Alterations in natural killer cells and natural killer T cells during acute viral hepatitis E

Hepatitis E virus: from innate sensing to adaptive immune responses

Hepatitis E virus (HEV) infections are a major cause of acute viral hepatitis in humans worldwide. In immunocompetent individuals, the majority of HEV infections remain asymptomatic and lead to spontaneous clearance of the virus, and only a minority of individuals with infection (5-16%) experience symptoms of acute viral hepatitis. However, HEV infections can cause up to 30% mortality in pregnant women, become chronic in immunocompromised patients and cause extrahepatic manifestations. A growing body of evidence suggests that the host immune response to infection with different HEV genotypes is a critical determinant of distinct HEV infection outcomes. In this Review, we summarize key components of the innate and adaptive immune responses to HEV, including the underlying immunological mechanisms of HEV associated with acute and chronic liver failure and interactions between T cell and B cell responses. In addition, we discuss the current status of vaccines against HEV and raise outstanding questions regarding the immune responses induced by HEV and treatment of the disease, highlighting areas for future investigation.

From discovery to treatment: tracing the path of hepatitis E virus

The hepatitis E virus (HEV) is a major cause of acute viral hepatitis worldwide. HEV is classified into eight genotypes, labeled HEV-1 through HEV-8. Genotypes 1 and 2 exclusively infect humans, while genotypes 3, 4, and 7 can infect both humans and animals. In contrast, genotypes 5, 6, and 8 are restricted to infecting animals. While most individuals with a strong immune system experience a self-limiting infection, those who are immunosuppressed may develop chronic hepatitis. Pregnant women are particularly vulnerable to severe illness and mortality due to HEV infection. In addition to liver-related complications, HEV can also cause extrahepatic manifestations, including neurological disorders. The immune response is vital in determining the outcome of HEV infection. Deficiencies in T cells, NK cells, and antibody responses are linked to poor prognosis. Interestingly, HEV itself contains microRNAs that regulate its replication and modify the host's antiviral response. Diagnosis of HEV infection involves the detection of HEV RNA and anti-HEV IgM/IgG antibodies. Supportive care is the mainstay of treatment for acute infection, while chronic HEV infection may be cleared with the use of ribavirin and pegylated interferon. Prevention remains the best approach against HEV, focusing on sanitation infrastructure improvements and vaccination, with one vaccine already licensed in China. This comprehensive review provides insights into the spread, genotypes, prevalence, and clinical effects of HEV. Furthermore, it emphasizes the need for further research and attention to HEV, particularly in cases of acute hepatitis, especially among solid-organ transplant recipients.

Pathogenesis and clinical features of severe hepatitis E virus infection

The hepatitis E virus (HEV), a member of the Hepeviridae family, is a small, non-enveloped icosahedral virus divided into eight distinct genotypes (HEV-1 to HEV-8). Only genotypes 1 to 4 are known to cause diseases in humans. Genotypes 1 and 2 commonly spread via fecal-oral transmission, often through the consumption of contaminated water. Genotypes 3 and 4 are known to infect pigs, deer, and wild boars, often transferring to humans through inadequately cooked meat. Acute hepatitis caused by HEV in healthy individuals is mostly asymptomatic or associated with minor symptoms, such as jaundice. However, in immunosuppressed individuals, the disease can progress to chronic hepatitis and even escalate to cirrhosis. For pregnant women, an HEV infection can cause fulminant liver failure, with a potential mortality rate of 25%. Mortality rates also rise amongst cirrhotic patients when they contract an acute HEV infection, which can even trigger acute-on-chronic liver failure if layered onto pre-existing chronic liver disease. As the prevalence of HEV infection continues to rise worldwide, highlighting the particular risks associated with severe HEV infection is of major medical interest. This text offers a brief summary of the characteristics of hepatitis developed by patient groups at an elevated risk of severe HEV infection.

The role of natural killer T cells in liver transplantation

Natural killer T cells (NKTs) are innate-like lymphocytes that are abundant in the liver and participate in liver immunity. NKT cells express both NK cell and T cell markers, modulate innate and adaptive immune responses. Type I and Type II NKT cells are classified according to the TCR usage, while they recognize lipid antigen in a non-classical major histocompatibility (MHC) molecule CD1d-restricted manner. Once activated, NKT cells can quickly produce cytokines and chemokines to negatively or positively regulate the immune responses, depending on the different NKT subsets. In liver transplantation (LTx), the immune reactions in a series of processes determine the recipients' long-term survival, including ischemia-reperfusion injury, alloresponse, and post-transplant infection. This review provides insight into the research on NKT cells subpopulations in LTx immunity during different processes, and discusses the shortcomings of the current research on NKT cells. Additionally, the CD56-expressing T cells are recognized as a NK-like T cell population, they were also discussed during these processes.

Circulating immunophenotypes are potentially prognostic in follicular cell-derived thyroid cancer

Background

Exploring the immune interface of follicular cell-derived thyroid cancer has prognostic and therapeutic potential. The available literature is lacking for comprehensive immunophenotyping in relation to clinical outcomes. In this study, we identify circulating immunophenotypes associated with thyroid cancer prognosis.

Methods

We conducted a pilot observational study of adults with follicular cell-derived thyroid cancer who underwent surgery at our tertiary care referral center and had consented for flow cytometry on peripheral blood collected at the time of thyroidectomy.

Results

Of the 32 included subjects, 20 (62%) had well differentiated, 5 (16%) had poorly differentiated, and 7 (22%) had anaplastic thyroid cancer. The most frequent AJCC stage was 4 (59%) and the ATA risk of recurrence category was high (56%). Patients with AJCC stage 3/4 demonstrated fewer circulating mononuclear cells (CD45+), more monocytes (CD14+), fewer total lymphocytes (CD14-), fewer T cells (CD3+), fewer CD4+ T cells, fewer gamma-delta T cells, fewer natural killer (NK) T-like cells, more myeloid-derived suppressor cells (MDSCs; Lin-CD33+HLADR-), and more effector memory T cells but similar CD8+ T cells compared to stage1/2. Immunophenotype comparisons by ATA risk stratification and course of thyroid cancer were comparable to those observed for stage, except for significant differences in memory T cell subtypes. The median follow-up was 58 months.

Conclusions

Aggressive follicular cell-derived thyroid cancer either at presentation or during follow-up is associated with down-regulation of the T cell populations specifically CD4+ T cells, gamma-delta T cells, and NK T-like cells but up-regulation of MDSCs and altered memory T cells. These immunophenotypes are potential prognostic biomarkers supporting future investigation for developing targeted immunotherapies against advanced thyroid cancer.

Viral Biology and Immune Privilege in the Development of Extrahepatic Manifestations During Hepatitis E Virus Infection

Hepatitis E virus (HEV) exhibits tropism toward hepatocytes and thus affects the liver; however, HEV may also affect other tissues, including the heart, kidneys, intestines, testicles, and central nervous system. To date, the pathophysiological links between HEV infection and extrahepatic manifestations have not yet been established. Considering that HEV infects multiple types of cells, the direct effects of virus replication in peripheral tissues represent a plausible explanation for extrahepatic manifestations. In addition, since the immune response is crucial in the development of the disease, the immune characteristics of affected tissues should be revisited to identify commonalities explaining the effects of the virus. This review summarizes the most recent advances in understanding the virus biology and immune-privileged status of specific tissues as major elements for HEV replication in diverse organs. These discoveries may open avenues to explain the multiple extrahepatic manifestations associated with HEV infection and ultimately to design effective strategies for infection control.

