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Viruses, Volume 3, Issue 11 (November 2011), Pages 2025-2373

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Research

Jump to: Review

Open AccessArticle Baculovirus Induced Transcripts in Hemocytes from the Larvae of Heliothis virescens
Viruses 2011, 3(11), 2047-2064; doi:10.3390/v3112047
Received: 2 September 2011 / Revised: 19 October 2011 / Accepted: 19 October 2011 / Published: 28 October 2011
Cited by 18 | PDF Full-text (1560 KB)
Abstract
Using RNA-seq digital difference expression profiling methods, we have assessed the gene expression profiles of hemocytes harvested from Heliothis virescens that were challenged with Helicoverpa zea single nucleopolyhedrovirus (HzSNPV). A reference transcriptome of hemocyte-expressed transcripts was assembled from 202 million 42-base tags by combining [...] Read more.
Using RNA-seq digital difference expression profiling methods, we have assessed the gene expression profiles of hemocytes harvested from Heliothis virescens that were challenged with Helicoverpa zea single nucleopolyhedrovirus (HzSNPV). A reference transcriptome of hemocyte-expressed transcripts was assembled from 202 million 42-base tags by combining the sequence data of all samples, and the assembled sequences were then subject to BLASTx analysis to determine gene identities. We used the fully sequenced HzSNPV reference genome to align 477,264 Illumina sequence tags from infected hemocytes in order to document expression of HzSNPV genes at early points during infection. A comparison of expression profiles of control insects to those lethally infected with HzSNPV revealed differential expression of key cellular stress response genes and genes involved in lipid metabolism. Transcriptional regulation of specific insect hormones in baculovirus-infected insects was also altered. A number of transcripts bearing homology to retroviral elements that were detected add to a growing body of evidence for extensive invasion of errantiviruses into the insect genome. Using this method, we completed the first and most comprehensive gene expression survey of both baculoviral infection and host immune defense in lepidopteran larvae. Full article
(This article belongs to the Special Issue Insect Viruses)
Open AccessArticle Activation of LTRs from Different Human Endogenous Retrovirus (HERV) Families by the HTLV-1 Tax Protein and T-Cell Activators
Viruses 2011, 3(11), 2146-2159; doi:10.3390/v3112146
Received: 20 September 2011 / Accepted: 22 October 2011 / Published: 2 November 2011
Cited by 12 | PDF Full-text (1149 KB)
Abstract
Human endogenous retroviruses (HERVs) represent approximately 8% of our genome. HERVs influence cellular gene expression and contribute to normal physiological processes such as cellular differentiation and morphogenesis. HERVs have also been associated with certain pathological conditions, including cancer and neurodegenerative diseases. As [...] Read more.
Human endogenous retroviruses (HERVs) represent approximately 8% of our genome. HERVs influence cellular gene expression and contribute to normal physiological processes such as cellular differentiation and morphogenesis. HERVs have also been associated with certain pathological conditions, including cancer and neurodegenerative diseases. As HTLV-1 causes adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and has been shown to modulate host gene expression mainly through the expression of the powerful Tax transactivator, herein we were interested in looking at the potential modulation capacity of HTLV-1 Tax on HERV expression. In order to evaluate the promoter activity of different HERV LTRs, pHERV-LTR-luc constructs were co-transfected in Jurkat T-cells with a Tax expression vector. Tax expression potently increased the LTR activity of HERV-W8 and HERV-H (MC16). In parallel, Jurkat cells were also stimulated with different T-cell-activating agents and HERV LTRs were observed to respond to different combination of Forskolin, bpV[pic] a protein tyrosine phosphatase inhibitor, and PMA. Transfection of expression vectors for different Tax mutants in Jurkat cells showed that several transcription factors including CREB appeared to be important for HERV-W8 LTR activation. Deletion mutants were derived from the HERV-W8 LTR and the region from −137 to −123 was found to be important for LTR response following Tax expression in Jurkat cells, while a different region was shown to be required in cells treated with activators. Our results thus demonstrated that HTLV-1 Tax activates several HERV LTRs. This raises the possibility that upregulated HERV expression could be involved in diseases associated with HTLV-1 infection. Full article
(This article belongs to the Special Issue Recent Developments in HTLV Research)
Open AccessArticle N-Terminally Myristoylated Feline Foamy Virus Gag Allows Env-Independent Budding of Sub-Viral Particles
Viruses 2011, 3(11), 2223-2237; doi:10.3390/v3112223
Received: 29 August 2011 / Revised: 4 November 2011 / Accepted: 4 November 2011 / Published: 14 November 2011
Cited by 6 | PDF Full-text (1768 KB)
Abstract
Foamy viruses (FVs) are distinct retroviruses classified as Spumaretrovirinae in contrast to the other retroviruses, the Orthoretrovirinae. As a unique feature of FVs, Gag is not sufficient for sub-viral particle (SVP) release. In primate and feline FVs (PFV and FFV), particle [...] Read more.
