An optimised protocol for the expression and purification of adenovirus core protein VII

Adenovirus protein VII (pVII) is a highly basic core protein, bearing resemblance to mammalian histones. Despite its diverse functions, a comprehensive understanding of its structural intricacies and the mechanisms underlying its functions remain elusive, primarily due to the complexity of producing a good amount of soluble pVII. This study aimed to optimise the expression and purification of recombinant pVII from four different adenoviruses with a simple vector construct. This study successfully determined the optimal conditions for efficiently purifying pVII across four adenovirus species, revealing the differential preference for bacterial expression systems. The One Shot BL21 Star (DE3) proved favourable over Rosetta 2 (DE3) pLysS with consistent levels of expression between IPTG-induced and auto-induction. We demonstrated that combining chemical and mechanical cell lysis is possible and highly effective. Other noteworthy benefits were observed in using RNase during sample processing. The addition of RNase has significantly improved the quality and quantity of the purified protein as confirmed by chromatographic and western blot analyses. These findings established a solid groundwork for pVII purification methodologies and carry the significant potential to assist in unveiling the core structure of pVII, its arrangement within the core, DNA condensation intricacies, and potential pathways for nuclear transport.

Antiviral Wolbachia strains associate with Aedes aegypti endoplasmic reticulum membranes and induce lipid droplet formation to restrict dengue virus replication

Wolbachia are a genus of insect endosymbiotic bacteria which includes strains wMel and wAlbB that are being utilized as a biocontrol tool to reduce the incidence of Aedes aegypti-transmitted viral diseases like dengue. However, the precise mechanisms underpinning the antiviral activity of these Wolbachia strains are not well defined. Here, we generated a panel of Ae. aegypti-derived cell lines infected with antiviral strains wMel and wAlbB or the non-antiviral Wolbachia strain wPip to understand host cell morphological changes specifically induced by antiviral strains. Antiviral strains were frequently found to be entirely wrapped by the host endoplasmic reticulum (ER) membrane, while wPip bacteria clustered separately in the host cell cytoplasm. ER-derived lipid droplets (LDs) increased in volume in wMel- and wAlbB-infected cell lines and mosquito tissues compared to cells infected with wPip or Wolbachia-free controls. Inhibition of fatty acid synthase (required for triacylglycerol biosynthesis) reduced LD formation and significantly restored ER-associated dengue virus replication in cells occupied by wMel. Together, this suggests that antiviral Wolbachia strains may specifically alter the lipid composition of the ER to preclude the establishment of dengue virus (DENV) replication complexes. Defining Wolbachia's antiviral mechanisms will support the application and longevity of this effective biocontrol tool that is already being used at scale.IMPORTANCEAedes aegypti transmits a range of important human pathogenic viruses like dengue. However, infection of Ae. aegypti with the insect endosymbiotic bacterium, Wolbachia, reduces the risk of mosquito to human viral transmission. Wolbachia is being utilized at field sites across more than 13 countries to reduce the incidence of viruses like dengue, but it is not well understood how Wolbachia induces its antiviral effects. To examine this at the subcellular level, we compared how different strains of Wolbachia with varying antiviral strengths associate with and modify host cell structures. Strongly antiviral strains were found to specifically associate with the host endoplasmic reticulum and induce striking impacts on host cell lipid droplets. Inhibiting Wolbachia-induced lipid redistribution partially restored dengue virus replication demonstrating this is a contributing role for Wolbachia's antiviral activity. These findings provide new insights into how antiviral Wolbachia strains associate with and modify Ae. aegypti host cells.

Structural and functional characterization of siadenovirus core protein VII nuclear localization demonstrates the existence of multiple nuclear transport pathways

Adenovirus protein VII (pVII) plays a crucial role in the nuclear localization of genomic DNA following viral infection and contains nuclear localization signal (NLS) sequences for the importin (IMP)-mediated nuclear import pathway. However, functional analysis of pVII in adenoviruses to date has failed to fully determine the underlying mechanisms responsible for nuclear import of pVII. Therefore, in the present study, we extended our analysis by examining the nuclear trafficking of adenovirus pVII from a non-human species, psittacine siadenovirus F (PsSiAdV). We identified a putative classical (c)NLS at pVII residues 120-128 (120PGGFKRRRL128). Fluorescence polarization and electrophoretic mobility shift assays demonstrated direct, high-affinity interaction with both IMPα2 and IMPα3 but not IMPβ. Structural analysis of the pVII-NLS/IMPα2 complex confirmed a classical interaction, with the major binding site of IMPα occupied by K124 of pVII-NLS. Quantitative confocal laser scanning microscopy showed that PsSiAdV pVII-NLS can confer IMPα/β-dependent nuclear localization to GFP. PsSiAdV pVII also localized in the nucleus when expressed in the absence of other viral proteins. Importantly, in contrast to what has been reported for HAdV pVII, PsSiAdV pVII does not localize to the nucleolus. In addition, our study demonstrated that inhibition of the IMPα/β nuclear import pathway did not prevent PsSiAdV pVII nuclear targeting, indicating the existence of alternative pathways for nuclear localization, similar to what has been previously shown for human adenovirus pVII. Further examination of other potential NLS signals, characterization of alternative nuclear import pathways, and investigation of pVII nuclear targeting across different adenovirus species is recommended to fully elucidate the role of varying nuclear import pathways in the nuclear localization of pVII.

Evidence of Australian wild deer exposure to N. caninum infection and potential implications for the maintenance of N. caninum sylvatic cycle

Infections with the coccidian parasite Neospora caninum affect domestic and wild animals worldwide. In Australia, N. caninum infections cause considerable losses to the cattle industry with seroprevalence of 8.7% in beef and 10.9% in dairy cattle. Conversely, the role of wild animals, in maintaining the parasite cycle is also unclear. It is possible that native or introduced herbivorous species could be reservoir hosts of N. caninum in Australia, but to date, this has not been investigated. We report here the first large-scale screening of N. caninum antibodies in Australian wild deer, spanning three species (fallow, red and sambar deer). Consequently, we also assessed two commercial cELISA tests validated for detecting N. caninum in cattle for their ability to detect N. caninum antibodies in serum samples of wild deer. N. caninum antibodies were detected in 3.7% (7/189, 95% CI 1.8 - 7.45) of the wild deer serum samples collected in south-eastern Australia (n = 189), including 97 fallow deer (Dama dama), 14 red deer (Cervus elaphus), and 78 sambar deer (Rusa unicolor). Overall, our study provides the first detection of N. caninum antibodies in wild deer and quantifies deer's potential role in the sylvatic cycle of N. caninum.

