Potent Cross-Serotype Dengue Neutralization with Low ADE by AG-Strand-Targeting Anti-EDIII Antibodies
Napon Nilchan, Anunyaporn Phungsom, Mongkhonphan Tantiwatcharakunthon, Prasit Luangaram, Pattarakul Pakchotanon, Thaneeya Duangchinda, Romchat Kraivong, Tanapan Prommool, Chatchawan Srisawat, Chunya PuttikhuntAbstract
Dengue virus (DENV) envelope protein domain III (EDIII) is a premier target for vaccine design because EDIII-specific antibodies can potently neutralize DENV with a low propensity for inducing antibody-dependent enhancement (ADE). We previously identified a cross-reactive antibody, R3N_2D3, which targets the EDIII AG-strand epitope and neutralizes all four DENV serotypes with low ADE, a desirable combination of activities among anti-DENV antibodies. In this study, we expanded this AG-strand-targeting antibody panel by identifying four additional anti-EDIII antibodies from our dengue-immune single-chain variable fragment (scFv)-phage libraries. Despite variations in their binding footprints, these new antibodies converged on key residues within the AG-strand epitope. When expressed as full IgG1, these candidates showed potent cross-neutralization with subnanomolar focus reduction neutralization titers (FRNT50 values) and consistently low ADE compared to the prototypical fusion-loop antibody 4G2 when tested in an in vitro U937 monocytic cell model. Collectively, these findings demonstrate that the AG-strand epitope can elicit broadly protective antibodies with reduced ADE risk, highlighting its potential as a strategic epitope for pan-DENV vaccine development.