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.

Response of host inflammasomes to viral infection

Inflammasomes are multiprotein complexes that induce downstream immune responses to specific pathogens, environmental stimuli, and host cell damage. Components of specific viruses activate different inflammasomes; for example, the influenza A virus M2 protein and encephalomyocarditis virus (EMCV) 2B protein activate the nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain (PYD)-containing 3 (NLRP3) inflammasome, whereas viral double-stranded RNA (dsRNA) activates the retinoic acid inducible gene-I (RIG-I) inflammasome. Once activated in response to viral infection, inflammasomes induce the activation of caspases and the release of mature forms of interleukin-1β (IL-1β) and IL-18. Here we review the association between viral infection and inflammasome activation. Identifying the mechanisms underlying virus-induced inflammasome activation is important if we are to develop novel therapeutic strategies to target viruses.

Retention and tolerance of autoreactive CD4(+) recent thymic emigrants in the liver

Mechanisms of peripheral tolerance play a critical role in preventing T cells that escape from negative selection in the thymus from initiating autoimmune reactions. To investigate the site of peripheral tolerance induction, we examined migration and activation of recent thymic emigrants (RTEs) in liver, spleen, lymph node and peripheral blood. We show that a fraction of RTE precursors were retained in the liver independent of the secondary lymphoid organs. Compared to RTEs from the lymph nodes, RTEs from the liver proliferated more and many exhibited an activated phenotype with the capability of producing IL-10 upon activation. Liver RTEs also responded poorly to interleukin (IL)-7 and were more prone to apoptosis. Following transfer into RAG(-/-) recipients, liver RTEs induced more severe inflammation and T cell infiltration in the lung and colon. The extrathymic expression of MHC and Aire is required for the acquisition of tolerogenic phenotype of newly generated thymic emigrants in the liver. These results suggest that the liver is the first checkpoint in the periphery to filter, retain, and enforce tolerance to autoreactive CD4(+) thymic emigrants that escape from negative selection.

HBV and the immune response

Hepatitis B virus (HBV) infection acquired in adult life is generally self-limited while chronic persistence of the virus is the prevalent outcome when infection is acquired perinatally. Both control of infection and liver cell injury are strictly dependent upon protective immune responses, because hepatocyte damage is the price that the host must pay to get rid of intracellular virus. Resolution of acute hepatitis B is associated with functionally efficient, multispecific antiviral T-cell responses which are preceded by a poor induction of intracellular innate responses at the early stages of infection. Persistent control of infection is provided by long-lasting protective memory, which is probably sustained by continuous stimulation of the immune system by trace amounts of virus which are never totally eliminated, persisting in an occult episomic form in the nucleus of liver cells even after recovery from acute infection. Chronic virus persistence is instead characterized by a lack of protective T-cell memory maturation and by an exhaustion of HBV-specific T-cell responses. Persistent exposure of T cells to high antigen loads is a key determinant of functional T-cell impairment but also other mechanisms can contribute to T-cell inhibition, including the tolerogenic effect of the liver environment. The degree of T-cell impairment is variable and its severity is related to the level of virus replication and antigen load. The antiviral T-cell function is more efficient in patients who can control infection either partially, such as inactive HBsAg carriers with low levels of virus replication, or completely, such as patients who achieve HBsAg loss either spontaneously or after antiviral therapy. Thus, understanding the features of the immune responses associated with control of infection is needed for the successful design of novel immune modulatory therapies based on the reconstitution of efficient antiviral responses in chronic HBV patients.

A retrospective observational study to assess adverse transfusion reactions of patients with and without prior transfusion history

BACKGROUND AND OBJECTIVES

This study compares the frequency of adverse transfusion reactions (ATRs) after first transfusions with the frequency of ATRs for subsequent (non-first) transfusions.

MATERIALS AND METHODS

Five hospitals agreed to systematically collect and share 2 years of data. This was a retrospective observational analysis of data including the number of transfusion episodes and ATRs for red blood cells (RBCs), fresh frozen plasma (FFP) and platelet concentrates (PCs) given to first-time transfusion recipients and to those previously transfused.

RESULTS

First transfusion ATRs to RBCs, FFP and PCs were 1.08%, 2.84% and 3.34%, respectively. These are higher than ATR incidences to RBCs (0.69%), FFP (1.91%) and PCs (2.75%) on subsequent transfusions. Specifically, first transfusion incidences of febrile non-haemolytic transfusion reactions (FNHTRs) to RBCs (0.43%) and allergic reactions to FFP (2.51%) were higher than on subsequent transfusions (RBCs: 0.23%, FFP: 1.65%).

CONCLUSION

There are risks of ATRs on the first transfusion as well as transfusions of patients with transfusion history.

Impact of hepatitis C seropositivity on the risk of coronary heart disease events

Chronic infections have been shown to enhance atherogenicity. However, the association between chronic hepatitis C (HCV) and coronary heart disease (CHD) remains controversial. We examined the risk for CHD events in patients with HCV with an emphasis on the risk of CHD events with active infection. We conducted a retrospective cohort study using the Enterprise Data Warehouse at the University of Arkansas for Medical Sciences. HCV positive and negative patients were identified based on serology and incident CHD events were studied. Patient characteristics at entry were compared either by analysis of variance/F-test (continuous variables) or by a Chi-squared test (categorical variables). The joint effect of risk factors for incident CHD was evaluated using logistic regression. A total of 8,251 HCV antibody positive, 1,434 HCV RNA positive and 14,799 HCV negative patients were identified. HCV antibody and RNA positive patients had a higher incidence of hypertension, diabetes mellitus, obesity and chronic lung disease, but lower serum cholesterol levels compared to HCV negative patients (p< 0.001). HCV seropositive patients had a higher incidence of CHD events when compared to controls (4.9% vs. 3.2%, p<0.001). In the HCV cohort, patients with detectable HCV RNA had a significantly higher incidence of CHD events when compared to patients who were only HCV antibody positive with no detectable RNA (5.9% vs. 4.7%, p=0.04). In multivariate logistic regression analysis, both HCV antibody positivity (OR 1.32, 95% CI 1.09-1.60, p<0.001) and HCV RNA positivity (OR 1.59, 95% CI 1.13-2.26, p<0.001) were independent risk factors for incident CHD events. In conclusion, there is increased incidence of CHD events in HCV seropositive patients and the incidence is much higher in patients with detectable HCV RNA when compared to patients with remote infection who are only antibody positive. Lipid profile does not appear to be a good cardiovascular risk stratification tool in HVC patients.