Antiviral response within different cell types of the CNS

The central nervous system (CNS) is a constitutive structure of various cell types conserved by anatomical barriers. Many of the major CNS cell-type populations distributed across the different brain regions are targets for several neurotropic viruses. Numerous studies have demonstrated that viral susceptibility within the CNS is not absolute and initiates a cell-type specific antiviral defence response. Neurons, astrocytes, and microglial cells are among the major resident cell populations within the CNS and are all equipped to sense viral infection and induce a relative antiviral response mostly through type I IFN production, however, not all these cell types adopt a similar antiviral strategy. Rising evidence has suggested a diversity regarding IFN production and responsiveness based on the cell type/sub type, regional distinction and cell`s developmental state which could shape distinct antiviral signatures. Among CNS resident cell types, neurons are of the highest priority to defend against the invading virus due to their poor renewable nature. Therefore, infected and uninfected glial cells tend to play more dominant antiviral roles during a viral infection and have been found to be the major CNS IFN producers. Alternatively, neuronal cells do play an active part during antiviral responses but may adopt differential strategies in addition to induction of a typical type I IFN response, to minimize the chance of cellular damage. Heterogeneity observed in neuronal IFN responsiveness may be partially explained by their altered ISGs and/or lower STATS expression levels, however, further in vivo studies are required to fully elucidate the specificity of the acquired antiviral responses by distinct CNS cell types.

First Evidence of Entamoeba Parasites in Australian Wild Deer and Assessment of Transmission to Cattle

Australian wild deer populations have significantly expanded in size and distribution in recent decades. Due to their role in pathogen transmission, these deer populations pose a biosecurity risk to the livestock industry. However, little is known about the infection status of wild deer in Australia. The intestinal parasite Entamoeba bovis has been previously detected in farm and wild ruminants worldwide, but its epidemiology and distribution in wild ruminants remain largely unexplored. To investigate this knowledge gap, faecal samples of wild deer and domestic cattle from south-eastern Australia were collected and analysed for the presence of Entamoeba spp. using PCR and phylogenetic analysis of the conserved 18S rRNA gene. E. bovis parasites were detected at high prevalence in cattle and wild deer hosts, and two distinct Entamoeba ribosomal lineages (RLs), RL1 and RL8, were identified in wild deer. Phylogenetic analysis further revealed the existance of a novel Entamoeba species in sambar deer and a novel Entamoeba RL in fallow deer. While we anticipated cross-species transmission of E. bovis between wild deer and cattle, the data generated in this study demonstrated transmission is yet to occur in Australia. Overall, this study has identified novel variants of Entamoeba and constitutes the first report of Entamoeba in fallow deer and sambar deer, expanding the host range of this parasite. Epidemiological investigations and continued surveillance of Entamoeba parasites in farm ruminants and wild animals will be required to evaluate pathogen emergence and transmission to livestock.

Novel Picornavirus Detected in Wild Deer: Identification, Genomic Characterisation, and Prevalence in Australia

The use of high-throughput sequencing has facilitated virus discovery in wild animals and helped determine their potential threat to humans and other animals. We report the complete genome sequence of a novel picornavirus identified by next-generation sequencing in faeces from Australian fallow deer. Genomic analysis revealed that this virus possesses a typical picornavirus-like genomic organisation of 7554 nt with a single open reading frame (ORF) encoding a polyprotein of 2225 amino acids. Based on the amino acid identity comparison and phylogenetic analysis of the P1, 2C, 3CD, and VP1 regions, this novel picornavirus was closely related to but distinct from known bopiviruses detected to date. This finding suggests that deer/bopivirus could belong to a novel species within the genus Bopivirus, tentatively designated as "Bopivirus C". Epidemiological investigation of 91 deer (71 fallow, 14 sambar and 6 red deer) and 23 cattle faecal samples showed that six fallow deer and one red deer (overall prevalence 7.7%, 95% confidence interval [CI] 3.8-15.0%) tested positive, but deer/bopivirus was undetectable in sambar deer and cattle. In addition, phylogenetic and sequence analyses indicate that the same genotype is circulating in south-eastern Australia. To our knowledge, this study reports for the first time a deer-origin bopivirus and the presence of a member of genus Bopivirus in Australia. Further epidemiological and molecular studies are needed to investigate the geographic distribution and pathogenic potential of this novel Bopivirus species in other domestic and wild animal species.

Host upregulation of lipid droplets drives antiviral responses

When a host cell is infected by a virus, it activates the innate immune response, setting off a cascade of signalling events leading to the production of an antiviral response. This immune response is typically robust and in general works well to clear viral infections, however, viruses have evolved evasion strategies to combat this, and therefore, a better understanding of how this response works in more detail is needed for the development of novel and effective therapeutics. Lipid droplets (LDs) are intracellular organelles and have historically been thought of simply as cellular energy sources, however, have more recently been recognised as critical organelles in signalling events. Importantly, many viruses are known to take over host cellular production of LDs, and it has traditionally been assumed the sole purpose of this is to supply energy for viral life cycle events. However, our recent work positions LDs as important organelles during the first few hours of an antiviral response, showing that they underpin the production of important antiviral cytokines following viral infection. Following infection of cells with either RNA viruses (Zika, Dengue, Influenza A) or a DNA (Herpes Simplex Virus-1) virus, LDs were rapidly upregulated, and this response was also replicated following stimulation with viral mimic agonists. This upregulation of LDs following infection was transient, and interestingly, did not follow the well described homeostatic mechanism of LD upregulation, instead being controlled by EGFR. The cell's ability to mount an effective immune response was greatly diminished when inhibiting EGFR, thus inhibiting LD upregulation during infection, also leading to an increase in viral replication. In this microreview, we extrapolate our recent findings and discuss LDs as an important organelle in the innate immune response.

Viperin has species-specific roles in response to herpes simplex virus infection

Viperin is a gene with a broad spectrum of antiviral functions and various mechanisms of action. The role of viperin in herpes simplex virus type 1 (HSV-1) infection is unclear, with conflicting data in the literature that is derived from a single human cell type. We have addressed this gap by investigating viperin during HSV-1 infection in several cell types, spanning species and including immortalized, non-immortalized and primary cells. We demonstrate that viperin upregulation by HSV-1 infection is cell-type-specific, with mouse cells typically showing greater increases compared with those of human origin. Further, overexpression and knockout of mouse, but not human viperin significantly impedes and increases HSV-1 replication, respectively. In primary mouse fibroblasts, viperin upregulation by infection requires viral gene transcription and occurs in a predominantly IFN-independent manner. Further we identify the N-terminal domain of viperin as being required for the anti-HSV-1 activity. Interestingly, this is the region of viperin that differs most between mouse and human, which may explain the apparent species-specific activity against HSV-1. Finally, we show that HSV-1 virion host shutoff (vhs) protein is a key viral factor that antagonises viperin in mouse cells. We conclude that viperin can be upregulated by HSV-1 in mouse and human cells, and that mouse viperin has anti-HSV-1 activity.

Lipid droplets and lipid mediators in viral infection and immunity

Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.

