Hepatitis C virus stimulates low-density lipoprotein receptor expression to facilitate viral propagation. J Virol. 2014;88:2519-2529. [PMID: 24352472 DOI: 10.1128/jvi.02727-13]

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.

PCSK9 Inhibitors and Infection-Related Adverse Events: A Pharmacovigilance Study Using the World Health Organization VigiBase

AIMS

Protein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) are novel lipid-lowering agents used in patients with cardiovascular disease. Despite reassuring safety data from pivotal trials, increasing evidence from real-world studies suggests that PCSK9i increase the risk of bacterial and viral infections. Therefore, this study aimed to identify signals of infection-related adverse events (AEs) associated with PCSK9i.

METHODS

We performed an observational pharmacovigilance study using the World Health Organization's VigiBase, recorded up to December 2022. We included individual case safety reports (ICSRs) of PCSK9 inhibitors, alirocumab and evolocumab, and compared them with those of other drugs. Infection-related ICSRs were retrieved from the Medical Dictionary for Regulatory Activities System Organ Class 'infections and infestations.'

RESULTS

Among 114,293 reports (258,099 drug-AE pairs) related to PCSK9 inhibitors, 54% included female patients, 41% included patients aged ≥65 years, and 82% included patients who received evolocumab. Additionally, beyond AEs recognized by regulatory authorities, organ infections such as influenza (reporting odds ratio [ROR] 2.89, 95% confidence interval [CI] 2.74-3.05), gastric infections (ROR 2.47, 95% CI 1.63-3.75), and kidney infections (ROR 1.36, 95% CI 1.06-1.73) were observed. Sensitivity analysis indicated a heightened risk of infection-related AEs associated with PCSK9i regardless of the specific drug type.

CONCLUSIONS

In addition to the labelled respiratory infections, six infection-related symptoms in the gastrointestinal, urinary, and renal organs were identified. Our findings support the need for systematic surveillance of infections among PCSK9i users.

Primary hypocholesterolemia is associated with an increased risk of hepatic complications in the general population

BACKGROUND & AIMS

Beyond cardiovascular disease protection, the health consequences of very low concentrations of low-density lipoprotein-cholesterol (LDL-C) remain a matter of debate. In primary hypobetalipoproteinemia (HBL), liver steatosis and cirrhosis have occasionally been reported. Here, we aimed to investigate the association between HBL and the risk of hepatic complications (cirrhosis complications and/or primary liver cancer) in the general population.

METHODS

A cohort study was conducted in the French population-based cohort CONSTANCES. Participants with primary HBL (LDL-C <5th percentile for age and sex, [HBL]) were compared with those with normal LDL-C concentrations (40th-60th percentile, [Control]). Participants on lipid-lowering therapies were excluded. For hepatic complications, follow-up events were compared by calculating the incidence density ratio (IDR). The same analyses were replicated in the UK Biobank (UKBB) cohort.

RESULTS

In the CONSTANCES and UKBB cohorts, 34,653 and 94,666 patients were analyzed, with median ages of 45 and 56 years, mean LDL-C concentrations (HBL vs. control) of 71 vs. 128 mg/dl and 86 vs. 142 mg/dl, and mean follow-up durations of 5.0 and 11.5 years, respectively. The HBL group presented a higher incidence of hepatic complications than the control group: 0.32/ vs. 0.07/1,000 person-years (IDR = 4.50, 95% CI 1.91-10.6) in CONSTANCES, and 0.69/ vs. 0.21/1,000 person-years (IDR = 3.27, 95% CI 2.63-4.06) in the UKBB. This risk proved to be independent of classic risk factors for liver disease (obesity, alcohol consumption, diabetes, viral hepatitis), including in a 5-year landmark analysis excluding early events. Sensitivity analyses based on apoliprotein-B levels (instead of LDL-C levels) or genetically defined HBL showed similar results.

CONCLUSIONS

HBL is associated with a markedly increased risk of hepatic complications. HBL must be considered as a substantial independent risk factor for liver diseases which justifies specific prevention and screening.

IMPACT AND IMPLICATIONS

Hypobetalipoproteinemia (HBL) is a lipid disorder characterized by permanent, inherited low levels (below the 5th percentile) of low-density lipoprotein-cholesterol. While HBL is associated with a lower risk of cardiovascular events, some studies suggest that it may be associated with a potential risk of hepatic steatosis and hepatic complications. Here, we studied the association between HBL and hepatic complications (defined as cirrhosis complications and/or primary liver cancer) in two populations of several hundred thousand people, both in France (CONSTANCES cohort) and the United Kingdom (UKBB). The results show that HBL is associated with a significant and independent excess risk of hepatic complications, including primary liver cancer. Thus, in people with HBL, the value of regular liver monitoring must be studied.

Personalized medicine and nutrition in hepatology for preventing chronic liver disease in Mexico

Chronic liver disease is a global health issue. Patients with chronic liver disease require a fresh approach that focuses on the genetic and environmental factors that contribute to disease initiation and progression. Emerging knowledge in the fields of Genomic Medicine and Genomic Nutrition demonstrates differences between countries in terms of genetics and lifestyle risk factors such as diet, physical activity, and mental health in chronic liver disease, which serves as the foundation for the implementation of Personalized Medicine and Nutrition (PerMed-Nut) strategies. Most of the world's populations have descended from various ethnic groupings. Mexico's population has a tripartite ancestral background, consisting of Amerindian, European, and African lineages, which is common across Latin America's regional countries. The purpose of this review is to discuss the genetic and environmental components that could be incorporated into a PerMed-Nut model for metabolic-associated liver disease, viral hepatitis B and C, and hepatocellular carcinoma in Mexico. Additionally, the implementation of the PerMed-Nut approach will require updated medicine and nutrition education curricula. Training and equipping future health professionals and researchers with new clinical and investigative abilities focused on preventing liver illnesses in the field of genomic hepatology globally is a vision that clinicians and nutritionists should be concerned about.

Hepatitis C virus E1 recruits high-density lipoprotein to support infectivity and evade antibody recognition

Hepatitis C virus (HCV) is a member of the Flaviviridae family; however, unlike other family members, the HCV virion has an unusually high lipid content. HCV has two envelope glycoproteins, E1 and E2. E2 contributes to receptor binding, cell membrane attachment, and immune evasion. In contrast, the functions of E1 are poorly characterized due, in part, to challenges in producing the protein. This manuscript describes the expression and purification of a soluble E1 ectodomain (eE1) that is recognized by conformational, human monoclonal antibodies. eE1 forms a complex with apolipoproteins AI and AII, cholesterol, and phospholipids by recruiting high-density lipoprotein (HDL) from the extracellular media. We show that HDL binding is a function specific to eE1 and HDL hinders recognition of E1 by a neutralizing monoclonal antibody. Either low-density lipoprotein or HDL increases the production and infectivity of cell culture-produced HCV, but E1 preferentially selects HDL, influencing both viral life cycle and antibody evasion.IMPORTANCEHepatitis C virus (HCV) infection is a significant burden on human health, but vaccine candidates have yet to provide broad protection against this infection. We have developed a method to produce high quantities of soluble E1 or E2, the viral proteins located on the surface of HCV. HCV has an unusually high lipid content due to the recruitment of apolipoproteins. We found that E1 (and not E2) preferentially recruits host high-density lipoprotein (HDL) extracellularly. This recruitment of HDL by E1 prevents binding of E1 by a neutralizing antibody and furthermore prevents antibody-mediated neutralization of the virus. By comparison, low-density lipoprotein does not protect the virus from antibody-mediated neutralization. Our findings provide mechanistic insight into apolipoprotein recruitment, which may be critical for vaccine development.

Pseudorabies virus upregulates low-density lipoprotein receptors to facilitate viral entry

Pseudorabies virus (PRV) is the causative agent of Aujeszky's disease in pigs. The low-density lipoprotein receptor (LDLR) is a transcriptional target of the sterol-regulatory element-binding proteins (SREBPs) and participates in the uptake of LDL-derived cholesterol. However, the involvement of LDLR in PRV infection has not been well characterized. We observed an increased expression level of LDLR mRNA in PRV-infected 3D4/21, PK-15, HeLa, RAW264.7, and L929 cells. The LDLR protein level was also upregulated by PRV infection in PK-15 cells and in murine lung and brain. The treatment of cells with the SREBP inhibitor, fatostatin, or with SREBP2-specific small interfering RNA prevented the PRV-induced upregulation of LDLR expression as well as viral protein expression and progeny virus production. This suggested that PRV activated SREBPs to induce LDLR expression. Furthermore, interference in LDLR expression affected PRV proliferation, while LDLR overexpression promoted it. This indicated that LDLR was involved in PRV infection. The study also demonstrated that LDLR participated in PRV invasions. The overexpression of LDLR or inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9), which binds to LDLR and targets it for lysosomal degradation, significantly enhanced PRV attachment and entry. Mechanistically, LDLR interacted with PRV on the plasma membrane, and pretreatment of cells with LDLR antibodies was able to neutralize viral entry. An in vivo study indicated that the treatment of mice with the PCSK9 inhibitor SBC-115076 promoted PRV proliferation. The data from the study indicate that PRV hijacks LDLR for viral entry through the activation of SREBPs.IMPORTANCEPseudorabies virus (PRV) is a herpesvirus that primarily manifests as fever, pruritus, and encephalomyelitis in various domestic and wild animals. Owing to its lifelong latent infection characteristics, PRV outbreaks have led to significant financial setbacks in the global pig industry. There is evidence that PRV variant strains can infect humans, thereby crossing the species barrier. Therefore, gaining deeper insights into PRV pathogenesis and developing updated strategies to contain its spread are critical. This study posits that the low-density lipoprotein receptor (LDLR) could be a co-receptor for PRV infection. Hence, strategies targeting LDLR may provide a promising avenue for the development of effective PRV vaccines and therapeutic interventions.

