Markus Cornberg

Natural killer cells act as rheostats modulating antiviral T cells

Antiviral T cells are thought to regulate whether hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections result in viral control, asymptomatic persistence or severe disease, although the reasons for these different outcomes remain unclear. Recent genetic evidence, however, has indicated a correlation between certain natural killer (NK)-cell receptors and progression of both HIV and HCV infection, implying that NK cells have a role in these T-cell-associated diseases. Although direct NK-cell-mediated lysis of virus-infected cells may contribute to antiviral defence during some virus infections—especially murine cytomegalovirus (MCMV) infections in mice and perhaps HIV in humans—NK cells have also been suspected of having immunoregulatory functions. For instance, NK cells may indirectly regulate T-cell responses by lysing MCMV-infected antigen-presenting cells. In contrast to MCMV, lymphocytic choriomeningitis virus (LCMV) infection in mice seems to be resistant to any direct antiviral effects of NK cells. Here we examine the roles of NK cells in regulating T-cell-dependent viral persistence and immunopathology in mice infected with LCMV, an established model for HIV and HCV infections in humans. We describe a three-way interaction, whereby activated NK cells cytolytically eliminate activated CD4 T cells that affect CD8 T-cell function and exhaustion. At high virus doses, NK cells prevented fatal pathology while enabling T-cell exhaustion and viral persistence, but at medium doses NK cells paradoxically facilitated lethal T-cell-mediated pathology. Thus, NK cells can act as rheostats, regulating CD4 T-cell-mediated support for the antiviral CD8 T cells that control viral pathogenesis and persistence.

A systematic review of hepatitis C virus epidemiology in Europe, Canada and Israel

Background and Aim: Decisions on public health issues are dependent on reliable epidemiological data. A comprehensive review of the literature was used to gather country‐specific data on risk factors, prevalence, number of diagnosed individuals and genotype distribution of the hepatitis C virus (HCV) infection in selected European countries, Canada and Israel.

Hepatitis B surface antigen (HBsAg) levels in the natural history of hepatitis B virus (HBV)-infection: a European perspective.

BACKGROUND & AIMS The quantifiable level of HBsAg has been suggested as a predictor of treatment response in chronic hepatitis B. However, there is limited information on HBsAg levels considering the dynamic natural course of HBV-infection. This study aimed to determine HBsAg levels in the different phases of HBV-infection in European HBsAg-positive patients. METHODS 226 HBV-monoinfected patients, not undergoing antiviral therapy, were analyzed in a cross-sectional study. Patients were categorized according to the phase of HBV-infection: HBeAg(+) immune tolerance phase (IT, n=30), immune clearance phase (IC, n=48), HBeAg(-) low-replicative phase (LR, n=68), HBeAg(-) hepatitis (ENH, n=68), and acute hepatitis B (n=12). HBsAg was quantified and correlated with HBV-DNA, HBV-genotypes and clinical parameters. In addition, 30 LR-patients were followed longitudinally. RESULTS HBsAg levels were higher in IT-patients and IC-patients compared to LR-patients and ENH-patients (4.96/4.37/3.09/3.87-log(10)IU/ml, p<0.001). HBsAg showed a strong correlation with HBV-DNA during acute hepatitis B (R=0.79, p<0.01). Correlation of HBsAg and HBV-DNA was weak or missing when analyzing different phases of persistent HBV-infection separately. However, associations between HBsAg and HBV-DNA were observed in patients infected with HBV-genotype D but not with HBV-genotype A. LR-patients with HBV-reactivation during follow-up (increase of HBV-DNA >2000IU/ml) showed >3-fold higher baseline HBsAg levels with a NPV of 95% for an HBsAg cut-off of 3500IU/ml. CONCLUSIONS HBsAg levels show significant differences during the natural course of HBV-infection and between HBV-genotypes. These findings may have important implications for understanding the natural history of HBV-infection and for using quantitative HBsAg as a diagnostic tool, i.e. as a marker for predicting HBV-reactivation.

Hepatitis B surface antigen quantification: Why and how to use it in 2011 – A core group report

Quantitative HBsAg had been suggested to be helpful in management of HBV, but assays were cumbersome. The recent availability of commercial quantitative assays has restarted the interest in quantitative serum hepatitis B surface antigen (HBsAg) as a biomarker for prognosis and treatment response in chronic hepatitis B. HBsAg level reflects the transcriptional activity of cccDNA rather than the absolute amount of cccDNA copies. Serum HBsAg level tends to be higher in hepatitis B e antigen (HBeAg)-positive than HBeAg-negative patients. Among patients with a low HBV DNA (<2000IU/ml), HBsAg <1000IU/ml in genotype D HBV infection and HBsAg <100IU/ml in genotype B/C HBV infection is associated with inactive carrier state in HBeAg-negative patients. The HBsAg reduction by nucleos(t)ide analogues (NA) is not as pronounced as by interferon treatment. On peginterferon treatment, sustained responders tend to show greater HBsAg decline than the non-responders. The optimal on-treatment HBsAg cutoff to predict response needs further evaluation in HBeAg-positive patients, but an absence of HBsAg decline together with a <2 log reduction in HBV DNA at week 12 can serve as stopping rule in HBeAg-negative patients with genotype D HBV infection. A rapid serum HBsAg decline during NA therapy may identify patients who will clear HBsAg in the long-term. There are early reports among Asian patients that an HBsAg level of <100IU/ml might predict lower risk of relapse after stopping NA treatment. In clinical practice, serum HBsAg level should be used together with, but not as a substitute for, HBV DNA.