Natural Killer T-like Cells: Immunobiology and Role in Disease

CD56+ T cells are generally recognized as a distinct population of T cells and are categorized as NKT-like cells. Although our understanding of NKT-like cells is far from satisfactory, it has been shown that aging and a number of disease situations have impacted these cells. To construct an overview of what is currently known, we reviewed the literature on human NKT-like cells. NKT-like cells are highly differentiated T cells with "CD1d-independent" antigen recognition and MHC-unrestricted cell killing. The genesis of NKT-like cells is unclear; however, it is proposed that the acquisition of innate characteristics by T cells could represent a remodeling process leading to successful aging. Additionally, it has been shown that NKT-like cells may play a significant role in several pathological conditions, making it necessary to comprehend whether these cells might function as prognostic markers. The quantification and characterization of these cells might serve as a cutting-edge indicator of individual immune health. Additionally, exploring the mechanisms that can control their killing activity in different contexts may therefore result in innovative therapeutic alternatives in a wide range of disease settings.

Immunomodulation of Natural Killer Cell Function by Ribavirin Involves TYK-2 Activation and Subsequent Increased IFN-γ Secretion in the Context of In Vitro Hepatitis E Virus Infection

Hepatitis E virus (HEV) is a major cause of acute hepatitis globally. Chronic and fulminant courses are observed especially in immunocompromised transplant recipients since administration of ribavirin (RBV) does not always lead to a sustained virologic response. By in vitro stimulation of NK cells through hepatoma cell lines inoculated with a full-length HEV and treatment with RBV, we analyzed the viral replication and cell response to further elucidate the mechanism of action of RBV on immune cells, especially NK cells, in the context of HEV infection. Co-culture of HEV-infected hepatoma cells with PBMCs and treatment with RBV both resulted in a decrease in viral replication, which in combination showed an additive effect. An analysis of NK cell functions after stimulation revealed evidence of reduced cytotoxicity by decreased TRAIL and CD107a degranulation. Simultaneously, IFN-ɣ production was significantly increased through the IL-12R pathway. Although there was no direct effect on the IL-12R subunits, downstream events starting with TYK-2 and subsequently pSTAT4 were upregulated. In conclusion, we showed that RBV has an immunomodulatory effect on the IL-12R pathway of NK cells via TYK-2. This subsequently leads to an enhanced IFN-ɣ response and thus, to an additive antiviral effect in the context of an in vitro HEV infection.

Single Cell Transcriptome Analysis of Peripheral Blood Mononuclear Cells in Freshly Isolated versus Stored Blood Samples

BACKGROUND

Peripheral blood mononuclear cells (PBMCs) are widely used as a model in the study of different human diseases. There is often a time delay from blood collection to PBMC isolation during the sampling process, which can result in an experimental bias, particularly when performing single cell RNA-seq (scRNAseq) studies.

METHODS

This study examined the impact of different time periods from blood draw to PBMC isolation on the subsequent transcriptome profiling of different cell types in PBMCs by scRNAseq using the 10X Chromium Single Cell Gene Expression assay.

RESULTS

Examining the five major cell types constituting the PBMC cell population, i.e., CD4+ T cells, CD8+ T cells, NK cells, monocytes, and B cells, both common changes and cell-type-specific changes were observed in the single cell transcriptome profiling over time. In particular, the upregulation of genes regulated by NF-kB in response to TNF was observed in all five cell types. Significant changes in key genes involved in AP-1 signaling were also observed. RBC contamination was a major issue in stored blood, whereas RBC adherence had no direct impact on the cell transcriptome.

CONCLUSIONS

Significant transcriptome changes were observed across different PBMC cell types as a factor of time from blood draw to PBMC isolation and as a consequence of blood storage. This should be kept in mind when interpreting experimental results.

Immunobiology and Host Response to HEV

Hepatitis E virus (HEV) usually causes acute self-limiting hepatitis but sometimes leads to chronic infection in immunocompromised persons. HEV is not directly cytopathic. Immunologically mediated events after HEV infection are believed to play important roles in the pathogenesis and clearance of infection. The anti-HEV antibody responses have been largely clarified since the determination of major antigenic determinant of HEV, which is located in the C-terminal portion of ORF2. This major antigenic determinant also forms the conformational neutralization epitopes. Robust anti-HEV immunoglobulin M (IgM) and IgG responses usually develop 3-4 weeks after infection in experimentally infected nonhuman primates. In humans, potent specific IgM and IgG responses occur in the very early phase of the disease and are critical in eliminating the virus, in concert with the innate and adaptive T-cell immune responses. Testing anti-HEV IgM is valuable in the diagnosis of acute hepatitis E. The long-term persistence and protection of anti-HEV IgG provide the basis for estimating the prevalence of HEV infection and for the development of a hepatitis E vaccine. Although human HEV has four genotypes, all the viral strains are considered to belong to a single serotype. It is becoming increasingly clear that the innate and adaptive T-cell immune responses play critical roles in the clearance of the virus. Potent and multispecific CD4+ and CD8+ T cell responses to the ORF2 protein occur in patients with acute hepatitis E, and weaker HEV-specific CD4+ and CD8+ T cell responses appear to be associated with chronic hepatitis E in immunocompromised individuals.

Detection of Nonenveloped Hepatitis E Virus in Plasma of Infected Blood Donors

BACKGROUND

Transfusion-transmitted hepatitis E virus (HEV) infections have raised many concerns regarding the safety of blood products. To date, enveloped HEV particles have been described in circulating blood, whereas nonenveloped HEV virions have only been found in feces; however, no exhaustive studies have been performed to fully characterize HEV particles in blood.

METHODS

Using isopycnic ultracentrifugation, we determined the types of HEV particles in plasma of HEV-infected blood donors.

RESULTS

Nonenveloped HEV was detected in 8 of 23 plasma samples, whereas enveloped HEV was found in all of them. No association was observed between the presence of nonenveloped HEV and viral load, gender, or age at infection. However, samples with HEV-positive serology and/or increased levels of liver injury markers contained a higher proportion of nonenveloped HEV than samples with HEV-negative serology and normal levels of liver enzymes. These results were further confirmed by analyzing paired donation and follow-up samples of 10 HEV-infected donors who were HEV seronegative at donation but had anti-HEV antibodies and/or increased levels of liver enzymes at follow up.

CONCLUSIONS

The HEV-contaminated blood products may contain nonenveloped HEV, which may pose an additional risk to blood safety by behaving differently to pathogen inactivation treatments or increasing infectivity.

Viral hepatitis in pregnancy

Viral hepatitis is caused by a heterogenous group of viral agents representing a wide range of phylogenetic groups. Many viruses can involve the liver and cause liver injury but only a subset are delineated as 'hepatitis viruses' based upon their primary site of replication and tropism for hepatocytes which make up the bulk of the liver cell population. Since their discovery, beginning with the agent that caused serum hepatitis in the 1960s, the alphabetic designations have been utilized. To date, we have five hepatitis viruses, A through E, though it is postulated that others may exist. This chapter will focus on those viruses. Note that hepatitis D is included as a subset of hepatitis B, as it cannot exist without concurrent hepatitis B infection. Pregnancy has the potential to affect all aspects of these viral agents due to the unique immunologic and physiologic changes that occur during and after the gestational period. In this review, we will discuss the most common viral hepatitis and their effects during pregnancy.