Hepatitis C Virus. Strategies to Evade Antiviral Responses

Hepatitis C virus (HCV) causes chronic liver disease and poses a major clinical and economic burden worldwide. HCV is an RNA virus that is sensed as non-self in the infected liver by host pattern recognition receptors, triggering downstream signaling to interferons (IFNs). The type III IFNs play an important role in immunity to HCV, and human genetic variation in their gene loci is associated with differential HCV infection outcomes. HCV evades host antiviral innate immune responses to mediate a persistent infection in the liver. This review focuses on anti-HCV innate immune sensing, innate signaling and effectors, and the processes and proteins used by HCV to evade and regulate host innate immunity.

T cell responses in hepatitis C virus infection: historical overview and goals for future research

Hepatitis C virus (HCV)-specific T cells are key factors in the outcome of acute HCV infection and in protective immunity. This review recapitulates the steps that immunologists have taken in the past 25years to dissect the role of T cell responses in HCV infection. It describes technical as well as disease-specific challenges that were caused by the inapparent onset of acute HCV infection, the difficulty to identify subjects who spontaneously clear HCV infection, the low frequency of HCV-specific T cells in the blood of chronically infected patients, and the lack of small animal models with intact immune systems to study virus-host interaction. The review provides a historical perspective on techniques and key findings, and identifies areas for future research.

Contribution of Toll-like receptors to the control of hepatitis B virus infection by initiating antiviral innate responses and promoting specific adaptive immune responses

It is well accepted that adaptive immunity plays a key role in the control of hepatitis B virus (HBV) infection. In contrast, the contribution of innate immunity has only received attention in recent years. Toll-like receptors (TLRs) sense pathogen-associated molecule patterns and activate antiviral mechanisms, including intracellular antiviral pathways and the production of antiviral effector interferons (IFNs) and pro-inflammatory cytokines. Experimental results from in vitro and in vivo models have demonstrated that TLRs mediate the activation of cellular signaling pathways and the production of antiviral cytokines, resulting in a suppression of HBV replication. However, HBV infection is associated with downregulation of TLR expression on host cells and blockade of the activation of downstream signaling pathways. In primary HBV infection, TLRs may slow down HBV infection, but contribute only indirectly to viral clearance. Importantly, TLRs may modulate HBV-specific T- and B-cell responses in vivo, which are essential for the termination of HBV infection. Thus, TLR agonists are promising candidates to act as immunomodulators for the treatment of chronic HBV infection. Antiviral treatment may recover TLR expression and function in chronic HBV infection and may increase the efficacy of therapeutic approaches based on TLR activation. A combined therapeutic strategy with antiviral treatment and TLR activation could facilitate the restoration of HBV-specific immune responses and thereby, achieve viral clearance in chronically infected HBV patients.

CD161+ MAIT cells are severely reduced in peripheral blood and lymph nodes of HIV-infected individuals independently of disease progression

Mucosal-associated invariant T (MAIT) cells are characterized by the combined expression of the semi-invariant T cell receptor (TCR) Vα7.2, the lectin receptor CD161, as well as IL-18R, and play an important role in antibacterial host defense of the gut. The current study characterized CD161⁺ MAIT and CD161^–TCRVα7.2⁺ T cell subsets within a large cohort of HIV patients with emphasis on patients with slow disease progression and elite controllers. Mononuclear cells from blood and lymph node samples as well as plasma from 63 patients and 26 healthy donors were analyzed by multicolor flow cytometry and ELISA for IL-18, sCD14 and sCD163. Additionally, MAIT cells were analyzed after in vitro stimulation with different cytokines and/or fixed E.coli. Reduced numbers of CD161⁺ MAIT cells during HIV infection were detectable in the blood and lymph nodes of all patient groups, including elite controllers. CD161⁺ MAIT cell numbers did not recover even after successful antiretroviral treatment. The loss of CD161⁺ MAIT cells was correlated with higher levels of MAIT cell activation; an increased frequency of the CD161^–TCRVα7.2⁺T cell subset in HIV infection was observed. In vitro stimulation of MAIT cells with IL-18 and IL-12, IL-7 and fixed E.coli also resulted in a rapid and additive reduction of the MAIT cell frequency defined by CD161, IL-18R and CCR6. In summary, the irreversible reduction of the CD161⁺ MAIT cell subset seems to be an early event in HIV infection that is independent of later stages of the disease. This loss appears to be at least partially due to the distinctive vulnerability of MAIT cells to the pronounced stimulation by microbial products and cytokines during HIV-infection.

Dissecting the dendritic cell controversy in chronic hepatitis B virus infection

Therapeutic vaccines to boost endogenous T-cell immunity rely on the stimulatory capacity of dendritic cells (DCs). The functionality of DCs in chronic hepatitis B virus (HBV) infection has been a long-standing debate. Therefore, we have attempted to summarize multiple studies investigating DC function in chronic HBV patients to determine whether common observations can be drawn. We found that the frequency and function of ex vivo-tested myeloid and plasmacytoid DCs were largely intact in patients with HBV infection and similar to those of healthy donor DCs. The main exception was reduced IFN-α production by plasmacytoid DC from chronic HBV patients. This reduced IFN-α production correlated with liver inflammation in multiple studies but not with viral load, suggesting that viral antigens have little effect on DC function. The majority of the confusion about DC function arises from studies reporting the reduced function of healthy donor DCs exposed to various sources of HBV in vitro. These direct effects of viral antigens are in contrast to data from HBV-infected patients. The variations in the assays used and areas that require further investigation are also covered.

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.

Daclatasvir-like inhibitors of NS5A block early biogenesis of hepatitis C virus-induced membranous replication factories, independent of RNA replication

BACKGROUND & AIMS

Direct-acting antivirals that target nonstructural protein 5A (NS5A), such as daclatasvir, have high potency against the hepatitis C virus (HCV). They are promising clinical candidates, yet little is known about their antiviral mechanisms. We investigated the mechanisms of daclatasvir derivatives.

METHODS

We used a combination of biochemical assays, in silico docking models, and high-resolution imaging to investigate inhibitor-induced changes in properties of NS5A, including its interaction with phosphatidylinositol-4 kinase IIIα and induction of the membranous web, which is the site of HCV replication. Analyses were conducted with replicons, infectious virus, and human hepatoma cells that express a HCV polyprotein. Studies included a set of daclatasvir derivatives and HCV variants with the NS5A inhibitor class-defining resistance mutation Y93H.

