Immune control and failure in HCV infection--tipping the balance

Contemporary Insights into Hepatitis C Virus: A Comprehensive Review

Hepatitis C virus (HCV) remains a significant global health challenge. Approximately 50 million people were living with chronic hepatitis C based on the World Health Organization as of 2024, contributing extensively to global morbidity and mortality. The advent and approval of several direct-acting antiviral (DAA) regimens significantly improved HCV treatment, offering potentially high rates of cure for chronic hepatitis C. However, the promising aim of eventual HCV eradication remains challenging. Key challenges include the variability in DAA access across different regions, slightly variable response rates to DAAs across diverse patient populations and HCV genotypes/subtypes, and the emergence of resistance-associated substitutions (RASs), potentially conferring resistance to DAAs. Therefore, periodic reassessment of current HCV knowledge is needed. An up-to-date review on HCV is also necessitated based on the observed shifts in HCV epidemiological trends, continuous development and approval of therapeutic strategies, and changes in public health policies. Thus, the current comprehensive review aimed to integrate the latest knowledge on the epidemiology, pathophysiology, diagnostic approaches, treatment options and preventive strategies for HCV, with a particular focus on the current challenges associated with RASs and ongoing efforts in vaccine development. This review sought to provide healthcare professionals, researchers, and policymakers with the necessary insights to address the HCV burden more effectively. We aimed to highlight the progress made in managing and preventing HCV infection and to highlight the persistent barriers challenging the prevention of HCV infection. The overarching goal was to align with global health objectives towards reducing the burden of chronic hepatitis, aiming for its eventual elimination as a public health threat by 2030.

Immune System and Hepatocellular Carcinoma (HCC): New Insights into HCC Progression

According to the WHO's recently released worldwide cancer data for 2020, liver cancer ranks sixth in morbidity and third in mortality among all malignancies. Hepatocellular carcinoma (HCC), the most common kind of liver cancer, accounts approximately for 80% of all primary liver malignancies and is one of the leading causes of death globally. The intractable tumor microenvironment plays an important role in the development and progression of HCC and is one of three major unresolved issues in clinical practice (cancer recurrence, fatal metastasis, and the refractory tumor microenvironment). Despite significant advances, improved molecular and cellular characterization of the tumor microenvironment is still required since it plays an important role in the genesis and progression of HCC. The purpose of this review is to present an overview of the HCC immune microenvironment, distinct cellular constituents, current therapies, and potential immunotherapy methods.

The liver cancer immune microenvironment: Therapeutic implications for hepatocellular carcinoma

The liver is the sixth most common site of primary cancer in humans and the fourth leading cause of cancer-related death in the world. Hepatocellular carcinoma (HCC) accounts for 90% of liver cancers. HCC is a prevalent disease with a progression that is modulated by the immune system. Half of the patients with HCC receive systemic therapies, traditionally sorafenib or lenvatinib, as a first-line therapy. In the last few years, immune-checkpoint inhibitors (ICIs) have revolutionized cancer therapy and have gained an increased interest in the treatment of HCC. In 2020, the combination of atezolizumab (anti-programmed death-ligand 1) and bevacizumab (anti-vascular endothelial growth factor) improved overall survival over sorafenib, resulting in Food and Drug Administration (FDA) approval as a first-line treatment for patients with advanced HCC. Despite these major advances, a better molecular and cellular characterization of the tumor microenvironment is still needed because it has a crucial role in the development and progression of HCC. Inflamed (hot) and noninflamed (cold) HCC tumors and genomic signatures have been associated with response to ICIs. However, there are no additional biomarkers to guide clinical decision-making. Other immune-targeting strategies, such as adoptive T-cell transfer, vaccination, and virotherapy, are currently under development. This review provides an overview on the HCC immune microenvironment, different cellular players, current available immunotherapies, and potential immunotherapy modalities.

The Role of B Cells in Adult and Paediatric Liver Injury

B lymphocytes are multitasking cells that direct the immune response by producing pro- or anti-inflammatory cytokines, by presenting processed antigen for T cell activation and co-stimulation, and by turning into antibody-secreting cells. These functions are important to control infection in the liver but can also exacerbate tissue damage and fibrosis as part of persistent inflammation that can lead to end stage disease requiring a transplant. In transplantation, immunosuppression increases the incidence of lymphoma and often this is of B cell origin. In this review we bring together information on liver B cell biology from different liver diseases, including alcohol-related and metabolic fatty liver disease, autoimmune hepatitis, primary biliary and primary sclerosing cholangitis, viral hepatitis and, in infants, biliary atresia. We also discuss the impact of B cell depletion therapy in the liver setting. Taken together, our analysis shows that B cells are important in the pathogenesis of liver diseases and that further research is necessary to fully characterise the human liver B cell compartment.

Transplantation of liver from hepatitis C-infected donors to hepatitis C RNA-negative recipients: Histological and virologic outcome

BACKGROUND

The virologic and histologic outcomes of a hepatitis C virus (HCV)-infected liver graft into an HCV-negative recipient are not well understood. We aimed to evaluate the sustained virologic response (SVR) rate and the liver histology at 1 year post-Orthotopic liver transplantation (OLT) with an HCV-infected graft.

METHODS

A total of 33 patients received the HCV antibody (Ab)+/nucleic acid amplification test (NAT)+ graft. Of these patients, 23 were HCV-negative recipients and 10 were HCV-positive recipients. The 1-year biopsy data were available for 24 patients: 15 patients in HCV-negative group who received an HCV Ab+/NAT+graft and 9 patients in HCV-positive group who received an HCV Ab+/NAT+ graft. Patients with (+) HCV ribonucleic acid (RNA) were started on direct-acting antiviral (DAA) treatment approximately 107 days after OLT using either a Glecaprevir-Pibrentasvir or Sofosbuvir-Velpatasvir or Sofosbuvir-Ledipasvir.

