As the DTT-sensitive m2H2 had previously been mapped to its epitope using linear peptides [21] , we attempted a similar approach to locate the binding epitope of D29 Fab-IgG. An inhibition ELISA was carried out using synthetic ,20 mer linear peptides covering DENV2 prM [25] as well as a library of short 15-mer overlapping linear peptides (Mimotope) corresponding to aa1-166 of prM and aa1-495 of E (Materials and Methods S1). However, none of the linear peptides were able to significantly inhibit the binding of D29 Fab-IgG to DENV2 (Fig. S3) , suggesting that the epitope of D29 Fab-IgG1 is discontinuous. Next, D29 Fab-IgG was screened using a random dodecapeptide (Ph.D-12)-phage library as this approach has previously been used to map antibody-binding motifs [26, 27] . Peptide-phage clones were randomly selected from the second, third and fourth round of panning, and their binding specificity was confirmed by direct binding ELISA against D29 Fab-IgG. Reactive clones were sequenced and checked against a list of common target-unrelated peptides (TUPs) [28] to eliminate peptides that react with constant regions of antibodies, protein A/G sepharose or plastic surfaces. No TUPs were detected and the resulting 20 unique clones fall into three main consensus groups: 26% contained the motif W(TL/SV)K(L/X)PXW; 14% contained the motif AKTMP and 33% contained the motif KXPXW ( Table 1) .