Evaluation of haemoparasite and Sarcocystis infections in Australian wild deer

Wild animals are natural reservoir hosts for a variety of pathogens that can be transmitted to other wildlife, livestock, other domestic animals, and humans. Wild deer (family Cervidae) in Europe, Asia, and North and South America have been reported to be infected with gastrointestinal and vector-borne parasites. In Australia, wild deer populations have expanded considerably in recent years, yet there is little information regarding which pathogens are present and whether these pathogens pose biosecurity threats to humans, wildlife, livestock, or other domestic animals. To address this knowledge gap, PCR-based screening for five parasitic genera was conducted in blood samples (n = 243) sourced from chital deer (Axis axis), fallow deer (Dama dama), rusa deer (Rusa timorensis) and sambar deer (Rusa unicolor) sampled in eastern Australia. These blood samples were tested for the presence of DNA from Plasmodium spp., Trypanosoma spp., Babesia spp., Theileria spp. and Sarcocystis spp. Further, the presence of antibodies against Babesia bovis was investigated in serum samples (n = 105) by immunofluorescence. In this study, neither parasite DNA nor antibodies were detected for any of the five genera investigated. These results indicate that wild deer are not currently host reservoirs for Plasmodium, Trypanosoma, Babesia, Theileria or Sarcocystis parasites in eastern Australia. We conclude that in eastern Australia, wild deer do not currently play a significant role in the transmission of these parasites. This survey represents the first large-scale molecular study of its type in Australian wild deer and provides important baseline information about the parasitic infection status of these animals. The expanding populations of wild deer throughout Australia warrant similar surveys in other parts of the country and surveillance efforts to continually assess the level of threat wild deer could pose to humans, wildlife, livestock and other domestic animals.

Viperin interacts with PEX19 to mediate peroxisomal augmentation of the innate antiviral response

Peroxisomes are recognized as significant platforms for the activation of antiviral innate immunity where stimulation of the key adapter molecule mitochondrial antiviral signaling protein (MAVS) within the RIG-I like receptor (RLR) pathway culminates in the up-regulation of hundreds of ISGs, some of which drive augmentation of multiple innate sensing pathways. However, whether ISGs can augment peroxisome-driven RLR signaling is currently unknown. Using a proteomics-based screening approach, we identified Pex19 as a binding partner of the ISG viperin. Viperin colocalized with numerous peroxisomal proteins and its interaction with Pex19 was in close association with lipid droplets, another emerging innate signaling platform. Augmentation of the RLR pathway by viperin was lost when Pex19 expression was reduced. Expression of organelle-specific MAVS demonstrated that viperin requires both mitochondria and peroxisome MAVS for optimal induction of IFN-β. These results suggest that viperin is required to enhance the antiviral cellular response with a possible role to position the peroxisome at the mitochondrial/MAM MAVS signaling synapse, furthering our understanding of the importance of multiple organelles driving the innate immune response against viral infection.

Lipid Droplet Motility Increases Following Viral Immune Stimulation

Lipid droplets (LDs) have traditionally been thought of as solely lipid storage compartments for cells; however, in the last decade, they have emerged as critical organelles in health and disease. LDs are highly dynamic within cells, and their movement is critical in organelle-organelle interactions. Their dynamics are known to change during cellular stress or nutrient deprivation; however, their movement during pathogen infections, especially at very early timepoints, is under-researched. This study aimed to track LD dynamics in vitro, in an astrocytic model of infection. Cells were either stimulated with a dsRNA viral mimic, poly I:C, or infected with the RNA virus, Zika virus. Individual LDs within infected cells were analysed to determine displacement and speed, and average LD characteristics for multiple individual cells calculated. Both LD displacement and mean speed were significantly enhanced in stimulated cells over a time course of infection with an increase seen as early as 2 h post-infection. With the emerging role for LDs during innate host responses, understanding their dynamics is critical to elucidate how these organelles influence the outcome of viral infection.

The Complex Diseases of Staphylococcus pseudintermedius in Canines: Where to Next?

Staphylococcus pseudintermedius is a pathogenic bacterium of concern within the veterinary sector and is involved in numerous infections in canines, including topical infections such as canine pyoderma and otitis externa, as well as systemic infections within the urinary, respiratory and reproductive tract. The high prevalence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) within such infections is a growing concern. Therefore, it is crucial to understand the involvement of S. pseudintermedius in canine disease pathology to gain better insight into novel treatment avenues. Here, we review the literature focused on S. pseudintermedius infection in multiple anatomic locations in dogs and the role of MRSP in treatment outcomes at these niches. Multiple novel treatment avenues for MRSP have been pioneered in recent years and these are discussed with a specific focus on vaccines and phage therapy as potential therapeutic options. Whilst both undertakings are in their infancy, phage therapy is versatile and has shown high success in both animal and human medical use. It is clear that further research is required to combat the growing problems associated with MRSP in canines.

Viperin binds STING and enhances the type-I interferon response following dsDNA detection

Viperin is an interferon-inducible protein that is pivotal for eliciting an effective immune response against an array of diverse viral pathogens. Here we describe a mechanism of viperin's broad antiviral activity by demonstrating the protein's ability to synergistically enhance the innate immune dsDNA signaling pathway to limit viral infection. Viperin co-localized with the key signaling molecules of the innate immune dsDNA sensing pathway, STING and TBK1; binding directly to STING and inducing enhanced K63-linked polyubiquitination of TBK1. Subsequent analysis identified viperin's necessity to bind the cytosolic iron-sulfur assembly component 2A, to prolong its enhancement of the type-I interferon response to aberrant dsDNA. Here we show that viperin facilitates the formation of a signaling enhanceosome, to coordinate efficient signal transduction following activation of the dsDNA signaling pathway, which results in an enhanced antiviral state. We also provide evidence for viperin's radical SAM enzymatic activity to self-limit its immunomodulatory functions. These data further define viperin's role as a positive regulator of innate immune signaling, offering a mechanism of viperin's broad antiviral capacity.

Serosurveillance and Molecular Investigation of Wild Deer in Australia Reveals Seroprevalence of Pestivirus Infection

Since deer were introduced into Australia in the mid-1800s, their wild populations have increased in size and distribution, posing a potential risk to the livestock industry, through their role in pathogen transmission cycles. In comparison to livestock, there are limited data on viral infections in all wildlife, including deer. The aim of this study was to assess blood samples from wild Australian deer for serological evidence of exposure to relevant viral livestock diseases. Blood samples collected across eastern Australia were tested by ELISA to detect antigens and antibodies against Pestivirus and antibodies against bovine herpesvirus 1. A subset of samples was also assessed by RT-PCR for Pestivirus, Simbu serogroup, epizootic hemorrhagic disease virus and bovine ephemeral fever virus. Our findings demonstrated a very low seroprevalence (3%) for ruminant Pestivirus, and none of the other viruses tested were detected. These results suggest that wild deer may currently be an incidental spill-over host (rather than a reservoir host) for Pestivirus. However, deer could be a future source of viral infections for domestic animals in Australia. Further investigations are needed to monitor pathogen activity and quantify possible future infectious disease impacts of wild deer on the Australian livestock industry.