Review of clinical characteristics, immune responses and regulatory mechanisms of hepatitis E-associated liver failure

Hepatitis E virus (HEV) is the most common cause of acute liver failure (LF) and one of the most common factors causing acute injury in acute-on-chronic LF (ACLF). When HEV-related LF occurs, a series of changes take place in both the intrahepatic environment and extrahepatic microenvironment. The changed types and distribution of immune cells (infiltrating macrophages and increased lymphocytes) in liver tissue, as well the increased proinflammatory cytokines and chemokines in the blood, indicate that the occurrence and progression of HEV-related LF are closely related to immune imbalance. The clinical features and immune reaction in the body during HEV-related acute LF (ALF) and ACLF are complicated. This review highlights recent progress in elucidating the clinical manifestations of HEV-associated ALF and ACLF and discusses the corresponding systemic immune changes and possible regulatory mechanisms.

Trained Immunity of IL-12-, IL-15-, and IL-18-Induced CD3+CD56+ NKT-Like Cells

CD₃+CD₅₆+ natural killer T (NKT)-like cells have an immune function of T cells and NK cells, which play an important role in antitumor and antiviral immune responses. This study aims to establish a CD₃+CD₅₆+ NKT-like cell model by simulating the memory NK effect induced by cytokines IL-12, IL-15, and IL-18 (IL-12/15/18) and explore the formation mechanism. Our study found that the IL-12/15/18 preactivated CD₃+CD₅₆+ NKT-like cells exhibited enhanced IFN-γ production in response to restimulation with IL-12/15/18 for 6h on day 7. The intrinsic potential of these trained cells was significantly improved, showing an increase in IFN-γ, TNF-α, and cell proliferation potential. The IFN-γ release, granzyme B level, and proliferation ability significantly increased when stimulated by NK-cell-sensitive K562 tumor cells. Among these cytokines, the combination of IL-12/15/18 was particularly effective. After the preactivation of IL-12/15/18, some cell surface proteins related to function and differentiation, such as CD11b, CD62 L, NKp46, NKG2A, and CD127, showed an evident and consistent change trend. The CDK4/6 inhibitor can effectively weaken this effect, and the expression of cyclin D1, Rb protein phosphorylation, and E2F-1 decreased significantly. Our work revealed that cytokine IL-12/15/18 can induce CD₃+CD₅₆+ NKT-like cells to obtain enhanced training immunity, which was a memory-like phenomenon.

Beyond the Usual Suspects: Hepatitis E Virus and Its Implications in Hepatocellular Carcinoma

Hepatitis E virus infections are the leading cause of viral hepatitis in humans, contributing to an estimated 3.3 million symptomatic cases and almost 44,000 deaths annually. Recently, HEV infections have been found to result in chronic liver infection and cirrhosis in severely immunocompromised patients, suggesting the possibility of HEV-induced hepatocarcinogenesis. While HEV-associated formation of HCC has rarely been reported, the expansion of HEV's clinical spectrum and the increasing evidence of chronic HEV infections raise questions about the connection between HEV and HCC. The present review summarizes current clinical evidence of the relationship between HEV and HCC and discusses mechanisms of virus-induced HCC development with regard to HEV pathogenesis. We further elucidate why the development of HEV-induced hepatocellular carcinoma has so rarely been observed and provide an outlook on possible experimental set-ups to study the relationship between HEV and HCC formation.

PD-1 blockade improves the anti-tumor potency of exhausted CD3+CD56+ NKT-like cells in patients with primary hepatocellular carcinoma

CD3⁺CD56⁺ NKT-like cells play pivotal roles in the anti-tumor immune defense response. However, little is known regarding circulating NKT-like cells in patients with primary hepatocellular carcinoma (HCC). In the present study, we demonstrate that circulating NKT-like cells in HCC patients are functionally impaired and anti-PD-1 blockade improves their anti-tumor potency. Circulating NKT cells were mainly comprised of CD8+ T cells. The frequencies and absolute counts of circulating NKT-like cells were comparable between HCC patents compared to healthy donors. NKT-like cells in HCC patients were impaired in their production of TNF-α and IFN-γ as well as cytotoxicity. The level of activating receptor NKG2D was significantly decreased on NKT-like cells in HCC patients. In contrast, the expression of inhibitory receptors PD-1, Tim-3, and CTLA-4 were markedly increased on NKT-like cells in HCC patients. Meanwhile, the expression of PD-L1 was also upregulated on NKT-like cells in HCC patients. In detail, PD-1⁺ NKT-like cells expressed lower levels of NKG2D, higher levels of Tim-3, and CTLA-4, and less IFN-γ when compared with PD-1⁻ NKT-like cells. Importantly, PD-1 blocked with anti-PD-1 antibody effectively improved the effector function of NKT-like cells from HCC patients or healthy donors. Our findings unveil the functional characterization of NKT-like cells in HCC patients and provide the potential targets to improve their function, which might benefit the optimization of HCC immunotherapy.

Hepatitis E Virus Infection-Immune Responses to an Underestimated Global Threat

Infection with the hepatitis E virus (HEV) is one of the main ubiquitous causes for developing an acute hepatitis. Moreover, chronification plays a predominant role in immunocompromised patients such as transplant recipients with more frequent severe courses. Unfortunately, besides reduction of immunosuppression and off-label use of ribavirin or pegylated interferon alfa, there is currently no specific anti-viral treatment to prevent disease progression. So far, research on involved immune mechanisms induced by HEV is limited. It is very difficult to collect clinical samples especially from the early phase of infection since this is often asymptomatic. Nevertheless, it is certain that the outcome of HEV-infected patients correlates with the strength of the proceeding immune response. Several lymphoid cells have been identified in contributing either to disease progression or achieving sustained virologic response. In particular, a sufficient immune control by both CD4⁺ and CD8⁺ T cells is necessary to prevent chronic viral replication. Especially the mechanisms underlying fulminant courses are poorly understood. However, liver biopsies indicate the involvement of cytotoxic T cells in liver damage. In this review, we aimed to highlight different parts of the lymphoid immune response against HEV and point out questions that remain unanswered regarding this underestimated global threat.

Immunological Manifestations of Hepatitis E-Associated Acute and Chronic Liver Failure and Its Regulatory Mechanisms

Hepatitis E virus (HEV) is a common cause of viral hepatitis in developing countries, most commonly transmitted through the fecal-oral route. The virus is mainly of genotypes (GT) 1 and GT2 genotypes, and patients usually show symptoms of acute hepatitis. Due to the rising trend of HEV serological prevalence in global population, HEV has become an important public health problem in developed countries. Severe hepatitis caused by HEV includes acute and chronic liver failure (ACLF). ACLF frequently occurs in developed countries and is caused by overlapping chronic liver diseases of HEV with genotypes GT3 and GT4. Because the onset of hepatitis E is closely associated with immunity, it is critical to understand the immunological mechanism of hepatitis E associated with acute and chronic liver failure (HEV-ACLF). This review discusses the immunological manifestations and mechanisms of HEV-ACLF, intrahepatic immune microenvironment and treatment, and raises outstanding questions about the immunological mechanism and treatment of the disease.

