Host-virus interactions in hepatitis B and hepatitis C infection

Introduction of direct-acting antiviral agents alters frequencies of anti-GPIIb/IIIa antibody-producing B cells in chronic hepatitis C patients with thrombocytopenia

The pathogenesis of thrombocytopenia in chronic hepatitis C (CHC) conceivably involves autoimmunity; however, the dynamics of autoantibodies and other autoimmune mechanisms remain unclear. In this study, we examined the changes in the frequency of anti-glycoprotein (GP) IIb/IIIa antibody-producing B cells and the levels of plasma B-cell-activating factor (BAFF), a proliferation-inducing ligand (APRIL), and interleukin (IL)-21 following treatment of CHC with direct-acting antiviral agents (DAA). We recruited 28 patients with CHC who underwent treatment with DAA for 8-12 weeks and subsequently tested negative for serum hepatitis C virus RNA. Thirty healthy controls were recruited for comparison. Platelet counts increased significantly (p = .016), and the frequency of anti-GPIIb/IIIa antibody-producing B cells decreased significantly (p = .002) in CHC patients with thrombocytopenia at the end of treatment (EOT) than before DAA treatment (baseline). However, these changes were not observed in CHC patients without thrombocytopenia. Plasma BAFF levels in CHC patients with thrombocytopenia significantly decreased from baseline to EOT (p = .002). Anti-GPIIb/IIIa antibody-producing B cells were positively correlated with plasma BAFF levels in these patients (r = 0.669, p = .039). These results suggest that DAA treatment suppresses the autoimmune response against platelets and improves thrombocytopenia.

CuMV VLPs Containing the RBM from SARS-CoV-2 Spike Protein Drive Dendritic Cell Activation and Th1 Polarization

Dendritic cells (DCs) are the most specialized and proficient antigen-presenting cells. They bridge innate and adaptive immunity and display a powerful capacity to prime antigen-specific T cells. The interaction of DCs with the receptor-binding domain of the spike (S) protein from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a pivotal step to induce effective immunity against the S protein-based vaccination protocols, as well as the SARS-CoV-2 virus. Herein, we describe the cellular and molecular events triggered by virus-like particles (VLPs) containing the receptor-binding motif from the SARS-CoV-2 spike protein in human monocyte-derived dendritic cells, or, as controls, in the presence of the Toll-like receptors (TLR)3 and TLR7/8 agonists, comprehending the events of dendritic cell maturation and their crosstalk with T cells. The results demonstrated that VLPs boosted the expression of major histocompatibility complex molecules and co-stimulatory receptors of DCs, indicating their maturation. Furthermore, DCs’ interaction with VLPs promoted the activation of the NF-kB pathway, a very important intracellular signalling pathway responsible for triggering the expression and secretion of proinflammatory cytokines. Additionally, co-culture of DCs with T cells triggered CD4+ (mainly CD4+Tbet+) and CD8+ T cell proliferation. Our results suggested that VLPs increase cellular immunity, involving DC maturation and T cell polarization towards a type 1 T cells profile. By providing deeper insight into the mechanisms of activation and regulation of the immune system by DCs, these findings will enable the design of effective vaccines against SARS-CoV-2.

Change of Cytokines in Chronic Hepatitis B Patients and HBeAg are Positively Correlated with HBV RNA, Based on Real-world Study

BACKGROUND AND AIMS

The natural course of chronic hepatitis B virus (HBV) infection is widely studied; however, follow-up studies of the same patients are scanty. Here, we studied the dynamic changes of serum HBV RNA and cytokines in hepatitis B virus e antigen (HBeAg)-positive patients treated with entecavir (ETV) to explore the relationship between the HBV serum viral nucleic acids and host immunity.

