A rAb screening method for improving the probability of identifying peptide mimotopes of carbohydrate antigens

Peptide mimotopes have been investigated as surrogate antigens of carbohydrate (CHO) targets on pathogen and tumor cells in vaccine and therapeutic discovery. One of the main bottlenecks in peptide mimotope discovery is the inability of initial screening regimes to differentiate between true mimotopes and non-mimotopes. As a result, subsequent in vivo analysis of putative peptide mimotopes is often inefficient requiring the use of experimental animals during a lengthy in vivo immunization process. Here, we demonstrate a rapid preliminary screening method to identify putative mimotopes using a recombinant antibody (rAb) library, which may increase the probability of identifying peptides that will elicit a CHO-cross-reactive response in vivo. A human naïve rAb library was screened against both an established peptide mimotope and a non-mimotope of the Group B Streptococcus (GBS) type III polysaccharide to determine if selected antibodies cross-reacted with the original GBS polysaccharide. We were able to differentiate between these two peptides because peptide-binding Abs that cross-reacted to GBS was isolated only with the peptide mimotope. We discuss the feasibility of using this method to significantly increase the breadth of screening and reduce the discovery time for peptide mimotopes.