Invertebrate Iridoviruses: A Glance over the Last Decade (original) (raw)
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Natural invertebrate hosts of iridoviruses (Iridoviridae)
Neotropical Entomology, 2008
Neotropical Entomology 37 : 615-632 (2008) Hospederos Naturales de los Iridovirus de Invertebrados RESUMEN -Los virus iridiscentes de invertebrados (VIIs) son virus icosaedrales de ADN que infectan a invertebrados, principalmente insectos e isópodos terrestres en hábitats húmedos y acuáticos. Búsquedas extensivas de bases de datos resultaron en la identifi cación de 79 artículos científi cos, los cuales reportaron 108 especies de invertebrados infectados naturalmente por iridovirus. De estos, 103 (95%) fueron artrópodos y los otros fueron moluscos, un anélido y un nematodo. Nueve especies fueron de hábitats marinos. De las 99 especies no marinas, 49 fueron terrestres y 50 fueron acuáticas, especialmente los estadios acuáticos de dípteros (44 especies). La abundancia de infecciones en especies de Aedes, Ochlerotatus y Psorophora se contrasta marcadamente con la escasez de casos en especies de Anopheles, Culex y Culiseta. Reportes de infecciones de los isópodos terrestres son numerosos (19 especies), aunque la diversidad de los VII que los infectan es desconocida. Se han reportado infecciones por VIIs de todos los continentes, excepto Antártica, pero se notan pocos ejemplos de África, Asia y Latinoamérica. La mayoría de los artículos señala que las infecciones patentes son poco comunes, mientras que las infecciones enmascaradas (subletales) pueden ser comunes en algunas especies. La relación entre el tamaño de la partícula y el color iridiscente concuerda con la teoría óptica en casi todos los casos. Veinticuatro de los VIIs de insectos han sido caracterizados parcialmente y solo dos de éstos han sido secuenciados completamente. Demuestro que el ritmo de publicación sobre los VIIs ha disminuido en los últimos 15 años, señalo varias conclusiones y sugerencias de la lista de especies de huéspedes y presento algunas recomendaciones para la investigación futura con este grupo de patógenos.
The genomic diversity and phylogenetic relationship in the family iridoviridae
Viruses, 2010
The Iridoviridae family are large viruses (∼120-200 nm) that contain a linear double-stranded DNA genome. The genomic size of Iridoviridae family members range from 105,903 bases encoding 97 open reading frames (ORFs) for frog virus 3 to 212,482 bases encoding 211 ORFs for Chilo iridescent virus. The family Iridoviridae is currently subdivided into five genera: Chloriridovirus, Iridovirus, Lymphocystivirus, Megalocytivirus, and Ranavirus. Iridoviruses have been found to infect invertebrates and poikilothermic vertebrates, including amphibians, reptiles, and fish. With such a diverse array of hosts, there is great diversity in gene content between different genera. To understand the origin of iridoviruses, we explored the phylogenetic relationship between individual iridoviruses and defined the core-set of genes shared by all members of the family. In order to further explore the evolutionary relationship between the Iridoviridae family repetitive sequences were identified and compar...
Genome sequence of a crustacean iridovirus, IIV31, isolated from the pill bug, Armadillidium vulgare
Journal of General Virology, 2014
Members of the family Iridoviridae are animal viruses that infect only invertebrates and poikilothermic vertebrates. The invertebrate iridovirus 31 (IIV31) was originally isolated from adult pill bugs, Armadillidium vulgare (class Crustacea, order Isopoda, suborder Oniscidea), found in southern California on the campus of the University of California, Riverside, USA. IIV31 virions are icosahedral, have a diameter of about 135 nm, and contain a dsDNA genome 220.222 kbp in length, with 35.09 mol % G+C content and 203 ORFs. Here, we describe the complete genome sequence of this virus and its annotation. This is the eighth genome sequence of an IIV reported.
Genome of Invertebrate Iridescent Virus Type 3 (Mosquito Iridescent Virus
Journal of Virology, 2006
Iridoviruses (IVs) are classified into five genera: Iridovirus and Chloriridovirus, whose members infect invertebrates, and Ranavirus, Lymphocystivirus, and Megalocytivirus, whose members infect vertebrates. Until now, Chloriridovirus was the only IV genus for which a representative and complete genomic sequence was not available. Here, we report the genome sequence and comparative analysis of a field isolate of Invertebrate iridescent virus type 3 (IIV-3), also known as mosquito iridescent virus, currently the sole member of the genus Chloriridovirus. Approximately 20% of the 190-kbp IIV-3 genome was repetitive DNA, with DNA repeats localized in 15 apparently noncoding regions. Of the 126 predicted IIV-3 genes, 27 had homologues in all currently sequenced IVs, suggesting a genetic core for the family Iridoviridae. Fifty-two IIV-3 genes, including those encoding DNA topoisomerase II, NAD-dependent DNA ligase, SF1 helicase, IAP, and BRO protein, are present in IIV-6 (Chilo iridescent virus, prototype species of the genus Iridovirus) but not in vertebrate IVs, likely reflecting distinct evolutionary histories for vertebrate and invertebrate IVs and potentially indicative of genes that function in aspects of virus-invertebrate host interactions. Thirty-three IIV-3 genes lack homologues in other IVs. Most of these encode proteins of unknown function but also encode IIV3-053L, a protein with similarity to DNA-dependent RNA polymerase subunit 7; IIV3-044L, a putative serine/threonine protein kinase; and IIV3-080R, a protein with similarity to poxvirus MutT-like proteins. The absence of genes present in other IVs, including IIV-6; the lack of obvious colinearity with any sequenced IV; the low levels of amino acid identity of predicted proteins to IV homologues; and phylogenetic analyses of conserved proteins indicate that IIV-3 is distantly related to other IV genera.
