HBV pathogenesis in animal models: recent advances on the role of platelets

Blood-Borne Infection Prevention in Combat Sports: Position Statement of the Association of Ringside Physicians

ABSTRACT

The Association of Ringside Physicians (ARP) emphasizes the importance of screening combat sports athletes for blood-borne infections, including hepatitis B, HIV, and hepatitis C, to mitigate transmission risks and ensure participant safety. Although transmission of hepatitis B and C and HIV in combat sports is rare, protecting athletes is of utmost importance. It is the recommendation of the ARP that all fighters participating in combat sports, in which the presence of blood is a common occurrence and is allowed during competition, should undergo testing for HIV, hepatitis B (HBV), and hepatitis C (HCV). Testing should be conducted using serum samples, because rapid tests are not considered acceptable for accurate results. Testing for HBV, HCV, and HIV should optimally be done within 3 months of competition, but within 6 months is acceptable. Athletes whose tests suggest active HBV, HCV, or HIV infection should be disqualified from competition in sports where blood is common and allowed. Athletes with cured prior HCV infection may be cleared for competition in all combat sports. Athletes with prior HBV infection and no detectable HBV DNA in blood can be cleared for competition in all combat sports. Athletes with latent HBV infection with detectable HBV DNA in blood have a small risk of disease reactivation, so they should not be cleared.

Study on the mechanism of MDSC-platelets and their role in the breast cancer microenvironment

Myeloid-derived suppressor cells (MDSCs) are key immunosuppressive cells in the tumor microenvironment (TME) that play critical roles in promoting tumor growth and metastasis. Tumor-associated platelets (TAPs) help cancer cells evade the immune system and promote metastasis. In this paper, we describe the interaction between MDSCs and TAPs, including their generation, secretion, activation, and recruitment, as well as the effects of MDSCs and platelets on the generation and changes in the immune, metabolic, and angiogenic breast cancer (BC) microenvironments. In addition, we summarize preclinical and clinical studies, traditional Chinese medicine (TCM) therapeutic approaches, and new technologies related to targeting and preventing MDSCs from interacting with TAPs to modulate the BC TME, discuss the potential mechanisms, and provide perspectives for future development. The therapeutic strategies discussed in this review may have implications in promoting the normalization of the BC TME, reducing primary tumor growth and distant lung metastasis, and improving the efficiency of anti-tumor therapy, thereby improving the overall survival (OS) and progression-free survival (PFS) of patients. However, despite the significant advances in understanding these mechanisms and therapeutic strategies, the complexity and heterogeneity of MDSCs and side effects of antiplatelet agents remain challenging. This requires further investigation in future prospective cohort studies.

Hydrogen Peroxide Inhibits Hepatitis C Virus Replication by Downregulating Hepatitis C Virus Core Levels through E6-Associated Protein-Mediated Proteasomal Degradation

Hepatitis C virus (HCV) is constantly exposed to considerable oxidative stress, characterized by elevated levels of reactive oxygen species, including hydrogen peroxide (H2O2), during acute and chronic infection in the hepatocytes of patients. However, the effect of oxidative stress on HCV replication is largely unknown. In the present study, we demonstrated that H2O2 downregulated HCV Core levels to inhibit HCV replication. For this purpose, H2O2 upregulated p53 levels, resulting in the downregulation of both the protein and enzyme activity levels of DNA methyltransferase 1 (DNMT1), DNMT3a, and DNMT3b, and activated the expression of E6-associated protein (E6AP) through promoter hypomethylation in the presence of HCV Core. E6AP, an E3 ligase, induced the ubiquitin-dependent proteasomal degradation of HCV Core in a p53-dependent manner. The inhibitory effect of H2O2 on HCV replication was almost completely nullified either by treatment with a representative antioxidant, N-acetyl-L-cysteine, or by knockdown of p53 or E6AP using a specific short hairpin RNA, confirming the roles of p53 and E6AP in the inhibition of HCV replication by H2O2. This study provides insights into the mechanisms that regulate HCV replication under conditions of oxidative stress in patients.

Hydrogen Peroxide Inhibits Hepatitis B Virus Replication by Downregulating HBx Levels via Siah-1-Mediated Proteasomal Degradation in Human Hepatoma Cells

The hepatitis B virus (HBV) is constantly exposed to significant oxidative stress characterized by elevated levels of reactive oxygen species (ROS), such as H2O2, during infection in hepatocytes of patients. In this study, we demonstrated that H2O2 inhibits HBV replication in a p53-dependent fashion in human hepatoma cell lines expressing sodium taurocholate cotransporting polypeptide. Interestingly, H2O2 failed to inhibit the replication of an HBV X protein (HBx)-null HBV mutant, but this defect was successfully complemented by ectopic expression of HBx. Additionally, H2O2 upregulated p53 levels, leading to increased expression of seven in absentia homolog 1 (Siah-1) levels. Siah-1, an E3 ligase, induced the ubiquitination-dependent proteasomal degradation of HBx. The inhibitory effect of H2O2 was nearly abolished not only by treatment with a representative antioxidant, N-acetyl-L-cysteine but also by knockdown of either p53 or Siah-1 using specific short hairpin RNA, confirming the role of p53 and Siah-1 in the inhibition of HBV replication by H2O2. The present study provides insights into the mechanism that regulates HBV replication under conditions of oxidative stress in patients.

Relationship between Hepatitis B virus infection and platelet production and dysfunction

Hepatitis B virus (HBV) is a kind of hepatotropic DNA virus. The main target organ is liver, except for liver, HBV has been found in a variety of extrahepatic tissues, such as kidney, thyroid, pancreas, bone marrow, etc. HBV can cause severe complications by invading these tissues. Among them, pancytopenia is one of the common complications, especially thrombocytopenia that causes life-threatening bleeding. However, the mechanism of thrombocytopenia is unclear and the treatment is extremely difficult. It has been confirmed that HBV has a close relationship with platelets. HBV can directly infect bone marrow, inhibit platelet production, and accelerate platelet destruction by activating monocyte-macrophage system and immune system. While platelets act as a double-edged sword to HBV. On one hand, the activated platelets can degranulate and release inflammatory mediators to help clear the viruses. Furthermore, platelets can provide anti-fibrotic molecules to improve liver functions and reduce hepatic fibrosis. On the other hand, platelets can also cause negative effects. The infected platelets collect HBV-specific CD8⁺ T cells and nonspecific inflammatory cells into liver parenchyma, inducing chronic inflammation, liver fibrosis and hepatic carcinoma. This article explores the interaction between HBV infection and platelets, providing a theoretical basis for clinical treatment of thrombocytopenia and severe hemorrhage caused by HBV infection.

Immunopathology of Chronic Hepatitis B Infection: Role of Innate and Adaptive Immune Response in Disease Progression

More than 250 million people are living with chronic hepatitis B despite the availability of highly effective vaccines and oral antivirals. Although innate and adaptive immune cells play crucial roles in controlling hepatitis B virus (HBV) infection, they are also accountable for inflammation and subsequently cause liver pathologies. During the initial phase of HBV infection, innate immunity is triggered leading to antiviral cytokines production, followed by activation and intrahepatic recruitment of the adaptive immune system resulting in successful virus elimination. In chronic HBV infection, significant alterations in both innate and adaptive immunity including expansion of regulatory cells, overexpression of co-inhibitory receptors, presence of abundant inflammatory mediators, and modifications in immune cell derived exosome release and function occurs, which overpower antiviral response leading to persistent viral infection and subsequent immune pathologies associated with disease progression towards fibrosis, cirrhosis, and hepatocellular carcinoma. In this review, we discuss the current knowledge of innate and adaptive immune cells transformations that are associated with immunopathogenesis and disease outcome in CHB patients.