METHODS

Thirty-three chronic hepatitis B patients who are HBeAg-positive, with high virus load (HBV DNA >20,000 IU/mL), and received standard nucleos(t)ide analogue (NA) antiviral therapy (ETV) for more than 48 weeks were included. The serum levels of HBV nucleic acids and selected cytokines were measured at 0, 12, 24, and 48 weeks respectively.

RESULTS

Serum HBV RNA could still be detected while serum HBV DNA had fallen below the detection limit in patients treated with ETV. There was a strong positive correlation between HBV RNA and HBeAg, with a concomitant decrease in the secretion of cytokines from type 1 helper T (Th1)/type 2 helper T (Th2)/interleukin (IL)-17 producing T (Th17) cells. IL-4 and IL-10 were the main cytokines negatively associated with serum HBV RNA.

CONCLUSIONS

HBeAg can be used to reflect the load of HBV RNA indirectly, because serum HBV RNA has not been widely used in clinical practice. Meanwhile, serum IL-4 and IL-10 might be explored in combination with HBV RNA in guiding future clinical antiviral therapy.

Immune therapies against chronic hepatitis B

Patients with chronic hepatitis B (CHB) represent a living and permanent reservoir of hepatitis B virus (HBV). Millions of these CHB patients will eventually develop complications such as liver cirrhosis, hepatic failure, and hepatocellular carcinoma if they are not treated properly. Accordingly, several antiviral drugs have been developed for the treatment of CHB, but these drugs can neither eradicate all forms of HBV nor contain the progression of complications in most patients with CHB. Thus, the development of new and novel therapeutics for CHB remains a pressing need. The molecular and cellular mechanisms underlying the pathogenesis of CHB indicate that immune dysregulations may be responsible for HBV persistence and progressive liver damage in CHB. This provided the scientific and ethical basis for the immune therapy of CHB patients. Around 30 years have passed since the initiation of immune therapies for CHB in the early 1990s, and hundreds of clinical trials have been accomplished to substantiate this immune treatment. Despite these approaches, an acceptable regimen of immune therapy is yet to be realized. However, most immune therapeutic agents are safe for human usage, and many of these protocols have inspired considerable optimism. In this review, the pros and cons of different immune therapies, observed in patients with CHB during the last 30 years, will be discussed to derive insights into the development of an evidence-based, effective, and patient-friendly regimen of immune therapy for the treatment of CHB.

Emerging Roles on Immunological Effect of Indoleamine 2,3-Dioxygenase in Liver Injuries

Indoleamine 2,3-dioxygenase (IDO) is one of the initial rate-limiting enzymes of the kynurenine pathway (KP), which causes immune suppression and induction of T cell anergy. It is associated with the imbalance of immune homeostasis in numerous diseases including cancer, chronic viral infection, allergy, and autoimmune diseases. Recently, IDO has extended its role to liver field. In this review, we summarize the dysregulation and potentials of IDO in the emerging field of liver injuries, as well as current challenges for IDO targets. In particular, we discuss unexpected conclusions against previous work published. IDO is induced by pro-inflammatory cytokines in liver dysfunction and exerts an immunosuppressive effect, whereas the improvement of liver injury may require consideration of multiple factors besides IDO.

Peripheral Immune Cells Exhaustion and Functional Impairment in Patients With Chronic Hepatitis B

After infection of hepatitis B virus (HBV), the virus induces a variety of immune disorders in the host, leading to immune escape and, finally, the chronicity of the disease. This study investigated immune cell defects and functional impairment in patients with chronic hepatitis B (CHB). We analyzed the percentage, function, and phenotypes of various immune cell subpopulations in the peripheral blood along with the concentrations of cytokines in the plasma. We compared the results between patients with CHB and healthy individuals. It was found that in patients with CHB, the cell function was impaired and, there was increased expression of inhibitory receptors, such as NKG2A and PD-1 in both NK and T cells. The impairment of function was mainly in cytokine secretion, and the cytotoxicity was not significantly diminished. We also found that the proportion of dendritic cells (DC) decreased and regulatory B cells (Breg) increased in CHB. In addition, the Breg cells were negatively correlated with T cell cytokine and positively correlated with ALT and HBV viral load. Taken together, various disorders and functional impairments were found in the immune cells of peripheral blood in CHB patients, especially NK and T cells. These cells showed exhaustion and the increase of regulatory B cells may be one of the reasons for this phenomenon.

