Hepatitis C virus production by human hepatocytes dependent on assembly and secretion of very low-density lipoproteins

Impaired ApoB secretion triggers enhanced secretion of ApoE to maintain triglyceride homeostasis in hepatoma cells

Apolipoprotein B (ApoB) is essential for the assembly and secretion of triglyceride (TG)-rich VLDL particles, and its dysfunction is linked to metabolic disorders, including dyslipidemia and liver steatosis. However, less attention has been paid to whether and how other apolipoproteins play redundant or compensatory roles when the ApoB function is compromised. Here, we investigated the effects of microsomal triglyceride transfer protein (MTP), which mediates lipidation of nascent ApoB, on ApoE function. We observed a paradoxical increase in ApoE secretion resulting from increased expression in MTP inhibitor (MTPi)-treated human hepatoma cells. This phenotype was recapitulated in APOB-knockout cells and was associated with impaired ApoB secretion. While MTP-dependent transfer of neutral lipids is dispensable for ApoE secretion, TG biosynthesis, redundantly catalyzed by DGAT1 and DGAT2, is required for efficient ApoE secretion in hepatoma cells. ApoE colocalizes with lipid droplets near the Golgi apparatus and mediates TG export in an ApoB-independent fashion. We found that simultaneous inhibition of both ApoE and ApoB, but not inhibition of either alone, led to TG accumulation in hepatoma cells, indicating that both proteins function redundantly to control TG content. Validation studies in primary human hepatocytes (PHHs) demonstrated DGAT2-dependent secretion of ApoE. While MTPi treatment did not elevate ApoE secretion, it induced increased sialylation of ApoE in the supernatants of PHHs. These results show that enhanced ApoE secretion compensates for the impaired ApoB function to maintain the lipid homeostasis, providing an alternative route to modulate lipid turnover in hepatoma cells.

Host-targeting antivirals for chronic viral infections of the liver

Infection with one or several of the five known hepatitis viruses is a leading cause of liver disease and poses a high risk of developing hepatocellular carcinoma upon chronic infection. Chronicity is primarily caused by hepatitis B virus (HBV) and hepatitis C virus (HCV) and poses a significant health burden worldwide. Co-infection of chronic HBV infected patients with hepatitis D virus (HDV) is less common but is marked as the most severe form of chronic viral hepatitis. Hepatitis A virus (HAV) and hepatitis E virus (HEV) primarily cause self-limiting acute hepatitis. However, studies have also reported chronic progression of HEV disease in immunocompromised patients. While considerable progress has been made in the treatment of HCV and HBV through the development of direct-acting antivirals (DAAs), challenges including drug resistance, incomplete viral suppression resulting in failure to achieve clearance and the lack of effective treatment options for HDV and HEV remain. Host-targeting antivirals (HTAs) have emerged as a promising alternative approach to DAAs and aim to disrupt virus-host interactions by modulating host cell pathways that are hijacked during the viral replication cycle. The aim of this review is to provide a comprehensive overview about the major milestones in research and development of HTAs for chronic HBV/HDV and HCV infections. It also summarizes the current state of knowledge on promising host-targeting therapeutic options against HEV infection.

Diverting hepatic lipid fluxes with lifestyles revision and pharmacological interventions as a strategy to tackle steatotic liver disease (SLD) and hepatocellular carcinoma (HCC)

Steatotic liver disease (SLD) and Hepatocellular Carcinoma (HCC) are characterised by a substantial rewiring of lipid fluxes caused by systemic metabolic unbalances and/or disrupted intracellular metabolic pathways. SLD is a direct consequence of the interaction between genetic predisposition and a chronic positive energy balance affecting whole-body energy homeostasis and the function of metabolically-competent organs. In this review, we discuss how the impairment of the cross-talk between peripheral organs and the liver stalls glucose and lipid metabolism, leading to unbalances in hepatic lipid fluxes that promote hepatic fat accumulation. We also describe how prolonged metabolic stress builds up toxic lipid species in the liver, and how lipotoxicity and metabolic disturbances drive disease progression by promoting a chronic activation of wound healing, leading to fibrosis and HCC. Last, we provide a critical overview of current state of the art (pre-clinical and clinical evidence) regarding mechanisms of action and therapeutic efficacy of candidate SLD treatment options, and their potential to interfere with SLD/HCC pathophysiology by diverting lipids away from the liver therefore improving metabolic health.

HDL-based therapeutics: A promising frontier in combating viral and bacterial infections

Low levels of high-density lipoprotein (HDL) and impaired HDL functionality have been consistently associated with increased susceptibility to infection and its serious consequences. This has been attributed to the critical role of HDL in maintaining cellular lipid homeostasis, which is essential for the proper functioning of immune and structural cells. HDL, a multifunctional particle, exerts pleiotropic effects in host defense against pathogens. It functions as a natural nanoparticle, capable of sequestering and neutralizing potentially harmful substances like bacterial lipopolysaccharides. HDL possesses antiviral activity, preventing viruses from entering or fusing with host cells, thereby halting their replication cycle. Understanding the complex relationship between HDL and the immune system may reveal innovative targets for developing new treatments to combat infectious diseases and improve patient outcomes. This review aims to emphasize the role of HDL in influencing the course of bacterial and viral infections and its and its therapeutic potential.

After the Storm: Persistent Molecular Alterations Following HCV Cure

The development of direct-acting antivirals (DAAs) against hepatitis C virus (HCV) has revolutionized the management of this pathology, as their use allows viral elimination in a large majority of patients. Nonetheless, HCV remains a major public health problem due to the multiple challenges associated with its diagnosis, treatment availability and development of a prophylactic vaccine. Moreover, HCV-cured patients still present an increased risk of developing hepatic complications such as hepatocellular carcinoma. In the present review, we aim to summarize the impact that HCV infection has on a wide variety of peripheral and intrahepatic cell populations, the alterations that remain following DAA treatment and the potential molecular mechanisms implicated in their long-term persistence. Finally, we consider how recent developments in single-cell multiomics could refine our understanding of this disease in each specific intrahepatic cell population and drive the field to explore new directions for the development of chemo-preventive strategies.

Chronic Hepatitis C Virus Infection, Extrahepatic Disease and the Impact of New Direct-Acting Antivirals

Chronic hepatitis C virus infection is an important cause of liver cirrhosis, hepatocellular carcinoma and death. Furthermore, it is estimated that about 40-70% of patients develop non-hepatic alterations in the course of chronic infection. Such manifestations can be immune-related conditions, lymphoproliferative disorders and metabolic alterations with serious adverse events in the short and long term. The introduction of new Direct-Acting Antivirals has shown promising results, with current evidence indicating an improvement and remission of these conditions after a sustained virological response.

Landscape of protein-protein interactions during hepatitis C virus assembly and release