Interplay of Anti-Viral Vaccines with Biologic Agents and Immunomodulators in Individuals with Autoimmune and Autoinflammatory Diseases

Vaccines are an essential part of a preventative healthcare strategy. However, response to vaccines may be less predictable in immunocompromised people. While outcomes for individuals with autoimmune and autoinflammatory diseases have dramatically improved with treatment using immunomodulating and biologic agents, infections have caused significant morbidity in these people today often more than due to their underlying diseases. Immune-based biologic therapies contribute to these infectious complications. This review addresses anti-viral vaccines, their effectiveness and safety in patients treated with approved biologic agents and immune targeted therapy with a focus on vaccines against influenza, human papillomavirus, hepatitis B virus and varicella zoster virus. Preliminary information regarding SARS-CoV-2 anti-viral vaccines is addressed. Additionally, we present recommendations regarding the safe use of vaccines in immunocompromised individuals with the goal to enhance awareness of the safety and efficacy of these anti-viral vaccines in these high-risk populations.

Longitudinal decrease in platelet counts as a surrogate marker of liver fibrosis

BACKGROUND

Liver cirrhosis is a significant source of morbidity and mortality worldwide. The disease is usually indolent and asymptomatic early in its course while many cirrhotic patients are diagnosed late when severe complications occur. A major challenge is to diagnose advanced fibrosis as early as possible, using simple and non-invasive diagnostics tools. Thrombocytopenia represents advanced fibrosis and portal hypertension (HTN) and most non-invasive scores that predict liver fibrosis incorporate platelets as a strong risk factor. However, little is known about the association between longitudinal changes in platelet counts (PTC), when still within the normal range, and the risk of cirrhosis.

AIM

To explore whether platelet counts trajectories over time, can predict advanced liver fibrosis across the different etiologies of liver diseases.

METHODS

A nested case-control study utilizing a large computerized database. Cirrhosis cases (n = 5258) were compared to controls (n = 15744) matched for age and sex at a ratio of 1:3. All participants had multiple laboratory measurements prior to enrollment. We calculated the trends of PTC, liver enzymes, bilirubin, international normalized ratio, albumin and fibrosis scores (fibrosis-4 and aspartate transaminase-to-platelet ratio index) throughout the preceding 20 years prior to cirrhosis diagnosis compared to healthy controls. The association between PTC, cirrhosis complications and fibrosis scores prior to cirrhosis diagnosis was investigated.

RESULTS

The mean age in both groups was 56 (SD 15.8). Cirrhotic patients were more likely to be smokers, diabetic with chronic kidney disease and had a higher prevalence of HTN. The leading cirrhosis etiologies were viral, alcoholic and fatty liver disease. The mean PTC decreased from 240000/μL to 190000/μL up to 15 years prior to cirrhosis diagnosis compared to controls who’s PTC remained stable around the values of 240000/μL. This trend was consistent regardless of sex, cirrhosis etiology and was more pronounced in patients who developed varices and ascites. Compared to controls whose values remained in the normal range, in the cirrhosis group aspartate aminotransferase and alanine aminotransferase, increased from 40 U/L to 75 U/L and FIB-4 increased gradually from 1.3 to 3 prior to cirrhosis diagnosis. In multivariable regression analysis, a decrease of 50 units in PTC was associated with 1.3 times odds of cirrhosis (95%CI 1.25-1.35).

CONCLUSION

In the preceding years before the diagnosis of cirrhosis, there is a progressive decline in PTC, within the normal range, matched to a gradual increase in fibrosis scores.

CRISPR/Cas9 gene editing: A new therapeutic approach in the treatment of infection and autoimmunity

CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein9) may be viewed as an adaptive bacterial immune system. When a virus infects a bacterium, a fragment of the virus genome is inserted into the CRISPR sequence of the bacterial genome as a memory. When the bacterium becomes infected again with the same virus, an RNA molecule that is a transcript of the memory sequence, directs Cas9, an endonuclease, to the complementary region of the virus genome, and Cas9 disables the virus by a double-strand break. In recent years, studies have shown that by designing synthetic RNA molecules and delivering them along with Cas9 into eukaryotic cells, different regions of the cell's genome can be targeted and manipulated. These findings have drawn much attention to this new technology and it has been shown that CRISPR/Cas9 gene editing can be used to treat some human diseases. These include infectious diseases and autoimmune diseases. In this review article, in addition to a brief overview of the biology of the CRISPR/Cas9 system, we collected the most recent findings on the applications of CRISPR/Cas9 technology for better investigation of the pathogenesis and treatment of viral infections (human immunodeficiency virus infection, hepatitis virus infections, and onco-virus infections), non-viral infections (parasitic, fungal, and bacterial infections), and autoimmune diseases.

Aspirin and the risk of hepatocellular carcinoma development in patients with alcoholic cirrhosis

Aspirin therapy has shown protective effects against hepatocellular carcinoma (HCC) in preclinical studies. However, it is unclear whether aspirin therapy lowers the risk of HCC in patients with alcoholic cirrhosis.A retrospective analysis of data from 949 consecutive patients with alcoholic cirrhosis who abstained from alcoholic drinking was performed. The primary and secondary outcomes were development of HCC and gastrointestinal bleeding events, respectively. Risk was compared between patients with aspirin treatment and patients who were not treated (non-aspirin group) using a time-varying Cox proportional hazards model for total population and propensity score-matching analysis.The aspirin group included 224 patients and the non-aspirin group had 725 patients. During the study period of median duration of 3.1 years, 133 patients (13.6%) developed HCC. In time-varying Cox proportional analyses, the aspirin group showed a significantly lower risk of HCC (adjusted hazard ratio [aHR]: 0.13; 95% confidence interval [CI]: 0.08-0.21; P < .001). In propensity score-matched pairs, aspirin therapy significantly reduced the risk of HCC (aHR: 0.14; 95% CI: 0.09-0.22; P < .001). In bleeding risk, treatment with aspirin alone was not significantly associated with a higher bleeding risk (aHR: 0.81; 95% CI: 0.45-1.44; P = .46).Aspirin therapy was associated with the lower risk of HCC in patients with alcoholic cirrhosis.

Platelets in chronic liver disease, from bench to bedside

In the last decade, numerous studies revealed physiologic and pathophysiologic roles of platelets beyond haemostasis, a process to prevent and stop bleeding. These include the activation of the immune system and the promotion of inflammation, infection and cancer. Hence, the emerging view on the role of platelets has shifted - platelets are now seen as alert "sentinels" of the immune compartment, rather than passive bystanders. Herein, we review well-established and newly discovered features of platelets that define their natural role in maintaining blood haemostasis, but also their functional relationship with other cells of the immune system. We focus on recent studies underlining functional involvement of platelets in chronic liver diseases and cancer, as well as the effects of anti-platelet therapy in these contexts. Finally, we illustrate the potential of platelets as possible diagnostic and therapeutic tools in liver disease based on recently developed methodologies.