Liver X Receptor-Inducible Host E3 Ligase IDOL Targets a Human Cytomegalovirus Reactivation Determinant

Liver X receptor (LXR) signaling broadly restricts virus replication; however, the mechanisms of restriction are poorly defined. Here, we demonstrate that the cellular E3 ligase LXR-inducible degrader of low-density lipoprotein receptor (IDOL) targets the human cytomegalovirus (HMCV) UL136p33 protein for turnover. UL136 encodes multiple proteins that differentially impact latency and reactivation. UL136p33 is a determinant of reactivation. UL136p33 is targeted for rapid turnover by the proteasome, and its stabilization by mutation of lysine residues to arginine results in a failure to quiet replication for latency. We show that IDOL targets UL136p33 for turnover but not the stabilized variant. IDOL is highly expressed in undifferentiated hematopoietic cells where HCMV establishes latency but is sharply downregulated upon differentiation, a stimulus for reactivation. We hypothesize that IDOL maintains low levels of UL136p33 for the establishment of latency. Consistent with this hypothesis, knockdown of IDOL impacts viral gene expression in wild-type (WT) HCMV infection but not in infection where UL136p33 has been stabilized. Furthermore, the induction of LXR signaling restricts WT HCMV reactivation from latency but does not affect the replication of a recombinant virus expressing a stabilized variant of UL136p33. This work establishes the UL136p33-IDOL interaction as a key regulator of the bistable switch between latency and reactivation. It further suggests a model whereby a key viral determinant of HCMV reactivation is regulated by a host E3 ligase and acts as a sensor at the tipping point between the decision to maintain the latent state or exit latency for reactivation. IMPORTANCE Herpesviruses establish lifelong latent infections, which pose an important risk for disease particularly in the immunocompromised. Our work is focused on the betaherpesvirus human cytomegalovirus (HCMV) that latently infects the majority of the population worldwide. Defining the mechanisms by which HCMV establishes latency or reactivates from latency is important for controlling viral disease. Here, we demonstrate that the cellular inducible degrader of low-density lipoprotein receptor (IDOL) targets a HCMV determinant of reactivation for degradation. The instability of this determinant is important for the establishment of latency. This work defines a pivotal virus-host interaction that allows HCMV to sense changes in host biology to navigate decisions to establish latency or to replicate.

Specialized metabolites from plants as a source of new multi-target antiviral drugs: a systematic review

Viral infections have always been the main global health challenge, as several potentially lethal viruses, including the hepatitis virus, herpes virus, and influenza virus, have affected human health for decades. Unfortunately, most licensed antiviral drugs are characterized by many adverse reactions and, in the long-term therapy, also develop viral resistance; for these reasons, researchers have focused their attention on investigating potential antiviral molecules from plants. Natural resources indeed offer a variety of specialized therapeutic metabolites that have been demonstrated to inhibit viral entry into the host cells and replication through the regulation of viral absorption, cell receptor binding, and competition for the activation of intracellular signaling pathways. Many active phytochemicals, including flavonoids, lignans, terpenoids, coumarins, saponins, alkaloids, etc., have been identified as potential candidates for preventing and treating viral infections. Using a systematic approach, this review summarises the knowledge obtained to date on the in vivo antiviral activity of specialized metabolites extracted from plant matrices by focusing on their mechanism of action.

Cholesterol Biosynthesis Modulates CSFV Replication

Classical swine fever (CSF) caused by the classical swine fever virus (CSFV) has resulted in severe losses to the pig industry worldwide. It has been proposed that lipid synthesis is essential for viral replication, and lipids are involved in viral protein maturation and envelope production. However, the specific crosstalk between CSFV and host cell lipid metabolism is still unknown. In this study, we found that CSFV infection increased intracellular cholesterol levels in PK-15 cells. Further analysis demonstrated that CSFV infection upregulated PCSK9 expression to block the uptake of exogenous cholesterol by LDLR and enhanced the cholesterol biosynthesis pathway, which disrupted the type I IFN response in PK-15 cells. Our findings provide new insight into the mechanisms underpinning the pathogenesis of CSFV and hint at methods for controlling the disease.

Molecular cloning, characterization, and functional analysis of the uncharacterized C11orf96 gene

Background

The mammalian genome encodes millions of proteins. Although many proteins have been discovered and identified, a large part of proteins encoded by genes are yet to be discovered or fully characterized. In the present study, we successfully identified a host protein C11orf96 that was significantly upregulated after viral infection.

Results

First, we successfully cloned the coding sequence (CDS) region of the cat, human, and mouse C11orf96 gene. The CDS region of the C11orf96 gene is 372 bp long, encodes 124 amino acids, and is relatively conserved in different mammals. From bioinformatics analysis, we found that C11orf96 is rich in Ser and has multiple predicted phosphorylation sites. Moreover, protein interaction prediction analysis revealed that the protein is associated with several transmembrane family proteins and zinc finger proteins. Subsequently, we found that C11orf96 is strictly distributed in the cytoplasm. According to the tissue distribution characteristics, C11orf96 is distributed in all tissues and organs, with the highest expression levels in the kidney. These results indicate that C11orf96 may play a specific biological role in the kidney.

Conclusions

Summarizing, these data lay the foundation for studying the biological functions of C11orf96 and for exploring its role in viral replication.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03224-5.

Insight into the Evolving Role of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is the last discovered member of the family of proprotein convertases (PCs), mainly synthetized in hepatic cells. This serine protease plays a pivotal role in the reduction of the number of low-density lipoprotein receptors (LDLRs) on the surface of hepatocytes, which leads to an increase in the level of cholesterol in the blood. This mechanism and the fact that gain of function (GOF) mutations in PCSK9 are responsible for causing familial hypercholesterolemia whereas loss-of-function (LOF) mutations are associated with hypocholesterolemia, prompted the invention of drugs that block PCSK9 action. The high efficiency of PCSK9 inhibitors (e.g., alirocumab, evolocumab) in decreasing cardiovascular risk, pleiotropic effects of other lipid-lowering drugs (e.g., statins) and the multifunctional character of other proprotein convertases, were the cause for proceeding studies on functions of PCSK9 beyond cholesterol metabolism. In this article, we summarize the current knowledge on the roles that PCSK9 plays in different tissues and perspectives for its clinical use.

Emerging Insights on the Diverse Roles of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) in Chronic Liver Diseases: Cholesterol Metabolism and Beyond

Chronic liver diseases are commonly associated with dysregulated cholesterol metabolism. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease of the proprotein convertase family that is mainly synthetized and secreted by the liver, and represents one of the key regulators of circulating low-density lipoprotein (LDL) cholesterol levels. Its ability to bind and induce LDL-receptor degradation, in particular in the liver, increases circulating LDL-cholesterol levels in the blood. Hence, inhibition of PCSK9 has become a very potent tool for the treatment of hypercholesterolemia. Besides PCSK9 limiting entry of LDL-derived cholesterol, affecting multiple cholesterol-related functions in cells, more recent studies have associated PCSK9 with various other cellular processes, including inflammation, fatty acid metabolism, cancerogenesis and visceral adiposity. It is increasingly becoming evident that additional roles for PCSK9 beyond cholesterol homeostasis are crucial for liver physiology in health and disease, often contributing to pathophysiology. This review will summarize studies analyzing circulating and hepatic PCSK9 levels in patients with chronic liver diseases. The factors affecting PCSK9 levels in the circulation and in hepatocytes, clinically relevant studies and the pathophysiological role of PCSK9 in chronic liver injury are discussed.

Long-term surveillance of liver histological changes in chronic hepatitis C patients completing pegylated interferon-α plus ribavirin therapy: an observational cohort study

BACKGROUND

For chronic hepatitis C (CHC) patients completing pegylated interferon (PegIFN)-α/ribavirin therapy, long-term liver histological changes remain largely unexplored.

METHODS

This observational cohort study included 85 CHC patients completing PegIFN-α/ribavirin therapy with liver biopsies performed at baseline and the end of surveillance (EOS). Median years between paired biopsies were 6.75 (interquartile range: 5.63-7.54).

RESULTS

In patients with baseline METAVIR fibrosis stages (F) <4 (able to undergo fibrosis progression; n = 77), cases achieving sustained virological response (SVR) (n = 52) had a significantly lower rate of fibrosis progression than non-SVR cases (n = 25) (3.8% versus 24.0%, p = 0.012). Among the entire cohort (n = 85), the rate of activity response [METAVIR activity grades (A) decreasing or maintaining at A0] in SVR cases (n = 59) was significantly higher than that in non-SVR cases (n = 26) (94.9% versus 65.4%, p = 0.001). For SVR cases among the entire cohort, independent predictors of fibrosis clearance included baseline F <2 [odds ratio (OR) = 7.877, p = 0.042] and aspartate transaminase (AST) levels declining by >70% at EOS compared with baseline (OR = 9.013, p = 0.038). For non-SVR cases among the entire cohort, baseline AST levels >80 U/l and glucose levels ⩽ 105 mg/dl independently predicted significant fibrosis (F2/F3/F4) at EOS (OR = 12.558, p = 0.049) and activity response (OR = 17.741, p = 0.047), respectively.

