Birnaviridae
Aquabirnavirus
Infectious bursal disease virus
Infectious pancreatic necrosis virus
Viral Structural Proteins
Molecular Sequence Data
RNA Replicase
Gill lamellar pillar cell necrosis, a new birnavirus disease in Japanese eels. (1/29)
Since the late 1980s, a birnaviral gill disease has been occurring in Japanese eels Anguilla japonica reared in warmwater ponds in western regions in Japan. Diseased eels mostly displayed marked formations of aneurysmal hematomas within gill lamellae and high mortalities. Histological examination revealed necrosis of pillar cells and subsequent aggregation of erythrocytes inside the lamellar capillaries, and proliferation of interlamellar epithelia onto the lamellae. Gastric gland cells were also necrotized. Electron microscopy revealed birnavirus infection in lamellar pillar cells. The causative birnavirus was isolated and cultured in fish cell lines and was found to be related to an infectious pancreatic necrosis virus (IPNV) Sp serotype by neutralization tests. The viral pathogenicity was confirmed by the results of histopathological examinations and infectivity experiments. (+info)Characteristics of a new birnavirus associated with a warm-water fish cell line. (2/29)
A warm-water fish cell line developed from blotched snakehead caudal peduncle (BSN) was found to have persistent birnavirus infection. Purified virus particles were of icosahedral shape and had 57+/-1.6 nm diameter. The BSN virus was resistant to 5-iodo-2'-deoxyuridine and induced yellowish-green cytoplasmic inclusions when stained with acridine orange. The virus was resistant to chloroform, acid and alkaline pH and heat treatment at 56 degrees C for 2 h. Purified virions had a buoyant density of 1.33 g/ml in CsCl and contained two genomic segments with molecular masses of 2.56 x 10(6) and 2.00 x 10(6) Da and four structural polypeptides of 112 (polyprotein, PP), 91 (VP1), 44 (VP2) and 37 (VP3) kDa. Reciprocal beta cross-neutralization tests incorporating four classical strains of infectious pancreatic necrosis virus (IPNV) (WB, Sp, Ab and TV-1) and the BSN virus established the complete serological distinctness of the virus from IPNV. Considering the uniqueness of the virus, the name blotched snakehead virus is proposed for this agent. (+info)Isolation of different types of birnavirus from ayu Plecoglossus altivelis and amago salmon Oncorhynchus rhodurus cultured in the same geographic area. (3/29)
A birnavirus was recently isolated from cultured ayu Plecoglossus altivelis on Shikoku island, Japan. The diseased fish displayed vertebral or vertical curvature and mild haemorrhage around the brain. Cytopathic effects (CPE) of the virus, including cell roundness, filamentous change and cell lysis, were observed in CHSE-214, RTG-2 and RSBK-2 cells. The virus isolated from ayu, designated the AY-98 strain, was found to be antigenically related to the marine birnavirus (MABV) Y-6 strain that originated from yellowtail Seriola quinqueradiata. AY-98 had a bi-segmented RNA genome and the same nucleotide sequence in the 310 bp VP2/NS junction as MABV Y-6. At the same time that the ayu epizootics occurred, another birnavirus (AM-98) was isolated from amago salmon Oncorhynchus rhodurus which were cultured 66 km away from the ayu farm. AM-98 showed a similar CPE and had the same host cell ranges as AY-98. However, AM-98 was serologically similar to the VR-299 strain of infectious pancreatic necrosis virus (IPNV) and their nucleotide sequences in the VP2/NS junction region showed 98% homology without changes at the amino acid level. In this study, the ayu strain AY-98 was grouped into MABV, whereas the amago salmon strain AM-98 was grouped into IPNV. This indicates that the 2 birnaviruses originated from different sources in spite of the fact that the places where they were isolated are close to one another. The results in this paper show a new aspect of the traditional consensus that the same serogroup of birnavirus distribute in close geographic areas. (+info)Active residues and viral substrate cleavage sites of the protease of the birnavirus infectious pancreatic necrosis virus. (4/29)