Assembly of infectious hepatitis C virus (HCV) particles requires multiple cellular proteins including for instance apolipoprotein E (ApoE). To describe these protein-protein interactions, we performed an affinity purification mass spectrometry screen of HCV-infected cells. We used functional viral constructs with epitope-tagged envelope protein 2 (E2), protein (p) 7, or nonstructural protein 4B (NS4B) as well as cells expressing a tagged variant of ApoE. We also evaluated assembly stage-dependent remodeling of protein complexes by using viral mutants carrying point mutations abrogating particle production at distinct steps of the HCV particle production cascade. Five ApoE binding proteins, 12 p7 binders, 7 primary E2 interactors, and 24 proteins interacting with NS4B were detected. Cell-derived PREB, STT3B, and SPCS2 as well as viral NS2 interacted with both p7 and E2. Only GTF3C3 interacted with E2 and NS4B, highlighting that HCV assembly and replication complexes exhibit largely distinct interactomes. An HCV core protein mutation, preventing core protein decoration of lipid droplets, profoundly altered the E2 interactome. In cells replicating this mutant, E2 interactions with HSPA5, STT3A/B, RAD23A/B, and ZNF860 were significantly enhanced, suggesting that E2 protein interactions partly depend on core protein functions. Bioinformatic and functional studies including STRING network analyses, RNA interference, and ectopic expression support a role of Rad23A and Rad23B in facilitating HCV infectious virus production. Both Rad23A and Rad23B are involved in the endoplasmic reticulum (ER)-associated protein degradation (ERAD). Collectively, our results provide a map of host proteins interacting with HCV assembly proteins, and they give evidence for the involvement of ER protein folding machineries and the ERAD pathway in the late stages of the HCV replication cycle.IMPORTANCEHepatitis C virus (HCV) establishes chronic infections in the majority of exposed individuals. This capacity likely depends on viral immune evasion strategies. One feature likely contributing to persistence is the formation of so-called lipo-viro particles. These peculiar virions consist of viral structural proteins and cellular lipids and lipoproteins, the latter of which aid in viral attachment and cell entry and likely antibody escape. To learn about how lipo-viro particles are coined, here, we provide a comprehensive overview of protein-protein interactions in virus-producing cells. We identify numerous novel and specific HCV E2, p7, and cellular apolipoprotein E-interacting proteins. Pathway analyses of these interactors show that proteins participating in processes such as endoplasmic reticulum (ER) protein folding, ER-associated protein degradation, and glycosylation are heavily engaged in virus production. Moreover, we find that the proteome of HCV replication sites is distinct from the assembly proteome, suggesting that transport process likely shuttles viral RNA to assembly sites.

Akt1 is involved in HCV release by promoting endoplasmic reticulum-to-endosome transition of infectious virions

AIMS

Hepatitis C virus (HCV) relies on the viral and host factors to complete its life cycle. It has evolved to profit from Akt activation at some stage in its life cycle through various mechanisms, notably by activating lipogenesis, which is crucial for infectious virions production.

MATERIALS AND METHODS

By employing an Akt-specific inhibitor, the impact of Akt on intracellular and extracellular infectivity was investigated. To ascertain the role of Akt in the HCV life cycle, the two-part cell culture-derived HCV infection protocol utilizing Akt1 small interfering RNAs (siRNAs) was implemented. The impact of Akt1 on intracellular HCV transition was determined using membrane flotation assay and proximity ligation assay coupled with Anti-Rab7 immunoprecipitation and immunofluorescence.

KEY FINDINGS

Akt1 silencing reduced infectious virions release to a degree comparable to that of ApoE, a host component involved in the HCV assembly and release, suggesting Akt1 was critical in the late stage of the HCV life cycle. Extracellular infectivity of HCV was inhibited by brefeldin A, and the inhibitory effect was augmented by Akt1 silencing and partially restored by ectopic Akt1 expression. Immunofluorescence revealed that Akt1 inhibition suppressed the interaction between HCV core protein and lipid droplet. Akt1 silencing impeded the transition of HCV from the endoplasmic reticulum to the endosome and hence inhibited the secretion of HCV infectious virions from the late endosome.

SIGNIFICANCE

Our study demonstrates that Akt1 has an impact on the lipogenesis pathway and plays a critical role in the assembly and secretion of infectious HCV.

Modulation of the replication of positive-sense RNA viruses by the natural plant metabolite xanthohumol and its derivatives

The COVID-19 pandemic has highlighted the importance of identifying new potent antiviral agents. Nutrients as well as plant-derived substances are promising candidates because they are usually well tolerated by the human body and readily available in nature, and consequently mostly cheap to produce. A variety of antiviral effects have recently been described for the hop chalcone xanthohumol (XN), and to a lesser extent for its derivatives, making these hop compounds particularly attractive for further investigation. Noteworthy, mounting evidence indicated that XN can suppress a wide range of viruses belonging to several virus families, all of which share a common reproductive cycle. As a result, the purpose of this review is to summarize the most recent research on the antiviral properties of XN and its derivatives, with a particular emphasis on the positive-sense RNA viruses human hepatitis C virus (HCV), porcine reproductive and respiratory syndrome virus (PRRSV), and severe acute respiratory syndrome corona virus (SARS-CoV-2).

Genetic and pharmacological perturbation of hepatitis-C virus entry

Hepatitis-C virus (HCV) chronically infects 58 million individuals worldwide with variable disease outcome. While a subfraction of individuals exposed to the virus clear the infection, the majority develop chronic infection if untreated. Another subfraction of chronically ill proceeds to severe liver disease. The underlying causes of this interindividual variability include genetic polymorphisms in interferon genes. Here, we review available data on the influence of genetic or pharmacological perturbation of HCV host dependency factors on the clinically observed interindividual differences in disease outcome. We focus on host factors mediating virus entry into human liver cells. We assess available data on genetic variants of the major entry factors scavenger receptor class-B type I, CD81, claudin-1, and occludin as well as pharmacological perturbation of these entry factors. We review cell culture experimental and clinical cohort study data and conclude that entry factor perturbation may contribute to disease outcome of hepatitis C.

Apolipoprotein E and viral infection: Risks and Mechanisms

Apolipoprotein E (ApoE) is a multifunctional protein critical for lipid metabolism and cholesterol homeostasis. In addition to being a well known genetic determinant of both neurodegenerative and cardiovascular diseases, ApoE is frequently involved in various viral infection-related diseases. Human ApoE protein is functionally polymorphic with three isoforms, namely, ApoE2, ApoE3, and ApoE4, with markedly altered protein structures and functions. ApoE4 is associated with increased susceptibility to infection with herpes simplex virus type-1 and HIV. Conversely, ApoE4 protects against hepatitis C virus and hepatitis B virus infection. With the outbreak of coronavirus disease 2019, ApoE4 has been shown to determine the incidence and progression of severe acute respiratory syndrome coronavirus 2 infection. These findings clearly indicate the critical role of ApoE in viral infection. Furthermore, ApoE polymorphism has various or even opposite effects in these infection processes, which are partly related to the structural features that distinguish the different ApoE statuses. In the current review, we summarize the emerging relationship between ApoE and viral infection, discuss the potential mechanisms, and identify future directions that may help to advance our understanding of the link between ApoE and viral infection.

Targeting the vital non-structural proteins (NSP12, NSP7, NSP8 and NSP3) from SARS-CoV-2 and inhibition of RNA polymerase by natural bioactive compound naringenin as a promising drug candidate against COVID-19

The prevalence of SARS-CoV-2-induced respiratory infections is now a major challenge worldwide. There is currently no specific antiviral drug to prevent or treat this disease. Infection with COVID-19 seriously needs to find effective therapeutic agents. In the present study, naringenin, as a potential inhibitor candidate for RNA Polymerase SARS-CoV-2 was compared with remdesivir (FDA-approved drug) and GS-441,524 (Derivative of the drug remdesivir) by screening with wild-type and mutant SARS-CoV-2 NSP12 (NSP7-NSP8) and NSP3 interfaces, then complexes were simulated by molecular dynamics (MD) simulations to gain their stabilities. The docking results displayed ​scores of -3.45 kcal/mol and -4.32 kcal/mol against NSP12 and NSP3, respectively. Our results showed that naringenin had ΔG values more negative than the ΔG values of Remdesivir (RDV) and GS-441,524. Hence, naringenin was considered to be a potential inhibitor. Also, the number of hydrogen bonds of naringenin with NSP3 and later NSP12 are more than Remdesivir and its derivative. In this research, Mean root mean square deviation (RMSD) values of NSP3 and NSP12with naringenin ligand (5.55±1.58 nm to 3.45±0.56 nm and 0.238±0.01 to 0.242±0.021 nm, respectively showed stability in the presence of ligand. The root mean square fluctuations (RMSF) values of NSP3 and NSP12 amino acid units in the presence of naringenin in were 1.5 ± 0.31 nm and 0.118±0.058, respectively. Pharmacokinetic properties and prediction of absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of naringenin and RDV showed that ​these two compounds had no potential cytotoxicity.