CONCLUSIONS

Among CHC patients completing PegIFN-α/ribavirin therapy, SVR lowers the risk of liver histological progression but does not guarantee fibrosis clearance. For SVR cases, those with baseline F ⩾ 2 or without significantly declined follow-up AST levels should be specifically monitored. As for non-SVR cases, those with a higher baseline AST or glucose level should preferentially receive retreatment.

Strong relationship between cholesterol, low-density lipoprotein receptor, Na+/H+ exchanger, and SARS-COV-2: this association may be the cause of death in the patient with COVID-19

Lipids have a wide variety and vital functions. Lipids play roles in energy metabolism, intracellular and extracellular signal traffic, and transport of fat-soluble vitamins. Also, they form the structure of the cell membrane. SARS-CoV-2 interacts with lipids since its genetic material contains lipid-enveloped ribonucleic acid (RNA). Previous studies have shown that total cholesterol, high-density lipoprotein, and low-density lipoprotein (LDL) levels are lower in patients with severe novel coronavirus disease 2019 (COVID-19) compared to patients with non-severe COVID-19.Na+/H+ Exchanger (NHE) is an important antiport that keeps the intracellular pH value within physiological limits. When the intracellular pH falls, NHE is activated and pumps H+ ions outward. However, prolonged NHE activation causes cell damage and atherosclerosis. Prolonged NHE activation may increase susceptibility to SARS-CoV-2 infection and severity of COVID-19.In COVID-19, increased angiotensin II (Ang II) due to angiotensin-converting enzyme-2 (ACE2) dysfunction stimulates NHE. Lipids are in close association with the NHE pump. Prolonged NHE activity increases the influx of H+ ions and free fatty acid (FFA) inward. Ang II also causes increased low-density lipoprotein receptor (LDLR) levels by inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9). Thus, intracellular atheroma plaque formation is accelerated.Besides, SARS-CoV-2 may replicate more rapidly as intracellular cholesterol increases. SARS-CoV-2 swiftly infects the cell whose intracellular pH decreases with NHE activation and FFA movement. Novel treatment regimens based on NHE and lipids should be explored for the treatment of COVID-19.

Strong relationship between cholesterol, low-density lipoprotein receptor, Na+/H+ exchanger, and SARS-COV-2: this association may be the cause of death in the patient with COVID-19

Lipids have a wide variety and vital functions. Lipids play roles in energy metabolism, intracellular and extracellular signal traffic, and transport of fat-soluble vitamins. Also, they form the structure of the cell membrane. SARS-CoV-2 interacts with lipids since its genetic material contains lipid-enveloped ribonucleic acid (RNA). Previous studies have shown that total cholesterol, high-density lipoprotein, and low-density lipoprotein (LDL) levels are lower in patients with severe novel coronavirus disease 2019 (COVID-19) compared to patients with non-severe COVID-19.Na⁺/H⁺ Exchanger (NHE) is an important antiport that keeps the intracellular pH value within physiological limits. When the intracellular pH falls, NHE is activated and pumps H⁺ ions outward. However, prolonged NHE activation causes cell damage and atherosclerosis. Prolonged NHE activation may increase susceptibility to SARS-CoV-2 infection and severity of COVID-19.In COVID-19, increased angiotensin II (Ang II) due to angiotensin-converting enzyme-2 (ACE2) dysfunction stimulates NHE. Lipids are in close association with the NHE pump. Prolonged NHE activity increases the influx of H⁺ ions and free fatty acid (FFA) inward. Ang II also causes increased low-density lipoprotein receptor (LDLR) levels by inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9). Thus, intracellular atheroma plaque formation is accelerated.Besides, SARS-CoV-2 may replicate more rapidly as intracellular cholesterol increases. SARS-CoV-2 swiftly infects the cell whose intracellular pH decreases with NHE activation and FFA movement. Novel treatment regimens based on NHE and lipids should be explored for the treatment of COVID-19.

The Impact of Steatosis on Chronic Hepatitis C Progression and Response to Antiviral Treatments

Metabolic derangement is characteristic in patients with hepatitis C virus (HCV) infection. Aside from established liver injury, various extrahepatic metabolic disorders impact the natural history of the disease, clinical outcomes, and the efficacy of antiviral therapy. The presence of steatosis, recently redefined as metabolic-associated fatty liver disease (MAFLD), is a common feature in HCV-infected patients, induced by host and/or viral factors. Most chronic HCV-infected (CHC) patients have mild steatosis within the periportal region of the liver with an estimated prevalence of 40% to 86%. Indeed, this is higher than the 19% to 50% prevalence observed in patients with other chronic liver diseases such as chronic hepatitis B (CHB). The histological manifestations of HCV infection are frequently observed in genotype 3 (G-3), where relative to other genotypes, the prevalence and severity of steatosis is also increased. Steatosis may independently influence the treatment efficacy of either interferon-based or interferon-free antiviral regimens. This review aimed to provide updated evidence of the prevalence and risk factors behind HCV-associated steatosis, as well as explore the impact of steatosis on HCV-related outcomes.

Metabolic comorbidities and male sex influence steatosis in chronic hepatitis C after viral eradication by direct-acting antiviral therapy (DAAs): Evaluation by the controlled attenuation parameter (CAP)

BACKGROUND

Chronic hepatitis C (CHC) is associated with hepatic steatosis, related to both a direct viral action and metabolic features. Vice-versa data on hepatic steatosis after viral eradication by direct-acting antiviral agents (DAA) are undefined although the presence of metabolic alterations could strongly influence the occurrence of steatosis as in NAFLD. The controlled attenuation parameter (CAP) (FibroscanⓇ) allows the qualitative and quantitative evaluation of fatty liver.

AIM

to evaluate in patients with CHC whether hepatic steatosis diagnosed by CAP modifies after DAAs-induced sustained virologic response (SVR).

METHODS

Data were collected the day of DAAs therapy starting and six months after SVR. CAP ≥ 248 dB/m defined the presence of steatosis.

RESULTS

794 CHC SVR patients referring to 2 Italian Units were enrolled. Mean age was 64 ± 16 ys, 50% males, BMI 25.4 ± 4 kg/m², genotype type-1 in 73%, type-3 in 8%. Prevalence of hepatic steatosis at baseline was 32% by US and 46% by CAP. De novo steatosis developed in 125 (29%), resolution in 122 (30%). At multivariate analysis de novo steatosis was independently associated with male sex (OR 1.7, CI 95% 1.09-2.67; p = 0.02) and baseline BMI (for unit increase OR 1.19, CI 95%1.11-1.29; p < 0.001). Baseline BMI (for unit increase OR 0.47, CI 95% 0.25-0.89; p = 0.02) and triglycerides (for unit increase OR 0.93, CI 95% 0.87-0.99; p = 0.03) prevented steatosis resolution after therapy.

CONCLUSIONS

after SVR de novo steatosis and resolution of baseline steatosis are closely related to the presence of metabolic comorbidities.

Adherence to a Fish-Rich Dietary Pattern Is Associated with Chronic Hepatitis C Patients Showing Low Viral Load: Implications for Nutritional Management

Hepatitis C virus (HCV) infection is influenced by genetic (e.g., APOE polymorphisms) and environmental factors between the virus and the host. HCV modulates the host’s lipid metabolism but dietary components influence lipids and in vitro HCV RNA replication. Few data exist on the role of dietary features or patterns (DPs) in HCV infection. Herein, we aimed to evaluate the nutritional profiles of chronic HCV (CHC) and spontaneous clearance (SC) Mexican patients in the context of APOE alleles and their correlation with HCV-related variables. The fibrosis-related APOEε3 allele prevailed in CHC and SC patients, who had four DPs (“meat and soft drinks”, DP1; “processed animal and fried foods”, DP2; “Mexican-healthy”, DP3; and “fish-rich”, DP4). In CHC subjects, polyunsaturated fatty acid intake (PUFA ≥ 4.9%) was negatively associated, and fiber intake (≥21.5 g/day) was positively associated with a high viral load (p < 0.036). High adherence to fish-rich DP4 was associated with a higher frequency of CHC individuals consuming PUFA ≥ 4.9% (p = 0.004) and low viral load (p = 0.036), but a lower frequency of CHC individuals consuming fiber ≥21.5 g/day (p = 0.038). In SC and CHC individuals, modifying unhealthy DPs and targeting HCV-interacting nutrients, respectively, could be part of a nutritional management strategy to prevent further liver damage.

