Belimumab treatment in autoimmune hepatitis and primary biliary cholangitis - a case series.

Background: The majority of patients with autoimmune hepatitis (AIH) achieve complete remission with established treatment regiments. In patients with intolerance or insufficient response to these drugs, the remaining options are limited and novel treatment approaches necessary. In primary biliary cholangitis (PBC), ursodeoxycholic acid (UDCA) and fibrates have improved prognosis dramatically, but there remains a proportion of patients with refractory disease.In patients with refractory AIH and/or PBC, we used a novel treatment strategy with the anti-B cell activating factor, belimumab. The first three patients had concomitant Sjögren's disease. The connecting element between all three diseases is B cell activation, including elevated levels of the B cell activating factor (BAFF). Furthermore, belimumab has been shown to be beneficial in Sjögren's disease. Aims and methods: To retrospectively investigate treatment response in six patients with AIH or PBC with or without concomitant Sjögren's disease treated with the anti-BAFF therapy belimumab at the University Hospital in Bern, Switzerland. Results: In all three patients with AIH, belimumab improved disease control and helped by-pass or reduce problematic side effects from corticosteroids and calcineurin inhibitors. In PBC patients (n = 3), there was no clear improvement of liver function tests, despite reduction or normalization of IgM. All patients with concomitant Sjögren's disease (n = 3) had an improvement of sicca symptoms and two out of three patients experienced an initially marked reduction in fatigue, which lessened over time. Conclusions: Belimumab may be a promising treatment option for patients with AIH and further investigations are needed. In PBC however, response was not convincing. The effects on sicca symptoms and fatigue were encouraging.

Histological and serological features of acute liver injury after SARS-CoV-2 vaccination.

Background & Aims: Liver injury with autoimmune features after vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is increasingly reported. We investigated a large international cohort of individuals with acute hepatitis arising after SARS-CoV-2 vaccination, focusing on histological and serological features. Methods: Individuals without known pre-existing liver diseases and transaminase levels ≥5x the upper limit of normal within 3 months after any anti-SARS-CoV-2 vaccine, and available liver biopsy were included. Fifty-nine patients were recruited; 35 females; median age 54 years. They were exposed to various combinations of mRNA, vectorial, inactivated and protein-based vaccines. Results: Liver histology showed predominantly lobular hepatitis in 45 (76%), predominantly portal hepatitis in 10 (17%), and other patterns in four (7%) cases; seven had fibrosis Ishak stage ≥3, associated with more severe interface hepatitis. Autoimmune serology, centrally tested in 31 cases, showed anti-antinuclear antibody in 23 (74%), anti-smooth muscle antibody in 19 (61%), anti-gastric parietal cells in eight (26%), anti-liver kidney microsomal antibody in four (13%), and anti-mitochondrial antibody in four (13%) cases. Ninety-one percent were treated with steroids ± azathioprine. Serum transaminase levels improved in all cases and were normal in 24/58 (41%) after 3 months, and in 30/46 (65%) after 6 months. One patient required liver transplantation. Of 15 patients re-exposed to SARS-CoV-2 vaccines, three relapsed. Conclusion: Acute liver injury arising after SARS-CoV-2 vaccination is frequently associated with lobular hepatitis and positive autoantibodies. Whether there is a causal relationship between liver damage and SARS-CoV-2 vaccines remains to be established. A close follow-up is warranted to assess the long-term outcomes of this condition. Impact and implications: Cases of liver injury after vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) have been published. We investigated a large international cohort of individuals with acute hepatitis after SARS-CoV-2 vaccination, focusing on liver biopsy findings and autoantibodies: liver biopsy frequently shows inflammation of the lobule, which is typical of recent injury, and autoantibodies are frequently positive. Whether there is a causal relationship between liver damage and SARS-CoV-2 vaccines remains to be established. Close follow-up is warranted to assess the long-term outcome of this condition.

Mycophenolate mofetil as second line treatment in autoimmune hepatitis - A retrospective single center analysis.

