Summary auto-generated
This study compares bovine viral diarrhea virus (BVDV), a pestivirus, with flaviviruses to reassess viral classification. BVDV possesses a single-stranded RNA genome of approximately 4.3 × 10⁶ Mr lacking a 3' poly(A) tail, similar to flaviviruses but distinct from alphaviruses. The genome contains a single open reading frame encoding a precursor polyprotein processed into multiple proteins. While direct nucleotide and amino acid sequence comparisons revealed minimal extensive homology between BVDV and three flavivirus serological subgroups (yellow fever, dengue 2, and Japanese encephalitis viruses), the overall organization of protein-coding domains and hydropathic profiles showed striking similarity. Short, conserved amino acid sequences were identified in two non-structural proteins (p125 and p133), suggesting functional conservation. Based on these molecular features—including genome structure, expression strategy, protein organization, and hydropathic character—the authors propose that Pestivirus, represented by BVDV, should be reclassified from the Togaviridae family and instead established as a new genus of non-arthropod-borne viruses within the Flaviviridae family.
Key findings
- BVDV possesses molecular features characteristic of flaviviruses: a poly(A)-deficient single-stranded RNA genome with a single open reading frame encoding a polyprotein precursor
- Protein-coding domain organization and amino acid hydropathic profiles of BVDV closely parallel those of flaviviruses despite minimal direct sequence homology
- Conserved amino acid sequences in p125 (analogous to flavivirus NS3) and p133 (analogous to flavivirus NS5) suggest functional similarities in non-structural proteins
- The authors propose reclassifying Pestivirus as a new genus within the Flaviviridae family rather than remaining in the Togaviridae family
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Abstract
The molecular features of bovine viral diarrhoea virus (BVDV), a member of the Pestivirus genus currently classified in the Togaviridae, were examined for characteristics resembling those of the Flaviviridae family. Like flaviviruses, BVDV possesses a single-stranded RNA genome (approx. 4.3 x 106 Mr) deficient in a 3' poly(A) tract. This RNA has a single open reading frame spanning the length of the genome in the viral RNA sense (positive polarity), implying an expression strategy involving the processing of a precursor polyprotein. With the exception of several short but significant stretches of identical amino acids within two non-structural proteins, no extended regions of nucleotide or amino acid sequence homology between BVDV and representatives of three serological subgroups of mosquito-borne flaviviruses were noted. However, comparison of the organization of protein-coding domains along the genomes and the hydropathic profiles of amino acid sequences revealed pronounced similarities. It is proposed that Pestivirus, of which BVDV is the prototype member, should no longer be grouped in the Togaviridae family, but rather be considered a genus of non-arthropod-borne viruses within the Flaviviridae.