Abstract
Nodaviruses are small bipartite RNA viruses which belong to the family of Nodaviridae. They are categorized into alpha-nodavirus, which infects insects, and beta-nodavirus, which infects fishes. Another distinct group of nodavirus infects shrimps and prawns, which has been proposed to be categorized as gamma-nodavirus. Our current review focuses mainly on recent studies performed on nodaviruses. Nodavirus can be transmitted vertically and horizontally. Recent outbreaks have been reported in China, Indonesia, Singapore and India, affecting the aquaculture industry. It also decreased mullet stock in the Caspian Sea. Histopathology and transmission electron microscopy (TEM) are used to examine the presence of nodaviruses in infected fishes and prawns. For classification, virus isolation followed by nucleotide sequencing are required. In contrast to partial sequence identification, profiling the whole transcriptome using next generation sequencing (NGS) offers a more comprehensive comparison and characterization of the virus. For rapid diagnosis of nodavirus, assays targeting the viral RNA based on reverse-transcription PCR (RT-PCR) such as microfluidic chips, reverse-transcription loop-mediated isothermal amplification (RT-LAMP) and RT-LAMP coupled with lateral flow dipstick (RT-LAMP-LFD) have been developed. Besides viral RNA detections, diagnosis based on immunological assays such as enzyme-linked immunosorbent assay (ELISA), immunodot and Western blotting have also been reported. In addition, immune responses of fish and prawn are also discussed. Overall, in fish, innate immunity, cellular type I interferon immunity and humoral immunity cooperatively prevent nodavirus infections, whereas prawns and shrimps adopt different immune mechanisms against nodavirus infections, through upregulation of superoxide anion, prophenoloxidase, superoxide dismutase (SOD), crustin, peroxinectin, anti-lipopolysaccharides and heat shock proteins (HSP). Potential vaccines for fishes and prawns based on inactivated viruses, recombinant proteins or DNA, either delivered through injection, oral feeding or immersion, are also discussed in detail. Lastly, a comprehensive review on nodavirus virus-like particles (VLPs) is presented. In recent years, studies on prawn nodavirus are mainly focused on Macrobrachium rosenbergii nodavirus (MrNV). Recombinant MrNV VLPs have been produced in prokaryotic and eukaryotic expression systems. Their roles as a nucleic acid delivery vehicle, a platform for vaccine development, a molecular tool for mechanism study and in solving the structures of MrNV are intensively discussed.
Highlights
The current review discusses recent studies related to nodaviruses
To the best of our knowledge, there are only eight review articles related to nodavirus which had been published within the past five years: immunological-based detection of shrimp viruses (Chaivisuthangkura, Longyant & Sithigorngul, 2014); recombinant nodavirus-like particles as delivery system (Jariyapong, 2015); the life cycle of beta-nodaviruses (Low et al, in press); viral encephalopathy and retinopathy in aquaculture (Doan et al, 2017); interaction between beta-nodavirus and its host for development of prophylactic measures for viral encephalopathy and retinopathy (Costa & Thompson, 2016); reactive oxygen species-mediated cell death (Reshi, Su & Hong, 2014); mitochondrial disruption and necrotic cell death (Hong, 2013); and immunity to beta-nodavirus infections of marine fish (Chen, Wang & Chen, 2014)
Through the use of endosomal inhibitors coupled with laser confocal microscopy and live cell imaging, we demonstrated that the internalization of Macrobrachium rosenbergii nodavirus (MrNV) virus-like particles (VLPs) was facilitated by clathrin- and caveolae-mediated endocytosis
Summary
The current review discusses recent studies related to nodaviruses. Recent reported outbreaks of nodaviruses, diagnostic assays, host immunological responses, vaccines, and virus-like particles (VLPs) are emphasized. To the best of our knowledge, there are only eight review articles related to nodavirus which had been published within the past five years: immunological-based detection of shrimp viruses (Chaivisuthangkura, Longyant & Sithigorngul, 2014); recombinant nodavirus-like particles as delivery system (Jariyapong, 2015); the life cycle of beta-nodaviruses (Low et al, in press); viral encephalopathy and retinopathy in aquaculture (Doan et al, 2017); interaction between beta-nodavirus and its host for development of prophylactic measures for viral encephalopathy and retinopathy (Costa & Thompson, 2016); reactive oxygen species-mediated cell death (Reshi, Su & Hong, 2014); mitochondrial disruption and necrotic cell death (Hong, 2013); and immunity to beta-nodavirus infections of marine fish (Chen, Wang & Chen, 2014) Another two review articles published within the past 10 years are about the biology and biomedical applications of Flock House virus (Venter & Schneemann, 2008), and white-tail-disease (WTD) in Macrobrachium rosenbergii (Bonami & Sri Widada, 2011). None of these articles review the recent advances in the study of nodaviruses as presented in the current review
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