Early monotherapy with pegylated interferon alpha-2b for acute hepatitis C infection: the HEP-NET acute-HCV-II study

Early treatment of acute hepatitis C with interferon alpha‐2b for 24 weeks prevents chronic infection in almost all patients. Because pegylated interferons have replaced conventional interferon in the therapy of chronic hepatitis C, the aim of this study was to analyze the efficacy of an early treatment of acute hepatitis C with peginterferon alfa‐ 2b. Between February 2001 and February 2004, 89 individuals with acute HCV infection were recruited at 53 different centers in Germany. Patients received 1.5 μg/kg peginterferon alfa‐2b for 24 weeks; treatment was initiated after a median of 76 days after infection (range 14‐150). End‐of‐treatment response and sustained virological response were defined as undetectable HCV RNA at the end of therapy and after 24 weeks of follow‐up, respectively. In the total study population, virological response was 82% at the end of treatment and 71% at the end of follow‐up. Of 89 individuals, 65 (73%) were adherent to therapy, receiving 80% of the interferon dosage within 80% of the scheduled treatment duration. End‐of‐treatment and sustained virological response rates in this subpopulation were 94% and 89%, respectively. A maximum alanine aminotransferase level of more than 500 U/L prior to therapy was the only factor associated with successful treatment. In conclusion, in acute HCV infection, early treatment with peginterferon α2b leads to high virological response rates in individuals who are adherent to treatment. The high number of dropouts underlines the importance of thorough patient selection and close monitoring during therapy. Thus, future studies should identify factors predicting spontaneous viral clearance to avoid unnecessary therapy. (HEPATOLOGY 2006;43:250–256.)

Expression of leptin and leptin receptor isoforms in the human stomach

BACKGROUND Leptin is an important regulator of food intake and energy expenditure. Initially it was thought to be expressed exclusively in and secreted by adipocytes. Recently, leptin expression was also noted in other tissues, including rat gastric mucosa. Information on leptin and leptin receptor expression in the human stomach is lacking. AIM To investigate expression of leptin and its corresponding receptors in human gastric epithelial cells. METHODS Fundic and antral gastric mucosal biopsies, primary cultures of human gastric epithelial cells, and the human gastric cancer cell line AGS were screened for expression of leptin and different leptin receptor isoform mRNA by reverse transcriptase-polymerase chain reaction. Immunohistochemistry was performed for localisation of leptin and leptin receptor proteins in gastric mucosa. RESULTS mRNA of leptin and its four receptor isoforms (huOB-R, long receptor isoform; huB219.1–3, short receptor isoforms) was detected in gastric mucosal biopsies, cultured human gastric epithelial cells, and gastric cancer cells. Immunohistochemistry demonstrated that chief as well as parietal cells were reactive to leptin and leptin receptors. CONCLUSIONS Leptin and leptin receptors are expressed in human gastric mucosa. These findings suggest a paracrine and/or autocrine effect of leptin on gastric epithelial cell function.

Historical epidemiology of hepatitis C virus (HCV) in selected countries

Chronic infection with hepatitis C virus (HCV) is a leading indicator for liver disease. New treatment options are becoming available, and there is a need to characterize the epidemiology and disease burden of HCV. Data for prevalence, viremia, genotype, diagnosis and treatment were obtained through literature searches and expert consensus for 16 countries. For some countries, data from centralized registries were used to estimate diagnosis and treatment rates. Data for the number of liver transplants and the proportion attributable to HCV were obtained from centralized databases. Viremic prevalence estimates varied widely between countries, ranging from 0.3% in Austria, England and Germany to 8.5% in Egypt. The largest viremic populations were in Egypt, with 6 358 000 cases in 2008 and Brazil with 2 106 000 cases in 2007. The age distribution of cases differed between countries. In most countries, prevalence rates were higher among males, reflecting higher rates of injection drug use. Diagnosis, treatment and transplant levels also differed considerably between countries. Reliable estimates characterizing HCV‐infected populations are critical for addressing HCV‐related morbidity and mortality. There is a need to quantify the burden of chronic HCV infection at the national level.