RESULTS

All patients (n = 33) were treated with DAA and achieved SVR. The 1-year post-OLT liver biopsies were available in 24 patients: 9 patients had F1 and F2 fibrosis and 17 patients had minimal to moderate inflammation. There was no statistical difference in fibrosis and inflammation between the HCV-negative vs. HCV-positive recipients. All patients who received the NAT+ graft developed viremia and subsequently achieved SVR with treatment.

CONCLUSION

At 1 year protocol liver biopsy, patients had inflammation consistent with viral hepatitis despite the successful eradication of HCV.

Immune system control of hepatitis C virus infection

Hepatitis C virus (HCV) remains a global public health problem even though more than 95% of infections can be cured by treatment with direct-acting antiviral agents. Resolution of viremia post antiviral therapy does not lead to protective immunity and therefore reinfections can occur. Immune cell detection of HCV activates signaling pathways that produce interferons and trigger the innate immune response against the virus, preventing HCV replication and spread. Cells in the innate immune system, including natural killer, dendritic, and Kupffer cells, interact with infected hepatocytes and present viral antigens to T and B cells where their effector responses contribute to infection outcome. Despite the immune activation, HCV can evade the host response and establish persistent infection. Plans to understand the correlates of protection and strategies to activate proper innate and adaptive immune responses are needed for development of an effective prophylactic vaccine that stimulates protective immunity and limits HCV transmission.

Deletion of a decoy epitope in porcine circovirus 2 (PCV2) capsid protein affects the protective immune response in mice

The swine pathogen porcine circovirus type 2 (PCV2) causes significant economic damage worldwide. The PCV2 capsid (CP) residues 169-STIDYFQPNNKR-180 have been identified as a decoy epitope that diverts the host immune response away from protective epitopes. However, the decoy epitope may include important linear or conformational protective epitopes against PCV2. In this study, we used the baculovirus system to express recombinant complete CP (1-233) and mutant CP (Δ169-180), in which the decoy epitope was deleted, and evaluated the immune response to these in mice. Immunization with mutant CP (Δ169-180) protein, which formed very low level of virus-like particles (VLPs), elicited significantly lower levels of PCV2 CP-specific IgG antibodies and a slightly lower neutralizing activity than immunization with the complete CP (1-233) protein. This finding suggests that the complete CP is important for efficient VLP assembly and induction of PCV2-specific IgG antibodies and neutralizing antibodies in mice. This study may provide useful information for next-generation vaccine design for PCV2 control.

Improving the aqueous solubility of HCV-E2 glycoprotein epitope mimics by cyclization using POLAR hinges

In this research we describe the improvement of the water-solubility of cyclic epitope mimics based on the HCV E2 glycoprotein by incorporation of suitable polar hinges. The poor solubility of epitope mimics based on peptide sequences in the envelope (E2) protein hampered their synthesis and purification and made it very difficult to prepare the molecular constructs for evaluation of their bioactivity. Since changes in the amino acid composition are hardly possible in these epitope mimics in order to increase water-solubility, a polar cyclization hinge may offer a remedy leading to a significant increase of polarity and therefore water solubility. These polar hinges were applied in the synthesis of better water-soluble HCV-E2 epitopes. An azide functionality in the polar hinges allowed attachment of a tetraethylene glycol linker by Cu-catalyzed azide-alkyne cyclo-addition (CuAAC) for a convenient conjugation to ELISA plates in order to evaluate the bio-activity of the epitope mimics. The immunoassays showed that the use of more polar cyclization hinges still supported anti-HCV antibody recognition and did not negatively influence their binding. This significantly increased solubility induced by polar hinges should therefore allow for the molecular construction and ultimate evaluation of synthetic vaccine molecules.

Paradoxical Roles of Oxidative Stress Response in the Digestive System before and after Carcinogenesis

Oxidative stress is recognized as a cancer-initiating stress response in the digestive system. It is produced through mitochondrial respiration and induces DNA damage, resulting in cancer cell transformation. However, recent findings indicate that oxidative stress is also a necessary anticancer response for destroying cancer cells. The oxidative stress response has also been reported to be an important step in increasing the anticancer response of newly developed molecular targeted agents. Oxidative stress might therefore be a cancer-initiating response that should be downregulated in the precancerous stage in patients at risk of cancer but an anticancer cell response that should not be downregulated in the postcancerous stage when cancer cells are still present. Many commercial antioxidant agents are marketed as “cancer-eliminating agents” or as products to improve one’s health, so cancer patients often take these antioxidant agents. However, care should be taken to avoid harming the anticancerous oxidative stress response. In this review, we will highlight the paradoxical effects of oxidative stress and antioxidant agents in the digestive system before and after carcinogenesis.

Association of IL28B (IFNL3) rs12979860 mRNA levels, viral load, and liver function among HCV genotype 1a patients

AIM

The present study was designed to evaluate the correlation of interleukin 28B (IL28B, IFNL3) rs12979860 mRNA levels, viral load, and liver function among hepatitis C virus (HCV) patients genotype 1a.

BACKGROUND

HCV is considered essentially hepatotropic and is a major health problem around the world.

METHODS

This study included 100 HCV-infected patients with HCV genotype1a (G1a) and rs12979860 CC genotype. These patients were divided into two groups according to HCV treatment. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and HCV Load were measured and recorded for each patient. IL28B mRNA levels were determined using real-time polymerase chain reaction assay, and their correlation with clinical data were analyzed. STRING was applied to construct a network and identify interactions between IL28B (IFNL3) and its significant neighbor proteins.

RESULTS

The results revealed a significant relationship between the ALT as well as ALP levels with IL28B rs12979860 mRNA expression level in men, and also with age >50 years. In the treated group, AST level and HCV load had a significant relationship with IL28B mRNA expression level. The results showed that the level of ALP and AST decreased significantly with increased IL28B mRNA expression level in the treated and untreated group, respectively. STRING database showed that IL28B (IFNL3) interacted with ten important neighbor proteins with some of these proteins being involved in signal transduction pathway activating antiviral response.