Low-Density Lipoprotein Receptor Suppresses the Endogenous Cholesterol Synthesis Pathway To Oppose Gammaherpesvirus Replication in Primary Macrophages

Gammaherpesviruses are ubiquitous pathogens that establish lifelong infections in >95% of adults worldwide and are associated with several cancers. We have shown that endogenous cholesterol synthesis supports gammaherpesvirus replication. However, the role of exogenous cholesterol exchange and signaling during infection remains poorly understood. Extracellular cholesterol is carried in the serum by several lipoproteins, including low-density lipoproteins (LDL). The LDL receptor (LDL-R) mediates the endocytosis of these cholesterol-rich LDL particles into the cell, thereby supplying the cell with cholesterol. We found that LDL-R expression attenuates gammaherpesvirus replication during the early stages of the replication cycle, as evident by increased viral gene expression in LDL-R^-/- primary macrophages. This was not observed in primary fibroblasts, indicating that the antiviral effects of LDL-R are cell type specific. Increased viral gene expression in LDL-R^-/- primary macrophages was due to increased activity of the endogenous cholesterol synthesis pathway. Intriguingly, despite type I interferon-driven increase in LDL-R mRNA levels in infected macrophages, protein levels of LDL-R continually decreased over the single cycle of viral replication. Thus, our study has uncovered an intriguing tug of war between the LDL-R-driven antiviral effect on cholesterol metabolism and the viral targeting of the LDL-R protein. IMPORTANCE LDL-R is a cell surface receptor that mediates the endocytosis of cholesterol-rich low-density lipoproteins, allowing cells to acquire cholesterol exogenously. Several RNA viruses usurp LDL-R function to facilitate replication; however, the role of LDL-R in DNA virus infection remains unknown. Gammaherpesviruses are double-stranded DNA viruses that are associated with several cancers. Here, we show that LDL-R attenuates gammaherpesvirus replication in primary macrophages by decreasing endogenous cholesterol synthesis activity, a pathway known to support gammaherpesvirus replication. In response, LDL-R protein levels are decreased in infected cells to mitigate the antiviral effects, revealing an intriguing tug of war between the virus and the host.

Serum lipid profile in HCV patients treated with direct-acting antivirals: a systematic review and meta-analysis

Although direct-acting antivirals are very effective and safe drugs, several authors have reported the alteration of lipid profile during and after anti-HCV therapy suggesting a potential impact on the risk of cardiovascular events. We performed a systematic review and meta-analysis of observational studies to investigate the magnitude and temporal trend of lipid profile changes in DAA treated patients. All selected studies included data on lipid profile before starting therapy and at least one follow-up assessment during or after antiviral treatment. We identified 14 studies (N = 1537 patients) after removing duplicates. Pooled data showed an increase in total cholesterol 4 weeks after starting therapy (+ 15.86 mg/dl; 95% CI + 9.68 to 22.05; p < 0.001) and 12 weeks after treatment completion (+ 17.05 mg/dl; 95% CI + 11.24 to 22.85; p < 0.001). LDL trend was similar to the total cholesterol change in overall analysis. A mean increase in HDL-cholesterol of 3.36 mg/dl (95% CI + 0.92 to 5.79; p = 0.07) was observed after 12 weeks of treatment, whereas at SVR24 HDL difference was + 4.34 mg/dl (95% CI + 1.40 to 7.28; p = 0.004).Triglycerides did not show significant changes during treatment and after treatment completion. DAAs induce mild lipid changes in chronic hepatitis C patients treated with DAAs, which may persist after treatment completion.

Quantitative and qualitative lipid improvement with chronic hepatitis C virus eradication using direct-acting antivirals

AIM

Direct-acting antivirals have revolutionized hepatitis C virus (HCV) therapy by providing a high sustained virological response (SVR) rate and subsequent favorable lipid increases. Proprotein convertase subtilisin-kexin like-9 (PCSK9) plays an important role in regulating quantitative lipid levels. This study examined the interactions between quantitative PCSK9 and lipid changes, as well as qualitative lipid changes in terms of lectin-like oxidized low-density lipoprotein (LDL) receptor-1 ligand containing apolipoprotein B (LAB) and high-density lipoprotein (HDL) cholesterol uptake capacity (HDL-CUC).

METHODS

Patients with chronic HCV infection (N = 231) who achieved an SVR by direct-acting antivirals without lipid-lowering therapy were included for comparisons of PCSK9, LAB, HDL-CUC, and other clinical indices between pretreatment and SVR12 time points.

RESULTS

LDL (LDL) cholesterol and HDL cholesterol levels were quantitatively increased at SVR12, along with higher PCSK9 (all p < 0.0001). PCSK9 was significantly correlated with LDL cholesterol (r = 0.244, p = 0.0003) and apolipoprotein B (r = 0.222, p = 0.0009) at SVR12. Regarding qualitative LDL changes, LAB was significantly decreased and LAB/LDL cholesterol and LAB/apolipoprotein B proportions were improved at SVR12 (all p < 0.0001). In terms of qualitative HDL changes, HDL-CUC was significantly ameliorated, along with HDL-CUC/HDL cholesterol, HDL-CUC/ apolipoprotein A1, and HDL-CUC/ apolipoprotein A2 at SVR12 (all p < 0.0001).

CONCLUSIONS

HCV eradication by direct-acting antivirals may produce quantitative lipid profile changes, along with PCSK9 production recovery in addition to qualitative lipid improvement, which possibly confers the additional secondary benefits of atherosclerosis improvement and cardiovascular disease event reduction.

How Do Enveloped Viruses Exploit the Secretory Proprotein Convertases to Regulate Infectivity and Spread?

Inhibition of the binding of enveloped viruses surface glycoproteins to host cell receptor(s) is a major target of vaccines and constitutes an efficient strategy to block viral entry and infection of various host cells and tissues. Cellular entry usually requires the fusion of the viral envelope with host plasma membranes. Such entry mechanism is often preceded by “priming” and/or “activation” steps requiring limited proteolysis of the viral surface glycoprotein to expose a fusogenic domain for efficient membrane juxtapositions. The 9-membered family of Proprotein Convertases related to Subtilisin/Kexin (PCSK) serine proteases (PC1, PC2, Furin, PC4, PC5, PACE4, PC7, SKI-1/S1P, and PCSK9) participate in post-translational cleavages and/or regulation of multiple secretory proteins. The type-I membrane-bound Furin and SKI-1/S1P are the major convertases responsible for the processing of surface glycoproteins of enveloped viruses. Stefan Kunz has considerably contributed to define the role of SKI-1/S1P in the activation of arenaviruses causing hemorrhagic fever. Furin was recently implicated in the activation of the spike S-protein of SARS-CoV-2 and Furin-inhibitors are being tested as antivirals in COVID-19. Other members of the PCSK-family are also implicated in some viral infections, such as PCSK9 in Dengue. Herein, we summarize the various functions of the PCSKs and present arguments whereby their inhibition could represent a powerful arsenal to limit viral infections causing the present and future pandemics.

Evidence of Transcriptional Shutoff by Pathogenic Viral Haemorrhagic Septicaemia Virus in Rainbow Trout

The basis of pathogenicity of viral haemorrhagic septicaemia virus (VHSV) was analysed in the transcriptome of a rainbow trout cell line inoculated with pathogenic and non-pathogenic VHSV isolates. Although both VHSV isolates showed similar viral replication patterns, the number of differentially expressed genes was 42-fold higher in cells inoculated with the non-pathogenic VHSV at 3 h post inoculation (hpi). Infection with the non-pathogenic isolate resulted in Gene Ontologies (GO) enrichment of terms such as immune response, cytokine-mediated signalling pathway, regulation of translational initiation, unfolded protein binding, and protein folding, and induced an over-representation of the p53, PPAR, and TGF-β signalling pathways. Inoculation with the pathogenic isolate resulted in the GO enrichment of terms related to lipid metabolism and the salmonella infection KEGG pathway involved in the rearrangement of the cytoskeleton. Antiviral response was evident at 12hpi in cells infected with the pathogenic isolate. Overall, the data showed a delay in the response of genes involved in immune responses and viral sensing in cells inoculated with the pathogenic isolate and suggest transcriptional shutoff and immune avoidance as a critical mechanism of pathogenicity in VHSV. These pathways offer opportunities to further understand and manage VHSV pathogenicity in rainbow trout.

The consequences of PCSK9 inhibition in selected tissues

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of nine members of the proprotein convertase family. These serine proteases play a pivotal role in the post-translational modification of proteins and the activation of hormones, enzymes, transcription factors and growth factors. As a result, they participate in many physiological processes like embryogenesis, activity of central nervous system and lipid metabolism. Scientific studies show that the family of convertases is also involved in the pathogenesis of viral and bacterial infections, osteoporosis, hyperglycaemia, cardiovascular diseases, neurodegenerative disorders and cancer. The inhibition of PCSK9 by two currently approved for use monoclonal antibodies (alirocumab, evolocumab) slows down the degradation of low-density lipoprotein cholesterol receptors (LDLRs). This leads to increased density of LDLRs on the surface of hepatocytes, resulting in decreased level of low-density lipoprotein cholesterol (LDL-C) in the bloodstream, which is connected with the reduction of cardiovascular risk. PCSK9 inhibitors (PCSK9i) were created for the patients who could not achieve appropriate level of LDL-C using current statin and ezetimibe therapy. It seems that high therapeutic efficacy of PCSK9i will make them more common in the clinical use. The pleiotropic effects of previously mentioned lipid-lowering therapies were the reasons for literature review of possible positive and negative effects of PCSK9 inhibition beyond cholesterol metabolism.

Effect of directly acting antivirals for hepatitis C virus infection on proprotein convertase subtilisin/kexin type 9 level

BACKGROUND AND AIMS

Eradication of the hepatitis C virus (HCV) may affect proprotein convertase subtilisin/kexin type 9 (PCSK9) levels and cardiovascular risk. However, information regarding PCSK9 level after HCV eradication is lacking. Hence, in this case-control retrospective study, we aimed to evaluate PCSK9 level from pretherapy baseline up to sustained virological response (SVR).

