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Nodamura virus B2 amino terminal domain sensitivity to small interfering RNA

Ali PS, John J, Selvaraj M, Kek TL, Salleh MZ

Microbiol. Immunol., 2015 May;59(5):299-304.
PMID: 25753649 DOI: 10.1111/1348-0421.12253

Nodamura virus (NoV) B2, a suppressor of RNA interference, binds double stranded RNAs (dsRNAs) and small interfering RNAs (siRNAs) corresponding to Dicer substrates and products. Here, we report that the amino terminal domain of NoV B2 (NoV B2 79) specifically binds siRNAs but not dsRNAs. NoV B2 79 oligomerizes on binding to 27 nucleotide siRNA. Mutation of the residues phenylalanine49 and alanine60 to cysteine and methionine, respectively enhances the RNA binding affinity of NoV B2 79. Circular dichroism spectra demonstrated that the wild type and mutant NoV B2 79 have similar secondary structure conformations.

Matched MeSH terms: Nodaviridae/genetics; Nodaviridae/physiology*
Risk factors associated with viral nervous necrosis in hybrid groupers in Malaysia and the high similarity of its causative agent nervous necrosis virus to reassortant red-spotted grouper nervous necrosis virus/striped jack nervous necrosis virus strains

Ariff N, Abdullah A, Azmai MNA, Musa N, Zainathan SC

Vet World, 2019 Aug;12(8):1273-1284.
PMID: 31641308 DOI: 10.14202/vetworld.2019.1273-1284

Background and Aim: Viral nervous necrosis (VNN) is a serious disease of several marine fish species. VNN causes 100% mortality in the larval stages, while lower losses have been reported in juvenile and adult fish. This study aimed to detect the occurrence of VNN while identifying its associated risk factors and the genotypes of its causative agent in a hybrid grouper hatchery in Malaysia.
Materials and Methods: A batch of newly hatched hybrid grouper fry (Epinephelus fuscoguttatus × Epinephelus lanceolatus) were followed from the larval stage to market size. Samples of the hybrid groupers, water, live feed, and artificial fish pellets were collected periodically from day 0 to 180 in the hybrid grouper hatchery. Reverse transcription-polymerase chain reaction (RT-PCR) and nested PCR amplifications were carried out on VNN-related sequences. The phylogenetic tree including the sampled causative agent of VNN was inferred from the coat protein genes from all known Betanodavirus species using Molecular Evolutionary Genetics Analysis (MEGA). Pearson's correlation coefficient values were calculated to determine the strength of the correlation between the presence of VNN in hybrid grouper samples and its associated risk factors.
Results: A total of 113 out of 146 pooled and individual samples, including hybrid grouper, water, and artificial fish pellet samples, demonstrated positive results in tests for the presence of VNN-associated viruses. The clinical signs of infection observed in the samples included darkened skin, deformation of the backbone, abdominal distension, skin lesions, and fin erosion. VNN was present throughout the life stages of the hybrid groupers, with the first detection occurring at day 10. VNN-associated risk factors included water temperature, dissolved oxygen content, salinity, ammonia level, fish size (adults more at risk than younger stages), and life stage (age). Detection of VNN-associated viruses in water samples demonstrated evidence of horizontal transmission of the disease. All the nucleotide sequences found in this study had high nucleotide identities of 88% to 100% to each other, striped jack nervous necrosis virus (SJNNV), and the reassortant strain red-spotted grouper NNV/SJNNV (RGNNV/SJNNV) isolate 430.2004 (GenBank accession number JN189932.1) (n=26). The phylogenetic analysis showed that quasispecies was present in each VNN-causing virus-positive sample, which differed based on the type of sample and life stage.
Conclusion: This study was the first to confirm the existence of a reassortant strain (RGNNV/SJNNV) in hybrid groupers from Malaysia and Southeast Asia. However, the association between the mode of transmission and the risk factors of this virus needs to be investigated further to understand the evolution and potential new host species of the reassortant strain.

Matched MeSH terms: Nodaviridae
Macrobrachium rosenbergii mannose binding lectin: synthesis of MrMBL-N20 and MrMBL-C16 peptides and their antimicrobial characterization, bioinformatics and relative gene expression analysis

Arockiaraj J, Chaurasia MK, Kumaresan V, Palanisamy R, Harikrishnan R, Pasupuleti M, et al.

