Anti-spike antibodies and neutralising antibody activity in people living with HIV vaccinated with COVID-19 mRNA-1273 vaccine: a prospective single-centre cohort study.

BACKGROUND: Vaccines against COVID-19 are a powerful tool to control the current SARS-CoV-2 pandemic. A thorough description of their immunogenicity among people living with HIV (PLWHIV) is necessary. We aimed to assess the immunogenicity of the mRNA-1273 vaccine among PLWHIV. METHODS: In this prospective cohort, adult PLWHIV outpatients were enrolled during the Italian vaccination campaign. Enrolment was allowed irrespective of ongoing combination antiretroviral therapy (ART), plasma HIV viral load and CD4+ T cell count. A two-dose regimen of mRNA-1273, with administrations performed 28 days apart, was employed. The primary outcomes were anti-spike (anti-S) antibody titres and neutralising antibody activity, assessed 28 days after completing the vaccination schedule. A convenient sample of individuals not affected by HIV was also collected to serve as control (referred as healthy-donors, HDs). FINDINGS: We enrolled 71 PLWHIV, mostly male (84·5%), with a mean age of 47 years, a median CD4+ T cell count of 747·0 cells per µL and a median HIV viral load <50 copies/mL. COVID-19-experienced PLWHIV displayed higher anti-S antibody titres (p=0·0007) and neutralising antibody activity in sera (p=0·0007) than COVID-19-naïve PLWHIV. When stratified according to CD4+ T cell count (<350 cells/µL, 350-500 cells/µL, >500 cells/µL), anti-S antibody titres (6/71, median 2173 U/mL [IQR 987-4109]; 7/71, 5763 IU/mL [IQR 4801->12500]; 58/71, 2449 U/mL [IQR 1524-5704]) were not lower to those observed among HDs (10, median 1425 U/mL [IQR 599-6131]). In addition, neutralising antibody activity, stratified according to the CD4+ T cell count (6/71, median 1314 [IQR 606-2477]; 7/71, 3329 IU/mL [IQR 1905-10508]; 58/71, 1227 U/mL [IQR 761-3032]), was like those displayed by HDs (10, median 2112 U/mL [IQR 719-8889]). INTERPRETATION: In our cohort of PLWHIV with well-controlled ART, stable viral suppression and robust CD4+ T cell count, inoculation with mRNA-1273 vaccine given 4 weeks apart produced detectable humoral immune response, similar to individuals without HIV infection, supporting vaccination in PLWHIV. FUNDING: This study was partially supported by Italian Ministry of Health Ricerca Corrente 2021, by Intesa San Paolo COVID-19 emergency 2020 funds, and by Fondazione Cariplo Grant (INNATE-CoV).

A challenging case of SARS-CoV-2- AIDS and Nocardiosis coinfection from the SMatteo COvid19 REgistry (SMACORE).

The COVID-19 pandemic is posing an unprecedented threat worldwide. One issue that has faltered, though, concerns the underestimated risk to trade all for COVID-19, misdiagnosing other potentially life-threatening diseases. Further still, the presence of respiratory symptoms in AIDS patients should stimulate more vigilant efforts to uncover other or additional infections. This case report highlights the pitfalls of diagnosing a rare pulmonary infection during the COVID-19 pandemic.

Association of Toll-like receptor 7 variants with life-threatening COVID-19 disease in males: findings from a nested case-control study.

Background: Recently, loss-of-function variants in TLR7 were identified in two families in which COVID-19 segregates like an X-linked recessive disorder environmentally conditioned by SARS-CoV-2. We investigated whether the two families represent the tip of the iceberg of a subset of COVID-19 male patients. Methods: This is a nested case-control study in which we compared male participants with extreme phenotype selected from the Italian GEN-COVID cohort of SARS-CoV-2-infected participants (<60 y, 79 severe cases versus 77 control cases). We applied the LASSO Logistic Regression analysis, considering only rare variants on young male subsets with extreme phenotype, picking up TLR7 as the most important susceptibility gene. Results: Overall, we found TLR7 deleterious variants in 2.1% of severely affected males and in none of the asymptomatic participants. The functional gene expression profile analysis demonstrated a reduction in TLR7-related gene expression in patients compared with controls demonstrating an impairment in type I and II IFN responses. Conclusions: Young males with TLR7 loss-of-function variants and severe COVID-19 represent a subset of male patients contributing to disease susceptibility in up to 2% of severe COVID-19. Funding: Funded by private donors for the Host Genetics Research Project, the Intesa San Paolo for 2020 charity fund, and the Host Genetics Initiative. Clinical trial number: NCT04549831.