Review of Lambda Interferons in Hepatitis B Virus Infection: Outcomes and Therapeutic Strategies

Hepatitis B virus (HBV) chronically infects over 250 million people worldwide and causes nearly 1 million deaths per year due to cirrhosis and liver cancer. Approved treatments for chronic infection include injectable type-I interferons and nucleos(t)ide reverse transcriptase inhibitors. A small minority of patients achieve seroclearance after treatment with type-I interferons, defined as sustained absence of detectable HBV DNA and surface antigen (HBsAg) antigenemia. However, type-I interferons cause significant side effects, are costly, must be administered for months, and most patients have viral rebound or non-response. Nucleos(t)ide reverse transcriptase inhibitors reduce HBV viral load and improve liver-related outcomes, but do not lower HBsAg levels or impart seroclearance. Thus, new therapeutics are urgently needed. Lambda interferons (IFNLs) have been tested as an alternative strategy to stimulate host antiviral pathways to treat HBV infection. IFNLs comprise an evolutionarily conserved innate immune pathway and have cell-type specific activity on hepatocytes, other epithelial cells found at mucosal surfaces, and some immune cells due to restricted cellular expression of the IFNL receptor. This article will review work that examined expression of IFNLs during acute and chronic HBV infection, the impact of IFNLs on HBV replication in vitro and in vivo, the association of polymorphisms in IFNL genes with clinical outcomes, and the therapeutic evaluation of IFNLs for the treatment of chronic HBV infection.

Relationships between IL-1β, TNF-α genetic polymorphisms and HBV infection: A meta-analytical study

BACKGROUND

IL-1β and TNF-α have been demonstrated as pro-inflammatory cytokines to participate in the innate immune response and suppression of HBV infection. However, the exact relationship between IL-1β, TNF-α gene polymorphisms and HBV infection remains unknown. Our study aims to assess the associations between IL-1β, TNF-α gene polymorphisms and HBV infection.

METHODS

A systematic literature search of PubMed and Embase databases was conducted through February 2020, and studies that were included in the present meta-analysis should fulfil the following conditions: (1) case-control studies focusing on the associations between IL-1β, TNF-α polymorphisms and HBV infection; (2) patients in the case group should be tested positive for the HBsAg and/or HBV-DNA without liver cirrhosis or hepatocellular carcinoma; (3) the control group including healthy population or HBV spontaneous clearance population; (4) odds ratios (ORs) and their 95% confidence intervals (CIs) could be calculated based on the allele and genotype frequencies provided in articles. The quality of included studies was assessed according to the Newcastle-Ottawa scale (NOS) assessment system. Pooled ORs and 95% CIs were used to analyze the strength of associations. Subgroup analysis was performed according to ethnicity and control type.

RESULTS

In the present meta-analysis, 49 articles including 10,218 cases and 9,557 controls were enrolled and seven polymorphisms (IL-1β rs16944, rs1143634, TNF-α rs1799724, rs1799964, rs1800629, rs1800630, rs361525) were studied. In overall meta-analysis, significant associations were found in IL-1β rs1143634, TNF-α rs1799724 and TNF-α rs1799964. For subgroup analysis under ethnicity, TNF-α rs1799724 and rs1800630 were markedly related to HBV infection in both Asian and Caucasian populations. In terms of control type subgroup, TNF-α rs1799724, rs1799964, rs1800630 were significantly associated with HBV persistence in HBV spontaneous clearance group.

