title: Identification of specific residues in avian influenza A virus NS1 that enhance viral replication and pathogenicity in mammalian systems.
abstract: Reassortment of their segmented genomes allows influenza A viruses (IAV) to gain new characteristics, which potentially enable them to cross the species barrier and infect new hosts. Improved replication was observed for reassortants of the strictly avian IAV A/FPV/Rostock/34 (FPV, H7N1) containing the NS segment from A/Goose/Guangdong/1/1996 (GD, H5N1), but not for reassortants containing the NS segment of A/Mallard/NL/12/2000 (MA, H7N3). The NS1 of GD and MA differ only in 8 aa positions. Here, we show that efficient replication of FPV-NSMA-derived mutants was linked to the presence of a single substitution (D74N) and more prominently to a triple substitution (P3S+R41K+D74N) in the NS1MA protein. The substitution(s) led to (i) increased virus titres, (ii) larger plaque sizes and (iii) increased levels and faster kinetics of viral mRNA and protein accumulation in mammalian cells. Interestingly, the NS1 substitutions did not affect viral growth characteristics in avian cells. Furthermore, we show that an FPV mutant with N74 in the NS1 (already possessing S3+K41) is able to replicate and cause disease in mice, demonstrating a key role of NS1 in the adaptation of avian IAV to mammalian hosts. Our data suggest that (i) adaptation to mammalian hosts does not necessarily compromise replication in the natural (avian) host and (ii) very few genetic changes may pave the way for zoonotic transmission. The study reinforces the need for close surveillance and characterization of circulating avian IAV to identify genetic signatures that indicate a potential risk for efficient transmission of avian strains to mammalian hosts.
authors.affiliation: Institute of Medical Virology, Justus Liebig University Giessen, Schubertstrasse 81, 35392 Giessen, Germany.
authors.forename: Pumaree
authors.initials: P
authors.lastname: Kanrai
authors.affiliation: Institute of Medical Virology, Justus Liebig University Giessen, Schubertstrasse 81, 35392 Giessen, Germany.|Center of Scientific Excellence for Influenza Viruses, National Research Center (NRC), 12311 Dokki, Giza, Egypt.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Mostafa
authors.affiliation: Institute of Medical Virology, Justus Liebig University Giessen, Schubertstrasse 81, 35392 Giessen, Germany.
authors.forename: Ramakanth
authors.initials: R
authors.lastname: Madhugiri
authors.affiliation: Department of Pharmaceutical Chemistry, Philipps University Marburg, Marbacher Weg 6, 35037 Marburg, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Lechner
authors.affiliation: Department of Infection Genetics, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Wilk
authors.affiliation: Department of Infection Genetics, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Schughart
authors.affiliation: Department of Virology, University of Helsinki, PO Box 21 (Haartmaninkatu 3) 00014, Finland.
authors.forename: Leena
authors.initials: L
authors.lastname: Ylösmäki
authors.affiliation: Department of Virology, University of Helsinki, PO Box 21 (Haartmaninkatu 3) 00014, Finland.
authors.forename: Kalle
authors.initials: K
authors.lastname: Saksela
authors.affiliation: Institute of Medical Virology, Justus Liebig University Giessen, Schubertstrasse 81, 35392 Giessen, Germany.
authors.forename: John
authors.initials: J
authors.lastname: Ziebuhr
authors.affiliation: Institute of Medical Virology, Justus Liebig University Giessen, Schubertstrasse 81, 35392 Giessen, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Pleschka
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D004195:Disease Models, Animal; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000502:physiology*; D008810:Mice, Inbred C57BL; D050505:Mutant Proteins / Q000235:genetics*; D020125:Mutation, Missense; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000821:virology; D017361:Viral Nonstructural Proteins / Q000235:genetics*; D014779:Virus Replication
chemical_list: C085820:INS1 protein, influenza virus; D050505:Mutant Proteins; D017361:Viral Nonstructural Proteins