Adaptive Natural Killer Cell Functional Recovery in Hepatitis C Virus Cured Patients.

BACKGROUND AND AIMS: Current evidence suggests that dysfunctional natural killer (NK) cell responses during hepatitis C virus (HCV) infection can be restored after viral eradication with direct acting antivirals (DAAs). However, the fate of the recently described adaptive NK cell population, endowed with increased ability to mediate antibody-dependent cell-mediated cytotoxicity (ADCC), during HCV infection is poorly defined, while no study has explored the effects of DAAs on this NK subset. APPROACH AND RESULTS: We performed multicolor flow cytometry to investigate CD57+ FcεRIγneg adaptive and FcεRIγpos conventional NK cell phenotype and function before and after DAA treatment in 59 patients chronically infected with HCV, 39 with advanced liver fibrosis, and 20 with mild-moderate liver fibrosis. Moreover, bulk NK cell phenotype and function were analyzed after cytokine activation following contact with K562 target cells. The proportion of FcεRIγneg NK cells in patients with HCV was associated with increased HCV load at baseline, and it was significantly reduced after treatment. Patients with an advanced fibrosis stage displayed increased NK cell activation and exhaustion markers that normalized after therapy. Of note, adaptive NK cells from patients with HCV were characterized by increased programmed death receptor 1 expression and reduced ADCC activity at baseline. DAA treatment restored ADCC ability and reduced programmed death receptor 1 expression. CONCLUSIONS: HCV profoundly affects the frequency, phenotype, and function of adaptive NK cells. DAA therapy restores a normal adaptive NK phenotype and enhances interferon-gamma production by this cell subset.

Unique immunological profile in patients with COVID-19.

The relationship between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and host immunity is poorly understood. We performed an extensive analysis of immune responses in 32 patients with severe COVID-19, some of whom succumbed. A control population of healthy subjects was included. Patients with COVID-19 had an altered distribution of peripheral blood lymphocytes, with an increased proportion of mature natural killer (NK) cells and low T-cell numbers. NK cells and CD8+ T cells overexpressed T-cell immunoglobulin and mucin domain-3 (TIM-3) and CD69. NK cell exhaustion was attested by increased frequencies of programmed cell death protein 1 (PD-1) positive cells and reduced frequencies of natural killer group 2 member D (NKG2D)-, DNAX accessory molecule-1 (DNAM-1)- and sialic acid-binding Ig-like lectin 7 (Siglec-7)-expressing NK cells, associated with a reduced ability to secrete interferon (IFN)γ. Patients with poor outcome showed a contraction of immature CD56bright and an expansion of mature CD57+ FcεRIγneg adaptive NK cells compared to survivors. Increased serum levels of IL-6 were also more frequently identified in deceased patients compared to survivors. Of note, monocytes secreted abundant quantities of IL-6, IL-8, and IL-1ß which persisted at lower levels several weeks after recovery with concomitant normalization of CD69, PD-1 and TIM-3 expression and restoration of CD8+ T cell numbers. A hyperactivated/exhausted immune response dominate in severe SARS-CoV-2 infection, probably driven by an uncontrolled secretion of inflammatory cytokines by monocytes. These findings unveil a unique immunological profile in COVID-19 patients that will help to design effective stage-specific treatments for this potentially deadly disease.

Patients with chronic hepatitis C receiving treatment with direct acting antivirals: How is this population changing?

BACKGROUND AND AIMS: Direct acting antiviral agents (DAAs) have revolutionized the landscape of chronic hepatitis C (CHC) enabling treatment of all those infected. It remains to be determined how the characteristics of those receiving treatment are changing. MATERIALS AND METHODS: We retrospectively analysed all the patients with CHC who received treatment with DAAs in a large referral centre since 01/01/2015. We stratified their demographic, clinical and virological characteristics at baseline and the sustained virological response (SVR) rates according to the year of treatment. RESULTS: In the study were included 2565 patients. During the study period, the yearly proportion of men and cirrhotic patients decreased (p<0.001) whereas mean age increased from 59.8 to 62.2 years old (p=0.04). An increasing trend was observed in the foreign-born patients from 4.3% to 7.9%, without reaching statistical significance. The prevalence of comorbidities had also increased during the study period (p<0.001). Instead, the yearly number of experienced patients decreased significantly (p<0.001) as well as the mean MELD score of cirrhotic patients from 9 to 7.6 (p<0.001). SVR rates increased significantly, from 93.4% in 2015 to 97.1% in 2018 (P<0.05). CONCLUSIONS: The population of patients with CHC receiving DAAs is becoming older and with more comorbidities. Nevertheless, this did not impact SVR rates.