Foamy viruses (FVs) are distinct retroviruses classified as Spumaretrovirinae in contrast to the other retroviruses, the Orthoretrovirinae. As a unique feature of FVs, Gag is not sufficient for sub-viral particle (SVP) release. In primate and feline FVs (PFV and FFV), particle budding completely depends on the cognate FV Env glycoproteins. It was recently shown that an artificially added N-terminal Gag myristoylation signal (myr-signal) overcomes this restriction in PFV inducing an Orthoretrovirus-like budding phenotype. Here we show that engineered, heterologous N-terminal myr-signals also induce budding of the distantly related FFV Gag. The budding efficiency depends on the myr-signal and its location relative to the N-terminus of Gag. When the first nine amino acid residues of FFV Gag were replaced by known myr-signals, the budding efficiency as determined by the detection of extracellular SVPs was low. In contrast, adding myr-signals to the intact N‑terminus of FFV Gag resulted in a more efficient SVP release. Importantly, budding of myr-Gag proteins was sensitive towards inhibition of cellular N-myristoyltransferases. As expected, the addition or insertion of myr-signals that allowed Env-independent budding of FFV SVPs also retargeted Gag to plasma membrane-proximal sites and other intracellular membrane compartments. The data confirm that membrane-targeted FV Gag has the capacity of SVP formation. Full article
(This article belongs to the Special Issue Feline Retroviruses)
Open AccessArticle Complete Sequence, Analysis and Organization of the Orgyia leucostigma Nucleopolyhedrovirus Genome
Viruses 2011, 3(11), 2301-2327; doi:10.3390/v3112301
Received: 23 August 2011 / Revised: 25 October 2011 / Accepted: 25 October 2011 / Published: 15 November 2011
Cited by 5 | PDF Full-text (389 KB)
Abstract
The complete genome of the Orgyia leucostigma nucleopolyhedrovirus (OrleNPV) isolated from the whitemarked tussock moth (Orgyia leucostigma, Lymantridae: Lepidoptera) was sequenced, analyzed, and compared to other baculovirus genomes. The size of the OrleNPV genome was 156,179 base pairs (bp) and [...] Read more.
The complete genome of the Orgyia leucostigma nucleopolyhedrovirus (OrleNPV) isolated from the whitemarked tussock moth (Orgyia leucostigma, Lymantridae: Lepidoptera) was sequenced, analyzed, and compared to other baculovirus genomes. The size of the OrleNPV genome was 156,179 base pairs (bp) and had a G+C content of 39%. The genome encoded 135 putative open reading frames (ORFs), which occupied 79% of the entire genome sequence. Three inhibitor of apoptosis (ORFs 16, 43 and 63), and five baculovirus repeated ORFs (bro-a through bro-e) were interspersed in the OrleNPV genome. In addition to six direct repeat (drs), a common feature shared among most baculoviruses, OrleNPV genome contained three homologous regions (hrs) that are located in the latter half of the genome. The presence of an F-protein homologue and the results from phylogenetic analyses placed OrleNPV in the genus Alphabaculovirus, group II. Overall, OrleNPV appears to be most closely related to group II alphabaculoviruses Ectropis obliqua (EcobNPV), Apocheima cinerarium (ApciNPV), Euproctis pseudoconspersa (EupsNPV), and Clanis bilineata (ClbiNPV). Full article
(This article belongs to the Special Issue Insect Viruses)
Figures

Open AccessArticle The Lymantria dispar IPLB-Ld652Y Cell Line Transcriptome Comprises Diverse Virus-Associated Transcripts
Viruses 2011, 3(11), 2339-2350; doi:10.3390/v3112339
Received: 30 September 2011 / Revised: 12 November 2011 / Accepted: 14 November 2011 / Published: 21 November 2011
Cited by 9 | PDF Full-text (1097 KB)
Abstract
The enhanced viral susceptibility of the gypsy moth (Lymantria dispar)-derived IPLB-Ld652Y cell line has made it a popular in vitro system for studying virus-related phenomena in the Lepidoptera. Using both single-pass EST sequencing and 454-based pyrosequencing, a transcriptomic library of [...] Read more.