METHODS

Eighty-four patients treated with directly acting antivirals (DAAs) between July 2015 and May 2018 were enrolled. Differences in baseline PCSK9 level due to absence/presence of recorded baseline characteristics (covariates) were evaluated. Changes in PCSK9 levels from pretherapy to SVR (ΔPCSK9) and their correlations with the covariates were assessed. The repeated measures analysis of variance was used to investigate the differences in PCSK9 level from the baseline to the achievement of SVR due to absence/presence of any covariate.

RESULTS

The mean age of the patients was 67.6 ± 11 years, and 53.6% were males. Baseline PCSK9 levels were statistically lower in patients using statins than in those not using statins (mean, 70.3 ± 43.1 ng/mL vs 271.8 ± 252.2 ng/mL; P = .017). PCSK9 level decreased significantly from baseline to the time of SVR (255 ± 248 ng/mL vs 169 ± 188 ng/mL; P < .001). PCSK9 levels were statistically higher in the HCV-infected patients at baseline than in the control group (255 ± 248 vs 166.3 ± 120.2 ng/mL; P = .020); however, this difference was lost after achieving SVR (mean, 169 ± 188 vs 166.3 ± 120.2 ng/mL; P = .464). Changes in PCSK9 level was not statistically related to any of the recorded covariates. The PCSK9 mean level did not differ significantly with absence/presence of any covariate from pretherapy to SVR.

CONCLUSIONS

The reduction in mean PCSK9 level from baseline pretherapy to after HCV eradication was statistically significant. Whether PCSK9 is a new biomarker for cardiovascular risk in these patients remains to be ascertained.

Changes in liver fibrosis in patients with chronic hepatitis C after successful direct-acting antiviral therapy

INTRODUCTION AND OBJECTIVES

After successful treatment of hepatitis C virus (HCV) infection with direct-acting antivirals (DAAs), the stage of liver fibrosis decreases over time. Here, we aimed to assess the changes in the liver fibrosis stage using transient elastography (TE) after successful DAA therapy in HCV-infected cirrhotic patients who were referred to Shariati hospital from 2016 to 2017.

MATERIAL AND METHODS

In this observational cohort, all HCV-infected cirrhotic patients who were treated with a combination of sofosbuvir/daclatasvir, had sustained virologic response (SVR), and had undergone pre- and post-treatment TE, were enrolled. The primary outcome was the changes in TE parameters six months after the end of treatment compared with baseline.

RESULTS

A total of 442 eligible subjects received DAA therapy. Overall, the SVR rate was 96.6%. Of these, 149 patients had completed the protocol and were enrolled. The mean age of patients was 56.1 ± 10.3 years and the predominant sex was male (77.9%). The median (Q₁ -Q₃ ) liver stiffness (LS) value at baseline was 26.3 kPa (18.1-38 kPa), which significantly decreased to 20.9 kPa (12-29.7 kPa) [z = -8.45, P-value < .001]. Also, the liver steatosis of patients with baseline CAP ≥ 220 dB/m had a significant response to treatment [z = -2.3, P-value = .023]. Based on multivariate analysis, a higher baseline liver fibrosis stage was the only determinant of LS values improvement in our study.

CONCLUSION

Successful HCV eradication in patients with liver fibrosis results in significant improvement in LS, even in cirrhotic patients.

Liver Lipids of Patients with Hepatitis B and C and Associated Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) still remains a difficult to cure malignancy. In recent years, the focus has shifted to lipid metabolism for the treatment of HCC. Very little is known about hepatitis B virus (HBV) and C virus (HCV)-related hepatic lipid disturbances in non-malignant and cancer tissues. The present study showed that triacylglycerol and cholesterol concentrations were similar in tumor adjacent HBV and HCV liver, and were not induced in the HCC tissues. Higher levels of free cholesterol, polyunsaturated phospholipids and diacylglycerol species were noted in non-tumorous HBV compared to HCV liver. Moreover, polyunsaturated phospholipids and diacylglycerols, and ceramides declined in tumors of HBV infected patients. All of these lipids remained unchanged in HCV-related HCC. In HCV tumors, polyunsaturated phosphatidylinositol levels were even induced. There were no associations of these lipid classes in non-tumor tissues with hepatic inflammation and fibrosis scores. Moreover, these lipids did not correlate with tumor grade or T-stage in HCC tissues. Lipid reprogramming of the three analysed HBV/HCV related tumors mostly resembled HBV-HCC. Indeed, lipid composition of non-tumorous HCV tissue, HCV tumors, HBV tumors and HBV/HCV tumors was highly similar. The tumor suppressor protein p53 regulates lipid metabolism. The p53 and p53S392 protein levels were induced in the tumors of HBV, HCV and double infected patients, and this was significant in HBV infection. Negative correlation of tumor p53 protein with free cholesterol indicates a role of p53 in cholesterol metabolism. In summary, the current study suggests that therapeutic strategies to target lipid metabolism in chronic viral hepatitis and associated cancers have to consider disease etiology.

Metabolic and cardiovascular complications after virological cure in hepatitis C: What awaits beyond

The association between chronic hepatitis C (CHC) infection and extrahepatic manifestations (EHMs), particularly cardiometabolic diseases, has been extensively examined. However, there has still been insufficient evaluation for these EHMs after virological cure. Several multidirectional mechanisms have been proposed explaining the ability of hepatitis C virus (HCV) developing EHMs, cardiometabolic ones, as well as the effect of antiviral therapy to resolve these EHMs. Data on these manifestations after achieving sustained virologic response (SVR) are still conflicting. However, current evidence suggests that reversal of hepatic steatosis and its coexistent hypocholesterolemia after successful viral eradication led to unfavorable lipid profile, which increases cardiovascular disease (CVD) risk. Additionally, most observations showed that metabolic alterations, such as insulin resistance and diabetes mellitus (DM), undergo some degree of reduction after viral clearance. These changes seem HCV-genotype dependent. Interferon-based antiviral therapy and direct acting antiviral drugs were shown to minimize incidence of DM. Large epidemiological studies that investigated the effect of SVR on CVD showed great discrepancies in terms of results, with predominant findings indicating that CVD events decreased in patients with SVR compared to non-responders or untreated ones. In this review, we present a summary of the current knowledge regarding extrahepatic sequelae of CHC following SVR, which may have an impact on healthcare providers’ clinical practice.

Rapid Decline of Serum Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) in Non-Cirrhotic Patients with Chronic Hepatitis C Infection Receiving Direct-Acting Antiviral Therapy

Direct-acting antivirals (DAAs) efficiently eradicate the hepatitis C virus (HCV). Low-density lipoprotein (LDL) levels increase rapidly upon DAA treatment. Proprotein convertase subtilisin/kexin 9 (PCSK9) induces degradation of the hepatic LDL receptor and thereby elevates serum LDL. The aim of this study was to determine serum PCSK9 concentrations during and after DAA therapy to identify associations with LDL levels. Serum PCSK9 was increased in 82 chronic HCV-infected patients compared to 55 patients not infected with HCV. Serum PCSK9 was low in HCV patients with liver cirrhosis, but patients with HCV-induced liver cirrhosis still exhibited higher serum PCSK9 than patients with non-viral liver cirrhosis. Serum PCSK9 correlated with measures of liver injury and inflammation in cirrhotic HCV patients. In patients without liver cirrhosis, a positive association of serum PCSK9 with viral load existed. Serum PCSK9 was not different between viral genotypes. Serum PCSK9 did not correlate with LDL levels in HCV patients irrespective of cirrhotic status. Serum PCSK9 was reduced, and LDL was increased at four weeks after DAA therapy start in non-cirrhotic HCV patients. Serum PCSK9 and LDL did not change upon DAA treatment in the cirrhotic group. The rapid decline of PCSK9 after the start of DAA therapy in conjunction with raised LDL levels in non-cirrhotic HCV patients shows that these changes are not functionally related.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) levels are not associated with severity of liver disease and are inversely related to cholesterol in a cohort of thirty eight patients with liver cirrhosis

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is of particular importance in cholesterol metabolism with high levels contributing to hypercholesterolemia. Cholesterol and sphingolipids are low in patients with liver cirrhosis. Purpose of this study was to find associations of plasma PCSK9 with circulating cholesterol and sphingolipid species and measures of liver disease severity in patients with liver cirrhosis.

METHODS

PCSK9 protein levels were determined by ELISA in systemic vein (SVP), hepatic vein (HVP) and portal vein plasma of patients with mostly alcoholic liver cirrhosis. PCSK9 and LDL-receptor protein expression were analysed in cirrhotic and non-cirrhotic liver tissues.

RESULTS

Serum PCSK9 was reduced in patients with liver cirrhosis in comparison to non-cirrhotic patients. In liver cirrhosis, plasma PCSK9 was not correlated with Child-Pugh score, Model for End-Stage Liver Disease score, bilirubin or aminotransferases. A negative association of SVP PCSK9 with albumin existed. PCSK9 protein in the liver did not change with fibrosis stage and was even positively correlated with LDL-receptor protein levels. Ascites volume and variceal size were not related to PCSK9 levels. Along the same line, transjugular intrahepatic shunt to lower portal pressure did not affect PCSK9 concentrations in the three blood compartments. Serum cholesterol, sphingomyelin and ceramide levels did not correlate with PCSK9. Stratifying patients by high versus low PCSK9 levels using the median as cut-off, several cholesteryl ester species were even low in the subgroup with high PCSK9 levels. A few sphingomyelin species were also reduced in the patients with PCSK9 levels above the median. PCSK9 is highly expressed in the liver but systemic, portal and hepatic vein levels were similar. PCSK9 was not correlated with the inflammatory proteins C-reactive protein, IL-6, galectin-3, resistin or pentraxin 3. Of note, HVP PCSK9 was positively associated with HVP chemerin and negatively with HVP adiponectin levels.

