IFN-γ production by human natural killer cells in response to HCV-infected hepatoma cells is dependent on accessory cells

Natural Killer Cells in Viral Infection: Special Issue Editorial

NK cells are a critical cell population in innate immunity, playing an important role in antiviral immunity [...].

Immunotherapy in liver cancer: overcoming the tolerogenic liver microenvironment

Liver cancer is a major global health concern, ranking among the top causes of cancer-related deaths worldwide. Despite advances in medical research, the prognosis for liver cancer remains poor, largely due to the inherent limitations of current therapies. Traditional treatments like surgery, radiation, and chemotherapy often fail to provide long-term remission and are associated with significant side effects. Immunotherapy has emerged as a promising avenue for cancer treatment, leveraging the body's immune system to target and destroy cancer cells. However, its application in liver cancer has been limited. One of the primary challenges is the liver's unique immune microenvironment, which can inhibit the effectiveness of immunotherapeutic agents. This immune microenvironment creates a barrier, leading to drug resistance and reducing the overall efficacy of treatment. Recent studies have focused on understanding the immunological landscape of liver cancer to develop strategies that can overcome these obstacles. By identifying the specific factors within the liver that contribute to immune suppression and drug resistance, researchers aim to enhance the effectiveness of immunotherapy. Prospective strategies include combining immunotherapy with other treatments, using targeted therapies to modulate the immune microenvironment, and developing new agents that can bypass or counteract the inhibitory mechanisms in the liver. These advancements hold promise for improving outcomes in liver cancer treatment.

Cytokine Response of Natural Killer Cells to Hepatitis B Virus Infection Depends on Monocyte Co-Stimulation

Hepatitis B virus (HBV) is a major driver of chronic hepatic inflammation, which regularly leads to liver cirrhosis or hepatocellular carcinoma. Immediate innate immune cell response is crucial for the rapid clearance of the infection. Here, natural killer (NK) cells play a pivotal role in direct cytotoxicity and the secretion of antiviral cytokines as well as regulatory function. The aim of this study was to further elucidate NK cell responses triggered by an HBV infection. Therefore, we optimized HBV in vitro models that reliably stimulate NK cells using hepatocyte-like HepG2 cells expressing the Na+-taurocholate co-transporting polypeptide (NTCP) and HepaRG cells. Immune cells were acquired from healthy platelet donors. Initially, HepG2-NTCP cells demonstrated higher viral replication compared to HepaRG cells. Co-cultures with immune cells revealed increased production of interferon-γ and tumor necrosis factor-α by NK cells, which was no longer evident in isolated NK cells. Likewise, the depletion of monocytes and spatial separation from target cells led to the absence of the antiviral cytokine production of NK cells. Eventually, the combined co-culture of isolated NK cells and monocytes led to a sufficient cytokine response of NK cells, which was also apparent when communication between the two immune cell subpopulations was restricted to soluble factors. In summary, our study demonstrates antiviral cytokine production by NK cells in response to HBV+ HepG2-NTCP cells, which is dependent on monocyte bystander activation.

CD4/CD8 Ratio could be predictor of burden hepatocellular carcinoma in Egyptian chronic hepatitis C after combined sofosbuvir and daclatasvir therapy

Background

During the first years of the use of direct acting Hepatitis C antiviral drugs (DAAS), several studies reported a possible correlation between this new era of treatment and an increased risk of Hepatocellular carcinoma (HCC). Its development could possibly be favored by the changes in the immunological milieu and the different cellular behavior after eradication of HCV infection with them. For this reason, this study aimed to address the immunological effect of DAAS.

Subject & methods

Prospective paired -sample design, carried out on 90 naïve chronically infected HCV patients before and after receiving a combination therapy of sofosbuvir; at a dose of 400 mg once daily and daclatasvir; at a dose of 60 mg once daily for 12 weeks and follow up for one year. immunological tests including: total T cell count, T helper cell count, T cytotoxic cell count and natural killer cell count in peripheral blood through (CD3, CD3/CD4, CD3/CD8 and CD56 respectively) by Fluorochrome monoclonal antibodies labelled with specific dyes through Multiparameter, FACSCanto ™ II flow cytometer (Becton Dickinson, USA).

Result

Concerning the immunological changes, total T cells (CD3+), Natural killer cells showed non-significant decrease at end of therapy while significant decrease in T helper cells (CD3+CD4+) T cytotoxic cells (CD3+CD8+) compared to pre-treatment value. Long follow up revealed 26.6% developed focal HCC, in more addition, multivariate analysis show CD4/CD8 ratio could be predictor as well as sex for early development of HCC after combined DAAS therapy.

Conclusion

HCV treatment by DAAS produces significant decrease in T helper, T cytotoxic cells in CHC patients at the end of therapy. 26.6% developed focal HCC with independent CD4/CD8 predictor for burden malignancy. Further large extended population study is needed for clarify this concern.

The mononuclear phagocyte system in hepatocellular carcinoma

The mononuclear phagocyte system (MPS) consists of monocytes, dendritic cells and macrophages, which play vital roles in innate immune defense against cancer. Hepatocellular carcinoma (HCC) is a complex disease that is affected or initiated by many factors, including chronic hepatitis B virus infection, hepatitis C virus infection, metabolic disorders or alcohol consumption. Liver function, tumor stage and the performance status of patients affect HCC clinical outcomes. Studies have shown that targeted treatment of tumor microenvironment disorders may improve the efficacy of HCC treatments. Cytokines derived from the innate immune response can regulate T-cell differentiation, thereby shaping adaptive immunity, which is associated with the prognosis of HCC. Therefore, it is important to elucidate the function of the MPS in the progression of HCC. In this review, we outline the impact of HCC on the MPS. We illustrate how HCC reshapes MPS cell phenotype remodeling and the production of associated cytokines and characterize the function and impairment of the MPS in HCC.

The Prognostic Value of Natural Killer Cells and Their Receptors/Ligands in Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis

Background

Natural killer (NK) cells play major roles in eliminating tumor cells. Preliminary studies have shown that NK cells and their receptors/ligands have prognostic value in malignant tumors. However, the relevance of NK cells and their receptors/ligands level to the prognosis of hepatocellular carcinoma (HCC) remains unclear.

Methods

Several electronic databases were searched from database inception to November 8, 2021. Random effects were introduced to this meta-analysis. The relevance of NK cells and their receptors/ligands level to the prognosis of HCC was evaluated using hazard ratios (HRs) with 95% confidence interval (95%CI).

Results

26 studies were included in the analysis. The pooled results showed that high NK cells levels were associated with better overall survival (HR=0.70, 95%CI 0.57–0.86, P=0.001) and disease-free survival (HR=0.61, 95%CI 0.40-0.93, P=0.022) of HCC patients. In subgroup analysis for overall survival, CD57⁺ NK cells (HR=0.70, 95%CI 0.55-0.89, P=0.004) had better prognostic value over CD56⁺ NK cells (HR=0.69, 95%CI 0.38-1.25, P=0.224), and intratumor NK cells had better prognostic value (HR=0.71, 95%CI 0.55-0.90, P=0.005) over peripheral NK cells (HR=0.66, 95%CI 0.41-1.06, P=0.088). In addition, high level of NK cell inhibitory receptors predicted increased recurrence of HCC, while the prognostic role of NK cell activating receptors remained unclear.