The polyprotein of infectious pancreatic necrosis virus (IPNV), a birnavirus, is processed by the viral protease VP4 (also named NS) to generate three polypeptides: pVP2, VP4, and VP3. Site-directed mutagenesis at 42 positions of the IPNV VP4 protein was performed to determine the active site and the important residues for the protease activity. Two residues (serine 633 and lysine 674) were critical for cleavage activity at both the pVP2-VP4 and the VP4-VP3 junctions. Wild-type activity at the pVP2-VP4 junction and a partial block (with an alteration of the cleavage specificity) at the VP4-VP3 junction were observed when replacement occurred at histidines 547 and 679. A similar observation was made when aspartic acid 693 was replaced by leucine, but wild-type activity and specificity were found when substituted by glutamine or asparagine. Sequence comparison between IPNV and two birnavirus (infectious bursal disease virus and Drosophila X virus) VP4s revealed that serine 633 and lysine 674 are conserved in these viruses, in contrast to histidines 547 and 679. The importance of serine 633 and lysine 674 is reminiscent of the protease active site of bacterial leader peptidases and their mitochondrial homologs and of the bacterial LexA-like proteases. Self-cleavage sites of IPNV VP4 were determined at the pVP2-VP4 and VP4-VP3 junctions by N-terminal sequencing and mutagenesis. Two alternative cleavage sites were also identified in the carboxyl domain of pVP2 by cumulative mutagenesis. The results suggest that VP4 cleaves the (Ser/Thr)-X-Ala / (Ser/Ala)-Gly motif, a target sequence with similarities to bacterial leader peptidases and herpesvirus protease cleavage sites. (+info)Expression of YAV proteins and vaccination against viral ascites among cultured juvenile yellowtail. (5/29)
Yellowtail ascites virus (YAV) is a member of the family Birnaviridae and causes viral ascites among juvenile yellowtail (Seriola quinqueradiata). We have reported the cloning and expression of two viral cDNAs, the first being segment A encoding a polyprotein of viral capsid proteins (VP2 and VP3) and a protease (NS), and the second being VP2-epitope encoding serotype-specific epitope region on VP2, using a baculovirus expression system. Another viral cDNA encoding a polyprotein of NS and VP3 was cloned and expressed in this study. For the expression of NS/VP3 (YAV nt 1626 to 3066) in insect cells a 31-kDa protein, corresponding to VP3 was detected, indicating an appropriate posttranslational processing of NS/VP3 polypeptide by NS protease itself. The analysis of the N-terminal amino acid sequence of this protein showed that NS protease may cleave an Ala-Ser bond. A study of the potential for vaccination of yellowtail fry by injection of insect cell lysates infected with baculovirus, containing either cDNA of segment A, VP2-epitope, or NS/VP3 was undertaken. Only a vaccination with cell lysates infected with a recombinant virus carrying the full length of YAV segment A gene demonstrated approximately the same effect as that of inactivated YAV. This result suggested that all proteins VP2, VP3, and NS are required for an effective vaccination. (+info)First isolation of an aquatic birnavirus from farmed and wild fish species in Australia. (6/29)
During routine sampling and testing, as part of a systematic surveillance program (the Tasmanian Salmonid Health Surveillance Program), an aquatic birnavirus was isolated from 'pin-head' (fish exhibiting deficient acclimatisation on transfer to saltwater) Atlantic salmon Salmo salar, approximately 18 mo old, farmed in net-pens located in Macquarie Harbour on the west coast of Tasmania, Australia. The isolate grows readily in a range of fish cell lines including CHSE-214, RTG-2 and BF-2 and is neutralised by a pan-specific rabbit antiserum raised against infectious pancreatic necrosis virus (IPNV) Ab strain and by a commercial pan-specific IPNV-neutralising monoclonal antibody. Presence of the virus was not associated with gross clinical signs. Histopathological examination revealed a range of lesions particularly in pancreatic tissue. The virus was localised in pancreas sections by immunoperoxidase staining using the polyclonal antiserum and by electron microscopy. Examination by electron microscopy demonstrated that the virus isolated in cell culture (1) belongs to the family Birnaviridae, genus Aquabirnaviridae; (2) was ultrastructurally and antigenically similar to virus identified in the index fish; (3) is related to IPNV. Western blot analysis using the polyclonal rabbit antiserum confirmed the cross-reactions between various aquatic birnavirus isolates. In addition, PCR analysis of isolated viral nucleic acid from the index case indicated that the virus is more closely related to IPNV fr21 and N1 isolates than to other birnavirus isolates available for comparison. Sampling of other fish species within Macquarie Harbour has demonstrated that the virus is present in several other species of fish including farmed rainbow trout Oncorhynchus mykiss, wild flounder Rhombosolea tapirina, cod Pseudophycis sp., spiked dogfish Squalus megalops and ling Genypterus blacodes. (+info)Genome sequence of a VP2/NS junction region of pillar cell necrosis virus (PCNV) in cultured Japanese eel Anguilla japonica. (7/29)