Higher circulating natural killer cells and lower lactate levels at admission predict spontaneous survival in non-acetaminophen induced acute liver failure

Massive cellular necrosis in acute liver failure (ALF) is dominantly immune mediated and innate immune cells are major pathophysiological determinants in liver damage. In fifty ALF and fifteen healthy, immune cells phenotyping by flow-cytometry, DAMPs using ELISA were analysed and correlated with clinical and biochemical parameters. ALF patients (aged 27 ± 9 yr, 56% males, 78% viral aetiology) showed no difference in neutrophils and classical monocytes, but significantly increased intermediate monocytes (CD14⁺CD16⁺) (p < 0.01), decreased non-classical monocytes (CD14^-CD16⁺) and CD3^-veCD16⁺CD56⁺ NK cells compared to HC. ALF patients who survived, showed higher NK cells (9.28 vs. 5.1%, p < 0.001) among lymphocytes and lower serum lactate levels (6.1 vs. 28, Odds ratio 2.23, CI 1.27-3.94) than non- survivors had higher. Logistic regression model predicted the combination of lactate levels with NK cell percentage at admission for survival. In conclusion, Combination of NK cell frequency among lymphocytes and lactate levels at admission can reliably predict survival of ALF patients.

Mobilization of γδ T Cells and IL-10 Production at the Acute Phase of Hepatitis E Virus Infection in Cytomegalovirus Carriers

Alterations in the γδ T cell compartment have been reported in immunocompromised individuals infected with hepatitis E virus (HEV)-g3. We now report the analysis of blood γδ T cells from acutely HEV-infected individuals in the absence of immunosuppression. In these patients, non-Vδ2 (ND2) γδ T cells outnumbered otherwise predominant Vδ2 cells selectively in human CMV (HCMV)-seropositive patients and were higher than in HCMV^pos controls, mimicking HCMV reactivation, whereas their serum was PCR-negative for HCMV. Stimulation of their lymphocytes with HEV-infected hepatocarcinoma cells led to an HEV-specific response in γδ subsets of HCMV^pos individuals. HEV infection was associated with a lowered expression of TIGIT, LAG-3, and CD160 immune checkpoint markers on ND2 effector memory cells in HCMV^neg but not in HCMV^pos HEV patients. γδ cell lines, predominantly ND2, were generated from patients after coculture with hepatocarcinoma cells permissive to HEV and IL-2/12/18. Upon restimulation with HEV-infected or uninfected cells and selected cytokines, these cell lines produced IFN-γ and IL-10, the latter being induced by IL-12 in IFN-γ-producing cells and upregulated by HEV and IL-18. They were also capable of suppressing the proliferation of CD3/CD28-activated CD4 cells in transwell experiments. Importantly, IL-10 was detected in the plasma of 10 of 10 HCMV^pos HEV patients but rarely in controls or HCMV^neg HEV patients, implying that γδ cells are probably involved in IL-10 production at the acute phase of infection. Our data indicate that HEV mobilizes a pool of ND2 memory cells in HCMV carriers, promoting the development of an immunoregulatory environment.

Surface NKG2C Identifies Differentiated αβT-Cell Clones Expanded in Peripheral Blood

T cells that express CD56 in peripheral blood of healthy humans represent a heterogeneous and poorly studied subset. In this work, we analyzed this subset for NKG2C expression. In both CD56+ and CD56- subsets most of the NKG2C+ T cells had a phenotype of highly differentiated CD8+ TEMRA cells. The CD56+NKG2C+ T cells also expressed a number of NK cell receptors, such as NKG2D, CD16, KIR2DL2/DL3, and maturation marker CD57 more often than the CD56-NKG2C+CD3+ cells. TCR β-chain repertoire of the CD3+CD56+NKG2C+ cell fraction was limited by the prevalence of one or several clonotypes which can be found within the most abundant clonotypes in total or CD8+ T cell fraction TCRβ repertoire. Thus, NKG2C expression in highly differentiated CD56+ T cells was associated with the most expanded αβ T cell clones. NKG2C+ T cells produced almost no IFN-γ in response to stimulation with HCMV pp65-derived peptides. This may be partially due to the high content of CD45RA+CD57+ cells in the fraction. CD3+NKG2C+ cells showed signs of activation, and the frequency of this T-cell subset in HCMV-positive individuals was positively correlated with the frequency of NKG2C+ NK cells that may imply a coordinated in a certain extent development of the NKG2C+ T and NK cell subsets under HCMV infection.

Evidence for Increased Inflammatory Cytokine Profile in Hepatitis E Virus-Infected Obese Patients: Implications for Chronic Liver Disease

We aimed to characterize the contribution of hepatitis E virus (HEV) in perpetuating the cytokine-mediated inflammatory setting related to liver damage in the context of obesity. Herein, serum samples from patients with liver disease were retrospectively analyzed and categorized as normal-weight patients (NW), overweight patients (OW), obese patients (ObP), and high alcohol consumer patients (HAC), and biochemical, anthropometrical, and transient elastography measurements were obtained. The positivity for immunoglobulin M (IgM) and immunoglobulin G (IgG) anti-HEV antibodies in samples was determined by enzyme-linked immunosorbent assay. Available samples from ObP were tested by reverse transcription-nested polymerase chain reaction for the presence of HEV-RNA. Cytokine profile in the serum of ObP was identified using a multiplexed immune assay. Globally, the highest frequency of IgG anti-HEV was found in ObP (57.5%), followed by HAC (20%), OW (15%), and NW (7.5%). A strong association between HEV serology and obesity was found (odds ratio = 4.21, confidence interval = 1.91.9.27) with a cutoff of 29.3 kg/m² (area under curve [AUC] = 0-66; p = 0.003) and, a 23.7% of available samples of ObP provided amplification of HEV genome. Cytokine analysis revealed significantly higher levels of proinflammatory cytokines (interleukin [IL]-12, interferon [IFN]-γ, and IL-1β) in IgG anti-HEV-positive ObP than in IgG anti-HEV-negative ObP. Moreover, a high proportion of patients with positive serology showed advanced liver damage. In conclusion, the high percentage of anti-HEV antibodies and viral RNA detection in the setting of an excess of fat, along with an associated proinflammatory cytokine profile found in IgG anti-HEV-positive ObP with more severe liver disease, support an interplay between HEV and obesity.

Experimental infection of hepatitis E virus induces pancreatic necroptosis in miniature pigs

Infection by hepatitis E virus (HEV) via the oral route causes acute hepatitis. Extra-hepatic manifestations of HEV infection may stem from various causes; however, its distribution in organs such as the liver, as well as the mechanisms underlying HEV-induced cell injury, remain unclear. The objective of this study was to determine the chronological distribution of HEV in various tissues of HEV-challenged miniature pigs and to investigate the mechanisms underlying HEV-induced cell death in the pancreas and liver. Virological and serological analyses were performed on blood and faecal samples. Histopathology of the liver and extra-hepatic tissues was analysed. Cell death pathways and immune cell characterisation in inflammatory lesions were analysed using immunohistochemistry. The liver and pancreas displayed inflammation and cellular injury, and a large amount of HEV was observed in the lesions. The liver was infiltrated by T and natural killer cells. HEV was identified in all organs except the heart, and was associated with immune cells. Although the liver and the pancreas strongly expressed TNF-α and TRAIL, TUNEL assay results were negative. RIP3 and pMLKL were expressed in the pancreas. RIP3, but not pMLKL, was expressed in the liver. Pancreatitis induced in HEV-infected miniature pigs is associated with necroptosis.