CONCLUSIONS

In the cohort of patients with liver cirrhosis mostly secondary to alcohol consumption high PCSK9 was associated with low levels of certain cholesteryl ester and sphingomyelin species. Positive correlations of PCSK9 and LDL-receptor protein in the liver of patients with chronic liver injury are consistent with these findings.

Statins and PCSK9 inhibitors: What is their role in coronavirus disease 2019?

Statins and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors interfere with several pathophysiological pathways of coronavirus disease 2019 (COVID-19). Statins may have a direct antiviral effect on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by inhibiting its main protease. Statin-induced up-regulation of angiotensin-converting enzyme 2 (ACE2) may also be beneficial, whereas cholesterol reduction might significantly suppress SARS-CoV-2 by either blocking its host-cell entry through the disruption of lipid rafts or by inhibiting its replication. Available human studies have shown beneficial effects of statins and PCSK9 inhibitors on pneumonia and sepsis. These drugs may act as immunomodulators in COVID-19 and protect against major complications, such as acute respiratory distress syndrome and cytokine release syndrome. Considering their antioxidative, anti-arrhythmic, antithrombotic properties and their beneficial effect on endothelial dysfunction, along with the increased risk of mortality of patients at high cardiovascular risk infected by SARS-CoV-2, statins and PCSK9 inhibitors might prove effective against the cardiovascular and thromboembolic complications of COVID-19. On the whole, randomized clinical trials are needed to establish routine use of statins and PCSK9 inhibitors in the treatment of SARS-CoV-2 infection. In the meantime, it is recommended that lipid-lowering therapy should not be discontinued in COVID-19 patients unless otherwise indicated.

Novel markers of endothelial dysfunction in hepatitis C virus-related cirrhosis: More than a mere prediction of esophageal varices

BACKGROUND

Hepatitis C virus (HCV) infection may affect lipid metabolism by enhancing the circulating levels of inflammatory cytokines, together with its impact on endothelial function.

AIM

To evaluate the potential correlation of changes in lipid profile, carotid intima-media thickness (CIMT), and ankle-brachial index with the severity of fibrosis, grades of esophageal varices (EVs), and fibrosis indices.

METHODS

The study included 240 subjects who were divided into 3 groups; group 1 (n = 90, HCV-related cirrhotic patients with EVs), group 2 (n = 90, HCV-related cirrhotic patients without EVs), and group 3 (n = 60, served as the healthy control group). All patients underwent routine laboratory tests, including a lipid profile assay. Low-density lipoproteins (LDL)/platelet count and platelet/splenic diameter ratios were calculated. Abdominal ultrasonography, CIMT by carotid Doppler, bedside ankle-brachial index (ABI), liver stiffness measurement, and upper gastrointestinal endoscopy were performed.

RESULTS

Multivariate logistic regression revealed that very-low-density lipoprotein (VLDL) (β = 0.988, odds ratio 2.5, P = 0.001), LDL/platelet count ratio (β = 1.178, odds ratio 3.24, P = 0.001), CIMT (β = 1.37, odds ratio 3.9, P = 0.001), and ABI (β = 2.3, odds ratio 5.9, P = 0.001) were the key variables associated with significant fibrosis, EVs and endothelial dysfunction. CIMT and LDL/platelet count ratio were predictive of advanced fibrosis and EVs at cutoff values of 1.1 mm and 1 mm, respectively, with an area under the curve (AUC) of 0.966 and 0.960 (P = 0.001), while VLDL and ABI at a cutoff of 16.5 mg/dL and 0.94 were predictive of advanced fibrosis and EVs with an AUC of 0.891 and 0.823, respectively (P = 0.001).

CONCLUSION

CIMT, ABI, VLDL, LDL/platelet count ratio are good non-invasive predictors of advanced fibrosis, presence of EVs, and endothelial dysfunction in liver cirrhosis.

Transcriptome and miRNome Analysis Provide New Insight Into Host Lipid Accumulation, Innate Immunity, and Viral Persistence in Hepatitis C Virus Infection in vitro

Hepatitis C virus (HCV)-host cell interaction during infection disturbs cellular homeostasis and culminates in pathological consequences. The processes could be first embodied in gene expression of HCV-infected cells. Here, we investigated transcriptome and miRNA expression (miRNome) alterations in HCV-infected Huh7 cells at 12, 36, and 60 h after infection to systematically explore host responses. The number of deregulated genes in the HCV-infected cells increased with infection duration. The altered biological processes at 36 h were mainly associated with stress and inflammatory response, whereas the most enriched processes at 60 h were predominantly linked to lipid metabolism. Notably, the key genes that participated in lipogenesis were downregulated, and conversely, the genes implicated in fatty acid beta-oxidation were upregulated. Reduced expression of the key genes involved in lipoprotein assembly and secretion pointed to a decreased requirement for and export of lipids, leading to lipid accumulation in HCV-infected hepatocytes. Fluctuation in the expression of host factors, innate immunity genes and transcription factors provided insight into host-directed mechanisms to control viral replication. Furthermore, miRNome presented a comprehensive expression profile of miRNAs in HCV-infected Huh7 cells. The integrated analysis of transcriptome and miRNome suggested that deregulated miR-483, miR-1303, miR-1260a, miR-27a^∗, and miR-21^∗ directly regulated lipid metabolical genes at 60 h. The decreased miR-122 at 60 h was indirectly involved in lipid metabolism and is expected to attenuate rampant replication of HCV and potentially contribute to viral persistence. Our results will help to gain a comprehensive understanding of the molecular mechanisms implicated in HCV-induced pathogenesis.

PCSK9 Levels Are Raised in Chronic HCV Patients with Hepatocellular Carcinoma

Background: Since emerging evidence suggests a protective role of proprotein convertase subtilisin/kexin type 9 (PCSK9) on hepatitis C virus (HCV) infection, the aim of the present study was to evaluate the correlation between PCSK9 and HCV infection in hepatocellular carcinoma (HCC) patients. Methods: In this retrospective study, PCSK9 levels were evaluated by ELISA, in plasma samples from control (n = 24) and 178 patients diagnosed for HCC, cirrhosis, or chronic hepatitis, either positive or negative for HCV. Results: HCV positive patients (HCV+) presented with higher PCSK9 levels compared to HCV negative individuals (HCV-), 325.2 ± 117.7 ng/mL and 256.7 ± 139.5 ng/mL, respectively. This difference was maintained in the presence of HCC, although this disease significantly reduced PCSK9 levels. By univariate analysis, a positive correlation between PCSK9 and HCV viral titer was found, being G2 genotype the most-potent inducer of PCSK9 among other genotypes. This induction was not associated with changes in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG). A negative correlation was also found between PCSK9 levels and liver impairment, assessed by Model for End-Stage Liver Disease (MELD). Finally, a multivariate correlation analysis corrected for age, TC, LDL-C, and sex, demonstrated, in the whole cohort, a positive association between PCSK9 and HCV and a negative with HCC. Conclusions: taken together, our study reveals that HCV raised PCSK9 in both the presence and absence of HCC.

The LDL-Receptor and its Molecular Properties: From Theory to Novel Biochemical and Pharmacological Approaches in Reducing LDL-cholesterol

BACKGROUND

The Low-Density Lipoprotein (LDL) Receptor (LDL-R) is a transmembrane protein playing a crucial role in effective lipid homeostasis. Various therapeutic agents have been used in the management of dyslipidemias, however, the outcome of therapeutic target is debated.

OBJECTIVE

The aim of this review is to summarize and fully understand the current concept regarding LDL-R and its molecular properties, metabolic pathway, factors affecting LDL-R activity and all available pharmacological interventions. Additionally, non-lipid related properties of LDL-R are also referred.

METHODS

Literature from the PubMed database was extracted to identify papers between 1984 to 2017 regarding LDL-R and therapeutic agents on dyslipidemia management.

RESULTS

We analyzed basic data regarding agents associated with LDL-R (Sterol Regulating Element-Binding Proteins - SREBPs, Protein ARH, IDOL, Thyroid Hormones, Haematologic Disorders, Protein convertase subtilisin kexintype 9 - PCSK-9, ApoC-III) as well as non-lipid related properties of LDL-R, while all relevant (common and novel) pharmacological interventions (statins, fibrates, cholesterol absorption inhibitors, bile acid sequestrants and PCSK- 9) are also referred.

CONCLUSION

LDL-R and its molecular properties are involved in lipid homeostasis, so potentially sets the therapeutic goals in cardiovascular patients, which is usually debated. Further research is needed in order to fully understand its properties, as well as to find the potential pharmacological interventions that could be beneficial in cholesterol homeostasis and various morbidities in order to reach the most appropriate therapeutic goal.