Fish Shellfish Immunol, 2015 Apr;43(2):364-74.
PMID: 25575476 DOI: 10.1016/j.fsi.2014.12.036

Mannose-binding lectin (MBL), an antimicrobial protein, is an important component of innate immune system which recognizes repetitive sugar groups on the surface of bacteria and viruses leading to activation of the complement system. In this study, we reported a complete molecular characterization of cDNA encoded for MBL from freshwater prawn Macrobrachium rosenbergii (Mr). Two short peptides (MrMBL-N20: (20)AWNTYDYMKREHSLVKPYQG(39) and MrMBL-C16: (307)GGLFYVKHKEQQRKRF(322)) were synthesized from the MrMBL polypeptide. The purity of the MrMBL-N20 (89%) and MrMBL-C16 (93%) peptides were confirmed by MS analysis (MALDI-ToF). The purified peptides were used for further antimicrobial characterization including minimum inhibitory concentration (MIC) assay, kinetics of bactericidal efficiency and analysis of hemolytic capacity. The peptides exhibited antimicrobial activity towards all the Gram-negative bacteria taken for analysis, whereas they showed the activity towards only a few selected Gram-positive bacteria. MrMBL-C16 peptides produced the highest inhibition towards both the Gram-negative and Gram-positive bacteria compared to the MrMBL-N20. Both peptides do not produce any inhibition against Bacillus sps. The kinetics of bactericidal efficiency showed that the peptides drastically reduced the number of surviving bacterial colonies after 24 h incubation. The results of hemolytic activity showed that both peptides produced strong activity at higher concentration. However, MrMBL-C16 peptide produced the highest activity compared to the MrMBL-N20 peptide. Overall, the results indicated that the peptides can be used as bactericidal agents. The MrMBL protein sequence was characterized using various bioinformatics tools including phylogenetic analysis and structure prediction. We also reported the MrMBL gene expression pattern upon viral and bacterial infection in M. rosenbergii gills. It could be concluded that the prawn MBL may be one of the important molecule which is involved in antimicrobial mechanism. Moreover, MrMBL derived MrMBL-N20 and MrMBL-C16 peptides are important antimicrobial peptides for the recognition and eradication of viral and bacterial pathogens.

Matched MeSH terms: Nodaviridae/physiology
Molecular importance of prawn large heat shock proteins 60, 70 and 90

Chaurasia MK, Nizam F, Ravichandran G, Arasu MV, Al-Dhabi NA, Arshad A, et al.

Fish Shellfish Immunol, 2016 Jan;48:228-38.
PMID: 26631804 DOI: 10.1016/j.fsi.2015.11.034

Considering the importance of heat shock proteins (HSPs) in the innate immune system of prawn, a comparative molecular approach was proposed to study the crustacean large HSPs 60, 70 and 90. Three different large HSPs were identified from freshwater prawn Macrobrachium rosenbergii (Mr) cDNA library during screening. The structural and functional characteristic features of HSPs were studied using various bioinformatics tools. Also, their gene expression and mRNA regulation upon various pathogenic infections was studied by relative quantification using 2(-ΔΔCT) method. MrHSP60 contains a long chaperonin 60 domain at 46-547 which carries a chaperonin 60 signature motif between 427 and 438, whereas MrHSP70 contains a long HSP70 domain at 21-624 and MrHSP90 carries a HSP90 domain at 188-719. The two dimensional analysis showed that MrHSP60 contains more amino acids (52%) in helices, whereas MrHSP70 (40.6%) and MrHSP90 (51.8%) carried more residues in coils. Gene expression results showed significant (P

Matched MeSH terms: Nodaviridae
Feasibility of vaccination against Macrobrachium rosenbergii nodavirus infection in giant freshwater prawn

Chen-Fei L, Chou-Min C, Jiun-Yan L

Fish Shellfish Immunol, 2020 Sep;104:431-438.
PMID: 32580003 DOI: 10.1016/j.fsi.2020.06.039