Chronic Viral Liver Diseases: Approaching the Liver Using T Cell Receptor-Mediated Gene Technologies

Chronic infection with viral hepatitis is a major risk factor for liver injury and hepatocellular carcinoma (HCC). One major contributing factor to the chronicity is the dysfunction of virus-specific T cell immunity. T cells engineered to express virus-specific T cell receptors (TCRs) may be a therapeutic option to improve host antiviral responses and have demonstrated clinical success against virus-associated tumours. This review aims to give an overview of TCRs identified from viral hepatitis research and discuss how translational lessons learned from cancer immunotherapy can be applied to the field. TCR isolation pipelines, liver homing signals, cell type options, as well as safety considerations will be discussed herein.

Clinical Manifestations, Pathogenesis and Treatment of Hepatitis E Virus Infections

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis throughout the world. Most infections are acute but they can become chronic in immunocompromised patients, such as solid organ transplant patients, patients with hematologic malignancy undergoing chemotherapy and those with a human immunodeficiency virus (HIV) infection. Extra-hepatic manifestations, especially neurological and renal diseases, have also been described. To date, four main genotypes of HEV (HEV1-4) were described. HEV1 and HEV2 only infect humans, while HEV3 and HEV4 can infect both humans and animals, like pigs, wild boar, deer and rabbits. The real epidemiology of HEV has been underestimated because most infections are asymptomatic. This review focuses on the recent advances in our understanding of the pathophysiology of acute HEV infections, including severe hepatitis in patients with pre-existing liver disease and pregnant women. It also examines the mechanisms leading to chronic infection in immunocompromised patients and extra-hepatic manifestations. Acute infections are usually self-limiting and do not require antiviral treatment. Conversely, a chronic HEV infection can be cleared by decreasing the dose of immunosuppressive drugs or by treating with ribavirin for 3 months. Nevertheless, new drugs are needed for those cases in which ribavirin treatment fails.

NKT-Like (CD3+CD56+) Cells in Chronic Myeloid Leukemia Patients Treated With Tyrosine Kinase Inhibitors

Therapy with Tyrosine Kinase Inhibitors (TKI) aiming stable deep molecular response is the gold standard to treat Chronic Myeloid Leukemia (CML). NKT-like cells (CD3+CD56+) combine characteristics of T and NK cells. The physiopathological role of these cells remains unknown although the literature refers their association with inflammation, autoimmune diseases, and cancer. Since the information regarding the role of NKT-like cells in CML is rare, we aimed at the characterization of these cells in CML patients treated with TKIs. Peripheral blood NKT-like cells from 48 CML patients and 40 healthy donors were analyzed by multiparametric flow cytometry. Functional tests consisting of co-culture with leukemic target cells (K562 cell line) were used to measure degranulation and cytokine production. Our results revealed that NKT-like cells are decreased in treated CML patients, although they present increased expression of activation markers (CD69 and HLA-DR), increased degranulation (CD107a) and impaired IFN-γ production. Significantly alterations on the expression of tumor recognition (NCRs and NKp80), and immune regulation receptors (LAG-3, TIM-3, and CD137) by NKT-like cells were observed in CML patients. Second generation TKIs increased cell activation (CD69) and decreased expression of NKp44 and NKp80 by NKT-like cells from CML patients when compared to Imatinib. CML patients that achieved deep molecular response (MR4.5) presented downregulation of NKp44 and LAG-3. Further studies are needed to clarify the role of these cells as biomarkers of therapy response and also to evaluate their value for discrimination of better candidates for sustained treatment-free remission after TKI discontinuation.

Chronic Hepatitis E is associated with cholangitis

BACKGROUND AND AIMS

Sporadic hepatitis E is an emerging indigenous disease in Europe induced by genotype 3 of the virus. While the disease takes an acute self-limited course in immunocompetent individuals, under immunocompromised conditions chronic hepatitis E might develop. The histology of chronic hepatitis E has not been described in detail systematically.

METHODS

Liver biopsies from 19 immunosuppressed patients with chronic hepatitis E were collected: 17 were organ transplant recipients, one had a CD4-deficiency and one had received steroid therapy because of ulcerative colitis. Biopsies were processed with standard stains. Evaluation of histologic activity and fibrosis was performed according to Ishak. Additionally, immunohistochemistry with antibodies directed against open reading frame 2 and 3 of the virus was performed and liver biopsies were tested for hepatitis E virus RNA.

RESULTS

Biochemical data showed an increase in alanine transaminase, aspartate transaminase, gamma-glutamyl transferase and total bilirubin. Histopathology displayed typical features of chronic hepatitis with mild to moderate activity. The number of polymorphonuclear leucocytes was considerably increased and all patients had a florid cholangitis that presented as a destructive form in five of them. Hepatocytes and bile duct epithelia stained positive for hepatitis E virus by immunohistochemistry.

CONCLUSIONS

Chronic hepatitis E in immunocompromised individuals runs a similar course as hepatitis B and C and shows similar histopathology. However, the presence of destructive cholangitis in some cases accompanied by an increased number of polymorphonuclear leucocytes is markedly different. Immunohistochemically the virus is present in bile duct epithelia, seemingly the cause for cholangitis.

Natural History, Clinical Manifestations, and Pathogenesis of Hepatitis E Virus Genotype 1 and 2 Infections

Infection with genotype 1 or 2 hepatitis E virus (HEV) results primarily from human-to-human transmission through the fecal-oral route in low-resource countries. It presents primarily as "acute viral hepatitis" syndrome, usually a self-limiting illness. A few cases progress to acute liver failure, a serious illness with high fatality. Clinical disease is infrequent among children. Infection during pregnancy is associated with a higher risk of symptomatic disease, severe liver injury, and mortality. Severe disease is also encountered in persons with preexisting chronic liver disease. Some cases have associated extrahepatic features, particularly acute pancreatitis and neurological manifestations. Chronic infection appears to be extremely infrequent with these HEV genotypes. The exact pathogenesis of liver injury remains unknown, although the host immune response appears to be important for viral clearance as well as for induction of liver injury. Hormonal and immune factors appear to be responsible for the severe disease during pregnancy.

The Interplay between Host Innate Immunity and Hepatitis E Virus

Hepatitis E virus (HEV) infection represents an emerging global health issue, whereas the clinical outcomes vary dramatically among different populations. The host innate immune system provides a first-line defense against the infection, but dysregulation may partially contribute to severe pathogenesis. A growing body of evidence has indicated the active response of the host innate immunity to HEV infection both in experimental models and in patients. In turn, HEV has developed sophisticated strategies to counteract the host immune system. In this review, we aim to comprehensively decipher the processes of pathogen recognition, interferon, and inflammatory responses, and the involvement of innate immune cells in HEV infection. We further discuss their implications in understanding the pathogenic mechanisms and developing antiviral therapies.

Clinical features and determinants of chronicity in hepatitis E virus infection

Hepatitis E virus (HEV) has traditionally been associated with an acute, self-limiting hepatitis and is not known to have any chronic sequelae. HEV genotypes 1 and 2, which are human pathogens, have been associated with this self-limiting presentation, in both sporadic and epidemic settings. HEV genotype 3, which is zoonotically transmitted, is increasingly being reported as a cause of chronic infection in immunocompromised patients. These include patients with solid organ transplants, patients receiving chemotherapy for haematologic malignancies and patients infected with HIV. Chronic infection is associated with rapidly progressing liver disease and extrahepatic manifestations including neurologic disorders. We review the clinical manifestations of chronic HEV infection and discuss factors determining persistence and chronicity of HEV.

