Abstract
Phage displaying random cyclic 7-mer, and linear 7-mer and 12-mer peptides at the N terminus of the coat protein, pIII, were panned with the murine monoclonal antibody, 9-2-L379 specific for meningococcal lipo-oligosaccharide. Five cyclic peptides with two sequence motifs, six linear 7-mers, and five linear 12-mers with different sequence motifs were identified. Only phage displaying cyclic peptides were specifically captured by and were antigenic for 9-2-L379. Monoclonal antibody 9-2-L379 exhibited "apparent" binding affinities to the cyclic peptides between 11 and 184 nm, comparable with lipo-oligosaccharide. All cyclic peptides competed with the binding of 9-2-L379 to lipo-oligosaccharide with EC(50) values in the range 10-105 microm, which correlated with their apparent binding affinities. Structural modifications of the cyclic peptides eliminated their ability to bind and compete with monoclonal antibody 9-2-L379. Mice (C3H/HeN) immunized with the cyclic peptide with optimal apparent binding affinity and EC(50) of competition elicited cross-reactive antibodies to meningococcal lipo-oligosaccharide with end point dilution serum antibody titers of 3200. Cyclic peptides were converted to T-cell-dependent immunogens without disrupting these properties by C-terminal biotinylation and complexing with NeutrAvidin. The data indicate that constrained peptides can cross-react with a carbohydrate-specific antibody with greater specificity than linear peptides, and critical to this specificity is their structural conformation.
Highlights
Numerous studies have demonstrated that oligopeptides, identified from antigenic regions of antibody idiotype sequences or by direct binding to anti-carbohydrate antibodies, can elicit cross-reactive antibody responses to bacterial polysaccharides [1]
Peptides with a constrained structure would be more likely to depend on conformation as well as chemical interactions to bind to the antibody paratope and act as better conformational mimics that elicit a cross-reactive antibody response to the bacterial glycan structure, whereas the more flexible linear peptides may only adopt a shape on docking to the antibody
In this study we characterized linear and cyclic peptides that cross-react with an antibody specific for a bacterial carbohydrate by phage capture assays, ELISA, measurement of apparent binding affinities, and in-solution competition to assess their specificity
Summary
The coliphage libraries Ph.D 7 (linear 7-mer random peptides), Ph.D 12 (linear 12 mer peptides), and Ph.D C7C (cyclic 7-mer peptides) were purchased from New England Biolabs. All three libraries express random peptides as an N-terminal fusion to coliphage coat protein pIII
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