The giant freshwater prawn/giant river prawn, Macrobrachium rosenbergii is one of the high market value crustaceans cultured worldwide. The intensified aquaculture of the species has led to the outbreak of infectious diseases, prominently, the white tail disease (WTD). It is caused by the infection of Macrobrachium rosenbergii nodavirus (MrNV), which was classified in the family of Nodaviridae. To-date, there are no effective prophylactic and therapeutic agents available against MrNV infection. Vaccination is known to be the most effective prophylactic agent in disease prevention. However, vaccine development against virus infection in crustaceans is equivocal. The feasibility of vaccination in conferring immune protection in crustaceans against infectious diseases is disputable. The argument lies in the fact that crustaceans do not possess adaptive immunity, which is the main immune component that functions to establish immunological memory upon vaccination. Nevertheless, an increasing number of literatures has been documented, which concerns the development of vaccines against infectious diseases in crustaceans. The current review deliberates different approaches in vaccine development against MrNV, which were documented in the past years. It is noteworthy that the live-attenuated MrNV vaccine has not been experimented by far. Thus, the potential of live-attenuated MrNV vaccine in conferring long-term immune protection through the establishment of innate immune memory is currently being discussed.

Matched MeSH terms: Nodaviridae/immunology*
Fulltext A Case Study on the Mortality of Cobia (Rachycentron canadum) Cultured in Traditional Cages

Chu KB, Abdulah A, Abdullah SZ, Bakar RA

Trop Life Sci Res, 2013 Dec;24(2):77-84.
PMID: 24575250 MyJurnal

The mass mortality of cobia (Rachycentron canadum) within 2-3 days was reported by 3 private farms in Bukit Tambun, Pulau Pinang, in February and March 2007. Only cobia with body weights of 3-4 kg were affected. Most diseased cobia swam on the surface and displayed flashing behaviour. All samples were positive for viral nervous necrosis (VNN) with low to medium levels of infection. Infestations by leeches (Zeylanicobdella arugamensis), body monogeneans (Benedenia sp.) and copepods (Caligus sp.) were also found, but no pathogenic bacteria were isolated. All water quality parameters monitored were within optimal ranges for culturing cobia. The main causes of high mortality in cobia remain unclear during the study. However, we believe that the mass mortality of cobia could be probably due to VNN infection and that the rate of mortality will increase further when cobia are subjected to aquaculture-related stresses (e.g., limited space). Traditional cages with a size of 2 (length) × 2 (width) × 1 m (depth) should only be used for rearing cobia below 1 kg in weight given the species' natural behaviours. In addition, cobia fingerlings should be screened for VNN prior to stocking them in cages.

Matched MeSH terms: Nodaviridae
RNA-binding region of Macrobrachium rosenbergii nodavirus capsid protein

Goh ZH, Mohd NAS, Tan SG, Bhassu S, Tan WS

J Gen Virol, 2014 Sep;95(Pt 9):1919-1928.
PMID: 24878641 DOI: 10.1099/vir.0.064014-0

White tail disease (WTD) kills prawn larvae and causes drastic losses to the freshwater prawn (Macrobrachium rosenbergii) industry. The main causative agent of WTD is Macrobrachium rosenbergii nodavirus (MrNV). The N-terminal end of the MrNV capsid protein is very rich in positively charged amino acids and is postulated to interact with RNA molecules. N-terminal and internal deletion mutagenesis revealed that the RNA-binding region is located at positions 20-29, where 80 % of amino acids are positively charged. Substitution of all these positively charged residues with alanine abolished the RNA binding. Mutants without the RNA-binding region still assembled into virus-like particles, suggesting that this region is not a part of the capsid assembly domain. This paper is, to the best of our knowledge, the first to report the specific RNA-binding region of MrNV capsid protein.

Matched MeSH terms: Nodaviridae/genetics*
Virus-like particles of Macrobrachium rosenbergii nodavirus produced in bacteria

Goh ZH, Tan SG, Bhassu S, Tan WS

J Virol Methods, 2011 Jul;175(1):74-9.
PMID: 21536072 DOI: 10.1016/j.jviromet.2011.04.021

Macrobrachium rosenbergii nodavirus (MrNv) infects giant freshwater prawns and causes white tail disease (WTD). The coding region of the capsid protein of MrNv was amplified with RT-PCR and cloned into the pTrcHis2-TOPO vector. The recombinant plasmid was introduced into Escherichia coli and protein expression was induced with IPTG. SDS-PAGE showed that the recombinant protein containing the His-tag and myc epitope has a molecular mass of about 46 kDa and it was detected by the anti-His antibody in Western blotting. The protein was purified using immobilized metal affinity chromatography (IMAC) and transmission electron microscopic analysis revealed that the recombinant protein assembled into virus-like particles (VLPs) with a diameter of about 30±3 nm. The size of the particles was confirmed by dynamic light scattering. Nucleic acids were extracted from the VLPs and treatment with nucleases showed that they were mainly RNA molecules. This is the first report describing the production of MrNv capsid protein in bacteria and its assembly into VLPs.

