Initial Studies of the Molecular Basis of Peptide Mimicry of Group B Streptococcal Type III Capsular Polysaccharide

Abstract

We have previously shown that the peptide FDTGAFDPDWPA is a mimetic of the group B streptococcal type III capsular polysaccharide (CPSm). It binds to anti-CPSm antibodies and can be used to immunize mice and produce anti-CPSm. In this paper we investigate the molecular mechanisms underlying this peptide-carbohydrate mimicry in two ways. First, we have examined the conformation of the peptide by NMR spectroscopy in water. Next, we have produced monoclonal anti-peptide and anti-CPS_III antibodies, compared their fine specificity, and have sequenced them. The results indicate that the peptide assumes a conformation that may be similar to that of the CPS_III in solution and that the peptide and CPS_III elicit an overlapping repertoire of antibodies.