The obesity paradox: Analysis from the SMAtteo COvid-19 REgistry (SMACORE) cohort.

BACKGROUND AND AIMS: Obesity has been suggested as a possible risk factor for a more severe course of COVID-19; however, conclusive evidence is lacking and few studies have investigated the role of BMI as a risk factor for admission to intensive care unit (ICU) and mortality. We retrospectively analyzed a COVID-19 cohort recruited during the first 40 days of the epidemic in Italy. We examined the association between obesity and 30-day mortality, admission to ICU, mortality and length of hospital stay in patients with COVID-19. METHODS AND RESULTS: Demographic, clinical and outcome data were retrospectively analyzed in 331 patients with COVID-19 admitted to hospital between 21 February and 31 March 2020. The predictive effect of obesity on mortality was assessed using a Cox proportional-hazard regression model, its effect on ICU admission and mortality in the ICU using logistic regressions, and its effect on length of hospital stay using a linear regression. Seventy-four of 331 patients had a BMI ≥30 kg/m2. Among obese patients, 21 (28.4%) required admission in ICU and 25 died (33.8%). After controlling for sex, age, comorbidities and clinical data, obesity was not significantly associated with mortality, mortality in ICU and length of hospital stay. The effect of obesity on ICU admission remained significant after controlling for sex, age, interstitial lung disease, heart disease and serum C-reactive protein. CONCLUSIONS: Obese patients with COVID-19 were more likely to be admitted to ICU than non-obese patients. However, there were no significant differences in mortality between the two groups.

Running out of bullets: The challenging management of acute hepatitis and SARS-COV-2 from the SMatteo COvid19 Registry (SMACORE).

Liver impairment is frequent in patients with novel coronavirus disease (COVID-19) and direct viral tropism for the liver has been proven. Since several of the currently administered drugs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are possibly hepatotoxic, the management of patients with COVID-19 and liver failure is still an almost unexplored field. Taking this challenging case of acute HBV with persistent hyperbilirubinemia and SARS-COV-2 infection with respiratory distress as a starting point, we here loop through this condition. Where the available therapeutic options are scarce, we here propose hemoperfusion (HP) as an attractive alternative to both delay any late-stage progression of hyper inflammation process in COVID-19 and remove the toxins involved in acute liver failure.

Early nutritional supplementation in non-critically ill patients hospitalized for the 2019 novel coronavirus disease (COVID-19): Rationale and feasibility of a shared pragmatic protocol.

OBJECTIVES: Beginning in December 2019, the 2019 novel coronavirus disease (COVID-19) has caused a pneumonia epidemic that began in Wuhan, China, and is rapidly spreading throughout the whole world. Italy is the hardest hit country after China. Considering the deleterious consequences of malnutrition, which certainly can affect patients with COVID-19, the aim of this article is to present a pragmatic protocol for early nutritional supplementation of non-critically ill patients hospitalized for COVID-19 disease. It is based on the observation that most patients present at admission with severe inflammation and anorexia leading to a drastic reduction of food intake, and that a substantial percentage develops respiratory failure requiring non-invasive ventilation or even continuous positive airway pressure. METHODS: High-calorie dense diets in a variety of different consistencies with highly digestible foods and snacks are available for all patients. Oral supplementation of whey proteins as well as intravenous infusion of multivitamin, multimineral trace elements solutions are implemented at admission. In the presence of 25-hydroxyvitamin D deficit, cholecalciferol is promptly supplied. If nutritional risk is detected, two to three bottles of protein-calorie oral nutritional supplements (ONS) are provided. If <2 bottles/d of ONS are consumed for 2 consecutive days and/or respiratory conditions are worsening, supplemental/total parenteral nutrition is prescribed. CONCLUSION: We are aware that our straight approach may be debatable. However, to cope with the current emergency crisis, its aim is to promptly and pragmatically implement nutritional care in patients with COVID-19, which might be overlooked despite being potentially beneficial to clinical outcomes and effective in preventing the consequences of malnutrition in this patient population.

Hepatitis C virus-induced NK cell activation causes metzincin-mediated CD16 cleavage and impaired antibody-dependent cytotoxicity.