CONCLUSION

This study indicated that rs12979860CC genotype could predict IL28B mRNA expression level in HCV-infected patients with G1a. Furthermore, IL28B mRNA expression level may serve as a useful marker for the development of G1a HCV-associated outcomes.

Antibody Repertoire Analysis of Hepatitis C Virus Infections Identifies Immune Signatures Associated With Spontaneous Clearance

Hepatitis C virus (HCV) is a major public health concern, with over 70 million people infected worldwide, who are at risk for developing life-threatening liver disease. No vaccine is available, and immunity against the virus is not well-understood. Following the acute stage, HCV usually causes chronic infections. However, ~30% of infected individuals spontaneously clear the virus. Therefore, using HCV as a model for comparing immune responses between spontaneous clearer (SC) and chronically infected (CI) individuals may empower the identification of mechanisms governing viral infection outcomes. Here, we provide the first in-depth analysis of adaptive immune receptor repertoires in individuals with current or past HCV infection. We demonstrate that SC individuals, in contrast to CI patients, develop clusters of antibodies with distinct properties. These antibodies' characteristics were used in a machine learning framework to accurately predict infection outcome. Using combinatorial antibody phage display library technology, we identified HCV-specific antibody sequences. By integrating these data with the repertoire analysis, we constructed two antibodies characterized by high neutralization breadth, which are associated with clearance. This study provides insight into the nature of effective immune response against HCV and demonstrates an innovative approach for constructing antibodies correlating with successful infection clearance. It may have clinical implications for prognosis of the future status of infection, and the design of effective immunotherapies and a vaccine for HCV.

IL-15 and IFN-γ signal through the ERK pathway to inhibit HCV replication, independent of type I IFN signaling

Despite effective new treatments for Hepatitis C virus (HCV) infection, development of drug resistance, safety concerns and cost are remaining challenges. More importantly, there is no vaccine available against hepatitis C infection. Recent data suggest that there is a strong correlation between spontaneous HCV clearance and human NK cell function, particularly IFN-γ production. Further, IL-15 has innate antiviral activity and is also one of the main factors that activates NK cells to produce IFN-γ. To examine whether IL-15 and IFN-γ have direct antiviral activity against HCV, Huh7.5 cells were treated with either IFN-γ or IL-15 prior to HCV infection. Our data demonstrate that IFN-γ and IL-15 block HCV replication in vitro. Additionally, we show that IL-15 and IFN-γ do not induce anti-HCV effects through the type I interferon signaling pathway or nitric oxide (NO) production. Instead, IL-15 and IFN-γ provide protection against HCV via the ERK pathway. Treatment of Huh7.5 cells with a MEK/ERK inhibitor abrogated the anti-HCV effects of IL-15 and IFN-γ and overexpression of ERK1 prevented HCV replication compared to control transfection. Our in vitro data support the hypothesis that early production of IL-15 and activation of NK cells in the liver lead to control of HCV replication.

Innate and Adaptive Immune Responses in Chronic HCV Infection

Hepatitis C virus (HCV) remains a public health problem of global importance, even in the era of potent directly-acting antiviral drugs. In this chapter, I discuss immune responses to acute and chronic HCV infection. The outcome of HCV infection is influenced by viral strategies that limit or delay the initiation of innate antiviral responses. This delay may enable HCV to establish widespread infection long before the host mounts effective T and B cell responses. HCV's genetic agility, resulting from its high rate of replication and its error prone replication mechanism, enables it to evade immune recognition. Adaptive immune responses fail to keep up with changing viral epitopes. Neutralizing antibody epitopes may be hidden by decoy structures, glycans, and lipoproteins. T cell responses fail due to changing epitope sequences and due to exhaustion, a phenomenon that may have evolved to limit immune-mediated pathology. Despite these difficulties, innate and adaptive immune mechanisms do impact HCV replication. Immune-mediated clearance of infection is possible, occurring in 20-50% of people who contract the disease. New developments raise hopes for effective immunological interventions to prevent or treat HCV infection.

The level of decoy epitope in PCV2 vaccine affects the neutralizing activity of sera in the immunized animals

Viral pathogens have evolved a wide range of tactics to evade host immune responses and thus propagate effectively. One efficient tactic is to divert host immune responses toward an immunodominant decoy epitope and to induce non-neutralizing antibodies toward this epitope. Therefore, it is expected that the amount of decoy epitope in a subunit vaccine can affect the level of neutralizing antibody in an immunized animal. In this study, we tested this hypothesis by generating an antibody specific to the decoy epitope on the capsid protein of porcine circovirus type 2 (PCV2). Using this antibody, we found that two commercial vaccines contained statistically different amounts of the decoy epitope. The vaccine with lower levels of decoy epitope induced a significantly higher level of neutralizing antibody after immunization. This antibody can be used as an analytical tool to monitor the quality of a vaccine from batch to batch.

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We generated a novel antibody specific to an immunodominant decoy epitope of PCV2.

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Using this novel antibody, we measured levels of decoy epitope in PCV2 vaccine.

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Decoy epitope in PCV2 vaccine affected the neutralizing antibody titer induction.

Immune Responses in the Liver

The liver is a key, frontline immune tissue. Ideally positioned to detect pathogens entering the body via the gut, the liver appears designed to detect, capture, and clear bacteria, viruses, and macromolecules. Containing the largest collection of phagocytic cells in the body, this organ is an important barrier between us and the outside world. Importantly, as portal blood also transports a large number of foreign but harmless molecules (e.g., food antigens), the liver's default immune status is anti-inflammatory or immunotolerant; however, under appropriate conditions, the liver is able to mount a rapid and robust immune response. This balance between immunity and tolerance is essential to liver function. Excessive inflammation in the absence of infection leads to sterile liver injury, tissue damage, and remodeling; insufficient immunity allows for chronic infection and cancer. Dynamic interactions between the numerous populations of immune cells in the liver are key to maintaining this balance and overall tissue health.

