Multiomics identifies the link between intratumor steatosis and the exhausted tumor immune microenvironment in hepatocellular carcinoma.

BACKGROUND AND AIMS: Immunotherapy has become the standard-of-care treatment for hepatocellular carcinoma (HCC), but its efficacy remains limited. To identify immunotherapy-susceptible HCC, we profiled the molecular abnormalities and tumor immune microenvironment (TIME) of rapidly increasing nonviral HCC. APPROACHES AND RESULTS: We performed RNA-seq of tumor tissues in 113 patients with nonviral HCC and cancer genome sequencing of 69 genes with recurrent genetic alterations reported in HCC. Unsupervised hierarchical clustering classified nonviral HCCs into three molecular classes (Class I, II, III), which stratified patient prognosis. Class I, with the poorest prognosis, was associated with TP53 mutations, whereas class III, with the best prognosis, was associated with cadherin-associated protein beta 1 (CTNNB1) mutations. Thirty-eight percent of nonviral HCC was defined as an immune class characterized by a high frequency of intratumoral steatosis and a low frequency of CTNNB1 mutations. Steatotic HCC, which accounts for 23% of nonviral HCC cases, presented an immune-enriched but immune-exhausted TIME characterized by T cell exhaustion, M2 macrophage and cancer-associated fibroblast (CAF) infiltration, high PD-L1 expression, and TGF-ß signaling activation. Spatial transcriptome analysis suggested that M2 macrophages and CAFs may be in close proximity to exhausted CD8+ T cells in steatotic HCC. An in vitro study showed that palmitic acid-induced lipid accumulation in HCC cells upregulated PD-L1 expression and promoted immunosuppressive phenotypes of cocultured macrophages and fibroblasts. Patients with steatotic HCC, confirmed by chemical-shift MR imaging, had significantly longer PFS with combined immunotherapy using anti-PD-L1 and anti-VEGF antibodies. CONCLUSIONS: Multiomics stratified nonviral HCCs according to prognosis or TIME. We identified the link between intratumoral steatosis and immune-exhausted immunotherapy-susceptible TIME.

Improved Liver Function After Sustained Virologic Response Enhanced Prognosis in Hepatitis C with Compensated Advanced Liver Fibrosis.

BACKGROUND AND AIM: Liver function can be improved in patients with chronic hepatitis C virus (HCV) infection who achieved sustained virologic response (SVR) with direct-acting antiviral (DAA) treatment. However, to our knowledge, the impact of liver function improvement after SVR on prognosis has not been investigated. METHODS: A total of 716 patients with chronic HCV infection and compensated advanced liver fibrosis who began receiving DAA treatment between September 2014 and August 2018 in 25 Japanese hospitals and achieved SVR were enrolled. RESULTS: The median age was 73 years, and 336 (47%) and 380 (53%) patients had albumin-bilirubin (ALBI) grade 1 and grade 2, respectively. Improvement to ALBI grade 1 at 1 year after the end of treatment (EOT) was observed in 76% of the patients with baseline ALBI grade 2. Among 380 patients with baseline ALBI grade 2, alanine aminotransferase (ALT) levels ≥ 40 U/L (p < 0.001) and modified ALBI (mALBI) grade 2a (p < 0.001) were significantly associated with improvement to ALBI grade 1 at 1 year after EOT in multivariate analysis. During the median observation period of 51.8 months, 4 and 10 patients with baseline ALBI grade 1 and 2, respectively, died. In patients with baseline ALBI grade 2, only the absence of improvement to ALBI grade 1 at 1 year after EOT was significantly associated with all-cause mortality in univariate analysis. CONCLUSIONS: Baseline ALT levels and mALBI grade were significantly associated with improvement in liver function after SVR. Patients whose liver function improved after SVR could have better prognosis.

[Rectal cancer with multiple metastases complicated by Crohn's disease 5 years after surgery:a case report].