Molecular characterisation of a novel pathogenic avipoxvirus from the Australian magpie (Gymnorhina tibicen)

Avipoxviruses are significant pathogens infecting a wide range of wild and domestic bird species globally. Here, we describe a novel genome sequence of magpiepox virus (MPPV) isolated from an Australian magpie. In the present study, histopathologically confirmed cutaneous pox lesions were used for transmission electron microscopic analysis, which demonstrated brick-shaped virions with regular spaced thread-like ridges, indicative of likely infectious particles. Subsequent analysis of the recovered MPPV genome positioned phylogenetically to a distinct sub-clade with the recently isolated avipoxvirus genome sequences from shearwater and canary bird species, and demonstrates a high degree of sequence similarity with CNPV (96.14%) and SWPV-2 (95.87%). The novel MPPV complete genome is missing 19 genes with a further 41 genes being truncated/fragmented compared to SWPV-2 and contains nine predicted unique genes. This is the first avipoxvirus complete genome sequence that infects Australian magpie.

The interferon stimulated gene viperin, restricts Shigella. flexneri in vitro

The role of interferon and interferon stimulated genes (ISG) in limiting bacterial infection is controversial, and the role of individual ISGs in the control of the bacterial life-cycle is limited. Viperin, is a broad acting anti-viral ISGs, which restricts multiple viral pathogens with diverse mechanisms. Viperin is upregulated early in some bacterial infections, and using the intracellular bacterial pathogen, S. flexneri, we have shown for the first time that viperin inhibits the intracellular bacterial life cycle. S. flexneri replication in cultured cells induced a predominantly type I interferon response, with an early increase in viperin expression. Ectopic expression of viperin limited S. flexneri cellular numbers by as much as 80% at 5hrs post invasion, with similar results also obtained for the intracellular pathogen, Listeria monocytogenes. Analysis of viperins functional domains required for anti-bacterial activity revealed the importance of both viperin's N-terminal, and its radical SAM enzymatic function. Live imaging of S. flexneri revealed impeded entry into viperin expressing cells, which corresponded to a loss of cellular cholesterol. This data further defines viperin's multi-functional role, to include the ability to limit intracellular bacteria; and highlights the role of ISGs and the type I IFN response in the control of bacterial pathogens.

Molecular characterization of the first saltwater crocodilepox virus genome sequences from the world's largest living member of the Crocodylia

Crocodilepox virus is a large dsDNA virus belonging to the genus Crocodylidpoxvirus, which infects a wide range of host species in the order Crocodylia worldwide. Here, we present genome sequences for a novel saltwater crocodilepox virus, with two subtypes (SwCRV-1 and -2), isolated from the Australian saltwater crocodile. Affected belly skins of juvenile saltwater crocodiles were used to sequence complete viral genomes, and perform electron microscopic analysis that visualized immature and mature virions. Analysis of the SwCRV genomes showed a high degree of sequence similarity to CRV (84.53% and 83.70%, respectively), with the novel SwCRV-1 and -2 complete genome sequences missing 5 and 6 genes respectively when compared to CRV, but containing 45 and 44 predicted unique genes. Similar to CRV, SwCRV also lacks the genes involved in virulence and host range, however, considering the presence of numerous hypothetical and or unique genes in the SwCRV genomes, it is completely reasonable that the genes encoding these functions are present but not recognized. Phylogenetic analysis suggested a monophyletic relationship between SwCRV and CRV, however, SwCRV is quite distinct from other chordopoxvirus genomes. These are the first SwCRV complete genome sequences isolated from saltwater crocodile skin lesions.

Lipid droplet density alters the early innate immune response to viral infection

The cellular localisation of many innate signalling events following viral infection has yet to be elucidated, however there has been a few cases in which membranes of certain cellular organelles have acted as platforms to these events. Of these, lipid droplets (LDs) have recently been identified as signalling platforms for innate TLR7 and 9 signalling. Despite their wide range of similar roles in various metabolic pathways, LDs have been overlooked as potential platforms for antiviral innate signalling events. This study established an in vitro model to evaluate the efficiency of the early innate immune response in cells with reduced LD content to the viral mimics, dsDNA and dsRNA, and Sendai viral infection. Using RT-qPCR, the expression of IFN-β and IFN-λ was quantified following stimulation along with the expression of specific ISGs. Luciferase based assays evaluated the combined expression of ISRE-promoter driven ISGs under IFN-β stimulation. Cellular LD content did not alter the entry of fluorescently labelled viral mimics into cells, but significantly decreased the ability of both Huh-7 and HeLa cells to produce type I and III IFN, as well as downstream ISG expression, indicative of an impeded innate immune response. This observation was also seen during Sendai virus infection of HeLa cells, where both control and LD reduced cells replicated the virus to the same level, but a significantly impaired type I and III IFN response was observed in the LD reduced cells. In addition to altered IFN production, cells with reduced LD content exhibited decreased expression of specific antiviral ISGs: Viperin, IFIT-1 and OAS-1 under IFN-β stimulation; However the overall induction of the ISRE-promoter was not effected. This study implicates a role for LDs in an efficient early innate host response to viral infection and future work will endeavour to determine the precise role these important organelles play in induction of an antiviral response.

Interferon-Stimulated Genes as Enhancers of Antiviral Innate Immune Signaling

The ability of a host to curb a viral infection is heavily reliant on the effectiveness of an initial antiviral innate immune response, resulting in the upregulation of interferon (IFN) and, subsequently, IFN-stimulated genes (ISGs). ISGs serve to mount an antiviral state within a host cell, and although the specific antiviral function of a number of ISGs has been characterized, the function of many of these ISGs remains to be determined. Recent research has uncovered a novel role for a handful of ISGs, some of them directly induced by IFN regulatory factor 3 in the absence of IFN itself. These ISGs, most with potent antiviral activity, are also able to augment varying arms of the innate immune response to viral infection, thereby strengthening this response. This new understanding of the role of ISGs may, in turn, help the recent advancement of novel therapeutics aiming to augment innate signaling pathways in an attempt to control viral infection and pathogenesis.

Dynamic Changes in Host Gene Expression following In Vitro Viral Mimic Stimulation in Crocodile Cells

The initial control of viral infection in a host is dominated by a very well orchestrated early innate immune system; however, very little is known about the ability of a host to control viral infection outside of mammals. The reptiles offer an evolutionary bridge between the fish and mammals, with the crocodile having evolved from the archosauria clade that included the dinosaurs, and being the largest living reptile species. Using an RNA-seq approach, we have defined the dynamic changes of a passaged primary crocodile cell line to stimulation with both RNA and DNA viral mimics. Cells displayed a marked upregulation of many genes known to be involved in the mammalian response to viral infection, including viperin, Mx1, IRF7, IRF1, and RIG-I with approximately 10% of the genes being uncharacterized transcripts. Both pathway and genome analysis suggested that the crocodile may utilize the main known mammalian TLR and cytosolic antiviral RNA signaling pathways, with the pathways being responsible for sensing DNA viruses less clear. Viral mimic stimulation upregulated the type I interferon, IFN-Omega, with many known antiviral interferon-stimulated genes also being upregulated. This work demonstrates for the first time that reptiles show functional regulation of many known and unknown antiviral pathways and effector genes. An enhanced knowledge of these ancient antiviral pathways will not only add to our understanding of the host antiviral innate response in non-mammalian species, but is critical to fully comprehend the complexity of the mammalian innate immune response to viral infection.