CONCLUSION

In the present study, we identified that three polymorphisms (IL-1β rs1143634, TNF-α rs1799724, rs1799964) might serve as potential genetic biomarkers in HBV infection.

Clinical and histopathological changes in different KIR gene profiles in chronic HCV Romanian patients

Hepatitis C virus (HCV)-infected individuals may have a faster progression of liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC) development when influenced by host, viral and environmental factors. Hepatitis C virus disease progression is also associated with genetic variants of specific killer cell immunoglobulin-like receptors (KIRs) and genes of the major histocompatibility complex (MHC). The aim of the present study was to correlate clinical, virologic and biochemical parameters and to evaluate the possible influence of KIR genes and their HLA class I ligands in patients infected with hepatitis C virus. The present study analysed a total of 127 chronic HCV-infected patients for various biochemical and genetics factors that can influence disease progression and prognosis. Liver function parameters such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), direct bilirubin (DB), alpha-fetoprotein (AFP), HCV RNA levels and fibrosis indices were analysed using well-established biochemical methods. At the same time, KIR and HLA genotyping was performed using a polymerase chain reaction sequence-specific primer technique. Analysis of HLA class I and HLA ligands revealed that HLA-C*12:02 and HLA-A3 and HLA-A11 were positively associated with the F3-F4 fibrosis group (p = .026; OR = 8.717, CI = 1.040-73.077; respectively, p = .047; OR = 2.187; 95% CI = 1.066-4.486). KIR2DL2-positive patients had high median levels of AST after treatment and direct bilirubin levels when compared to KIR2DL2-negative patients (p = .013, respectively, p = .028). KIR2DL2/KIR2DL2-C1C1 genotype was associated with increased AST, ALT and GGT levels. A higher GGT level was also observed in KIR2DS2-C1-positive patients when compared to KIR2DS2-C1-negative patients. The present research demonstrates several links between specific clinical, virologic and biochemical parameters and the expression of KIR genes and their HLA ligands in HCV-infected patients. These connections should be taken into account when considering disease development and treatment.

Potential Drug Targets Against Hepatitis B Virus Based on Both Virus and Host Factors

BACKGROUND

Hepatitis B is a very harmful and epidemic disease caused by hepatitis B virus (HBV). Although an effective anti-HBV vaccine is available, chronic infection poses still a huge health burden in the whole world. The present anti-HBV drugs including nucleoside analogues and interferonalpha have their limitations without exception. There is no effective drug and therapeutic method that can really and truly cure hepatitis B so far. The variability of HBV genome results in that a significant number of patients develop drug resistance during the long-term use of anti-HBV drugs. Hence, it is urgently needed to discover novel targets and develop new drugs against hepatitis B.

OBJECTIVE

The review aims to provide the theory support for designing of the anti-HBV innovative drugs by offering a summary of the current situation of antiviral potential targets.

RESULTS AND CONCLUSION

Since HBV is obligate intracellular parasite, and as such it depends on host cellular components and functions to replicate itself. The targeting both virus and host might be a novel therapeutic option for hepatitis B. Accordingly, we analyse the advances in the study of the potential drug targets for anti-HBV infection, focusing on targeting virus genome, on targeting host cellular functions and on targeting virus-host proteins interactions, respectively. Meanwhile, the immune targets against chronic hepatitis B are also emphasized. In short, the review provides a summary of antiviral therapeutic strategies to target virus factors, host factors and immune factors for future designing of the innovative drug against HBV infection.

Association among cytokine profiles of innate and adaptive immune responses and clinical-virological features in untreated patients with chronic hepatitis B

Background

Complete clearance of intracellular viruses depends on effector cells of innate and adaptive immune systems. This study aimed to identify the relationships among antiviral cytokines produced by natural killer (NK) and T cells and clinical-virological characteristics in untreated chronic hepatitis B (CHB) patients.

