Flaviviridae

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Baltimore Classification

Higher order taxa

Viruses; ssRNA positive-strand viruses, no DNA stage; Flaviviridae

Genera

Flavivirus, Pestivirus, Hepacivirus

Description and Significance

Flaviviridae contains a myriad of viruses that cause disease in humans. Flaviviridae has a total of 69 pathogens in its rank. The family gets its name from Yellow Fever virus, a type virus of Flaviviridae; flavus means yellow in Latin.

The Flavivirus genus contains several nasty critters that include yellow fever virus, dengue fever virus, and Japanese encephalitis (JE) virus. The pestivirus genus has three serotypes of bovine viral diarrhea, but no human pathogens are yet known. Genus Hepacivirus consists of hepatitis C virus and its relatives. (source: Stanford.edu)

Genome Structure

The genome of Flaviviridae is not segmented and contains a single molecule of linear positive-sense, single-stranded RNA. The complete genome is 9500-12500 nucleotides long. The 5'-end of the genome has a methylated nucleotide cap, or genome-linked protein (VPg). The 3'- terminus has no poly (A) tract but the poly (A) tract is present in some strains of tick-born encephalitis complex of flaviviruses. (source: ICTV dB Descriptions)

Virion Structure of a Flaviviridae

The virions of flaviviridae consist of an envelope and a nucleocapsid. The virus capsid is enveloped. The virions ar spherical to pleomorphic and measures 40-60 nm in diameter. There are small spikes surrounded by a prominent fringe that make up the surface projections. The capsid is round and exhibits a polyhedral symmetry. The core is isometric and has a diameter of 25-30 nm. The capsids can be penetrated by stain and some appear dark in the center. (source: ICTV dB Descriptions)

Reproduction Cycle of a Flaviviridae in a Host Cell

During the replication process, the entire flavivirus genomes is translated as a single polyprotein which is then cleaved into the mature proteins. The complementary (-)strand RNA is synthesized by NS proteins and used as a template for genomic progeny RNA synthesis. Assembly occurs during budding, characteristically into cytoplasmic vacuoles rather than at the cell surface. The release of the virus occurs during cell lyses. (source: Microbiology@Leicester: Flaviviruses)

Viral Ecology & Pathology

References

Stanford.edu

ICTV dB Descriptions