Deletion of accessory genes 3a, 3b, 5a or 5b from avian coronavirus infectious bronchitis virus induces an attenuated phenotype both in vitro and in vivo

Andrea Laconi, Steven J van Beurden, Alinda J Berends, Annika Krämer-Kühl, Christine A Jansen, Dieuwertje Spekreijse, Gilles Chénard, Hans-Christian Philipp, Egbert Mundt, Peter J M Rottier, M Hélène Verheije

    Research output: Contribution to journalArticleAcademicpeer-review

    Abstract

    Avian coronavirus infectious bronchitis virus (IBV) infects domestic fowl, resulting in respiratory disease and causing serious losses in unprotected birds. Its control is mainly achieved by using live attenuated vaccines. Here we explored the possibilities for rationally attenuating IBV to improve our knowledge regarding the function of IBV accessory proteins and for the development of next-generation vaccines with the recently established reverse genetic system for IBV H52 based on targeted RNA recombination and selection of recombinant viruses in embryonated eggs. To this aim, we selectively removed accessory genes 3a, 3b, 5a and 5b individually, and rescued the resulting recombinant (r) rIBV-Δ3a, rIBV-Δ3b, rIBV-Δ5a and rIBV-Δ5b. In vitro inoculation of chicken embryo kidney cells with recombinant and wild-type viruses demonstrated that the accessory protein 5b is involved in the delayed activation of the interferon response of the host after IBV infection. Embryo mortality after the inoculation of 8-day-old embryonated chicken eggs with recombinant and wild-type viruses showed that rIBV-Δ3b, rIBV-Δ5a and rIBV-Δ5b had an attenuated phenotype in ovo, with reduced titres at 6 h p.i. and 12 h p.i. for all viruses, while growing to the same titre as wild-type rIBV at 48 h p.i. When administered to 1-day-old chickens, rIBV-Δ3a, rIBV-Δ3b, rIBV-Δ5a and rIBV-Δ5b showed reduced ciliostasis in comparison to the wild-type viruses. In conclusion, individual deletion of accessory genes in IBV H52 resulted in mutant viruses with an attenuated phenotype.

    Original languageEnglish
    Pages (from-to)1381-1390
    JournalJournal of General Virology
    Volume99
    Issue number10
    DOIs
    Publication statusPublished - 1 Aug 2018

    Keywords

    • Coronavirus
    • live attenuated virus
    • infectious bronchitis virus
    • chicken
    • accessory proteins
    • accessory genes

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