Methods

We measured antiviral cytokines interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and interleukin-2 (IL-2) produced by T, NK and natural killer T (NKT) cells, respectively, in a cohort with chronic hepatitis B virus (HBV) infection (CHB). We also correlated these cytokines with clinical-virological characteristics using a linear regression model.

Results

levels of IFN-γ⁺ and TNF-α⁺ CD4⁺ and CD8⁺ T cells were significantly higher in immune active (IA) phase than in other phases. Immune tolerant (IT) patients showed the lowest expression of IFN-γ by NK and NKT cells, and TNF-α by NK cells. IFN-γ⁺, TNF-α⁺ and IL-2⁺ CD4⁺ and CD8⁺ T cells frequencies were similar between IA and gray zone (GZ) phases. Principal component analysis based on cytokines confirmed that most IT patients significantly differed from inactive carriers (IC) and IA patients, while GZ patients were widely scattered. Multivariate analysis showed both T and NK cells producing IFN-γ and TNF-α, but not IL-2, had significant association with serum alanine aminotransferase (ALT). Moreover, IFN-γ⁺ NKT cells were associated with HBV DNA, while IFN-γ⁺ CD4⁺ and CD8⁺ T cells were correlated with age.

Conclusion

HBV clinical phases are characterized by distinct cytokine signatures, which showed relationship to viral features in these untreated CHB patients.

Increase in liver γδ T cells with concurrent augmentation of IFN-β production during the early stages of a mouse model of acute experimental hepatitis B virus infection

The role of γδ T cells in acute hepatitis B virus (HBV) infection remains unclear. For the present study, a mouse model of acute HBV infection was constructed using hydrodynamic injection-based transfection of an HBV DNA plasmid (pHBV). Subsequent changes in the percentages of γδ T cells, expression of activation molecules (CD25 and CD69) and the production of the inflammatory cytokines interferon (IFN)-γ and tumor necrosis factor-α (TNF-α) by liver γδ T cells were investigated using fluorescence-activated cell sorting (FACS). Additionally, the immune responses in the mouse liver were evaluated dynamically by measuring cytokine mRNA expression (IFN-α, IFN-β, IFN-γ or TNF-α) using reverse transcription-quantitative PCR, and other populations of immune cells, including CD4⁺T, CD8⁺T, natural killer (NK) or natural killer T (NKT) cells, using FACS. On day 1 following acute HBV infection, the percentage of liver γδ T cells was significantly increased along with the high expression of HBV markers. Additionally, liver γδ T cells displayed peak expression of the activation marker CD69 and peak IFN-γ production within this timeframe. IFN-β mRNA expression and the percentage of NK cells were elevated significantly on day 1 in liver tissues. However, there were no significant changes in the spleen or peripheral γδ T cells. Therefore, these data suggested that during the early stages of acute HBV infection, significantly increased numbers of liver γδ T cells may be involved in the enhanced immune response to the increased expression of HBV markers in the liver.

Immunopathogenesis of Liver Injury During Hepatitis C Virus Infection

The present report describes current concepts about the mechanism of liver cell injury caused by host immune response against hepatitis C virus (HCV) infection in human beings. This report is based on the observations from experimental studies and follow-up actions on human liver diseases. The results from different investigations suggest that liver injury depends on the presentation of viral antigen and the level of host immune response raised against HCV-related peptides. Both innate and adaptive immunity are triggered to counter the viral onset. During development of host immunity, the cell-mediated immune response involving CD4⁺ Th1 cells and CD8⁺ cytotoxic T-lymphocyte (CTL) cells were found to play a major role in causing liver damage. The hepatic Innate lymphoid cells (ILCs) subsets are involved in the immune regulation of different liver diseases: viral hepatitis, mechanical liver injury, and fibrosis. Humoral immunity and natural killer (NK) cell action also contributed in liver cell injury by antibody-dependent cellular cytotoxicity (ADCC). In fact, immunopathogenesis of HCV infection is a complex phenomenon where regulation of immune response at several steps decides the possibility of viral elimination or persistence. Regulation of immune response was noted starting from viral-host interaction to immune reaction cascade engaged in cell damage. The activation or suppression of interferon-stimulated genes, NK cell action, CTL inducement by regulatory T cells (Treg), B cell proliferation, and so on was demonstrated during HCV infection. Involvement of HLA in antigen presentation, as well as types of viral genotypes, also influenced host immune response against HCV peptides. The combined effect of all these effector mechanisms ultimately decides the progression of viral onset to acute or chronic infection. In conclusion, immunopathogenesis of liver injury after HCV infection may be ascribed mainly to host immune response. Second, it is cell-mediated immunity that plays a predominant role in liver cell damage.