RESULTS

NS5A inhibitors did not affect NS5A stability or dimerization. A daclatasvir derivative interacted with NS5A and molecular docking studies revealed a plausible mode by which the inhibitor bound to NS5A dimers. This interaction was impaired in mutant forms of NS5A that are resistant to daclatavir, providing a possible explanation for the reduced sensitivity of the HCV variants to this drug. Potent NS5A inhibitors were found to block HCV replication by preventing formation of the membranous web, which was not linked to an inhibition of phosphatidylinositol-4 kinase IIIα. Correlative light-electron microscopy revealed unequivocally that NS5A inhibitors had no overall effect on the subcellular distribution of NS5A, but completely prevented biogenesis of the membranous web.

CONCLUSIONS

Highly potent inhibitors of NS5A, such as daclatasvir, block replication of HCV RNA at the stage of membranous web biogenesis-a new paradigm in antiviral therapy.

Virology and cell biology of the hepatitis C virus life cycle: an update

Hepatitis C virus (HCV) is an important human pathogen that causes hepatitis, liver cirrhosis and hepatocellular carcinoma. It imposes a serious problem to public health in the world as the population of chronically infected HCV patients who are at risk of progressive liver disease is projected to increase significantly in the next decades. However, the arrival of new antiviral molecules is progressively changing the landscape of hepatitis C treatment. The search for new anti-HCV therapies has also been a driving force to better understand how HCV interacts with its host, and major progresses have been made on the various steps of the HCV life cycle. Here, we review the most recent advances in the fast growing knowledge on HCV life cycle and interaction with host factors and pathways.

Mucosal-associated invariant T-cells: new players in anti-bacterial immunity

Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population involved in anti-bacterial immunity. In human beings, MAIT cells are abundant, comprising ~10% of the CD8⁺ T-cell compartment in blood. They are enriched at mucosal sites and are particularly prevalent within the liver. MAIT cells are defined by the expression of a semi-invariant T-cell receptor (Vα7.2-Jα33/12/20) and are restricted by the non-polymorphic, highly evolutionarily conserved MHC class Ib molecule, MHC-related protein (MR)1. MR1 has recently been shown to present an unstable pyrimidine intermediate derived from a biosynthetic precursor of riboflavin; riboflavin biosynthesis occurs in many bacteria but not in human beings. Consistent with this, MAIT cells are responsive to riboflavin-metabolizing bacteria, including Salmonella. In mouse models, MAIT cells have been shown to play a non-redundant role in anti-bacterial immunity, including against Escherichia coli, Klebsiella pneumoniae, and Mycobacterium bovis BCG. In human beings, MAIT cells are decreased in frequency in the blood of patients with tuberculosis or pneumonia, and their frequency has been inversely correlated with the risk of subsequent systemic bacterial infection in patients in intensive care. Intriguingly, MAIT cells are also depleted from the blood early in HIV infection and fail to recover with anti-retroviral therapy, which may contribute to the susceptibility of patients infected with HIV to certain bacterial infections, including non-typhoidal Salmonella. In this review, we will discuss what is currently known about MAIT cells, the role that Salmonella has played in elucidating MAIT cell restriction and function, and the role MAIT cells might play in the control of Salmonella infection.

Age-Dependent Immune Events during HBV Infection from Birth to Adulthood: An Alternative Interpretation

Immune responses change during the life of an individual. While this concept has been well accepted for adaptive immunity, only recently it is becoming clear that the innate immune responses also acquire distinct features in different phases of life. We believe that this concept can offer a different interpretation of the pathological manifestations that can be observed in HBV-infected subjects during the patient’s life. Here, we will review the age-related immunopathological features of HBV infection and discuss how the different virological and clinical manifestations might be linked to the developmental pathway of the immune system from newborns to adults. We will discuss how the age of patients can affect the degree of inflammatory responses, but not the levels of antiviral specific immunity. We then propose that the different clinical manifestations occurring during the natural history of HBV infection are related to the host ability to trigger an inflammatory immune response.

Comparison of LAIR-1 genetic pathways in murine vs human internal organs

Growing evidence suggests that defective expression or dysfunction of LAIR-1, a novel immunoinhibitory receptor for collagen, is closely associated with some autoimmune diseases, cancers, as well as viral infections. We analyzed the variation of LAIR-1 genetic pathways in murine versus human internal organs, including the lung and brain. The results showed that, under physiological conditions, LAIR-1 links more closely to the common genes in mouse than in human, which poses tissue specificity. It means that mice experimental data in relation to the role of LAIR-1 immune regulation may be overestimated when applied to assess human conditions. Moreover, we found that the in vivo interaction of LAIR-1 with LAIR-2 rarely occurs, implying that the species difference in LAIR-1 genetic pathways could not be primarily attributed to the existence of human LAIR-2. In summary, this study opens the door for insight into LAIR-1 functions inside the human body, and raises concern as to extrapolative credibility of the murine model in biomedical research.

Isoliquiritigenin is a potent inhibitor of NLRP3 inflammasome activation and diet-induced adipose tissue inflammation

Inflammasome activation initiates the development of many inflammatory diseases, including obesity and type 2 diabetes. Therefore, agents that target discrete activation steps could represent very important drugs. We reported previously that ILG, a chalcone from Glycyrrhiza uralensis, inhibits LPS-induced NF-κB activation. Here, we show that ILG potently inhibits the activation of NLRP3 inflammasome, and the effect is independent of its inhibitory potency on TLR4. The inhibitory effect of ILG was stronger than that of parthenolide, a known inhibitor of the NLRP3 inflammasome. GL, a triterpenoid from G. uralensis, had similar inhibitory effects on NLRP3 activity, but high concentrations of GL were required. In contrast, activation of the AIM2 inflammasome was inhibited by GL but not by ILG. Moreover, GL inhibited NLRP3- and AIM2-activated ASC oligomerization, whereas ILG inhibited NLRP3-activated ASC oligomerization. Low concentrations of ILG were highly effective in IAPP-induced IL-1β production compared with the sulfonylurea drug glyburide. In vivo analyses revealed that ILG potently attenuated HFD-induced obesity, hypercholesterolemia, and insulin resistance. Furthermore, ILG treatment improved HFD-induced macrovesicular steatosis in the liver. Finally, ILG markedly inhibited diet-induced adipose tissue inflammation and IL-1β and caspase-1 production in white adipose tissue in ex vivo culture. These results suggest that ILG is a potential drug target for treatment of NLRP3 inflammasome-associated inflammatory diseases.

