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At least 19 recordsLinked to original sources

PubMed2005

Complete genome sequence of the grouper iridovirus and comparison of genomic organization with those of other iridoviruses.

The complete DNA sequence of grouper iridovirus (GIV) was determined using a whole-genome shotgun approach on virion DNA. The circular form genome was 139,793 bp in length with a 49% G + C content. It contained 120 predicted open reading frames (ORFs) with coding capacities ranging from 62 to 1,268 amino acids. A total of 21% (25 of 120) of GIV ORFs are conserved in the other five sequenced iridovirus genomes, including DNA replication, transcription, nucleotide metabolism, protein modification, viral structure, and virus-host interaction genes. The whole-genome nucleotide pairwise comparison showed that GIV virus was partially colinear with counterparts of previously sequenced ranaviruses (ATV and TFV). Besides, sequence analysis revealed that GIV possesses several unique features which are different from those of other complete sequenced iridovirus genomes: (i) GIV is the first ranavirus-like virus which has been sequenced completely and which infects fish other than amphibians, (ii) GIV is the only vertebrate iridovirus without CpG sequence methylation and lacking DNA methyltransferase, (iii) GIV contains a purine nucleoside phosphorylase gene which is not found in other iridoviruses or in any other viruses, (iv) GIV contains 17 sets of repeat sequence, with basic unit sizes ranging from 9 to 63 bp, dispersed throughout the whole genome. These distinctive features of GIV further extend our understanding of molecular events taking place between ranavirus and its hosts and the iridovirus evolution.

Animals↗

PubMed2002

Comparative analysis of the genome and host range characteristics of two insect iridoviruses: Chilo iridescent virus and a cricket iridovirus isolate.

The iridovirus isolate termed cricket iridovirus (CrIV) was isolated in 1996 from Gryllus campestris L. and Acheta domesticus L. (both Orthoptera, Gryllidae). CrIV DNA shows distinct DNA restriction patterns different from those known for Insect iridescent virus type 6 (IIV-6). This observation led to the assumption that CrIV might be a new species within the family Iridoviridae. CrIV can be transmitted perorally to orthopteran species, resulting in specific, fatal diseases. These species include Gryllus bimaculatus L. and the African migratory locust Locusta migratoria migratorioides (Orthoptera, Acrididae). Analysis of genomic and host range properties of this isolate was carried out in comparison to those known for IIV-6. Host range studies of CrIV and IIV-6 revealed no differences in the peroral susceptibility in all insect species and developmental stages tested to date. Different gene loci of the IIV-6 genome were analyzed, including the major capsid protein (274L), thymidylate synthase (225R), an exonuclease (012L), DNA polymerase (037L), ATPase (075L), DNA ligase (205R) and the open reading frame 339L, which is homologous to the immediate-early protein ICP-46 of frog virus 3. The average identity of the selected viral genes and their gene products was found to be 95.98 and 95.18% at the nucleotide and amino acid level, respectively. These data led to the conclusion that CrIV and IIV-6 are not different species within the Iridoviridae family and that CrIV must be considered to be a variant and/or a novel strain of IIV-6.

Amino Acid Sequence↗

PubMed2002

Viral DNA sequences of genes encoding the ATPase and the major capsid protein of tropical iridovirus isolates which are pathogenic to fishes in Japan, South China Sea and Southeast Asian countries.