Background: Most patients with autoimmune hepatitis respond to standard treatment with steroids and azathioprine. While the disease is usually fatal if untreated, patients who respond well to therapy have an excellent prognosis. Nevertheless, second-line treatment is necessary in approximately 20% of patients, due to either intolerance or insufficient response to first line treatment.While data for mycophenolate mofetil (MMF) in patients intolerant to azathioprine is encouraging, MMF seems of less benefit in patients with insufficient response to first line treatment, but analyzed data on this issue is limited. Aim: To evaluate the efficacy and safety of MMF as a second-line therapy in patients with AIH. Methods: Retrospective analysis of a monocentric database of AIH patients who received medical care from 2000 to 2022. Clinical, immunological and biochemical parameters were assessed at different time points including last follow-up. Results: Overall, 144 patients with AIH were identified. Fifty out of 144 (35%) AIH patients received MMF. Forty (80%) received MMF due to first line treatment intolerance, while ten (20%) due to insufficient response to first line treatment.Remission with MMF monotherapy was 81.5% in the intolerance group versus 30% in the insufficient response group. Patients switched to MMF because of an insufficient response, more often needed additional prednisolone doses higher than 5 mg/day, a switch to third-line treatment or combination regiments, to achieve disease control. Conclusions: Patients treated with MMF because of intolerance to first line treatment show a good disease control under MMF in the majority of cases. Efficacy is considerably lower in the patients switched to MMF because of an insufficient response to first line treatment.

Accelerated Course of Alveolar Echinococcosis After Treatment With Steroids in a Patient With Autoimmune Encephalitis.

Human alveolar echinococcosis (AE) is a zoonotic infection caused by the fox tapeworm Echinococcus â€‹â€‹â€‹â€‹â€‹â€‹multilocularis. We report the case of a patient who developed an accelerated course of AE with diffuse liver involvement after high-dose steroid treatment for autoimmune encephalitis. Immunosuppressive therapies present us with new challenges regarding the management of AE. With this article, we would like to draw attention to the importance of a screening program for AE before planned immunosuppressive therapy.

Autoimmune hepatitis triggered by SARS-CoV-2 vaccination.

The development of autoimmune diseases has been reported after SARS-CoV-2 infection. Vaccination against SARS-CoV-2 could also trigger auto-immunity, as it has been described with other vaccines. An aberrant immune response induced by molecular mimicry and bystander activation, especially in predisposed individuals, is a potential mechanism. We report the case of a 76-year-old woman with Hashimoto thyroiditis and prior COVID-19 infection who developed severe autoimmune hepatitis (with typical features including strongly positive anti-smooth muscle antibody and markedly elevated immunoglobulins G, as well as typical histological findings) following SARS-CoV-2 vaccination (mRNA-1273 SARS-CoV-2 vaccine, Moderna®). The link between SARS-CoV-2 vaccination and the development of autoimmune diseases needs to be further investigated. Although a causality relationship cannot be proven, caution may be warranted when vaccinating individuals with known autoimmune diseases.

Real-world effectiveness and safety of glecaprevir/pibrentasvir therapy in patients with chronic hepatitis C virus infection in Switzerland.

AIM OF THE STUDY: In the era of pangenotypic treatment regimens against hepatitis C virus (HCV) infection, data from postmarketing observational studies are crucial to better understand the treatment patterns used in specific countries and treatment outcomes under real-life conditions. We report data from Switzerland from an ongoing, multinational postmarketing observational study on the pangenotypic treatment regimen of glecaprevir (GLE; NS3/4A protease inhibitor) and pibrentasvir (PIB; NS5A inhibitor), coformulated as GLE/PIB. METHODS: Adults infected with chronic HCV genotypes 1–6 were eligible to participate in the postmarketing observational study if they started GLE/PIB at the treating physician’s discretion. The primary objective was to evaluate the effectiveness of GLE/PIB based on sustained virological response 12 weeks after completion of treatment (SVR12); secondary outcomes included patient-reported outcomes (Fatigue Severity Scale, Work Productivity and Activity Impairment Questionnaire, Pictorial Representation of Illness and Self Measure tool) and safety data. RESULTS: In Switzerland, 109 patients were enrolled, and 107 patients received ≥1 dose GLE/PIB (94.4% non-cirrhotic; 43.9%/14.0%/29.0%/13.1% GT1/GT2/GT3/GT4; 89.7% treatment-naïve; 91.6% assigned to an 8-week GLE/PIB regimen). Overall, 95 of 98 patients with sufficient follow-up data (96.9%) achieved SVR12 (95% confidence interval [CI] 91.4% to 99.0%), and 91.6% in the safety population (including six non-virological failures). The three treatment failures were due to relapse. All three failures were GT3, without cirrhosis and treatment naïve. Patient-reported outcomes improved as well. GLE/PIB was well tolerated with no serious adverse events and no adverse events leading to discontinuation or interruption of GLE/PIB treatment. CONCLUSION: These real-world effectiveness and safety data of GLE/PIB in patients from Switzerland were consistent with those seen in the multinational registration trials. (Trial registration number: Clinicaltrials.gov: NCT03303599.).