Matched MeSH terms: Nodaviridae/genetics; Nodaviridae/physiology*
Development and partial characterization of new marine cell line from brain of Asian sea bass Lates calcarifer for virus isolation

Hasoon MF, Daud HM, Abdullah AA, Arshad SS, Bejo HM

In Vitro Cell Dev Biol Anim, 2011 Jan;47(1):16-25.
PMID: 21082288 DOI: 10.1007/s11626-010-9348-5

A new cell line, Asian sea bass brain (ASBB), was derived from the brain tissue of Asian sea bass Lates calcarifer. This cell line was maintained in Leibovitz L-15 media supplemented with 10% fetal bovine serum (FBS). The ASBB cell line was subcultured more than 60 times over a period of 15 mo. The ASBB cell line consists predominantly of fibroblastic-like cells and was able to grow at temperatures between 20°C and 30°C with an optimum temperature of 25°C. The growth rate of these cells increased as the proportion of FBS increased from 2% to 20% at 25°C with optimum growth at the concentrations of 10% or 15% FBS. Polymerase chain reaction products were obtained from ASBB cells and tissues of sea bass with primer sets of microsatellite markers of sea bass. An isolate of piscine nodavirus from juveniles of marine fish species tested positive by IQ2000 kit for viral nervous necrosis detection and was examined for its infectivity to a fish cell line of ASBB. A marine fish betanodavirus was tested to determine the susceptibility of this new cell line in comparison with commercial highly permissive SSN-1 cells. The ASBB cell line was found to be susceptible to nodavirus (RGNNV genotype), and the infection was confirmed by comparison cytopathic effect (CPE) with commercial SSN-1 and reverse transcriptase-polymerase chain reaction. A nodavirus was further elucidated by electron microscopy, and the virus tested was shown to induce CPE on ASBB cells with significant high titer. This suggests that the ASBB cell line has good potential for the isolation of fish viruses.

Matched MeSH terms: Nodaviridae/physiology*; Nodaviridae/ultrastructure
Fulltext Cryo-Electron Microscopy Structure of the Macrobrachium rosenbergii Nodavirus Capsid at 7 Angstroms Resolution

Ho KL, Kueh CL, Beh PL, Tan WS, Bhella D

Sci Rep, 2017 05 18;7(1):2083.
PMID: 28522842 DOI: 10.1038/s41598-017-02292-0

White tail disease in the giant freshwater prawn Macrobrachium rosenbergii causes significant economic losses in shrimp farms and hatcheries and poses a threat to food-security in many developing countries. Outbreaks of Macrobrachium rosenbergii nodavirus (MrNV), the causative agent of white tail disease (WTD) are associated with up to 100% mortality rates. There are no interventions available to treat or prevent MrNV disease however. Here we show the structure of MrNV virus-like particles (VLPs) produced by recombinant expression of the capsid protein, using cryogenic electron microscopy. Our data show that MrNV VLPs package nucleic acids in a manner reminiscent of other known nodavirus structures. The structure of the capsid however shows striking differences from insect and fish infecting nodaviruses, which have been shown to assemble trimer-clustered T = 3 icosahedral virus particles. MrNV particles have pronounced dimeric blade-shaped spikes extending up to 6 nm from the outer surface of the capsid shell. Our structural analysis supports the assertion that MrNV may belong to a new genus of the Nodaviridae. Moreover, our study provides the first structural view of an important pathogen affecting aquaculture industries across the world.

Matched MeSH terms: Nodaviridae/classification; Nodaviridae/ultrastructure*
Fulltext Structure of the Macrobrachium rosenbergii nodavirus: A new genus within the Nodaviridae?

