Infectious salmon anemia virus—Genetics and pathogenesis

Cottet, Luis; Rivas‐Aravena, Andrea; Martı́n, Marcelo Cortez-San; Sandino, Ana María; Spencer, Eugenio

doi:10.1016/j.virusres.2010.10.021

Cited by 46 publications

(29 citation statements)

References 76 publications

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“…We could not detect the rISAV genome in the supernatants of the cells in which the four vectors expressing the proteins of the RNPC were excluded from the transfection mix. These results strongly suggest that the putative functions proposed for the proteins encoded by segments 1, 2, and 4 are the subunits of the viral polymerase (57). Moreover, detection of EGFP vRNA within segment 6 in cell supernatant (Fig.…”

Section: Discussionsupporting

confidence: 54%

Development of a Reverse Genetic System for Infectious Salmon Anemia Virus: Rescue of Recombinant Fluorescent Virus by Using Salmon Internal Transcribed Spacer Region 1 as a Novel Promoter

Toro-Ascuy

Tambley

Beltrán

et al. 2015

Appl Environ Microbiol

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Infectious salmon anemia (ISA) is a serious disease of marine-farmed Atlantic salmon (Salmo salar) caused by ISA virus (ISAV), belonging to the genus Isavirus, family Orthomyxoviridae. There is an urgent need to understand the virulence factors and pathogenic mechanisms of ISAV and to develop new vaccine approaches. Using a recombinant molecular biology approach, we report the development of a plasmid-based reverse genetic system for ISAV, which includes the use of a novel fish promoter, the Atlantic salmon internal transcribed spacer region 1 (ITS-1). Salmon cells cotransfected with pSS-URG-based vectors expressing the eight viral RNA segments and four cytomegalovirus (CMV)-based vectors that express the four proteins of the ISAV ribonucleoprotein complex allowed the generation of infectious recombinant ISAV (rISAV). We generated three recombinant viruses, wild-type rISAV 901_09 and rISAVr S6-NotI-HPR containing a NotI restriction site and rISAV S6/EGFP-HPR harboring the open reading frame of enhanced green fluorescent protein (EGFP), both within the highly polymorphic region (HPR) of segment 6. All rescued viruses showed replication activity and cytopathic effect in Atlantic salmon kidney-infected cells. The fluorescent recombinant viruses also showed a characteristic cytopathic effect in salmon cells, and the viruses replicated to a titer of 6.5 ؋ 10 5 PFU/ml, similar to that of the wild-type virus. This novel reverse genetics system offers a powerful tool to study the molecular biology of ISAV and to develop a new generation of ISAV vaccines to prevent and mitigate ISAV infection, which has had a profound effect on the salmon industry. Infectious salmon anemia (ISA) is a disease that principally affects Atlantic salmon (Salmo salar), which has caused enormous losses to salmon farming worldwide (1, 2). ISA was first reported in 1984 in Norway (3) and subsequently was identified in Canada (4), Scotland (5), the United States (6), the Faroe Islands (Denmark) (6), and Chile (7). The etiological agent of this disease is the infectious salmon anemia virus (ISAV), a pleomorphic enveloped virus with a diameter of 45 to 140 nm, which belongs to the family Orthomyxoviridae (8). Its genome has 8 negative-polarity singlestranded RNA (ssRNA) segments that encode 10 proteins. Sequence similarity analyses of the genomes of different ISAV isolates show significant variation in the coding regions. In contrast, the untranslated regions (UTR) at both ends of each segment are highly conserved (9-11), as has been described for other orthomyxoviruses as well (e.g., influenza A and B viruses) (12).There is little knowledge at present about the functions of the ISAV proteins. Bioinformatic analyses of the sequences predict that segments 1, 2, and 4 encode the subunits of the RNA-dependent RNA polymerase (RdRp), analogous to PB2, PB1, and PA, respectively, of the influenza A virus. Segment 3 encodes the nucleoprotein (NP), which has been reported to have the capacity to bind ssRNA (13). For influenza virus, it has been shown that t...

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Section: Discussionsupporting

confidence: 54%

Development of a Reverse Genetic System for Infectious Salmon Anemia Virus: Rescue of Recombinant Fluorescent Virus by Using Salmon Internal Transcribed Spacer Region 1 as a Novel Promoter

Toro-Ascuy

Tambley

Beltrán

et al. 2015

Appl Environ Microbiol

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“…The enveloped virus particles are of 45-140 nm in diameter, however, highly pleiomorphic particles up to 700 nm in the longest dimension are occasionally observed. The genome organization is consistent with other members of the Orthomyxoviridae ; comprising of 8 segments of single stranded negative sense RNA ((-) ssRNA), in which each segment encodes one protein except segments 7 and 8, which encode two (European strains)/three (Canadian strains) and two proteins, respectively [8]. Four major structural proteins have been identified, including a 68 kDa nucleoprotein, a 22 kDa matrix protein, a 42 kDa surface glycoprotein named haemagglutinin-esterase protein with receptor-binding and receptor-destroying activity, and a 50 kDa surface glycoprotein with fusion activity, coded by genome segments 3, 8, 6, and 5, respectively.…”

