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Abstract The receptor-binding site of influenza A virus hemagglutinin partially overlaps with major antigenic sites and constantly evolves. In this study, we observe that mutations G186D and D190N in the hemagglutinin receptor-binding site have coevolved in two recent human H3N2 clades. X-ray crystallography results show that these mutations coordinately drive the evolution of the hemagglutinin receptor binding mode. Epistasis between G186D and D190N is further demonstrated by glycan binding and thermostability analyses. Immunization and neutralization experiments using mouse and human samples indicate that the evolution of receptor binding mode is accompanied by a change in antigenicity. Besides, combinatorial mutagenesis reveals that G186D and D190N, along with other natural mutations in recent H3N2 strains, alter the compatibility with a common egg-adaptive mutation in seasonal influenza vaccines. Overall, our findings elucidate the role of epistasis in shaping the recent evolution of human H3N2 hemagglutinin and substantiate the high evolvability of its receptor-binding mode.

Lei et al. systematically characterized the epistasis among natural mutations in the neuraminidase of human influenza H3N2 virus, which provide insights into the biophysical constraints that shaped its evolution trajectory over the past half-century.

The success of HER2-targeted cancer therapy is limited by treatment resistance. Here, the authors engineer an anti-HER2 biparatopic antibody with multiple mechanisms of action including induction of HER2 clustering to trigger complement dependent cytotoxicity, signal inhibition, antibody dependent cellular cytotoxicity and phagocytosis.