umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Nora virus as a model to study persistent infection in Drosophila melanogaster
Molecular Biology. (Dan Hultmark)
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 [en]
Nora virus, Drosophial, persistence, transmission, RNAi, capsid proteins
National Category
Microbiology in the medical area
Research subject
Molecular Biology
Identifiers
URN: urn:nbn:se:umu:diva-22129ISBN: 978-91-7264-781-7 (print)OAI: oai:DiVA.org:umu-22129DiVA: diva2:212780
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
List of papers
1. Nora virus, a persistent virus in Drosophila, defines a new picorna-like virus family.
Open this publication in new window or tab >>Nora virus, a persistent virus in Drosophila, defines a new picorna-like virus family.
2006 (English)In: Journal of General Virology, ISSN 0022-1317, E-ISSN 1465-2099, Vol. 87, no Pt 10, 3045-3051 p.Article in journal (Refereed) Published
Abstract [en]

Several viruses, including picornaviruses, are known to establish persistent infections, but the mechanisms involved are poorly understood. Here, a novel picorna-like virus, Nora virus, which causes a persistent infection in Drosophila melanogaster, is described. It has a single-stranded, positive-sense genomic RNA of 11879 nt, followed by a poly(A) tail. Unlike other picorna-like viruses, the genome has four open reading frames (ORFs). One ORF encodes a picornavirus-like cassette of proteins for virus replication, including an iflavirus-like RNA-dependent RNA polymerase and a helicase that is related to those of mammalian picornaviruses. The three other ORFs are not closely related to any previously described viral sequences. The unusual sequence and genome organization in Nora virus suggest that it belongs to a new family of picorna-like viruses. Surprisingly, Nora virus could be detected in all tested D. melanogaster laboratory stocks, as well as in wild-caught material. The viral titres varied enormously, between 10(4) and 10(10) viral genomes per fly in different stocks, without causing obvious pathological effects. The virus was also found in Drosophila simulans, a close relative of D. melanogaster, but not in more distantly related Drosophila species. It will now be possible to use Drosophila genetics to study the factors that control this persistent infection.

Keyword
Animals, Drosophila/*virology, Molecular Sequence Data, Phylogeny, Polymerase Chain Reaction, RNA Viruses/*classification/isolation & purification/*physiology, RNA; Viral/chemistry/classification/genetics
Identifiers
urn:nbn:se:umu:diva-17048 (URN)10.1099/vir.0.81997-0 (DOI)16963764 (PubMedID)
Available from: 2007-10-28 Created: 2007-10-28 Last updated: 2017-12-14Bibliographically approved
2. Drosophila Nora virus capsid proteins differ from those of other picorna-like viruses
Open this publication in new window or tab >>Drosophila Nora virus capsid proteins differ from those of other picorna-like viruses
Show others...
2011 (English)In: Virus Research, ISSN 0168-1702, E-ISSN 1872-7492, Vol. 160, no 1-2, 51-58 p.Article in journal (Refereed) Published
Abstract [en]

The recently discovered Nora virus from Drosophila melanogaster is a single-stranded RNA virus. Its published genomic sequence encodes a typical picorna-like cassette of replicative enzymes, but no capsid proteins similar to those in other picorna-like viruses. We have now done additional sequencing at the termini of the viral genome, extending it by 455 nucleotides at the 5' end, but no more coding sequence was found. The completeness of the final 12,333-nucleotide sequence was verified by the production of infectious virus from the cloned genome. To identify the capsid proteins, we purified Nora virus particles and analyzed their proteins by mass spectrometry. Our results show that the capsid is built from three major proteins, VP4A, B and C, encoded in the fourth open reading frame of the viral genome. The viral particles also contain traces of a protein from the third open reading frame, VP3. VP4A and B are not closely related to other picorna-like virus capsid proteins in sequence, but may form similar jelly roll folds. VP4C differs from the others and is predicted to have an essentially α-helical conformation. In a related virus, identified from EST database sequences from Nasonia parasitoid wasps, VP4C is encoded in a separate open reading frame, separated from VP4A and B by a frame-shift. This opens a possibility that VP4C is produced in non-equimolar quantities. Altogether, our results suggest that the Nora virus capsid has a different protein organization compared to the order Picornavirales.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2011
Keyword
RNA viruses, Picornavirales, Insect viruses, Capsid protein organization
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:umu:diva-45033 (URN)10.1016/j.virusres.2011.05.006 (DOI)21605604 (PubMedID)
Note
Available online 13 May 2011 Available from: 2011-06-22 Created: 2011-06-20 Last updated: 2017-12-11Bibliographically approved
3. The Drosophila Nora virus is an enteric virus, transmitted via feces
Open this publication in new window or tab >>The Drosophila Nora virus is an enteric virus, transmitted via feces
Show others...
2009 (English)In: Journal of Invertebrate Pathology, ISSN 0022-2011, E-ISSN 1096-0805, Vol. 101, 29-33 p.Article in journal (Refereed) Published
Abstract [en]

 The biology of the Drosophila viruses has not been intensely investigated. Here we have investigated the biology of the Nora virus, a persistent Drosophila virus. We find that injected Nora virus is able to replicate in the files, reaching a high titer that is maintained in the next generation. There is a remarkable variation in the viral loads of individual flies in persistently infected stocks; the titers can differ by three orders of magnitude. The Nora virus is mainly found in the intestine of infected flies, and the histology of these infected intestines show increased vacuolization. The virus is excreted in the feces and is horizontally transmitted. The Nora virus infection has a very mild effect on the longevity of the flies, and no significant effect on the number of eggs laid and the percent of eggs that develop to adults.

Keyword
Drosophila, Nora virus, Horizontal transmission, Enteric virus, Picorna-like virus
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-22146 (URN)10.1016/j.jip.2009.02.003 (DOI)
Available from: 2009-04-24 Created: 2009-04-24 Last updated: 2017-12-13Bibliographically approved
4. Nora virus persistent infections are not affected by the RNAi machinery.
Open this publication in new window or tab >>Nora virus persistent infections are not affected by the RNAi machinery.
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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-30293 (URN)10.1371/journal.pone.0005731 (DOI)19478998 (PubMedID)
Available from: 2009-12-15 Created: 2009-12-15 Last updated: 2017-12-12Bibliographically approved

Open Access in DiVA

fulltext(997 kB)1092 downloads
File information
File name FULLTEXT01.pdfFile size 997 kBChecksum SHA-512
260f599a7add148f4ac915c3267263096d2837be9dd708e3e541746293166689478f6827934dffbb2842bd1ba03f63f4e0e21ebf0be82efe0015953fd9f6bdfd
Type fulltextMimetype application/pdf

Microbiology in the medical area

Search outside of DiVA

GoogleGoogle Scholar
Total: 1092 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 263 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf