title: Differential replication properties among H9N2 avian influenza viruses of Eurasian origin.
abstract: Avian influenza H9N2 viruses have become panzootic in Eurasia causing respiratory manifestations, great economic losses and occasionally being transmitted to humans. To evaluate the replication properties and compare the different virus quantification methods, four Eurasian H9N2 viruses from different geographical origins were propagated in embryonated chicken egg (ECE) and Madin-Darby canine kidney epithelial cell systems. The ECE-grown and cell culture-grown viruses were monitored for replication kinetics based on tissue culture infectious dose (TCID50), Hemagglutination (HA) test and quantitative real time RT-PCR (qRT-PCR). The cellular morphology was analyzed using immunofluorescence (IF) and cellular ELISA was used to screen the sensitivity of the viruses to amantadine. The Eurasian wild type-H9N2 virus produced lower titers compared to the three G1-H9N2 viruses at respective time points. Detectable titers were observed earliest at 16 h post inoculation (hpi), significant morphological changes on cells were first observed at 32 hpi. Few nucleotide and amino acid substitutions were noticed in the HA, NA and NS gene sequences but none of them are related to the known conserved region that can alter pathogenesis or virulence following a single passage in cell culture. All studied H9N2 viruses were sensitive to amantadine. The G1-H9N2 viruses have higher replication capabilities compared to the European wild bird-H9N2 probably due to their specific genetic constitutions which is prerequisite for a successful vaccine candidate. Both the ECE and MDCK cell system allowed efficient replication but the ECE system is considered as the better cultivation system for H9N2 viruses in order to get maximum amounts of virus within a short time period.
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. parvin.rokshana@vetmed.uni-leipzig.de.|Department of Pathology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh. parvin.rokshana@vetmed.uni-leipzig.de.
authors.forename: Rokshana
authors.initials: R
authors.lastname: Parvin
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. shehata@vetmed.uni-leipzig.de.|Avian and Rabbit Diseases Department, Faculty of Veterinary Medicine, University of Sadat City, Sadat City, Egypt. shehata@vetmed.uni-leipzig.de.
authors.forename: Awad A
authors.initials: AA
authors.lastname: Shehata
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. kristin.heenemann@vetmed.uni-leipzig.de.
authors.forename: Kristin
authors.initials: K
authors.lastname: Heenemann
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. Malgorzata.Gac@vetmed.uni-leipzig.de.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Gac
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. antje.rueckner@vetmed.uni-leipzig.de.
authors.forename: Antje
authors.initials: A
authors.lastname: Rueckner
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. halami@vetmed.uni-leipzig.de.
authors.forename: Mohammad Y
authors.initials: MY
authors.lastname: Halami
authors.affiliation: Institute of Virology, Center for Infectious Diseases, Faculty of Veterinary Medicine, University of Leipzig, 04109, Leipzig, Saxony, Germany. thomas.vahlenkamp@uni-leipzig.de.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Vahlenkamp
mesh_terms: D000547:Amantadine / Q000494:pharmacology; D019943:Amino Acid Substitution; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology; D002642:Chick Embryo; D004285:Dogs; D006386:Hemagglutination Tests / Q000662:veterinary*; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D061985:Madin Darby Canine Kidney Cells; D009154:Mutation; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary*; D014779:Virus Replication / Q000187:drug effects
chemical_list: D000998:Antiviral Agents; D000547:Amantadine