Insertion of a multibasic cleavage motif into the hemagglutinin of a low-pathogenic avian influenza H6N1 virus induces a highly pathogenic phenotype.
The highly pathogenic avian influenza (HPAI) virus phenotype is restricted to influenza A viruses of the H5 and H7 hemagglutinin (HA) subtypes. To obtain more information on the apparent subtype-specific nature of the HPAI virus phenotype, a low-pathogenic avian influenza (LPAI) H6N1 virus was generated, containing an HPAI H5 RRRKKR [downward arrow] G multibasic cleavage site (MBCS) motif in HA (the downward arrow indicates the site of cleavage). This insertion converted the LPAI virus phenotype into an HPAI virus phenotype in vitro and in vivo. The H6N1 virus with an MBCS displayed in vitro characteristics similar to those of HPAI H5 viruses, such as cleavage of HA(0) (the HA protein of influenza A virus initially synthesized as a single polypeptide precursor) and virus replication in the absence of exogenous trypsin. Studies of chickens confirmed the HPAI phenotype of the H6N1 virus with an MBCS, with an intravenous pathogenicity index of 1.4 and systemic virus replication upon intranasal inoculation, the hallmarks of HPAI viruses. This study provides evidence that the subtype-specific nature of the emergence of HPAI viruses is not at the molecular, structural, or functional level, since the introduction of an MBCS resulted in a fully functional virus with an HPAI virus genotype and phenotype.
Department of Virology, Erasmus Medical Center, PO Box 2040, Rotterdam, Netherlands. vincent.munster@nih.gov
Vincent J
VJ
Munster
Eefje J A
EJ
Schrauwen
Emmie
E
de Wit
Judith M A
JM
van den Brand
Theo M
TM
Bestebroer
Sander
S
Herfst
Guus F
GF
Rimmelzwaan
Albert D M E
AD
Osterhaus
Ron A M
RA
Fouchier
D000825:Animal Structures / Q000821:virology; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens; D004285:Dogs; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000502:physiology*; D007150:Immunohistochemistry; D009980:Influenza A virus / Q000235:genetics / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000473:pathology / Q000821:virology; D008853:Microscopy; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011201:Poultry Diseases / Q000473:pathology / Q000821:virology; D012367:RNA, Viral / Q000235:genetics; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D019562:Viral Load; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D037521:Virulence Factors