Naringenin: A flavanone with anti-inflammatory and anti-infective properties

Although a growing body of research has recently shown how crucial inflammation and infection are to all major diseases, several of the medications currently available on the market have various unfavourable side effects, necessitating the development of alternative therapeutic choices. Researchers are increasingly interested in alternative medications or active components derived from natural sources. Naringenin is a commonly consumed flavonoid found in many plants, and since it was discovered to have nutritional benefits, it has been utilized to treat inflammation and infections caused by particular bacteria or viruses. However, the absence of adequate clinical data and naringenin's poor solubility and stability severely restrict its usage as a medicinal agent. In this article, we discuss naringenin's effects and mechanisms of action on autoimmune-induced inflammation, bacterial infections, and viral infections based on recent research. We also present a few suggestions for enhancing naringenin's solubility, stability, and bioavailability. This paper emphasizes the potential use of naringenin as an anti-inflammatory and anti-infective agent and the next prophylactic substance for the treatment of various inflammatory and infectious diseases, even though some mechanisms of action are still unclear, and offers some theoretical support for its clinical application.

Hepatitis C Virus (HCV)-Ribonucleic Acid (RNA) As a Biomarker for Lymphoid Malignancy with HCV Infection

The hepatitis C virus (HCV) is potentially associated with liver cancer, and advances in various drugs have led to progress in the treatment of hepatitis C and attempts to prevent its transition to liver cancer. Furthermore, reactivation of HCV has been observed in the treatment of lymphoma, during which the immortalization and proliferation of lymphocytes occur, which leads to the possibility of further stimulating cytokines and the like and possibly to the development of lymphoid malignancy. There are also cases in which the disappearance of lymphoid malignancy has been observed by treating HCV and suppressing HCV-Ribonucleic acid (RNA), as well as cases of recurrence with an increase in HCV-RNA. While HCV-associated lymphoma has a poor prognosis, improving the prognosis with Direct Acting Antivirals (DAA) has recently been reported. The reduction and eradication of HCV-RNA by means of DAA is thus important for the treatment of lymphoid malignancy associated with HCV infection, and HCV-RNA can presumably play a role as a biomarker. This review provides an overview of what is currently known about HCV-associated lymphoma, its epidemiology, the mechanisms underlying the progression to lymphoma, its treatment, the potential and limits of HCV-RNA as a therapeutic biomarker, and biomarkers that are expected now that DAA therapy has been developed.

Research progress on the role of RNA N6-methyladenosine methylation in HCV infection

Hepatitis C virus (HCV) is a positive-stranded RNA virus causing chronic liver diseases. The chemical modification of RNA is a research hotspot in related fields in recent years, including the methylation and acetylation of adenine, guanine, cytosine and other bases, among which methylation is the most important modification form. m⁶A (N⁶-methyladenosine), as the most abundant RNA modification form, plays an important role in HCV virus infection by modifying viral RNA and cell transcripts. This review aims to summarize the current knowledge on the roles of m⁶A modification in HCV infection, and discuss the research prospect.

Mechanisms of Action of the Host-Targeting Agent Cyclosporin A and Direct-Acting Antiviral Agents against Hepatitis C Virus

Several direct-acting antivirals (DAAs) are available, providing interferon-free strategies for a hepatitis C cure. In contrast to DAAs, host-targeting agents (HTAs) interfere with host cellular factors that are essential in the viral replication cycle; as host genes, they are less likely to rapidly mutate under drug pressure, thus potentially exhibiting a high barrier to resistance, in addition to distinct mechanisms of action. We compared the effects of cyclosporin A (CsA), a HTA that targets cyclophilin A (CypA), to DAAs, including inhibitors of nonstructural protein 5A (NS5A), NS3/4A, and NS5B, in Huh7.5.1 cells. Our data show that CsA suppressed HCV infection as rapidly as the fastest-acting DAAs. CsA and inhibitors of NS5A and NS3/4A, but not of NS5B, suppressed the production and release of infectious HCV particles. Intriguingly, while CsA rapidly suppressed infectious extracellular virus levels, it had no significant effect on the intracellular infectious virus, suggesting that, unlike the DAAs tested here, it may block a post-assembly step in the viral replication cycle. Hence, our findings shed light on the biological processes involved in HCV replication and the role of CypA.

The role of human lipoproteins for hepatitis C virus persistence

Hepatitis C virus (HCV) is a hepatotropic virus that establishes a chronic infection in most individuals. Effective treatments are available; however, many patients are not aware of their infection. Consequently, they do not receive treatment and HCV transmission remains high, particularly among groups at high risk of exposure such as people who inject intravenous drugs. A prophylactic vaccine may reduce HCV transmission, but is currently not available. HCV has evolved immune evasion strategies, which facilitate persistence and complicate development of a protective vaccine. The peculiar association of HCV particles with human lipoproteins is thought to facilitate evasion from humoral immune response and viral homing to liver cells. A better understanding of these aspects provides the basis for development of protective vaccination strategies. Here, we review key information about the composition of HCV particles, the mechanisms mediating lipoprotein incorporation, and the functional consequences of this interaction.

Hepatitis C Virus-Lipid Interplay: Pathogenesis and Clinical Impact

Hepatitis C virus (HCV) infection represents the major cause of chronic liver disease, leading to a wide range of hepatic diseases, including cirrhosis and hepatocellular carcinoma. It is the leading indication for liver transplantation worldwide. In addition, there is a growing body of evidence concerning the role of HCV in extrahepatic manifestations, including immune-related disorders and metabolic abnormalities, such as insulin resistance and steatosis. HCV depends on its host cells to propagate successfully, and every aspect of the HCV life cycle is closely related to human lipid metabolism. The virus circulates as a lipid-rich particle, entering the hepatocyte via lipoprotein cell receptors. It has also been shown to upregulate lipid biosynthesis and impair lipid degradation, resulting in significant intracellular lipid accumulation (steatosis) and circulating hypocholesterolemia. Patients with chronic HCV are at increased risk for hepatic steatosis, dyslipidemia, and cardiovascular disease, including accelerated atherosclerosis. This review aims to describe different aspects of the HCV viral life cycle as it impacts host lipoproteins and lipid metabolism. It then discusses the mechanisms of HCV-related hepatic steatosis, hypocholesterolemia, and accelerated atherosclerosis.

The Role of Cytosolic Lipid Droplets in Hepatitis C Virus Replication, Assembly, and Release

The hepatitis C virus (HCV) causes chronic hepatitis by establishing a persistent infection. Patients with chronic hepatitis frequently develop hepatic cirrhosis, which can lead to liver cancer-the progressive liver damage results from the host's immune response to the unresolved infection. The HCV replication process, including the entry, replication, assembly, and release stages, while the virus circulates in the bloodstream, it is intricately linked to the host's lipid metabolism, including the dynamic of the cytosolic lipid droplets (cLDs). This review article depicts how this interaction regulates viral cell tropism and aids immune evasion by coining viral particle characteristics. cLDs are intracellular organelles that store most of the cytoplasmic components of neutral lipids and are assumed to play an increasingly important role in the pathophysiology of lipid metabolism and host-virus interactions. cLDs are involved in the replication of several clinically significant viruses, where viruses alter the lipidomic profiles of host cells to improve viral life cycles. cLDs are involved in almost every phase of the HCV life cycle. Indeed, pharmacological modulators of cholesterol synthesis and intracellular trafficking, lipoprotein maturation, and lipid signaling molecules inhibit the assembly of HCV virions. Likewise, small-molecule inhibitors of cLD-regulating proteins inhibit HCV replication. Thus, addressing the molecular architecture of HCV replication will aid in elucidating its pathogenesis and devising preventive interventions that impede persistent infection and prevent disease progression. This is possible via repurposing the available therapeutic agents that alter cLDs metabolism. This review highlights the role of cLD in HCV replication.