Conclusion

NK cells and their inhibitory receptors have prognostic value for HCC. The prognostic role of NK cell activating receptors is unclear and more high-quality prospective studies are essential to evaluate the prognostic value of NK cells and their receptors/ligands for HCC.

Innate and Adaptive Immunopathogeneses in Viral Hepatitis; Crucial Determinants of Hepatocellular Carcinoma

Viral hepatitis B (HBV) and hepatitis C (HCV) infections remain the most common risk factors for the development of hepatocellular carcinoma (HCC), and their heterogeneous distribution influences the global prevalence of this common type of liver cancer. Typical hepatitis infection elicits various immune responses within the liver microenvironment, and viral persistence induces chronic liver inflammation and carcinogenesis. HBV is directly mutagenic but can also cause low-grade liver inflammation characterized by episodes of intermittent high-grade liver inflammation, liver fibrosis, and cirrhosis, which can progress to decompensated liver disease and HCC. Equally, the absence of key innate and adaptive immune responses in chronic HCV infection dampens viral eradication and induces an exhausted and immunosuppressive liver niche that favors HCC development and progression. The objectives of this review are to (i) discuss the epidemiological pattern of HBV and HCV infections, (ii) understand the host immune response to acute and chronic viral hepatitis, and (iii) explore the link between this diseased immune environment and the development and progression of HCC in preclinical models and HCC patients.

Natural Killer-Dendritic Cell Interactions in Liver Cancer: Implications for Immunotherapy

Simple Summary

The reciprocal crosstalk between dendritic cells (DCs) and natural killer (NK) cells plays a pivotal role in regulating immune defense against viruses and tumors. The Th-cell polarizing ability, cytokine-producing capacity, chemokine expression, and migration of DCs are regulated by activated NK cells. Conversely, the effector functions including lysis and cytokine production, proliferation, and migration of NK cells are influenced by close interactions with activated DCs. In this review, we explore the impact of DC–NK cell crosstalk and its therapeutic potential in immune control of liver malignances.

Abstract

Natural killer (NK) and dendritic cells (DCs) are innate immune cells that play a crucial role in anti-tumor immunity. NK cells kill tumor cells through direct cytotoxicity and cytokine secretion. DCs are needed for the activation of adaptive immune responses against tumor cells. Both NK cells and DCs are subdivided in several subsets endowed with specialized effector functions. Crosstalk between NK cells and DCs leads to the reciprocal control of their activation and polarization of immune responses. In this review, we describe the role of NK cells and DCs in liver cancer, focusing on the mechanisms involved in their reciprocal control and activation. In this context, intrahepatic NK cells and DCs present unique immunological features, due to the constant exposure to non-self-circulating antigens. These interactions might play a fundamental role in the pathology of primary liver cancer, namely hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC). Additionally, the implications of these immune changes are relevant from the perspective of improving the cancer immunotherapy strategies in HCC and ICC patients.

NK cells: A double edge sword against SARS-CoV-2

Natural killer (NK) cells are pivotal effectors of the innate immunity protecting an individual from microbes. They are the first line of defense against invading viruses, given their substantial ability to directly target infected cells without the need for specific antigen presentation. By establishing cellular networks with a variety of cell types such as dendritic cells, NK cells can also amplify and modulate antiviral adaptive immune responses. In this review, we will examine the role of NK cells in SARS-COV2 infections causing the ongoing COVID19 pandemic, keeping in mind the controversial role of NK cells specifically in viral respiratory infections and in inflammatory-driven lung damage. We discuss lessons learnt from previous coronavirus outbreaks in humans (caused by SARS-CoV-1 and MERS-COV).

Host immune response in chronic hepatitis C infection: involvement of cytokines and inflammasomes

Chronic liver disease is a major health issue worldwide and chronic hepatitis C (CHC) is associated with an increased risk of cirrhosis and hepatocellular carcinoma (HCC). There is evidence that the hepatitis C virus (HCV) infection is correlated with immune senescence by way of immune activation and chronic inflammation, which lead to increased metabolic and cardiovascular risk, as well as progressive liver damage. Both the innate and adaptive immunity are firmly tied to the prognosis of an infection with HCV and its response to antiviral therapy. HCV is therefore associated with increased pro-inflammatory status, heightened production of cytokines, prolonged systemic inflammation, as well as increased morbidity and mortality, mainly due to the progression of hepatic fibrosis and HCC, but also secondary to cardiovascular diseases. Viral hepatic pathology is increasingly considered a disease that is no longer merely limited to the liver, but one with multiple metabolic consequences. Numerous in vitro studies, using experimental models of acute or chronic inflammation of the liver, has brought new information on immunopathological mechanisms resulting from viral infections and have highlighted the importance of involving complex structures, inflammasomes complex, in these mechanisms, in addition to the involvement of numerous proinflammatory cytokines. Beyond obtaining a sustained viral response and halting the aforementioned hepatic fibrosis, the current therapeutic "treat-to-target" strategies are presently focused on immune-mediated and metabolic disorders, to improve the quality of life and long-term prognosis of CHC patients.

Immune Reconstitution Disorders: Spotlight on Interferons

Three decades of research in hematopoietic stem cell transplantation and HIV/AIDS fields have shaped a picture of immune restoration disorders. This manuscript overviews the molecular biology of interferon networks, the molecular pathogenesis of immune reconstitution inflammatory syndrome, and post-hematopoietic stem cell transplantation immune restoration disorders (IRD). It also summarizes the effects of thymic involution on T cell diversity, and the results of the assessment of diagnostic biomarkers of IRD, and tested targeted immunomodulatory treatments.

Mononuclear phagocyte system in hepatitis C virus infection

The mononuclear phagocyte system (MPS), which consists of monocytes, dendritic cells (DCs), and macrophages, plays a vital role in the innate immune defense against pathogens. Hepatitis C virus (HCV) is efficient in evading the host immunity, thereby facilitating its development into chronic infection. Chronic HCV infection is the leading cause of end-stage liver diseases, liver cirrhosis, and hepatocellular carcinoma. Acquired immune response was regarded as the key factor to eradicate HCV. However, innate immunity can regulate the acquired immune response. Innate immunity-derived cytokines shape the adaptive immunity by regulating T-cell differentiation, which determines the outcome of acute HCV infection. Inhibition of HCV-specific T-cell responses is one of the most important strategies for immune system evasion. It is meaningful to illustrate the role of innate immune response in HCV infection. With the MPS being the important factor in innate immunity, therefore, understanding the role of the MPS in HCV infection will shed light on the pathophysiology of chronic HCV infection. In this review, we outline the impact of HCV infection on the MPS and cytokine production. We discuss how HCV is detected by the MPS and describe the function and impairment of MPS components in HCV infection.

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.

