The conserved bridging domain on HCV E1E2 glycoprotein complex is targeted by neutralizing antibodies from diverse lineages

Chen, F.; Nguyen, Y. T. K.; Lee, Y.-Z.; Giang, E.; Lau, S. C.; Koide, Y.; Hung, S.-H.; Ueno, L.; He, L.; Fuerst, T. R.; Lauer, G. M.; Stanfield, R. L.; Zhu, J.; Wilson, I. A.; Law, M.

doi:10.1101/2025.11.05.686883

bioRxiv · 10.1101/2025.11.05.686883

The conserved bridging domain on HCV E1E2 glycoprotein complex is targeted by neutralizing antibodies from diverse lineages

Chen, F.·Nguyen, Y. T. K.·Lee, Y.-Z.·Giang, E.·Lau, S. C.·Koide, Y.·Hung, S.-H.·Ueno, L.·He, L.·Fuerst, T. R.·Lauer, G. M.·Stanfield, R. L.·Zhu, J.·Wilson, I. A.·Law, M.

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Abstract

The induction of potent and cross-reactive neutralizing antibody (nAb) responses remains a challenge in vaccine development against antigenically diverse viruses such as hepatitis C virus (HCV). The HCV E1E2 glycoprotein complex contains two major neutralizing sites: the neutralizing face (NF) and the less explored bridging domain (BD). Here, we characterized 25 BD-targeting nAbs isolated from infection or immunization. These antibodies arise from diverse B cell lineages but share convergent CDRH3 features. Epitope mapping by alanine scanning and negative-stain electron microscopy revealed overlapping epitopes on BD spanning antigenic regions AR4 and AR5, with variable back layer engagement. The crystal structure of a non-human primate BD nAb RM3-26 in complex with E2 uncovered a back layer-directed recognition mode analogous to that of the human nAb hcab40. Together, BD- and NF-directed nAbs exhibited additivity in their neutralization, highlighting BD as a conserved site of vulnerability on HCV and a valuable target for rational vaccine design.

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Chen, F., Nguyen, Y. T. K., Lee, Y.-Z., Giang, E., Lau, S. C., Koide, Y., Hung, S.-H., Ueno, L., He, L., Fuerst, T. R., Lauer, G. M., Stanfield, R. L., Zhu, J., Wilson, I. A., Law, M.. 2025-11-07. The conserved bridging domain on HCV E1E2 glycoprotein complex is targeted by neutralizing antibodies from diverse lineages. https://doi.org/10.1101/2025.11.05.686883

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