An Update on the Metabolic Landscape of Oncogenic Viruses

Viruses play an important role in cancer development as about 12% of cancer types are linked to viral infections. Viruses that induce cellular transformation are known as oncoviruses. Although the mechanisms of viral oncogenesis differ between viruses, all oncogenic viruses share the ability to establish persistent chronic infections with no obvious symptoms for years. During these prolonged infections, oncogenic viruses manipulate cell signaling pathways that control cell cycle progression, apoptosis, inflammation, and metabolism. Importantly, it seems that most oncoviruses depend on these changes for their persistence and amplification. Metabolic changes induced by oncoviruses share many common features with cancer metabolism. Indeed, viruses, like proliferating cancer cells, require increased biosynthetic precursors for virion production, need to balance cellular redox homeostasis, and need to ensure host cell survival in a given tissue microenvironment. Thus, like for cancer cells, viral replication and persistence of infected cells frequently depend on metabolic changes. Here, we draw parallels between metabolic changes observed in cancers or induced by oncoviruses, with a focus on pathways involved in the regulation of glucose, lipid, and amino acids. We describe whether and how oncoviruses depend on metabolic changes, with the perspective of targeting them for antiviral and onco-therapeutic approaches in the context of viral infections.

Cellular Lipids-Hijacked Victims of Viruses

Over the millions of years-long co-evolution with their hosts, viruses have evolved plenty of mechanisms through which they are able to escape cellular anti-viral defenses and utilize cellular pathways and organelles for replication and production of infectious virions. In recent years, it has become clear that lipids play an important role during viral replication. Viruses use cellular lipids in a variety of ways throughout their life cycle. They not only physically interact with cellular membranes but also alter cellular lipid metabolic pathways and lipid composition to create an optimal replication environment. This review focuses on examples of how different viruses exploit cellular lipids in different cellular compartments during their life cycles.

Metabolic dysfunction and cancer in HCV: Shared pathways and mutual interactions

HCV hijacks many host metabolic processes in an effort to aid viral replication. The resulting hepatic metabolic dysfunction underpins many of the hepatic and extrahepatic manifestations of chronic hepatitis C (CHC). However, the natural history of CHC is also substantially influenced by the host metabolic status: obesity, insulin resistance and hepatic steatosis are major determinants of CHC progression toward hepatocellular carcinoma (HCC). Direct-acting antivirals (DAAs) have transformed the treatment and natural history of CHC. While DAA therapy effectively eradicates the virus, the long-lasting overlapping metabolic disease can persist, especially in the presence of obesity, increasing the risk of liver disease progression. This review covers the mechanisms by which HCV tunes hepatic and systemic metabolism, highlighting how systemic metabolic disturbance, lipotoxicity and chronic inflammation favour disease progression and a precancerous niche. We also highlight the therapeutic implications of sustained metabolic dysfunction following sustained virologic response as well as considerations for patients who develop HCC on the background of metabolic dysfunction.

Sofosbuvir-based direct-acting antivirals and changes in cholesterol and low density lipoprotein-cholesterol

Worsened lipid profiles were observed in chronic hepatitis C (CHC) patients during direct-acting antivirals (DAAs) treatment, among which combination drugs confounded the effect of individual ingredient on lipid. Tenofovir alafenamide (TAF) also worsened lipid profiles in HIV patients. Structural similarity between sofosbuvir (SOF) and TAF prompted us to investigate rapid increase in total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in CHC patients treated with SOF-based DAAs. A retrospective study was performed to analyze 487 CHC patients receiving DAAs with SVR12. Relative risks on elevating TC and LDL-C were analyzed by logistic regression to determine SOF-based over non-SOF-based regimens. TC or LDL-C levels at baseline, week-4 and SVR12 were compared by Wilcoxon matched-pairs signed rank test. Week 4 or SVR12 to baseline ratios of serum TC or LDL-C between regimens were compared by Mann–Whitney's test. 487 patients were treated with Harvoni (SOF-based, 206 patients), Epclusa (SOF-based, 124 patients), Maviret (non-SOF-based, 122 patients), or Zepatier (non-SOF-based, 35 patients). At week 4 during drug treatment, Harvoni, Epclusa, and Maviret induced statistically significant elevation of TC and LDL-C, but Zepatier did not. SOF-based regimens had 2.72-fold higher relative risk (RR) causing 10% elevation of TC (95% CI 1.84–4.02, p < 0.001) and 2.04-fold higher RR causing 10% elevation of LDL-C (95% CI 1.39–3.01, p < 0.001) than non-SOF-based DAAs. SOF-based DAAs were associated with significantly larger amplitude of increases in TC and LDL-C than non-SOF-based DAAs during the initial 4 weeks of treatment, but the increases were not sustained to SVR12.

Integrative Transcriptomics and Proteomics Analysis Provide a Deep Insight Into Bovine Viral Diarrhea Virus-Host Interactions During BVDV Infection

Bovine viral diarrhea virus (BVDV) is the causative agent of bovine viral diarrhea-mucosal disease (BVD-MD), an important viral disease in cattle that is responsible for extensive economic losses to the cattle industry worldwide. Currently, several underlying mechanisms involved in viral replication, pathogenesis, and evading host innate immunity of BVDV remain to be elucidated, particularly during the early stage of virus infection. To further explore the mechanisms of BVDV-host interactions, the transcriptomics and proteomics profiles of BVDV-infected MDBK cells were sequenced using RNA-seq and iTRAQ techniques, respectively, and followed by an integrative analysis. Compared with mock-infected MDBK cells, a total of 665 differentially expressed genes (DEGs) (391 down-regulated, 274 up-regulated) and 725 differentially expressed proteins (DEPs) (461 down-regulated, 264 up-regulated) were identified. Among these, several DEGs and DEPs were further verified using quantitative RT-PCR and western blot. Following gene ontology (GO) annotation and KEGG enrichment analysis, we determined that these DEGs and DEPs were significantly enriched in multiple important cellular signaling pathways including NOD-like receptor, Toll-like receptor, TNF, NF-κB, MAPK, cAMP, lysosome, protein processing in endoplasmic reticulum, lipid metabolism, and apoptosis signaling pathways. Significantly, the down-regulated DEGs and DEPs were predominantly associated with apoptosis-regulated elements, inflammatory factors, and antiviral elements that were involved in innate immunity, thus, indicating that BVDV could inhibit apoptosis and the expression of host antiviral genes to facilitate viral replication. Meanwhile, up-regulated DEGs and DEPs were primarily involved in metabolism and autophagy signaling pathways, indicating that BVDV could utilize the host metabolic resources and cell autophagy to promote replication. However, the potential mechanisms BVDV-host interactions required further experimental validation. Our data provide an overview of changes in transcriptomics and proteomics profiles of BVDV-infected MDBK cells, thus, providing an important basis for further exploring the mechanisms of BVDV-host interactions.

An Antigenically Diverse, Representative Panel of Envelope Glycoproteins for Hepatitis C Virus Vaccine Development

BACKGROUND & AIMS

Development of a prophylactic hepatitis C virus (HCV) vaccine will require accurate and reproducible measurement of neutralizing breadth of vaccine-induced antibodies. Currently available HCV panels may not adequately represent the genetic and antigenic diversity of circulating HCV strains, and the lack of standardization of these panels makes it difficult to compare neutralization results obtained in different studies. Here, we describe the selection and validation of a genetically and antigenically diverse reference panel of 15 HCV pseudoparticles (HCVpps) for neutralization assays.

METHODS

We chose 75 envelope (E1E2) clones to maximize representation of natural polymorphisms observed in circulating HCV isolates, and 65 of these clones generated functional HCVpps. Neutralization sensitivity of these HCVpps varied widely. HCVpps clustered into 15 distinct groups based on patterns of relative sensitivity to 7 broadly neutralizing monoclonal antibodies. We used these data to select a final panel of 15 antigenically representative HCVpps.

