Nidoviruses are a group of positive‐sense, enveloped RNA viruses that infect a variety of vertebrates. They are associated with both overt and asymptomatic diseases in their natural hosts.

Keywords: coronaviruses; arteriviruses; toroviruses; molecular biology; pathogenesis

Figure 1.

The genome organization of nidoviruses. The genomic open reading frames (ORFs) encoding structural proteins are lightly shaded; those encoding nonstructural proteins are solid. The ORFs are drawn to scale in the correct reading frame. The size of the Berne virus (BEV) ORF rep1a is estimated. The BEV genome isolated in 1972 carries the remnants of an HE gene but does not express an HE protein. Further isolates may carry a functional HE gene, as has been reported by Cornelissen et al.. IBV, infectious bronchitis virus; MHV, murine hepatitis virus; HCV, human coronavirus; EAV, equine arteritis virus.

Figure 2.

The replicase gene of nidoviruses. The replicase gene is illustrated as two open reading frames (ORFs) that overlap (rep1a and rep1b in Figure ). The ORFs are drawn to scale. Shaded boxes represent conserved domains. The domains are defined in terms of their putative functions. 3CCP, 3C‐like cysteine proteinase; 3CSP, 3C‐like serine proteinase; C/H, cysteine–histidine motif; HEL, NTPase/helicase; PCP, papain‐like cysteine proteinase; POL, polymerase. IBV, infectious bronchitis virus; MHV, murine hepatitis virus; HCV, human coronavirus; BEV, Berne virus; EAV, equine arteritis virus.

Figure 3.

The translation strategy of nidoviruses. The figure illustrates the genome organization of (a) murine hepatitis virus and (b) equine arteritis virus (EAV), the structural relationship of the genomic and subgenomic mRNAs and the positions of the junction sites. RNA sequences (or open reading frames) encoding nonstructural proteins are represented by solid boxes; open reading frames encoding structural proteins are lightly shaded. 7mG represents a 5′‐cap structure preceding the leader sequence; AAA represents a 3′‐polyadenylate tract. The translation product(s) of the individual mRNAs are indicated.



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Further Reading

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Lai MMC and Cavanagh D (1997) The molecular biology of coronaviruses. Advances in Virus Research 48: 1–100.

Plagemann PWG (1996) Lactate dehydrogenase‐elevating virus and related viruses. In: Fields BN, Knipe DM, Howley PM et al. (eds) Fields Virology, 3rd edn, pp. 1105–1120. Philadelphia: Lippincott‐Raven.

Siddell SG and Snijder EJ (1998) Coronaviruses, toroviruses and arteriviruses. In: Mahy BWJ and Collier L (eds) Topley and Wilson'Microbiology and Microbial Infections, 5th edn, vol. 1, pp. 463–484. London: Edward Arnold.

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Ziebuhr, John, and Siddell, Stuart(Jul 2003) Nidoviruses. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001016]