Genus Coltivirus (family Reoviridae): genomic and morphologic characterization
of Old World and New World viruses.

Attoui H, Mohd JF, Biagini P, Cantaloube JF, de MP, Murphy FA, de LX.

Unite des Virus Emergents, Universite de la Mediterranee and EFS
Alpes-Meditertanee, Marseille, France.

We report a genomic and morphologic study of the European Eyach (EYA) virus
(genus Coltivirus, family Reoviridae) and a comparative analysis with the
American Colorado tick fever (CTF) virus (the type species of the genus). The
previously established, but distant, antigenic relationship between these
viruses was strengthened by genetic findings (presence of cognate genes, amino
acid identity between 55 and 88%, similar conserved terminal motifs, suspected
read-through phenomenon in segment 9 of both viruses) and by indistinguishable
ultramicroscopic morphologies. Moreover, putative constitutive modifying enzyme
activities were suspected to be carried out by homologous viral proteins
(RNA-dependent RNA polymerase, methyl/guanylyl transferase, NTPase). These
findings, together with the comparative analysis to genomes of southeast Asian
isolates, support the recent classification of arboviruses with 12 segments of
dsRNA within two distinct genera (genus Coltivirus and genus Seadornavirus) and
raise interesting questions about the evolutionary origins of coltiviruses. The
previously proposed hypothesis that EYA virus was derived from an ancestral
virus introduced in Europe with the migration of lagomorphs from North-America,
would imply a divergence date between American and European isolates of over 50
million years ago (MYA). This analysis allows for the first time to propose an
evolutionary rate for virus dsRNA genomes which was found to be in the order of
10(-8) to 10(-9) mutations/nt/year, a rate similar to that of dsDNA genomes.

PMID: 11958454 [PubMed - in process]