Investigation of sphingosine kinase 1 in interferon responses during dengue virus infection

Dengue virus (DENV) regulates sphingosine kinase (SK)-1 activity and chemical inhibition of SK1 reduces DENV infection. In primary murine embryonic fibroblasts (pMEFs) lacking SK1 however, DENV infection is enhanced and this is associated with induction of normal levels of interferon beta (IFN-β) but reduced levels of IFN-stimulated genes (ISGs). We have further investigated this link between SK1 and type I IFN responses. DENV infection downregulates cell-surface IFN-alpha receptor (IFNAR)1 in both wild-type (WT) and SK1^-/- pMEF, but, consistent with poor ISG responses, shows reduced induction of phosphorylated (p)-STAT1 and key IFN regulatory factors (IRF)1 and -7 in SK1^-/- pMEF. Direct IFN stimulation induced ISGs (viperin, IFIT1), CXCL10, IRF1 and -7 and p-STAT1. Responses, however, were significantly reduced in SK1^-/- pMEF, except for IFN-stimulated CXCL10 and IRF7. Poor IFN responses in SK1^-/- pMEF were associated with a small reduction in basal cell-surface IFNAR1 and IRF1 mRNA in uninfected SK1^-/- compared with WT pMEF. In contrast, treatment of cells with the SK1 inhibitor, SK1-I or expression of an inhibitory SK1 short hairpin RNA (shRNA), both of which reduce DENV infection, does not alter basal IRF1 mRNA or affect type I IFN stimulation of p-STAT1. Thus, cells genetically lacking SK1 can induce many responses normally following DENV infection, but have adaptive changes in IFNAR1 and IRF1 that compromise DENV-induced type I IFN responses. This suggests a biological link between SK1 and IFN-stimulated pathways. Other approaches to reduce SK1 activity, however, do not influence these important antiviral pathways but reduce infection and may be useful antiviral strategies.

Oyster viperin retains direct antiviral activity and its transcription occurs via a signalling pathway involving a heat-stable haemolymph protein

Little is known about the response of non-model invertebrates, such as oysters, to virus infection. The vertebrate innate immune system detects virus-derived nucleic acids to trigger the type I IFN pathway, leading to the transcription of hundreds of IFN-stimulated genes (ISGs) that exert antiviral functions. Invertebrates were thought to lack the IFN pathway based on the absence of IFN or ISGs encoded in model invertebrate genomes. However, the oyster genome encodes many ISGs, including the well-described antiviral protein viperin. In this study, we characterized oyster viperin and showed that it localizes to caveolin-1 and inhibits dengue virus replication in a heterologous model. In a second set of experiments, we have provided evidence that the haemolymph from poly(I : C)-injected oysters contains a heat-stable, protease-susceptible factor that induces haemocyte transcription of viperin mRNA in conjunction with upregulation of IFN regulatory factor. Collectively, these results support the concept that oysters have antiviral systems that are homologous to the vertebrate IFN pathway.

Reduction in sphingosine kinase 1 influences the susceptibility to dengue virus infection by altering antiviral responses

Sphingosine kinase (SK) 1 is a host kinase that enhances some viral infections. Here we investigated the ability of SK1 to modulate dengue virus (DENV) infection in vitro. Overexpression of SK1 did not alter DENV infection; however, targeting SK1 through chemical inhibition resulted in reduced DENV RNA and infectious virus release. DENV infection of SK1⁻/ ⁻ murine embryonic fibroblasts (MEFs) resulted in inhibition of infection in an immortalized line (iMEF) but enhanced infection in primary MEFs (1°MEFs). Global cellular gene expression profiles showed expected innate immune mRNA changes in DENV-infected WT but no induction of these responses in SK1⁻/⁻  iMEFs. Reverse transciption PCR demonstrated a low-level induction of IFN-β and poor induction of mRNA for the interferon-stimulated genes (ISGs) viperin, IFIT1 and CXCL10 in DENV-infected SK1⁻/⁻  compared with WT iMEFs. Similarly, reduced induction of ISGs was observed in SK1⁻/⁻  1°MEFs, even in the face of high-level DENV replication. In both iMEFs and 1°MEFs, DENV infection induced production of IFN-β protein. Additionally, higher basal levels of antiviral factors (IRF7, CXCL10 and OAS1) were observed in uninfected SK1⁻/⁻  iMEFs but not 1°MEFs. This suggests that, in this single iMEF line, lack of SK1 upregulates the basal levels of factors that may protect cells against DENV infection. More importantly, regardless of the levels of DENV replication, all cells that lacked SK1 produced IFN-β but were refractory to induction of ISGs such as viperin, IFIT1 and CXCL10. Based on these findings, we propose new roles for SK1 in affecting innate responses that regulate susceptibility to DENV infection.

The Interferon-induced Transmembrane Proteins, IFITM1, IFITM2, and IFITM3 Inhibit Hepatitis C Virus Entry

The interferon-induced transmembrane (IFITM) family of proteins have recently been identified as important host effector molecules of the type I interferon response against viruses. IFITM1 has been identified as a potent antiviral effector against hepatitis C virus (HCV), whereas the related family members IFITM2 and IFITM3 have been described to have antiviral effects against a broad range of RNA viruses. Here, we demonstrate that IFITM2 and IFITM3 play an integral role in the interferon response against HCV and act at the level of late entry stages of HCV infection. We have established that in hepatocytes, IFITM2 and IFITM3 localize to the late and early endosomes, respectively, as well as the lysosome. Furthermore, we have demonstrated that S-palmitoylation of all three IFITM proteins is essential for anti-HCV activity, whereas the conserved tyrosine residue in the N-terminal domain of IFITM2 and IFITM3 plays a significant role in protein localization. However, this tyrosine was found to be dispensable for anti-HCV activity, with mutation of the tyrosine resulting in an IFITM1-like phenotype with the retention of anti-HCV activity and co-localization of IFITM2 and IFITM3 with CD81. In conclusion, we propose that the IFITM proteins act in a coordinated manner to restrict HCV infection by targeting the endocytosed HCV virion for lysosomal degradation and demonstrate that the actions of the IFITM proteins are indeed virus and cell-type specific.

