Summary auto-generated
This study presents a comparative sequence analysis of Coltivirus isolates from the Americas, Europe, and Asia to establish taxonomic classification within the genus Coltivirus (family Reoviridae). Researchers analyzed double-stranded RNA genomic segments from Colorado tick fever (CTF) virus and related isolates using RT-PCR, direct sequencing, and phylogenetic analysis. American isolates (CTF strains) and European isolates (Eyach virus) were grouped together as Coltivirus group A, subdivided into species A1 (American) and A2 (European) based on sequence identity and primer compatibility. Asian isolates from Indonesia (JKT strains) and China (Banna virus) formed a distinct Coltivirus group B, further divided into two species: B1 (JKT-7075) and B2 (JKT-6423, JKT-6969, JKT-7043, Banna). Protein analysis revealed conserved domains including dsRNA-binding motifs in group B segment 8 (subgroup B1) and segment 12 (subgroup B2), and a conserved amino acid pattern in segment 7 matching protein kinase catalytic domains. The study provides molecular criteria for establishing polythetic species classification within Coltivirus and demonstrates significant evolutionary divergence between geographic groups.
Key findings
- American and European coltiviruses form group A (comprising species A1 and A2), while Asian isolates form group B (comprising species B1 and B2), with minimal cross-group sequence homology
- Group A viruses share 65-68% to 67-56% nucleic acid identity between subgroups A1 and A2, while group B viruses within subgroup B2 show 83-98% identity in conserved segments
- Asian coltivirus group B genomes contain dsRNA-binding domains in segment proteins and conserved protein kinase-like catalytic motifs in segment 7
- Conserved inverted terminal repeats and specific terminal sequence motifs (GUAUA/UA/UU at 5' end and A/GCC/UGAC at 3' end) were identified in group B non-coding regions
- The G-C content of group B sequences (37-39%) is significantly lower than group A sequences (48.4-51.6%), supporting distinct evolutionary origins
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Abstract
H Attoui, RN Charrel, F Billoir, JF Cantaloube, P de Micco and X de Lamballerie
Laboratoire de Virologie Moleculaire, Tropicale et Transfusionnelle, Faculte de Medecine de Marseille, Universite de la Mediterranee, Marseille, France.
In this study, the basis for the classification of virus isolates grouped within the genus Coltivirus, family Reoviridae, is discussed. Sequences of dsRNA segments from American (segments 9-12), European (segment 12) and Asian (segments 7-12) isolates were characterized and polythetic criteria were defined for their taxonomic classification. These criteria (including sequence analysis) permitted the different species to be distinguished and classified into two groups. In both groups, subgroups were defined according to the degree of homology between the genomic sequences. American and European isolates are classified within group A, which includes subgroups A1 (Colorado tick fever virus species) and A2 (Eyach virus species). Asian isolates are classified in group B, which includes subgroups B1 (JKT-7075 virus species) and B2 (JKT-6423 virus species). The proteins encoded by the sequenced genomic segments were analysed. This allowed the identification of dsRNA binding domains in the proteins encoded by segment 8 of subgroup B1 isolates and segment 12 of subgroup B2 isolates. A conserved pattern of amino acids in segment 7 of group B isolates matched sequences found in the catalytic domains of protein kinases.