Interleukin-7 augments CD8+ T cells function and promotes viral clearance in chronic hepatitis C virus infection

Interleukin (IL)-7 is a potent proliferation, activation, and survival cytokine for CD8⁺ T cells to improve viral and tumor specific CD8⁺ T cell responses. However, the role of IL-7 in regulation of dysfunctional hepatitis C virus (HCV)-specific CD8⁺ T cells was not fully elucidated. Thus, a total of 53 patients with chronic hepatitis C and 24 healthy individuals were enrolled in the current study. Serum IL-7 and its receptor α chain CD127 expression was measured. The modulatory function of IL-7 to CD8⁺ T cells was investigated in both direct and indirect contact co-culture with HCVcc-infected Huh7.5 cells. Both serum IL-7 and CD127 expression on CD8⁺ T cells was significantly reduced in chronic HCV-infected patients, which was negatively correlated with HCV RNA. Stimulation of IL-7 promoted both cytotoxicity and cytokines (interferon-γ, tumor necrosis factor-α, and IL-2) production of CD8⁺ T cells from patients with chronic hepatitis C. Moreover, IL-7 increased proliferation of CD8⁺ T cells, while downregulated a critical repressor of cytokine signaling, suppressor of cytokine signaling 3 (SOCS3). The IL-7-mediated enhancement effects to CD8⁺ T cells were dependent on IL-6 production. The current data suggested that IL-7 induced both cytolytic and noncytolytic functions of CD8⁺ T cells probably via repression of SOCS3. IL-7 might be considered as one of the therapeutic candidates for treatment of chronic HCV infection.

Molecular characterization of hepatitis C virus in end-stage renal disease patients under hemodialysis

New direct-acting antiviral (DAA) agents are in development or already approved for the treatment of chronic hepatitis C virus (HCV) infection. The effectiveness of these drugs is related to the previous existence of resistant variants. Certain clinical conditions can allow changes in immunological characteristics of the host and even modify genetic features of viral populations. The aim of this study was to perform HCV molecular characterization from samples of end-stage renal disease patients on hemodialysis (ESRD-HD). Nested PCR and Sanger sequencing were used to obtain genetic information from the NS5B partial region of a cohort composed by 86 treatment-naïve patients. Genomic sequences from the Los Alamos databank were employed for comparative analysis. Bioinformatics methodologies such as phylogenetic reconstructions, informational entropy, and mutation analysis were used to analyze datasets separated by geographical location, HCV genotype, and renal function status. ESRD-HD patients presented HCV genotypes 1a (n = 18), 1b (n = 16), 2a (n = 2), 2b (n = 2), and 3a (n = 4). Control subjects were infected with genotypes 1a (n = 11), 1b (n = 21), 2b (n = 4), and 3a (n = 8). Dataset phylogenetic reconstruction separated HCV subtype 1a into two distinct clades. The entropy analysis from the ESRD-HD group revealed two amino acid positions related to an epitope for cytotoxic T lymphocytes and T helper cells. Genotype 1a was found to be more diverse than subtype 1b. Also, genotype 1a ERSD-HD patients had a higher mean of amino acids changes in comparison to control group patients. The identification of specific mutations on epitopes and high genetic diversity within the NS5B HCV partial protein in hemodialysis patients can relate to host immunological features and geographical distribution patterns. This genetic diversity can affect directly the new DAA's resistance mechanisms.

Hepatitis C virus mediated chronic inflammation and tumorigenesis in the humanised immune system and liver mouse model

Hepatitis C is a liver disease caused by infection of the Hepatitis C virus (HCV). Many individuals infected by the virus are unable to resolve the viral infection and develop chronic hepatitis, which can lead to formation of liver cirrhosis and cancer. To understand better how initial HCV infections progress to chronic liver diseases, we characterised the long term pathogenic effects of HCV infections with the use of a humanised mouse model (HIL mice) we have previously established. Although HCV RNA could be detected in infected mice up to 9 weeks post infection, HCV infected mice developed increased incidences of liver fibrosis, granulomatous inflammation and tumour formation in the form of hepatocellular adenomas or hepatocellular carcinomas by 28 weeks post infection compared to uninfected mice. We also demonstrated that chronic liver inflammation in HCV infected mice was mediated by the human immune system, particularly by monocytes/macrophages and T cells which exhibited exhaustion phenotypes. In conclusion, HIL mice can recapitulate some of the clinical symptoms such as chronic inflammation, immune cell exhaustion and tumorigenesis seen in HCV patients. Our findings also suggest that persistence of HCV-associated liver disease appear to require initial infections of HCV and immune responses but not long term HCV viraemia.

Seroprevalence of HCV and HIV infection among clients of the nation's longest-standing statewide syringe exchange program: A cross-sectional study of Community Health Outreach Work to Prevent AIDS (CHOW)

BACKGROUND

The Community Health Outreach Work to Prevent AIDS (CHOW) Project is the first and longest-standing statewide integrated and funded needle and syringe exchange program (SEP) in the US. Initiated on O'ahu in 1990, CHOW expanded statewide in 1993. The purpose of this study is to estimate the prevalences of hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infection, and to characterize risk behaviors associated with infection among clients of a long-standing SEP through the analysis of the 2012 CHOW evaluation data.

METHODS

A cross-sectional sample of 130 CHOW Project clients was selected from January 1, 2012 through December 31, 2012. Questionnaires captured self-reported exposure information. HIV and HCV antibodies were detected via rapid, point-of-care FDA-approved tests. Log-binomial regressions were used to estimate prevalence proportion ratios (PPRs). A piecewise linear log-binomial regression model containing 1 spline knot was used to fit the age-HCV relationship.