Extracellular vesicles restrict dengue virus fusion in Aedes aegypti cells

Aedes aegypti is the primary vector of dengue virus (DENV), and acquires this virus from a vertebrate host during blood feeding. Previous literature has shown that vertebrate blood factors such as complement protein C5a and low-density lipoprotein (LDL) influence DENV acquisition in the mosquito. Here, we show that extracellular vesicles in cell culture medium inhibit DENV infection in mosquito cells. Specifically, extracellular vesicles enter into mosquito cells and inhibit an early stage of infection. Extracellular vesicles had no effect on virus cell attachment or entry. Instead, extracellular vesicles restricted virus membrane fusion. Extracellular vesicles only inhibited DENV infection in mosquito cells and not vertebrate cells. These data highlight a novel virus-vector-host interaction that limits virus infection in mosquito cells by restricting virus membrane fusion.

Association of Serum PCSK9 Levels with Antibiotic Resistance and Severity of Disease in Patients with Bacterial Infections Admitted to Intensive Care Units

BACKGROUND

The results of several studies have suggested that infections and sepsis, either bacterial or viral, might be associated with elevated plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels. Since there are no data on PCSK9 levels and antibiotic resistance or the severity of disease in patients with bacterial infections in intensive care units, the aim of this study was to investigate whether any such associations exist.

METHODS

100 patients (46 males, mean age 67.12 ± 1.34 years) with bacterial infections who were staying in an intensive care unit (ICU) longer than 48 h but less than 7 days and who were not receiving corticosteroids were analyzed. Their serum levels of albumin, C-reactive protein, glucose, lactate, blood urea nitrogen, prothrombin (international normalized ratio), total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, PCSK9, and procalcitonin were measured. The severity of the patients' condition was assessed by using the Glasgow Coma Scale (GCS), the Sequential Organ Failure Assessment (SOFA), and the Acute Physiology and Chronic Health Evaluation II (APACHE II) scales.

RESULTS

Using a hierarchical regression modeling approach, no significant association was found between PCSK9 levels and either the severity of disease (APACHE II, SOFA, and GCS) indices or resistance to antibiotics.

CONCLUSION

The results suggest that there is no association between PCSK9 levels and resistance to antibiotics or the condition of patients hospitalized in intensive care units.

Cognitive impairments in HCV infection: From pathogenesis to neuroimaging

Extrahepatic manifestations of hepatitis C virus (HCV) infection, in particular cognitive impairments, can be present in the absence of clinical liver dysfunction. Executive memory, attention, and concentration are cognitive domains that are most frequently affected. Microstructural and functional changes in cortical gray matter and basal ganglia associate these neuropsychiatric changes in early HCV infection. No study has covered the relationship between imaging features of HCV-related cognitive impairment and HCV pathology. Herein we summarize evidence suggesting a direct pathology of HCV in microglia, astrocytes, and microvascular endothelial cells, and a neuroinflammatory response in HCV-related cognitive decline. Lipoproteins and their receptors mediate HCV infectivity in the central nervous system and confer susceptibility to HCV-related cognitive decline. Magnetic resonance spectroscopy has revealed changes compatible with reactive gliosis and microglial activation in basal ganglia, frontal and occipital white matter, in the absence of cirrhosis or hepatic encephalopathy. Similarly, diffusion imaging shows evidence of structural disintegrity in the axonal fibers of white matter tracts associated with temporal and frontal cortices. We also discuss the cognitive benefits and side-effects of the two most popular therapeutic protocols interferon-based therapy and interferon-free therapy using direct acting anti-virals. Evidences support a network-based pattern of disruption in functional connectivity in HCV patients and a common neuronal substrate for HCV-related and interferon-therapy-associated cognitive decline. These evidences might help identify patients who benefit from either interferon-based or interferon-free treatment regimen.

The Impact of Mevastatin on HCV Replication and Autophagy of Non-Transformed HCV Replicon Hepatocytes Is Influenced by the Extracellular Lipid Uptake

Statins efficiently inhibit cholesterol synthesis by blocking 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase in the mevalonate pathway. However, the effect of statins on intracellular cholesterol is partially counterbalanced by a consequent increased uptake of extracellular lipid sources. Hepatitis C virus (HCV) infection induces intracellular accumulation of cholesterol by promoting both new synthesis and uptake of circulating lipoproteins, which is required for HCV replication and release. Hepatocytes respond to the increase in intracellular cholesterol levels by inducing lipophagy, a selective type of autophagy mediating the degradation of lipid deposits within lysosomes. In a cellular system of HCV replication based on HuH7 hepatoma cells, statin treatment was shown to be sufficient to decrease intracellular cholesterol, which is accompanied by reduced HCV replication and decreased lipophagy, and has no apparent impact on endocytosis-mediated cholesterol uptake. To understand whether these results were influenced by an altered response of cholesterol influx in hepatoma cells, we analyzed the effect of statins in non-transformed murine hepatocytes (MMHD3) harboring subgenomic HCV replicons. Notably, we found that total amount of cholesterol is increased in MMHD3 cells upon mevastatin treatment, which is associated with increased HCV replication and lipophagy. Conversely, mevastatin is able to reduce cholesterol amounts only when cells are grown in the presence of delipidated serum to prevent extracellular lipid uptake. Under this condition, HCV replication is reduced and autophagy flux is severely impaired. Altogether, these results indicate that both de novo synthesis and extracellular uptake have to be targeted in non-transformed hepatocytes in order to decrease intracellular cholesterol levels and consequently limit HCV replication.

Changes in serum LDL, PCSK9 and microRNA-122 in patients with chronic HCV infection receiving Daclatasvir/Asunaprevir

The present study evaluated the changes in lipid profile, and the associations between serum protein convertase subtilisin/kexin 9 (PCSK9), microRNA (miR)122 and low-density lipoprotein variation following treatment of hepatitis C virus (HCV) genotype 1b infection with Daclatasvir/Asunaprevir. A total of 39 patients with HCV genotype 1b infection with chronic hepatitis received a 24-week treatment regimen of Daclatasvir/Asunaprevir. Laboratory data were obtained for each subject every 4 weeks during treatment and every 12 weeks after treatment. Serum miR122 and PCSK9 were measured at the start of treatment (week 0), end of treatment (week 24), 4 weeks after the end of treatment (week 28), 12 weeks after the end of treatment (week 36) and 28 weeks after the end of treatment (week 52). LDL was increased at week 4 after the start of treatment to week 52. The increased LDL/HDL ratio at week 52 compared with week 4 was also associated with relative miR122 at week 52. At week 4, PCSK9-active form (A) was lower than that at other time points, and PCSK9-inactive form (I) exhibited the greatest increase. At week 52, PCSK9-A was higher than that during treatment, but PCSK9-I level at week 52 did not markedly differ from that any time point except for week 4. Relative miR122 at week 4 was associated with increased PCSK9-A at weeks 36 and 52 from the start of DAA. In summary, treatment of HCV with Daclatasvir/Asunaprevir resulted in elevated LDL, and relative miR122 and PCSK9-A levels in serum appeared to have some association with LDL increase.

Liver steatosis and dyslipidemia after HCV eradication by direct acting antiviral agents are synergistic risks of atherosclerosis

Aim

We comprehensively analyzed how hepatitis C virus (HCV) eradication by interferon (IFN)-free direct-acting-antiviral-agents (DAAs) affects liver steatosis and atherogenic risk.

Methods

Patients treated with IFN-free-DAAs who underwent transient elastography before and at 24-weeks post-treatment, including controlled attenuation parameter (CAP), and achieved sustained viral response (SVR) were enrolled. The association between changes in liver steatosis, lipid-metabolism, and genetic and clinical factors was analyzed.

Results

A total of 117 patients were included. The mean CAP and low-density lipoprotein cholesterol (LDL-C) levels were significantly elevated at SVR24. However, baseline LDL-C and CAP values were significantly negatively correlated with changes in these values after HCV eradication, indicating that in patients with high baseline values, the values generally decreased after HCV eradication. Mean small-dense LDL-C (sdLDL-C), which has greater atherogenic potential, was significantly elevated only in patients with both dyslipidemia (LDL-C >140 mg/dL) and liver steatosis (CAP >248 dB/m) at SVR24. Those patients had significant higher baseline BMI, LDL-C, and total-cholesterol levels.

Conclusions

Generally, successful HCV eradication by IFN-free-DAAs decreases CAP and LDL-C in patients with high baseline values. However, elevated LDL-C was accompanied with elevated sdLDL-C only in patients with liver steatosis and dyslipidemia at SVR24; therefore, those patients may require closer monitoring.

The Multifaceted Roles of Autophagy in Flavivirus-Host Interactions

Autophagy is an evolutionarily conserved cellular process in which intracellular components are eliminated via lysosomal degradation to supply nutrients for organelle biogenesis and metabolic homeostasis. Flavivirus infections underlie multiple human diseases and thus exert an immense burden on public health worldwide. Mounting evidence indicates that host autophagy is subverted to modulate the life cycles of flaviviruses, such as hepatitis C virus, dengue virus, Japanese encephalitis virus, West Nile virus and Zika virus. The diverse interplay between autophagy and flavivirus infection not only regulates viral growth in host cells but also counteracts host stress responses induced by viral infection. In this review, we summarize the current knowledge on the role of autophagy in the flavivirus life cycle. We also discuss the impacts of virus-induced autophagy on the pathogeneses of flavivirus-associated diseases and the potential use of autophagy as a therapeutic target for curing flavivirus infections and related human diseases.