BACKGROUND & AIMS: The Fc receptor family for immunoglobulin (Ig)G type III (FcγRIII, CD16) is an activating receptor on natural killer (NK) cells and an essential mediator of antibody-dependent cellular cytotoxicity (ADCC). There is only limited information on its role during chronic hepatitis C virus (HCV) infection. We studied CD16 expression in relation to NK cell functional activity in HCV-infected patients and sought mechanistic insights into virus-induced modulation. METHODS: NK cell CD16 expression and activation status were evaluated ex vivo by flow cytometry in HCV-infected patients and healthy controls (HC) as well as in vitro after co-culture with HCV-infected HuH7.5 cells. Rituximab-mediated ADCC was assessed in HC and HCV-infected patients using Daudi cells as a target. The role of metzincins in CD16 down-modulation was assessed using specific inhibitory molecules and by evaluating intracellular mRNA levels. RESULTS: HCV-infected patients exhibited increased frequencies of ex vivo activated NK cells and a concomitantly decreased NK CD16 expression, which resulted in impaired ADCC activity. Moreover, exposure of NK cells to culture-derived HCV recapitulated the ex vivo findings of decreased CD16 expression and increased NK cell activation. Importantly, blockade of metzincin-mediated shedding activity, including selective a disintegrin and metalloproteinase 17 (ADAM-17) inhibition, restored NK CD16 expression. Successful treatment with direct-acting antivirals partially improved NK ADCC function despite delayed CD16 reconstitution. CONCLUSION: Chronic HCV infection induces NK cell activation resulting in ADAM-17-dependent CD16 shedding and consequent impaired ADCC function. Altered ADCC may contribute to failure to eradicate HCV-infected hepatocytes. LAY SUMMARY: We show here that hepatitis C virus (HCV) activates natural killer (NK) lymphocytes which, as a consequence, loose their Fc receptor for IgG (CD16), an essential molecule for antibody binding. We show that this occurs through the action of enzymes named metzincins, resulting in altered NK-mediated antibody-dependent killing (ADCC) of target cells. This mechanism may contribute to HCV persistence and may represent a general phenomenon whereby some viruses can escape host's immune responses.

HCV intergenotype 2k/1b recombinant detected in a DAA-treated patient in Italy.

Direct-acting antiviral (DAA) combinations are potent and effective drugs currently recommended for treatment of chronic HCV infection. Difficult to treat genotypes are the most important predictors of treatment failure. We report a case of DAA treatment failure in an HCV-infected patient carrying a recombinant genotype 2k/1b. This strain, first isolated from a Russian patient in 2002, has now been observed for the first time in Italy.

Hepatitis C virus inhibits CD4 T cell function via binding to Toll-like receptor 7.

Toll-like receptor 7 (TLR7) is a ssRNA receptor that activates dendritic cells and macrophages upon ssRNA binding; however, little is known of its role in CD4+ T cells. We show here that hepatitis C virus (HCV) induces a dose dependent inhibition of cytokine production and expression of activation markers in CD4 T cells, which were restored by a TLR7-specific antagonist. These findings indicate that HCV induces CD4 T cell impairment via TLR7 which may contribute to failure of virus eradication, casting doubts on the use of TLR7 agonists to boost innate immunity in chronic RNA virus infections.

Lack of Siglec-7 expression identifies a dysfunctional natural killer cell subset associated with liver inflammation and fibrosis in chronic HCV infection.

OBJECTIVE: Sialic-acid-binding immunoglobulin-like lectin-7 (Siglec-7) is a natural killer (NK) cell inhibitory receptor associated with NK phenotypic and functional abnormalities in HIV-1 infection. We investigated the significance of NK-expressed and serum soluble Siglec-7 in relation to NK functional ability and parameters of liver necroinflammation and fibrosis in chronic HCV infection. DESIGN: NK-expressed and serum Siglec-7 were evaluated in 130 and 166 HCV-infected individuals by flow cytometry and ELISA, respectively. NK cell degranulation and cytokine secretion were determined by flow cytometry. 65 patients with chronic HBV infection, 84 with chronic biliary disorders and 168 healthy donors served as controls. RESULTS: Expression of Siglec-7 was significantly decreased on NK cells from HCV-infected and HBV-infected patients and, conversely, serum Siglec-7 was significantly increased in these patients compared with controls. The frequency of Siglec-7pos NK cells was significantly higher at baseline in sustained virological responders to pegylated interferon-α/ribavirin treatment than in non-responders. Activating receptor expression was significantly higher in Siglec-7pos NK cells and was associated with increased degranulation and cytokine secretion compared with Siglec-7neg cells. In chronic HCV infection, there was an inverse correlation between Siglec-7 expression and serum aminotransferases, γ-glutamyl transpeptidase, liver stiffness, aspartate aminotransferase to platelet ratio index and fibrosis-4 scores, and a positive correlation between serum Siglec-7 and the same clinical parameters, including histological staging. CONCLUSIONS: These findings identify Siglec-7neg NK cells as a dysfunctional subpopulation associated with severe liver disease in chronic HCV infection.

