E57R-G, E129V-A, E131Q-G) and M5/6 (E129V-A, E131Q-G, E133E-G, E134N-G) (Fig. 6A ). Both control antibodies were able detect their respective protein targets for all mutants, apart from Figure 5 . Localization of P3 and P9 peptide sequence on 3D crystal structure of prM-E heterodimer (PDB 3C6E). P3 (Purple) and P9 (green) peptide sequences were aligned with the predicted clusters (Cluster 1 -Navy blue; Cluster 2 -Black) on the prM-E crystal structure. The path of peptide phage sequences was highlighted with the participating residues from the cluster and the peptide phage labeled. Matched residues were purple (P3) or green (P9) and numbered accordingly; mis-matched residues were grey. The respective proteins and domains were highlighted as above. doi:10.1371/journal.pone.0033451.g005 M3/4 and M4/5 which appeared to be non-viable (Fig. 6B) . The binding of h4G2 to E of M4 also appeared to be affected by the mutation introduced (Fig. 6B) ; likely to be caused by a change of local conformation, rather than a drop of expression level since prM-binding by m2H2 was normal. Notably, the binding of D29 Fab-IgG to the E protein of the M3, M5 and M6 mutants were severely affected; in particular, D29 Fab-IgG failed to detect E of M4 and M5/6, whereas binding of prM for all these mutants was not affected at all (Fig. 6B ). Together these results confirm the epitopes identified through peptide-phage display.