title: The critical cut-off temperature of avian influenza viruses.
abstract: We have measured the pathogenicity for 6-week-old chicks of infection by H7 avian influenza viruses. One virus, strain S3 from A/FPV/Rostock/34(H7N1) showed a temperature sensitive phenotype at 41.5 degrees C and reduced pathogenicity. By analysis of reassortants made between virus S3 and A/FPV/Dobson/27(H7N7), a fully pathogenic virus, two conclusions arise. (1) The critical cut-off temperature for avian influenza virus in 6-week-old chicks is 41.5 degrees. (2) RNA segment 1 of virus S3 is responsible for the lack of pathogenicity in reassortant viruses. Nucleotide sequencing of RNA segment 1 from S3 and its parent, A/FPV/Rostock/34 has revealed a single mutation at nucleotide 1561. This results in a substitution of isoleucine for leucine at amino acid position 512 in the cap-binding protein, PB2.
authors.affiliation: Division of Molecular Biology, AFRC Institute for Animal Health, Pirbright Laboratory, Nr. Woking, Surrey, U.K.
authors.forename: J W
authors.initials: JW
authors.lastname: McCauley
authors.forename: C R
authors.initials: CR
authors.lastname: Penn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002645:Chickens; D009980:Influenza A virus / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000382:microbiology*; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics; D013696:Temperature; D010948:Viral Plaque Assay
chemical_list: D002352:Carrier Proteins; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D012367:RNA, Viral