Phenotypic Effects of Substitutions within the Receptor Binding Site of Highly Pathogenic Avian Influenza H5N1 Virus Observed during Human Infection
Dirk Eggink, Monique I. Spronken, Roosmarijn van der Woude, Jocynthe Buzink, Frederik Broszeit, Ryan McBride, Hana Apsari Pawestri, Vivi Setiawaty, James C. Paulson, Geert‐Jan Boons, Ron A. M. Fouchier, Colin A. Russell, M.C.M. de Jong, Robert P. de Vries
Abstract
H5 viruses continue to be a threat for public health. Because these viruses are immunologically novel to humans, they could spark a pandemic when adapted to transmit between humans. Avian influenza viruses need several adaptive mutations to bind to human-type receptors, increase hemagglutinin (HA) stability, and replicate in human cells. However, knowledge on adaptive mutations during human infections is limited. A previous study showed substantial diversity within the receptor binding site of H5N1 during human infection. We therefore analyzed the observed amino acid changes phenotypically in a diverse set of assays, including virus replication, stability, and receptor specificity. None of the tested substitutions resulted in a clear step toward a human-adapted virus capable of aerosol transmission. It is notable that acquiring human-type receptor specificity needs multiple amino acid mutations, and that variability at key position 226 is not tolerated, reducing the risk of them being acquired naturally.