Since 2013, H7N9 avian influenza viruses (AIVs) have caused more than 1,600 human infections, posing a threat to public health. An emerging concern is whether H7N9 AIVs will cause pandemics among humans. Molecular analysis of hemagglutinin (HA), which is a critical determinant of interspecies transmission, shows that the current H7N9 AIVs are still dual-receptor tropic, indicating limited human-to-human transmission potency ...
Since 2013, H7N9 avian influenza viruses (AIVs) have caused more than 1,600 human infections, posing a threat to public health. An emerging concern is whether H7N9 AIVs will cause pandemics among humans. Molecular analysis of hemagglutinin (HA), which is a critical determinant of interspecies transmission, shows that the current H7N9 AIVs are still dual-receptor tropic, indicating limited human-to-human transmission potency. Mutagenesis and structural studies reveal that a G186V substitution is sufficient for H7N9 AIVs to acquire human receptor-binding capacity, and a Q226L substitution would favor binding to both avian and human receptors only when paired with A138/V186/P221 hydrophobic residues. These data suggest a different evolutionary route of H7N9 viruses compared to other AIV-subtype HAs.
Organizational Affiliation: 
School of Life Sciences, University of Science and Technology of China, Hefei 230026, China; CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing 100101, China; Research Network of Immunity and Health (RNIH), Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing 100101, China; Laboratory of Animal Infectious Diseases, College of Animal Sciences and Veterinary Medicine, Guangxi University, Nanning 530004, China; Laboratory of Protein Engineering and Vaccines, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China; Center for Influenza Research and Early-Warning, Chinese Academy of Sciences (CASCIRE), Beijing 100101, China; Savaid Medical School, University of Chinese Academy of Sciences, Beijing 101408, China; Shenzhen Key Laboratory of Pathogen and Immunity, Shenzhen Third People's Hospital, Shenzhen 518112, China. Electronic address: gaof@im.ac.cn.