Plasmacytoid dendritic cells control dengue and Chikungunya virus infections via IRF7-regulated interferon responses

Type I interferon (IFN-I) responses are critical for the control of RNA virus infections, however, many viruses, including Dengue (DENV) and Chikungunya (CHIKV) virus, do not directly activate plasmacytoid dendritic cells (pDCs), robust IFN-I producing cells. Herein, we demonstrated that DENV and CHIKV infected cells are sensed by pDCs, indirectly, resulting in selective IRF7 activation and IFN-I production, in the absence of other inflammatory cytokine responses. To elucidate pDC immunomodulatory functions, we developed a mouse model in which IRF7 signaling is restricted to pDC. Despite undetectable levels of IFN-I protein, pDC-restricted IRF7 signaling controlled both viruses and was sufficient to protect mice from lethal CHIKV infection. Early pDC IRF7-signaling resulted in amplification of downstream antiviral responses, including an accelerated natural killer (NK) cell-mediated type II IFN response. These studies revealed the dominant, yet indirect role of pDC IRF7-signaling in directing both type I and II IFN responses during arbovirus infections.

Viruses, like the ones responsible for the tropical diseases dengue and chikungunya, are parasites of living cells. As they cannot multiply on their own, these microbes need to infect a host cell and hijack its machinery to make more of themselves.

When a cell is invaded, it can sense the viral particles, and defend itself by releasing antiviral molecules. Some of these molecules, such as interferons, also help recruit immune cells that can fight the germs. However, viruses often evolve mechanisms to escape being detected by the cell they occupy.

Plasmacytoid dendritic cells are a rare group of immune cells, and they are able to detect when another cell is infected by the dengue virus. When they are in close physical contact with an invaded cell, these sentinels can recognize immature viral particles and release large amounts of antiviral molecules. However, it is unclear how important plasmacytoid dendritic cells are in clearing a viral infection.

Here, Webster, Werneke et al. confirmed that plasmacytoid dendritic cells were able to sense cells infected by dengue, but also by chikungunya. When this happened, the dendritic cells primarily produced interferon, rather than other defense molecules.

In addition, mice were genetically engineered so that the production of interferon was restricted to the plasmacytoid dendritic cells. When infected with dengue or chikungunya, the modified rodents resisted the diseases. These results show that, even though they are only a small percentage of all immune cells, plasmacytoid dendritic cells have an outsize role as first responders and as coordinators of the immune response.

Finally, Webster, Werneke et al. showed that when low doses of interferon are added, , the plasmacytoid dendritic cells respond more quickly to cells infected by dengue. Together these findings could potentially be leveraged to create new treatments to fight dengue. These would be of particular interest because interferons are not as damaging to the body compared to other types of defense molecules. The issue is timely since climate change is allowing the mosquitos that transmit dengue and chikungunya to live in new places, exposing more people to these serious infections.

Prokaryotic Expression and Anti-IBDV Activity of Chicken Interleukin-18 and Interferon-γ

Interferon-γ (IFN-γ), a cytokine produced by activated natural killer cells and T lymphocytes, is an important regulator of innate and adaptive immunity. Interleukin (IL)-18, also known as IFN-γ-inducing factor, is a cytokine that induces T and natural killer cells to produce IFN-γ. In this study, the chicken IL-18 (ChIL-18) and chicken IFN-γ (ChIFN-γ) genes were inserted into the pET28a prokaryotic expression vector, resulting in pET28a-IL-18 and pET28a-IFN-γ, respectively. These plasmids were transformed into Escherichia coli strain BL21, and the ChIL-18 and ChIFN-γ proteins were expressed and purified. To determine their antiviral activities, 200 ng/mL of ChIL-18 and/or ChIFN-γ were inoculated into chicken embryonic fibroblast cells. After 24 h, one 50% tissue culture infective dose (TCID50) of infectious bursal disease virus (IBDV) was inoculated into the chicken embryonic fibroblast cells. The results showed that the antiviral effect of ChIL-18 and ChIFN-γ in combination was better than that of ChIL-18 or ChIFN-γ alone. Next, 14-day-old chicken were injected with 200 µg of ChIL-18 and/or ChIFN-γ and then were challenged with 103 TCID50 of IBDV via intraperitoneal injection. The results showed that the proliferation of IBDV was inhibited by the injection of the recombinant proteins, especially the combination of ChIL-18 and ChIFN-γ, as evidenced by cytokine detection, quantitative PCR, and pathology analyses. These results indicate that ChIL-18 and ChIFN-γ could inhibit IBDV infection and the combination of ChIL-18 and ChIFN-γ has a better inhibitory effect than either cytokine alone.

Interferon-α-Enhanced CD100/Plexin-B1/B2 Interactions Promote Natural Killer Cell Functions in Patients with Chronic Hepatitis C Virus Infection

Background

CD100, also known as Sema4D, is an immune semaphorin constitutively expressed on natural killer (NK) cells and T cells. As an immune activation molecule, CD100 has important immunoregulatory effects on NK functions by enhancing the interactions between NK cells and target cells. The aim of this study was to investigate whether hepatitis C virus (HCV) infection affects CD100 expression, and whether interferon-α treatment enhances NK killing activity to facilitate HCV clearance via CD100.

Methods

Expression of CD100 on NK cells was evaluated by flow cytometry in patients with chronic HCV infection, with or without pegylated interferon-α-based therapy. NK cell cytotoxicity and interferon (IFN)-γ production were measured by flow cytometry upon culturing the NK cells with K562 and Huh7.5 or HCV JFH-1-infected Huh7.5 cells.

Results

The frequency of CD100⁺ NK cells in HCV-infected individuals was slightly suppressed compared to healthy subjects. IFN-α treatment could significantly upregulate CD100 expression, which was confirmed by in vitro studies using peripheral blood mononuclear cells cocultured with HCV-expressing Huh7.5 cells or IFN-α. Importantly, the expression of CD100 on NK cells from HCV patients was inversely associated with the HCV-RNA levels in the early phase of IFN-α therapy, and the IFN-α upregulated CD100 led to an enhanced NK killing activity through ligations with its receptors plexin-B1/B2 on target cells.

Conclusion

These results implied a novel mechanism by which IFN-α enhanced CD100/Plexin-B1/B2 interaction plays an important role in promoting NK functions in patients with chronic hepatitis C.