The role of oxidative stress during inflammatory processes

Abstract The production of various reactive oxidant species in excess of endogenous antioxidant defense mechanisms promotes the development of a state of oxidative stress, with significant biological consequences. In recent years, evidence has emerged that oxidative stress plays a crucial role in the development and perpetuation of inflammation, and thus contributes to the pathophysiology of a number of debilitating illnesses, such as cardiovascular diseases, diabetes, cancer, or neurodegenerative processes. Oxidants affect all stages of the inflammatory response, including the release by damaged tissues of molecules acting as endogenous danger signals, their sensing by innate immune receptors from the Toll-like (TLRs) and the NOD-like (NLRs) families, and the activation of signaling pathways initiating the adaptive cellular response to such signals. In this article, after summarizing the basic aspects of redox biology and inflammation, we review in detail the current knowledge on the fundamental connections between oxidative stress and inflammatory processes, with a special emphasis on the danger molecule high-mobility group box-1, the TLRs, the NLRP-3 receptor, and the inflammasome, as well as the transcription factor nuclear factor-κB.

The role of Kupffer cells in hepatitis B and hepatitis C virus infections

Globally, over 500 million people are chronically infected with the hepatitis B virus (HBV) or hepatitis C virus (HCV). These chronic infections cause liver inflammation, and may result in fibrosis/cirrhosis or hepatocellular carcinoma. Albeit that HBV and HCV differ in various aspects, clearance, persistence, and immunopathology of either infection depends on the interplay between the innate and adaptive responses in the liver. Kupffer cells, the liver-resident macrophages, are abundantly present in the sinusoids of the liver. These cells have been shown to be crucial players to maintain homeostasis, but also contribute to pathology. However, it is important to note that especially during pathology, Kupffer cells are difficult to distinguish from infiltrating monocytes/macrophages and other myeloid cells. In this review we discuss our current understanding of Kupffer cells, and assess their role in the regulation of anti-viral immunity and disease pathogenesis during HBV and HCV infection.

Restoration of HCV-specific CD8+ T cell function by interferon-free therapy

BACKGROUND & AIMS

Chronic hepatitis C virus (HCV) infection is characterised by a failure of virus-specific CD8+ T cells that is mainly caused by viral escape and T cell exhaustion. Constant antigen stimulation has been suggested to contribute to HCV-specific CD8+ T cell exhaustion. However, IFN-based therapies failed to recover HCV-specific CD8+ T cell function suggesting that the damage to CD8+ T cells may be permanent even after antigen removal. It was therefore the objective of this study to analyse the impact of inhibition of ongoing viral replication by IFN-free therapy with direct acting antivirals (DAA) on the phenotype and function of HCV-specific CD8+ T cells.

METHODS

Virus-specific CD8+ T cells obtained from a patient cohort of 51 previously untreated chronically infected patients undergoing IFN-free therapy with a combination of faldaprevir (a protease inhibitor) and deleobuvir (a non-nucleoside polymerase inhibitor) with or without ribavirin were analysed ex vivo and after in vitro expansion at baseline, wk4, wk 12, and after treatment.

RESULTS

Our results show the rapid restoration of proliferative HCV-specific CD8+ T cells in the majority of patients with SVR12 within 4 weeks of therapy suggesting that IFN-free therapy mediated antigen removal may restore CD8+ T cell function.

CONCLUSIONS

This study indicates a specific restoration of proliferative HCV-specific CD8+ T cells under IFN-free therapy. This is in contrast to PegIFN-based therapies that have been shown not to restore T cell function during and after chronic infection.

The immune tolerant phase of chronic HBV infection: new perspectives on an old concept

Chronic hepatitis B virus (HBV) infection progresses through distinct disease phases that are strongly associated with patient age. The so-called immune tolerant (IT) phase represents the classical early phase of infection; it is associated with high levels of HBV replication and lack of clinical signs of liver Inflammation. Whether this phase of HBV infection is also associated with immunological features of "tolerance' has recently been challenged. Here, we review the data that dispute this concept of immune tolerance and then propose an alternative interpretation of the immunopathological events that take place during this early phase of CHB infection.

Harnessing the antibacterial and immunological properties of mucosal-associated invariant T cells in the development of novel oral vaccines against enteric infections

Enteric infections are a major cause of mortality and morbidity with significant social and economic implications worldwide and particularly in developing countries. An attractive approach to minimizing the impact of these diseases is via the development of oral vaccination strategies. However, oral vaccination is challenging due to the tolerogenic and hyporesponsive nature of antigen presenting cells resident in the gastrointestinal tract. The inclusion of adjuvants in oral vaccine formulations has the potential to overcome this challenge. To date no oral adjuvants have been licenced for human use and thus oral adjuvant discovery remains a key goal in improving the potential for oral vaccine development. Mucosal-associated invariant T (MAIT) cells are a recently discovered population of unconventional T cells characterized by an evolutionarily conserved αβ T cell receptor (TCR) that recognizes antigens presented by major histocompatibility complex (MHC) class I-related (MR1) molecule. MAIT cells are selected intra-thymically by MR1 expressing double positive thymocytes and enter the circulation with a naïve phenotype. In the circulation they develop a memory phenotype and are programmed to home to mucosal tissues and the liver. Once resident in these tissues, MAIT cells respond to bacterial and yeast infections through the production of chemokines and cytokines that aid in the induction of an adaptive immune response. Their abundance in the gastrointestinal tract and ability to promote adaptive immunity suggests that MAIT cell activators may represent attractive novel adjuvants for use in oral vaccination.

Enrichment of LAG-3, but not PD-1, on double negative T cells at the female genital tract

PROBLEM

The expression of inhibitory markers such as LAG-3 and PD-1 on T lymphocytes regulates immune function. Their expression at the genital mucosa is poorly understood, but regulation of immune activation at the female genital tract likely controls susceptibility to sexually transmitted infections.

METHOD OF STUDY

Cervical mononuclear cells were phenotyped by flow cytometry. Concentrations of cytokines were determined in cervical-vaginal lavage samples by bead array.

RESULTS

LAG-3 expression was significantly elevated at the genital mucosa and was associated with expression of CCR5 and CD69. Double negative (DN) T cells expressed the highest levels of LAG-3, but not PD-1, and were more activated than other T lymphocytes.