Section: Introductionmentioning

confidence: 67%

Molecular phylodynamics and protein modeling of infectious salmon anemia virus (ISAV)

et al. 2011

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BackgroundISAV is a member of the Orthomyxoviridae family that affects salmonids with disastrous results. It was first detected in 1984 in Norway and from then on it has been reported in Canada, United States, Scotland and the Faroe Islands. Recently, an outbreak was recorded in Chile with negative consequences for the local fishing industry. However, few studies have examined available data to test hypotheses associated with the phylogeographic partitioning of the infecting viral population, the population dynamics, or the evolutionary rates and demographic history of ISAV. To explore these issues, we collected relevant sequences of genes coding for both surface proteins from Chile, Canada, and Norway. We addressed questions regarding their phylogenetic relationships, evolutionary rates, and demographic history using modern phylogenetic methods.ResultsA recombination breakpoint was consistently detected in the Hemagglutinin-Esterase (he) gene at either side of the Highly Polymorphic Region (HPR), whereas no recombination breakpoints were detected in Fusion protein (f) gene. Evolutionary relationships of ISAV revealed the 2007 Chilean outbreak group as a monophyletic clade for f that has a sister relationship to the Norwegian isolates. Their tMRCA is consistent with epidemiological data and demographic history was successfully recovered showing a profound bottleneck with further population expansion. Finally, selection analyses detected ongoing diversifying selection in f and he codons associated with protease processing and the HPR region, respectively.ConclusionsOur results are consistent with the Norwegian origin hypothesis for the Chilean outbreak clade. In particular, ISAV HPR0 genotype is not the ancestor of all ISAV strains, although SK779/06 (HPR0) shares a common ancestor with the Chilean outbreak clade. Our analyses suggest that ISAV shows hallmarks typical of RNA viruses that can be exploited in epidemiological and surveillance settings. In addition, we hypothesized that genetic diversity of the HPR region is governed by recombination, probably due to template switching and that novel fusion gene proteolytic sites confer a selective advantage for the isolates that carry them. Additionally, protein modeling allowed us to relate the results of phylogenetic studies with the predicted structures. This study demonstrates that phylogenetic methods are important tools to predict future outbreaks of ISAV and other salmon pathogens.

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“…While not much is known about the transcription/replication cycle of ISAV, it has been proposed to utilize mechanisms ( Fig. 1) similar to those of influenza virus (8,58), which includes the highly pathogenic influenza A (inf A) virus.…”

Section: Infectious Salmon Anemia Virus (Isav) Has Emerged As a Greatmentioning

confidence: 99%

Structural Characterization of the Viral and cRNA Panhandle Motifs from the Infectious Salmon Anemia Virus

Brinson

Szakal

Marino

2011

J Virol

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Infectious salmon anemia virus (ISAV) has emerged as a virus of great concern to the aquaculture industry since it can lead to highly contagious and lethal infections in farm-raised salmon populations. While little is known about the transcription/replication cycle of ISAV, initial evidence suggests that it follows molecular mechanisms similar to those found in other orthomyxoviruses, which include the highly pathogenic influenza A (inf A) virus. During the life cycle of orthomyxoviruses, a panhandle structure is formed by the pairing of the conserved 5 and 3 ends of each genomic RNA. This structural motif serves both as a promoter of the viral RNA (vRNA)-dependent RNA polymerase and as a regulatory element in the transcription/replication cycle. As a first step toward characterizing the structure of the ISAV panhandle, here we have determined the secondary structures of the vRNA and the cRNA panhandles on the basis of solution nuclear magnetic resonance (NMR) and thermal melting data. The vRNA panhandle is distinguished by three noncanonical U ⅐ G pairs and one U ⅐ U pair in two stem helices that are linked by a highly stacked internal loop. For the cRNA panhandle, a contiguous stem helix with a protonated C ⅐ A pair near the terminus and tandem downstream U ⅐ U pairs was found. The observed noncanonical base pairs and base stacking features of the ISAV RNA panhandle motif provide the first insight into structural features that may govern recognition by the viral RNA polymerase.

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Infectious salmon anemia virus—Genetics and pathogenesis

Cited by 46 publications

References 76 publications

Development of a Reverse Genetic System for Infectious Salmon Anemia Virus: Rescue of Recombinant Fluorescent Virus by Using Salmon Internal Transcribed Spacer Region 1 as a Novel Promoter

Development of a Reverse Genetic System for Infectious Salmon Anemia Virus: Rescue of Recombinant Fluorescent Virus by Using Salmon Internal Transcribed Spacer Region 1 as a Novel Promoter

Molecular phylodynamics and protein modeling of infectious salmon anemia virus (ISAV)

Structural Characterization of the Viral and cRNA Panhandle Motifs from the Infectious Salmon Anemia Virus

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