Platelets and Platelet-Derived Extracellular Vesicles in Liver Physiology and Disease

Beyond their role in hemostasis, platelets are proposed as key mediators of several physiological and pathophysiological processes of the liver, such as liver regeneration, toxic or viral acute liver injury, liver fibrosis, and carcinogenesis. The effects of platelets on the liver involve interactions with sinusoidal endothelial cells and the release of platelet-contained molecules following platelet activation. Platelets are the major source of circulating extracellular vesicles, which are suggested to play key roles in platelet interactions with endothelial cells in several clinical disorders. In the present review, we discuss the implications of platelet-derived extracellular vesicles in physiological and pathophysiological processes of the liver.

T Lymphocytes as Measurable Targets of Protection and Vaccination Against Viral Disorders

Continuous epidemiological surveillance of existing and emerging viruses and their associated disorders is gaining importance in light of their abilities to cause unpredictable outbreaks as a result of increased travel and vaccination choices by steadily growing and aging populations. Close surveillance of outbreaks and herd immunity are also at the forefront, even in industrialized countries, where previously eradicated viruses are now at risk of re-emergence due to instances of strain recombination, contractions in viral vector geographies, and from their potential use as agents of bioterrorism. There is a great need for the rational design of current and future vaccines targeting viruses, with a strong focus on vaccine targeting of adaptive immune effector memory T cells as the gold standard of immunity conferring long-lived protection against a wide variety of pathogens and malignancies. Here, we review viruses that have historically caused large outbreaks and severe lethal disorders, including respiratory, gastric, skin, hepatic, neurologic, and hemorrhagic fevers. To observe trends in vaccinology against these viral disorders, we describe viral genetic, replication, transmission, and tropism, host-immune evasion strategies, and the epidemiology and health risks of their associated syndromes. We focus on immunity generated against both natural infection and vaccination, where a steady shift in conferred vaccination immunogenicity is observed from quantifying activated and proliferating, long-lived effector memory T cell subsets, as the prominent biomarkers of long-term immunity against viruses and their associated disorders causing high morbidity and mortality rates.

Natural History, Clinical Manifestations, and Pathogenesis of Hepatitis A

Hepatitis A virus (HAV) is transmitted by the fecal-oral route and is a major cause of acute viral hepatitis. The clinical manifestations of HAV infection range from asymptomatic infection to acute liver failure (ALF), but do not include progression to chronic hepatitis. Risk factors for severe acute hepatitis A are older age (>40 years) and preexisting liver disease. Some patients may show atypical clinical features such as relapsing hepatitis, prolonged cholestasis, or extrahepatic manifestations. Almost all hepatitis A patients spontaneously recover with supportive care. However, in the case of ALF (<1%), intensive care and urgent decision on liver transplantation are required. Liver injury during hepatitis A is not directly caused by HAV but is known to be caused by immune-mediated mechanisms. In this review, the natural history and clinical manifestations of hepatitis A are described. In addition, mechanisms of immunopathogenesis in hepatitis A are discussed.

Correlations between polymorphisms in the uridine diphosphate-glucuronosyltransferase 1A and C-C motif chemokine receptor 5 genes and infection with the hepatitis B virus in three ethnic groups in China

Objective To determine whether genetic polymorphisms in the uridine diphosphate-glucuronosyltransferase 1A ( UGT1A) and the C-C motif chemokine receptor 5 ( CCR5) genes are associated with hepatitis B virus (HBV) infection in Yi, Yao and Han ethnic groups in the Guizhou Province of China. Methods The study enrolled subjects with and without HBV infection. Whole blood was used for DNA genotyping using standard techniques. The study determined the frequencies of several polymorphic alleles ( UGT1A6 [rs2070959], UGT1A1 [rs8175347], CCR5-59029 [rs1799987] and CCR5Δ32 [rs333]) and then characterized their relationship with HBV infection. Results A total of 404 subjects were enrolled in the study: 138 from the Yao group, 101 from the Yi group and 165 from the Han group. There was a significant difference in the frequency of UGT1A1 rs8175347 polymorphisms among the three groups. The rates of 7TA carriers of UGT1A1 rs8175347 in all three groups were significantly higher than the other genotypes. Individuals with genotype AA of UGT1A6 rs2070959 in the Yi group had a higher risk for HBV infection than in the Yao and Han groups. The frequency of genotype GG in CCR5-59029 in the Yao group was significantly higher than in the Yi group. The genotypes of CCR5Δ32 were not associated with HBV infection. Conclusion These findings provide genetic and epidemiological evidence for an association of UGT1A and CCR5-59029 polymorphisms with HBV infection in Chinese Yi and Yao populations.

Antiplatelet therapy and the risk of hepatocellular carcinoma in chronic hepatitis B patients on antiviral treatment

Antiplatelet therapy has shown protective effects against hepatocellular carcinoma (HCC) in preclinical studies. However, it is unclear whether antiplatelet therapy lowers the risk of HCC in patients with chronic hepatitis B. A retrospective analysis was conducted of data from 1,674 chronic hepatitis B patients, enrolled between January 2002 and May 2015, whose serum hepatitis B virus DNA levels were suppressed by antivirals to <2,000 IU/mL. The primary and secondary outcomes were development of HCC and bleeding events, respectively. Risk was compared between patients with antiplatelet treatment (aspirin, clopidogrel, or both; antiplatelet group) and patients who were not treated (non-antiplatelet group) using a time-varying Cox proportional hazards model for total population and propensity score-matching analysis. The antiplatelet group included 558 patients, and the non-antiplatelet group had 1,116 patients. During the study period, 63 patients (3.8%) developed HCC. In time-varying Cox proportional analyses, the antiplatelet group showed a significantly lower risk of HCC (hazard ratio [HR], 0.44; 95% confidence interval [CI], 0.23-0.85; P = 0.01), regardless of antiplatelet agent. In propensity score-matched pairs, antiplatelet therapy significantly reduced the risk of HCC (HR, 0.34; 95% CI, 0.15-0.77; P = 0.01). However, the overall risk of bleeding was higher in the antiplatelet group (HR, 3.28; 95% CI, 1.98-5.42; P < 0.001), particularly for clopidogrel with or without aspirin. Treatment with aspirin alone was not associated with a higher bleeding risk (HR, 1.11; 95% CI, 0.48-2.54; P = 0.81).

CONCLUSION

Antiplatelet therapy reduces the risk of HCC in chronic hepatitis B patients whose hepatitis B virus is effectively suppressed. However, antiplatelet therapy containing clopidogrel may increase the risk of bleeding. (Hepatology 2017;66:1556-1569).