CONCLUSION

The elevated expression of LAG-3 at the genital tract suggests it may regulate T-cell activation, and identify cells susceptible to HIV infection. The enrichment of LAG-3 on DN T cells suggests LAG-3 may contribute to the immunoregulatory activity of these cells.

CD27(+)CD56Bright natural killer cells may be involved in spontaneous clearance of acute hepatitis C in HIV-positive patients

OBJECTIVE

The objective of this study was to analyse the potential role of CD27 in natural killer (NK) cell-mediated control of hepatitis C virus (HCV) infection in HIV-positive patients.

DESIGN

Frequency of CD27-expressing CD56 NK cells was analysed in HIV mono-infected individuals and HIV-positive patients with acute or chronic hepatitis C. Anti-HCV activity of CD27(+) and CD27(-) NK cells was compared.

METHODS

NK cell mediated inhibition of HCV replication was analysed using the HUH7 HCV Replicon model. NK cell phenotype and interferon (IFN) secretion was studied by flowcytometry.

RESULTS

High frequency of CD27(+)CD56 NK cells is associated with spontaneous clearance of acute hepatitis C in HIV-positive patients. Accordingly, we found CD27(+)CD56 NK cells to display strong anti-HCV activity.

CONCLUSION

Our results underline the important role of NK cells in modulating outcome of HCV infection.

Contradictory immune response in post liver transplantation hepatitis B and C

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

Classical swine fever virus and p7 protein induce secretion of IL-1β in macrophages

Classical swine fever virus (CSFV) has a tropism for vascular endothelial cells and immune system cells. The process and release of pro-inflammatory cytokines, including IL-1β and IL-18, is one of the fundamental reactions of the innate immune response to viral infection. In this study, we investigated the production of IL-1β from macrophages following CSFV infection. Our results showed that IL-1β was upregulated after CSFV infection through activating caspase-1. Subsequent studies demonstrated that reactive oxygen species may not be involved in CSFV-mediated IL-1β release. Recently, research has indicated a novel mechanism by which inflammasomes are triggered through detection of activity of viroporin. We further demonstrated that CSFV viroporin p7 protein induced IL-1β secretion which could be inhibited by the ion channel blocker amantadine and also discovered that p7 protein was a short-lived protein degraded by the proteasome. Together, our observations provided an insight into the mechanism of CSFV-induced inflammatory responses.

In situ characterization of intrahepatic non-parenchymal cells in PSC reveals phenotypic patterns associated with disease severity

Liver-infiltrating T cells have been implicated in the pathogenesis of primary sclerosing cholangitis (PSC), however little information is available about changes in other cellular compartments in the liver during PSC. This study aimed to characterize non-parenchymal intrahepatic cells in PSC livers and to find associations between phenotypes and disease severity. Using immunohistochemistry, followed by automated image analysis and quantification and a principal component analysis, we have studied non-parenchymal intrahepatic cells in PSC-patient livers (n = 17) and controls (n = 17). We observed a significant increase of T cells in the PSC patients, localized to the fibrotic areas. MAIT cells, normally present at high numbers in the liver, were not increased to the same extent. PSC patients had lower expression of MHC class I than controls. However, the levels of NKp46+ NK cells were similar between patients and controls, nevertheless, NKp46 was identified as a phenotypic marker that distinguished PSC patients with mild from those with severe fibrosis. Beyond that, a group of PSC patients had lost expression of Caldesmon and this was associated with more extensive bile duct proliferation and higher numbers of T cells. Our data reveals phenotypic patterns in PSC patients associated with disease severity.

Hepatitis C virus core protein enhances HIV-1 replication in human macrophages through TLR2, JNK, and MEK1/2-dependent upregulation of TNF-α and IL-6

Despite their differential cell tropisms, HIV-1 and HCV dramatically influence disease progression in coinfected patients. Macrophages are important target cells of HIV-1. We hypothesized that secreted HCV core protein might modulate HIV-1 replication. We demonstrate that HCV core significantly enhances HIV-1 replication in human macrophages by upregulating TNF-α and IL-6 via TLR2-, JNK-, and MEK1/2-dependent pathways. Furthermore, we show that TNF-α and IL-6 secreted from HCV core-treated macrophages reactivates monocytic U1 cells latently infected with HIV-1. Our studies reveal a previously unrecognized role of HCV core by enhancing HIV-1 infection in macrophages.

Cellular visualization of macrophage pyroptosis and interleukin-1β release in a viral hemorrhagic infection in zebrafish larvae

Hemorrhagic viral diseases are distributed worldwide with important pathogens, such as dengue virus or hantaviruses. The lack of adequate in vivo infection models has limited the research on viral pathogenesis and the current understanding of the underlying infection mechanisms. Although hemorrhages have been associated with the infection of endothelial cells, other cellular types could be the main targets for hemorrhagic viruses. Our objective was to take advantage of the use of zebrafish larvae in the study of viral hemorrhagic diseases, focusing on the interaction between viruses and host cells. Cellular processes, such as transendothelial migration of leukocytes, virus-induced pyroptosis of macrophages. and interleukin-1β (Il-1β) release, could be observed in individual cells, providing a deeper knowledge of the immune mechanisms implicated in the disease. Furthermore, the application of these techniques to other pathogens will improve the current knowledge of host-pathogen interactions and increase the potential for the discovery of new therapeutic targets. Importance: Pathogenic mechanisms of hemorrhagic viruses are diverse, and most of the research regarding interactions between viruses and host cells has been performed in cell lines that might not be major targets during natural infections. Thus, viral pathogenesis research has been limited because of the lack of adequate in vivo infection models. The understanding of the relative pathogenic roles of the viral agent and the host response to the infection is crucial. This will be facilitated by the establishment of in vivo infection models using organisms such as zebrafish, which allows the study of the diseases in the context of a complete individual. The use of this animal model with other pathogens could improve the current knowledge on host-pathogen interactions and increase the potential for the discovery of new therapeutic targets against diverse viral diseases.

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.

The risk of placental abruption and placenta previa in pregnant women with chronic hepatitis B viral infection: a systematic review and meta-analysis

INTRODUCTION

Several epidemiological studies have found a positive association between chronic hepatitis B virus (CHB) infection and the risk of placental abruption and placenta previa, but various studies have reported conflicting findings. The objective was to systematically review the literature to determine a possible association between CHB infection and these two placental complications.