Pre-existing mutations related to tenofovir in chronic hepatitis B patients with long-term nucleos(t)ide analogue drugs treatment by ultra-deep pyrosequencing

Aims

The dynamics of resistance-associated mutations under combination therapy were explored.

Methods

A total of 46 patients were classified into adefovir (n=14) and entecavir (n=32) groups. In the adefovir (ADV) group, six patients receiving combined therapy were DNA-positive after more than 3 years of therapy. Ultra-deep pyrosequencing was used to analyze the dynamics of multi-drugs resistance mutations.

Results

At baseline, all 46 treatment-naïve patients harbored rtA181V/T substitutions (1.2%-4.6%) and rtN236T substitutions (1.6%-6.1%). In the ADV group, eight patients with long-term treatment were consecutively HBV DNA-positive for more than 3 years. During treatment, the rtA181T resistance-associated site appeared with increasing frequency in six of eight patients (NOs. 1-6), and two patients (NOs.4 and 8) carrying the rtA181T resistance mutations increasingly showed high levels of rtN236T. One patient (NO. 8) experienced virological breakthrough. Other known pre-existing mutations showed no dynamic fluctuations, including in rtA194T, rtP177G, rtF249A, and rtD263E. In addition to the common substitutions, some previously unknown amino acid substitutions, such as rtD134N, rtL145M/S, rtF151Y/L, rtR153Q, and rtS223A, should be further studied.

Conclusions

HBV-resistance substitutions conferring to nucleoside analogs are present at baseline. The dynamics of the HBV RT-region quasispecies variation are heterogeneous and complex.

Veritable antiviral capacity of natural killer cells in chronic HBV infection: an argument for an earlier anti-virus treatment

Background

There is limited information on innate immunity, especially natural killer (NK) cell function, in different chronic hepatitis B (CHB) stages. Therefore, we examined whether the clinical staging strategy accurately reflects veritable NK cell immunity.

Methods

A total of 237 eligible CHB patients and 22 healthy controls were enrolled in our study. Demographic and clinical data were collected, and the CHB phases (immune active-IA, immune tolerant phase-IT, inactive CHB-IC, and grey zone-GZ) were classified according to the latest American Association for the Study of Liver Disease guidelines. Peripheral blood mononuclear cells from patients and healthy controls were tested for NK cell frequency, phenotype and function using flow cytometry.

Results

A significant decrease in activating receptor NKp44 and NKp46 expression and significant increase of exhaustion molecule Tim-3 expression were observed in NK cells from CHB patients. Reduced cytokine secretion and preserved or elevated cytotoxic function were also observed. Patients in the IT group exhibited comparable cytokine secretion and cytolytic capacity as age-matched IA patients. NK cell anti-viral functions were preserved in GZ patients. Some of the NK cell function in patients who were excluded from treatment by the current treatment guidelines was less compromised than patients who qualified for treatment.

Conclusion

Our findings provide evidence of veritable NK cell immunity during different natural history phases in treatment-naïve patients with chronic HBV Infection. Chronic HBV infection hindered NK cell function in CHB patients. However, the presumed IT and GZ statuses of CHB patients based on the clinical parameters may not accurately reflect the inner immune status of these patients and should be reconsidered. Some patients excluded from treatment by the current treatment guidelines may be able to be selected as candidates for treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1318-1) contains supplementary material, which is available to authorized users.