Sequence analysis and characterisation of virally induced viperin in the saltwater crocodile (Crocodylus porosus)

A number of pathogens have been detected in crocodiles, however little is known about their ability to control these pathogens. The interferon stimulated gene (ISG), viperin, has gained attention recently as an important host protein involved in multiple arms of the immune response. Viperin in concert with a number of other ISGs was upregulated in response to viral nucleic acid mimics and sendai virus in the C. porosus cell line, LV-1, indicating an intact early innate response to viral infection in these animals for the first time. Viperin was cloned from the LV-1 cell line and shown to have similar localisation patterns as human viperin, as well as demonstrating extremely high conservation with the human orthologue, excepting at the N-terminus. Interestingly, C. porosus viperin was also able to inhibit Dengue virus replication in vitro, showing a high level of intact functionality for this protein across divergent animal species, and perhaps demonstrating its importance in the early innate response to pathogens in the animal kingdom.

Dengue Virus Infection of Primary Endothelial Cells Induces Innate Immune Responses, Changes in Endothelial Cells Function and Is Restricted by Interferon-Stimulated Responses

Although endothelial cell (EC) infection is not widespread during dengue virus (DENV) infection in vivo, the endothelium is the site of the pathogenic effects seen in severe DENV disease. In this study, we investigated DENV infection of primary EC and defined factors that influence infection in this cell type. Consistent with in vivo findings where EC infection is infrequent, only 3%-15% of EC became productively DENV-2-infected in vitro. This low level infection could not be attributed to inhibition by heparin, EC donor variation, heterogeneity, or biological source. DENV-infection of EC was associated with induction of innate immune responses, including increased STAT1 protein, STAT1- phosphorylation, interferon (IFN)-β, OAS-1, IFIT-1/ISG56, and viperin mRNA. Antibody blocking of IFN-β inhibited the induction of OAS1, IFIT1/ISG56, and viperin while shRNA knockdown of viperin enhanced DENV-infection in EC. DENV-infection of EC resulted in increased activity of sphingosine kinase 1, a factor important in maintaining vascular integrity, and altered basal and stimulated changes in barrier integrity of DENV-infected EC monolayers. Thus, DENV productively infects only a small percentage of primary EC but this has a major influence on induction of IFN-β driven innate immune responses that can restrict infection while the EC themselves are functionally altered. These changes may have important consequences for the endothelium and are reflective of pathogenic changes associated with vascular leakage, as seen in DENV disease.

Fatty Acids Induce a Pro-Inflammatory Gene Expression Profile in Huh-7 Cells That Attenuates the Anti-HCV Action of Interferon

The pathogenesis of nonalcoholic steatohepatitis is primarily an immune-driven disease and a known factor associated with treatment failure of chronic hepatitis C with interferon (IFN) and ribavirin. We studied the hepatocyte response in a model of steatosis at the transcriptome level and the antiviral action of IFN against hepatitis C virus (HCV) in this setting. In this study, we have shown that lipid loading (oleic acid and palmitic acid, OA:PA) of Huh-7 cells leads to increased expression of classical interferon-stimulated genes (ISGs) and NF-κβ-dependent pro-inflammatory genes. A selective blocker of Toll-like receptor (TLR)2 signaling suppressed NF-κβ promoter activity by OA:PA, suggesting that free fatty acids (FFAs) act as a TLR2 pathogen-associated molecular pattern. Furthermore, in the presence of OA:PA, IFN stimulation and HCV infection (Jc1) increased ISG expression. Somewhat counterintuitive to the increase in ISGs, the anti-HCV activity of IFN was attenuated in the presence of OA:PA. Interestingly, the combination of OA:PA, HCV, and IFN-α stimulation resulted in a significant increase in CXCL8 protein production, a cytokine known to have anti-IFN modulating activity. Thus, in an in vitro model of steatosis, the FFAs OA and PA drive an NF-κβ-dependent inflammatory and ISG gene expression profile via TLR2 activation. Furthermore, FFA synergistically increases IFN-driven gene expression that may account for HCV treatment failure in vivo.

Current and future targets of antiviral therapy in the hepatitis C virus life cycle

ABSTRACT 

Advances in our understanding of the hepatitis C virus (HCV) life cycle have enabled the development of numerous clinically advanced direct-acting antivirals. Indeed, the recent approval of first-generation direct-acting antivirals that target the viral NS3–4A protease and NS5B RNA-dependent RNA polymerase brings closer the possibility of universally efficacious and well-tolerated antiviral therapies for this insidious infection. However, the complexities of comorbidities, unforeseen side effects or drug–drug interactions, viral diversity, the high mutation rate of HCV RNA replication and the elegant and constantly evolving mechanisms employed by HCV to evade host and therapeutically implemented antiviral strategies remain as significant obstacles to this goal. Here, we review advances in our understanding of the HCV life cycle and associated opportunities for antiviral therapy.

Signal transducer and activator of transcription 3 is a proviral host factor for hepatitis C virus

Host factors play an important role in all facets of the hepatitis C virus (HCV) life cycle and one such host factor is signal transducer and activator of transcription 3 (STAT3). The HCV core protein has been shown to directly interact with and activate STAT3, while oxidative stress generated during HCV replication in a replicon-based model also induced STAT3 activation. However, despite these findings the precise role of STAT3 in the HCV life cycle remains unknown. We have established that STAT3 is actively phosphorylated in the presence of replicating HCV. Furthermore, expression of a constitutively active form of STAT3 leads to marked increases in HCV replication, whereas, conversely, chemical inhibition and small interfering RNA (siRNA) knockdown of STAT3 leads to significant decreases in HCV RNA levels. This strongly implicates STAT3 as a proviral host factor. As STAT3 is a transcription factor, up-regulation of a distinct set of STAT3-dependent genes may create an environment that is favorable for HCV replication. However, STAT3 has recently been demonstrated to positively regulate microtubule (MT) dynamics, by way of a direct sequestration of the MT depolymerizing protein Stathmin 1 (STMN1), and we provide evidence that STAT3 may exert its effect on the HCV life cycle by way of positive regulation of MT dynamics.

CONCLUSION

We have demonstrated that STAT3 plays a role in the life cycle of HCV and have clarified the role of STAT3 as a proviral host factor.

The role of viperin in the innate antiviral response

Viral infection of the cell is able to initiate a signaling cascade of events that ultimately attempts to limit viral replication and prevent escalating infection through expression of host antiviral proteins. Recent work has highlighted the importance of the host antiviral protein viperin in this process, with its ability to limit a large variety of viral infections as well as play a role in the production of type I interferon and the modulation of a number of transcription factor binding sites. Viperin appears to have the ability to modulate varying conditions within the cell and to interfere with proviral host proteins in its attempts to create an unfavorable environment for viral replication. The study of the mechanistic actions of viperin has come a long way in recent years, describing important functional domains of the protein for its antiviral and immune modulator actions as well as demonstrating its role as a member of the radical SAM enzyme family. However, despite the rapid expansion of knowledge regarding the functions of this highly conserved and ancient antiviral protein, there still remains large gaps in our understanding of the precise mechanisms at play for viperin to exert such a wide variety of roles within the cell.