RESULTS

Both the 65 and 15 HCVpp panels span 4 tiers of neutralization sensitivity, and neutralizing breadth measurements for 7 broadly neutralizing monoclonal antibodies were nearly equivalent using either panel. Differences in neutralization sensitivity between HCVpps were independent of genetic distances between E1E2 clones.

CONCLUSIONS

Neutralizing breadth of HCV antibodies should be defined using viruses spanning multiple tiers of neutralization sensitivity rather than panels selected solely for genetic diversity. We propose that this multitier reference panel could be adopted as a standard for the measurement of neutralizing antibody potency and breadth, facilitating meaningful comparisons of neutralization results from vaccine studies in different laboratories.

Hepatocellular Carcinoma in Chronic Viral Hepatitis: Where Do We Stand?

Hepatocellular carcinoma (HCC) is one of the major causes of cancer-related death. Although the burden of alcohol- and NASH-related HCC is growing, chronic viral hepatitis (HBV and HCV) remains a major cause of HCC development worldwide. The pathophysiology of viral-related HCC includes liver inflammation, oxidative stress, and deregulation of cell signaling pathways. HBV is particularly oncogenic because, contrary to HCV, integrates in the cell DNA and persists despite virological suppression by nucleotide analogues. Surveillance by six-month ultrasound is recommended in patients with cirrhosis and in "high-risk" patients with chronic HBV infection. Antiviral therapy reduces the risks of development and recurrence of HCC; however, patients with advanced chronic liver disease remain at risk of HCC despite virological suppression/cure and should therefore continue surveillance. Multiple scores have been developed in patients with chronic hepatitis B to predict the risk of HCC development and may be used to stratify individual patient's risk. In patients with HCV-related liver disease who achieve sustained virological response by direct acting antivirals, there is a strong need for markers/scores to predict long-term risk of HCC. In this review, we discuss the most recent advances regarding viral-related HCC.

Effect of sofosbuvir-based DAAs on changes in lower-density lipoprotein in HCV patients: a systematic review and meta-analysis

BACKGROUND

Previous studies reported worsened lipid profiles in patients infected with hepatitis C virus (HCV) during direct-acting antivirals (DAAs) treatment. This study aimed to investigate the effect of sofosbuvir (SOF)-based DAAs on changes in low-density lipoprotein (LDL) in HCV patients.

METHODS

A systematic review of articles published before 31 May 2021 was conducted by searching MEDLINE, Cochrane Library, EMBASE, and CINAHL Plus. Eligible studies were those comparing SOF-based DAAs and non-SOF DAAs for HCV patients and providing numerical data for changes in LDL. Risk of Bias in Non-randomized Studies- of Interventions was used for assessing risk of bias, and meta-analysis was performed for changes in LDL.

RESULTS

Six studies comprising 1248 patients were included, 848 patients treated with SOF-based DAAs and 400 patients with non-SOF DAAs vs. SOF-based DAAs group had significantly greater increases in LDL from baseline to week 4 than non-SOF DAAs group (P = 0.001). However, changes in LDL from baseline to the end of treatment (P = 0.060), to post-treatment week 12 (P = 0.263), and to post-treatment week 24 (P = 0.319) did not significantly differ between the two groups. Further comparison of SOF/ledipasvir with asunaprevir/daclatasvir revealed a similar trend in changes in LDL.

CONCLUSIONS

For HCV patients, SOF-based DAA regimens were associated with rapid and significant increases in LDL during the initial 4 weeks of treatment, and the changes did not sustain after the end of treatment. Potential mechanism might be related to the phosphoramidate side chain of SOF.

Hepatitis C virus induces oxidation and degradation of apolipoprotein B to enhance lipid accumulation and promote viral production

Hepatitis C virus (HCV) infection induces the degradation and decreases the secretion of apolipoprotein B (ApoB). Impaired production and secretion of ApoB-containing lipoprotein is associated with an increase in hepatic steatosis. Therefore, HCV infection-induced degradation of ApoB may contribute to hepatic steatosis and decreased lipoprotein secretion, but the mechanism of HCV infection-induced ApoB degradation has not been completely elucidated. In this study, we found that the ApoB level in HCV-infected cells was regulated by proteasome-associated degradation but not autophagic degradation. ApoB was degraded by the 20S proteasome in a ubiquitin-independent manner. HCV induced the oxidation of ApoB via oxidative stress, and oxidized ApoB was recognized by the PSMA5 and PSMA6 subunits of the 20S proteasome for degradation. Further study showed that ApoB was degraded at endoplasmic reticulum (ER)-associated lipid droplets (LDs) and that the retrotranslocation and degradation of ApoB required Derlin-1 but not gp78 or p97. Moreover, we found that knockdown of ApoB before infection increased the cellular lipid content and enhanced HCV assembly. Overexpression of ApoB-50 inhibited lipid accumulation and repressed viral assembly in HCV-infected cells. Our study reveals a novel mechanism of ApoB degradation and lipid accumulation during HCV infection and might suggest new therapeutic strategies for hepatic steatosis.

Hepatitis C virus (HCV) infection induces the degradation of apolipoprotein B (ApoB), which is the primary apolipoprotein in low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL). Impaired production and secretion of ApoB-containing lipoprotein is associated with an increase in hepatic steatosis. Thus, ApoB degradation might contribute to HCV infection-induced fatty liver. Here, we found that ApoB was not degraded through endoplasmic reticulum-associated degradation (ERAD) or autophagy, as reported previously. Instead, HCV infection induced ApoB oxidation through oxidative stress, and oxidatively damaged ApoB could be recognized and directly degraded by the 20S proteasome. We also found that ApoB was retrotranslocated from the endoplasmic reticulum (ER) to lipid droplets (LDs) for degradation. Through overexpression of ApoB-50, which can mediate the assembly and secretion of LDL and VLDL, we confirmed that ApoB degradation contributed to hepatocellular lipid accumulation induced by HCV infection. Additionally, expression of ApoB-50 impaired HCV production due to the observed decrease in lipid accumulation. In this study, we identified new mechanisms of ApoB degradation and HCV-induced lipid accumulation, and our findings might facilitate the development of novel therapeutic strategies for HCV infection-induced fatty liver.

HCV egress - unconventional secretion of assembled viral particles

It is believed that hepatitis C virus (HCV) particles are released through the canonical secretory route: from the endoplasmic reticulum (ER), via the Golgi, to the plasma membrane. While the Golgi is important for HCV release per se, its direct involvement in the trafficking of assembled virions has not yet been established. In fact, data from studies analyzing HCV egress are compatible with several potential pathways of HCV secretion. Here, we summarize and discuss the current knowledge related to the HCV export pathway. Apart from the prototypical anterograde transport, possible routes of HCV release include ER-to-endosomal transport, secretory autophagy, and poorly described mechanisms of unconventional protein secretion. Studying HCV egress promises to shed light on unconventional cellular trafficking and secretory routes.

Differentiated Cells in Prolonged Hypoxia Produce Highly Infectious Native-Like Hepatitis C Virus Particles

BACKGROUND AND AIMS

Standard hepatitis C virus (HCV) cell-culture models present an altered lipid metabolism and thus produce lipid-poor lipoviral particles (LVPs). These models are thereby weakly adapted to explore the complete natural viral life cycle.

APPROACH AND RESULTS

To overcome these limitations, we used an HCV cell-culture model based on both cellular differentiation and sustained hypoxia to better mimic the host-cell environment. The long-term exposure of Huh7.5 cells to DMSO and hypoxia (1% O₂ ) significantly enhanced the expression of major differentiation markers and the cellular hypoxia adaptive response by contrast with undifferentiated and normoxic (21% O₂ ) standard conditions. Because hepatocyte-like differentiation and hypoxia are key regulators of intracellular lipid metabolism, we characterized the distribution of lipid droplets (LDs) and demonstrated that experimental cells significantly accumulate larger and more numerous LDs relative to standard cell-culture conditions. An immunocapture (IC) and transmission electron microscopy (TEM) method showed that differentiated and hypoxic Huh7.5 cells produced lipoproteins significantly larger than those produced by standard Huh7.5 cell cultures. The experimental cell culture model is permissive to HCV-Japanese fulminant hepatitis (JFH1) infection and produces very-low-buoyant-density LVPs that are 6-fold more infectious than LVPs formed by standard JFH1-infected Huh7.5 cells. Finally, the IC-TEM approach and antibody-neutralization experiments revealed that LVPs were highly lipidated, had a global ultrastructure and a conformation of the envelope glycoprotein complex E1E2 close to that of the ones circulating in infected individuals.