Tropical iridovirus infection causes severe epizootic resulting in mass mortalities and large economic losses in freshwater ornamental fishes cultured in Southeast Asian countries, in wild fish seedlings captured in South China Sea, and in marine fishes farmed in Japan, Singapore, and Thailand. All of tropical iridovirus-infected fishes histopathologically showed the systemic formation of inclusion body-bearing cells and necrosis of virus-infected splenocytes and hematopoietic cells. We designed primer sets for the ATPase gene and the major capsid protein (MCP) gene and sequenced the PCR products derived from 5 iridovirus isolates from sea bass in South China Sea, red sea bream in Japan, brown-spotted grouper with a grouper sleepy disease in Thailand, dwarf gourami from Malaysia and African lampeye from Sumatra Island, Indonesia. The ATPase gene and the MCP gene of these 5 viral isolates were highly homologous (> 95.8%, > 94.9% identity, respectively) and the deduced amino acid sequences of the ATPase and the MCP were also highly identical (> 98.1%, > 97.2% identity, respectively). Based on the high homology, these 5 isolates of tropical iridovirus from various fishes in geographically different regions were determined to have a single origin and to be native to Southeast Asian regions. However, these sequences were far different from those of members of the genera Ranavirus, Lymphocystivirus and Iridovirus in the Family Iridoviridae. We propose a new genus "Tropivirus" for tropical iridovirus in the Family Iridoviridae.

Adenosine Triphosphatases↗

PubMed2003

Cladistic analysis of iridoviruses based on protein and DNA sequences.

Cladograms of iridoviruses were inferred from bootstrap analysis of molecular data sets comprising all published protein and DNA sequences of the major capsid protein, ATPase and DNA polymerase genes of members of the Iridoviridae family Iridovirus. All data sets yielded cladograms supporting the separation of the Iridovirus, Ranavirus and Lymphocystivirus genera, and the cladogram based on data derived from major capsid proteins further divided both the Iridovirus and Ranavirus genera into two groups. Tests of alternative hypotheses of topological constraints were also performed to further investigate relationships between infectious spleen and kidney necrosis virus (ISKNV), an unclassified fish iridovirus for which the complete genome sequence data is available, and other iridoviruses. Cladograms inferred and results of Shimodaira-Hasegawa tests indicated that ISKNV is more closely related to the Ranavirus genus than it is to the other genera of the family.

Amino Acid Sequence↗

PubMed1994

Comparative studies of iridoviruses: further support for a new classification.

Changes in the classification of invertebrate iridoviruses (IVs) (Iridoviridae) have recently been proposed (Williams and Cory, 1994). The previous system of naming isolates according to the host and sequence of discovery (IV type 1, IV2, IV3, etc.) is not adequate for the purposes of taxonomy, since iridovirus isolates may infect many species, including hosts from diverse invertebrate orders. The new system of invertebrate iridovirus nomenclature, as with several other virus families, is based on geographical origin. Proposals have been made, based on DNA hybridization and other characteristics, by which invertebrate iridovirus isolates can be assigned to one of four recognized complexes, or considered as candidates for alternative assignations. This study reports comparative data on the DNA of 14 invertebrate iridovirus isolates used in the Williams and Cory study plus the two type vertebrate iridoviruses, frog virus 3 and flounder lymphocystis disease virus. DNA studies support the validity of assigning several isolates a common name and of grouping the known isolates into four complexes. The detection of such complexes is in broad agreement with previous serological studies. A previously undescribed isolate (San Miguel IV) obtained from the lepidopteran pest Anticarsia gemmatalis (Lep.: Noctuidae) has been initially characterized following the procedures recommended by Williams and Cory. DNA hybridization and Southern blot analysis identified this isolate as a new member of the Polyiridovirus complex. The San Miguel IV MSP gene was identified and a central fragment of ca. 719 bp was recovered by PCR amplification. The restriction endonuclease profiles (5 enzymes) of this isolate were distinct from others previously described.

Animals↗

PubMed2004

Complete genomic DNA sequence of rock bream iridovirus.

Iridovirus is a causative agent of epizootics among cultured rock bream (Oplegnathus fasciatus) in Korea. Here, we report the complete genomic sequence of rock bream iridovirus (RBIV). The genome of RBIV was 112080 bp long and contained at least 118 putative open reading frames (ORFs), and its genome organization was similar to that of infectious spleen and kidney necrosis virus (ISKNV). Of the RBIV's 118 ORFs, 85 ORFs showed 60-99% amino acid identity to those of ISKNV. Phylogenetic analysis of major capsid protein (MCP), DNA repair protein RAD2, and DNA polymerase type-B family indicated that RBIV is closely related to red sea bream iridovirus (RSIV), Grouper sleepy disease iridovirus (GSDIV), Dwarf gourami iridovirus (DGIV), and ISKNV. The genome sequence provides useful information concerning the evolution and divergence of iridoviruses in cultured fish.

