title: Proteolytic enzymes in embryonated chicken eggs sustain the replication of egg-grown low-pathogenicity avian influenza viruses in cells in the absence of exogenous proteases.
abstract: Low pathogenic influenza viruses grow readily in embryonated chicken eggs but require the addition of exogenous proteases to grow in MDCK cell culture. In this study, we found that the influenza viruses propagated previously in eggs, can grow for up to two passages in cell culture without the addition of exogenous proteolytic enzymes. These results indicate that the reason for virus propagation in cells during the first two passages may be due to proteases from egg allantoic fluid carried over from egg culture. The ability of influenza viruses to grow in cells in the absence of trypsin is currently considered as a hallmark of highly pathogenic influenza viruses. Our data indicate that differentiating between high and low pathogenicity using cell culture only is not appropriate and other indicators such as sequence analysis and in vitro pathogenicity index should be performed.
authors.affiliation: Environmental Research Division, National Research Centre, Dokki 12311, Giza, Egypt.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Kandeil
authors.affiliation: Environmental Research Division, National Research Centre, Dokki 12311, Giza, Egypt.
authors.forename: Ola
authors.initials: O
authors.lastname: Bagato
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
authors.forename: Hassan
authors.initials: H
authors.lastname: Zaraket
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Debeauchamp
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
authors.forename: Scott
authors.initials: S
authors.lastname: Krauss
authors.affiliation: Environmental Research Division, National Research Centre, Dokki 12311, Giza, Egypt.
authors.forename: Rabeh
authors.initials: R
authors.lastname: El-Shesheny
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Webby
authors.affiliation: Environmental Research Division, National Research Centre, Dokki 12311, Giza, Egypt.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Ali
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, United States. Electronic address: ghazi.kayali@stjude.org.
authors.forename: Ghazi
authors.initials: G
authors.lastname: Kayali
mesh_terms: D000818:Animals; D002460:Cell Line; D002645:Chickens; D004285:Dogs; D009980:Influenza A virus / Q000145:classification / Q000254:growth & development* / Q000472:pathogenicity / Q000502:physiology; D005585:Influenza in Birds / Q000821:virology; D010447:Peptide Hydrolases / Q000378:metabolism*; D014774:Virulence; D014776:Virus Cultivation / Q000379:methods; D014779:Virus Replication; D015053:Zygote / Q000201:enzymology* / Q000821:virology*
chemical_list: D010447:Peptide Hydrolases
keywords: Cell culture; Influenza; Protease