The enhanced viral susceptibility of the gypsy moth (Lymantria dispar)-derived IPLB-Ld652Y cell line has made it a popular in vitro system for studying virus-related phenomena in the Lepidoptera. Using both single-pass EST sequencing and 454-based pyrosequencing, a transcriptomic library of 14,368 putatively unique transcripts (PUTs) was produced comprising 8,476,050 high-quality, informative bases. The gene content of the IPLB-Ld652Y transcriptome was broadly assessed via comparison with the NCBI non‑redundant protein database, and more detailed functional annotation was inferred by comparison to the Swiss-Prot subset of UniProtKB. In addition to L. dispar cellular transcripts, a diverse array of both RNA and DNA virus-associated transcripts was identified within the dataset, suggestive of a high level of viral expression and activity in IPLB-Ld652Y cells. These sequence resources will provide a sound basis for developing testable experimental hypotheses by insect virologists, and suggest a number of avenues for potential research. Full article
(This article belongs to the Special Issue Insect Viruses)

Review

Jump to: Research

Open AccessReview Viruses of Fish: An Overview of Significant Pathogens
Viruses 2011, 3(11), 2025-2046; doi:10.3390/v3112025
Received: 2 September 2011 / Revised: 26 September 2011 / Accepted: 28 September 2011 / Published: 25 October 2011
Cited by 34 | PDF Full-text (6095 KB)
Abstract
The growing global demand for seafood together with the limited capacity of the wild-capture sector to meet this demand has seen the aquaculture industry continue to grow around the world. A vast array of aquatic animal species is farmed in high density [...] Read more.
The growing global demand for seafood together with the limited capacity of the wild-capture sector to meet this demand has seen the aquaculture industry continue to grow around the world. A vast array of aquatic animal species is farmed in high density in freshwater, brackish and marine systems where they are exposed to new environments and potentially new diseases. On-farm stresses may compromise their ability to combat infection, and farming practices facilitate rapid transmission of disease. Viral pathogens, whether they have been established for decades or whether they are newly emerging as disease threats, are particularly challenging since there are few, if any, efficacious treatments, and the development of effective viral vaccines for delivery in aquatic systems remains elusive. Here, we review a few of the more significant viral pathogens of finfish, including aquabirnaviruses and infectious hematopoietic necrosis virus which have been known since the first half of the 20th century, and more recent viral pathogens, for example betanodaviruses, that have emerged as aquaculture has undergone a dramatic expansion in the past few decades. Full article
(This article belongs to the Special Issue Viruses Infecting Fish, Amphibians, and Reptiles)
Open AccessReview Antiviral Immunity in Amphibians
Viruses 2011, 3(11), 2065-2086; doi:10.3390/v3112065
Received: 5 September 2011 / Revised: 20 October 2011 / Accepted: 22 October 2011 / Published: 31 October 2011
Cited by 18 | PDF Full-text (1072 KB)
Abstract
Although a variety of virus species can infect amphibians, diseases caused by ranaviruses ([RVs]; Iridoviridae) have become prominent, and are a major concern for biodiversity, agriculture and international trade. The relatively recent and rapid increase in prevalence of RV infections, the [...] Read more.