RESULTS

The estimated seroprevalence of HCV was 67.7% (95% confidence interval [CI]=59.5-75.8%). HIV seroprevalence was 2.3% (95% CI=0-4.9%). Anti-HCV prevalence demonstrated age-specific patterns, ranging from 31.6% through 90.9% in people who inject drugs (PWID) <30 to ≥60 years respectively. Age (continuous/year) prior to spline knot at 51.5 years (adjusted PPR [APPR]=1.03; 95% CI=1.02-1.05) and months exchanging syringes (quartiles) (APPR=1.92; 95% CI=1.3-3.29) were independently associated with anti-HCV prevalence.

CONCLUSION

In Hawai'i, HCV prevalence among PWID is hyperendemic demonstrating age- and SEP duration-specific trends. Relatively low HIV prevalence compared with HCV prevalence reflects differences in transmissibility of these 2 blood-borne pathogens and suggests much greater efficacy of SEP for HIV prevention.

Tumor Necrosis Factor Inhibits Spread of Hepatitis C Virus Among Liver Cells, Independent From Interferons

BACKGROUND & AIMS

Tumor necrosis factor (TNF) is an inflammatory cytokine expressed by human fetal liver cells (HFLCs) after infection with cell culture-derived hepatitis C virus (HCV). TNF has been reported to increase entry of HCV pseudoparticles into hepatoma cells and inhibit signaling by interferon alpha (IFNα), but have no effect on HCV-RNA replication. We investigated the effects of TNF on HCV infection of and spread among Huh-7 hepatoma cells and primary HFLCs.

METHODS

Human hepatoma (Huh-7 and Huh-7.5) and primary HFLCs were incubated with TNF and/or recombinant IFNA2A, IFNB, IFNL1, and IFNL2 before or during HCV infection. We used 2 fully infectious HCV chimeric viruses of genotype 2A in these studies: J6/JFH (clone 2) and Jc1(p7-nsGluc2A) (Jc1G), which encodes a secreted luciferase reporter. We measured HCV replication, entry, spread, production, and release in hepatoma cells and HFLCs.

RESULTS

TNF inhibited completion of the HCV infectious cycle in hepatoma cells and HFLCs in a dose-dependent and time-dependent manner. This inhibition required TNF binding to its receptor. Inhibition was independent of IFNα, IFNβ, IFNL1, IFNL2, or Janus kinase signaling via signal transducer and activator of transcription. TNF reduced production of infectious viral particles by Huh-7 and HFLC, and thereby reduced the number of infected cells and focus size. TNF had little effect on HCV replicons and increased entry of HCV pseudoparticles. When cells were incubated with TNF before infection, the subsequent antiviral effects of IFNs were increased.

CONCLUSIONS

In a cell culture system, we found TNF to have antiviral effects independently of, as well as in combination with, IFNs. TNF inhibits HCV infection despite increased HCV envelope glycoprotein-mediated infection of liver cells. These findings contradict those from other studies, which have reported that TNF blocks signal transduction in response to IFNs. The destructive inflammatory effects of TNF must be considered along with its antiviral effects.

MBL2 Genetic Variants in HCV Infection Susceptibility, Spontaneous Viral Clearance and Pegylated Interferon Plus Ribavirin Treatment Response

Hepatitis C is disease that damages the liver, and it is caused by the hepatitis C virus (HCV). The pathology became chronic in about 80% of the cases due to virus persistence in the host organism. The standard of care consists of pegylated interferon plus ribavirin; however, the treatment response is very variable and different host/viral factors may concur in the disease outcome. The mannose-binding protein C (MBL) is a component of the innate immune system, able to recognize HCV and consecutively activating the immune response. MBL is encoded by MBL2 gene, and polymorphisms, two in the promoter region (H/L and X/Y) and three in exon 1 (at codon 52, 54 and 57), have been described as functionally influencing protein expression. In this work, 203 Italian HCV patients and 61 healthy controls were enrolled and genotyped for the five MBL2 polymorphisms mentioned above to investigate their role in HCV infection susceptibility, spontaneous viral clearance and treatment response. MBL2 polymorphisms were not associated with HCV infection susceptibility and with spontaneous viral clearance, while MBL2 O allele, O/O genotype, HYO haplotype and DP combined genotype (all correlated with low or deficient MBL expression) were associated with sustained virological response. Moreover, a meta-analysis to assess the role of MBL2 polymorphisms in HCV infection susceptibility was also performed: YA haplotype could be associated with protection towards HCV infection.

Expression of scavenger receptor-AI promotes alternative activation of murine macrophages to limit hepatic inflammation and fibrosis

The liver maintains an immunologically tolerant environment as a result of continuous exposure to food and bacterial constituents from the digestive tract. Hepatotropic pathogens can take advantage of this niche and establish lifelong chronic infections causing hepatic fibrosis and hepatocellular carcinoma. Macrophages (Mϕ) play a critical role in regulation of immune responses to hepatic infection and regeneration of tissue. However, the factors crucial for Mϕ in limiting hepatic inflammation or resolving liver damage have not been fully understood. In this report, we demonstrate that expression of C-type lectin receptor scavenger receptor-AI (SR-AI) is crucial for promoting M2-like Mϕ activation and polarization during hepatic inflammation. Liver Mϕ uniquely up-regulated SR-AI during hepatotropic viral infection and displayed increased expression of alternative Mϕ activation markers, such as YM-1, arginase-1, and interleukin-10 by activation of mer receptor tyrosine kinase associated with inhibition of mammalian target of rapamycin. Expression of these molecules was reduced on Mϕ obtained from livers of infected mice deficient for the gene encoding SR-AI (msr1). Furthermore, in vitro studies using an SR-AI-deficient Mϕ cell line revealed impeded M2 polarization and decreased phagocytic capacity. Direct stimulation with virus was sufficient to activate M2 gene expression in the wild-type (WT) cell line, but not in the knockdown cell line. Importantly, tissue damage and fibrosis were exacerbated in SR-AI^-/- mice following hepatic infection and adoptive transfer of WT bone-marrow-derived Mϕ conferred protection against fibrosis in these mice.