CONCLUSIONS

This relevant HCV cell culture model thus mimics the complete native intracellular HCV life cycle and, by extension, can be proposed as a model of choice for studies of other hepatotropic viruses.

Cellular factors involved in the hepatitis C virus life cycle

The hepatitis C virus (HCV), an obligatory intracellular pathogen, highly depends on its host cells to propagate successfully. The HCV life cycle can be simply divided into several stages including viral entry, protein translation, RNA replication, viral assembly and release. Hundreds of cellular factors involved in the HCV life cycle have been identified over more than thirty years of research. Characterization of these cellular factors has provided extensive insight into HCV replication strategies. Some of these cellular factors are targets for anti-HCV therapies. In this review, we summarize the well-characterized and recently identified cellular factors functioning at each stage of the HCV life cycle.

Epigenetic Mechanisms Involved in HCV-Induced Hepatocellular Carcinoma (HCC)

Hepatocellular carcinoma (HCC), is the third leading cause of cancer-related deaths, which is largely caused by virus infection. About 80% of the virus-infected people develop a chronic infection that eventually leads to liver cirrhosis and hepatocellular carcinoma (HCC). With approximately 71 million HCV chronic infected patients worldwide, they still have a high risk of HCC in the near future. However, the mechanisms of carcinogenesis in chronic HCV infection have not been still fully understood, which involve a complex epigenetic regulation and cellular signaling pathways. Here, we summarize 18 specific gene targets and different signaling pathways involved in recent findings. With these epigenetic alterations requiring histone modifications and DNA hyper or hypo-methylation of these specific genes, the dysregulation of gene expression is also associated with different signaling pathways for the HCV life cycle and HCC. These findings provide a novel insight into a correlation between HCV infection and HCC tumorigenesis, as well as potentially preventable approaches. Hepatitis C virus (HCV) infection largely causes hepatocellular carcinoma (HCC) worldwide with 3 to 4 million newly infected cases diagnosed each year. It is urgent to explore its underlying molecular mechanisms for therapeutic treatment and biomarker discovery. However, the mechanisms of carcinogenesis in chronic HCV infection have not been still fully understood, which involve a complex epigenetic regulation and cellular signaling pathways. Here, we summarize 18 specific gene targets and different signaling pathways involved in recent findings. With these epigenetic alterations requiring histone modifications and DNA hyper or hypo-methylation of these specific genes, the dysregulation of gene expression is also associated with different signaling pathways for the HCV life cycle and HCC. These findings provide a novel insight into a correlation between HCV infection and HCC tumorigenesis, as well as potentially preventable approaches.

Therapeutic potential of phytoconstituents of edible fruits in combating emerging viral infections

Plant-derived bioactive molecules display potential antiviral activity against various viral targets including mode of viral entry and its replication in host cells. Considering the challenges and search for antiviral agents, this review provides substantiated data on chemical constituents of edible fruits with promising antiviral activity. The bioactive constituents like naringenin, mangiferin, α-mangostin, geraniin, punicalagin, and lectins of edible fruits exhibit antiviral effect by inhibiting viral replication against IFV, DENV, polio, CHIKV, Zika, HIV, HSV, HBV, HCV, and SARS-CoV. The significance of edible fruit phytochemicals to block the virulence of various deadly viruses through their inhibitory action against the entry and replication of viral genetic makeup and proteins are discussed. In view of the antiviral property of active constituents of edible fruits which can strengthen the immune system and reduce oxidative stress, they are suggested to be diet supplements to combat various viral diseases including COVID-19. PRACTICAL APPLICATIONS: Considering the increasing threat of COVID-19, it is suggested to examine the therapeutic efficacy of existing antiviral molecules of edible fruits which may provide prophylactic and adjuvant therapy with their potential antioxidant, anti-inflammatory, and immune-modulatory effects. Several active molecules like geraniin, naringenin, (2R,4R)-1,2,4-trihydroxyheptadec-16-one, betacyanins, mangiferin, punicalagin, isomangiferin, procyanidin B2, quercetin, marmelide, jacalin lectin, banana lectin, and α-mangostin isolated from various edible fruits have showed promising antiviral properties against different pathogenic viruses. Especially flavonoid compounds extracted from edible fruits possess potential antiviral activity against a wide array of viruses like HIV-1, HSV-1 and 2, HCV, INF, dengue, yellow fever, NSV, and Zika virus infection. Hence taking such fruits or edible fruits and their constituents/compounds as dietary supplements could deliver adequate plasma levels in the body to optimize the cell and tissue levels and could lead to possible benefits for the preventive measures for this pandemic COVID-19 situation.

Interdependent Impact of Lipoprotein Receptors and Lipid-Lowering Drugs on HCV Infectivity

The HCV replication cycle is tightly associated with host lipid metabolism: Lipoprotein receptors SR-B1 and LDLr promote entry of HCV, replication is associated with the formation of lipid-rich membranous organelles and infectious particle assembly highjacks the very-low-density lipoprotein (VLDL) secretory pathway. Hence, medications that interfere with the lipid metabolism of the cell, such as statins, may affect HCV infection. Here, we study the interplay between lipoprotein receptors, lipid homeostasis, and HCV infection by genetic and pharmacological interventions. We found that individual ablation of the lipoprotein receptors SR-B1 and LDLr did not drastically affect HCV entry, replication, or infection, but double lipoprotein receptor knock-outs significantly reduced HCV infection. Furthermore, we could show that this effect was neither due to altered expression of additional HCV entry factors nor caused by changes in cellular cholesterol content. Strikingly, whereas lipid-lowering drugs such as simvastatin or fenofibrate did not affect HCV entry or infection of immortalized hepatoma cells expressing SR-B1 and/or LDLr or primary human hepatocytes, ablation of these receptors rendered cells more susceptible to these drugs. Finally, we observed no significant differences between statin users and control groups with regards to HCV viral load in a cohort of HCV infected patients before and during HCV antiviral treatment. Interestingly, statin treatment, which blocks the mevalonate pathway leading to decreased cholesterol levels, was associated with mild but appreciable lower levels of liver damage markers before HCV therapy. Overall, our findings confirm the role of lipid homeostasis in HCV infection and highlight the importance of the mevalonate pathway in the HCV replication cycle.

A Review of Hepatitis B Virus and Hepatitis C Virus Immunopathogenesis

Despite the advances in therapy, hepatitis B virus (HBV) and hepatitis C virus (HCV) still represent a significant global health burden, both as major causes of cirrhosis, hepatocellular carcinoma, and death worldwide. HBV is capable of incorporating its covalently closed circular DNA into the host cell's hepatocyte genome, making it rather difficult to eradicate its chronic stage. Successful viral clearance depends on the complex interactions between the virus and host's innate and adaptive immune response. One encouraging fact on hepatitis B is the development and effective distribution of the HBV vaccine. This has significantly reduced the spread of this virus. HCV is a RNA virus with high mutagenic capacity, thus enabling it to evade the immune system and have a high rate of chronic progression. High levels of HCV heterogeneity and its mutagenic capacity have made it difficult to create an effective vaccine. The recent advent of direct acting antivirals has ushered in a new era in hepatitis C therapy. Sustained virologic response is achieved with DAAs in 85-99% of cases. However, this still leads to a large population of treatment failures, so further advances in therapy are still needed. This article reviews the immunopathogenesis of HBV and HCV, their properties contributing to host immune system avoidance, chronic disease progression, vaccine efficacy and limitations, as well as treatment options and common pitfalls of said therapy.