METHODS

We conducted a computerized search in electronic database through March 1, 2014, supplemented with a manual search of reference lists, to identify original published research on placental abruption and placenta previa rates in women with CHB infection. Data were independently extracted, and relative risks were calculated. The meta-analysis was performed using Stata version 10.0 software.

RESULTS

Five studies involving 9088 placenta previa cases were identified. No significant association between CHB infection and placenta previa was identified (OR = 0.98, 95% CI = 0.60-1.62). Five studies involving 15571 placental abruption cases were identified. No significant association between CHB infection and placental abruption was identified (OR = 1.42, 95% CI, 0.93-2.15).

DISCUSSION

The immune response against the virus represents a key factor in determining infection outcomes. No observation of significant increased risk of the placental complications could be partially explained by the complex immune response during CHB infection.

CONCLUSIONS

Our meta-analysis found no evidence of significant associations between CHB infection and increased risk of placental abruption as well as placenta previa. Further well-designed studies were warranted to assess any potential association between CHB infection and increased risk of placental abruption as well as placenta previa.

Nonclassical T cells and their antigens in tuberculosis

T cells that recognize nonpeptidic antigens, and thereby are identified as nonclassical, represent important yet poorly characterized effectors of the immune response. They are present in large numbers in circulating blood and tissues and are as abundant as T cells recognizing peptide antigens. Nonclassical T cells exert multiple functions including immunoregulation, tumor control, and protection against infections. They recognize complexes of nonpeptidic antigens such as lipid and glycolipid molecules, vitamin B2 precursors, and phosphorylated metabolites of the mevalonate pathway. Each of these antigens is presented by antigen-presenting molecules other than major histocompatibility complex (MHC), including CD1, MHC class I-related molecule 1 (MR1), and butyrophilin 3A1 (BTN3A1) molecules. Here, we discuss how nonclassical T cells participate in the recognition of mycobacterial antigens and in the mycobacterial-specific immune response.

Chronic hepatitis B virus in young adults: the need for new approaches to management

One in four patients infected with hepatitis B virus (HBV) at birth or in early childhood will develop cirrhosis or hepatocellular carcinoma. Historically, guidelines have overlooked treatment in young people, as the immune tolerant disease phase is considered synonymous with chronic infection in the young. Current treatment aims to suppress HBV replication through long-term nucleos(t)ide therapy with little emphasis on virus eradication. To achieve HBsAg loss, it is accepted that effective immune control of virus is required, mimicking that seen in those who resolve acute HBV infection. We have recently challenged the accuracy of a generic immune tolerant state in young people, thus raising a potential role for earlier treatment. Here we report on our immunological analysis of HBV in young people and the role of a dedicated clinic; we make the case for earlier intervention to achieve effective immune control leading to better outcomes.

Prolactin prevents hepatocellular carcinoma by restricting innate immune activation of c-Myc in mice

Women are more resistant to hepatocellular carcinoma (HCC) than men despite equal exposure to major risk factors, such as hepatitis B or C virus infection. Female resistance is hormone-dependent, as evidenced by the sharp increase in HCC incidence in postmenopausal women who do not take hormone replacement therapy. In rodent models sex-dimorphic HCC phenotypes are pituitary-dependent, suggesting that sex hormones act via the gonadal-hypophyseal axis. We found that the estrogen-responsive pituitary hormone prolactin (PRL), signaling through hepatocyte-predominant short-form prolactin receptors (PRLR-S), constrained TNF receptor-associated factor (TRAF)-dependent innate immune responses invoked by IL-1β, TNF-α, and LPS/Toll-like receptor 4 (TLR4), but not TRIF-dependent poly(I:C)/TLR3. PRL ubiquitinated and accelerated poststimulatory decay of a "trafasome" comprised of IRAK1, TRAF6, and MAP3K proteins, abrogating downstream activation of c-Myc-interacting pathways, including PI3K/AKT, mTORC1, p38 MAPK, and NF-κB. Consistent with this finding, we documented exaggerated male liver responses to immune stimuli in mice and humans. Tumor promotion through, but regulation above, the level of c-Myc was demonstrated by sex-independent HCC eruption in Alb-Myc transgenic mice. PRL deficiency accelerated liver carcinogenesis in Prl(-/-) mice of both sexes. Conversely, pharmacologic PRL mobilization using the dopamine D2 receptor antagonist domperidone prevented HCC in tumor-prone C3H/HeN males. Viewed together, our results demonstrate that PRL constrains tumor-promoting liver inflammation by inhibiting MAP3K-dependent activation of c-Myc at the level of the trafasome. PRL-targeted therapy may hold promise for reducing the burden of liver cancer in high-risk men and women.

A molecular basis underpinning the T cell receptor heterogeneity of mucosal-associated invariant T cells

A novel MAIT cell antagonist, Ac-6-FP, stabilizes MR1 and can inhibit MAIT cell activation with the flexible TCR β-chain serving to fine-tune the affinity of the TCR for antigen-MR1 complexes.

Mucosal-associated invariant T (MAIT) cells express an invariant T cell receptor (TCR) α-chain (TRAV1-2 joined to TRAJ33, TRAJ20, or TRAJ12 in humans), which pairs with an array of TCR β-chains. MAIT TCRs can bind folate- and riboflavin-based metabolites restricted by the major histocompatibility complex (MHC)-related class I−like molecule, MR1. However, the impact of MAIT TCR and MR1-ligand heterogeneity on MAIT cell biology is unclear. We show how a previously uncharacterized MR1 ligand, acetyl-6-formylpterin (Ac-6-FP), markedly stabilized MR1, potently up-regulated MR1 cell surface expression, and inhibited MAIT cell activation. These enhanced properties of Ac-6-FP were attributable to structural alterations in MR1 that subsequently affected MAIT TCR recognition via conformational changes within the complementarity-determining region (CDR) 3β loop. Analysis of seven TRBV6-1⁺ MAIT TCRs demonstrated how CDR3β hypervariability impacted on MAIT TCR recognition by altering TCR flexibility and contacts with MR1 and the Ag itself. Ternary structures of TRBV6-1, TRBV6-4, and TRBV20⁺ MAIT TCRs in complex with MR1 bound to a potent riboflavin-based antigen (Ag) showed how variations in TRBV gene usage exclusively impacted on MR1 contacts within a consensus MAIT TCR-MR1 footprint. Moreover, differential TRAJ gene usage was readily accommodated within a conserved MAIT TCR-MR1-Ag docking mode. Collectively, MAIT TCR heterogeneity can fine-tune MR1 recognition in an Ag-dependent manner, thereby modulating MAIT cell recognition.

