To broadly characterize the epitope of D29 Fab-IgG on DENV, we used competition ELISA with well characterized DENV antibodies including mouse-derived 3H5 (m3H5) which is specific to DENV2 EDIII; m4G2, a cross-reactive antibody that recognizes EDII of all flaviviruses and m2H2, a cross-DENV reactive anti-prM antibody [21, 22] . Making use of humanized versus parental murine antibodies for 3H5 and 4G2, and HRPconjugated m2H2 versus non-conjugated for m2H2, each of the reference antibodies was shown to self-compete ( Fig. 2A) . No significant competition was observed between D29 Fab-IgG and m3H5, m4G2 or non-DENV specific control antibody. However, binding of D29 Fab-IgG to DENV2 decreased significantly in the presence of m2H2 in a dose-dependent manner, indicating that D29 Fab-IgG recognized an epitope on prM similar to that of m2H2 ( Fig. 2A) .