Pillar cell necrosis virus (PCNV) is an aquatic birnavirus that was isolated from farmed Japanese eel experiencing mass mortality. In this study, a VP2/NS junction region in genome segment A of PCNV was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) and sequenced. The VP2/NS region in PCNV had the highest homology with that of a strain Ab of infectious pancreatic necrosis virus (IPNV). This result revealed that PCNV belongs to birnavirus genogroup II. (+info)Blotched snakehead virus is a new aquatic birnavirus that is slightly more related to avibirnavirus than to aquabirnavirus. (8/29)
By different approaches, we characterized the birnavirus blotched snakehead virus (BSNV). The sequence of genomic segment A revealed the presence of two open reading frames (ORFs): a large ORF with a 3,207-bp-long nucleotide sequence and a 417-nucleotide-long small ORF located within the N-terminal half of the large ORF, but in a different reading frame. The large ORF was found to encode a polyprotein cotranslationally processed by the viral protease VP4 to generate pVP2 (the VP2 precursor), a 71-amino-acid-long peptide ([X]), VP4, and VP3. The two cleavage sites at the [X]-VP4 and VP4-VP3 junctions were identified by N-terminal sequencing. We showed that the processing of pVP2 generated VP2 and several small peptides (amino acids [aa] 418 to 460, 461 to 467, 468 to 474, and 475 to 486). Two of these peptides (aa 418 to 460 and 475 to 486) were positively identified in the viral particles with 10 additional peptides derived from further processing of the peptide aa 418 to 460. The results suggest that VP4 cleaves multiple Pro-X-Ala downward arrow Ala motifs, with the notable exception of the VP4-VP3 junction. Replacement of the members of the predicted VP4 catalytic dyad (Ser-692 and Lys-729) confirmed their indispensability in the polyprotein processing. The genomic segment B sequence revealed a single large ORF encoding a putative polymerase, VP1. Our results demonstrate that BSNV should be considered a new aquatic birnavirus species, slightly more related to IBDV than to IPNV. (+info)Birnaviridae is a family of non-enveloped, double-stranded RNA viruses that infect a wide range of animals, including birds, fish, and insects. The name Birnaviridae comes from the combination of the words "bird" and "RNA." These viruses are characterized by their icosahedral symmetry and bi-segmented genome, which is composed of two segments of double-stranded RNA.
The two genomic segments of Birnaviridae encode for several viral proteins, including the viral capsid protein and the RNA-dependent RNA polymerase (RdRp) that is responsible for replicating the viral genome. The family Birnaviridae includes several important veterinary pathogens, such as infectious bursal disease virus (IBDV), which causes a highly contagious and often fatal disease in young chickens, and aquabirnavirus, which infects various species of fish and can cause significant economic losses in the aquaculture industry.
Birnaviruses are typically transmitted through fecal-oral routes or by ingestion of contaminated food or water. They replicate in the cytoplasm of infected cells and can induce a range of clinical signs, depending on the specific virus and host species. In addition to their veterinary importance, birnaviruses are also of interest to researchers studying the fundamental biology of RNA viruses and their interactions with host cells.
An Aquabirnavirus is a type of double-stranded RNA virus that belongs to the family Birnaviridae. The name "Aquabirnavirus" reflects its prevalence in aquatic environments. These viruses are known to infect a variety of hosts, including fish and crustaceans. They have an icosahedral symmetry and a non-enveloped capsid. The genome of Aquabirnaviruses consists of two segments of double-stranded RNA. The larger segment encodes the viral polyprotein, while the smaller segment encodes the viral capsid protein. Aquabirnaviruses are relatively resistant to environmental factors such as heat, pH, and organic solvents, which allows them to persist in aquatic environments for extended periods.
Birnaviridae is a family of viruses that includes several species known to cause infections in animals, including birds and fish. The most well-known member of this family is the infectious bursal disease virus (IBDV), which primarily affects young chickens and causes a highly contagious disease known as Gumboro disease.
Infection with IBDV can result in a range of symptoms, including diarrhea, depression, ruffled feathers, and decreased appetite. In severe cases, the virus can cause significant mortality in infected flocks. Other members of the Birnaviridae family include viruses that infect salmonids (such as infectious pancreatic necrosis virus) and other bird species.