Animals↗

PubMed1999

Comparison of the major capsid protein genes, terminal redundancies, and DNA-DNA homologies of two New Zealand iridoviruses.

Molecular comparisons were carried out on two iridoviruses isolated from endemic sympatric New Zealand pasture pests. These viruses, Costelytra zealandica iridescent virus (CzIV/IV16) and Wiseana iridescent virus (WIV/IV9), belong to the same virus genus but it is not known how related they are. The major capsid protein (MCP) gene from each virus was located, sequenced, and compared to the homologous gene from other iridoviruses. The MCP genes of WIV and CzIV were similar to each other (87.9% amino acid similarity) and to other iridovirus MCP genes. The MCP genes of both WIV and CzIV were most homologous to the MCP gene from Tipula iridescent virus (TIV/IV1), with amino acid similarities of 92.3 and 88.3% respectively. The genomes of WIV and CzIV were compared to other invertebrate iridoviruses using solution DNA-DNA hybridisations. Even after reducing the annealing stringency conditions hybridisation ratios never exceeded 10% indicating there is little sequence conservation between iridovirus genomes. Estimates of the size of terminal redundancies were also calculated for these viruses using pulsed-field agarose gel electrophoresis. These values ranged from 0 to 8%. These studies indicate that WIV and CzIV have distinct genomes and that the genus Iridovirus is comprised of a group of genetically diverse viruses.

Amino Acid Sequence↗

PubMed2003

Evidence for the evolution of ascoviruses from iridoviruses.

Ascoviruses (family Ascoviridae) are large, enveloped, double-stranded (ds)DNA viruses that attack lepidopteran larvae and pupae, and are unusual in that they are transmitted by parasitic wasps during oviposition. Previous comparisons of DNA polymerase sequences from vertebrate and invertebrate viruses suggested that ascoviruses are closely related to iridoviruses. This relationship was unexpected because these viruses differ markedly in virion symmetry, genome configuration and cellular pathology. Here we present evidence based on sequence comparisons and phylogenetic analyses of a greater range of ascovirus proteins and their homologues in other large dsDNA viruses that ascoviruses evolved from iridoviruses. Consensus trees for the major capsid protein, DNA polymerase, thymidine kinase and ATPase III from representative ascoviruses, algal viruses (family Phycodnaviridae), vertebrate and invertebrate iridoviruses (family Iridoviridae) and African swine fever virus (ASFV; family Asfarviridae) showed that ascovirus proteins clustered most closely with those of the lepidopteran iridovirus Chilo iridescent virus (CIV) (Invertebrate iridescent virus 6). Moreover, analysis of the presence or absence of homologues of an additional 50 proteins encoded in the genome of Spodoptera frugiperda ascovirus (SfAV-1a) showed that about 40 % occurred in CIV, with lower percentages encoded by the genomes of, respectively, vertebrate iridoviruses, phycodnaviruses and ASFV. The occurrence of three of these genes in SfAV-1a but not CIV was indicative of the evolutionary differentiation of ascoviruses from invertebrate iridoviruses.

Adenosine Triphosphatases↗

PubMed2003

Strain variation in an emerging iridovirus of warm-water fishes.