Although a variety of virus species can infect amphibians, diseases caused by ranaviruses ([RVs]; Iridoviridae) have become prominent, and are a major concern for biodiversity, agriculture and international trade. The relatively recent and rapid increase in prevalence of RV infections, the wide range of host species infected by RVs, the variability in host resistance among population of the same species and among different developmental stages, all suggest an important involvement of the amphibian immune system. Nevertheless, the roles of the immune system in the etiology of viral diseases in amphibians are still poorly investigated. We review here the current knowledge of antiviral immunity in amphibians, focusing on model species such as the frog Xenopus and the salamander (Ambystoma tigrinum), and on recent progress in generating tools to better understand how host immune defenses control RV infections, pathogenicity, and transmission. Full article
(This article belongs to the Special Issue Viruses Infecting Fish, Amphibians, and Reptiles)
Open AccessReview Viruses Infecting Reptiles
Viruses 2011, 3(11), 2087-2126; doi:10.3390/v3112087
Received: 2 September 2011 / Revised: 19 October 2011 / Accepted: 21 October 2011 / Published: 1 November 2011
Cited by 45 | PDF Full-text (314 KB)
Abstract
A large number of viruses have been described in many different reptiles. These viruses include arboviruses that primarily infect mammals or birds as well as viruses that are specific for reptiles. Interest in arboviruses infecting reptiles has mainly focused on the role [...] Read more.
A large number of viruses have been described in many different reptiles. These viruses include arboviruses that primarily infect mammals or birds as well as viruses that are specific for reptiles. Interest in arboviruses infecting reptiles has mainly focused on the role reptiles may play in the epidemiology of these viruses, especially over winter. Interest in reptile specific viruses has concentrated on both their importance for reptile medicine as well as virus taxonomy and evolution. The impact of many viral infections on reptile health is not known. Koch’s postulates have only been fulfilled for a limited number of reptilian viruses. As diagnostic testing becomes more sensitive, multiple infections with various viruses and other infectious agents are also being detected. In most cases the interactions between these different agents are not known. This review provides an update on viruses described in reptiles, the animal species in which they have been detected, and what is known about their taxonomic positions. Full article
(This article belongs to the Special Issue Viruses Infecting Fish, Amphibians, and Reptiles)
Open AccessReview Neutralizing Antibody Response to Hepatitis C Virus
Viruses 2011, 3(11), 2127-2145; doi:10.3390/v3112127
Received: 14 September 2011 / Revised: 18 October 2011 / Accepted: 22 October 2011 / Published: 2 November 2011
Cited by 32 | PDF Full-text (1823 KB)
Abstract
A critical first step in a “rational vaccine design” approach for hepatitis C virus (HCV) is to identify the most relevant mechanisms of immune protection. Emerging evidence provides support for a protective role of virus neutralizing antibodies, and the ability of the [...] Read more.
A critical first step in a “rational vaccine design” approach for hepatitis C virus (HCV) is to identify the most relevant mechanisms of immune protection. Emerging evidence provides support for a protective role of virus neutralizing antibodies, and the ability of the B cell response to modify the course of acute HCV infection. This has been made possible by the development of in vitro cell culture models, based on HCV retroviral pseudotype particles expressing E1E2 and infectious cell culture-derived HCV virions, and small animal models that are robust tools in studies of antibody-mediated virus neutralization. This review is focused on the immunogenic determinants on the E2 glycoprotein mediating virus neutralization and the pathways in which the virus is able to escape from immune containment. Encouraging findings from recent studies provide support for the existence of broadly neutralization antibodies that are not associated with virus escape. The identification of conserved epitopes mediating virus neutralization that are not associated with virus escape will facilitate the design of a vaccine immunogen capable of eliciting broadly neutralizing antibodies against this highly diverse virus. Full article
(This article belongs to the Special Issue Humoral Responses Against HCV)
Open AccessReview Herpesviruses that Infect Fish
Viruses 2011, 3(11), 2160-2191; doi:10.3390/v3112160
Received: 15 September 2011 / Revised: 15 October 2011 / Accepted: 22 October 2011 / Published: 8 November 2011
Cited by 26 | PDF Full-text (1246 KB)
Abstract
Herpesviruses are host specific pathogens that are widespread among vertebrates. Genome sequence data demonstrate that most herpesviruses of fish and amphibians are grouped together (family Alloherpesviridae) and are distantly related to herpesviruses of reptiles, birds and mammals (family Herpesviridae). Yet, [...] Read more.