Hepatitis E virus infection as a cause of graft hepatitis in liver transplant recipients

Hepatitis E virus (HEV) infection induces self‐limiting liver disease in immunocompetent individuals. Cases of chronic hepatitis E have recently been identified in organ transplant recipients. We questioned if chronic hepatitis E plays a role in graft hepatitis after liver transplantation in a low endemic area. Two hundred twenty‐six liver transplant recipients, 129 nontransplanted patients with chronic liver disease, and 108 healthy controls were tested for HEV antibodies. HEV RNA was investigated in all sera from transplanted patients. HEV antibodies were detected in 1 healthy control (1%), 4 patients with chronic liver disease (3%), and 10 liver transplant recipients (4%). Three liver transplant patients also tested positive for HEV RNA. Two of them developed persistent viremia with HEV genotype 3. The patients were anti‐HEV immunoglobulin G–negative and HEV RNA–negative before transplantation and had an episode of acute hepatitis 5 or 7 months after transplantation, which led to advanced liver fibrosis after 22 months in 1 patient. Seroconversion to anti‐HEV occurred not before 4 months after the first detection of HEV RNA. The possibility of reverse zoonotic transmission was experimentally confirmed by the infection of 5 pigs with a patients serum. The pigs showed histological inflammation in the liver, and HEV RNA was detectable in different organs, including muscle. In conclusion, the prevalence of HEV infection in Central European liver transplant recipients is low; however, chronic hepatitis E may occur and needs to be considered in the differential diagnosis of graft hepatitis. The diagnosis of HEV infection should be based on HEV RNA determination in immunosuppressed patients. We suggest that immunocompromised individuals should avoid eating uncooked meat and contact with possibly HEV‐infected animals. Liver Transpl 16:74–82, 2010.

Memory of mice and men: CD8+ T-cell cross-reactivity and heterologous immunity.

Summary:  The main functions of memory T cells are to provide protection upon re‐exposure to a pathogen and to prevent the re‐emergence of low‐grade persistent pathogens. Memory T cells achieve these functions through their high frequency and elevated activation state, which lead to rapid responses upon antigenic challenge. The significance and characteristics of memory CD8+ T cells in viral infections have been studied extensively. In many of these studies of T‐cell memory, experimental viral immunologists go to great lengths to assure that their animal colonies are free of endogenous pathogens in order to design reproducible experiments. These experimental results are then thought to provide the basis for our understanding of human immune responses to viruses. Although these findings can be enlightening, humans are not immunologically naïve, and they often have memory T‐cell populations that can cross‐react with and respond to a new infectious agent or cross‐react with allo‐antigens and influence the success of tissue transplantation. These cross‐reactive T cells can become activated and modulate the immune response and outcome of subsequent heterologous infections, a phenomenon we have termed heterologous immunity. These large memory populations are also accommodated into a finite immune system, requiring that the host makes room for each new population of memory cell. It appears that memory cells are part of a continually evolving interactive network, where with each new infection there is an alteration in the frequencies, distributions, and activities of memory cells generated in response to previous infections and allo‐antigens.

Interferon-α–Induced TRAIL on Natural Killer Cells Is Associated With Control of Hepatitis C Virus Infection

BACKGROUND & AIMS Pegylated interferon-alpha (PEG-IFNalpha), in combination with ribavirin, controls hepatitis C virus (HCV) infection in approximately 50% of patients by mechanisms that are not completely understood. Beside a direct antiviral effect, different immunomodulatory effects have been discussed. Natural killer (NK) cells might be associated with control of HCV infection. We examined the effects of IFNalpha on human NK cells and its relevance to HCV infection. METHODS We performed gene expression profiling studies of NK cells following stimulation of peripheral blood mononuclear cells with IFNalpha. We evaluated IFNalpha-induced tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression using flow cytometry analyses of NK cells isolated from patients with acute or chronic hepatitis C that had received PEG-IFNalpha therapy. RESULTS TRAIL was among the most up-regulated genes after IFNalpha stimulation of NK cells from healthy controls. After in vitro stimulation with IFNalpha, CD56(dim) NK cells from patients who had responded to PEG-IFNalpha therapy expressed higher levels of TRAIL than cells from patients with chronic hepatitis C. TRAIL expression, ex vivo, was inversely correlated with HCV-RNA levels during the early phase of PEG-IFNalpha therapy. In patients with acute hepatitis C, TRAIL expression on CD56(bright) NK cells increased significantly compared with cells from controls. In in vitro studies, IFNalpha-stimulated NK cells eliminated HCV-replicating hepatoma cells by a TRAIL-mediated mechanism. CONCLUSIONS IFNalpha-induced expression of TRAIL on NK cells is associated with control of HCV infection; these observations might account for the second-phase decline in HCV-RNA levels during PEG-IFNalpha therapy.