Enrichment of Ly6Chi monocytes by multiple GM-CSF injections with HBV vaccine contributes to viral clearance in a HBV mouse model

Adjuvants are considered a necessary component for HBV therapeutic vaccines but few are licensed in clinical practice due to concerns about safety or efficiency. In our recent study, we established that a combination protocol of 3-day pretreatments with GM-CSF before a vaccination (3 × GM-CSF+VACCINE) into the same injection site could break immune tolerance and cause over 90% reduction of HBsAg level in the HBsAg transgenic mouse model. Herein, we further investigated the therapeutic potential of the combination in AAV8–1.3HBV-infected mice. After 4 vaccinations, both serum HBeAg and HBsAg were cleared and there was a 95% reduction of HBV-positive hepatocytes, in addition to the presence of large number of infiltrating CD8⁺ T cells in the livers. Mechanistically, the HBV-specific T-cell responses were elicited via a 3 × GM-CSF+VACCINE-induced conversion of CCR2-dependent CD11b⁺ Ly6C^hi monocytes into CD11b⁺CD11c⁺ DCs. Experimental depletion of Ly6C^hi monocytes resulted in a defective HBV-specific immune response thereby abrogating HBV eradication. This vaccination strategy could lead to development of an effective therapeutic protocol against chronic HBV in infected patients.

Oxidative stress, a trigger of hepatitis C and B virus-induced liver carcinogenesis

Virally induced liver cancer usually evolves over long periods of time in the context of a strongly oxidative microenvironment, characterized by chronic liver inflammation and regeneration processes. They ultimately lead to oncogenic mutations in many cellular signaling cascades that drive cell growth and proliferation. Oxidative stress, induced by hepatitis viruses, therefore is one of the factors that drives the neoplastic transformation process in the liver. This review summarizes current knowledge on oxidative stress and oxidative stress responses induced by human hepatitis B and C viruses. It focuses on the molecular mechanisms by which these viruses activate cellular enzymes/systems that generate or scavenge reactive oxygen species (ROS) and control cellular redox homeostasis. The impact of an altered cellular redox homeostasis on the initiation and establishment of chronic viral infection, as well as on the course and outcome of liver fibrosis and hepatocarcinogenesis will be discussed The review neither discusses reactive nitrogen species, although their metabolism is interferes with that of ROS, nor antioxidants as potential therapeutic remedies against viral infections, both subjects meriting an independent review.

Determinants of hepatic effector CD8+ T cell dynamics

Antigen-specific effector CD8⁺ T cells play a critical role in controlling hepatic infections, such as the one caused by hepatitis B virus (HBV). We review here recent results where we coupled advanced dynamic imaging with dedicated mouse models of HBV pathogenesis to show that circulating effector CD8⁺ T cells aimed at viral clearance initially arrest in liver sinusoids by preferentially docking onto platelets that have previously adhered to liver sinusoids. Upon detachment from platelets, effector CD8⁺ T cells crawl within the sinusoids irrespective of bloodstream direction, and probe underlying hepatocytes for the presence of antigen by extending filopodia-like protrusions through the sinusoidal fenestrae. Effector CD8⁺ T cells recognize hepatocellular antigen and perform effector functions (i.e., IFN-γ production and hepatocyte killing) while still in the intravascular space. They later extravasate in the parenchyma. Finally, we provide our perspective on how, in the next few years, intravital microscopy might shed new light on yet unresolved issues with particular regard to identifying the determinants of hepatic effector CD8⁺ T cell trafficking, antigen recognition and effector functions during hepatocellular carcinoma and understanding the mechanisms whereby intrahepatic T cell priming induces functionally defective T cell responses. A better understanding of how adaptive immunity mediates pathogen clearance and tumor elimination may lead to improved vaccination and treatment strategies for immunotherapy of infectious diseases and cancer.

Platelets: No longer bystanders in liver disease

Growing lines of evidence recognize that platelets play a central role in liver homeostasis and pathobiology. Platelets have important roles at every stage during the continuum of liver injury and healing. These cells contribute to the initiation of liver inflammation by promoting leukocyte recruitment through sinusoidal endothelium. They can activate effector cells, thus amplifying liver damage, and by modifying the hepatic cellular and cytokine milieu drive both hepatoprotective and hepatotoxic processes.

CONCLUSION

In this review we summarize how platelets drive such pleiotropic actions and attempt to reconcile the paradox of platelets being both deleterious and beneficial to liver function; with increasingly novel methods of manipulating platelet function at our disposal, we highlight avenues for future therapeutic intervention in liver disease. (Hepatology 2016;64:1774-1784).

Hepatitis B: progress in understanding chronicity, the innate immune response, and cccDNA protection

Hepatitis B virus (HBV) infection is a serious health threat around the world. Despite the availability of an effective hepatitis B vaccine, the number of HBV carriers is estimated to be as high as 240 million worldwide. Global mortality due to HBV-related liver diseases such as chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC) may be as high as 1 million deaths per year. HBV is transmitted via blood and body fluids, and is much more infectious than both human immunodeficiency virus (HIV) and hepatitis C virus. While HBV infection exhibits a variety of clinical presentations, even asymptomatic carriers can develop HCC without liver fibrosis. Current therapeutic options against HBV include pegylated interferon (Peg-IFN) and nucleos(t)ide reverse transcriptase inhibitors (NRTIs), with clinical studies showing a significant association between loss of HBV DNA and a decrease in cancer risk. However, the ultimate goal of HBV therapy is a complete cure of HBV-including the elimination of covalently closed circular DNA (cccDNA)-in order to further decrease the risk of developing HCC. The development of hepatitis B is associated with the host immune response to virus-infected hepatocytes, as HBV is understood to lack direct cytotoxicity. While HBV-specific CD8+ T cells are thus involved in hepatitis development, they also play an important role in eliminating HBV infection. Indeed, the innate immune response during the initial phase of HBV infection is essential to the induction of acquired immunity. However, the innate immune response to HBV infection, including the roles of specific immunocompetent cells and associated molecules, is not well understood. In this review, we focus on the current understanding of the mechanisms underlying hepatitis development by HBV infection. We also address the mechanisms by which HBV protects cccDNA.

Immune responses and immunopathology in acute and chronic viral hepatitis

Hepatitis A virus (HAV), hepatitis B virus (HBV) and hepatitis C virus (HCV) are responsible for most cases of viral hepatitis. Infection by each type of virus results in a different typical natural disease course and clinical outcome that are determined by virological and immunological factors. HCV tends to establish a chronic persistent infection, whereas HAV does not. HBV is effectively controlled in adults, although it persists for a lifetime after neonatal infection. In this Review, we discuss the similarities and differences in immune responses to and immunopathogenesis of HAV, HBV and HCV infections, which may explain the distinct courses and outcomes of each hepatitis virus infection.

Adaptive immunity in the liver

The anatomical architecture of the human liver and the diversity of its immune components endow the liver with its physiological function of immune competence. Adaptive immunity is a major arm of the immune system that is organized in a highly specialized and systematic manner, thus providing long-lasting protection with immunological memory. Adaptive immunity consists of humoral immunity and cellular immunity. Cellular immunity is known to have a crucial role in controlling infection, cancer and autoimmune disorders in the liver. In this article, we will focus on hepatic virus infections, hepatocellular carcinoma and autoimmune disorders as examples to illustrate the current understanding of the contribution of T cells to cellular immunity in these maladies. Cellular immune suppression is primarily responsible for chronic viral infections and cancer. However, an uncontrolled auto-reactive immune response accounts for autoimmunity. Consequently, these immune abnormalities are ascribed to the quantitative and functional changes in adaptive immune cells and their subsets, innate immunocytes, chemokines, cytokines and various surface receptors on immune cells. A greater understanding of the complex orchestration of the hepatic adaptive immune regulators during homeostasis and immune competence are much needed to identify relevant targets for clinical intervention to treat immunological disorders in the liver.