CONCLUSION

SR-AI expression on liver Mϕ promotes recovery from infection-induced tissue damage by mediating a switch to a proresolving Mϕ polarization state. (Hepatology 2017;65:32-43).

High resolution sequencing of hepatitis C virus reveals limited intra-hepatic compartmentalization in end-stage liver disease

BACKGROUND & AIMS

The high replication and mutation rate of hepatitis C virus (HCV) results in a heterogeneous population of viral sequences in vivo. HCV replicates in the liver and infected hepatocytes occur as foci surrounded by uninfected cells that may promote compartmentalization of viral variants. Given recent reports showing interferon stimulated gene (ISG) expression in chronic hepatitis C, we hypothesized that local interferon responses may limit HCV replication and evolution.

METHODS

To investigate the spatial influence of liver architecture on viral replication we measured HCV RNA and ISG mRNA from each of the 8 Couinaud segments of the liver from 21 patients undergoing liver transplant.

RESULTS

HCV RNA and ISG mRNA levels were comparable across all sites from an individual liver but showed up to 500-fold difference between patients. Importantly, there was no association between ISG and HCV RNA expression across all sites in the liver or plasma. Deep sequencing of HCV RNA isolated from the 8 hepatic sites from two subjects showed a similar distribution of viral quasispecies across the liver and uniform sequence diversity. Single genome amplification of HCV E1E2-envelope clones from 6 selected patients at 2 hepatic sites supported these data and showed no evidence for HCV compartmentalization.

CONCLUSIONS

We found no differences between the hepatic and plasma viral quasispecies in all patients sampled. We conclude that in end-stage liver disease HCV RNA levels and the genetic pool of HCV envelope sequences are indistinguishable between distant sites in the liver and plasma, arguing against viral compartmentalization.

LAY SUMMARY

HCV is an RNA virus that exists as a quasispecies of closely related genomes that are under continuous selection by host innate and adaptive immune responses and antiviral drug therapy. The primary site of HCV replication is the liver and yet our understanding of the spatial distribution of viral variants within the liver is limited. High resolution sequencing of HCV and monitoring of innate immune responses at multiple sites across the liver identified a uniform pattern of diversity and argues against viral compartmentalization.

Prevalence of IFNL3 gene polymorphism among blood donors and its relation to genomic profile of ancestry in Brazil

The recent development of interferon-free regimens based on direct-acting antivirals for the treatment of chronic hepatitis C virus infection has benefited many but not all patients. Some patients still experience treatment failure, possibly attributed to unknown host and viral factors, such as IFNL3 gene polymorphism. The present study assessed the prevalence of rs12979860-CC, rs12979860-CT, and rs12979860-TT genotypes of the IFNL3 gene, and its relationship with ancestry informative markers in 949 adult Brazilian healthy blood donors. Race was analyzed using ancestry informative markers as a surrogate for ancestry. IFNL3 gene was genotyped using the ABI TaqMan single nucleotide polymorphisms genotyping assays. The overall frequency of rs12979860-CC genotype was 36.9%. The contribution of African ancestry was significantly higher among donors from the northeast region in relation to southeast donors, whereas the influence of European ancestry was significantly higher in southeast donors. Donors with rs12979860-CC and rs12979860-CT genotypes had similar ancestry background. The contribution of African ancestry was higher among rs12979860-TT genotype donors in comparison to both rs12979860-CC and rs12979860-CT genotypes. The prevalence of rs12979860-CC genotype is similar to that found in the US, despite the Brazilian ancestry informative markers admixture. However, in terms of ancestry, rs12979860-CT genotype was much closer to rs12979860-CC individuals than to rs12979860-TT.

Hepatitis C virus: life cycle in cells, infection and host response, and analysis of molecular markers influencing the outcome of infection and response to therapy

Hepatitis C virus (HCV) is a major global health burden accounting for around 170 million chronic infections worldwide. Since its discovery, which dates back to about 30 years ago, many details of the viral genome organization and the astonishing genetic diversity have been unveiled but, owing to the difficulty of culturing HCV in vitro and obtaining fully susceptible yet immunocompetent in vivo models, we are still a long way from the full comprehension of viral life cycle, host cell pathways facilitating or counteracting infection, pathogenetic mechanisms in vivo, and host defences. Here, we illustrate the viral life cycle into cells, describe the interplay between immune and genetic host factors shaping the course of infection, and provide details of the molecular approaches currently used to genotype, monitor replication in vivo, and study the emergence of drug-resistant viral variants.

Hepatic fibrosis and immune phenotype vary by HCV viremia in HCV/HIV co-infected subjects: A Women's interagency HIV study