Effect of IL15 rs10833 and SCARB1 rs10846744 on virologic responses in chronic hepatitis C patients treated with pegylated interferon-α and ribavirin

The scavenger receptor type B class I (SCARBI) is known to be involved in the entry of hepatitis C virus (HCV) into the host, while interleukin-15 (IL15) is an important cytokine in both the innate and acquired immune responses against HCV infection. We investigated the association of IL15 rs10833 or SCARB1 rs10846744 polymorphisms with treatment responses in patients with chronic HCV (CHC). SCARB1 rs10846744 and IL15 rs10833 were identified in 365 treatment-naïve CHC patients through genotyping by TaqMan® Real-Time PCR and PCR-restriction fragment length polymorphism (RFLP), respectively. Of these 365 CHC treatment-naïve patients, rapid virological response (RVR), complete early virological response (cEVR), and sustained virological response (SVR) were observed in 53.2%, 76.4%, and 66.0% of the patients, respectively. Multivariate logistic regression analysis revealed that RVR was associated with sex (P=0.016), aspartate aminotransferase (AST) (P=0.026), IL15 rs10833 (AA) genotype (P<0.001), and SCARB1 rs10846744 (CC) genotype (P<0.001), while there was a relationship between alanine aminotransferase (ALT) (P=0.013) and IL15 rs10833 (AA) genotype (P<0.001) with cEVR. Age (<40years) (P=0.001), AST (P=0.029), ALP (P=0.028), HCV genotypes (P=0.005), HCV viral load (P=0.026), IL15 rs10833 (AA) genotype (P<0.001), and SCARB1 rs10846744 (CC) genotype (P=0.001) were strongly associated with SVR. In conclusion, the SCARB1 rs10846744 (CC) and IL15 rs10833 (AA) genotypes can be considered as powerful predictors of treatment responses in CHC patients treated with an interferon-based therapy.

Interaction and Mutual Activation of Different Innate Immune Cells Is Necessary to Kill and Clear Hepatitis C Virus-Infected Cells

Innate immune cells can sense hepatitis C virus (HCV)-infected cells and respond with anti-viral actions including secretion of interferons (IFNs). In previous studies, the response of individual innate immune cells against HCV was analyzed in detail. We hypothesized that interaction of multiple innate immune cells increases the magnitude of the immune response and eventually leads to clearance of HCV-infected cells. To investigate this, we co-cultured Huh-7 HCV subgenomic replicon (SGR) cells with peripheral blood mononuclear cells (PBMCs). We confirm secretion of IFNα by plasmacytoid dendritic cells (pDCs) and IFNγ by natural killer (NK) cells in the co-culture setup. Moreover, we observed that also monocytes contribute to the anti-viral response. Flow cytometry and ImageStream analysis demonstrated that monocytes take up material from HCV SGR cells in co-culture with PBMCs. Preceding the uptake, PBMCs caused apoptosis of HCV SGR cells by tumor necrosis factor-related apoptosis inducing ligand (TRAIL) expression on NK cells. We observed that only the interplay of monocytes, pDCs, and NK cells resulted in efficient clearance of HCV SGR cells, while these cell populations alone did not kill HCV SGR cells. Despite similar TRAIL receptor expression on Huh-7 control cells and HCV SGR cells, HCV activated PBMCs specifically killed HCV SGR cells and did not target Huh-7 control cells. Finally, we showed that HCV replicating cells per se are sensitive toward TRAIL-induced apoptosis. Our results highlight the importance of the interplay of different innate immune cells to initiate an efficient, rapid, and specific response against HCV-infected cells.

Immunogenetic studies of the hepatitis C virus infection in an era of pan-genotype antiviral therapies - Effective treatment is coming

What are the factors that influence human hepatitis C virus (HCV) infection, hepatitis status establishment, and disease progression? Firstly, one has to consider the genetic background of the host and HCV genotypes. The immunogenetic host profile will reflect how each infected individual deals with infection. Secondly, there are environmental factors that drive susceptibility or resistance to certain viral strains. These will dictate (I) the susceptibility to infection; (II) whether or not an infected person will promote viral clearance; (III) the immune response and the response profile to therapy; and (IV) whether and how long it would take to the development of HCV-associated diseases, as well as their severity. Looking at this scenario, this review addresses clinical aspects of HCV infection, following by an update of molecular and cellular features of the immune response against the virus. The evasion mechanisms used by HCV are presented, considering the potential role of exosomes in infection. Genetic factors influencing HCV infection and pathogenesis are the main topics of the article. Shortly, HLAs, MBLs, TLRs, ILs, and IFNLs genes have relevant roles in the susceptibility to HCV infection. In addition, ILs, IFNLs, as well as TLRs genes are important modulators of HCV-associated diseases. The viral aspects that influence HCV infection are presented, followed by a discussion about evolutionary aspects of host and HCV interaction. HCV and HIV infections are close related. Thus, we also present a discussion about HIV/HCV co-infection, focusing on cellular and molecular aspects of this interaction. Pharmacogenetics and treatment of HCV infection are the last topics of this review. The understanding of how the host genetics interacts with viral and environmental factors is crucial for the development of new strategies to prevent HCV infection, even in an era of potential development of pan-genotypic antivirals.

Brief Report: CD14brightCD16- monocytes and sCD14 level negatively associate with CD4-memory T-cell frequency and predict HCV-decline on therapy

During HIV+ hepatitis C virus (HCV)+ coinfection CD14CD16 monocytes produce soluble immune-activation markers that predict disease progression and poor response to interferon (IFN)-α treatment. We evaluated relationships among immune activation, monocyte phenotype, CD4-memory T cells, and HCV-, cytomegalovirus-, and cytomegalovirus/Epstein-Barr virus/influenza-specific IFN-γ-response before and during IFN-α treatment. Effector-memory and central-memory CD4 T-cell frequencies were lower in HCV+ HIV+ donors than in uninfected donors and correlated negatively with HCV level, CD14CD16 monocytes, and plasma sCD14. sCD14 and CD14CD16 monocytes negatively correlated with IFN-α-dependent HCV decline. CD4 effector-memory T cells positively associated with cytomegalovirus/Epstein-Barr virus/influenza(CEF)-specific IFN-γ response, while sCD14 negatively associated with both CD4 effector-memory T cells and CEF-specific IFN-γ response. These data support a role for memory-CD4 T cells in HCV containment and link immune activation and CD14CD16-monocyte frequency to the failure of IFN-dependent HCV clearance.

Inflammatory monocytes require type I interferon receptor signaling to activate NK cells via IL-18 during a mucosal viral infection

Although type I interferon is critical for NK cell activation, the underlying mechanism is under debate and is unknown during a mucosal infection. Lee et al. have determined that type I interferon induces inflammatory monocytes to produce IL-18 to directly activate NK cells to combat viral infections.

The requirement of type I interferon (IFN) for natural killer (NK) cell activation in response to viral infection is known, but the underlying mechanism remains unclear. Here, we demonstrate that type I IFN signaling in inflammatory monocytes, but not in dendritic cells (DCs) or NK cells, is essential for NK cell function in response to a mucosal herpes simplex virus type 2 (HSV-2) infection. Mice deficient in type I IFN signaling, Ifnar^−/− and Irf9^−/− mice, had significantly lower levels of inflammatory monocytes, were deficient in IL-18 production, and lacked NK cell–derived IFN-γ. Depletion of inflammatory monocytes, but not DCs or other myeloid cells, resulted in lower levels of IL-18 and a complete abrogation of NK cell function in HSV-2 infection. Moreover, this resulted in higher susceptibility to HSV-2 infection. Although Il18^−/− mice had normal levels of inflammatory monocytes, their NK cells were unresponsive to HSV-2 challenge. This study highlights the importance of type I IFN signaling in inflammatory monocytes and the induction of the early innate antiviral response.