Although iridoviruses vary widely within and among genera with respect to their host range and virulence, variation within iridovirus species has been less extensively characterized. This study explores the nature and extent of intraspecific variation within an emerging iridovirus of North American warm-water fishes, largemouth bass virus (LMBV). Three LMBV isolates recovered from three distinct sources differed genetically and phenotypically. Genetically, the isolates differed in the banding patterns generated from amplified fragment length polymorphism analysis but not in their DNA sequences at two loci of different degrees of evolutionary stability. In vitro, the isolates replicated at identical rates in cell culture, as determined by real-time quantitative PCR of viral particles released into suspension. In vivo, the isolates varied over fivefold in virulence, as measured by the rate at which they induced mortality in juvenile largemouth bass. This variation was reflected in the viral loads of exposed fish, measured using real-time quantitative PCR; the most virulent viral strain also replicated to the highest level in fish. Together, these results justify the designation of these isolates as different strains of LMBV. Strain variation in iridoviruses could help explain why animal populations naturally infected with iridovirus pathogens vary so extensively in their clinical responses to infection. The results of this study are especially relevant to emerging iridoviruses of aquaculture systems and wildlife.

Animals↗

PubMed2005

Characterization of an iridovirus detected from cultured turbot Scophthalmus maximus in Korea.

Juvenile turbot Scophthalmus maximus that became sick during an outbreak of disease at mariculture facilities at Go-Chang, Korea, in 2003, were examined to identify the cause of the disease. The fish had pale body color, an enlarged abdomen, protruding eyes, an enlarged spleen and kidney, and pale gills and/or liver. Histopathogical examination revealed basophilic enlarged cells in the kidney, spleen, gills, heart, stomach, intestine, liver, pancreas and skin. Hexagonal viral particles with a diameter of 136 to 159 nm were observed in the enlarged cells. A specific 1299 bp fragment of the major capsid protein (MCP) gene of the turbot iridovirus (TBIV) was amplified by PCR. Sequence homology was greater than 93.76% between the MCP gene in TBIV and the same gene in 5 viruses in the tentatively proposed genus Tropivirus (family Iridoviridae): red sea bream iridovirus, sea bass iridovirus, grouper sleepy disease iridovirus, African lampeye iridovirus and dwarf gourami iridovirus. These results suggest that the virus detected from turbot is similar to the proposed genus Tropivirus.

Animals↗

PubMed1997

Molecular characterization, sequence analysis, and taxonomic position of newly isolated fish iridoviruses.

Within the past decade, iridoviruses have been identified as the causative agents of systemic disease in a variety of commercially and recreationally important fish. Here we examine nine iridoviruses from fish, reptiles, and amphibians and demonstrate that all isolates were more similar to frog virus 3, the type species of the genus Ranavirus, than to lymphocystis disease virus, the type species of the genus Lymphocystivirus. Comparison of viral protein synthesis profiles, restriction endonuclease digestion patterns, and the amino acid sequence of the major capsid protein indicated that iridoviruses isolated from the same geographic region were similar, if not identical, whereas viruses from different areas were distinct. Moreover, using primers complementary to the conserved major capsid protein, we found that both PCR and RT-PCR successfully amplified virus-specific nucleic acid from all nine isolates. These studies demonstrate that the piscine iridoviruses examined here were members of the genus Ranavirus, and suggest that surveys of pathogenic "fish viruses" may need to include neighboring amphibian and reptilian populations. In addition, the results indicate that PCR readily identified vertebrate iridoviruses and suggest that PCR will be useful in the diagnosis of fish disease.

Amino Acid Sequence↗

PubMed2001

Complete genome analysis of the mandarin fish infectious spleen and kidney necrosis iridovirus.

The nucleotide sequence of the infectious spleen and kidney necrosis virus (ISKNV) genome was determined and found to comprise 111,362 bp with a G+C content of 54.78%. It contained 124 potential open reading frames (ORFs) with coding capacities ranging from 40 to 1208 amino acids. The analysis of the amino acid sequences deduced from the individual ORFs revealed that 35 of the 124 potential gene products of ISKNV show significant homology to functionally characterized proteins of other species. Some of the putative gene products of ISKNV showed significant homologies to proteins in the GenBank/EMBL/DDBJ databases including enzymes and structural proteins involved in virus replication, transcription, protein modification, and virus-host interaction. In addition, one major repeated sequence showing significant homology to the Red Sea bream iridovirus (RSIV) genome was identified. Based on the information obtained from biological properties (including histopathology, tissue tropisms, natural host range, and geographic distribution), physiochemical and physical properties, and genome analysis, we suggest that ISKNV, RSIV, sea bass iridovirus, grouper iridovirus, and African lampeye iridovirus may belong to a new genus of the Iridoviridae family and are tentatively referred to as cell hypertrophy iridoviruses.

