Initial studies of the molecular basis of peptide mimicry of group B streptococcal type III capsular polysaccharide.

We have previously shown that the peptide FDTGAFDPDWPA is a mimetic of the group B streptococcal type III capsular polysaccharide (CPS(III)). It binds to anti-CPS(III) antibodies and can be used to immunize mice and produce anti-CPS(III). 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.