Employed inhibition ELISA techniques with peptide antigens and anti-peptide sera.
- Analyzed MAb binding to isolated VP1 protein and synthetic peptides.
- Mapped critical amino acid residues within VP1 contributing to epitopes.
Main Results:
- Identified distinct conformational sites on FMDV VP1 recognized by neutralizing MAbs.
- Demonstrated that two immunogenic VP1 tracts (residues 143-146 and 200-213) form a single antigenic domain in the virion.
- Pinpointed critical amino acids (e.g., 143, 144, 146, 206, 207) for MAb binding and neutralization.
- Characterized a strain-specific MAb recognizing epitopes within residues 161-180 and 200-213.
Conclusions:
- The VP1 protein of FMDV contains complex antigenic domains formed by spatially proximate linear sequences.
- These findings elucidate the structural basis of FMDV neutralization by MAbs.
- The identified epitopes provide targets for rational FMDV vaccine design.