Immunity against hepatitis E virus infection: Implications for therapy and vaccine development

Hepatitis E virus (HEV) is the leading cause of acute viral hepatitis worldwide and an emerging cause of chronic infection in immunocompromised patients. As with viral infections in general, immune responses are critical to determine the outcome of HEV infection. Accumulating studies in cell culture, animal models and patients have improved our understanding of HEV immunopathogenesis and informed the development of new antiviral therapies and effective vaccines. In this review, we discuss the recent progress on innate and adaptive immunity in HEV infection, and the implications for the devolopment of effective vaccines and immune-based therapies.

Immunobiology and Host Response to HEV

Hepatitis E virus (HEV) causes acute self-limiting hepatitis in most cases and chronic infection in rare circumstances. It is believed to be noncytopathic, so immunologically mediated events should play important roles in its pathogenesis and infection outcomes. The anti-HEV antibody response was clarified when the major antigenic determinants on the ORF2 polypeptide were determined, which are located in its C-terminal portion. This subregion also forms the conformational neutralization epitopes. Robust anti-HEV immunoglobulin M (IgM) and IgG responses usually develop 3-4 weeks after infection in experimentally infected nonhuman primates. In humans, potent specific IgM and IgG responses occur in the very early phase of the disease and are critical in eliminating the virus, in concert with the innate and adaptive T-cell immune responses. They are also very valuable in the diagnosis of acute hepatitis E, when patients are tested for both anti-HEV IgM and IgG. The long-term persistence and protection of anti-HEV IgG provide the basis for estimating the prevalence of HEV infection and for the development of a hepatitis E vaccine. Although HEV has four genotypes, all the viral strains are considered to belong to a single serotype. It is becoming increasingly clear that the innate and adaptive T-cell immune responses play critical roles in the clearance of the virus. Potent and multispecific CD4⁺ and CD8⁺ T-cell responses to the ORF2 protein occur in patients with acute hepatitis E, and weaker HEV-specific CD4⁺ and CD8⁺ T-cell responses appear to be associated with chronic hepatitis E in immunocompromised individuals.

Unique clinical courses of transfusion-transmitted hepatitis E in patients with immunosuppression

BACKGROUND

The high prevalence of specific immunoglobulin G for hepatitis E virus (HEV) in Japanese people raises the possibility of a high incidence of HEV-viremic blood donors and therefore frequent transfusion-transmitted HEV (TT-HEV).

STUDY DESIGN AND METHODS

TT-HEV cases established in Japan through hemovigilance and those published in the literature were collected. Infectivity of HEV-contaminated blood components and disease severity in relation to immunosuppression were investigated.

RESULTS

Twenty established TT-HEV cases were recorded over the past 17 years. A lookback study verified that five of 10 patients transfused with known HEV-contaminated blood components acquired HEV infection. The minimal infectious dose of HEV through transfusion was 3.6 × 10⁴ IU. Nine of the 19 TT-HEV cases analyzed had hematologic diseases. Only two cases showed the maximal alanine aminotransferase level of more than 1000 U/L. Two patients with hematologic malignancy and two liver transplant recipients had chronic liver injury of moderate severity.

CONCLUSION

The infectivity of HEV-contaminated components was 50%. Immunosuppression likely causes the moderate illness of TT-HEV, but it may lead to the establishment of chronic sequelae. Transfusion recipients, a population that is variably immunosuppressed, are more vulnerable to chronic liver injury as a result of TT-HEV than the general population is as a result of food-borne infection.

Advances in hepatitis E - I: virology, pathogenesis and diagnosis

INTRODUCTION

Infection with hepatitis E virus (HEV) is the commonest cause of acute hepatitis worldwide. HEV was discovered in 1980s and is known to have small non-enveloped virions with single-stranded RNA genome of positive polarity. In recent years. In recent years, availability of new information has changed our understanding of this virus and the pathogenesis of the related disease.

AREAS COVERED

This article reviews the current knowledge about structure, genomic organization, taxonomy, genetic epidemiology, host specificity and replication of the human HEV and of various closely-related viruses that infect other animals. In addition, the models available for the study of HEV infection, the available information on the pathogenesis of this infection and the techniques available for its diagnosis are also reviewed. Expert commentary: A circulating, enveloped form of the human HEV has been recently recognized. Originally believed to naturally infect only humans and possibly primates, HEV-like viruses are now known to infect several vertebrate animals. Based on this, phylogenetic classification of these viruses has recently been revised. In vitro replicons and infection systems have been developed, which have improved our understanding about the virus and the pathogenesis of infection with it. Recent development of mouse models with chimeric livers that contain human hepatocytes provides another avenue for further advancement of this knowledge.

Hepatitis E Pathogenesis

Although most hepatitis E virus (HEV) infections are asymptomatic, some can be severe, causing fulminant hepatitis and extra-hepatic manifestations, including neurological and kidney injuries. Chronic HEV infections may also occur in immunocompromised patients. This review describes how our understanding of the pathogenesis of HEV infection has progressed in recent years.

Conventional and innate lymphocytes response at the acute phase of HEV infection in transplanted patients

OBJECTIVES

The hepatitis E virus (HEV) causes usually benign and spontaneously resolving acute hepatitis in immunocompetent individuals. In immunocompromised patients with a solid-organ transplant (SOT), chronic infections occur in about 2/3 of cases. We aimed to evaluate the immune cells implicated at the acute phase of HEV infection.

METHODS

We studied the activation and memory markers on CD4, CD8, γδ and NK cells in 32 HEV-free control SOT patients and 23 SOT recipients, including 14 who became chronically infected. Samples from 7 immunocompetent individuals with an acute infection and 8 healthy donor samples were included for comparison.

RESULTS

In acutely-infected SOT patients, NK and Vδ2 cells, but not other γδ cells, had an increased expression of CD69. Based on CD45RA/CD27 markers, solid-organ recipients infected with HEV contained a larger pool of circulating naive subsets among lymphocyte Tγδ cells. However, these alterations of Vδ2 cells were not associated with HEV clearance. Only the adaptive IFN-γ responses to HEV peptides, determined by ELISpot, were associated with a favorable outcome in immunocompromised patients.

CONCLUSIONS

Transplanted patients mobilized their γδ cells at the acute phase of infection. Their precise role in HEV infection will thus deserve further investigations as they could be specifically immunomanipulated.