Herpesviruses are host specific pathogens that are widespread among vertebrates. Genome sequence data demonstrate that most herpesviruses of fish and amphibians are grouped together (family Alloherpesviridae) and are distantly related to herpesviruses of reptiles, birds and mammals (family Herpesviridae). Yet, many of the biological processes of members of the order Herpesvirales are similar. Among the conserved characteristics are the virion structure, replication process, the ability to establish long term latency and the manipulation of the host immune response. Many of the similar processes may be due to convergent evolution. This overview of identified herpesviruses of fish discusses the diseases that alloherpesviruses cause, the biology of these viruses and the host-pathogen interactions. Much of our knowledge on the biology of Alloherpesvirdae is derived from research with two species: Ictalurid herpesvirus 1 (channel catfish virus) and Cyprinid herpesvirus 3 (koi herpesvirus). Full article
(This article belongs to the Special Issue Viruses Infecting Fish, Amphibians, and Reptiles)
Open AccessReview The Molecular Biology of Feline Immunodeficiency Virus (FIV)
Viruses 2011, 3(11), 2192-2213; doi:10.3390/v3112192
Received: 1 October 2011 / Revised: 31 October 2011 / Accepted: 31 October 2011 / Published: 9 November 2011
Cited by 8 | PDF Full-text (918 KB)
Abstract
Feline immunodeficiency virus (FIV) is widespread in feline populations and causes an AIDS-like illness in domestic cats. It is highly prevalent in several endangered feline species. In domestic cats FIV infection is a valuable small animal model for HIV infection. In recent [...] Read more.
Feline immunodeficiency virus (FIV) is widespread in feline populations and causes an AIDS-like illness in domestic cats. It is highly prevalent in several endangered feline species. In domestic cats FIV infection is a valuable small animal model for HIV infection. In recent years there has been a significant increase in interest in FIV, in part to exploit this, but also because of the potential it has as a human gene therapy vector. Though much less studied than HIV there are many parallels in the replication of the two viruses, but also important differences and, despite their likely common origin, the viruses have in some cases used alternative strategies to overcome similar problems. Recent advances in understanding the structure and function of FIV RNA and proteins and their interactions has enhanced our knowledge of FIV replication significantly, however, there are still many gaps. This review summarizes our current knowledge of FIV molecular biology and its similarities with, and differences from, other lentiviruses. Full article
(This article belongs to the Special Issue Feline Retroviruses)
Open AccessReview Biology and Genomics of Viruses Within the Genus Gammabaculovirus
Viruses 2011, 3(11), 2214-2222; doi:10.3390/v3112214
Received: 1 October 2011 / Revised: 26 October 2011 / Accepted: 3 November 2011 / Published: 10 November 2011
Cited by 3 | PDF Full-text (753 KB)
Abstract
Hymenoptera is a very large and ancient insect order encompassing bees, wasps, ants and sawflies. Fossil records indicate that they existed over 200 million years ago and about 100 million years before the appearance of Lepidoptera. Sawflies have been major pests [...] Read more.