Amino Acid Sequence↗

PubMed2005

Development and characterization of a new tropical marine fish cell line from grouper, Epinephelus coioides susceptible to iridovirus and nodavirus.

The development and characterization of a new tropical marine fish cell line (GS), derived from the spleen of orange spotted grouper, Epinephelus coioides is described. The GS cells grow well in Leibovitz's L-15 medium supplemented with 10% foetal bovine serum, and have been subcultured more than 200 times. The optimal growth temperature was 27 degrees C. The GS cell culture consisted of mostly fibroblastic cells. The modal diploid chromosome number was 48. GS cell cultures showed advanced cytopathic effects after infection with a pathogenic grouper iridovirus (Singapore grouper iridovirus, SGIV) or with a grouper nodavirus (Epinephelus tauvina nervous necrosis virus, ETNNV). Analysis by transmission electron microscopy showed a large number of SGIV and ETNNV particles in the cytoplasm of virus-infected cells, respectively, indicative of high sensitivity to these two viruses. Immunofluorescence microscopy showed that iridovirus-infected GS cells reacted strongly with monoclonal antibody against the grouper iridovirus. It is suggested that the GS cell line has good potential as a diagnostic tool for isolation and propagation of iridovirus and nodavirus. When the GS cells were transfected with pEGFP vector DNA, significant fluorescent signals were observed suggesting that the GS cell line can be used as a useful tool for transgenic and genetic manipulation studies.

Animals↗

PubMed1998

Is the major capsid protein of iridoviruses a suitable target for the study of viral evolution?

Iridoviruses are large cytoplasmic DNA viruses that are specific for different insect or vertebrate hosts. The major structural component of the non-enveloped icosahedral virus particles is the major capsid protein (MCP) which appears to be highly conserved among members of the family Iridoviridae, Phycodnaviridae, and African swine fever virus. The amino acid sequences of the known MCPs were used in comparative analyses to elucidate the phylogenic relationships between different cytoplasmic DNA viruses including three insect iridoviruses (Tipula iridescent virus, Simulium iridescent virus, Chilo iridescent virus), seven vertebrate iridoviruses isolated either from fish (lymphocystis disease virus, rainbow trout virus, European catfish virus, doctor fish virus), amphibians (frog virus 3), or reptiles (turtle virus 3, turtle virus 5), one member of the family Phycodnaviridae (Paramecium bursaria Chlorella virus type 1), and African swine fever virus. These analyses revealed that the amino acid sequence of the MCP is a suitable target for the study of viral evolution since it contains highly conserved domains, but is sufficiently diverse to distinguish closely related iridovirus isolates. Furthermore the results suggest that a substantial revision of the taxonomy of iridoviruses based on molecular phylogeny is required.

Amino Acid Sequence↗

PubMed2006

Novel iridovirus in a nautilus (Nautilus spp.).

Intracytoplasmic inclusion bodies suggestive of iridovirus infection were observed in formalin-fixed, paraffin-embedded tissues from a nautilus (Nautilus spp.) that died without premonitory signs. Transmission electron microscopy revealed enveloped, hexagonal, viral particles that measured approximately 176 nm in diameter. Virions contained a dense central core and morphology typical of iridoviruses. Extracted DNA was amplified using primers homologous to conserved iridovirus sequences. The amplicons were cloned, sequenced, and determined to be approximately 60% similar to reported amphibian iridovirus sequences. A polymerase chain reaction-generated digoxigenin probe was used to detect viral nucleic acid in tissue sections by DNA in situ hybridization and high-affinity cytochemistry. The detected nucleic acid corresponded to the inclusion bodies observed microscopically. This represents a novel iridovirus of mollusks.

