Short communicationMolecular detection of murine noroviruses in laboratory and wild mice☆
Introduction
The Norovirus genus of the Caliciviridae family contains both human and animal pathogens and is further subdivided into five genogroups (GI–V), from which GV represents the murine NoVs (MNV). The ∼7.5 kb positive sense, single stranded norovirus RNA genome is organized into three major open reading frames (ORF): ORF1 encodes a large polyprotein that is cleaved to individual non-structural proteins; ORF2 encodes the viral capsid protein (VP1); and ORF3 encodes a minor structural protein (VP2). In the MNV genome, an additional ORF4 has also been identified (Thackray et al., 2007). Since the discovery of the first MNV in 2003 (Karst et al., 2003) it became evident that MNV infection is the most prevalent viral infection in laboratory mice (Hsu et al., 2005, Kim et al., 2011, Perdue et al., 2007). MNV infection in immunocompetent mice is subclinical but in impaired mice such as STAT1−/−, MNV establishes systemic infection that leads to high mortality (Karst et al., 2003). Due to its ability to grow in tissue culture, MNV became the most widely used surrogate model for human norovirus research (Wobus et al., 2006). All MNV strains isolated from laboratory mice worldwide belong to a single genotype with ∼13% nt and ∼7% aa diversity in the ORF2 (VP1) region indicating a very limited genetic diversity compared to the genetic diversity observed among human noroviruses (Thackray et al., 2007). Recent studies, by either serology or molecular detection suggest that MNVs are also circulating in wild rodents (Parker et al., 2009, Smith et al., 2012). However, the extent of their genetic diversity and biological similarities to MNVs is not well established. In this study, wild and laboratory mice were screened for MNVs, and two novel MNVs from striped field mice (Apodemus agrarius) were identified and characterized.
Section snippets
Sample collection
Thirty striped field mice (A. agrarius), 70 yellow-necked mice (Apodemus flavicollis), and 3 bank voles (Myodes glareolus) were live trapped between July and October 2010 in South-West Hungary. Two pellets collected from each of 10 individual animals of the same Apodemus species were mixed together and made into 20% suspensions in RPMI-1640, yielding 3 striped field mice and 7 yellow-necked mice sample pools. The bank vole samples were processed individually. In addition 121 stool samples were
Results
None of the wild mice samples yielded calicivirus specific amplicon with the generic P289/P290 primers. When tested with the MNV specific primers, 2 of the 3 striped field mice (A. agrarius) samples and 10 of the 41 laboratory mouse samples yielded RT-PCR amplicons, while the yellow-necked mouse (A. flavicollis) and bank vole (M. glareolus) samples remained negative. Phylogenetic analysis of the 356 nt (without the primers) long amplicons revealed that all laboratory mouse MNVs detected in this
Discussion
Until very recently MNVs were only described in laboratory mice and with limited genetic diversity compared to other noroviruses, either indicating a recent introduction of MNVs to mouse (Mus musculus) and/or limited evolutionary pressure on MNVs compared to noroviruses of other hosts. In 2010, we initiated a study for the molecular detection of caliciviruses in stool samples of wild and laboratory rodents. Based on literature search and sequence alignments, two primer pairs, a broadly reactive
Acknowledgements
We thank Susan Austin for helping with the sample collection. Grants from the National Institutes of Health (P01HD13021) and the Infectious Disease Scholar Fund of CCHMC to T.F., and the Hungarian National Research Grant OTKA (K81258) to L.E. were used to support this study.
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