The present invention relates to an anti-idiotypic polypeptide scaffold that includes two or more peptide sequences that mimic a discontinuous epitope of a pathogen that is recognized by or induces formation of a broadly neutralizing antibody. Using a fibronectin FNfn10 scaffold bearing two or more modified discontinuous loops, scaffolds that recognize broadly neutralizing antibodies in vitro and from patient serum have been identified. These scaffolds should induce an immune response or mobilize germline specificities to initiate their affinity maturation.
