PEPTIDE MIMICS OF GROUP B STREPTOCOCCAL CARBOHYDRATE ANTIGENS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Using phage display libraries, peptides were selected that bind to the highly protective monoclonal antibody S9, which binds to the type III capsular polysaccharide of group B streptococcus. The ability of this peptide to be an antigenic mimic and to elicit anti-type III antibodies upon immunization was demonstrated. A secondary phage library allowed the selection of improved mimics. NMR studies have been performed showing the peptide both free in solution and bound by the antibody. Collaborative research with the CCRC aims to further study the structural basis for this mimicry. Fabs of antibodies that bind to both the CPS and peptide are being made. Once they are purified, they will be crystallized, either with or without carbohydrate or peptide antigen, and used for X-ray diffraction analyses.