Adult form of Langerhans cell histiocytosis with pulmonary and hepatic involvement mimicking malignancy in a patient with chronic hepatitis C infection.

Langerhans cell histiocytosis (LCH) is a myeloid neoplasm with inflammatory properties. There are few published reports of adult LCH with liver involvement, which is still poorly understood, but shows high morbidity and mortality. We report a case of a 37-year-old woman suffering from hepatitis C showing a LCH affecting the lung as well as the liver. Consistent with histology, we found an early stage of a proliferative/granulomatous phase of hepatobiliary LCH, whereas pulmonary findings showed a nodular stage of adult pulmonary LCH. Although hepatocellular carcinoma is a common malignancy in patients suffering from hepatitis C, it is crucial to keep in mind differential diagnosis for newly appearing liver lesions.

All-Cause Mortality and Causes of Death in the Swiss Hepatitis C Cohort Study (SCCS).

BACKGROUND: With direct-acting antiviral agents (DAAs), mortality rates and causes of death among persons with hepatitis C virus (HCV) infection may change over time. However, the emergence of such trends may be delayed by the slow progression of chronic hepatitis C. To date, detailed analyses of cause-specific mortality among HCV-infected persons over time remain limited. METHODS: We evaluated changes in causes of death among Swiss Hepatitis C Cohort Study (SCCS) participants from 2008 to 2016. We analyzed risk factors for all-cause and cause-specific mortality, accounting for changes in treatment, fibrosis stage, and use of injectable drugs over time. Mortality ascertainment was completed by linking lost-to-follow-up participants to the Swiss Federal Statistical Office death registry. RESULTS: We included 4700 SCCS participants, of whom 478 died between 2008 and 2016. The proportion of unknown causes of death decreased substantially after linkage, from 42% to 10%. Leading causes of death were liver failure (crude death rate 4.4/1000 person-years), liver cancer (3.4/1000 person-years), and nonliver cancer (2.8/1000 person-years), with an increasing proportion of cancer-related deaths over time. Cause-specific analysis showed that persons with sustained virologic response were less at risk for liver-related mortality than those never treated or treated unsuccessfully. CONCLUSIONS: Although the expected decrease in mortality is not yet observable, causes of death among HCV-infected persons have evolved over time. With the wider use of DAAs, liver-related mortality is expected to decline in the future. Continued monitoring of cause-specific mortality will remain important to assess the long-term effect of DAAs and design effective interventions.

Controlled attenuation parameter reflects steatosis in compensated advanced chronic liver disease.

BACKGROUND & AIMS: Controlled attenuation parameter (CAP) for steatosis assessment has not been validated in compensated advanced chronic liver disease compensated advanced chronic liver disease (cACLD). We primarily aimed at assessing the accuracy of CAP for the diagnosis and quantification of steatosis in cACLD. Secondary aim: to assess the validity of non-invasive criteria for cACLD according to liver stiffness measurement (LSM). METHODS: This is a single-centre retrospective study including patients with cACLD defined as LSM ≥10 kPa, CAP measurement and liver biopsy (reference standard for steatosis and fibrosis) observed in 06/2015-06/2017. Steatosis was graded as S0 (<5%), S1 (5%-32%), S2 (33%-66%) and S3 (>66%). The diagnostic performance of CAP for any grade of steatosis and for high-grade steatosis (≥S2) was studied. RESULTS: Among 461 consecutive patients, 111 with LSM-based diagnosis of cACLD were included (63% male, median age 55 years, median body mass index 28.1 Kg/m2 , aetiology: 32% non-alcoholic fatty liver disease/non-alcoholic steatohepatitis, 32% alcohol or viral + metabolic syndrome, 15% viral, 6% autoimmune, 4% alcohol, 11% others). Median LSM and CAP were 16.1 kPa and 277 dB/m respectively. On liver biopsy, steatosis was found in 88/111 patients (79%); 44 patients (43 with metabolic syndrome) had high-grade steatosis. CAP was accurate in identifying any grade of steatosis (area under the receiving operating characteristic curves 0.847; 95% CI 0.767-0.926, P < .0001), and ≥S2 steatosis (0.860; 95% CI 0.788-0.932, P < .0001). CAP performed similarly in patients with CAP- interquartile range (IQR) ≥ or <40 dB/m. CONCLUSIONS: Steatosis is frequent in patients with cACLD and metabolic syndrome. CAP diagnostic accuracy for any steatosis and high-grade steatosis is good in this population. A CAP-IQR ≥40 dB/m does not impair CAP diagnostic accuracy in cACLD.