HCV and HIV independently lead to immune dysregulation. The mechanisms leading to advanced liver disease progression in HCV/HIV coinfected subjects remain unclear.In this cross-sectional study, we assessed the association of HCV viremia, liver fibrosis, and immune response patterns in well-characterized HIV phenotypes: Elite controllers (Elites), HIV controlled (ARTc), and HIV uncontrolled (ARTuc) matched by age and race. Groups were stratified by HCV RNA status. Regulatory T-cell frequencies, T-cell activation (HLADR+CD38+), apoptosis (Caspase-3+), and intracellular cytokines (interferon-γ, IL-2, IL-17) were assessed using multiparametric flow-cytometry. Liver fibrosis was scored by AST to platelet ratio index (APRI).We found liver fibrosis (APRI) was 50% lower in Elites and ARTc compared to ARTuc. Higher liver fibrosis was associated with significantly low CD4+ T cell counts (P < 0.001, coefficient r = -0.463). Immune activation varied by HIV phenotype but was not modified by HCV viremia. HCV viremia was associated with elevated CD8 T-cell Caspase-3 in Elites, ARTuc, and HIV- except ARTc. CD8 T-cell Caspase-3 levels were significantly higher in HCV RNA+ Elites (P = 0.04) and ARTuc (P = 0.001) and HIV- groups (P = 0.02) than ARTc. Importantly, ARTuc HCV RNA+ had significantly higher CD4 T-cell interleukin-17 levels than ARTuc HCV RNA- (P = 0.005).HIV control was associated with lower liver fibrosis in HCV/HIV co-infected women. HCV viremia is associated with an inflammatory CD4 TH-17 phenotype in absence of HIV control and higher frequency of pro-apoptosis CD8 T-cells critical to avert progression of HIV and HCV disease that is attenuated in ART controllers. Elite controllers with HCV viremia are more prone to CD8 T-cell apoptosis than ART controllers, which could have negative consequences over time, highlighting the importance of ART control in HCV/HIV coinfected individuals.

CD209 promoter polymorphisms associate with HCV infection and pegylated-interferon plus ribavirin treatment response

Hepatitis C is a severe liver disease caused by hepatitis C virus that could persist in the host causing progression towards chronic disease in about 80% of the cases. Pegylated-interferon plus ribavirin was the gold standard therapy, however treatment's response was quite variable among individuals and different host/viral factors may play a role in disease outcome. The cluster of differentiation 209 (CD209 antigen) is a component of the innate immune system able to recognize HCV and consequently activating the immune response. We enrolled 203 Italian HCV infected patients and 220 healthy controls investigating if five promoter polymorphisms within CD209 gene (encoding for CD209 antigen) correlated with HCV infection susceptibility, spontaneous viral clearance and interferon treatment response. CD209 -939G>A and -871A>G polymorphisms associated with HCV infection susceptibility, while, CD209 -871A>G and -336A>G polymorphisms associated with response to treatment. In conclusion, CD209 polymorphisms could play a role in the susceptibility to HCV infection as well as interferon treatment response in our study population from North-East of Italy.

Status of hepatitis C virus vaccination: Recent update

Hepatitis C virus (HCV) infection is still a major public health problem worldwide since its first identification in 1989. At the start, HCV infection was post-transfusion viral infection, particularly in developing countries. Recently, due to iv drug abuse, HCV infection became number one health problem in well-developed countries as well. Following acute HCV infection, the innate immune response is triggered in the form of activated coordinated interaction of NK cells, dendritic cells and interferon α. The acquired immune response is then developed in the form of the antibody-mediated immune response (ABIR) and the cell-mediated immune response (CMIR). Both are responsible for clearance of HCV infection in about 15% of infected patients. However, HCV has several mechanisms to evade these antivirus immune reactions. The current review gives an overview of HCV structure, immune response and viral evasion mechanisms. It also evaluates the available preventive and therapeutic vaccines that induce innate, ABIR, CMIR. Moreover, this review highlights the progress in recent HCV vaccination studies either in preclinical or clinical phases. The unsatisfactory identification of HCV infection by the current screening system and the limitations of currently available treatments, including the ineligibility of some chronic HCV patients to such antiviral agents, mandate the development of an effective HCV vaccine.

Lymphocyte activation gene 3 negatively regulates the function of intrahepatic hepatitis C virus-specific CD8+ T cells

BACKGROUND AND AIM

Chronic hepatitis C (CHC) in humans caused by persistent hepatitis C virus (HCV) infection is a global public health problem. The functional exhaustion of HCV-specific CD8(+) T cells regulated by several inhibitory receptors has been shown to contribute to chronic HCV infection. Lymphocyte activation gene 3 (LAG-3), which is an inhibitory receptor, plays an important role in several chronic viral infections. However, its effect on the function of HCV-specific CD8(+) T cells is unclear.

METHODS

The expression of LAG-3 on the CD8(+) T cells in intrahepatic and peripheral lymphocytes from 17 CHC patients and 15 HCV-negative patients was analyzed by flow cytometry. The LAG-3 expression in CD8(+) T cells was downregulated or upregulated by lentivirus LAG-3 shRNA or lentivirus overexpressing LAG-3. After HCV peptide stimulation, flow cytometry was used to detect cell proliferation and cytokine (γ-interferon [IFN-γ], tumor necrosis factor-α [TNF-α], granzyme B, and perforin) production of CD8(+) T cells. Cytotoxicity functions of HCV-specific CD8(+) T cells were measured using a (51) Cr release assay.

RESULTS

The frequency of LAG-3-positive intrahepatic and peripheral CD8(+) T cells was higher in CHC patients, compared with HCV-negative patients. The cell proliferation, cytokine (IFN-γ, TNF-α, granzyme B, and perforin) expression and cytotoxicity function of HCV-specific CD8(+) T cells in CHC patients were increased by the knocking down and blockade of LAG-3. In the LAG-3 overexpressed CD8(+) T cells, cell proliferation, cytokine (IFN-γ, TNF-α, granzyme B, and perforin) expression, and cytotoxicity function were inhibited, while the LAG-3 blocking antibody reversed the inhibition.

CONCLUSION

LAG-3 negatively regulated the function of HCV-specific CD8(+) T cells in CHC patients.