Host factor-targeted hepatitis B virus therapies

In this review we will focus on host factors known to impact hepatitis B virus (HBV) replication as current or potential targets for therapeutic intervention. Some immunotherapeutic strategies will be discussed because they have the potential to activate interferon-mediated clearance of HBV, but attention will also be paid to host machinery and proteins that silence covalently closed circular DNA, destabilize viral RNA, or disrupt entry and trafficking of HBV virions. Many of these are in the early stages of development, but may represent novel avenues to reduce HBV burden when combined with nucleos(t)ide analogues.

Type 1 interferon-induced IL-7 maintains CD8+ T-cell responses and homeostasis by suppressing PD-1 expression in viral hepatitis

Type 1 interferon (IFN-I) promotes antigen-presenting cell maturation and was recently shown to induce hepatic IL-7 production during infection. Herein, we further explored the underlying mechanisms used by IFN-I to orchestrate antiviral immune responses in the liver. Acute viral hepatitis was induced by i.v. injection of adenovirus (Ad) in IFN-α receptor knockout (IFNAR(-/-)) and control mice. To disrupt signaling, monoclonal antibodies (mAbs) against IL-7 receptor alpha (IL-7Rα) or PD-L1 were i.p. injected. We found that CD8(+) T cells in IFNAR(-/-) mice were less effective than those in control mice. The reduced T-cell function was accompanied by increased levels of PD-1 expression, apoptosis and decreased IFN-γ production. The lack of IFN-I signaling also impaired the expression of accessory molecules in both intrahepatic dendritic cell (DCs) and hepatocytes. PD-L1 was comparably and highly expressed on hepatocytes in both IFNAR(-/-) and control mice. Injection of PD-L1-specific mAb in IFNAR(-/-) mice reversed the compromised immune responses in the liver. Further investigation showed that hepatic IL-7 elevation was less pronounced in IFNAR(-/-) mice compared to the controls. A treatment with recombinant IL-7 suppressed PD-1 expression on CD8(+) T cells in vitro. Accordingly, blocking IL-7R signaling in vivo resulted in increased PD-1 expression on CD8(+) T cells in Ad-infected mice. Collectively, the results suggest that IFN-I-induced hepatic IL-7 production maintains antiviral CD8(+) T-cell responses and homeostasis by suppressing PD-1 expression in acute viral hepatitis.

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

Despite the development of potent antiviral drugs, HCV remains a global health problem; global eradication is a long way off. In this review, we discuss the immune response to HCV infection and particularly, the interplay between viral strategies that delay the onset of antiviral responses and host strategies that limit or even eradicate infected cells but also contribute to pathogenesis. Although HCV can disable some cellular virus-sensing machinery, IFN-stimulated antiviral genes are induced in the infected liver. Whereas epitope evolution contributes to escape from T cell-mediated immunity, chronic high antigen load may also blunt the T cell response by activating exhaustion or tolerance mechanisms. The evasive maneuvers of HCV limit sterilizing humoral immunity through rapid evolution of decoy epitopes, epitope masking, stimulation of interfering antibodies, lipid shielding, and cell-to-cell spread. Whereas the majority of HCV infections progress to chronic hepatitis with persistent viremia, at least 20% of patients spontaneously clear the infection. Most of these are protected from reinfection, suggesting that protective immunity to HCV exists and that a prophylactic vaccine may be an achievable goal. It is therefore important that we understand the correlates of protective immunity and mechanisms of viral persistence.

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.

How viruses use the immune system to promote infection of polarized cells

ABSTRACT: 

To establish infection and access bodily compartments including the gut, lung, liver and brain, viruses must traverse polarized epithelial and endothelial cell sheets. Many viruses use components of the immune system to successfully infect epithelial cells and gain access to underlying tissue. Recently, several reports have highlighted new and surprising ways by which viruses can hijack the immune system to invade polarized cells. This review will summarize recent advances in our understanding of how viruses interact with the immune system, and with polarized cells, for successful infection. These studies raise important questions about the design and screening of therapeutics and vaccines that activate the immune system, which may need to consider the role of immune cells and the inflammatory microenvironment.

Oxidative stress and hepatic Nox proteins in chronic hepatitis C and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common liver cancer and a leading cause of cancer-related mortality in the world. Hepatitis C virus (HCV) is a major etiologic agent of HCC. A majority of HCV infections lead to chronic infection that can progress to cirrhosis and, eventually, HCC and liver failure. A common pathogenic feature present in HCV infection, and other conditions leading to HCC, is oxidative stress. HCV directly increases superoxide and H2O2 formation in hepatocytes by elevating Nox protein expression and sensitizing mitochondria to reactive oxygen species generation while decreasing glutathione. Nitric oxide synthesis and hepatic iron are also elevated. Furthermore, activation of phagocytic NADPH oxidase (Nox) 2 of host immune cells is likely to exacerbate oxidative stress in HCV-infected patients. Key mechanisms of HCC include genome instability, epigenetic regulation, inflammation with chronic tissue injury and sustained cell proliferation, and modulation of cell growth and death. Oxidative stress, or Nox proteins, plays various roles in these mechanisms. Nox proteins also function in hepatic fibrosis, which commonly precedes HCC, and Nox4 elevation by HCV is mediated by transforming growth factor β. This review summarizes mechanisms of oncogenesis by HCV, highlighting the roles of oxidative stress and hepatic Nox enzymes in HCC.

Toll-like receptor 8 agonist and bacteria trigger potent activation of innate immune cells in human liver

The ability of innate immune cells to sense and respond to impending danger varies by anatomical location. The liver is considered tolerogenic but is still capable of mounting a successful immune response to clear various infections. To understand whether hepatic immune cells tune their response to different infectious challenges, we probed mononuclear cells purified from human healthy and diseased livers with distinct pathogen-associated molecules. We discovered that only the TLR8 agonist ssRNA40 selectively activated liver-resident innate immune cells to produce substantial quantities of IFN-γ. We identified CD161^Bright mucosal-associated invariant T (MAIT) and CD56^Bright NK cells as the responding liver-resident innate immune cells. Their activation was not directly induced by the TLR8 agonist but was dependent on IL-12 and IL-18 production by ssRNA40-activated intrahepatic monocytes. Importantly, the ssRNA40-induced cytokine-dependent activation of MAIT cells mirrored responses induced by bacteria, i.e., generating a selective production of high levels of IFN-γ, without the concomitant production of TNF-α or IL-17A. The intrahepatic IFN-γ production could be detected not only in healthy livers, but also in HBV- or HCV-infected livers. In conclusion, the human liver harbors a network of immune cells able to modulate their immunological responses to different pathogen-associated molecules. Their ability to generate a strong production of IFN-γ upon stimulation with TLR8 agonist opens new therapeutic opportunities for the treatment of diverse liver pathologies.

