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Nora virus persistent infections are not affected by the RNAi machinery.
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). (Hultmark)
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). (Hultmark)
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). (Hultmark)
2009 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 4, no 5, e5731- p.Article in journal (Refereed) Published
Abstract [en]

Drosophila melanogaster is widely used to decipher the innate immune system in response to various pathogens. The innate immune response towards persistent virus infections is among the least studied in this model system. We recently discovered a picorna-like virus, the Nora virus which gives rise to persistent and essentially symptom-free infections in Drosophila melanogaster. Here, we have used this virus to study the interaction with its host and with some of the known Drosophila antiviral immune pathways. First, we find a striking variability in the course of the infection, even between flies of the same inbred stock. Some flies are able to clear the Nora virus but not others. This phenomenon seems to be threshold-dependent; flies with a high-titer infection establish stable persistent infections, whereas flies with a lower level of infection are able to clear the virus. Surprisingly, we find that both the clearance of low-level Nora virus infections and the stability of persistent infections are unaffected by mutations in the RNAi pathways. Nora virus infections are also unaffected by mutations in the Toll and Jak-Stat pathways. In these respects, the Nora virus differs from other studied Drosophila RNA viruses.

Place, publisher, year, edition, pages
2009. Vol. 4, no 5, e5731- p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:umu:diva-30293DOI: 10.1371/journal.pone.0005731PubMedID: 19478998OAI: oai:DiVA.org:umu-30293DiVA: diva2:281404
Available from: 2009-12-15 Created: 2009-12-15 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Nora virus as a model to study persistent infection in Drosophila melanogaster
Open this publication in new window or tab >>Nora virus as a model to study persistent infection in Drosophila melanogaster
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Drosophila melanogaster has been widely used as a model organism to study the immune responses against bacteria, fungi, parasites and viruses. Here, I present a D. melanogaster virus as a model to study persistent virus infections. I have discovered and characterized the Nora virus, a small picorna-like RNA virus able to persistently infect D. melanogaster. The Nora virus genome encodes four open reading frames; a feature not present in other picorna-like viruses. The Nora virus is not closely related to any other virus family, but rather is the first virus in a new family of picorna-like viruses. The major replicative proteins of this virus are encoded in the second open reading frame and the capsid proteins are encoded in the fourth open reading frame. The sequence of the capsid proteins are not obviously related to any other previously described protein. By looking at expressed sequence tags (EST) projects, we identified an EST sequence from the parasitic wasp Nasonia which appears to encode proteins that have sequence similarity to the Nora virus capsid proteins. I have shown that the Nora virus persists in the fly intestine however I did not observe serious pathological effects in the infected flies. The virus is shed through feces and the transmission occurs horizontally via the ingestion of virus-contaminated food. Moreover, I observed variability in the viral titers among single flies of the same infected stock. Some flies are able to clear the Nora virus but not others and this phenomenon seems to be titer-dependent. Surprisingly, none of the known Drosophila antiviral responses play a role against the Nora virus. In conclusion, my work shows that studying the Nora virus interaction with the Drosophila immune system can lead to new findings on viral persistence mechanisms of RNA viruses and of Drosophila viral innate immunity.

Place, publisher, year, edition, pages
Umeå: Department of molecular biology, 2009. 39 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1265
Keyword
Nora virus, Drosophial, persistence, transmission, RNAi, capsid proteins
National Category
Microbiology in the medical area
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-22129 (URN)978-91-7264-781-7 (ISBN)
Public defence
2009-05-18, Major Groove, Institution för Molekylärbiologi, byggnad 6L, 09:00 (English)
Opponent
Supervisors
Available from: 2009-04-28 Created: 2009-04-23 Last updated: 2011-06-22Bibliographically approved

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Habayeb, Mazen SEkström, Jens-OlaHultmark, Dan
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