4-O'-methylhonokiol protects from alcohol/carbon tetrachloride-induced liver injury in mice.

Alcoholic liver disease (ALD) is a leading cause of liver cirrhosis, liver cancer, and related mortality. The endocannabinoid system contributes to the development of chronic liver diseases, where cannabinoid receptor 2 (CB2) has been shown to have a protecting role. Thus, here, we investigated how CB2 agonism by 4'-O-methylhonokiol (MHK), a biphenyl from Magnolia grandiflora, affects chronic alcohol-induced liver fibrosis and damage in mice. A combination of alcohol (10% vol/vol) and CCl4 (1 ml/kg) was applied to C57BL/6 mice for 5 weeks. MHK (5 mg/kg) was administered daily, and liver damage assessed by serum AST and ALT levels, histology, gene, and protein expression. Endocannabinoids (ECs) and related lipid derivatives were measured by liquid chromatography and mass spectrometry (LC-MS) in liver tissues. In vitro, MHK was studied in TGFß1-activated hepatic stellate cells (HSC). MHK treatment alleviated hepatic fibrosis, paralleled by induced expression of matrix metalloproteinases (MMP)-2, -3, -9, and -13, and downregulation of CB1 mRNA. Necrotic lesions and hepatic inflammation were moderately improved, while IL-10 mRNA increased and IFNγ, Mcl-1, JNK1, and RIPK1 normalized by MHK. Hepatic anandamide (AEA) and related N-acetylethanolamines (NAEs) were elevated in MHK group, whereas fatty acid synthase and diacylglycerol O-acyltransferase 2 expression reduced. In vitro, MHK prevented HSC activation and induced apoptosis via induction of bak1 and bcl-2. To conclude, MHK revealed hepatoprotective effects during alcohol-induced liver damage through the induction of MMPs, AEA, and NAEs and prevention of HSC activation, indicating MHK as a potent therapeutic for liver fibrosis and ALD. KEY MESSAGES: Methylhonokiol improves liver damage and survival. Methylhonokiol reduces hepatic fibrosis and necroinflammation. Methylhonokiol prevents myofibroblast activation and induces apoptosis. Methylhonokiol upregulates endocannabinoids and related N-acylethanolamines. Methylhonokiol contributes to lipid hydrolysis via PPARα/γ.

Reduced IFNλ4 activity is associated with improved HCV clearance and reduced expression of interferon-stimulated genes.

Hepatitis C virus (HCV) infections are the major cause of chronic liver disease, cirrhosis and hepatocellular carcinoma worldwide. Both spontaneous and treatment-induced clearance of HCV depend on genetic variation within the interferon-lambda locus, but until now no clear causal relationship has been established. Here we demonstrate that an amino-acid substitution in the IFNλ4 protein changing a proline at position 70 to a serine (P70S) substantially alters its antiviral activity. Patients harbouring the impaired IFNλ4-S70 variant display lower interferon-stimulated gene (ISG) expression levels, better treatment response rates and better spontaneous clearance rates, compared with patients coding for the fully active IFNλ4-P70 variant. Altogether, these data provide evidence supporting a role for the active IFNλ4 protein as the driver of high hepatic ISG expression as well as the cause of poor HCV clearance.

A common polymorphism in the NCAN gene is associated with hepatocellular carcinoma in alcoholic liver disease.