Ho KL, Gabrielsen M, Beh PL, Kueh CL, Thong QX, Streetley J, et al.

PLoS Biol, 2018 Oct;16(10):e3000038.
PMID: 30346944 DOI: 10.1371/journal.pbio.3000038

Macrobrachium rosenbergii nodavirus (MrNV) is a pathogen of freshwater prawns that poses a threat to food security and causes significant economic losses in the aquaculture industries of many developing nations. A detailed understanding of the MrNV virion structure will inform the development of strategies to control outbreaks. The MrNV capsid has also been engineered to display heterologous antigens, and thus knowledge of its atomic resolution structure will benefit efforts to develop tools based on this platform. Here, we present an atomic-resolution model of the MrNV capsid protein (CP), calculated by cryogenic electron microscopy (cryoEM) of MrNV virus-like particles (VLPs) produced in insect cells, and three-dimensional (3D) image reconstruction at 3.3 Å resolution. CryoEM of MrNV virions purified from infected freshwater prawn post-larvae yielded a 6.6 Å resolution structure, confirming the biological relevance of the VLP structure. Our data revealed that unlike other known nodavirus structures, which have been shown to assemble capsids having trimeric spikes, MrNV assembles a T = 3 capsid with dimeric spikes. We also found a number of surprising similarities between the MrNV capsid structure and that of the Tombusviridae: 1) an extensive network of N-terminal arms (NTAs) lines the capsid interior, forming long-range interactions to lace together asymmetric units; 2) the capsid shell is stabilised by 3 pairs of Ca2+ ions in each asymmetric unit; 3) the protruding spike domain exhibits a very similar fold to that seen in the spikes of the tombusviruses. These structural similarities raise questions concerning the taxonomic classification of MrNV.

Matched MeSH terms: Nodaviridae/classification; Nodaviridae/pathogenicity; Nodaviridae/ultrastructure*
Fulltext A Novel RNA Virus, Macrobrachium rosenbergii Golda Virus (MrGV), Linked to Mass Mortalities of the Larval Giant Freshwater Prawn in Bangladesh

Hooper C, Debnath PP, Biswas S, van Aerle R, Bateman KS, Basak SK, et al.

Viruses, 2020 10 02;12(10).
PMID: 33023199 DOI: 10.3390/v12101120

Mass mortalities of the larval stage of the giant freshwater prawn, Macrobrachium rosenbergii, have been occurring in Bangladesh since 2011. Mortalities can reach 100% and have resulted in an 80% decline in the number of hatcheries actively producing M. rosenbergii. To investigate a causative agent for the mortalities, a disease challenge was carried out using infected material from a hatchery experiencing mortalities. Moribund larvae from the challenge were prepared for metatranscriptomic sequencing. De novo virus assembly revealed a 29 kb single‑stranded positive-sense RNA virus with similarities in key protein motif sequences to yellow head virus (YHV), an RNA virus that causes mass mortalities in marine shrimp aquaculture, and other viruses in the Nidovirales order. Primers were designed against the novel virus and used to screen cDNA from larvae sampled from hatcheries in the South of Bangladesh from two consecutive years. Larvae from all hatcheries screened from both years were positive by PCR for the novel virus, including larvae from a hatchery that at the point of sampling appeared healthy, but later experienced mortalities. These screens suggest that the virus is widespread in M. rosenbergii hatchery culture in southern Bangladesh, and that early detection of the virus can be achieved by PCR. The hypothesised protein motifs of Macrobrachium rosenbergii golda virus (MrGV) suggest that it is likely to be a new species within the Nidovirales order. Biosecurity measures should be taken in order to mitigate global spread through the movement of post-larvae within and between countries, which has previously been linked to other virus outbreaks in crustacean aquaculture.

