Birnaviridae

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Birnaviridae
Virus classification
Group:
Group III (dsRNA)
Family:
Birnaviridae
Genera

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Birnavirus RNA dependent RNA polymerase (VP1)
Identifiers
Symbol Birna_RdRp
Pfam PF04197
InterPro IPR007100
Birnavirus VP2 protein
File:PDB 2df7 EBI.jpg
crystal structure of infectious bursal disease virus vp2 subviral particle
Identifiers
Symbol Birna_VP2
Pfam PF01766
Pfam clan CL0055
InterPro IPR002662
Birnavirus VP3 protein
Identifiers
Symbol Birna_VP3
Pfam PF01767
InterPro IPR002663
Birnavirus VP4 protein
Identifiers
Symbol Birna_VP4
Pfam PF01768
InterPro IPR002664
MEROPS S50
Birnavirus VP5 protein
Identifiers
Symbol Birna_VP5
Pfam PF03042
InterPro IPR004284

Birnaviridae is a family of viruses. Salmonid fish, young sexually immature chickens, and insects serve as natural hosts. There are currently six species in this family, divided among 4 genera. Diseases associated with this family include: IPNV: infectious pancreatic necrosis in salmonid fish, causes significant losses to the aquaculture industry. chronic infection in adult, and acute viral disease in young salmonid fish.[1][2]

Birnaviridae proteins

The Birnaviridae genome encodes several proteins:

Birnaviridae RNA-directed RNA polymerase (VP1), which lacks the highly conserved Gly-Asp-Asp (GDD) sequence, a component of the proposed catalytic site of this enzyme family that exists in the conserved motif VI of the palm domain of other RNA-directed RNA polymerases.[3]

The large RNA segment, segment A, of birnaviruses codes for a polyprotein (N-VP2-VP4-VP3-C) [4] that is processed into the major structural proteins of the virion: VP2, VP3 (a minor structural component of the virus), and into the putative protease VP4.[4] VP4 protein is involved in generating VP2 and VP3.[4] recombinant VP3 is more immunogenic than recombinant VP2.[5]

Infectious pancreatic necrosis virus (IPNV), a birnavirus, is an important pathogen in fish farms. Analyses of viral proteins showed that VP2 is the major structural and immunogenic polypeptide of the virus.[6][7] All neutralizing monoclonal antibodies are specific to VP2 and bind to continuous or discontinuous epitopes. The variable domain of VP2 and the 20 adjacent amino acids of the conserved C-terminal are probably the most important in inducing an immune response for the protection of animals.[6]

Non structural protein VP5 is found in RNA segment A. The function of this small viral protein is unknown. It is believed to be involved in influencing apoptosis, but studies are not completely concurring. The protein can not be found in the virion.

Structure

Viruses in Birnaviridae are non-enveloped, with icosahedral and Single-shelled geometries, and T=13 symmetry. The diameter is around 70 nm. Genomes are linear and segmented, around 15.2.3-3kb in length. The genome codes for 5 to 6 proteins.[1]

Genus Structure Symmetry Capsid Genomic Arrangement Genomic Segmentation
Avibirnavirus Icosahedral T=13 Non-Enveloped Linear Segmented
Aquabirnavirus Icosahedral T=13 Non-Enveloped Linear Segmented
Blosnavirus Icosahedral T=13 Non-Enveloped Linear Segmented
Entomobirnavirus Icosahedral T=13 Non-Enveloped Linear Segmented

Life Cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the double-stranded RNA virus replication model. Double-stranded rna virus transcription is the method of transcription. Salmonid fish, young sexually immature chickens, and insects serve as the natural host. Transmission routes are contact.[1]

Genus Host Details Tissue Tropism Entry Details Release Details Replication Site Assembly Site Transmission
Avibirnavirus Birds None Cell receptor endocytosis Budding Cytoplasm Cytoplasm Contact
Aquabirnavirus Salmonid fish None Cell receptor endocytosis Budding Cytoplasm Cytoplasm Contact
Blosnavirus Blotched snakehead fish None Unknown Budding Cytoplasm Cytoplasm Unknown
Entomobirnavirus Insects: diptera None Cell receptor endocytosis Budding Cytoplasm Cytoplasm Unknown

Taxonomy

Group: dsRNA

Order: Unassigned

[2]

References

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External Links

This article incorporates text from the public domain Pfam and InterPro IPR002664

This article incorporates text from the public domain Pfam and InterPro IPR002663

This article incorporates text from the public domain Pfam and InterPro IPR004284

This article incorporates text from the public domain Pfam and InterPro IPR002662

This article incorporates text from the public domain Pfam and InterPro IPR007100

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