BACKGROUND & AIMS: The genetic background of alcoholic liver diseases and their complications are increasingly recognized. A common polymorphism in the neurocan (NCAN) gene, which is known to be expressed in neuronal tissue, has been identified as a risk factor for non-alcoholic fatty liver disease (NAFLD). We investigated if this polymorphism may also be related to alcoholic liver disease (ALD) and hepatocellular carcinoma (HCC). METHODS: We analysed the distribution of the NCAN rs2228603 genotypes in 356 patients with alcoholic liver cirrhosis, 126 patients with alcoholic HCC, 382 persons with alcohol abuse without liver damage, 362 healthy controls and in 171 patients with hepatitis C virus (HCV) associated HCC. Furthermore, a validation cohort of 229 patients with alcoholic cirrhosis (83 with HCC) was analysed. The genotypes were determined by LightSNiP assays. The expression of NCAN was studied by RT-PCR and immunofluorescence microscopy. RESULTS: The frequency of the NCAN rs2228603 T allele was significantly increased in patients with HCC due to ALD (15.1%) compared to alcoholic cirrhosis without HCC (9.3%), alcoholic controls (7.2%), healthy controls (7.9%), and HCV associated HCC (9.1%). This finding was confirmed in the validation cohort (15.7% vs. 6.8%, OR=2.53; 95%CI: 1.36-4.68; p=0.0025) and by multivariate analysis (OR=1.840; 95%CI: 1.22-2.78; p=0.004 for carriage of the rs2228603 T allele). In addition, we identified and localised NCAN expression in human liver. CONCLUSIONS: NCAN is not only expressed in neuronal tissue, but also in the liver. Its rs2228603 polymorphism is a risk factor for HCC in ALD, but not in HCV infection.

IL28B expression depends on a novel TT/-G polymorphism which improves HCV clearance prediction.

Approximately 3% of the world population is chronically infected with the hepatitis C virus (HCV), with potential development of cirrhosis and hepatocellular carcinoma. Despite the availability of new antiviral agents, treatment remains suboptimal. Genome-wide association studies (GWAS) identified rs12979860, a polymorphism nearby IL28B, as an important predictor of HCV clearance. We report the identification of a novel TT/-G polymorphism in the CpG region upstream of IL28B, which is a better predictor of HCV clearance than rs12979860. By using peripheral blood mononuclear cells (PBMCs) from individuals carrying different allelic combinations of the TT/-G and rs12979860 polymorphisms, we show that induction of IL28B and IFN-γ-inducible protein 10 (IP-10) mRNA relies on TT/-G, but not rs12979860, making TT/-G the only functional variant identified so far. This novel step in understanding the genetic regulation of IL28B may have important implications for clinical practice, as the use of TT/G genotyping instead of rs12979860 would improve patient management.

Acute Hepatitis Induced by Lyprinol, the Lipid Extract of the Green-Lipped Mussel (Perna canaliculus), in a Patient with Polyarthrosis.

Lyprinol, the lipid extract of the green-lipped mussel (Perna canaliculus), is a readily and freely available agent with a putative anti-inflammatory impact. It has already found application as a complementary and supplementary treatment of osteoarthritis, rheumatoid arthritis, asthma, and cancer. So far no major side effects for Lyprinol have been reported, yet. Here, we present the case of a 76-year-old woman with acutely exacerbating abdominal pain and highly elevated liver transaminases while taking Lyprinol as a complementary treatment of polyarthrosis.

Lack of ex vivo peripheral and intrahepatic α-fetoprotein-specific CD4+ responses in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common malignancies with a poor prognosis and limited therapeutic options that is often characterized by the expression of the tumor-associated antigen α-fetoprotein (AFP). CD4+ helper T cells are important in generating potent anticancer immunity as they prime and expand CD8+ T-cell memory and may also have direct antitumor activity. However, very little information is currently available about the relative frequency, immunodominance and peripheral versus intratumoral distribution of AFP-specific CD4+ T-cell responses in patients with HCC. We, therefore, analyzed AFP-specific CD4+ responses in blood and tumor tissue of patients with HCC by using overlapping peptides spanning the entire AFP protein and novel sensitive approaches such as antigen-specific upregulation of CD154. We found that AFP-specific CD4+ T-cell responses were not detectable in the peripheral blood ex vivo. However, after in vitro stimulation, AFP-specific CD4+ T-cell responses were detectable in a large fraction of patients targeting different previously unreported epitopes with no clear immunodominance. These results indicate that AFP-specific CD4+ T-cell responses are not completely deleted but only present at very low frequencies. Importantly, AFP-specific CD4+ T-cell responses were also rarely detectable in tumor tissue, suggesting that the relative absence of these cells in the circulation ex vivo is not due to a rapid accumulation to the tumor side. Taken together, these results suggest that the lack of sufficient CD4+ T-cell help, especially within the tumor tissue, may be one central mechanism responsible for the failure of AFP-specific immune responses to control HCC progression.