Impaired monocyte-macrophage functions and defective Toll-like receptor signaling in hepatitis E virus-infected pregnant women with acute liver failure

Acute viral hepatitis resulting due to hepatitis E viral infection (AVH-E) is often serious in pregnancy and could result in acute liver failure (ALF). The role of monocytes and macrophages (mono-macs) in the pathogenesis of AVH-E and development of ALF-E in pregnancy is unclear. We investigated the functions of mono-macs in pregnant (P), AVH-E (n = 44), ALF-E (n = 12), healthy controls (HC; n = 20) and compared with nonpregnant (NP) AVH-E (n = 10), ALF-E (n = 5), and HC (n = 10). We also recruited non-hepatitis E virus-related pregnant (P), ALF-NE (n = 5) and non-pregnant (NP), ALF-NE (n = 12) patients with ALF. Mono-macs, dendritic cell (DC) phenotypes, and Toll-like receptor (TLR) expressions were studied by flow cytometry and reverse-transcriptase polymerase chain reaction. Mono-macs functionality was determined by analyzing their phagocytic activity and reactive oxygen species (ROS) generation by using flow cytometry. Frequency of mono-macs and DCs was increased during HEV infection compared to HC (P < 0.001). Macrophages were increased (P < 0.002) in ALF-E(P) compared to ALF-NE(P). The macrophage phagocytic activity and Escherichia coli-induced ROS production was significantly impaired in ALF-E(P) compared to AVH-E(P) (P < 0.001), ALF-E(NP), and ALF-NE(P) patients (P < 0.02). TLR3 and TLR9 expression and downstream MYD88 signalling molecules IRF3 and IRF7 were significantly down-regulated in ALF-E(P) (P < 0.00) compared to AVH-E(P) and ALF-NE(P).

CONCLUSION

Functionality of mono-macs is impaired in pregnant ALF-E patients compared to AVH-E(P). Reduced TLR3 and TLR7 expression and TLR downstream-signaling molecules in pregnant ALF-E patients suggests inadequate triggers for the innate immune responses contributing to development and severity of ALF-E. Studies using TLR agonists to activate mono-macs may be of use and in vitro studies should be undertaken using patient samples.

Hepatitis E virus infection: Epidemiology and treatment implications

Hepatitis E virus (HEV) infection is now established as an emerging enteric viral hepatitis. Standard treatments in acute and chronic hepatitis E remain to be established. This study undertakes a review of the epidemiology, treatment implication and vaccine prevention from published literature. HEV infection is a worldwide public health problem and can cause acute and chronic hepatitis E. HEV genotypes 1 and 2 are primarily found in developing countries due to waterborne transmission, while the zoonotic potential of genotypes 3 and 4 affects mostly industrialized countries. An awareness of HEV transmission through blood donation, especially in the immunocompromised and solid organ transplant patients, merits an effective anti-viral therapy. There are currently no clear indications for the treatment of acute hepatitis E. Despite concerns for side effects, ribavirin monotherapy or in combination with pegylated interferon alpha for at least 3 mo appeared to show significant efficacy in the treatment of chronic hepatitis E. However, there are no available treatment options for specific patient population groups, such as women who are pregnant. Vaccination and screening of HEV in blood donors are currently a global priority in managing infection. New strategies for the treatment and control of hepatitis E are required for both acute and chronic infections, such as prophylactic use of medications, controlling large outbreaks, and finding acceptable antiviral therapy for pregnant women and other patient groups for whom the current options of treatment are not viable.

Phenotypic and functional analyses of NK and NKT-like populations during the early stages of chikungunya infection

The aim of this study was to characterize NK (CD56⁺CD3⁻) and NKT-like cell (CD56⁺CD3⁺) responses early after chikungunya infection. Expression profiling and functional analysis of T/NK/NKT-like cells were performed on samples from 56 acute and 31 convalescent chikungunya patients and 56 control individuals. The percentages of NK cells were high in both patient groups, whereas NKT-like cell percentages were high only in the convalescent group. The percentages of NKp30⁺CD3⁻CD56⁺, NKp30⁺CD3⁺CD56⁺, CD244⁺CD3⁻CD56⁺, and CD244⁺CD3⁺CD56⁺cells were high, whereas the percentages of NKG2D⁺CD3⁻CD56⁺ and NKG2D⁺CD3⁺CD56⁺cells were low in both patient groups. The percentages of NKp44⁺CD3⁻CD56⁺ cells were high in both patient groups, whereas the percentages of NKp44⁺CD3⁺CD56⁺ cells were higher in the acute group than in convalescent and control groups. The percentages of NKp46⁺CD3⁻CD56⁺ cells were high in both patient groups. Higher percentages of perforin⁺CD3⁻CD56⁺ and perforin⁺CD3⁺CD56⁺ cells were observed in acute and convalescent patients, respectively. Higher cytotoxic activity was observed in acute patients than in controls. IFN-γ expression on NK cells of convalescent patients and on NKT-like cells of both patient groups was indicative of the regulatory role of NK and NKT-like cells. Collectively, these data showed that higher expression of activating receptors on NK/NKT-like cells and perforin⁺ NK cells in acute patients could be responsible for increased cytotoxicity. The observed expression of perforin⁺ NK cells in the acute phase and IFN-γ⁺ NKT-like cells in the subsequent convalescent stage showed that NK/NKT-like cells mount an early and efficient response to chikungunya virus. Further study of the molecular mechanisms that limit viral dissemination/establishment of chronic disease will aid in understanding how NK/NKT-like cells control chikungunya infection.

Increased numbers and functional activity of CD56⁺ T cells in healthy cytomegalovirus positive subjects

Human T cells expressing CD56 are capable of tumour cell lysis following activation with interleukin-2 but their role in viral immunity has been less well studied. Proportions of CD56(+) T cells were found to be highly significantly increased in cytomegalovirus-seropositive (CMV(+) ) compared with seronegative (CMV(-) ) healthy subjects (9.1 ± 1.5% versus 3.7 ± 1.0%; P < 0.0001). Proportions of CD56(+) T cells expressing CD28, CD62L, CD127, CD161 and CCR7 were significantly lower in CMV(+) than CMV(-) subjects but those expressing CD4, CD8, CD45RO, CD57, CD58, CD94 and NKG2C were significantly increased (P < 0.05), some having the phenotype of T effector memory cells. Levels of pro-inflammatory cytokines and CD107a were significantly higher in CD56(+) T cells from CMV(+) than CMV(-) subjects following stimulation with CMV antigens. This also resulted in higher levels of proliferation in CD56(+) T cells from CMV(+) than CMV(-) subjects. Using Class I HLA pentamers, it was found that CD56(+) T cells from CMV(+) subjects contained similar proportions of antigen-specific CD8(+) T cells to CD56(-) T cells in donors of several different HLA types. These differences may reflect the expansion and enhanced functional activity of CMV-specific CD56(+) memory T cells. In view of the link between CD56 expression and T-cell cytotoxic function, this strongly implicates CD56(+) T cells as being an important component of the cytotoxic T-cell response to CMV in healthy carriers.

Hepatitis E rORF2p stimulated and unstimulated peripheral expression profiling in patients with self-limiting hepatitis E infection

To improve the current knowledge on the involvement of peripheral lymphocytes in hepatitis E virus (HEV) associated pathogenesis, we analyzed alterations in (1) immunophenotypic expressions (by flow cytometry) and (2) gene expression patterns (by TaqMan Low Density Array) of activatory, inhibitory, integrin, homing, ectonucleotidase machinery, costimulatory, inflammatory markers, and T regulatory cells (Treg) associated cytokines on HEV rORF2p stimulated and unstimulated PBMCs of 43 acute HEV patients, 30 recovered individuals, and 43 controls. The phenotypic expressions of key molecules CTLA-4, GITR, CD103, CD25, CD69, IL10 and TGF-β₁ in the acute patients and TGF-β₁ in the recovered individuals were significantly elevated on both unstimulated and stimulated PBMCs. Gene expression array data revealed upregulations of CD25, PD1, CD103, CCR4, IL10, and TGF-β₁ on both unstimulated and HEV rORF2p stimulated PBMCs of acute patients. The observed upregulations of inhibitory, integrin, activatory, and Treg-associated cytokine genes on the PBMCs of acute HEV patients complemented by their frequency data suggest them as the major players in the fine-tuning of immune response in self-limiting hepatitis E infection.