Viperin is induced following dengue virus type-2 (DENV-2) infection and has anti-viral actions requiring the C-terminal end of viperin

The host protein viperin is an interferon stimulated gene (ISG) that is up-regulated during a number of viral infections. In this study we have shown that dengue virus type-2 (DENV-2) infection significantly induced viperin, co-incident with production of viral RNA and via a mechanism requiring retinoic acid-inducible gene I (RIG-I). Viperin did not inhibit DENV-2 entry but DENV-2 RNA and infectious virus release was inhibited in viperin expressing cells. Conversely, DENV-2 replicated to higher tires earlier in viperin shRNA expressing cells. The anti-DENV effect of viperin was mediated by residues within the C-terminal 17 amino acids of viperin and did not require the N-terminal residues, including the helix domain, leucine zipper and S-adenosylmethionine (SAM) motifs known to be involved in viperin intracellular membrane association. Viperin showed co-localisation with lipid droplet markers, and was co-localised and interacted with DENV-2 capsid (CA), NS3 and viral RNA. The ability of viperin to interact with DENV-2 NS3 was associated with its anti-viral activity, while co-localisation of viperin with lipid droplets was not. Thus, DENV-2 infection induces viperin which has anti-viral properties residing in the C-terminal region of the protein that act to restrict early DENV-2 RNA production/accumulation, potentially via interaction of viperin with DENV-2 NS3 and replication complexes. These anti-DENV-2 actions of viperin show both contrasts and similarities with other described anti-viral mechanisms of viperin action and highlight the diverse nature of this unique anti-viral host protein.

The interferon signaling pathway genes as biomarkers of hepatitis C virus disease progression and response to treatment

Hepatitis C virus is an ever-increasing worldwide health problem with over 350,000 individuals succumbing to hepatitis C virus-related liver diseases each year. The ability to determine the outcome of an acute-phase illness may be useful in terms of implementing treatment strategies; however, to date, the predictive associations in the literature have centered around candidate gene analysis. Much greater advancements have been made in describing biomarkers from the activation of the host innate immune response, such as the interferon system, for prediction of treatment outcome in chronic hepatitis C with the advent of genome-wide association studies. Recent times has seen a major breakthrough in the field with the description of the IL28B genotype as an independent association factor for pegylated IFN-α2b/ribavirin treatment response. The ability to couple this with other easily measured biomarkers such as the interferon-stimulated gene CXCL10, serum concentration may make this predictive marker set very useful in the clinical setting.

Osteopontin increases hepatocellular carcinoma cell growth in a CD44 dependant manner

AIM: To investigate the role of osteopontin (OPN) and its splice variants in the proliferation of hepatocellular carcinoma (HCC).

METHODS: The expression of OPN variants in HCC cell lines as well as HCC tissue samples and non-tumour tissue was studied using polymerase chain reaction. OPN variant cDNAs were cloned into a mammalian expression vector allowing both transient expression and the production of stable OPN expressing cell lines. OPN expression was studied in these cells using Western blotting, immunofluoresnce and enzyme linked immunosorbent assay. A CD44 blocking antibody and siRNA targeting of CD44 were used to examine the role of this receptor in the OPN stimulated cell growth observed in culture. Huh-7 cells stably expressing either OPN-A, -B or -C were injected subcutaneously into the flanks of nude mice to observe in vivo tumour growth. Expression of OPN mRNA and protein in these tumours was examined using reverse transcription-polymerase chain reaction and immunohistochemistry.

RESULTS: OPN is expressed in HCC in 3 forms, the full length OPN-A and 2 splice variants OPN-B and -C. OPN variant expression was noted in HCC tissue as well as cognate surrounding cirrhotic liver tissue. Expression of these OPN variants in the HCC derived cell line Huh-7 resulted in secretion of OPN into the culture medium. Transfer of OPN conditioned media to naïve Huh-7 and HepG2 cells resulted in significant cell growth suggesting that all OPN variants can modulate cell proliferation in a paracrine manner. Furthermore the OPN mediated increase in cellular proliferation was dependent on CD44 as only CD44 positive cell lines responded to OPN conditioned media while siRNA knockdown of CD44 blocked the proliferative effect. OPN expression also increased the proliferation of Huh-7 cells in a subcutaneous nude mouse tumour model, with Huh-7 cells expressing OPN-A showing the greatest proliferative effect.

CONCLUSION: This study demonstrates that OPN plays a significant role in the proliferation of HCC through interaction with the cell surface receptor CD44. Modulation of this interaction could represent a novel strategy for the control of HCC.

The antiviral protein viperin inhibits hepatitis C virus replication via interaction with nonstructural protein 5A

The interferon-stimulated gene, viperin, has been shown to have antiviral activity against hepatitis C virus (HCV) in the context of the HCV replicon, although the molecular mechanisms responsible are not well understood. Here, we demonstrate that viperin plays an integral part in the ability of interferon to limit the replication of cell-culture-derived HCV (JFH-1) that accurately reflects the complete viral life cycle. Using confocal microscopy and fluorescence resonance energy transfer (FRET) analysis, we demonstrate that viperin localizes and interacts with HCV nonstructural protein 5A (NS5A) at the lipid-droplet (LD) interface. In addition, viperin also associates with NS5A and the proviral cellular factor, human vesicle-associated membrane protein-associated protein subtype A (VAP-A), at the HCV replication complex. The ability of viperin to limit HCV replication was dependent on residues within the C-terminus, as well as an N-terminal amphipathic helix. Removal of the amphipathic helix-redirected viperin from the cytosolic face of the endoplasmic reticulum and the LD to a homogenous cytoplasmic distribution, coinciding with a loss of antiviral effect. C-terminal viperin mutants still localized to the LD interface and replication complexes, but did not interact with NS5A proteins, as determined by FRET analysis.

CONCLUSION

In conclusion, we propose that viperin interacts with NS5A and the host factor, VAP-A, to limit HCV replication at the replication complex. This highlights the complexity of the host control of viral replication by interferon-stimulated gene expression.

Alcohol metabolism increases the replication of hepatitis C virus and attenuates the antiviral action of interferon

The interactions between hepatitis C virus (HCV) and alcohol metabolism are not well understood. To determine the effect that alcohol metabolism has on HCV replication and the antiviral action of interferon (IFN), Huh-7 cells that harbor HCV replication and metabolize ethanol via the introduced expression of cytochrome P450 2E1 (Cyp2e1) were treated with ethanol and IFN-alpha. Treatment of these cells with ethanol (0-100 mmol/L) significantly increased HCV replication. This effect was dependent on Cyp2e1 expression and alcohol-metabolized oxidative stress (OS), because the antioxidant N-acetylcysteine blocked this effect. Furthermore, the anti-HCV action of IFN-alpha was attenuated in the presence of ethanol metabolism, most likely via attenuation of Stat1 tyrosine-701 phosphorylation. These in vitro results mimic what is often noted clinically, and further dissection of this model system will aid in our understanding of interactions between HCV and alcohol metabolism.