Hymenoptera is a very large and ancient insect order encompassing bees, wasps, ants and sawflies. Fossil records indicate that they existed over 200 million years ago and about 100 million years before the appearance of Lepidoptera. Sawflies have been major pests in many parts of the world and some have caused serious forest defoliation in North America. All baculoviruses isolated from sawflies are of the single nucleocapsids phenotype and appear to replicate in midgut cells only. This group of viruses has been shown to be excellent pest control agents and three have been registered in Canada and Britain for this purpose. Sawfly baculoviruses contain the smallest genome of all baculoviruses sequenced so far. Gene orders among sequenced sawfly baculoviruses are co-linear but this is not shared with the genomes of lepidopteran baculoviruses. One distinguishing feature among all sequenced sawfly viruses is the lack of a gene encoding a membrane fusion protein, which brought into question the role of the budded virus phenotype in Gammabaculovirus biology. Full article
(This article belongs to the Special Issue Insect Viruses)
Open AccessReview Hepatitis C Virus Assembly Imaging
Viruses 2011, 3(11), 2238-2254; doi:10.3390/v3112238
Received: 21 September 2011 / Revised: 3 November 2011 / Accepted: 4 November 2011 / Published: 15 November 2011
Cited by 8 | PDF Full-text (2030 KB)
Abstract
Hepatitis C Virus (HCV) assembly process is the least understood step in the virus life cycle. The functional data revealed by forward and reverse genetics indicated that both structural and non-structural proteins are involved in the assembly process. Using confocal and electron [...] Read more.
Hepatitis C Virus (HCV) assembly process is the least understood step in the virus life cycle. The functional data revealed by forward and reverse genetics indicated that both structural and non-structural proteins are involved in the assembly process. Using confocal and electron microscopy different groups determined the subcellular localization of different viral proteins and they identified the lipid droplets (LDs) as the potential viral assembly site. Here, we aim to review the mechanisms that govern the viral proteins recruitment to LDs and discuss the current model of HCV assembly process. Based on previous examples, this review will also discuss advanced imaging techniques as potential means to extend our present knowledge of HCV assembly process. Full article
(This article belongs to the Special Issue Frontiers in Imaging)
Open AccessReview Viral Determinants of HIV-1 Macrophage Tropism
Viruses 2011, 3(11), 2255-2279; doi:10.3390/v3112255
Received: 16 September 2011 / Revised: 4 November 2011 / Accepted: 4 November 2011 / Published: 15 November 2011
Cited by 22 | PDF Full-text (290 KB)
Abstract
Macrophages are important target cells for HIV-1 infection that play significant roles in the maintenance of viral reservoirs and other aspects of pathogenesis. Understanding the determinants of HIV-1 tropism for macrophages will inform HIV-1 control and eradication strategies. Tropism for macrophages is [...] Read more.
Macrophages are important target cells for HIV-1 infection that play significant roles in the maintenance of viral reservoirs and other aspects of pathogenesis. Understanding the determinants of HIV-1 tropism for macrophages will inform HIV-1 control and eradication strategies. Tropism for macrophages is both qualitative (infection or not) and quantitative (replication capacity). For example many R5 HIV-1 isolates cannot infect macrophages, but for those that can the macrophage replication capacity can vary by up to 1000-fold. Some X4 viruses are also capable of replication in macrophages, indicating that cellular tropism is partially independent of co-receptor preference. Preliminary data obtained with a small number of transmitted/founder viruses indicate inefficient macrophage infection, whereas isolates from later in disease are more frequently tropic for macrophages. Thus tropism may evolve over time, and more macrophage tropic viruses may be implicated in the pathogenesis of advanced HIV-1 infection. Compartmentalization of macrophage-tropic brain-derived envelope glycoproteins (Envs), and non-macrophage tropic non-neural tissue-derived Envs points to adaptation of HIV-1 quasi-species in distinct tissue microenvironments. Mutations within and adjacent to the Env-CD4 binding site have been identified that determine macrophage tropism at the entry level, but post-entry molecular determinants of macrophage replication capacity involving HIV-1 accessory proteins need further definition. Full article
Open AccessReview Hepatitis C Virus Evasion Mechanisms from Neutralizing Antibodies
Viruses 2011, 3(11), 2280-2300; doi:10.3390/v3112280
Received: 8 September 2011 / Revised: 28 October 2011 / Accepted: 7 November 2011 / Published: 15 November 2011
Cited by 34 | PDF Full-text (274 KB)
Abstract
Hepatitis C virus (HCV) represents a major public health problem, affecting 3% of the world’s population. The majority of infected individuals develop chronic hepatitis, which can progress to cirrhosis and hepatocellular carcinoma. To date, a vaccine is not available and current therapy [...] Read more.
