Mutations of an antibody binding energy hot spot on domain III of the dengue 2 envelope glycoprotein exploited for neutralization escape

Previous crystallographic studies have identified a total of 11 DENV-2 envelope protein domain III (ED3) residues (K305, F306, K307, V308, V309, K310, I312, Q325, P364, K388, and N390) that interacted, through both side- and main-chain contacts, with the Fab of a dengue virus (DENV) subcomplex-specific neutralizing monoclonal antibody (MAb) 1A1D-2 (Lok et al., 2008). Here, we used DENV-2 recombinant ED3 mutants of the MAb 1A1D-2 structural epitope residues to determine the functional epitope of this MAb. The side-chains of residues K307, K310 and I312 were determined to be functionally critical for MAb binding, and thus constitute a hot spot of binding energy for MAb 1A1D-2 on the DENV-2 ED3. Overall, these findings demonstrate that only a subset of the amino acid residue side-chains within the structural epitope of MAb 1A1D-2 define a functional epitope on the DENV-2 ED3 that is essential for MAb binding and neutralization escape.