In recent years, with the rising incidence of patients having long-term Crohn's disease, there has been an increase in the number of reports of carcinogenesis from dysplasia with chronic inflammation as the primary pathogenic factor. We hereby report a case of multiple metastases that appeared 5 years after surgery, in a patient with rectal cancer who had Crohn's disease. A man in his 50s was diagnosed with Crohn's disease which affected his small and large intestines 21 years back. The patient was being treated with oral steroids, 5-aminosalicylic acid, and modified nutrition. Infliximab was added to the treatment after it was introduced 11 years ago. He also had a history of rectal cancer and had undergone surgery for the same 5 years back. He was diagnosed with stage II cancer, and had not received any adjuvant chemotherapy. However, 5 years after surgery, multiple metastases recurred, and chemotherapy with mFOLFOX6 was administered. Additionally, for treating his Crohn's disease, which was also active, infliximab was changed to vedolizumab;however, the patient died a year later. Colorectal cancer accompanied with Crohn's disease has a higher risk of developing metastasis and is associated with poorer prognosis as compared to the noncomplicated colorectal cancer. Regarding treatment modalities, while searching for multidisciplinary treatment methods centered on surgical treatment in collaboration with medical oncologists and radiologists, the safety of treatment for Crohn's disease in patients with cancer must be borne in mind. The rising prevalence of cases of colorectal cancer with Crohn's disease is expected to lead to the formulation of specialized diagnostic and treatment strategies for these patients.

Comparison of atezolizumab plus bevacizumab and lenvatinib in terms of efficacy and safety as primary systemic chemotherapy for hepatocellular carcinoma.

AIM: Atezolizumab plus bevacizumab and lenvatinib have each shown efficacy as primary systemic chemotherapies for hepatocellular carcinoma (HCC) in clinical trials. However, comparative trials of these two treatments have not been conducted. This study aimed to compare the therapeutic outcomes of these two treatments. METHODS: This prospectively registered multicenter study analyzed 272 patients with HCC who received atezolizumab plus bevacizumab (the Atezo + Beva group; n = 90) or lenvatinib (the Len group; n = 182) as primary systemic chemotherapy. After propensity score matching (PSM), 66 patients were assigned to each group. RESULTS: After PSM, the median progression-free survival (PFS) was significantly longer in the Atezo + Beva group than in the Len group (8.8 vs. 5.2 months; p = 0.012). No significant differences were noted between the two groups in terms of median overall survival (not reached vs. 20.6 months; p = 0.577), objective response rates (43.8% vs. 52.4%; p = 0.330), and disease control rates (76.6% vs. 82.5%; p = 0.404). The percentage of patients with modified albumin-bilirubin grades of one or 2a was maintained during treatment in the Atezo + Beva group but decreased over time in the Len group. The rate of discontinuation due to adverse events (AEs) was lower in the Atezo + Beva group than in the Len group (12.1% vs. 28.8%; p = 0.018). CONCLUSIONS: Atezolizumab plus bevacizumab showed prolonged PFS, maintained hepatic reserve, and had lower rates of severe AEs compared with that on using lenvatinib as primary systemic chemotherapy for HCC.

Hyperprogressive disease in patients with unresectable hepatocellular carcinoma receiving atezolizumab plus bevacizumab therapy.

BACKGROUND: Atezolizumab plus bevacizumab was approved for hepatocellular carcinoma (HCC) patients in 2020, but treatment outcomes of atezolizumab plus bevacizumab in real-world settings remain unclear. Hyperprogressive disease (HPD), an acceleration of tumor growth occurring in some types of malignancies treated with immune checkpoint inhibitors, was assessed in HCC patients receiving atezolizumab plus bevacizumab. METHODS: Tumor growth kinetics (TGK) and tumor growth rate (TGR) were calculated at pre- and post-treatment in 88 Japanese patients with HCC receiving atezolizumab plus bevacizumab. Hyperprogressive disease was defined as progressive disease (PD) with ≥ two-fold increase in TGK and TGR. The association of baseline characteristics with HPD was analyzed. RESULTS: The best objective responses were partial response, stable disease, and PD in 12 (13.6%), 51 (58.0%), and 25 (28.4%) patients, respectively. The median progression-free survival was 5.0 months. Eleven (12.5%) and 9 (10.2%) patients had a TGK ratio and a TGR ratio of ≥2, respectively. Hyperprogressive disease was observed in nine patients (10.2%) and they showed significantly shorter overall survival than patients without HPD (median, 4.3 months vs. not reached; p < 0.001). Patients with HPD had larger and more intrahepatic tumors, higher levels of α-fetoprotein and lactate dehydrogenase, and higher neutrophil-to-lymphocyte ratio (NLR) at baseline than patients without HPD. NLR of ≥3 at baseline was identified as the only independent factor associated with HPD in multivariate analysis. CONCLUSIONS: Hyperprogressive disease was observed in 10.2% of HCC patients receiving atezolizumab plus bevacizumab, and an elevated NLR at baseline had an increased risk of HPD.