Hepatitis C virus (HCV) represents a major public health problem, affecting 3% of the world’s population. The majority of infected individuals develop chronic hepatitis, which can progress to cirrhosis and hepatocellular carcinoma. To date, a vaccine is not available and current therapy is limited by resistance, adverse effects and high costs. Although it is very well established that cell-mediated immunity is necessary for viral clearance, the importance of host antibodies in clearing HCV infection is being increasingly recognized. Indeed, recent studies indicate that neutralizing antibodies are induced in the early phase of infection by patients who subsequently clear viral infection. Conversely, patients who do not clear the virus develop high titers of neutralizing antibodies during the chronic stage. Surprisingly, these antibodies are not able to control HCV infection. HCV has therefore developed mechanisms to evade immune elimination, allowing it to persist in the majority of infected individuals. A detailed understanding of the mechanisms by which the virus escapes immune surveillance is therefore necessary if novel preventive and therapeutic treatments have to be designed. This review summarizes the current knowledge of the mechanisms used by HCV to evade host neutralizing antibodies. Full article
(This article belongs to the Special Issue Humoral Responses Against HCV)
Open AccessReview Stress Granules in the Viral Replication Cycle
Viruses 2011, 3(11), 2328-2338; doi:10.3390/v3112328
Received: 13 September 2011 / Revised: 13 November 2011 / Accepted: 14 November 2011 / Published: 18 November 2011
Cited by 16 | PDF Full-text (1189 KB)
Abstract
As intracellular parasites, viruses require a host cell in order to replicate. However, they face a series of cellular responses against infection. One of these responses is the activation of the double-stranded RNA (dsRNA)-activated protein kinase R (PKR). PKR phosphorylates the α [...] Read more.
As intracellular parasites, viruses require a host cell in order to replicate. However, they face a series of cellular responses against infection. One of these responses is the activation of the double-stranded RNA (dsRNA)-activated protein kinase R (PKR). PKR phosphorylates the α subunit of eukaryotic translation initiation factor 2 (eIF2α), which in turn results in global protein synthesis inhibition and formation of stress granules (SGs). Recent studies have shown that SGs can interfere with the replicative cycle of certain viruses. This review addresses how viruses have evolved different control strategies at the SG level to ensure an efficient replication cycle during the cellular stress response triggered by the viral infection. Full article
Open AccessReview Ecopathology of Ranaviruses Infecting Amphibians
Viruses 2011, 3(11), 2351-2373; doi:10.3390/v3112351
Received: 16 September 2011 / Revised: 3 November 2011 / Accepted: 10 November 2011 / Published: 22 November 2011
Cited by 54 | PDF Full-text (877 KB)
Abstract
Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in organ necrosis and massive hemorrhaging. Subclinical infections have been documented, although their role in ranavirus persistence and emergence [...] Read more.
Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in organ necrosis and massive hemorrhaging. Subclinical infections have been documented, although their role in ranavirus persistence and emergence remains unclear. Water is an effective transmission medium for ranaviruses, and survival outside the host may be for significant duration. In aquatic communities, amphibians, reptiles and fish may serve as reservoirs. Controlled studies have shown that susceptibility to ranavirus infection and disease varies among amphibian species and developmental stages, and likely is impacted by host-pathogen coevolution, as well as, exogenous environmental factors. Field studies have demonstrated that the likelihood of epizootics is increased in areas of cattle grazing, where aquatic vegetation is sparse and water quality is poor. Translocation of infected amphibians through commercial trade (e.g., food, fish bait, pet industry) contributes to the spread of ranaviruses. Such introductions may be of particular concern, as several studies report that ranaviruses isolated from ranaculture, aquaculture, and bait facilities have greater virulence (i.e., ability to cause disease) than wild-type isolates. Future investigations should focus on the genetic basis for pathogen virulence and host susceptibility, ecological and anthropogenic mechanisms contributing to emergence, and vaccine development for use in captive populations and species reintroduction programs. Full article
(This article belongs to the Special Issue Viruses Infecting Fish, Amphibians, and Reptiles)

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