Efficacy of low-dose rituximab for the treatment of mixed cryoglobulinemia vasculitis: Phase II clinical trial and systematic review.

OBJECTIVE: To evaluate whether rituximab at a low dose of 250 mg/m(2) × 2 may be as effective as at higher dosages, most commonly 375 mg/m(2)×4, used in previous studies on the treatment of patients with refractory mixed cryoglobulinemia (MC) vasculitis associated with hepatitis C virus (HCV) infection. METHODS: We conducted a phase 2, single-arm two-stage trial (EUDRACT n. 2008-000086-38) of low-dose rituximab in 52 patients with HCV-associated MC who were ineligible/intolerant or non-responder to antiviral therapy. The primary outcomes were response of vasculitis evaluated by the Birmingham Vasculitis Activity Score (BVAS) at months 3, 6 and 12, rate of relapses and time to relapse, and rate of adverse events. Our data were compared with those reported in 19 published studies selected among 291 reviewed in a literature search. RESULTS: The cumulative response rate (complete and partial) at month 3 was 81% in our patients, and 86% in 208 patients from studies using high-dose rituximab. The relapse rate and median time to relapse were, respectively, 41% and 6 months in our study, and 32% and 7 months in high-dose studies. Treatment-related adverse events were 11.5% in our study and 19.9% in high-dose studies. None of these differences was statistically significant. CONCLUSION: Rituximab at a low dosage of 250 mg/m(2) × 2 is as effective as at higher dosages for treating MC vasculitis. This low-dose regimen may improve the cost/benefit profile of rituximab therapy for MC.

Epidemiological characteristics of bloodstream infections in patients with different degrees of liver disease.

Observational retrospective study to evaluate the etiology, the outcome and the risk factors of bloodstream infections (BSIs) in patients with liver disease. One hundred and forty-eight BSIs were diagnosed (infection rate: 0.60 per 100 days of hospital stay), 62 BSIs (41.9 %) were associated with Gram-positive bacteria (infection rate: 0.25 per 100 days of hospital stay) and 80 (54.4 %) with Gram-negative bacteria (infection rate: 0.32 per 100 days of hospital stay). Admission-associated mortality was higher in patients with BSI than in those without BSI (20.6 versus 5.0 %, p < 0.001). Patients with cirrhosis had an increased risk to develop a BSI compared with patients with chronic hepatitis, specifically for Gram-positive (and Staphylococcus spp)-related BSI.

Performance of liver stiffness measurements by transient elastography in chronic hepatitis.

AIM: To compare results of liver stiffness measurements by transient elastography (TE) obtained in our patients population with that used in a recently published meta-analysis. METHODS: This was a single center cross-sectional study. Consecutive patients with chronic viral hepatitis scheduled for liver biopsy at the outpatient ward of our Infectious Diseases Department were enrolled. TE was carried out by using FibroScan™ (Echosens, Paris, France). Liver biopsy was performed on the same day as TE, as day case procedure. Fibrosis was staged according to the Metavir scoring system. The diagnostic performance of TE was assessed by using receiver operating characteristic (ROC) curves and the area under the ROC curve analysis. RESULTS: Two hundred and fifty-two patients met the inclusion criteria. Six (2%) patients were excluded due to unreliable TE measurements. Thus, 246 (171 men and 75 women) patients were analyzed. One hundred and ninety-five (79.3%) patients had chronic hepatitis C, 41 (16.7%) had chronic hepatitis B, and 10 (4.0%) were coinfected with human immunodeficiency virus. ROC curve analysis identified optimal cut-off value of TE as high as 6.9 kPa for F ≥ 2; 7.9 kPa for F ≥ 3; 9.6 kPa for F = 4 in all patients (n = 246), and as high as 6.9 kPa for F ≥ 2; 7.3 kPa for F ≥ 3; 9.3 kPa for F = 4 in patients with hepatitis C (n = 195). Cut-off values of TE obtained by maximizing only the specificity were as high as 6.9 kPa for F ≥ 2; 9.6 kPa for F ≥ 3; 12.2 kPa for F = 4 in all patients (n = 246), and as high as 7.0 kPa for F ≥ 2; 9.3 kPa for F ≥ 3; 12.3 kPa for F = 4 in patients with hepatitis C (n = 195). CONCLUSION: The cut-off values of TE obtained in this single center study are comparable to that obtained in a recently published meta-analysis that included up to 40 studies.

