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 104 and 1010 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.
ÅslingB.,
DushayM. S.,
HultmarkD.1995; Identification of early genes in the Drosophila immune response by PCR-based differential display: the Attacin A gene and the evolution of attacin-like proteins. Insect Biochem Mol Biol 25:511–518[CrossRef]
BrunG.,
PlusN.1980; The viruses of Drosophila
. In The Genetics and Biology of Drosophila pp 625–702 Edited by
AshburnerM.,
WrightT. R. F.
London: Academic Press;
CalvezV.,
PelletierI.,
BorzakianS.,
Colbère-GarapinF.1993; Identification of a region of the poliovirus genome involved in persistent infection of HEp-2 cells. J Virol 67:4432–4435
DostertC.,
JouanguyE.,
IrvingP.,
TroxlerL.,
Galiana-ArnouxD.,
HetruC.,
HoffmannJ. A.,
ImlerJ.-L.2005; The Jak-STAT signaling pathway is required but not sufficient for the antiviral response of Drosophila
. Nat Immunol 6:946–953[CrossRef]
HamiltonB. A.,
PalazzoloM. J.,
ChangJ. H.,
VijayRaghavanK.,
MayedaC. A.,
WhitneyM. A.,
MeyerowitzE. M.1991; Large scale screen for transposon insertions into cloned genes. Proc Natl Acad Sci U S A 88:2731–2735[CrossRef]
HedengrenM.,
ÅslingB.,
DushayM. S.,
AndoI.,
EkengrenS.,
WihlborgM.,
HultmarkD.1999; Relish , a central factor in the control of humoral, but not cellular immunity in Drosophila
. Mol Cell 4:827–837[CrossRef]
JiangX.,
EstesM. K.,
MetcalfT. G.1987; Detection of hepatitis A virus by hybridization with single-stranded RNA probes. Appl Environ Microbiol 53:2487–2495
JohnsonK. N.,
ChristianP. D.1998; The novel genome organization of the insect picorna-like virus Drosophila C virus suggests this virus belongs to a previously undescribed virus family. J Gen Virol 79:191–203
KimA.,
TerzianC.,
SantamariaP.,
PélissonA.,
Prud'hommeN.,
BuchetonA.1994; Retroviruses in invertebrates: the gypsy retrotransposon is apparently an infectious retrovirus of Drosophila melanogaster
. Proc Natl Acad Sci U S A 91:1285–1289[CrossRef]
KlingelK.,
HohenadlC.,
CanuA.,
AlbrechtM.,
SeemannM.,
MallG.,
KandolfR.1992; Ongoing enterovirus-induced myocarditis is associated with persistent heart muscle infection: quantitative analysis of virus replication, tissue damage, and inflammation. Proc Natl Acad Sci U S A 89:314–318[CrossRef]
KroghA.,
LarssonB.,
von HeijneG.,
SonnhammerE. L. L.2001; Predicting transmembrane protein topology with a hidden Markov model: application to complete genomes. J Mol Biol 305:567–580[CrossRef]
KylstenP.,
SamakovlisC.,
HultmarkD.1990; The cecropin locus in Drosophila ; a compact gene cluster involved in the response to infection. EMBO J 9:217–224
Landès-DevauchelleC.,
BrasF.,
DezéléeS.,
TeningesD.1995; Gene 2 of the sigma rhabdovirus genome encodes the P protein, and gene 3 encodes a protein related to the reverse transcriptase of retroelements. Virology 213:300–312[CrossRef]
PelletierI.,
DuncanG.,
PavioN.,
Colbère-GarapinF.1998; Molecular mechanisms of poliovirus persistence: key role of capsid determinants during the establishment phase. Cell Mol Life Sci 54:1385–1402[CrossRef]
TångrotJ.,
WangL.,
KågströmB.,
SauerU.2006; FISH – family identification of sequence homologues using structure anchored hidden Markov models. Nucleic Acids Res 34: (web server issue), W10–W14 [CrossRef]
ZambonR. A.,
NandakumarM.,
VakhariaV. N.,
WuL. P.2005; The Toll pathway is important for an antiviral response in Drosophila
. Proc Natl Acad Sci U S A 102:7257–7262[CrossRef]