Matched MeSH terms: Nodaviridae/genetics; Nodaviridae/isolation & purification
Comparative genome analysis reveals a distinct influence of nucleotide composition on virus-host species-specific interaction of prawn-infecting nodavirus

Ismail SNFB, Baharum SN, Fazry S, Low CF

J Fish Dis, 2019 Dec;42(12):1761-1772.
PMID: 31637743 DOI: 10.1111/jfd.13093

Discovery of species-specific interaction between the host and virus has drawn the interest of many researchers to study the evolution of the newly emerged virus. Comparative genome analysis provides insights of the virus functional genome evolution and the underlying mechanisms of virus-host interactions. The analysis of nucleotide composition signified the evolution of nodavirus towards host specialization in a host-specific mutation manner. GC-rich genome of betanodavirus was significantly deficient in UpA and UpU dinucleotides composition, whilst the AU-rich genome of gammanodavirus was deficient in CpG dinucleotide. The capsid of MrNV and PvNV of gammanodavirus retains the highest abundance of adenine and uracil at the second codon position, respectively, which were found to be very distinctive from the other genera. ENC-GC3 plot inferred the influence of natural selection and mutational pressure in shaping the evolution of MrNV RdRp and capsid, respectively. Furthermore, CAI/eCAI analysis predicts a comparable adaptability of MrNV in squid, Sepia officinalis than its natural host, Macrobrachium rosenbergii. Thus, further study is warranted to investigate the capacity of MrNV replication in S. officinalis owing to its high codon adaptation index.

Matched MeSH terms: Nodaviridae/genetics*
Virus-like particle of Macrobrachium rosenbergii nodavirus produced in Spodoptera frugiperda (Sf9) cells is distinctive from that produced in Escherichia coli

Kueh CL, Yong CY, Masoomi Dezfooli S, Bhassu S, Tan SG, Tan WS

Biotechnol Prog, 2017 Mar;33(2):549-557.
PMID: 27860432 DOI: 10.1002/btpr.2409

Macrobrachium rosenbergii nodavirus (MrNV) is a virus native to giant freshwater prawn. Recombinant MrNV capsid protein has been produced in Escherichia coli, which self-assembled into virus-like particles (VLPs). However, this recombinant protein is unstable, degrading and forming heterogenous VLPs. In this study, MrNV capsid protein was produced in insect Spodoptera frugiperda (Sf9) cells through a baculovirus system. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that the recombinant protein produced by the insect cells self-assembled into highly stable, homogenous VLPs each of approximately 40 nm in diameter. Enzyme-linked immunosorbent assay (ELISA) showed that the VLPs produced in Sf9 cells were highly antigenic and comparable to those produced in E. coli. In addition, the Sf9 produced VLPs were highly stable across a wide pH range (2-12). Interestingly, the Sf9 produced VLPs contained DNA of approximately 48 kilo base pairs and RNA molecules. This study is the first report on the production and characterization of MrNV VLPs produced in a eukaryotic system. The MrNV VLPs produced in Sf9 cells were about 10 nm bigger and had a uniform morphology compared with the VLPs produced in E. coli. The insect cell production system provides a good source of MrNV VLPs for structural and immunological studies as well as for host-pathogen interaction studies. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:549-557, 2017.

Matched MeSH terms: Nodaviridae/genetics; Nodaviridae/metabolism*
Fulltext Data set of phylogenetic analysis inferred based on the complete genomes of the family Nodaviridae

Low CF, Bunawan H

Data Brief, 2016 Sep;8:1454-61.
PMID: 27617282 DOI: 10.1016/j.dib.2016.08.025

In this article, nine complete genomes of viruses from the genus Alphanodavirus and Betanodavirus (Family Nodaviridae) were comparatively analyzed and the data of their evolutionary origins and relatedness are reported. The nucleotide sequence alignment of the complete genomes from all species and their deduced evolutionary relationships are presented. High sequence similarity within the genus Betanodavirus compared to the genus Alphanodavirus was revealed in multiple sequence alignment of the Nodaviridae genomes. The amino acid sequence similarity for both RNA1 and RNA2 ORF is more conserved in Betanodavirus, compared to Alphanodavirus. The conserved and variable regions within the virus genome that were defined based on the multiple sequence alignments are presented in this dataset.