The Divergent CD8+ T Cell Adjuvant Properties of LT-IIb and LT-IIc, Two Type II Heat-Labile Enterotoxins, Are Conferred by Their Ganglioside-Binding B Subunits

Poor immune responses elicited by vaccine antigens can be enhanced by the use of appropriate adjuvants. Type II heat-labile enterotoxins (HLT) produced by Escherichia coli are extremely potent adjuvants that augment both humoral and cellular immunity to co-administered antigens. Recent findings demonstrate that LT-IIb and LT-IIc, two type II HLT adjuvants, exhibit potent, yet distinguishable CD8⁺ T cell adjuvant properties. While LT-IIc elicits a robust and rapid response at one week after administration, LT-IIb engenders a more gradual and slower expansion of antigen-specific CD8⁺ T cells that correlates with improved immunity. The variations in immune effects elicited by the HLT adjuvants have been generally attributed to their highly divergent B subunits that mediate binding to various gangliosides on cell surfaces. Yet, HLT adjuvants with point mutations in the B subunit that significantly alter ganglioside binding retain similar adjuvant functions. Therefore, the contribution of the B subunits to adjuvanticity remains unclear. To investigate the influence of the B subunits on the enhancement of immune responses by LT-IIb and LT-IIc, chimeric HLT were engineered in which the B subunits of the two adjuvants were exchanged. Comparing the immune potentiating characteristics of both native and chimeric HLT adjuvants, it was found that not all the adjuvant characteristics of the HLT adjuvants were modulated by the respective B subunits. Specifically, the differences in the CD8⁺ T cell kinetics and protective responses elicited by LT-IIb and LT-IIc did indeed followed their respective B subunits. However, induction of IL-1 from macrophages and the capacity to intoxicate cells in a mouse Y1 adrenal cell bioassay did not correlate with the B subunits. Therefore, it is likely that additional factors other than the B subunits contribute to the effects elicited by the HLT adjuvants.

Therapeutic cancer vaccines

The clinical benefit of therapeutic cancer vaccines has been established. Whereas regression of lesions was shown for premalignant lesions caused by HPV, clinical benefit in cancer patients was mostly noted as prolonged survival. Suboptimal vaccine design and an immunosuppressive cancer microenvironment are the root causes of the lack of cancer eradication. Effective cancer vaccines deliver concentrated antigen to both HLA class I and II molecules of DCs, promoting both CD4 and CD8 T cell responses. Optimal vaccine platforms include DNA and RNA vaccines and synthetic long peptides. Antigens of choice include mutant sequences, selected cancer testis antigens, and viral antigens. Drugs or physical treatments can mitigate the immunosuppressive cancer microenvironment and include chemotherapeutics, radiation, indoleamine 2,3-dioxygenase (IDO) inhibitors, inhibitors of T cell checkpoints, agonists of selected TNF receptor family members, and inhibitors of undesirable cytokines. The specificity of therapeutic vaccination combined with such immunomodulation offers an attractive avenue for the development of future cancer therapies.

Control of oxidative stress in hepatocellular carcinoma: Helpful or harmful?

Oxidative stress is becoming recognized as a key factor in the progression of chronic liver disease (CLD) and hepatocarcinogenesis. The metabolically important liver is a major reservoir of mitochondria that serve as sources of reactive oxygen species, which are apparently responsible for the initiation of necroinflammation. As a result, CLD could be a major inducer of oxidative stress. Chronic hepatitis C is a powerful generator of oxidative stress, causing a high rate of hepatocarcinogenesis among patients with cirrhosis. Non-alcoholic steatohepatitis is also associated with oxidative stress although its hepatocarcinogenic potential is lower than that of chronic hepatitis C. Analyses of serum markers and histological findings have shown that hepatocellular carcinoma correlates with oxidative stress and experimental data indicate that oxidative stress increases the likelihood of developing hepatocarcinogenesis. However, the results of antioxidant therapy have not been favorable. Physiological oxidative stress is a necessary biological response, and thus adequate control of oxidative stress and a balance between oxidative and anti-oxidative responses is important. Several agents including metformin and L-carnitine can reportedly control mechanistic oxidative stress. This study reviews the importance of oxidative stress in hepatocarcinogenesis and of control strategies for the optimal survival of patients with CLD and hepatocellular carcinoma.

The Humoral Immune Response to HCV: Understanding is Key to Vaccine Development

Hepatitis C virus (HCV) remains a global problem, despite advances in treatment. The low cost and high benefit of vaccines have made them the backbone of modern public health strategies, and the fight against HCV will not be won without an effective vaccine. Achievement of this goal will benefit from a robust understanding of virus-host interactions and protective immunity in HCV infection. In this review, we summarize recent findings on HCV-specific antibody responses associated with chronic and spontaneously resolving human infection. In addition, we discuss specific epitopes within HCV's envelope glycoproteins that are targeted by neutralizing antibodies. Understanding what prompts or prevents a successful immune response leading to viral clearance or persistence is essential to designing a successful vaccine.

Contradictory immune response in post liver transplantation hepatitis B and C

Hepatitis B and C often progress to decompensated liver cirrhosis requiring orthotopic liver transplantation (OLT). After OLT, hepatitis B recurrence is clinically controlled with a combination of hepatitis B immunoglobulin (HBIG) and nucleos(t)ide analogues. Another approach is to induce self-producing anti-hepatitis B virus (HBV) antibodies using a HBV envelope antigen vaccine. Patients who had not been HBV carriers such as acutely infected liver failure or who received liver from HBV self-limited donor are good candidate. For chronic HBV carrier patients, a successful response can only be achieved in selected patients such as those treated with experimentally reduced immunosuppression protocols or received an anti-HBV adaptive memory carrying donor liver. Hepatitis C virus (HCV) reinfects transplanted livers at a rate of >90%. HCV reinfected patients show different severities of hepatitis, from mild and slowly progressing to severe and rapidly progressing, possibly resulting from different adaptive immune responses. More than half the patients require interferon treatment, although the success rate is low and carries risks for leukocytopenia and rejection. Managing the immune response has an important role in controlling recurrent hepatitis C. This study aimed to review the adaptive immune response in post-OLT hepatitis B and C.