CD14+ monocyte-derived galectin-9 induces natural killer cell cytotoxicity in chronic hepatitis C

Natural killer (NK) cell activation is associated with both liver injury and persistent infection in chronic hepatitis C (CHC); however, the detailed mechanism of this activation has not yet been fully elucidated. Because galectin-9 (Gal-9) has been reported to be increased in the serum and liver tissue of CHC patients, we investigated the function of Gal-9 in NK cell activation in CHC. First, we evaluated the function of Gal-9 on NK cytotoxicity in vitro. Gal-9 treatment resulted in increased cytotoxicity of naïve NK cells, and the Gal-9-activated NK cells demonstrated cytotoxicity toward hepatoma cells and T cells. Additionally, coculturing peripheral blood mononuclear cells (PBMCs) with JFH-1/Huh7.5.1 cells increased both Gal-9 production and NK cell cytotoxicity. Next, we investigated the source of Gal-9 and the mechanism of Gal-9 production. Deletion of CD14⁺ monocytes from PBMCs resulted in reduced Gal-9 production in the coculture with JFH-1/Huh7.5.1 cells. Gal-9 production was driven by coculturing of PBMCs with apoptotic hepatocytes. Blocking integrin α_v β₃ , a receptor for phosphatidylserine expressed on apoptotic cells, also resulted in decreased Gal-9 production. Finally, we found that serum Gal-9 levels were significantly higher in CHC patients than in healthy donors and patients who achieved sustained virologic response. Among CHC patients, serum Gal-9 levels were significantly higher in patients with elevated alanine aminotransferase (ALT) than in those with normal ALT.

CONCLUSION

These results demonstrate that CD14⁺ monocyte-derived Gal-9 increases NK cell cytotoxicity in HCV infection, which might be associated with liver injury and persistent infection. (Hepatology 2017;65:18-31).

IL15 polymorphism is associated with advanced fibrosis, inflammation-related biomarkers and virological response in human immunodeficiency virus/hepatitis C virus coinfection

BACKGROUND & AIMS

IL15 is an essential cytokine in both innate and adaptive immune response against hepatitis C virus (HCV) infection. The aim was to analyze whether IL15 rs10833 is associated with liver disease severity and response to pegylated-interferon-alpha plus ribavirin (pegIFN-alpha/RBV) therapy in human immunodeficiency virus (HIV)-/HCV-co-infected patients.

METHODS

A retrospective study was performed in 315 patients who started pegIFN-alpha/RBV therapy. Liver fibrosis stage was characterized in 286 patients. IL15 rs10833 and IL28B rs12980275 were genotyped by GoldenGate. The primary outcomes were: (a) advanced liver fibrosis evaluated by liver biopsy (F3-F4) or transient elastography (liver stiffness values ≥9.5 Kpa); (b) sustained virological response (SVR). The secondary outcome variable was the levels of serum biomarkers of inflammation.

RESULTS

Patients with rs10833 AA genotype had increased odds of having advanced fibrosis (adjusted odds ratio (aOR) = 2.30; P = 0.019), particularly in males (aOR = 2.24; P = 0.040), patients with HCV serum viral load (HCV-RNA) <500 000 IU/ml (aOR = 5.14; P = 0.018) and patients with IL28B rs12980275 AG/GG genotypes (aOR = 2.51; P = 0.046). Moreover, rs10833 AA genotype was significantly associated with higher levels of hepatocyte growth factor (adjusted arithmetic mean ratio (aAMR) = 1.50; P = 0.016), sICAM-1 (aAMR = 1.57; P = 0.025) and sVCAM-1 (aAMR = 1.56; P = 0.007). Finally, patients with rs10833 AA genotype had increased odds of achieving SVR (aOR = 3.12; P = 0.006), particularly in males (aOR = 3.69; P = 0.005), GT1/4 patients (aOR = 3.59; P = 0.006), patients with advanced fibrosis (aOR = 4.64; P = 0.021), HCV-RNA ≥500 000 IU/ml (aOR = 3.92; P = 0.007) and patients with IL28B rs12980275 AG/GG genotype (aOR = 2.98; P = 0.041).

CONCLUSIONS

The presence of IL15 rs10833 AA genotype in HIV-/HCV-co-infected patients was associated with advanced liver fibrosis, inflammation-related biomarkers and increased rates of SVR to pegIFN-alpha/RBV therapy.

IFN-λ3 polymorphism indirectly influences NK cell phenotype and function during acute HCV infection

Introduction

Polymorphisms in the type III interferon IFN‐λ3 and the killer cell immunoglobulin‐like receptor (KIR) genes controlling the activity of natural killer (NK) cells can predict spontaneous resolution of acute hepatitis C virus (HCV) infection. We hypothesized that IFN‐λ3 polymorphism may modulate NK cell function during acute HCV.

Methods

We monitored the plasma levels of type III IFNs in relation to the phenotype and the function of NK cells in a cohort of people who inject drugs (PWID) during acute HCV infection with different outcomes.

Results

Early acute HCV was associated with high variability in type III IFNs plasma levels and the favorable IFN‐λ3 CC genotype was associated with higher viral loads. Reduced expression of Natural Killer Group Protein 2A (NKG2A) was associated with lower IFN‐λ3 plasma levels and the CC genotype. IFN‐γ production by NK cells was higher in individuals with the CC genotype during acute infection but this did not prevent viral persistence. IFN‐λ3 plasma levels did not correlate with function of NK cells and IFN‐λ3 prestimulation did not affect NK cell activation and function.

Conclusions

These results suggest that IFN‐λ3 polymorphism indirectly influences NK cell phenotype and function during acute HCV but other factors may act in concert to determine the outcome of the infection.

Natural killer cells in hepatitis C: Current progress

Patients infected with the hepatitis C virus (HCV) are characterized by a high incidence of chronic infection, which results in chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The functional impairment of HCV-specific T cells is associated with the evolution of an acute infection to chronic hepatitis. While T cells are the important effector cells in adaptive immunity, natural killer (NK) cells are the critical effector cells in innate immunity to virus infections. The findings of recent studies on NK cells in hepatitis C suggest that NK cell responses are indeed important in each phase of HCV infection. In the early phase, NK cells are involved in protective immunity to HCV. The immune evasion strategies used by HCV may target NK cells and might contribute to the progression to chronic hepatitis C. NK cells may control HCV replication and modulate hepatic fibrosis in the chronic phase. Further investigations are, however, needed, because a considerable number of studies observed functional impairment of NK cells in chronic HCV infection. Interestingly, the enhanced NK cell responses during interferon-α-based therapy of chronic hepatitis C indicate successful treatment. In spite of the advances in research on NK cells in hepatitis C, establishment of more physiological HCV infection model systems is needed to settle unsolved controversies over the role and functional status of NK cells in HCV infection.