Matched MeSH terms: Nodaviridae
Betanodavirus: Dissection of the viral life cycle

Low CF, Syarul Nataqain B, Chee HY, Rozaini MZH, Najiah M

J Fish Dis, 2017 Nov;40(11):1489-1496.
PMID: 28449248 DOI: 10.1111/jfd.12638

Progressive research has been recently made in dissecting the molecular biology of Betanodavirus life cycle, the causative pathogen of viral encephalopathy and retinopathy in economic important marine fish species. Establishment of betanodavirus infectious clone allows the manipulation of virus genome for functional genomic study, which elucidates the biological event of the viral life cycle at molecular level. The betanodavirus strategizes its replication by expressing anti-apoptosis/antinecrotic proteins to maintain the cell viability during early infection. Subsequently utilizes and controls the biological machinery of the infected cells for viral genome replication. Towards the late phase of infection, mass production of capsid protein for virion assembly induces the activation of host apoptosis pathway. It eventually leads to the cell lysis and death, which the lysis of cell contributes to the accomplishment of viral shedding that completes a viral life cycle. The recent efforts to dissect the entire betanodavirus life cycle are currently reviewed.

Matched MeSH terms: Nodaviridae/physiology*
Molecular biology of Macrobrachium rosenbergii nodavirus infection in giant freshwater prawn

Low CF, Md Yusoff MR, Kuppusamy G, Ahmad Nadzri NF

J Fish Dis, 2018 Dec;41(12):1771-1781.
PMID: 30270534 DOI: 10.1111/jfd.12895

Macrobrachium rosenbergii nodavirus (MrNV) has been threatening the giant freshwater prawn aquaculture since 1997, causing white tail disease in the prawn species that leads to 100% lethality of the infected postlarvae. Comprehension of the viral infectivity and pathogenesis at molecular biology level has recently resolved the viral capsid protein and evidenced the significant difference in the viral structural protein compared to other nodaviruses that infect fish and insect. Cumulative researches have remarked the proposal to assert MrNV as a member of new genus, gammanodavirus to the Nodaviridae family. The significance of molecular biology in MrNV infection is being highlighted in this current review, revolving the viral life cycle from virus binding and entry into host, virus replication in host cell, to virus assembly and release. The current review also highlights the emerging aptamers technology that is also known as synthetic antibody, its application in disease diagnosis, and its prophylactic and therapeutic properties. The future perspective of synthetic virology technology in understanding viral pathogenesis, as well as its potential in viral vaccine development, is also discussed.

Matched MeSH terms: Nodaviridae/physiology*
Fulltext Chimeric Virus-Like Particles of Prawn Nodavirus Displaying Hepatitis B Virus Immunodominant Region: Biophysical Properties and Cytokine Response

Ninyio NN, Ho KL, Yong CY, Chee HY, Hamid M, Ong HK, et al.

Int J Mol Sci, 2021 Feb 15;22(4).
PMID: 33672018 DOI: 10.3390/ijms22041922

Hepatitis B is a major global health challenge. In the absence of an effective treatment for the disease, hepatitis B vaccines provide protection against the viral infection. However, some individuals do not have positive immune responses after being vaccinated with the hepatitis B vaccines available in the market. Thus, it is important to develop a more protective vaccine. Previously, we showed that hepatitis B virus (HBV) 'a' determinant (aD) displayed on the prawn nodavirus capsid (Nc) and expressed in Spodoptera frugiperda (Sf9) cells (namely, Nc-aD-Sf9) self-assembled into virus-like particles (VLPs). Immunisation of BALB/c mice with the Nc-aD-Sf9 VLPs showed significant induction of humoral, cellular and memory B-cell immunity. In the present study, the biophysical properties of the Nc-aD-Sf9 VLPs were studied using dynamic light scattering (DLS) and circular dichroism (CD) spectroscopy. Enzyme-linked immunosorbent assay (ELISA) was used to determine the antigenicity of the Nc-aD-Sf9 VLPs, and multiplex ELISA was employed to quantify the cytokine response induced by the VLPs administered intramuscularly into BALB/c mice (n = 8). CD spectroscopy of Nc-aD-Sf9 VLPs showed that the secondary structure of the VLPs predominantly consisted of beta (β)-sheets (44.8%), and they were thermally stable up to ~52 °C. ELISA revealed that the aD epitope of the VLPs was significantly antigenic to anti-HBV surface antigen (HBsAg) antibodies. In addition, multiplex ELISA of serum samples from the vaccinated mice showed a significant induction (p < 0.001) of IFN-γ, IL-4, IL-5, IL-6, IL-10, and IL-12p70. This cytokine profile is indicative of natural killer cell, macrophage, dendritic cell and cytotoxic T-lymphocyte activities, which suggests a prophylactic innate and adaptive cellular immune response mediated by Nc-aD-Sf9 VLPs. Interestingly, Nc-aD-Sf9 induced a more robust release of the aforementioned cytokines than that of Nc-aD VLPs produced in Escherichia coli and a commercially used hepatitis B vaccine. Overall, Nc-aD-Sf9 VLPs are thermally stable and significantly antigenic, demonstrating their potential as an HBV vaccine candidate.