A novel dendritic-cell-targeting DNA vaccine for hepatitis B induces T cell and humoral immune responses and potentiates the antivirus activity in HBV transgenic mice

Strategies for inducing an effective immune response following vaccination have focused on targeting antigens to dendritic cells (DCs) through the DC-specific surface molecule DEC-205. The immunogenicity and efficacy of DNA vaccination can also be enhanced by fusing the encoded antigen to single-chain antibodies directed against DEC-205. Here, we investigated this promising approach for its enhancement of hepatitis B virus (HBV)-specific cellular and humoral immune responses and its antiviral effects in HBV transgenic mice. A plasmid DNA vaccine encoding mouse DEC-205 single-chain fragment variable (mDEC-205-scFv) linked with the hepatitis B surface antigen (HBsAg) was constructed. Vaccination with this fusion DNA vaccine in HBV transgenic mice induced robust antiviral T cell and antibody immunity against HBsAg. The levels of serum-circulating HBsAg and the HBV DNA copy number were downregulated by the induction of a higher HBsAg-specific response. Thus, in this study, we demonstrated the therapeutic efficacy of the novel mDEC-205-scFv-fused DNA vaccine in a mouse model of immune-tolerant, chronic HBV infection.

Mouse Models of Hepatitis B Virus Pathogenesis

The host range of hepatitis B virus (HBV) is limited to humans and chimpanzees. As discussed in the literature, numerous studies in humans and chimpanzees have generated a great deal of information on the mechanisms that cause viral clearance, viral persistence, and disease pathogenesis during acute or chronic HBV infection. Relevant pathogenetic studies have also been performed in those few species representing natural hosts of hepadnaviruses that are related to HBV, such as the woodchuck hepatitis virus and the duck hepatitis virus. Further insight has been gained from multidisciplinary studies in transgenic or humanized chimeric mouse models expressing and/or replicating HBV to varying degrees. We provide here a concise summary of the available HBV mouse models as well as of the contributions of these models to our understanding of HBV pathogenesis.

Immune Response in Hepatitis B Virus Infection

Hepatitis B virus (HBV) can replicate within hepatocytes without causing direct cell damage. The host immune response is, therefore, not only essential to control the spread of virus infection, but it is also responsible for the inflammatory events causing liver pathologies. In this review, we discuss how HBV deals with host immunity and how we can harness it to achieve virus control and suppress liver damage.

Elevated mean platelet volume is associated with poor short-term outcomes in hepatitis B virus-related acute-on-chronic liver failure patients

BACKGROUND AND AIM

It has been shown that mean platelet volume (MPV) can be used as a prognostic biomarker in some chronic diseases. The aim of the present study is to investigate the possible association between MPV and clinical outcome and prognosis in patients with HBV-related acute-on-chronic liver failure (HBV-ACLF) within 4 weeks.

METHODS

This study included 64 patients with HBV-ACLF, 19 chronic hepatitis B (CHB) patients, 27 patients with hepatitis B-related cirrhosis (CR, Child-Pugh A/B), 51 healthy subjects (healthy controls [HC]). The complete blood counts and biochemical examination of blood were obtained after 12h of fasting. In the ACLF group, the relationships between the prognosis and the MPV were analyzed.

RESULTS

At baseline, a statistically significant increase in MPV was shown in patients with ACLF (median 9.5, range 7.1-14.1) compared with HC (8.0, 7.2-11.9, P<0.001), CR (8.4, 5.9-11.1, P<0.001) and CHB (8.3, 7.3-12.0, P<0.001). The MPV value was positively correlated with model of end-stage liver disease (MELD) score and international normalized ratio (INR). The MPV level was significantly increased in nonsurvivors than survivors. High MPV level showed a significantly lower survival rate (P=0.001). Multivariate logistic regression analysis showed that only MPV level was independent factor predicting poor short-term outcomes.

CONCLUSION

MPV values at presentation were higher among nonsurvivors than survivors, and this parameter was well correlated with liver function parameters and may be used as a predictor for 4-week mortality rate in patients with HBV-ACLF.

Hepatic effector CD8(+) T-cell dynamics

CD8(+) T cells play a critical role in hepatitis B virus (HBV) pathogenesis. During acute, self-limited infections, these cells are instrumental to viral clearance; in chronic settings, they sustain repetitive cycles of hepatocellular necrosis that promote hepatocellular carcinoma development. Both CD8(+) T-cell defensive and destructive functions are mediated by antigen-experienced effector cells and depend on the ability of these cells to migrate to the liver, recognize hepatocellular antigens and perform effector functions. Understanding the signals that modulate the spatiotemporal dynamics of CD8(+) T cells in the liver, particularly in the context of antigen recognition, is therefore critical to gaining insight into the pathogenesis of acute and chronic HBV infection. Here, we highlight recent data on how effector CD8(+) T cells traffic within the liver, and we discuss the potential for novel imaging techniques to shed light on this important aspect of HBV pathogenesis.

IL-35 inhibits HBV antigen-specific IFN-γ-producing CTLs in vitro

Interleukin (IL)-35 is an inhibitory cytokine consisting of IL-12A and Epstein-Barr virus-induced gene 3 (Ebi3) and is required by regulatory T-cells (Tregs) for maximal activity. During chronic hepatitis B virus (HBV) infection, Tregs have immunosuppressive effects on HBV-specific T helper (Th) cells, yet little is known about the complex regulation of Tregs and their contribution to the inadequate immune system response to the virus. In the present study, we investigated whether IL-35 is involved in HBV-related cellular immune responses. Cluster of differentiation (CD)4(+) T-cells from peripheral blood were derived from healthy volunteers, resolved HBV individuals and chronic active hepatitis B patients and stimulated with CD3/28-conjugated beads. We analysed mRNA and protein levels of IL-35 and assessed the inhibitory effect of IL-35 on HBV core antigen-specific cytotoxic T lymphocytes (CTLs), dendritic cells (DCs) and effector T-cells (Teffs). Correlation analyses between liver inflammation and HBV DNA load were conducted. Results show that chronic HBV patients harbour significantly higher levels of Ebi3 mRNA and protein in CD4(+) T-cells compared with healthy volunteers and resolved HBV individuals. IL-35 suppressed the proliferation of HBV antigen-specific CTLs and interferon (IFN)-γ production in vitro. Ex vivo, IL-35 decreased the proliferation of CD4(+)CD45RA(+) naïve T-cells, especially in CD4(+)CD25(-)CD45RA(+) naïve Teffs. IL-35 inhibited the expansion of CD11c(+) DCs. Our data indicate that IL-35 is highly expressed in chronic HBV CD4(+) T-cells and plays an important role in the inhibition of the cellular immune response in chronic HBV.

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.