Transmission of Birnaviridae viruses typically occurs through direct contact with infected animals or their feces, as well as through contaminated food and water sources. Prevention and control measures for these infections include good biosecurity practices, vaccination, and proper nutrition and management.
Infectious Bursal Disease Virus (IBDV) is a highly contagious avian virus that primarily affects the bursa of Fabricius in young chickens, leading to an immunosuppressive disease known as Gumboro disease. The bursa of Fabricius is a vital organ for the development and maturation of B cells, which are crucial for the immune system's response to infections.
IBDV is a non-enveloped, double-stranded RNA virus belonging to the Birnaviridae family. It has two serotypes, with serotype 1 being responsible for the majority of outbreaks and being highly pathogenic, while serotype 2 is less virulent and causes mild or asymptomatic infections.
The virus targets and destroys the B cells in the bursa, leading to a weakened immune system that makes the affected chickens more susceptible to secondary bacterial and viral infections. The disease can cause significant economic losses in the poultry industry due to high mortality rates, decreased feed conversion efficiency, and reduced egg production.
Vaccination is an effective prevention strategy against IBDV, with both live and inactivated vaccines available for use in chickens. Good biosecurity measures, such as strict sanitation practices and limiting the movement of birds and people between farms, can also help prevent the spread of the virus.
Infectious pancreatic necrosis (IPN) is a viral disease that primarily affects young salmonid fish, such as salmon and trout. The IPN virus, also known as Salmonid alphavirus (SAV), is the causative agent of this disease. It is an enveloped, positive-sense single-stranded RNA virus belonging to the family Alphaflexiviridae and genus Alphavirus.
The IPN virus primarily targets the exocrine pancreas, leading to severe necrosis (tissue death) in infected fish. The infection can also spread to other organs, including the liver, kidney, and heart. Infected fish may exhibit various clinical signs such as lethargy, loss of appetite, darkening of the skin, abnormal swimming behavior, and exophthalmia (bulging eyes).
The IPN virus is highly contagious and can be transmitted horizontally through direct contact with infected fish or their bodily fluids. It can also be vertically transmitted from infected broodstock to their offspring. The disease can have significant economic impacts on the aquaculture industry, leading to high mortality rates in affected fish populations.
Prevention and control measures for IPN include vaccination of broodstock and fry, biosecurity practices, and quarantine procedures. There is no specific treatment for IPN, and antibiotics are generally not effective against viral infections. Supportive care, such as providing optimal water quality and nutrition, can help affected fish recover from the disease.
Viral structural proteins are the protein components that make up the viral particle or capsid, providing structure and stability to the virus. These proteins are encoded by the viral genome and are involved in the assembly of new virus particles during the replication cycle. They can be classified into different types based on their location and function, such as capsid proteins, matrix proteins, and envelope proteins. Capsid proteins form the protein shell that encapsulates the viral genome, while matrix proteins are located between the capsid and the envelope, and envelope proteins are embedded in the lipid bilayer membrane that surrounds some viruses.
Molecular sequence data refers to the specific arrangement of molecules, most commonly nucleotides in DNA or RNA, or amino acids in proteins, that make up a biological macromolecule. This data is generated through laboratory techniques such as sequencing, and provides information about the exact order of the constituent molecules. This data is crucial in various fields of biology, including genetics, evolution, and molecular biology, allowing for comparisons between different organisms, identification of genetic variations, and studies of gene function and regulation.
RNA-dependent RNA polymerase, also known as RNA replicase, is an enzyme that catalyzes the production of RNA from an RNA template. It plays a crucial role in the replication of certain viruses, such as positive-strand RNA viruses and retroviruses, which use RNA as their genetic material. The enzyme uses the existing RNA strand as a template to create a new complementary RNA strand, effectively replicating the viral genome. This process is essential for the propagation of these viruses within host cells and is a target for antiviral therapies.
An encyclopedia is a comprehensive reference work containing articles on various topics, usually arranged in alphabetical order. In the context of medicine, a medical encyclopedia is a collection of articles that provide information about a wide range of medical topics, including diseases and conditions, treatments, tests, procedures, and anatomy and physiology. Medical encyclopedias may be published in print or electronic formats and are often used as a starting point for researching medical topics. They can provide reliable and accurate information on medical subjects, making them useful resources for healthcare professionals, students, and patients alike. Some well-known examples of medical encyclopedias include the Merck Manual and the Stedman's Medical Dictionary.
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