Immunometabolic Effect of Cholesterol in Hepatitis C Infection: Implications in Clinical Management and Antiviral Therapy

Hepatitis C virus (HCV) is a lipid-enveloped virion particle that causes infection to the liver, and as part of its life cycle, it disrupts the host lipid metabolic machinery, particularly the cholesterol synthesis pathway. The innate immune response generated by liver resident immune cells is responsible for successful viral eradication. Unfortunately, most patients fail to eliminate HCV and progress to chronic infection. Chronic infection is associated with hepatic fat accumulation and inflammation that triggers fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Despite that the current direct-acting antiviral agents have increased the cure rate of HCV infection, viral genotype and the host genetic background influence both the immune response and lipid metabolism. In this context, recent evidence has shown that cholesterol and its derivatives such as oxysterols might modulate and potentialize the hepatic innate immune response generated against HCV. The impairment of the HCV life cycle modulated by serum cholesterol could be relevant for the clinical management of HCV-infected patients before and after treatment. Alongside, cholesterol levels are modulated either by genetic variations in IL28B, ApoE, and LDLR or by dietary components. Indeed, some nutrients such as unsaturated fatty acids have demonstrated to be effective against HCV replication. Thus, cholesterol modifications may be considered as a new adjuvant strategy for HCV infection therapy by providing a biochemical tool that guides treatment decisions, an improved treatment response and favoring viral clearance. Herein, the mechanisms by which cholesterol contributes to the immune response against HCV infection and how genetic and environmental factors may affect this role are reviewed.

Pleiotropic effects of proprotein convertase subtilisin/kexin type 9 inhibitors?

PURPOSE OF REVIEW

Current data suggest that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors may affect many metabolic pathways beyond lowering LDL cholesterol. The aim of the present manuscript is to present these so-called pleiotropic effects of PCSK9 inhibitors.

RECENT FINDINGS

PCSK9 may affect the activity of other receptors beyond LDL receptors (LDLR), such as cluster of differentiation 36 (CD36), very-low-density-lipoprotein (VLDL) receptors, apolipoprotein (Apo) E receptors, LDLR-related protein 1 (LRP-1) and ATP-Binding Cassette Transporter (ABCA1). Thus, a role of PCSK9 in the development of atherosclerosis, in vascular wall inflammation and in platelet function has been suggested. Additionally, PCSK9 inhibitors may affect lipid variables beyond LDL cholesterol, carbohydrate variables, as well as they may affect brain and kidney function. Additionally, a controversial role of PCSK9 in sepsis, hepatitis C infection and Alzheimer's disease has been suggested.

SUMMARY

These possible pleiotropic effects of PCSK9 inhibitors need further research, as they may affect cardiovascular risk and provide further insights in the development of atherosclerosis and other diseases such as Alzheimer's disease or chronic viral infection and sepsis.

Identification of potential anti-hepatitis C virus agents targeting non structural protein 5B using computational techniques

Hepatitis C virus (HCV) nonstructural protein 5B (NS5B) is an RNA-dependent RNA polymerase that plays a key role in HCV replication, and, hence, NS5B is an attractive target for hepatitis C drug discovery. Hepatitis C is a chronic liver disease affecting the global population significantly. Many NS5B inhibitors targeting active site were launched in recent years, however, still there exists a pressing need for cost-effective therapies with pan genotypic activity and therapies targeting niche HCV population with comorbities and resistant to earlier therapies. The objective of the current study is to identify potential anti-HCV agents from FDA approved drugs that are already in the market for a different disease-Drug repurposing approach. A combination of computational chemistry and computational biology techniques was used to discover potential therapies for hepatitis C targeting the NS5B Thumb I allosteric site. Computational chemistry analysis emphasized the fact that fluvastatin, a lipid lowering agent, and olopatadine, an antihistamine, exhibited good binding affinity to NS5B. In addition, gene set enrichment analysis brought to light the significant overlap between disease characteristic features and the mechanism of action of fluvastatin and olopatadine. The current study concludes the potentially beneficial use of fluvastatin in niche hepatitis C patient population suffering from nonalcoholic fatty liver diseases.

Proprotein convertase subtilisin/kexin type 9 inhibits interferon β expression through interacting with ATF-2

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates lipid metabolism. A mutual interplay of lipid homeostasis and innate immune system has been increasingly recognized. We, therefore, studied the effect of PCSK9 on interferon (IFN) β expression. We show that PCSK9 decreases IFNβ promoter/enhancer activity, mRNA and protein levels, and its downstream 2',5'-oligoadenylate synthetase-1 mRNA level. ProPCSK9, but not the cleaved PCSK9, down-regulates IFNβ promoter/enhancer activity. Moreover, PCSK9 decreases IFNβ promoter/enhancer activity through the positive regulatory domain IV region where the activating transcription factor-2 (ATF-2)/c-Jun heterodimer binds. Mechanistically, we demonstrate an interaction between PCSK9 and ATF-2, which reduces ATF-2/c-Jun dimerization and ATF-2/c-Jun binding to the IFNβ enhancer. This novel function of PCSK9 should have important implications in optimizing the clinical use of PCSK9 inhibitors.

Hepatitis C virus regulates proprotein convertase subtilisin/kexin type 9 promoter activity

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secretory serine protease mainly expressed in liver. Although PCSK9 has been shown to inhibit hepatitis C virus (HCV) entry and replication, whether HCV regulates PCSK9 transcription has not been well studied. PCSK9 promoter activity is modulated by numerous transcription factors including sterol-regulatory element binding protein (SREBP)-1a, -1c, -2, hepatocyte nuclear factor-1 (HNF-1), and forkhead box O3 (FoxO3). Since they are differently regulated by HCV, we studied the effects of these transcription factors on PCSK9 promoter activity in the context of HCV infection and replication. We demonstrated that PCSK9 promoter activity was up-regulated after HCV infection and in HCV genomic replicon cells. We also studied the effects of HCV proteins on the PCSK9 promoter activity. While HCV structural proteins core, E1, and E2 had no effect, NS2, NS3, NS3-4A, NS5A and NS5B enhanced, and p7 and NS4B decreased PCSK9 promoter activity. Furthermore, we showed that transcription factors SREBP-1c, HNF-1α and specificity protein 1 increased PCSK9 promoter activity in HCV replicon cells, whereas SREBP-1a, HNF-1β and FoxO3 had an inhibitory effect. These results demonstrated the molecular mechanisms of how HCV modulates PCSK9 promoter activity and advanced our understanding on the mutual interactions between HCV and PCSK9.

Proprotein convertase subtilisin/kexin type 9 inhibits hepatitis C virus replication through interacting with NS5A

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease actively involved in regulating lipid homeostasis. Although PCSK9 has been shown to inhibit hepatitis C virus (HCV) entry and replication, the underlying mechanisms have not been thoroughly characterized. Moreover, whether PCSK9 regulates HCV translation and assembly/secretion has not been determined. We therefore further studied the effects of PCSK9 on the HCV life cycle. We showed that PCSK9 did not affect HCV translation or assembly/secretion. Overexpression of PCSK9 inhibited HCV replication in HCV genomic replicon cells in a dose-dependent manner and after cell culture-derived HCV (HCVcc) infection. Knocking down PCSK9 increased HCV replication. The gain-of-function (D374Y) or loss-of-function (Δaa. 31-52) PCSK9 mutants for low-density lipoprotein receptor (LDLR) degradation had no effect on HCV replication, suggesting that HCV replication inhibition by PCSK9 was not due to LDLR degradation. The uncleaved ProPCSK9, but not cleaved PCSK9, down-regulated HCV replication, suggesting that the auto-cleavage of PCSK9 affected HCV replication. We also found that PCSK9 interacted with NS5A through NS5A aa. 95-215, and this region played an important role in NS5A dimerization, NS5A-RNA binding and was essential for HCV replication. More importantly, NS5A dimerization and NS5A-RNA binding were suppressed by PCSK9 upon interaction. These results suggested that PCSK9 inhibited HCV replication through interaction with NS5A. Our study should help optimize anti-HCV treatment regimen in patients with abnormal lipid profiles.

Low density lipopolyprotein inhibits flavivirus acquisition in Aedes aegypti

Aedes aegypti is the primary vector of a number of human pathogens including dengue virus (DENV) and Zika virus (ZIKV). Ae. aegypti acquires these viruses during the processing of bloodmeals obtained from an infected vertebrate host. Vertebrate blood contains a number of factors that have the potential to modify virus acquisition in the mosquito. Interestingly, low density lipopolyprotein (LDL) levels are decreased during severe DENV infection. Accordingly, we hypothesized that LDL is a modifiable factor that can influence flavivirus acquisition in the mosquito. We found that LDL is endocytosed by Ae. aegypti cells in a dynamin-dependent manner. LDL is also endocytosed by midgut epithelial cells and accumulates at the luminal midgut epithelium during bloodmeal digestion. Importantly, pretreatment with LDL, but not high density lipopolyprotein (HDL), significantly inhibited both DENV and ZIKV infection in vitro, and LDL inhibited ZIKV infection in vivo. This study identifies human LDL or 'bad cholesterol' as a modifiable factor that can inhibit flavivirus acquisition in Ae. aegypti. Identification of modifiable blood factors and critical cellular interactions that mediate pathogen acquisition may lead to novel strategies to disrupt the transmission cycle of vector-borne diseases.