Virological Mechanisms in the Coinfection between HIV and HCV

Due to shared transmission routes, coinfection with Hepatitis C Virus (HCV) is common in patients infected by Human Immunodeficiency Virus (HIV). The immune-pathogenesis of liver disease in HIV/HCV coinfected patients is a multifactorial process. Several studies demonstrated that HIV worsens the course of HCV infection, increasing the risk of cirrhosis and hepatocellular carcinoma. Also, HCV might increase immunological defects due to HIV and risk of comorbidities. A specific cross-talk among HIV and HCV proteins in coinfected patients modulates the natural history, the immune responses, and the life cycle of both viruses. These effects are mediated by immune mechanisms and by a cross-talk between the two viruses which could interfere with host defense mechanisms. In this review, we focus on some virological/immunological mechanisms of the pathogenetic interactions between HIV and HCV in the human host.

Innate detection of hepatitis B and C virus and viral inhibition of the response

Viral hepatitis caused by hepatitis B virus (HBV) and hepatitis C virus (HCV) infections poses a significant burden to the public health system. Although HBV and HCV differ in structure and life cycles, they share unique characteristics, such as tropism to infect hepatocytes and association with hepatic and extrahepatic disorders that are of innate immunity nature. In response to HBV and HCV infection, the liver innate immune cells eradicate pathogens by recognizing specific molecules expressed by pathogens via distinct cellular pattern recognition receptors whose triggering activates intracellular signalling pathways inducing cytokines, interferons and anti-viral response genes that collectively function to clear infections. However, HBV and HCV evolve strategies to inactivate innate signalling factors and as such establish persistent infections without being recognized by the innate immunity. We review recent insights into how HBV and HCV are sensed and how they evade innate immunity to establish chronicity. Understanding the mechanisms of viral hepatitis is mandatory to develop effective and safe therapies for eradication of viral hepatitis.

Effects of Bush Sophora Root polysaccharide and its sulfate on immuno-enhancing of the therapeutic DVH

Bush Sophora Root polysaccharide (BSRPS) and its sulfate, sulfated Bush Sophora Root polysaccharide (sBSRPS), possess the antiviral activities against duck hepatitis A virus. However their antiviral mechanisms are still not clear. This paper reported their immuno-enhancing roles in the therapeutic effects for duck virus hepatitis (DVH). The effects of BSRPS and sBSRPS on stimulating lymphocyte proliferation were investigated by MTT methods. After that, ducklings were challenged with DHAV and treated with BSRPS and sBSRPS. Meanwhile, the total antibody (Ab), cytokines including interferon gamma (IFN-γ), hepatocyte growth factor (HGF), interleukin (IL)-2, IL-6 and IL-8 were determined by enzyme-linked immuno sorbent assay methods. The results showed that BSRPS owned a fine hepatoprotective effect with stable HGF producing ability. Sulfated modification was able to increase the proliferation rates of B and T lymphocytes and the secretions of total Ab, IFN-γ and IL-2, as comparison with those of BSRPS group. In summary, both of them exhibited immuno-enhancing effects on the therapeutic effects for DVH, and the capacity of sBSRPS was stronger than that of BSRPS.

Osteopontin promotes dendritic cell maturation and function in response to HBV antigens

Purpose

Dendritic cells (DCs) play critical roles in promoting innate and adaptive immunity in microbial infection. Functional impairment of DCs may mediate the suppression of viral-specific T-cell immune response in chronic hepatitis B (CHB) patients. Osteopontin (OPN) is involved in several liver diseases and infectious diseases. However, whether OPN affects DC function in hepatitis B virus (HBV) infection is unknown.

Methods

Twenty CHB patients and 20 healthy volunteers were recruited. OPN secreted by DCs was compared. Peripheral blood mononuclear cells cultured with OPN antibody were examined to study the costimulatory molecular expression and interleukin (IL)-12 production of DCs after HBV antigenic stimulation. OPN-deficient mice were used to investigate the influence of OPN on DC maturation and function after HBV antigenic stimulation in vitro and in vivo. Exogenous OPN was administrated to further verify the functioning of DCs from CHB patients upon HBV antigenic stimulation.

Results

We found that OPN production of DCs from CHB patients was significantly lower than those from healthy volunteers. The absence of OPN impaired IL-12 production and costimulatory molecular expression of DCs upon stimulation with HBV antigens. Defective DC function led to reduced activation of Th1 response to HBV antigens. In addition, OPN deficiency in DCs reduced the HBV antigen-induced inflammatory response in the liver of mice. Importantly, OPN administration significantly promoted the maturation of DCs from CHB patients in vitro.

Conclusion

These findings suggested that OPN could improve the maturation and functioning of DCs in the immune response to HBV antigens, which might be useful to further improve the effect of DC vaccine.

Anti-duck virus hepatitis mechanisms of Bush Sophora Root polysaccharide and its sulfate verified by intervention experiments

In our previous study, Bush Sophora Root polysaccharide (BSRPS) and its sulfate (sBSRPS) exhibited anti-duck virus hepatitis (DVH) abilities as well as anti-oxidative and immuno-enhancement effects. The aim of this paper was to ulteriorly investigate the exact anti-DVH mechanisms of BSRPS and sBSRPS by intervention experiments. Hinokitiol and FK506 were used as the pro-oxidant and immunosuppressant, respectively. The dynamic deaths, oxidative and immune evaluation indexes and hepatic pathological change scores were detected. When was intervened by hinokitiol, sBSRPS still possessed therapeutic effect while BSPRS was useless. Under the condition of immunosuppression, BSRPS lost a part role in treating DVH; however such a role of sBSRPS completely exhausted. These results suggested both anti-oxidative and immuno-enhancement effects of BSRPS played roles in healing DVH, and the former was more crucial; unlike BSRPS, only immuno-enhancement ability of sBSRPS was imperative for its curative effect on DVH.

Interleukin-2 from Adaptive T Cells Enhances Natural Killer Cell Activity against Human Cytomegalovirus-Infected Macrophages

Control of human cytomegalovirus (HCMV) requires a continuous immune surveillance, thus HCMV is the most important viral pathogen in severely immunocompromised individuals. Both innate and adaptive immunity contribute to the control of HCMV. Here, we report that peripheral blood natural killer cells (PBNKs) from HCMV-seropositive donors showed an enhanced activity toward HCMV-infected autologous macrophages. However, this enhanced response was abolished when purified NK cells were applied as effectors. We demonstrate that this enhanced PBNK activity was dependent on the interleukin-2 (IL-2) secretion of CD4(+) T cells when reexposed to the virus. Purified T cells enhanced the activity of purified NK cells in response to HCMV-infected macrophages. This effect could be suppressed by IL-2 blocking. Our findings not only extend the knowledge on the immune surveillance in HCMV-namely, that NK cell-mediated innate immunity can be enhanced by a preexisting T cell antiviral immunity-but also indicate a potential clinical implication for patients at risk for severe HCMV manifestations due to immunosuppressive drugs, which mainly suppress IL-2 production and T cell responsiveness.