Animals↗

PubMed2002

Iridovirus disease in two ornamental tropical freshwater fishes: African lampeye and dwarf gourami.

Many species of ornamental freshwater fishes are imported into Japan from all over the world. We found African lampeye Aplocheilichthys normani and dwarf gourami Colisa lalia suffering from an iridovirus infection just after being imported by tropical fish wholesalers from Singapore. African lampeye were cultured on the Indonesian Island of Sumatra and dwarf gourami were cultured in Malaysia before export. Diseased fishes displayed distinct histopathological signs of iridovirus infection: systemic appearance of inclusion body-bearing cells, and necrosis of splenocytes and hematopoietic cells. Electron microscopy revealed viral particles (African lampeye:180 to 200 nm in edge to edge diameter; dwarf gourami: 140 to 150 nm in diameter) in an inclusion body within the cytoplasm of inclusion body-bearing cells as well as in the cytoplasm of necrotized cells. Experimental infection with an iridovirus isolate from African lampeye (ALIV) revealed pathogenicity of ALIV to African lampeye and pearl gourami Trichogaster leeri. Polymerase chain reaction (PCR) products from ALIV and an iridovirus isolate from dwarf gourami (DGIV) using iridovirus-specific primers were indistinguishable. The nucleotide sequence of PCR products derived from ALIV (696 base pairs) and DGIV (701 base pairs) had 95.3% identity. These results indicate that ALIV and DGIV have a single origin.

Animals↗

PubMed1999

Characterization of a new iridovirus isolated from crickets and investigations on the host range

Typical signs of an iridovirus infection were observed in two species of fatally diseased crickets, Gryllus campestris L. and Acheta domesticus L. (Orthoptera, Gryllidae). The infection was manifested by hypertrophy and bluish iridescence of the affected fat body cells. Electron microscope investigations led to the identification of a new iridovirus, which was termed cricket iridovirus (CrIV). In negatively stained preparations the size of the icosahedral virus particles ranged from 151 nm (side-side) to 167 nm (apex-apex). Assembly of virions occurred in the cytoplasm of hypertrophied fat body cells, where they often accumulated in paracrystalline arrays. Genetic analyses of purified viral DNA using a variety of restriction enzymes revealed that CrIV is distinct from all other known iridoviruses that have been isolated from insects and reported so far. In host range studies it was shown that CrIV can be transmitted perorally to other orthopteran species, causing characteristic symptoms and fatal disease. These species include Gryllus bimaculatus L. (Orthoptera, Gryllidae) and the African migratory locust Locusta migratoria migratorioides (R. & F.) (Orthoptera, Acrididae), which represents one of the most important pest insects in developing countries, as well as the cockroaches Blattella germanica L. and Blatta orientalis L. (both Orthoptera, Blattidae). Consequently, the isolation and characterization of this new cricket iridovirus is of particular interest in view of its possible use in biological or integrated control. Copyright 1999 Academic Press.

Journal Article↗

PubMed2004

Sequence variation in the gene encoding the major capsid protein of Korean fish iridoviruses.

Ten iridoviruses were isolated from cultured fish from various regions in Korea; 7 from rock bream, 1 from red sea bream, 1 from sea bass, and 1 from rockfish. The full open-reading frame (ORF) encoding the major capsid protein (MCP) (1362 bp) from ten iridoviruses were sequenced and the nucleotide sequences were phylogenetically analyzed. Phylogenetic analysis revealed that the ten Korean isolates were classified into one cluster. However, their sequences were not identical and, based on the nucleotide sequence variation, they could be further divided into two subgroups. While nine Korean isolates were similar to the Japanese isolate red sea bream iridovirus (RSIV), one isolate was distinct from other iridovirus isolates. These results suggest that a diversity of iridoviruses exist in Korea and that a new variant strain has emerged.

Amino Acid Sequence↗