Hepatitis C Virus Glycan-Dependent Interactions and the Potential for Novel Preventative Strategies

Chronic hepatitis C virus (HCV) infections continue to be a major contributor to liver disease worldwide. HCV treatment has become highly effective, yet there are still no vaccines or prophylactic strategies available to prevent infection and allow effective management of the global HCV burden. Glycan-dependent interactions are crucial to many aspects of the highly complex HCV entry process, and also modulate immune evasion. This review provides an overview of the roles of viral and cellular glycans in HCV infection and highlights glycan-focused advances in the development of entry inhibitors and vaccines to effectively prevent HCV infection.

Hepatitis C Virus Uses Host Lipids to Its Own Advantage

Lipids and lipoproteins constitute indispensable components for living not only for humans. In the case of hepatitis C virus (HCV), the option of using the products of our lipid metabolism is “to be, or not to be”. On the other hand, HCV infection, which is the main cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma, exerts a profound influence on lipid and lipoprotein metabolism of the host. The consequences of this alternation are frequently observed as hypolipidemia and hepatic steatosis in chronic hepatitis C (CHC) patients. The clinical relevance of these changes reflects the fact that lipids and lipoprotein play a crucial role in all steps of the life cycle of HCV. The virus circulates in the bloodstream as a highly lipidated lipo-viral particle (LVP) that defines HCV hepatotropism. Thus, strict relationships between lipids/lipoproteins and HCV are indispensable for the mechanism of viral entry into hepatocytes, viral replication, viral particles assembly and secretion. The purpose of this review is to summarize the tricks thanks to which HCV utilizes host lipid metabolism to its own advantage.

Metabolic complications of hepatitis C virus infection

Hepatitis C virus (HCV) infection is a systemic disease that is implicated in multiple extrahepatic organ dysfunction contributing to its protean manifestations. HCV is associated with diverse extrahepatic disorders including atherosclerosis, glucose and lipid metabolic disturbances, alterations in the iron metabolic pathways, and lymphoproliferative diseases over and above the traditional liver manifestations of cirrhosis and hepatocellular carcinoma. The orchestration between HCV major proteins and the liver-muscle-adipose axis, poses a major burden on the global health of human body organs, if not adequately addressed. The close and inseparable associations between chronic HCV infection, metabolic disease, and cardiovascular disorders are specifically important considering the increasing prevalence of obesity and metabolic syndrome, and their economic burden to patients, the healthcare systems, and society. Cellular and molecular mechanisms governing the interplay of these organs and tissues in health and disease are therefore of significant interest. The coexistence of metabolic disorders and chronic hepatitis C infection also enhances the progression to liver fibrosis and hepatocellular carcinoma. The presence of metabolic disorders is believed to influence the chronicity and virulence of HCV leading to liver disease progression. This comprehensive review highlights current knowledge on the metabolic manifestations of hepatitis C and the potential pathways in which these metabolic changes can influence the natural history of the disease.

Viral use and subversion of membrane organization and trafficking

Membrane trafficking is an essential cellular process conserved across all eukaryotes, which regulates the uptake or release of macromolecules from cells, the composition of cellular membranes and organelle biogenesis. It influences numerous aspects of cellular organisation, dynamics and homeostasis, including nutrition, signalling and cell architecture. Not surprisingly, malfunction of membrane trafficking is linked to many serious genetic, metabolic and neurological disorders. It is also often hijacked during viral infection, enabling viruses to accomplish many of the main stages of their replication cycle, including entry into and egress from cells. The appropriation of membrane trafficking by viruses has been studied since the birth of cell biology and has helped elucidate how this integral cellular process functions. In this Review, we discuss some of the different strategies viruses use to manipulate and take over the membrane compartments of their hosts to promote their replication, assembly and egress.

Profiling of MicroRNA Targets Using Activity-Based Protein Profiling: Linking Enzyme Activity to MicroRNA-185 Function

MicroRNAs (miRNAs) act as cellular signal transducers through repression of protein translation. Elucidating targets using bioinformatics and traditional quantitation methods is often insufficient to uncover global miRNA function. Herein, alteration of protein function caused by miRNA-185 (miR-185), an immunometabolic miRNA, was determined using activity-based protein profiling, transcriptomics, and lipidomics. Fluorophosphonate-based activity-based protein profiling of miR-185-induced changes to human liver cells revealed that exclusively metabolic serine hydrolase enzymes were regulated in activity, some with roles in lipid and endocannabinoid metabolism. Lipidomic analysis linked enzymatic changes to levels of cellular lipid species, such as components of very-low-density lipoprotein particles. Additionally, inhibition of one miR-185 target, monoglyceride lipase, led to decreased hepatitis C virus levels in an infectious model. Overall, the approaches used here were able to identify key functional changes in serine hydrolases caused by miR-185 that are targetable pharmacologically, such that a small molecule inhibitor can recapitulate the miRNA phenotype.

Changes of Gut-Microbiota-Liver Axis in Hepatitis C Virus Infection

Simple Summary

Gut microbiota alteration is linked to many health disorders including hepatitis C virus (HCV) infection. This dysbiosis in turn impacts the coordination between the gut and the liver that is known as the gut–liver-axis. Here, we discuss the latest findings regarding the changes in gut microbiota structure and functionality post HCV infection and its treatment regimens. In addition, we underline the contribution of the microbiota alterations to HCV associated liver complications.

Abstract

The gut–liver-axis is a bidirectional coordination between the gut, including microbial residents, the gut microbiota, from one side and the liver on the other side. Any disturbance in this crosstalk may lead to a disease status that impacts the functionality of both the gut and the liver. A major cause of liver disorders is hepatitis C virus (HCV) infection that has been illustrated to be associated with gut microbiota dysbiosis at different stages of the disease progression. This dysbiosis may start a cycle of inflammation and metabolic disturbance that impacts the gut and liver health and contributes to the disease progression. This review discusses the latest literature addressing this interplay between the gut microbiota and the liver in HCV infection from both directions. Additionally, we highlight the contribution of gut microbiota to the metabolism of antivirals used in HCV treatment regimens and the impact of these medications on the microbiota composition. This review sheds light on the potential of the gut microbiota manipulation as an alternative therapeutic approach to control the liver complications post HCV infection.

Anthropometric parameters and liver histology influence lipid metabolic changes in HCV chronic hepatitis on direct-acting antiviral treatment

Background

Hepatitis C virus (HCV) infection affects lipid metabolism. We investigated the impact of direct-acting antiviral (DAA) treatment on lipid metabolism in chronic hepatitis C (CHC), with a focus on the effects of anthropometric parameters and liver histology. We also analyzed the dynamics of metabolic indexes used to estimate cardiovascular risk.

Methods

In 49 patients with CHC treated with DAAs, lipid metabolic changes, anthropometric parameters, liver histology and cardiovascular risk indexes, including triglyceride to HDL ratio (Tr/HDL), fatty liver index (FLI) and visceral adiposity index (VAI) were evaluated at baseline (BL), end of treatment (EOT) and 12 [sustained virological response (SVR) 12] and 24 (SVR24) weeks after EOT.

Results

SVR occurred in 96% of cases. Total and LDL cholesterol and ApoB levels increased significantly between BL and EOT (P<0.001, <0.001 and 0.05, respectively) and remained stable thereafter. Total and LDL cholesterol significantly increased only in patients with higher BL waist circumference (P<0.01 and 0.009), fibrosis (P=0.002 and 0.005) and steatosis (P=0.043 and 0.033, respectively). HDL cholesterol significantly rose at SVR24. However, cardiovascular risk indexes (Tr/HDL ratio, FLI and VAI) did not significantly change during DAA treatment and follow up.

Conclusions

Patients with HCV eradication after DAA treatment develop a pro-atherogenic lipid pattern, which varies according to anthropometric parameters and liver histology. However, no increase of cardiovascular risk indexes occurs in the short-term. Total and LDL cholesterol should be monitored long-term in CHC patients cured from infection.