IMPORTANCE

Human cytomegalovirus (HCMV) is never cleared by the host after primary infection but instead establishes a lifelong latent infection with possible reactivations when the host's immunity becomes suppressed. Both innate immunity and adaptive immunity are important for the control of viral infections. Natural killer (NK) cells are main innate effectors providing a rapid response to virus-infected cells. Virus-specific T cells are the main adaptive effectors that are critical for the control of the latent infection and limitation of reinfection. In this study, we found that IL-2 secreted by adaptive CD4(+) T cells after reexposure to HCMV enhances the activity of NK cells in response to HCMV-infected target cells. This is the first direct evidence that the adaptive T cells can help NK cells to act against HCMV infection.

Alcohol and HCV: implications for liver cancer

Liver cancers are one of the deadliest known malignancies which are increasingly becoming a major public health problem in both developed and developing countries. Overwhelming evidence suggests a strong role of infection with hepatitis B and C virus (HBV and HCV), alcohol abuse, as well as metabolic diseases such as obesity and diabetes either individually or synergistically to cause or exacerbate the development of liver cancers. Although numerous etiologic mechanisms for liver cancer development have been advanced and well characterized, the lack of definite curative treatments means that gaps in knowledge still exist in identifying key molecular mechanisms and pathways in the pathophysiology of liver cancers. Given the limited success with current therapies and preventive strategies against liver cancer, there is an urgent need to identify new therapeutic options for patients. Targeting HCV and or alcohol-induced signal transduction, or virus-host protein interactions may offer novel therapies for liver cancer. This review summarizes current knowledge on the mechanistic development of liver cancer associated with HCV infection and alcohol abuse as well as highlights potential novel therapeutic strategies.

Innate and adaptive immune responses in HCV infections

Hepatitis C virus has been identified a quarter of a decade ago as a leading cause of chronic viral hepatitis that can lead to cirrhosis and hepatocellular carcinoma. Only a minority of patients can clear the virus spontaneously during acute infection. Elimination of HCV during acute infection correlates with a rapid induction of innate, especially interferon (IFN) induced genes, and a delayed induction of adaptive immune responses. However, the majority of patients is unable to clear the virus and develops viral persistence in face of an ongoing innate and adaptive immune response. The virus has developed several strategies to escape these immune responses. For example, to escape innate immunity, the HCV NS3/4A protease can efficiently cleave and inactivate two important signalling molecules in the sensory pathways that react to HCV pathogen-associated molecular patterns (PAMPs) to induce IFNs, i.e., the mitochondrial anti-viral signalling protein (MAVS) and the Toll-IL-1 receptor-domain-containing adaptor-inducing IFN-β (TRIF). Despite these escape mechanisms, IFN-stimulated genes (ISGs) are induced in a large proportion of patients with chronic infection. Of note, chronically HCV infected patients with constitutive IFN-stimulated gene (ISG) expression have a poor response to treatment with pegylated IFN-α (PegIFN-α) and ribavirin. The mechanisms that protect HCV from IFN-mediated innate immune reactions are not entirely understood, but might involve blockade of ISG protein translation at the ribosome, localization of viral replication to cell compartments that are not accessible to anti-viral IFN-stimulated effector systems, or direct antagonism of effector systems by viral proteins. Escape from adaptive immune responses can be achieved by emergence of viral escape mutations that avoid recognition by antibodies and T cells. In addition, chronic infection is characterized by the presence of functionally and phenotypically altered NK and T cell responses that are unable to clear the virus but most likely contribute to the ongoing liver disease. In this review, we will summarize current knowledge about the role of innate and adaptive immune responses in determining the outcome of HCV infection.

Protection against hepatitis C infection via NK cells in highly-exposed uninfected injecting drug users

BACKGROUND & AIMS

HCV seroprevalence surveys in longstanding injecting drug users (IDUs) reveal a small minority who remain seronegative, with some exhibiting HCV-specific cellular immunity. This study aimed to characterise this immunity, assess associations with risk behaviours and protection against infection.

METHODS

A nested case-control series from a prospective cohort of seronegative IDUs was selected with incident cases (IN; n = 28) matched by demographics and risk behaviour to exposed uninfected (EU) subjects (n = 28). Samples were assayed for natural killer (NK) cell phenotypes and function, HCV-specific IFNγ in ELISpot, and HCV-specific CD4 T effector responses. IL28B and HLA-C/KIR2DL3 genotypes were tested.

RESULTS

Numbers of activated (CD69(+)) NK cells in the mature CD56(dim)CD16(+) subset, and cytotoxic (NKp30(+)) cells in the CD56(bright)CD16(+) subset were higher in the EU subjects (p = 0.040, p = 0.038 respectively). EU subjects had higher frequencies of interferon gamma (IFNγ) producing NK cells, and lower frequencies of CD107a expression (p = 0.003, p = 0.015 respectively). By contrast, the frequency, magnitude, and breadth of HCV-specific CD4 and CD8 T cell responses did not differ, nor did IL28B, HLA-C, or KIR2DL3 allele frequencies.

CONCLUSIONS

Sustained NK cell activation contributes to protection against HCV infection. HCV-specific cellular immunity is prevalent in EU subjects but does not appear to be protective.

Recent advances in the anti-HCV mechanisms of interferon

Interferon (IFN) in combination with ribavirin has been the standard of care (SOC) for chronic hepatitis C for the past few decades. Although the current SOC lacks the desired efficacy, and 4 new direct-acting antiviral agents have been recently approved, interferons are still likely to remain the cornerstone of therapy for some time. Moreover, as an important cytokine system of innate immunity, host interferon signaling provides a powerful antiviral response. Nevertheless, the mechanisms by which HCV infection controls interferon production, and how interferons, in turn, trigger anti-HCV activities as well as control the outcome of HCV infection remain to be clarified. In this report, we review current progress in understanding the mechanisms of IFN against HCV, and also summarize the knowledge of induction of interferon signaling by HCV infection.

Endogenous intrahepatic IFNs and association with IFN-free HCV treatment outcome

BACKGROUND. Hepatitis C virus (HCV) infects approximately 170 million people worldwide and may lead to cirrhosis and hepatocellular carcinoma in chronically infected individuals. Treatment is rapidly evolving from IFN-α-based therapies to IFN-α-free regimens that consist of directly acting antiviral agents (DAAs), which demonstrate improved efficacy and tolerability in clinical trials. Virologic relapse after DAA therapy is a common cause of treatment failure; however, it is not clear why relapse occurs or whether certain individuals are more prone to recurrent viremia. METHODS. We conducted a clinical trial using the DAA sofosbuvir plus ribavirin (SOF/RBV) and performed detailed mRNA expression analysis in liver and peripheral blood from patients who achieved either a sustained virologic response (SVR) or relapsed. RESULTS. On-treatment viral clearance was accompanied by rapid downregulation of IFN-stimulated genes (ISGs) in liver and blood, regardless of treatment outcome. Analysis of paired pretreatment and end of treatment (EOT) liver biopsies from SVR patients showed that viral clearance was accompanied by decreased expression of type II and III IFNs, but unexpectedly increased expression of the type I IFN IFNA2. mRNA expression of ISGs was higher in EOT liver biopsies of patients who achieved SVR than in patients who later relapsed. CONCLUSION. These results suggest that restoration of type I intrahepatic IFN signaling by EOT may facilitate HCV eradication and prevention of relapse upon withdrawal of SOF/RBV. TRIAL REGISTRATION. ClinicalTrials.gov NCT01441180.

