Astroviruses

Abstract

Astroviruses are positive‐sense, single‐stranded RNA viruses encoding three open reading frames. However, the exact number of processed proteins remains unknown. Originally identified as a common cause of childhood diarrhoea, especially in children under 2 years of age, astroviruses are now recognised as an infection of diverse mammals and birds. Disease can range from asymptomatic to mild, self‐limiting gastroenteritis, as well as nephritis, hepatitis and encephalitis in certain host species. Astrovirus pathogenicity and immune response is only poorly characterised and may differ between mammalian and avian species. Given the wide host range and extensive genetic diversity among species, it is not surprising that classifying astrovirus family members remains a challenge. In this article, the current knowledge of astroviruses is reviewed, including their replication, viral evolution, pathogenesis and immune response.

Key Concepts

  • The Astroviridae are a complex family of emerging viruses.
  • Astrovirus pathogenesis and host immune responses remain an underexplored area of investigation.
  • Astroviruses may be more prevalent in humans than previously recognised.
  • Astroviridae classification and nomenclature for newly identified genotypes are needed.
  • Astroviruses are associated with more than gastroenteritis.

Keywords: gastroenteritis; Astroviridae; genetic diversity; recombination; food and waterborne; emerging; non‐enveloped virus; positive‐strand RNA virus

Figure 1. Electron micrograph of Human astrovirus from diarrhoeal faeces. Particles have a smooth margin and display a surface five‐ or six‐pointed star motif. Bar, 100 nm.
Figure 2. Phylogenetic relationships within the Astroviridae family. The predicted nucleotide sequences of ICTV reference (a) mammalian or (b) avian astrovirus genomes were aligned using ClustalW and the phylogenetic tree generated using the neighbour‐joining algorithm in the MEGA6 programme.
Figure 3. Organisation of the human astrovirus genome. Virus RNA is 6800 bases in length and contains three ORFs. ORFs 1a and 1b are expressed from the full‐length virus RNA genome; ORF1b is translated as a 1a–1b fusion following ribosome frameshifting. ORF2 is translated from a sub‐genomic promoter. Key: (a) in/del = insertion/deletion; RDRP = RNA‐dependent RNA polymerase; VPg = viral protein attached to the genome. (b) Light blue box = nucleotide binding motif; purple box = coiled coil domain blue box = transmembrane helices; v‐Pro = viral protease; red box = in/del. (c) The primary ORF2 product contains two domains; the highly conserved N‐terminal domain, which forms the core of the capsid (blue), and the hypervariable C‐terminal domain, which forms the spike (purple). The basic and acidic regions of the VP90 are highly conserved among all astroviruses. Adapted from Schultz‐Cherry (2013) with kind permission of Springer Science + Business Media New York 2013.
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References

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Further Reading

Brown JR, Morfopoulou S, Hubb J, et al. (2015) Astrovirus VA1/HMO‐C: an increasingly recognized neurotropic pathogen in immunocompromised patients. Clinical Infectious Diseases. Jan 7. pii: ciu940. [Epub ahead of print].

Mendez E and Arias CF (2013) Astroviruses. In: Knipe DM and Howley P, (eds). Fields Virology, pp. 293–298. Wolters Kluwer: Philadelphia.

Taboada B, Espinoza MA, Isa P, et al. (2014) Is there still room for novel viral pathogens in pediatric respiratory tract infections? PLoS One 9 (11): e113570.

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How to Cite close
Schultz‐Cherry, Stacey(Apr 2015) Astroviruses. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001006.pub3]