The Balance between CD8+ T Cell-Mediated Clearance of AAV-Encoded Antigen in the Liver and Tolerance Is Dependent on the Vector Dose

The liver continuously receives antigens from circulation and the gastrointestinal tract. A complex immune regulatory system has evolved in order to both limit inflammation and promote tolerance in the liver. Although in situ immune tolerance mechanisms enable successful gene therapy and liver transplantation, at the same time they facilitate chronic infections by pathogens such as hepatitis viruses. It is, however, poorly understood why hepatocytes infected with hepatitis viruses or transduced with adeno-associated virus (AAV)-based vectors may be rejected by CD8⁺ T cells several months later. We found that hepatic transfer of limited doses of an AAV-ovalbumin vector rapidly induced antigen-specific CD8⁺ T cells that only became functionally competent after >2 months. At this time, CD8⁺ T cells had downregulated negative checkpoint markers, e.g., the programmed death 1 [PD-1] receptor, and upregulated expression of relevant cytokines. At further reduced vector dose, only intrahepatic rather than systemic CD8⁺ T cell responses occurred, showing identical delay in antigen clearance. In contrast, PD-1-deficient mice rapidly cleared ovalbumin. Interestingly, higher vector dose directed sustained transgene expression without CD8⁺ T cell responses. Regulatory T cells, IL-10 expression, and Fas-L contributed to high-dose tolerance. Thus, viral vector doses profoundly impact CD8⁺ T cell responses.

Interferon Lambda: Modulating Immunity in Infectious Diseases

Interferon lambdas (IFN-λs; IFNL1-4) modulate immunity in the context of infections and autoimmune diseases, through a network of induced genes. IFN-λs act by binding to the heterodimeric IFN-λ receptor (IFNLR), activating a STAT phosphorylation-dependent signaling cascade. Thereby hundreds of IFN-stimulated genes are induced, which modulate various immune functions via complex forward and feedback loops. When compared to the well-characterized IFN-α signaling cascade, three important differences have been discovered. First, the IFNLR is not ubiquitously expressed: in particular, immune cells show significant variation in the expression levels of and susceptibilities to IFN-λs. Second, the binding affinities of individual IFN-λs to the IFNLR varies greatly and are generally lower compared to the binding affinities of IFN-α to its receptor. Finally, genetic variation in the form of a series of single-nucleotide polymorphisms (SNPs) linked to genes involved in the IFN-λ signaling cascade has been described and associated with the clinical course and treatment outcomes of hepatitis B and C virus infection. The clinical impact of IFN-λ signaling and the SNP variations may, however, reach far beyond viral hepatitis. Recent publications show important roles for IFN-λs in a broad range of viral infections such as human T-cell leukemia type-1 virus, rotaviruses, and influenza virus. IFN-λ also potentially modulates the course of bacterial colonization and infections as shown for Staphylococcus aureus and Mycobacterium tuberculosis. Although the immunological processes involved in controlling viral and bacterial infections are distinct, IFN-λs may interfere at various levels: as an innate immune cytokine with direct antiviral effects; or as a modulator of IFN-α-induced signaling via the suppressor of cytokine signaling 1 and the ubiquitin-specific peptidase 18 inhibitory feedback loops. In addition, the modulation of adaptive immune functions via macrophage and dendritic cell polarization, and subsequent priming, activation, and proliferation of pathogen-specific T- and B-cells may also be important elements associated with infectious disease outcomes. This review summarizes the emerging details of the IFN-λ immunobiology in the context of the host immune response and viral and bacterial infections.