Virus-specific CD4+ T cell responses in chronic HCV infection in blood and liver identified by antigen-specific upregulation of CD154.

BACKGROUND & AIMS: Virus-specific CD4+ T cells play a major role in hepatitis C virus (HCV) infection. Viral clearance is associated with vigorous and multispecific CD4+ T cell responses, while chronic infection has been shown to be associated with weak or absent T cell responses. Most of these studies, however, have used functional assays to analyse virus-specific CD4+ T cell responses. Therefore, the important question, of whether virus-specific CD4+ T cells are completely absent or primarily impaired in specific effector functions during chronic infection, has yet to be analysed in detail. METHODS: To address this issue, a novel assay, where CD4+ T cell frequencies can be determined by de novo CD154 (CD40 ligand) expression in response to HCV antigens, was used in a cohort of chronically infected HCV patients and patients who spontaneously resolved HCV infection. These responses were compared to functional assays, such as the IFN-gamma ELISpot and flow cytometry-based proliferative assays. RESULTS: Our results reveal that using the CD154 assay, virus-specific CD4+ T cells are readily detectable during chronic HCV infection albeit at a lower frequency when compared to patients who spontaneously resolved the infection. Importantly, no CD4+ T cell responses were detectable from these patients when using functional assays. Finally, these cell populations were enriched in the intrahepatic compartment. CONCLUSIONS: Our findings suggest that HCV-specific CD4+ T cell responses are readily detectable in chronic HCV infection and enriched in the infected liver.

CD4+ T cell responses in hepatitis C virus infection.

Hepatitis C virus (HCV) infection is a major cause of liver damage, with virus-induced end-stage disease such as liver cirrhosis and hepatocellular carcinoma resulting in a high rate of morbidity and mortality worldwide. Evidence that CD4+ T cell responses to HCV play an important role in the outcome of acute infection has been shown in several studies. However, the mechanisms behind viral persistence and the failure of CD4+ T cell responses to contain virus are poorly understood. During chronic HCV infection, HCV-specific CD4+ T cell responses are relatively weak or absent whereas in resolved infection these responses are vigorous and multispecific. Persons with a T-helper type I profile, which promotes cellular effector mechanisms are thought to be more likely to experience viral clearance, but the overall role of these cells in the immunopathogenesis of chronic liver disease is not known. To define this, much more data is required on the function and specificity of virus-specific CD4+ T cells, especially in the early phases of acute disease and in the liver during chronic infection. The role and possible mechanisms of action of CD4+ T cell responses in determining the outcome of acute and chronic HCV infection will be discussed in this review.

T-cell responses and previous exposure to hepatitis C virus in indeterminate blood donors.

Blood donors are routinely screened for hepatitis C virus infection. Some individuals have weak or restricted virus-specific antibody responses, and are classed as indeterminate. Such donors are almost always negative for viral RNA in blood. We postulated that previous transient virus exposure might account for some of these cases. With sensitive ex-vivo analyses of T-cell responses, we identified virus-specific responses in 15 of 30 indeterminate blood donors tested, compared with none in controls (p=0.0013). Additionally, these responses were typically focused on core-derived peptides. These findings suggest previous exposure to the virus in many indeterminate blood donors.

Pervasive influence of hepatitis C virus on the phenotype of antiviral CD8+ T cells.

Recent studies using MHC class I tetramers have shown that CD8(+) T cell responses against different persistent viruses vary considerably in magnitude and phenotype. At one extreme, hepatitis C virus (HCV)-specific CD8(+) T cell responses in blood are generally weak and have a phenotype that is perforin low and CCR7 high (early memory). At the other, specific responses to CMV are strong, perforin high, and CCR7 low (mature or effector memory). To examine the potential mechanisms behind this diversity, we compared CMV-specific responses in HCV-infected and healthy individuals. We find a striking difference in the phenotype of CMV-specific CD8(+) T cells between these groups. In the HCV-infected cohort, CMV-specific CD8(+) T cells lost markers associated with maturity; they had increased expression of CCR7 and reduced expression of Fas and perforin. They nevertheless responded to Ag in vitro in a manner similar to controls, with strong proliferation and appropriate acquisition of effector memory markers. The reduction in mature CD8 T cells in HCV-infected individuals may arise through either impairment or regulation of T cell stimulation, or through the early loss of mature T cells. Whatever the mechanism, HCV has a pervasive influence on the circulating CD8(+) T cell population, a novel feature that may be a hallmark of this infection.