Platelets and infection - an emerging role of platelets in viral infection

Platelets are anucleate blood cells that play a crucial role in the maintenance of hemostasis. While platelet activation and elevated platelet counts (thrombocytosis) are associated with increased risk of thrombotic complications, low platelet counts (thrombocytopenia) and several platelet function disorders increase the risk of bleeding. Over the last years, more and more evidence has emerged that platelets and their activation state can also modulate innate and adaptive immune responses and low platelet counts have been identified as a surrogate marker for poor prognosis in septic patients. Viral infections often coincide with platelet activation. Host inflammatory responses result in the release of platelet activating mediators and a pro-oxidative and pro-coagulant environment, which favors platelet activation. However, viruses can also directly interact with platelets and megakaryocytes and modulate their function. Furthermore, platelets can be activated by viral antigen-antibody complexes and in response to some viruses B-lymphocytes also generate anti-platelet antibodies. All these processes contributing to platelet activation result in increased platelet consumption and removal and often lead to thrombocytopenia, which is frequently observed during viral infection. However, virus-induced platelet activation does not only modulate platelet count but also shape immune responses. Platelets and their released products have been reported to directly and indirectly suppress infection and to support virus persistence in response to certain viruses, making platelets a double-edged sword during viral infections. This review aims to summarize the current knowledge on platelet interaction with different types of viruses, the viral impact on platelet activation, and platelet-mediated modulations of innate and adaptive immune responses.

Reproducible complete remission of advanced hepatocellular carcinoma with sorafenib in combination with clopidogrel

We present a 57-year-old Caucasian man with hepatocellular carcinoma (HCC) twice achieving complete remission with reduced dose sorafenib. His initial diagnosis of HCC rapidly improved with sorafenib and he achieved a complete biochemical and radiographic response within 7 months. Remission lasted only 5 months but we noted that the timing of his relapse was immediately after he incidentally discontinued clopidogrel. It was restarted and within 5 months of restarting clopidogrel he once again achieved complete remission. The course of his remission was followed and temporal association of sorafenib remission with use of clopidogrel was observed.

High seroprevalence of human herpesvirus type 8 in patients with hepatocellular carcinoma

Cirrhosis patients have immunologic insufficiency and a high seroprevalence of human herpesvirus type 8 (HHV-8). Nearly all hepatocellular carcinoma (HCC) patients are cirrhotic and have immunoabnormalities. This study aimed to assess the HHV-8 seroprevalence and hemograms in HCC patients. Blood samples from 95 HCC patients, 95 age-, sex-, and Child-Pugh class-matched cirrhotics, and 95 age- and sex-matched healthy controls were analyzed for anti-HHV-8 antibodies, HHV-8 DNA, and lymphocyte, monocyte, and platelet counts. HCC patients had lower lymphocyte and platelet counts and a higher monocyte count than the healthy controls (each p < 0.0001). HCC patients, and particularly those with a severe Child-Pugh class, had higher platelet counts than the corresponding cirrhosis patients (p = 0.003 and 0.002, respectively). HHV-8 seropositivity and antibody titers in HCC patients were comparable with values in cirrhosis patients and were much higher than in controls (both p < 0.0001). HCC patients, but not cirrhosis patients, had a higher prevalence of high anti-HHV-8 antibody titers (≥ 1:160) than healthy controls (p = 0.003). HCC patients with lymphopenia or thrombocytopenia had lower HHV-8 seropositivity than those without lymphopenia and thrombocytopenia (p = 0.04 and 0.01, respectively). One each of HCC and cirrhosis patients were positive for HHV-8 DNA. HCC patients seemed to suffer from less severe or shorter duration of portal hypertension compared with Child-Pugh class-matched cirrhosis patients. HCC patients had a high HHV-8 seroprevalence, which seemed to be inversely associated with lymphopenia and thrombocytopenia.

Association of genetic variation of sodium taurocholate cotransporting polypeptide with chronic hepatitis B virus infection

BACKGROUND

Sodium taurocholate cotransporting polypeptide (NTCP) plays an important role in the enterohepatic circulation of bile acids and hepatocyte function and was recently proposed to be a functional receptor for hepatitis B virus (HBV).

OBJECTIVE

This study investigated the association of the functional polymorphism c.800C>T (p.S267F) (rs2296651) of the NTCP gene with HBV infection.

METHODS

The study included 244 patients with chronic HBV infection, 76 HBV infection resolvers, and 113 healthy controls. The polymorphism was genotyped using the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

The distribution of the genotype and allele frequency of rs2296651 polymorphism was significantly different among the HBV patients, HBV infection resolvers, and healthy controls (p=0.034 and p=0.039, respectively). The frequency of genotype CT in HBV patients was significantly higher than that in healthy controls (11.9% vs. 4.4%, p=0.026, odds ratios [OR]=2.913, 95% confidence intervals [95% CI]=1.097-7.738). The frequency of allele T in HBV patients was also significantly higher than that in healthy controls (5.9% vs. 2.2%, p=0.029, OR=2.793, 95% CI=1.067-7.312). The frequency of genotype CT and allele T in HBV patients was higher than that in HBV infection resolvers although the difference was not significant. The genotype and allele frequency between infection resolvers and healthy controls and between HBV patients with different clinical diseases had no significant difference.

CONCLUSION

These findings suggest that the rs2296651 polymorphism may predispose the susceptibility to and chronicity of HBV infection.

Mouse models of hepatitis B virus infection comprising host-virus immunologic interactions

Hepatitis B virus (HBV) infection is one of the most prevalent infectious diseases associated with various human liver diseases, including acute, fulminant and chronic hepatitis; liver cirrhosis; and hepatocellular carcinoma. Despite the availability of an HBV vaccine and the development of antiviral therapies, there are still more than 350 million chronically infected people worldwide, approximately 5% of the world population. To understand the virus biology and pathogenesis in HBV-infected patients, several animal models have been developed to mimic hepatic HBV infection and the immune response against HBV, but the narrow host range of HBV infection and lack of a full immune response spectrum in animal models remain significant limitations. Accumulating evidence obtained from studies using a variety of mouse models that recapitulate hepatic HBV infection provides several clues for understanding host-virus immunologic interactions during HBV infection, whereas the determinants of the immune response required for HBV clearance are poorly defined. Therefore, adequate mouse models are urgently needed to elucidate the mechanism of HBV elimination and identify novel targets for antiviral therapies.

Abnormal platelet kinetics are detected before the occurrence of thrombocytopaenia in HBV-related liver disease

BACKGROUND & AIMS

Thrombocytopaenia is a frequent feature in patients with HBV-related liver disease. Its underlying mechanism is not fully understood. Multiple factors might contribute to the development of thrombocytopaenia. In this study, we investigated the reticulated platelets (RP), glycocalicin (GC), serum thrombopoietin (TPO) and platelet glycoprotein (GP) in different stages of the disease.

METHODS

One hundred and fourteen patients with HBV-related liver disease (30 with chronic hepatitis B (CHB), 20 patients in Child A without thrombocytopaenia, 19 patients in Child A with thrombocytopaenia, 45 in Child B/C with thrombocytopaenia) and 25 normal controls (NC) were enrolled. Liver cirrhosis (LC) was classified according to modified Child-Turcotte-Pugh (CTP) score. Serum TPO levels and GC were measured by ELISA. RP and platelet glycoprotein (GP) expression were detected by flow cytometry.

RESULTS

The TPO levels of patients with LC were significantly lower than that of controls, even in patients of Child A without thrombocytopaenia group. Serum TPO level was positively correlated (r = 0.65, p < 0.01) with serum albumin in Child B/C group. Both the RP percentages and the glycocalicin index (GCI) levels were significantly higher in patients groups including CHB and Child A without thrombocytopaenia than that of normal controls. A negative correlation existed in HBV DNA copies and the GPs% in patients with CHB and Child A without thrombocytopaenia.