Hepatic IFNL4 expression is associated with non-response to interferon-based therapy through the regulation of basal interferon-stimulated gene expression in chronic hepatitis C patients

Single nucleotide polymorphisms (SNPs) within or near interferon lambda 4 (IFNL4) gene located upstream of IFNL3 are associated with response to anti-HCV therapy both in interferon (IFN)-based and IFN-free regimens. IFNL4 encodes IFNλ4, a newly discovered type III IFN, and its expression is controlled by rs368234815-TT/ΔG, which is in strong linkage disequilibrium (LD) with other tag SNPs within or near IFNL4 such as rs12979860 and rs8099917. Intrahepatic expression levels of IFN-stimulated genes (ISGs) affect the responsiveness to IFNα and are also associated with IFNL4 genotype. However, IFNL4 expressions and its role in intrinsic antiviral innate immunity remain unclear. This study evaluated the effect of IFNL4 on intrahepatic ISG expression and investigated its relationship with treatment outcomes in liver samples obtained from 49 chronic hepatitis C patients treated with pegylated (PEG)-IFN/ribavirin therapy. IFNL4 mRNA was detected in 11 of 22 patients with IFNL4-unfavorable SNPs but not in patients with favorable genotypes. IFNL4 expression was associated with non-response to PEG-IFN/ribavirin therapy. Intrahepatic expression of antiviral ISGs (ISG15 and MX1) was significantly higher in IFNL4-unfavorable patients with detectable IFNL4 mRNA than in patients with undetectable IFNL4 mRNA, whereas the expression of suppressive ISGs (RNF125, SOCS1, SOCS3, and RNF11) was lower in patients with detectable IFNL4 mRNA. In summary, intrahepatic expression of IFNL4 was associated with increased antiviral ISG expression and decreased suppressive ISG expression at baseline, resulting in poor responsiveness to IFNα-based therapy in HCV infection.

Genome editing and the next generation of antiviral therapy

Engineered endonucleases such as homing endonucleases (HEs), zinc finger nucleases (ZFNs), Tal-effector nucleases (TALENS) and the RNA-guided engineered nucleases (RGENs or CRISPR/Cas9) can target specific DNA sequences for cleavage, and are proving to be valuable tools for gene editing. Recently engineered endonucleases have shown great promise as therapeutics for the treatment of genetic disease and infectious pathogens. In this review, we discuss recent efforts to use the HE, ZFN, TALEN and CRISPR/Cas9 gene-editing platforms as antiviral therapeutics. We also discuss the obstacles facing gene-editing antiviral therapeutics as they are tested in animal models of disease and transition towards human application.

Advance in studies on traditional Chinese medicines to treat infection with the hepatitis B virus and hepatitis C virus

Traditional Chinese medicine (TCM), as a type of complementary and alternative medicine (CAM), is a sophisticated and time-honored form of healthcare in China. Many TCMs are widely used to treat hepatitis B and hepatitis C in countries like China, Japan, and South Korea. Since conventional clinical preparations like interferon-α cause obvious dose-dependent adverse reactions and drug resistance, TCMs and related bioactive compounds have garnered increasing attention from physicians and medical researchers. Thus far, a number of TCMs and compounds have been used to inhibit the hepatitis B virus (HBV) or hepatitis C virus (HCV) in vitro, in vivo, and even in clinical trials. The current review summarizes TCMs and related compounds that have been used to inhibit HBV or HCV. Most of these medicines are derived from herbs. HepG2.2.15 cells have been used to study HBV in vitro and Huh7.5 cells have been similarly used to study HCV. Ducks have been used to study the anti-HBV effect of new medication in vivo, but there are few animal models for anti-HCV research at the present time. Thus far, a number of preclinical studies have been conducted but few clinical trials have been conducted. In addition, a few chemically modified compounds have displayed greater efficacy than natural products. However, advances in TCM research are hampered by mechanisms of action of many bioactive compounds that have yet to be identified. In short, TCMs and related active compounds are a CAM that could be used to treat HBV and HCV infections.