Ultrastructural and sequence characterization of Penaeus vannamei nodavirus (PvNV) from Belize

Abstract

The Penaeus vannamei nodavirus (PvNV), which causes muscle necrosis in Penaeus vannamei from Belize, was identified in 2005. Infected shrimp show clinical signs of white, opaque lesions in the tail muscle. Under transmission electron microscopy, the infected cells exhibit increases in various organelles, including mitochondria, Golgi stacks, and rough endoplasmic reticulum. Cytoplasmic inclusions containing para-crystalline arrays of virions were visualized. The viral particle is spherical in shape and 19 to 27 nm in diameter. A cDNA library was constructed from total RNA extracted from infected shrimp. Through nucleotide sequencing from the cDNA clones and northern blot hybridization, the PvNV genome was shown to consist of 2 segments: RNA1 (3111 bp) and RNA2 (1183 bp). RNA1 contains 2 overlapped open reading frames (ORF A and B), which may encode a RNA-dependent RNA polymerase (RdRp) and a B2 protein, respectively. RNA2 contains a single ORF that may encode the viral capsid protein. Sequence analyses showed the presence of 4 RdRp characteristic motifs and 2 conserved domains (RNA-binding B2 protein and viral coat protein) in the PvNV genome. Phylo genetic analysis based on the translated amino acid sequence of the RdRp reveals that PvNV is a member of the genus Alphanodavirus and closely related to Macrobrachium rosenbergii nodavirus (MrNV). In a study investigating potential PvNV vectors, we monitored the presence of PvNV by RT-PCR in seabird feces and various aquatic organisms collected around a shrimp farm in Belize. PvNV was detected in mosquitofish, seabird feces, barnacles, and zooplankton, suggesting that PvNV can be spread via these carriers. KEY WORDS: Penaeus vannamei nodavirus · PvNV · Ultrastructure · Genomic sequencing · Mechanical carriersResale or republication not permitted without written consent of the publisher RNA-dependent RNA polymerase (RdRp), and RNA2 encodes the capsid protein. RNA3 encodes 1 or 2 small proteins (designated B1 and B2). The function of B1 is not known, but B2 is a double-stranded RNA-binding protein described in other noda viruses, such as Flock House virus (FHV) and Greasy grouper nervous necrosis virus (GGNNV), to act as a suppressor against host antiviral RNA-silencing res ponse (Li et al. 2002, Lingel et al. 2005, Fenner et al. 2006. However, whether the B2 of PvNV functions similarly in the shrimp cells is not yet known.In the present study, we examined the morphogenesis of PvNV under transmission electron microscopy (TEM), sequenced its genome (both RNA1 and RNA2), and determined the taxonomic status of the virus. In addition, we investigated potential carriers of PvNV collected from shrimp ponds. MATERIALS AND METHODSPvNV-infected shrimp. Shrimp taxonomy was according to Holthius (1980). The PvNV-infected Penaeus vannamei used in this study were generated by laboratory infection from an isolate obtained from a farm in Belize in 2005. The preparation of inoculum and laboratory infection procedure were described by Tang et al (2007).Electron microscopy s...

Exploration of the virome of the European brown shrimp (Crangon crangon)

“…In the case of the Nodaviridae, it is surprising to find CcNoLV mainly in the hepatopancreas samples, because the main tissue for infection of related viruses is the tail muscle. Viruses of this family are known to cause white tail disease in, for example, Macrobrachium rosenbergii and P. vannamei [2,58,59]. Members of the Densovirinae subfamily (family Parvoviridae) are known to mainly infect tissues of mesodermal and ectodermal origin, but in some cases they are also able to infect endodermal tissues [2].…”

Retracted: Reverse transcription loop-mediated isothermal amplification (RT-LAMP) combined with colorimetric gold nanoparticle (AuNP) probe assay for visual detection ofPenaeus vannameinodavirus (PvNV)

“…Pv NV is a member of the family Nodaviridae and genus Alphanodavirus (Tang et al . ). Pv NV contains two segmented genome of positive‐sense single‐stranded RNA, the sequence of genomic segment 1 (3111 bp) encoded the RNA‐dependent RNA polymerase (RdRp) and the B2 protein, and segment 2 (1183 bp) encoded the viral capsid protein (Tang et al .…”

“…Pv NV contains two segmented genome of positive‐sense single‐stranded RNA, the sequence of genomic segment 1 (3111 bp) encoded the RNA‐dependent RNA polymerase (RdRp) and the B2 protein, and segment 2 (1183 bp) encoded the viral capsid protein (Tang et al . ). Moreover, Pv NV sequence analysis has revealed a similarity to that of Macrobrachium rosenbergii nodavirus ( Mr NV) affected the freshwater prawn M. rosenbergii (Bonami et al .…”

“…; Tang et al . ). On the other hand, the clinical signs of infected shrimp showed whitened abdominal muscles and histological signs of coagulative muscle necrosis with haemocytic aggregation are impossible to differentiate from the sign of infectious myonecrosis virus (IMNV) infection (Flegel ; Tang et al .…”

“…On the other hand, the clinical signs of infected shrimp showed whitened abdominal muscles and histological signs of coagulative muscle necrosis with haemocytic aggregation are impossible to differentiate from the sign of infectious myonecrosis virus (IMNV) infection (Flegel ; Tang et al . ). Moreover, Pv NV has potentially spread via various aquatic organisms such as mosquitofish, seabird faeces, barnacles and zooplankton (Tang et al .…”