Risk of hepatocellular carcinoma after sustained virologic response in hepatitis C virus patients without advanced liver fibrosis.

AIM: Hepatocellular carcinoma (HCC) after sustained virologic response (SVR) has been observed even in hepatitis C virus (HCV) patients without advanced liver fibrosis. Identifying predictors for HCC incidence in patients without advanced liver fibrosis will enable efficient post-SVR HCC surveillance. This study aimed to develop a scoring system to predict the incidence of HCC after SVR in HCV patients without advanced liver fibrosis. METHODS: A total of 1682 HCV patients without advanced liver fibrosis (defined as Fibrosis-4 index <3.25) with no history of HCC who initiated direct-acting antiviral treatment between September 2014 and October 2020 at 26 institutions, and achieved SVR24, were included. We divided 1682 patients into training (1122) and validation (560) cohorts. RESULTS: In the multivariate analysis, baseline age ≥ 65 years (p = 0.030), alanine aminotransferase (ALT) levels at SVR24 ≥ 30 U/l (p = 0.001), and α-fetoprotein (AFP) levels at SVR24 ≥ 5.0 ng/ml (p = 0.001) were independent predictors for HCC incidence in the training cohort. We developed a scoring system to predict HCC incidence after SVR24 using these three factors (1 point was added for each factor). The cumulative HCC incidence rates at 5 years were 7.1% in patients who scored 2 or 3, and no patients developed HCC in those who scored 0 in the validation cohort. CONCLUSIONS: Our scoring system using the three factors of baseline age, ALT levels at SVR, and AFP levels at SVR is useful for post-SVR HCC surveillance of patients without advanced liver fibrosis.

Prediction Model for Intrahepatic Distant Recurrence After Radiofrequency Ablation for Primary Hepatocellular Carcinoma 2 cm or Smaller.

BACKGROUND: Intrahepatic hepatocellular carcinoma (HCC) has a high recurrence rate after radiofrequency ablation (RFA). However, to date, no standalone predictive factors for intrahepatic distant recurrence after curative ablation have been reported. AIMS: The aim of this study was to investigate predictive factors for intrahepatic distant recurrence after curative treatment with RFA for HCCs. METHODS: This multicenter study consisted of 17 institutions that registered 821 patients. The risk factors for intrahepatic distant recurrence after complete ablation by RFA for primary HCC ≤ 2 cm in diameter were identified in a retrospectively collected training set (n = 636) and then validated in a prospectively collected validation set (n = 185). RESULTS: The cumulative intrahepatic distant and local recurrence rates (i.e., entire recurrence rate) in the training set were 23.6% and 53.7% at 1 and 3 years, respectively. The cumulative intrahepatic distant recurrence rates in the training set were 17.0% and 43.8% at 1 and 3 years, respectively. Multivariate analysis of the training set showed that tumor number and serum levels of α-fetoprotein (AFP) and des-γ-carboxy prothrombin (DCP) were independent risk factors for both entire recurrence and intrahepatic distant recurrence. Intrahepatic distant recurrence risk in both the training and validation cohorts was stratified using a scoring system with three factors: tumor number (single or multiple), AFP (< 10 ng/ml or ≥ 10 ng/ml), and DCP (< 50 mAU/ml or ≥ 50 mAU/ml). CONCLUSION: The scoring system composed of tumor number, AFP, and DCP is useful for classifying the risk of intrahepatic distant recurrence after curative ablation for HCC.

[A case of severe colitis induced by the administration of pembrolizumab for pulmonary adenocarcinoma in a patient with ulcerative colitis].

