An Insect Nidovirus Emerging from a Primary Tropical Rainforest

Zirkel, Florian; Kurth, Andreas; Quan, Phenix-Lan; Briese, Thomas; Ellerbrok, Heinz; Pauli, Georg; Leendertz, Fabian H.; Lipkin, W. Ian; Ziebuhr, John; Drosten, Christian; Junglen, Sandra

The order Nidovirales comprises the families Coronaviridae (subfamilies Coronavirinae [CoV] and Torovirinae [ToV] ), as well as the monogeneric families Arteriviridae (ArV, genus Arterivirus) and Roniviridae (RoV, genus Okavirus) (17) . Nidoviruses have a wide range of hosts, including crustaceans (RoV) (18) , fish (ToV) (19) , birds (CoV) (20) , and a variety of mammals (ArV, CoV, and ToV) (17, (21) (22) (23) . With plus-stranded genomes between 26 and 32 kb, CoV, ToV, and RoV have the largest known RNA genomes and are referred to as "large" nidoviruses (17) . Genomes of the "small" nidoviruses (ArV) comprise 13 to 16 kb. All nidoviruses encode two replicase polyproteins, pp1a and pp1ab, encoded by open reading frame 1a (ORF1a) and ORF1b located at the 5= end of the genome and followed by genes encoding structural proteins and, in most cases, several accessory (nonessential) proteins. A distinctive feature of nidoviruses is their transcription strategy. Genes downstream of the replicase polyprotein gene are expressed from a nested set of 3=-coterminal subgenomic mRNAs (in Latin, nidus means nest) (24) (25) (26) (27) . In this study, analyses of subgenomic mRNAs and major features of genome organization and phylogenetic analysis were employed for a taxonomic classification of a novel insect nidovirus. The summation of results suggests the discovery of a previously unrecognized family within the order Nidovirales.