Host immune status and response to hepatitis E virus infection

Hepatitis E virus (HEV), identified over 30 years ago, remains a serious threat to life, health, and productivity in developing countries where access to clean water is limited. Recognition that HEV also circulates as a zoonotic and food-borne pathogen in developed countries is more recent. Even without treatment, most cases of HEV-related acute viral hepatitis (with or without jaundice) resolve within 1 to 2 months. However, HEV sometimes leads to acute liver failure, chronic infection, or extrahepatic symptoms. The mechanisms of pathogenesis appear to be substantially immune mediated. This review covers the epidemiology of HEV infection worldwide, the humoral and cellular immune responses to HEV, and the persistence and protection of antibodies produced in response to both natural infection and vaccines. We focus on the contributions of altered immune states (associated with pregnancy, human immunodeficiency virus [HIV], and immunosuppressive agents used in cancer and transplant medicine) to the elevated risks of chronic infection (in immunosuppressed/immunocompromised patients) and acute liver failure and mortality (among pregnant women). We conclude by discussing outstanding questions about the immune response to HEV and interactions with hormones and comorbid conditions. These questions take on heightened importance now that a vaccine is available.

Analysis of antiviral response in human epithelial cells infected with hepatitis E virus

Hepatitis E virus (HEV) is a major cause of enterically transmitted acute hepatitis in developing nations and occurs in sporadic and epidemic forms. The disease may become severe with high mortality (20%) among pregnant women. Due to lack of efficient cell culture system and small animal model, early molecular events of HEV infection are not yet known. In the present study, human lung epithelial cells, A549, were infected with HEV to monitor expression levels of genes/proteins in antiviral pathways. Both live and UV inactivated virus elicited robust induction of inflammatory cytokines/chemokines such as IL-6, IL-8, TNF-α, and RANTES within 12 h of infection. Cells exposed to soluble capsid protein showed no induction suggesting the capsid structure and not the protein being detected as the pathogen pattern by cells. A delayed up-regulation of type I interferon genes only by the live virus at 48 h post HEV infection indicated the need of virus replication. However, absence of secreted interferons till 96 h suggested possible involvement of post-transcriptional regulation of type I IFN expression. HEV infected cells showed activation of both NF-κB and IRF3 transcription factors when seen at protein levels; however, reporter gene assays showed predominant expression via NF-κB promoter as compared to IRF3 promoter. Knockdown experiments done using siRNAs showed involvement of MyD88 and TRIF adaptors in generating antiviral response thus indicating role of TLR2, TLR4 and TLR3 in sensing viral molecules. MAVS knockdown surprisingly enhanced only proinflammatory cytokines and not type I IFNs. This suggested that HEV not only down-regulates RIG-I helicase like receptor mediated IFN induction but also employs MAVS in curtailing host inflammatory response. Our findings uncover an early cellular response in HEV infection and associated molecular mechanisms suggesting the potential role of inflammatory response triggered by HEV infection in host immune response and pathogenesis.

Increased numbers but functional defects of CD56+CD3+ cells in lung cancer

CD56+ T cells were studied in samples of peripheral blood from small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC) patients compared with healthy controls. Relative numbers of CD56+CD3+ cells were increased in NSCLC (P = 0.001) and SCLC (P = 0.002) compared with normal subjects but their ability to respond to activation by up-regulating CD25 or producing IFN-γ were both significantly impaired. Expression of the killer-immunoglobulin-like receptor CD158a was significantly lower on CD56+CD3+ cells in SCLC than controls and also in early stage compared with late stage NSCLC patients. Mean levels of CD158e were higher in NSCLC patients than controls. CD158e levels on CD56+CD3+ cells were increased in the presence of its ligand HLA-Bw4 compared with controls. Although the precise role of CD56+CD3+ cells is not clear, they appear to be functionally impaired in lung cancer, which may have implications for a reduction of direct or indirect anti-tumour responses.

Cytokine profiles, CTL response and T cell frequencies in the peripheral blood of acute patients and individuals recovered from hepatitis E infection

Background

Hepatitis E is a major public health problem in the developing countries. Pathogenesis of hepatitis E virus (HEV) infection is poorly understood.

Methods

This case-control study included 124 Hepatitis E patients (46 acute and 78 recovered), 9 with prior exposure to HEV and 71 anti-HEV negative healthy controls. HEV induced CTL response by Elispot, cytokines/chemokines quantitation by Milliplex assay and peripheral CD4+ & CD8+ T cell frequencies by flow cytometry were assessed.

Results

Among the patient categories, HEV specific IFN-γ responses as recorded by Elispot were comparable. Comparisons of cytokines/chemokines revealed significantly high levels of IL-1α and sIL-2Rα during acute phase. Circulating peripheral CD4/CD8+ T-cell subsets in acute and recovered individuals were comparable compared to controls, while among patient categories CD8+T cell subset was significantly higher in recovered individuals.

Conclusions

Our findings suggest that IL-1α and sIL-2Rα play a role in the pathogenesis of acute Hepatitis E infection. Lack of robust HEV ORF2-specific CTL response in the peripheral blood of HEV infected patients during the acute and recovered phases of the disease may be associated with involvement of innate immune cells/localization of the immune events at the site of infection.

Effector T cells immune reactivity among patients with acute hepatitis E

Hepatitis E virus (HEV) is a leading cause of acute viral hepatitis in several developing countries. Information on cellular immune responses during acute hepatitis E is limited. We therefore studied peripheral blood mononuclear cells (PBMCs) from patients with acute hepatitis E and healthy adult subjects who lacked anti-HEV antibodies for enumeration of various T-cell subsets using flow cytometry and to assess HEV-specific T effector cell responses using interferon-gamma ELISPOT assays. The patients showed increased numbers of CD8(+) cells and CD4(+) CD8(+) cells compared with healthy controls. In addition, the proportion of PBMCs that produced interferon-gamma in response to recombinant HEV open reading frame (ORF) 2 and ORF 3 proteins were found to be higher in patients than in healthy controls. Using pools of 15-mer overlapping peptides corresponding to these recombinant proteins, the immunodominant regions in these proteins for interferon-gamma-producing cells were mapped to regions corresponding to amino acids 181-249 and 301-489 of HEV ORF2 protein. These data provide evidence for the activation of effector T cells during acute hepatitis E. These responses may play a role in viral clearance from the host in patients with HEV infection.

Study of cellular immune response against Hepatitis E virus (HEV)

Hepatitis E virus infection (HEV) is a major cause of acute viral hepatitis in the developing world. The immunopathology of HEV infections has not yet been elucidated. The virus is noncytopathic, and therefore, liver injury may be attributed to immune-mediated damage by cytotoxic T cells and natural killer cells. Therefore, we studied the nature of immune cells involved in HEV-induced liver damage using immunohistochemistry in liver biopsies taken from patients with HEV-induced acute liver failure and demonstrated a significant infiltration of activated CD8(+) T cells containing granzymes. These findings suggest the possible involvement of cytotoxic T cells in disease pathogenesis during HEV infection.