CONCLUSION

Abnormal platelet production, destruction and platelet-specific glycoproteins levels were detected before the occurrence of thrombocytopaenia in HBV-related liver disease, indicating that multiple mechanisms might play roles in thrombocytopaenia in HBV-infected patients.

An IFN-γ knockout mouse model of HBV persistence

AIM: To develop an interferon-γ (IFN-γ) knockout mouse model of HBV persistence.

METHODS: Nine IFN-γ knock-out (IFN-γ^-/-) mice were injected hydrodynamically with 10 micrograms of pAAV/HBV1.2 DNA via the tail vein. Nine wild-type C57BL/6 mice were used as controls. After injection, blood samples were regularly taken to monitor serum levels of HBsAg, HBeAg and HBV DNA. HBsAg and HBeAg were determined by electrochemiluminescence immunoassay (ECLIA) on an E170 analyzer. Total DNA was extracted from serum samples and used for detection of HBV DNA by real-time PCR.

RESULTS: Serum HBsAg, HBeAg and HBV DNA in IFN-γ^-/- mice were continuously positive until 40 days after the injection of the pAAV/HBV1.2 DNA. The levels and duration of serum HBsAg, HBeAg and HBV DNA in IFN-γ^-/- mice were similar to those in control mice. Serum HBsAg levels in IFN-γ^-/- mice were higher than those in wild-type C57BL/6 mice on day 40 post injection (P = 0.042). Serum HBV DNA levels in IFN-γ^-/- mice were persistently higher than those in wild-type C57BL/6 mice (P = 0.012, on day 25; P = 0.039, on day 40). No significant difference was observed in serum HBeAg levels between IFN-γ^-/- mice and control mice.

CONCLUSION: We have successfully developed an IFN-γ^-/- mouse model of HBV persistence. Our data suggest that IFN-γ could suppress HBV replication during chronic HBV infection.

The L60V variation in hepatitis B virus core protein elicits new epitope-specific cytotoxic T lymphocytes and enhances viral replication

Mutations in the core protein (HBc) of hepatitis B virus (HBV) are associated with aggressive hepatitis and advanced liver diseases in chronic hepatitis B (CHB). In this study, we identified the L60V variation in HBc that generates a new HLA-A2-restricted CD8(+) T cell epitope by screening an overlapping 9-mer peptide pool covering HBc and its variants. The nonameric epitope V60 was determined by structural and immunogenic analysis. The HBc L60V variation is correlated with hepatic necroinflammation and higher viral levels, and it may be associated with a poor prognosis in CHB patients. Immunization with the defined HBV epitope V60 peptide elicited specific cytotoxic T lymphocyte (CTL)-induced liver injury in HLA-A2(+) HBV transgenic mice. In addition, in vitro and in vivo experiments both demonstrated that the HBc L60V variation facilitates viral capsid assembly and increases HBV replication. These data suggest that the HBc L60V variation can impact both HBV replication and HBV-specific T cell responses. Therefore, our work provides further dissection of the impact of the HBc L60V variation, which orchestrates HBV replication, viral persistence, and immunopathogenesis during chronic viral infection.

Cellular immunity in ASFV responses

African swine fever virus (ASFV) infection usually results in an acute haemorrhagic disease with a mortality rate approaching 100% in domestic pigs. However, pigs can survive infection with less-virulent isolates of ASFV and may become chronically infected. Surviving animals are resistant to challenge with homologous or, in some cases, closely related isolates of the virus indicating that pigs can develop protective immunity against ASFV. During asymptomatic, non-virulent ASFV infections natural killer cell activity increases in pigs, suggesting this cell type plays a role in ASFV immunity. Furthermore, depletion of CD8(+) lymphocytes from ASFV immune pigs demolishes protective immunity against related virulent viruses. This suggests that ASFV specific antibody alone is not sufficient for protection against ASFV infection and that there is an important role for the CD8(+) lymphocyte subset in ASFV protective immunity. These results were supported by DNA immunization studies, demonstrating a correlation between the protection afforded against lethal challenge and the detection of a large number of vaccine-induced antigen-specific CD8(+) T-cells. Peripheral blood mononuclear cells (PBMCs) from ASF immune pigs protected from clinical disease show higher proportions of ASFV specific CD4(+)CD8(high+) double positive cytotoxic T cells than PBMCs from ASF immune but clinically diseased pig. The frequency of ASFV specific IFNγ producing T cells induced by immunization correlates to the degree of protection from ASFV challenge, and this may prove to be a useful indicator of any potential cross-protection against heterologous ASFV isolates.

Effector CD8 T cell trafficking within the liver

CD8 T cells play a critical role in several pathological conditions affecting the liver, most notably viral hepatitis. Accordingly, understanding the mechanisms that modulate the intrahepatic recruitment of CD8 T cells is of paramount importance. Some of the rules governing the behavior of these cells in the liver have been characterized at the population level, or have been inferred by studying the intrahepatic behavior of other leukocyte subpopulations. In contrast to most microvascular beds where leukocyte adhesion is restricted to the endothelium of post-capillary venules, it is now becoming clear that in the liver leukocytes, including CD8 T cells, can efficiently interact with the endothelium of hepatic capillaries (i.e. the sinusoids). While physical trapping has been proposed to play an important role in leukocyte adhesion to hepatic sinusoids, there is mounting evidence that T cell recruitment to the liver is highly regulated and depends on recruitment signals that are either constitutive or induced by inflammation. We review here several specific adhesive mechanisms that have been shown to regulate CD8 T cell trafficking within the liver, as well as highlight recent data that establish platelets as key cellular regulators of intrahepatic CD8 T cell accumulation.

Persistent hepatitis B viral replication in a FVB/N mouse model: impact of host and viral factors

The mechanism underlying the chronicity of hepatitis B virus (HBV) infection has long been an interesting question. However, this mechanism remains unclear largely due to the lack of an animal model that can support persistent HBV replication and allow for the investigation of the relevant immune responses. In this study, we used hydrodynamic injection to introduce HBV replicon DNA into the livers of three different mouse strains: BALB/c, C57BL/6, and FVB/N. Interestingly, we found that an HBV clone persistently replicated in the livers of FVB/N mice for up to 50 weeks but was rapidly cleared from the livers of BALB/c and C57BL/6 mice. Flow cytometric analysis and quantitative reverse transcription PCR analysis of the mouse livers indicated that after DNA injection, FVB/N mice had few intrahepatic activated cytotoxic T lymphocytes (CTLs) and produced low levels of alanine aminotransferase, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and the CXCL9 and CXCL10 chemokines. These findings were in sharp contrast with those observed in BALB/c and C57BL/6 mice, reflecting a strong correlation between the degree of liver inflammation and viral clearance. Mutational analysis further demonstrated that a change of Asn-214 to Ser-214 in the HBV surface antigen rendered the persistent HBV clone clearable in FVB/N mice, which was accompanied by increased levels of activated CTL and upregulated expression of IFN-γ, CXCL9, and CXCL10 in the livers. These results indicate that the heterogeneity of the host factors and viral sequences may influence the immune responses against HBV. An inadequate activation of immune or inflammatory responses can lead to persistent HBV replication in vivo.