Performance of real-time strain elastography, transient elastography, and aspartate-to-platelet ratio index in the assessment of fibrosis in chronic hepatitis C.

OBJECTIVE: The purpose of this article is to evaluate the diagnostic performance of transient elastography, real-time strain elastography, and aspartate-to-platelet ratio index in assessing fibrosis in patients with chronic hepatitis C by using histologic Metavir scores as reference standard. SUBJECTS AND METHODS: Consecutive patients with chronic hepatitis C scheduled for liver biopsy were enrolled. Liver biopsy was performed on the same day as transient elastography and real-time strain elastography. Transient elastography and real-time strain elastography were performed in the same patient encounter by a single investigator using a medical device based on elastometry and an ultrasound machine, respectively. Diagnostic performance was assessed by using receiver operating characteristic curves and area under the receiver operating characteristic curve (AUC) analysis. RESULTS: One hundred thirty patients (91 men and 39 women) were analyzed. The cutoff values for transient elastography, real-time strain elastography, and aspartate-to-platelet ratio index were 6.9 kPa, 1.82, and 0.37, respectively, for fibrosis score of 2 or higher; 7.3 kPa, 1.86, and 0.70, respectively, for fibrosis score of 3 or higher; and 9.3 kPa, 2.33, and 0.70, respectively, for fibrosis score of 4. AUC values of transient elastography, real-time strain elastography, aspartate-to-platelet ratio index were 0.88, 0.74, and 0.86, respectively, for fibrosis score of 2 or higher; 0.95, 0.80, and 0.89, respectively, for fibrosis score of 3 or higher; and 0.97, 0.80, and 0.84, respectively, for fibrosis score of 4. A combination of the three methods, when two of three were in agreement, showed AUC curves of 0.93, 0.95, and 0.95 for fibrosis scores of 2 or higher, 3 or higher, and 4, respectively. CONCLUSION: Transient elastography, real-time strain elastography, and aspartate-to-platelet ratio index values were correlated with histologic stages of fibrosis. Transient elastography offered excellent diagnostic performance in assessing severe fibrosis and cirrhosis. Real-time elastography does not yet have the potential to substitute for transient elastography in the assessment of liver fibrosis.

Impaired intrahepatic natural killer cell cytotoxic function in chronic hepatitis C virus infection.

UNLABELLED: Hepatitis C virus (HCV) persistence in the host results from inefficiencies of innate and adaptive immune responses. Most studies addressing the role of innate immunity concentrated on peripheral blood (PB) natural killer (NK) cells, whereas only limited information is available on intrahepatic (IH) NK cells. We therefore examined phenotypic and functional features of IH and PB NK cells in paired liver biopsy and venous blood samples from 70 patients with chronic HCV infection and 26 control persons subjected to cholecystectomy for gallstones as controls. Ex vivo isolated IH NK cells from HCV-infected patients displayed unique phenotypic features, including increased expression of NKp46-activating receptor in the face of reduced tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and cluster of differentiation (CD) 107a expression, which resulted in impaired degranulation compared with controls. To gain insights into the effect of HCV on NK cells, we exposed peripheral blood mononuclear cells (PBMCs) from patients and healthy donors to cell-culture-derived HCV (HCVcc) and measured NK cell degranulation, TRAIL, and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) expression. Exposure of PBMCs to HCVcc significantly boosted NK degranulation, pERK1/2, and TRAIL expression in healthy donors, but not in patients with chronic HCV infection, a defect that was completely reversed by interferon-alpha. Purified NK cells showed a minimal, though significant, increase in degranulation and TRAIL expression, both in patients and controls, after exposure to HCVcc. CONCLUSIONS: These findings indicate dysfunctional IH NK cell cytotoxicity associated with TRAIL down-regulation in chronic HCV infection, which may contribute to virus persistence. PB NK cell impairment upon exposure to HCVcc suggests the existence of an accessory cell-dependent NK cell lytic defect in chronic HCV infection predominantly involving the TRAIL pathway.