A comparison of six cypovirus isolates by cross-hybridisation of their dsRNA genome segments

Abstract

Genetic relationships between the genome segments of six cypovirus (CPV) isolates were analysed by RNA cross-hybridisation. These included three type 1 viruses and single isolates of types 2, 5 and 12, which collectively are identical to those previously compared by serology and electrophoresis [Mertens et al. (1989), J Gen Virol 70: 173-185]. Since only genome segment 10 of three cypovirus types and segments 8 and 9 of a single virus strain (of type 1) have currently been sequenced, this initial study provides some additional information on sequence variation/similarity in each of the ten genome segments. The RNA of the type 1 viruses showed high levels of cross-hybridisation. Significant but much lower levels of cross-hybridisation were detected between type 1 and the related type 12 CPV. However, only very low levels of cross-hybridisation were detected between the other pairs of viruses. Apart from evidence of a slightly higher level of sequence similarity between the largest segments, the RNA sequence appeared to vary uniformly across the whole genome. There was no evidence for any type specific RNA sequences restricted to individual genome segment(s). The sequence variation, reflected in the levels of RNA sequence similarity and cross hybridisation, correlates well with serological data, showing large differences between CPV types and supports the continued use of electropherotype as one of the 'species parameters' for the classification of cypoviruses.

Molecular and biological characterization of a Cypovirus from the mosquito Culex restuans

“…After ingestion of the inclusion bodies by the insect, the alkaline pH and proteinases of the intestinal track break down the polyhedrin and release the virions, which enter and replicate in the cytoplasm of midgut epithelial cells (Mertens et al, 1999(Mertens et al, , 2004bZhang et al, 1999). Most CPV infections produce chronic disease with low mortality although some are pathogenic (Mertens et al, 1999(Mertens et al, , 2004b.…”

“…The RNA segments are composed of plus-strand mRNA and its complementary minus-strand in an end to end based-pair conWguration with the exception of a protruding 5Ј cap on the plus-strand (Furuichi and Miura, 1975). Based on the migration pattern of the genome segments on a 1% agarose or 3-5% polyacrylamide gel, CPVs are classiWed into 17 distinct electrophoretypes (Mertens et al, 1989(Mertens et al, , 1999(Mertens et al, , 2004bPayne and Mertens, 1983;Payne and Rivers, 1976;Shapiro et al, 2005).…”

Morphological and Molecular Characterization of a Cypovirus ( Reoviridae ) from the Mosquito Uranotaenia sapphirina (Diptera: Culicidae)

“…Different cypovirus "types" were initially identified on the basis of differences in the migration patterns of their genome segments during polyacrylamide gel electrophoresis, i.e., electropherotypes (22). Subsequent studies showed a good correlation between electropherotype and the grouping of strains on the basis of serological properties (18) or RNA cross-hybridization (17,20). It has recently been shown that, in addition to the RNA migration patterns, nucleotide sequences, for example, those of genome segment 10 (Seg-10; the polyhedrin gene), can be used to distinguish different Cypovirus species (20).…”

Biological and molecular studies of a cypovirus from the black fly Simulium ubiquitum (Diptera: Simuliidae)

“…Sixteen diVerent virus species (Cypovirus-1 to have already been formally recognized within the genus Cypovirus, family Reoviridae (Mertens et al, 2004). These diVerent species can be distinguished by diVerences in the migration patterns of their dsRNAs during electrophoresis, variations in RNA sequences (both in the coding regions and conserved terminal regions) and by antigenic variation in the viral proteins (Mertens et al, 2004(Mertens et al, , 1999Payne and Rivers, 1976). Further Cypovirus species 18,and 19) have been proposed, based on isolates from mosquitoes (CPV-17- Green et al, 2006;Shapiro et al, 2005) and from the winter moth Operophtera brumata (CPV-18 and 19-Graham et al, 2006) that have been characterized and compared to the existing species by electropherotype analysis and sequencing of the viral genome.…”