Dissection of a circulating and intrahepatic CD4(+)Foxp3(+) T-cell subpopulation in chronic hepatitis B virus (HBV) infection: a highly informative strategy for distinguishing chronic HBV infection states

BACKGROUND

The definition of CD4(+)Foxp3(+) regulatory T cells (Tregs) is challenging as it relates to chronic hepatitis B virus (HBV) infection. Recently, the heterogeneity of human CD4(+)Foxp3(+) T cells has been confirmed.

METHODS

Three circulating CD4(+)Foxp3(+) T-cell subpopulations in chronic HBV patients were identified, and their frequencies associated with clinical parameters were analyzed. Antigen specificity of Tregs was further studied.

RESULTS

We found that circulating and intrahepatic CD4(+)CD45RA(-)Foxp3(hi)-activated Tregs (aTregs) were selectively increased in patients with chronic active hepatitis B and acute-on-chronic liver failure (ACLF) but not in asymptomatic carriers. The aTreg frequency was strongly correlated with HBV DNA load but not liver damage. In both peripheral blood mononuclear cells and livers, ACLF patients showed a dramatically elevated frequency of interleukin 17A-secreting CD45RA(-)Foxp3(lo) nonsuppressive T cells (non-Tregs), which were shown to be associated with severe liver damage. Interestingly, an HBV core antigen (HBcAg)-derived peptide could preferentially expand CD4(+)CD25(+)Foxp3(+) T cells and aTregs in HLA-DR9(+) chronic active hepatitis B patients, and these Tregs required ligand-specific reactivation for suppressor function.

CONCLUSIONS

The delineation of a CD4(+)Foxp3(+) T-cell subpopulation is a highly informative strategy for distinguishing different chronic HBV infection states. HBcAg-derived peptides may be responsible for activation of Tregs that, in turn, specifically inhibit anti-HBV immune response but not liver inflammation.

Potential role of soluble B7-H3 in liver immunopathogenesis during chronic HBV infection

Immune-mediated mechanisms have been implicated in liver pathogenesis and subsequent progression in hepatitis B virus (HBV) infection. Costimulatory molecules, the important regulators of immune responses, participate in the regulation of liver pathology in HBV infection. However, the role of B7-H3 (CD276, a new member of B7 family) in this process has not been investigated. In this study, we detected abundant soluble B7-H3 (sB7-H3) in the plasma of patients with chronic HBV infections. The increase of the plasma B7-H3 was associated with the progression of liver cirrhosis and accompanied by decreased expression of B7-H3 on hepatocytes. The identification analysis suggests that the plasma B7-H3 might be derived from the membrane-bound B7-H3 on hepatocytes. A functional study showed that immobilized (4Ig) B7-H3Ig fusion protein could inhibit TCR-induced proliferation and IFN-γ secretion of T cells, which could be partially blocked by soluble B7-H3flag fusion protein. These results suggest that the reduced expression of B7-H3 in the livers might temper the inhibition of T-cell responses mediated by B7-H3 expressed on hepatocytes and thus promote the hepatic inflammation and hepatitis progression in the chronic HBV-infected patients.

Clinical profile, genotype and management updates of hepatitis B virus

Hepatitis B virus (HBV) is a well known agent of acute and chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Around 400 million people worldwide carrier of HBV of which more than 250 million reside in Asia, and 1-2 million people have died from it. It has a partially double-stranded DNA, having 3.2-kb genome size and replicate via reverse transcription of RNA intermediate. In the natural history or during the antiviral therapy of chronic HBV infection, seroconversion from HBeAg to anti-HBeAg is usually accompanied by a decrease in viral replication and remission of liver disease. Based on genomic sequence data HBV is classified into eight genotypes A-H and four major serotypes ayw, ayr, adw and adr on the basis of complete genome and S gene sequence analysis. Genotypes and serotypes are useful tools in understanding the epidemiology of HBV infection. HBV genotypes have distinct geographical distributions. The HBV variants appear during HBeAg seroconversion and they bring mutations in the precore region (PC) that prevent HBeAg synthesis. Another common HBeAg variant is the basal core promoter mutant (BCP) characterized by point mutation in the promoter of both HBeAg mRNA and core protein mRNA. The most frequent core promoter mutation is the double A1762T and G1764A nucleotide exchange, which results in a substantial decrease in HBeAg expression but enhanced viral genome replication. The approved antiviral drugs such as Interferon, lamivudine, adefovir dipivoxil, entecavir and telbivudine for purpose of treating chronic HBV infection is to prevent or stop the progression of liver injury by suppressing viral replication or eliminating infection. Sustained losses of viral markers of active viral replication (HBeAg and HBV DNA) are the standard end point of the therapies.

Unravelling the mechanism and significance of thrombin binding to platelet glycoprotein Ib

The main question concerning the mechanism of a-thrombin binding to platelet membrane glycoprotein (GP)Ib is whether it involves both thrombin exosite I and exosite II. The solution of two independent crystal structures suggests alternative explanations that may actually reflect different modes of binding with distinct pathophysiological significance. With respect to function, it is still unclear whether thrombin binding to GPIb promotes procoagulant and prothrombotic pathways of response to vascular injury or limits such responses by sequestering, at least temporarily, the active enzyme. We review here published information on these topics and touch upon ongoing studies aimed at finding definitive answers to outstanding questions relevant for a better understanding of thrombosis and haemostasis.

Enhanced thrombin formation and fibrinolysis during acute Puumala hantavirus infection

INTRODUCTION

Nephropathia epidemica (NE) is a viral hemorrhagic fever with renal syndrome associated with thrombocytopenia and mild bleeding. We assessed activation of coagulation and fibrinolysis during the acute phase of NE.

MATERIALS AND METHODS

19 hospital-treated patients were involved. Plasma levels of D-dimer, prothrombin fragments 1+2 (F1+2), activated partial thromboplastin time (APTT), prothrombin time (PT%), thrombin time (TT), fibrinogen, antithrombin (AT), protein S free antigen (PS), protein C (PC) and complete blood count (CBC) were measured three times during the acute phase and once at 32-54 days after the onset of fever (recovery phase). Laboratory abnormalities were evaluated by the disseminated intravascular coagulation (DIC) scoring advocated by the International Society of Thrombosis and Haemostasis (ISTH).

RESULTS

APTT was prolonged and D-dimer and F1+2 increased during the acute phase of NE. AT, PC and PS decreased, and TT was shortened, all implying increased thrombin generation. Acutely F1+2 was 3.4-fold and D-dimer even 24-fold higher compared with the recovery phase (median 726 vs 213 pmol/l, and median 4.8 vs 0.2mg/l, respectively, p<0.001 for both). Platelet count correlated with AT, PC, and PS (r=0.73, r=0.81, and r=0.71, respectively, p<0.001 for all) as well as with fibrinogen (r=0.72, p<0.001). Only five patients fulfilled the ISTH diagnosis of DIC.

CONCLUSIONS

During acute NE thrombocytopenia was associated with decreased natural anticoagulants, shortened thrombin time and enhanced fibrinolysis. Augmented thrombin formation and fibrinolysis characterize this hantavirus infection.