HCV Assembly and Egress via Modifications in Host Lipid Metabolic Systems

Hepatitis C virus (HCV) proliferates by hijacking the host lipid machinery. In vitro replication systems revealed many aspects of the virus life cycle; in particular, viral utilization of host lipid metabolism during HCV proliferation. HCV interacts with lipid droplets (LDs) before starting the process of virus capsid formation at the lipid-rich endoplasmic reticulum (ER) membrane compartment. HCV buds into the ER via lipoprotein assembly and secretion. Exchangeable apolipoproteins, represented by apolipoprotein E (apoE), play pivotal roles in enhancing HCV-specific infectivity. HCV virions are likely to interact with other lipoproteins circulating in blood vessels and incorporate apolipoproteins as well as lipids. This review focuses on virus assembly and egress by briefly describing the recent advances in this area.

Lipoprotein-based drug delivery

Lipoproteins (LPs) are circulating heterogeneous nanoparticles produced by the liver and intestines. LPs play a major role in the transport of dietary and endogenous lipids to target cells through cell membrane receptors or cell surface-bound lipoprotein lipase. The stability, biocompatibility, and selective transport of LPs make them promising delivery vehicles for various therapeutic and imaging agents. This review discusses isolation, manufacturing, and drug loading techniques used for LP-based drug delivery, as well as recent applications for diagnosis and treatment of cancer, atherosclerosis, and other life-threatening diseases.

Naringenin, a flavanone with antiviral and anti-inflammatory effects: A promising treatment strategy against COVID-19

At the end of 2019, a novel flu-like coronavirus named COVID-19 (coronavirus disease 2019) was recognized by World Health Organization. No specific treatments exist for COVID-19 at this time. New evidence suggests that therapeutic options focusing on antiviral agents may alleviate COVID-19 symptoms as well as those that lead to the decrease in the inflammatory responses. Flavonoids, as phenolic compounds, have attracted considerable attention due to their various biological properties. In this review, the promising effects and possible mechanisms of action of naringenin, a citrus-derived flavonoid, against COVID-19 were discussed. We searched PubMed/Medline, Science direct, Scopus, and Google Scholar databases up to March 2020 using the definitive keywords. The evidence reviewed here indicates that naringenin might exert therapeutic effects against COVID-19 through the inhibition of COVID-19 main protease, 3-chymotrypsin-like protease (3CLpro), and reduction of angiotensin converting enzyme receptors activity. One of the other mechanisms by which naringenin might exert therapeutic effects against COVID-19 is, at least partly, by attenuating inflammatory responses. The antiviral activity of the flavanone naringenin against some viruses has also been reported. On the whole, the favorable effects of naringenin lead to a conclusion that naringenin may be a promising treatment strategy against COVID-19.

The ATGL lipase cooperates with ABHD5 to mobilize lipids for hepatitis C virus assembly

Lipid droplets are essential cellular organelles for storage of fatty acids and triglycerides. The hepatitis C virus (HCV) translocates several of its proteins onto their surface and uses them for production of infectious progeny. We recently reported that the lipid droplet-associated α/β hydrolase domain-containing protein 5 (ABHD5/CGI-58) participates in HCV assembly by mobilizing lipid droplet-associated lipids. However, ABHD5 itself has no lipase activity and it remained unclear how ABHD5 mediates lipolysis critical for HCV assembly. Here, we identify adipose triglyceride lipase (ATGL) as ABHD5 effector and new host factor involved in the hepatic lipid droplet degradation as well as in HCV and lipoprotein morphogenesis. Modulation of ATGL protein expression and lipase activity controlled lipid droplet lipolysis and virus production. ABHD4 is a paralog of ABHD5 unable to activate ATGL or support HCV assembly and lipid droplet lipolysis. Grafting ABHD5 residues critical for activation of ATGL onto ABHD4 restored the interaction between lipase and co-lipase and bestowed the pro-viral and lipolytic functions onto the engineered protein. Congruently, mutation of the predicted ABHD5 protein interface to ATGL ablated ABHD5 functions in lipid droplet lipolysis and HCV assembly. Interestingly, minor alleles of ABHD5 and ATGL associated with neutral lipid storage diseases in human, are also impaired in lipid droplet lipolysis and their pro-viral functions. Collectively, these results show that ABHD5 cooperates with ATGL to mobilize triglycerides for HCV infectious virus production. Moreover, viral manipulation of lipid droplet homeostasis via the ABHD5-ATGL axis, akin to natural genetic variation in these proteins, emerges as a possible mechanism by which chronic HCV infection causes liver steatosis.

The impact of direct-acting antiviral treatment on lipid metabolism and insulin resistance in chronic hepatitis C patients: temporary? permanent?

BACKGROUND/AIMS

In previous studies that investigated the impact of direct-acting antiviral (DAA) treatment on lipid metabolism and insulin resistance in chronic hepatitis C patients have been compared to baseline values with either end of treatment or post-treatment values. The results are inconsistent. We evaluated patients throughout the treatment and after treatment.

MATERIALS AND METHODS

121 patients were included in the study. 93 patients were treated with sofosbuvir/ledipasvir±Ribavirin (RBV), and 28 patients were treated with ombitasvir/paritaprevir/ritonavir+dasabuvir±RBV. Total cholesterol (TC), low-density lipoprotein (LDL), triglycerides (TG) and homeostatic model assessment-insulin resistance (HOMA-IR) levels were measured at the onset of treatment, after the1st month of treatment, at the end of treatment, and 6 and 12 months after the end of treatment.

RESULTS

117 patients were genotype 1. Sustained virological response was 98.4%. HOMA-IR values during treatment were significantly higher than at the beginning of treatment (p=0.0001). At 12 months there was a decrease in HOMA-IR, but this was not statistically significant (p=0.2048). TC and LDL levels were significantly increased in the first month of treatment (TC; 159±30, 180±34 mg/dl; LDL; 84±28, 100±30 mg/dl, respectively) (p<0.0001) and this increase was present during and after treatment. There was no statistically significant increase in TG (p=0120). Both treatment regimens showed similar effects on HOMA-IR, TC, and LDL.

CONCLUSION

Patients with HCV treated with DAAs drugs showed increased IR, TC, and LDL cholesterol levels during treatment. After the end of treatment, IR goes back to normal, while the elevated TC and LDL levels persist indefinitely.

18β-Glycyrrhetinic acid acts through hepatocyte nuclear factor 4 alpha to modulate lipid and carbohydrate metabolism

Hepatocyte nuclear factor 4 alpha (HNF4α) regulates the expression of essential genes involved in very-low-density lipoprotein (VLDL) homeostasis and gluconeogenesis.　18β-glycyrrhetinic acid (GA) is an active ingredient of Glycyrrhiza uralensis an herbal medicine used for treating liver aliments. In this study, we established that GA functions as a partial antagonist of HNF4α through HNF4α-driven reporter luciferase assay and co-immunoprecipitation experiments with co-activator PGC1α. By virtual docking and site-directed mutagenesis analysis, we confirmed that serine 190 and arginine 235 of HNF4α are both essential for GA to exert its antagonistic action on HNF4α. Importantly, GA suppressed the expression of HNF4α target genes such as apolipoprotein B (ApoB), microsomal triglyceride transfer protein (MTP) and phospholipase A₂ G12B (PLA2G12B) modulating hepatic VLDL secretion in mice fed on a high fat diet. In addition, GA also suppressed gluconeogenesis and ameliorated glucose intolerance via down-regulating the expression of HNF4α target genes glucose-6-phosphatase (G6pc) and phosphoenolpyruvate carboxykinase (Pepck). Furthermore, GA significantly lowered blood glucose and improved insulin resistance in db/db mice. In all, we established that GA acts as a partial HNF4α antagonist modulating lipid and carbohydrate metabolism.