Matched MeSH terms: Nodaviridae/immunology*
Genome analysis of Betanodavirus from cultured marine fish species in Malaysia

Ransangan J, Manin BO

Vet Microbiol, 2012 Apr 23;156(1-2):16-44.
PMID: 22051446 DOI: 10.1016/j.vetmic.2011.10.002

Betanodavirus is the causative agent of the viral nervous necrosis (VNN) or viral encephalopathy and retinopathy disease in marine fish. This disease is responsible for most of the mass mortalities that occurred in marine fish hatcheries in Malaysia. The genome of this virus consists of two positive-sense RNA molecules which are the RNA1 and RNA2. The RNA1 molecule contains the RdRp gene which encodes for the RNA-dependent RNA polymerase and the RNA2 molecule contains the Cp gene which encodes for the viral coat protein. In this study, total RNAs were extracted from 32 fish specimens representing the four most cultured marine fish species in Malaysia. The fish specimens were collected from different hatcheries and aquaculture farms in Malaysia. The RNA1 was successfully amplified using three pairs of overlapping PCR primers whereas the RNA2 was amplified using a pair of primers. The nucleotide analysis of RdRp gene revealed that the Betanodavirus in Malaysia were 94.5-99.7% similar to the RGNNV genotype, 79.8-82.1% similar to SJNNV genotype, 81.5-82.4% similar to BFNNV genotype and 79.8-80.7% similar to TPNNV genotype. However, they showed lower similarities to FHV (9.4-14.2%) and BBV (7.2-15.7%), respectively. Similarly, the Cp gene revealed that the viruses showed high nucleotide similarity to RGNNV (95.9-99.8%), SJNNV (72.2-77.4%), BFNNV (80.9-83.5%), TPNNV (77.2-78.1%) and TNV (75.1-76.5%). However, as in the RdRp gene, the coat protein gene was highly dissimilar to FHV (3.0%) and BBV (2.6-4.1%), respectively. Based on the genome analysis, the Betanodavirus infecting cultured marine fish species in Malaysia belong to the RGNNV genotype. However, the phylogenetic analysis of the genes revealed that the viruses can be further divided into nine sub-groups. This has been expected since various marine fish species of different origins are cultured in Malaysia.

Matched MeSH terms: Nodaviridae/classification; Nodaviridae/genetics*
Mass mortality of hatchery-produced larvae of Asian seabass, Lates calcarifer (Bloch), associated with viral nervous necrosis in Sabah, Malaysia

Ransangan J, Manin BO

Vet Microbiol, 2010 Sep 28;145(1-2):153-7.
PMID: 20427132 DOI: 10.1016/j.vetmic.2010.03.016

Culture of Asian seabass, Lates calcarifer (Bloch) is a popular aquaculture activity in Malaysia. This fish is in high demand and fetches a good price in the local market. The seed for this fish is commercially produced by induced spawning in hatcheries. However, the seed supply is affected by frequent mass mortality of larvae aged between 15 and 60 dph. The clinical signs shown by the affected larvae include lethargy, loss of appetite, uncoordinated swimming, unusual spiral movement pattern and dark coloration. Histological examination of brain and eye of the affected specimens revealed extensive cell vacuolation in larvae aged 15-25 dph. Partial nucleotide sequence of the nervous necrosis virus coat protein gene of the affected larvae showed 94.0-96.1% homology to the nucleotide sequences of coat protein gene from nervous necrosis virus isolated from other countries in the Southeast Asia and Australia. This study provides scientific evidence based on molecular technique that many episodes of mass mortality in seabass larvae in Sabah is associated with the viral nervous necrosis. Because no effective treatment has been reported for this infection, stringent biosecurity measures must be adopted for exclusion of the pathogen from the culture system.

Matched MeSH terms: Nodaviridae/genetics*

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