The ability of human pathogens, like HBV, HCV or Plasmodium spp. to infect the liver might be influenced by its tolerogenic features. However, hepatic tolerance is not absolute since protective immunity can be triggered. Our goal was to define how to deliberately elicit an intrahepatic protective immune response. To achieve this, we purified immune cells residing in the vascular bed of human livers and we probed their reactivity against different pathogen-associated molecules, mimicking signature components of viruses or bacteria. We found that robust production of anti-viral cytokine IFN-γ was induced only by the TLR8 agonist ssRNA40. Mechanistically, ssRNA40 triggered hepatic monocytes to produce IL-12 and IL-18 cytokines, which stimulated IFN-γ production by liver-resident CD161^Bright MAIT and CD56^Bright NK cells. We also demonstrated that ssRNA40-mediated activation could occur in pathologic (HBV- or HCV-chronically infected) livers and that a similar cytokine-mediated activation of intrahepatic cells could also be triggered upon bacterial infection. Thus, we showed that the liver immune cells can respond vigorously to specific pathogen-associated molecules. The selective production of IFN-γ by liver-resident cells could have therapeutic implications for the treatment of chronic liver infections.

Check MAIT

The evolutionary conservation of T lymphocyte subsets bearing αβ TCRs using invariant α-chains is indicative of unique and important functions. Among these T lymphocytes, NKT cells that express an invariant TCRα-chain and recognize lipid Ags presented by the nonclassical MHC class I molecule CD1d are probably the most studied. However, a new population of evolutionarily conserved T cells with another invariant TCRα rearrangement was recently characterized. These cells, which are very abundant in humans, tend to reside in mucosal tissues and, therefore, were named mucosal-associated invariant T (MAIT) cells. Until recently, little was known about MAIT cells; however, several recent advances in our understanding of MAIT cell characteristics and functions secure their upcoming rise to fame in the immunology field and in clinical practice.

HIV-1 infection induces interleukin-1β production via TLR8 protein-dependent and NLRP3 inflammasome mechanisms in human monocytes

The induction of inflammatory cytokines such as IL-1β is associated with the progression of human immunodeficiency virus, type 1 (HIV-1) disease or AIDS. Unlike most inflammatory cytokines that are regulated by NF-κB at the transcriptional level, production of mature IL-1β also depends on inflammasome activation. The mechanism by which HIV-1 induces pro-IL-1β expression and activates inflammasomes to cleave pro-IL-1β into its bioactive form is not clearly defined. We report here that HIV-1 infection in human monocytes efficiently induced IL-1β expression and inflammasome activation. Toll-like receptor 8 (TLR8) was required for inducing pro-IL-1β expression, whereas the NLRP3 inflammasome was required for IL-1β maturation and release. Furthermore, the lysosomal protease cathepsin B and HIV-1 induced production of reactive oxygen species were critical for HIV-induced inflammasome activation and IL-1β production. HIV-1 entry, reverse transcription, and integration were all required for both pro-IL-1β expression and inflammasome activation. Finally, we show that HIV-1-derived RNA was sufficient to induce both pro-IL-1β expression and inflammasome activation. We conclude that HIV-1 infection induced the expression of pro-IL-1β via TLR8-mediated mechanisms and activated caspase-1 through the NLRP3 inflammasome to cleave pro-IL-1β into bioactive IL-1β. These findings help to elucidate mechanisms of HIV-1 disease progression and identify novel targets for treating HIV-1 induced inflammation and immune activation.

Vasculitis: determinants of disease patterns

The vasculitides are a large group of heterogeneous diseases for which it has been assumed that pathogenesis is largely autoimmune. As clinicians, we distinguish one form of vasculitis from another on the basis of observed patterns of organ injury, the size of the vessels affected and histopathological findings. The terms 'small-vessel', 'medium-vessel' and 'large-vessel' vasculitis are useful clinical descriptors, but fail to inform us about why vessels of a certain calibre are favoured by one disease and not another. Classification based on vessel size also fails to consider that vessels of a specific calibre are not equally prone to injury. Distinct vulnerabilities undoubtedly relate to the fact that same-size vessels in different tissues may not be identical conduits. In fact, vessels become specialized, from the earliest stages of embryonic development, to suit the needs of different anatomical locations. Vessels of the same calibre in different locations and organs are as different as the organ parenchymal cells through which they travel. The dialogue between developing vessels and the tissues they perfuse is designed to meet special local needs. Added to the story of vascular diversity and vulnerability are changes that occur during growth, development and ageing. An improved understanding of the unique territorial vulnerabilities of vessels could form the basis of new hypotheses for the aetiopathogenesis of the vasculitides. This Review considers how certain antigens, including infectious agents, might become disease-relevant and how vascular diversity could influence disease phenotypes and the spectrum of vascular inflammatory diseases.

Role of cellular immunity in cow's milk allergy: pathogenesis, tolerance induction, and beyond

Food allergy is an aberrant immune-mediated reaction against harmless food substances, such as cow's milk proteins. Due to its very early introduction, cow's milk allergy is one of the earliest and most common food allergies. For this reason cow's milk allergy can be recognized as one of the first indications of an aberrant inflammatory response in early life. Classically, cow's milk allergy, as is true for most other allergies as well, is primarily associated with abnormal humoral immune responses, that is, elevation of specific immunoglobulin E levels. There is growing evidence indicating that cellular components of both innate and adaptive immunity play significant roles during the pathogenesis of cow's milk allergy. This is true for the initiation of the allergic phenotype (stimulation and skewing towards sensitization), development and outgrowth of the allergic disease. This review discusses findings pertaining to roles of cellular immunity in allergic inflammation, and tolerance induction against cow's milk proteins. In addition, a possible interaction between immune mechanisms underlying cow's milk allergy and other types of inflammation (infections and noncommunicable diseases) is discussed.