The Molecular Biology of Frog Virus 3 and other Iridoviruses Infecting Cold-Blooded Vertebrates
Frog virus 3 (FV3) is the best characterized member of the family Iridoviridae. FV3 study has provided insights into the replication of other family members, and has served as a model of viral transcription, genome replication, and virus-mediated host-shutoff. Although the broad outlines of FV3 replication have been elucidated, the precise roles of most viral proteins remain unknown. Current studies using knock down (KD) mediated by antisense morpholino oligonucleotides (asMO) and small, interfering RNAs (siRNA), knock out (KO) following replacement of the targeted gene with a selectable marker by homologous recombination, ectopic viral gene expression, and recombinant viral proteins have enabled researchers to systematically ascertain replicativeand virulence-related gene functions. In addition, the application of molecular tools to ecological studies is providing novel ways for field biologists to identify potential pathogens, quantify infections, and trace the evolution of ecologically important viral species. In this review, we summarize current studies using not only FV3, but also other iridoviruses infecting ectotherms. As described below, general principles ascertained using FV3 served as a model for the family, and studies utilizing other ranaviruses and megalocytiviruses have confirmed and extended our understanding of iridovirus replication. Collectively, these and future efforts will elucidate molecular events in viral OPEN ACCESS Viruses 2011, 3 1960
Comparative Genomics of an Emerging Amphibian Virus
G3: Genes|Genomes|Genetics, 2015
Ranaviruses, a genus of the Iridoviridae, are large double-stranded DNA viruses that infect cold-blooded vertebrates worldwide. Ranaviruses have caused severe epizootics in commercial frog and fish populations, and are currently classified as notifiable pathogens in international trade. Previous work shows that a ranavirus that infects tiger salamanders throughout Western North America (Ambystoma tigrinum virus, or ATV) is in high prevalence among salamanders in the fishing bait trade. Bait ATV strains have elevated virulence and are transported long distances by humans, providing widespread opportunities for pathogen pollution. We sequenced the genomes of 15 strains of ATV collected from tiger salamanders across western North America and performed phylogenetic and population genomic analyses and tests for recombination. We find that ATV forms a monophyletic clade within the rest of the Ranaviruses and that it likely emerged within the last several thousand years, before human activities influenced its spread. We also identify several genes under strong positive selection, some of which appear to be involved in viral virulence and/or host immune evasion. In addition, we provide support for the pathogen pollution hypothesis with evidence of recombination among ATV strains, and potential bait-endemic strain recombination. KEYWORDS Ranavirus Ambystoma tigrinum virus range expansion Emerging infectious diseases are increasingly appreciated as a leading health concern for humans, wildlife, and economically important agricultural populations (Daszak et al. 2000; Smith et al. 2009). Indeed, pathogens are now listed as a leading cause of species' declines and extinctions (De Castro and Bolker 2005; Smith et al. 2006). Ranaviruses, a genus of the Iridoviridae, are globally-distributed pathogens of amphibians, reptiles and commercial fish species (Chinchar 2002; Miller et al. 2011). These large, double-stranded DNA viruses are considered emerging due to increases in incidence and geographic range over the last 30 years (Daszak et al. 2000; Chinchar 2002; Miller et al. 2011). Ranaviruses are now classified as notifiable pathogens in international trade because of their effects on commercial and wildlife populations (Schloegel et al. 2010). Pathogen pollution is of particular concern, whereby non-native ranavirus strains are introduced into host populations with which they have no evolutionary history, potentially leading to large scale epizootics (Cunningham et al. 2003). Phylogenetic analyses provide several lines of evidence for host switching events among the 10 completely sequenced Ranavirus genomes (Jancovich et al. 2010; Abrams et al. 2013). These analyses suggest that TFV (tiger frog virus) and GIV (grouper iridovirus) are likely strains of the geographically-distant FV3 (frog virus 3) and SGIV (Singapore grouper iridovirus), respectively (Chinchar et al. 2011). In addition, strains isolated from different vertebrate classes, such as STIV (soft-shelled turtle iridovirus; Reptilia) and FV3 (Amphibia) are very similar in genome organization, and, like RGV (Lei et al. 2012), both have truncated versions of the viral homolog of eukaryotic translational initiation factor 2a [vIF-2a (Huang et al. 2009; Tan et al. 2004)]. Additional phylogenetic analyses, combined with comparisons of genomic organization, suggest that the most recent common ancestor of all ranaviruses was a strain that infected fish (Jancovich et al. 2010; Chinchar et al. 2011). Evidence of a fishamphibian host switch comes from the strong collinearity of EHNV (epizootic hematopoietic necrosis virus; isolated from rainbow trout) and ATV (Ambystoma tigrinum virus, isolated from salamanders). A possible mechanism for host switching among vertebrate classes was inferred from evidence of positive selection on 12 ranavirus genes; six of these genes were apparently acquired as a result of host switches (Abrams et al. 2013).
BMC Genomics, 2009
Background: Soft-shelled turtle iridovirus (STIV) is the causative agent of severe systemic diseases in cultured soft-shelled turtles (Trionyx sinensis). To our knowledge, the only molecular information available on STIV mainly concerns the highly conserved STIV major capsid protein. The complete sequence of the STIV genome is not yet available. Therefore, determining the genome sequence of STIV and providing a detailed bioinformatic analysis of its genome content and evolution status will facilitate further understanding of the taxonomic elements of STIV and the molecular mechanisms of reptile iridovirus pathogenesis.
Novel Iridovirus in a Nautilus (Nautilus Spp.)
Journal of Veterinary Diagnostic Investigation, 2006
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.