A screening method for identifying disruptions in interferon signaling reveals HCV NS3/4a disrupts Stat-1 phosphorylation

Viruses have evolved mechanisms to inhibit the innate immune response to infection. The aim of this study was to develop an efficient screening method to identify viral proteins and their ability to block Jak-Stat signaling using hepatitis C virus (HCV) as an example. The 2FTGH cell assay system was used in combination with transient transfection of HCV proteins in this study. Using 1000U/ml IFN and 30mM 6-TG to treat 2FTGH cells, it was established that transient protein expression in this cell system yielded 39% and 0% cell survival for the positive (HPV E7) and negative controls (GFP expression) respectively. Transient expression of HCV Core-p7 resulted in 22% cell survival, consistent with previous reports, while expression of the HCV serine protease NS3/4a resulted in 54% cell survival. NS3/4a was subsequently shown to inhibit phosphorylation of Stat-1 at the serine residue 727.

CONCLUSION

the 2FTGH cell assay system can be adapted for transient screening to examine the ability of viral proteins or other potential inhibitors to block the Jak-Stat signaling pathway. We show that HCV NS3/4a is able to block this pathway at the stage of Stat-1 serine 727 phosphorylation.

Analysis of ISG expression in chronic hepatitis C identifies viperin as a potential antiviral effector

Interferon (IFN) alpha inhibits hepatitis C virus (HCV) replication both clinically and in vitro; however, the complete spectrum of interferon-stimulated genes (ISGs) expressed in the HCV-infected liver or the genes responsible for control of HCV replication have not been defined. To better define ISG expression in the chronically infected HCV liver, DNA microarray analysis was performed on 9 individuals with chronic hepatitis C (CHC). A total of 232 messenger RNAs were differentially regulated in CHC compared with nondiseased liver controls. A significant proportion of these were potential ISGs that were transcriptionally elevated, suggesting an ongoing response to endogenous IFN and/or double-stranded RNA. One ISG significantly elevated in all patients was viperin, an evolutionary conserved ISG that has antiviral activity against human cytomegalovirus. Stimulation of Huh-7 and HepG2 cells with IFN-alpha or -gamma revealed viperin is predominantly a type I ISG. Furthermore, viperin expression could also be induced following transfection of Huh-7 cells with either poly(I:C) or HCV RNA. Transient expression of viperin in cells harboring the HCV genomic replicon resulted in a significant decrease in HCV replication, suggesting that viperin has anti-HCV activity. In conclusion, even in the face of a persistent HCV infection, there is an active ISG antiviral cellular response, highlighting the complexity of the host viral relationship. Furthermore, ISG viperin has anti-HCV activity in vitro; we postulate that viperin, along with other ISGs, acts to limit HCV replication.

A novel I-TAC promoter polymorphic variant is functional in the presence of replicating HCV in vitro

BACKGROUND

Chemokines are strong candidate genes for outcome of HCV infection. I-TAC is a chemokine known to be involved in the inflammatory process of HCV infection, and its expression is upregulated in chronic hepatitis C (CHC).

OBJECTIVES

The aim of this study was to investigate genetic variability in the I-TAC promoter and to determine the correlation of these variants with HCV disease progression.

STUDY DESIGN

I-TAC genotyping was performed in 60 chronic HCV patients and 60 controls using GeneScan analysis. Functional analysis of the I-TAC promoter was performed with the aid of luciferase reporter constructs transfected into Huh-7 cells or Huh-7 cells harbouring HCV genomic and sub-genomic replicons. Cytokine induced production of I-TAC from whole blood cultures was measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Sequencing of approximately 1 kb upstream of the I-TAC gene start codon revealed the presence of a novel 5 bp deletion mutant (-599del5) in a number of chronic HCV patients. Analysis of the functional potential of this deletion revealed no transcriptional change in Huh-7 cells transfected with luciferase reporter constructs, and this was confirmed in cytokine stimulated whole blood cultures where similar levels of I-TAC were liberated regardless of -599del5 genotype. Conversely, the -599del5 deletion variant significantly reduced transcriptional activity of the I-TAC promoter in the presence of replicating HCV. The distribution frequency of the allele was found to be significantly increased in a chronically HCV infected population compared to healthy controls.

CONCLUSIONS

The novel I-TAC -599del5 promoter polymorphism is a functional variant in the presence of replicating HCV. Furthermore, this deletion mutant is significantly increased in a chronic HCV cohort and may predispose to HCV disease susceptibility.

Expression of the CXCR3 ligand I-TAC by hepatocytes in chronic hepatitis C and its correlation with hepatic inflammation

The factors that regulate lymphocyte traffic in chronic hepatitis C (CHC) are not completely defined. Interferon (IFN)-inducible T cell alpha chemoattractant (I-TAC) is a relatively new member of the CXCR3 chemokine ligand family that selectively recruits activated T cells to sites of inflammation. To determine if I-TAC plays a role in CHC, we investigated I-TAC expression in hepatitis C virus (HCV)-infected liver biopsy material. I-TAC messenger RNA (mRNA) levels were significantly increased in HCV-infected liver compared with normal liver, which correlated with both portal and lobular inflammation. I-TAC expression was localized to hepatocytes throughout the liver lobule, with those in close proximity to active areas of inflammation expressing the highest concentration of I-TAC. In vitro, I-TAC mRNA and protein expression was inducible in Huh-7 cells following either IFN-alpha or -gamma stimulation and synergistically with tumor necrosis factor (TNF)-alpha. Furthermore, transfection of Huh-7 cells with either poly(I:C) or HCV RNA representing the HCV subgenomic replicon induced I-TAC mRNA expression. HCV replication was also found to modulate I-TAC expression, with stimulation of Huh-7 cells harboring either the HCV subgenomic or genomic replicon showing significantly increased synergistic effects compared with those previously seen in Huh-7 cells alone with IFN-gamma and TNF-alpha. In conclusion, these results suggest I-TAC, one of the most potent chemoattractants for activated T cells, is produced by hepatocytes in the HCV-infected liver and plays an important role in T cell recruitment and ultimately the pathogenesis of CHC.

Variation in immune response genes and chronic Q fever. Concepts: preliminary test with post-Q fever fatigue syndrome

Acute primary Q fever is followed by various chronic sequelae. These include subacute Q fever endocarditis, granulomatous reactions in various organs or a prolonged debilitating post-infection fatigue syndrome (QFS). The causative organism, Coxiella burnetii, persists after an initial infection. The differing chronic outcomes may reflect variations within cytokine and accessory immune control genes which affect regulation of the level of persistence. As a preliminary test of the concept we have genotyped QFS patients and controls for gene variants spanning 15 genes and also examined HLA-B and DR frequencies. QFS patients exhibited a significantly increased frequency of HLA-DR-11 compared with controls and also significant differences in allelic variant frequencies within the NRAMP, and IFNgamma genes. These results indicate a possible genetic role in the expression of overt chronic Q fever. Further studies will be undertaken to increase sample sizes, to survey other forms of chronic Q fever and to examine Q fever patients who have recovered without sequelae.