Innate immune cell networking in hepatitis C virus infection

Persistent viral infection, such as HCV infection, is the result of the inability of the host immune system to mount a successful antiviral response, as well as the escape strategies devised by the virus. Although each individual component of the host immune system plays important roles in antiviral immunity, the interactive network of immune cells as a whole acts against the virus. The innate immune system forms the first line of host defense against viral infection, and thus, virus elimination or chronic HCV infection is linked to the direct outcome of the interactions between the various innate immune cells and HCV. By understanding how the distinct components of the innate immune system function both individually and collectively during HCV infection, potential therapeutic targets can be identified to overcome immune dysfunction and control chronic viral infection.

Monocytes activate natural killer cells via inflammasome-induced interleukin 18 in response to hepatitis C virus replication

BACKGROUND & AIMS

Production of interferon (IFN)-γ by natural killer (NK) cells is attenuated during chronic infection with hepatitis C virus (HCV). We investigated whether this is due to intrinsic or extrinsic mechanisms of NK cells.

METHODS

Peripheral blood mononuclear cells (PBMCs) were collected from patients with chronic HCV infection or uninfected blood donors (controls); NK cells and monocytes were isolated or eliminated. We cultured hepatoma cells that express luciferase-tagged subgenomic HCV replicons (Huh7/HCV replicon cells) or their HCV-negative counterparts (Huh7) with NK cells in the presence or absence of other populations of PBMCs. Antiviral activity, cytotoxicity, and cytokine production were assessed.

RESULTS

NK cells produced greater amounts of IFN-γ when PBMC were cocultured with Huh7/HCV replicon cells than with Huh7 cells; NK cells and PBMCs from controls suppressed HCV replication to a greater extent than those from patients with chronic HCV infection. This antiviral effect was predominantly mediated by tumor necrosis factor (TNF)-α and IFN-γ. The antiviral activity of NK cells and their production of IFN-γ were reduced when they were used in coculture alone (rather than with PBMC), or after depletion of CD14(+) monocytes, after knockdown of the inflammasome in monocytes, or after neutralization of interleukin-18, which is regulated by the inflammasome. These findings indicate a role for monocytes in NK cell activation. Compared with control monocytes, monocytes from patients with chronic HCV infection had reduced TNF-α-mediated (direct) and reduced NK cell-mediated (indirect) antiviral effects. Control monocytes increased the antiviral effects of NK cells from patients with chronic HCV infection and their production of IFN-γ.

CONCLUSIONS

Monocytes sense cells that contain replicating HCV and respond by producing interleukin-18 via the inflammasome and by activating NK cells. Patients with chronic HCV infection have reduced monocyte function, attenuating NK cell IFN-γ-mediated responses.

Expansion of NK cells by engineered K562 cells co-expressing 4-1BBL and mMICA, combined with soluble IL-21

NK cells hold promise for protecting hosts from cancer and pathogen infection through direct killing and expressing immune-regulatory cytokines. In our study, a genetically modified K562 cell line with surface expression of 4-1BBL and MICA was constructed to expand functional NK cells in vitro for further adoptive immunotherapy against cancer. After a long-term up to 21 day co-culture with newly isolated peripheral blood mononuclear cells (PBMCs) in the presence of soluble IL-21 (sIL-21), notable increase in proportion of expanded NK cells was observed, especially the CD56(bright)CD16(+) subset. Apparent up-regulation of activating receptors CD38, CD69 and NKG2D was detected on expanded NK cells, so did inhibitory receptor CD94; the cytotoxicity of expanded NK cells against target tumor cells exceeded that of NK cells within fresh PBMCs. The intracellular staining showed expanded NK cells produced immune-regulatory IFN-γ. Taken together, we expanded NK cells with significant up-regulation of activating NKG2D and moderate enhancement of cytotoxicity, with IFN-γ producing ability and a more heterogeneous population of NK cells. These findings provide a novel perspective on expanding NK cells in vitro for further biology study and adoptive immunotherapy of NK cells against cancer.

CD81 and hepatitis C virus (HCV) infection

Hepatitis C Virus (HCV) infection is a global public health problem affecting over 160 million individuals worldwide. Its symptoms include chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. HCV is an enveloped RNA virus mainly targeting liver cells and for which the initiation of infection occurs through a complex multistep process involving a series of specific cellular entry factors. This process is likely mediated through the formation of a tightly orchestrated complex of HCV entry factors at the plasma membrane. Among HCV entry factors, the tetraspanin CD81 is one of the best characterized and it is undoubtedly a key player in the HCV lifecycle. In this review, we detail the current knowledge on the involvement of CD81 in the HCV lifecycle, as well as in the immune response to HCV infection.

An insight into the diagnosis and pathogenesis of hepatitis C virus infection

This review focuses on research findings in the area of diagnosis and pathogenesis of hepatitis C virus (HCV) infection over the last few decades. The information based on published literature provides an update on these two aspects of HCV. HCV infection, previously called blood transmitted non-A, non-B infection, is prevalent globally and poses a serious public health problem worldwide. The diagnosis of HCV infection has evolved from serodetection of non-specific and low avidity anti-HCV antibodies to detection of viral nucleic acid in serum using the polymerase chain reaction (PCR) technique. Current PCR assays detect viral nucleic acid with high accuracy and the exact copy number of viral particles. Moreover, multiplex assays using real-time PCR are available for identification of HCV-genotypes and their isotypes. In contrast to previous methods, the newly developed assays are not only fast and economic, but also resolve the problem of the window period as well as differentiate present from past infection. HCV is a non-cytopathic virus, thus, its pathogenesis is regulated by host immunity and metabolic changes including oxidative stress, insulin resistance and hepatic steatosis. Both innate and adaptive immunity play an important role in HCV pathogenesis. Cytotoxic lymphocytes demonstrate crucial activity during viral eradication or viral persistence and are influenced by viral proteins, HCV-quasispecies and several metabolic factors regulating liver metabolism. HCV pathogenesis is a very complex phenomenon and requires further study to determine the other factors involved.

The natural killer cell response to HCV infection

In the last few years major progress has been made in better understanding the role of natural killer (NK) cells in hepatitis C virus (HCV) infection. This includes multiple pathways by which HCV impairs or limits NK cells activation. Based on current genetic and functional data, a picture is emerging where only a rapid and strong NK cell response early on during infection which results in strong T cell responses and possible subsequent clearance, whereas chronic HCV infection is associated with dysfunctional or biased NK cells phenotypes. The hallmark of this NK cell dysfunction is persistent activation promoting ongoing hepatitis and hepatocyte damage, while being unable to clear HCV due to impaired IFN-γ responses. Furthermore, some data suggests certain chronically activated subsets that are NKp46^high may be particularly active against hepatic stellate cells, a key player in hepatic fibrogenesis. Finally, the role of NK cells during HCV therapy, HCV recurrence after liver transplant and hepatocellular carcinoma are discussed.