Summary auto-generated
Taura syndrome virus (TSV), which devastates farmed Pacific white shrimp (Penaeus vannamei) in the Americas, was characterized and definitively classified as a member of the Picornaviridae family. Researchers purified TSV isolates from Ecuador and Hawaii and determined the virus is a 31-32 nm icosahedral particle containing single-stranded RNA of approximately 9 kb that is polyadenylated at the 3' end. The viral capsid comprises three major polypeptides (55, 40, and 24 kDa) and one minor polypeptide (58 kDa), with a buoyant density of 1.338 g/ml in cesium chloride. Both isolates were shown to be identical in biophysical and biological properties. Infectivity assays demonstrated that whole virus particles caused 60-64% mortality in specific pathogen-free shrimp within 48 hours, with characteristic histological lesions of Taura syndrome. Extracted viral RNA also retained infectivity, confirming the genome's role as messenger RNA. The presence of virions in shrimp hemolymph during acute infection indicates systemic disease spread.
Key findings
- TSV is a 31-32 nm icosahedral non-enveloped virus containing ~9 kb polyadenylated single-stranded RNA, definitively classified in family Picornaviridae
- The viral capsid contains three major polypeptides (24, 40, 55 kDa) and one minor polypeptide (58 kDa), with total composition ~85% protein and 15% RNA
- Hawaiian and Ecuadorian TSV isolates are identical in biophysical, biochemical, and biological characteristics
- Both whole virus particles and extracted viral RNA are infectious, causing 40-64% mortality in shrimp with characteristic acute-phase histological lesions
- Virions circulate systemically in shrimp hemolymph during acute phase infection, indicating disseminated disease spread
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Abstract
The causative agent of Taura syndrome (TS) was recognized in 1994 to be viral in nature and tentatively classified as belonging to either the family Picornaviridae or Nodaviridae. The work reported here has led to a more definitive classification of this new penaeid virus. Located within the cytoplasm of infected cuticular epithelial cells of penaeid shrimp, the virus is a 31 to 32 nm icosahedral particle with a buoyant density of 1.338+/-0.001 g/ml. Three major (55, 40 and 24 kDa) and one minor (58 kDa) polypeptides constitute its proteinic capsid. Its genome contains a single molecule of ssRNA, which is polyadenylated at the 3' end and approximately 9 kb in length. Based on these characteristics, we believe that TS virus should be included in the family Picornaviridae. Ecuadorian and Hawaiian TS virus isolates were found to be identical in their biophysical, biochemical and biological characteristics, and should be considered as the same virus.