Pembrolizumab is an immunoglobulin G4 isotype antibody that targets the programmed cell death protein 1 (PD-1) receptor of lymphocytes. It is used in the treatment of advanced non-small cell lung cancer (NSCLC). The safety and efficacy of immunotherapy for autoimmune disease are currently unknown;immune-related adverse events induced by immune checkpoint inhibitors (ICIs) have been reported. We report a case of severe colitis induced by the administration of pembrolizumab for pulmonary adenocarcinoma in a patient with ulcerative colitis. A 72-year-old man with a 3-year history of ulcerative colitis maintained clinical remission with mesalazine. The recurrence of lung adenocarcinoma was diagnosed and treated with pembrolizumab as second-line treatment. Diarrhea and bloody stool recurred 5 months after the first administration of pembrolizumab. The colitis did not respond to corticosteroids and infliximab. Because of the recurrence of ulcerative colitis, treatment of the lung adenocarcinoma was discontinued, and the patient died 1 year after the first administration of pembrolizumab. Few cases of severe colitis induced by the administration of pembrolizumab in patients with ulcerative colitis have been reported. This case suggests that the clinical stratification of autoimmune disease and typical standards of effectiveness of treatment are needed for patients with autoimmune disease who are treated with ICIs.

Therapeutic efficacy of lenvatinib in hepatocellular carcinoma patients with portal hypertension.

AIM: Preserved liver function may be an important factor affecting therapeutic efficacy in hepatocellular carcinoma patients treated with lenvatinib, but not all patients can be treated while preserving liver function. This study evaluated the therapeutic efficacy of lenvatinib in patients with poor liver function with and without portal hypertension. METHODS: This prospectively registered multicenter study analyzed 93 patients treated with lenvatinib. Progression-free survival was compared between patients with and without advanced portal hypertension according to baseline liver function. Advanced portal hypertension was defined as having both splenomegaly and any portosystemic collaterals. RESULTS: A total of 37 patients (40.7%) had advanced portal hypertension. Progression-free survival did not differ between patients with and without advanced portal hypertension in the entire cohort (median 7.6 vs. 4.1 months, respectively; P = 0.148), but was significantly longer in patients with advanced portal hypertension than in those without advanced portal hypertension in the albumin-bilirubin grade 2 or 3 group (median 7.6 vs. 2.1 months, respectively; P = 0.016). In a multivariate analysis, the presence of advanced portal hypertension was identified as the only significant predictor associated with prolonged progression-free survival in the albumin-bilirubin grade 2 or 3 group. CONCLUSIONS: Advanced portal hypertension was associated with the therapeutic efficacy of lenvatinib in controlling the progression of hepatocellular carcinoma in patients with poor liver function.

[A case of idiopathic thrombocytopenic purpura development after total colectomy for ulcerative colitis].

Ulcerative colitis (UC) is known to be associated with extraintestinal manifestations. However, idiopathic thrombocytopenic purpura (ITP) has rarely been reported as one of the extraintestinal manifestations in UC. In most cases, ITP develops as an extraintestinal manifestation during the treatment for UC. After treatment with medications or colectomy, there is often a remission of UC and ITP. However, we experienced a case of ITP development after total colectomy for UC. An 83-year-old man was diagnosed as having UC and started treatment with medications. After 3 years, total colectomy and ileostomy were performed to prevent UC remission. Subsequently, no further treatment was provided. Two years later, he presented to the hematology department in our hospital with the chief complaint of thrombocytopenia and was diagnosed as having ITP. ITP was treated with steroids, and his platelet count increased to within the normal range. Immunological abnormalities may be involved in the development of extraintestinal manifestation, including UC-associated ITP. In previous reports, ITP was cured by colectomy for UC. In contrast, peripheral arthritis is a common extraintestinal manifestation of UC, and it is known that 75% of these patients develop or continue to experience such symptoms after colectomy. Some extraintestinal manifestations may equally persist after colectomy. However, the underlying mechanisms are poorly understood. Ileitis and small intestinal and duodenal inflammation are all known bowel complications associated with colectomy, and some immunological mechanisms have been suggested to be involved. Therefore, careful monitoring in these patients is necessary to detect any possibility of developing extraintestinal manifestations after colectomy. Further studies to examine the mechanisms underlying the immunological abnormality between UC and extraintestinal manifestations such as ITP are needed.

Outbreak of hepatitis A linked to European outbreaks among men who have sex with men in Osaka, Japan, from March to July 2018.

AIM: Ongoing hepatitis A outbreaks among men who have sex with men (MSM) have been reported worldwide, mainly in Europe, since 2016. In Japan, there has been an increase in the number of notified hepatitis A cases since January 2018, most of which were suspected to have been transmitted through homosexual contact. In this paper, we describe the current outbreak situation of hepatitis A among MSM. METHODS: Between March and July 2018, 13 cases of hepatitis A were identified in our hospital. All cases were identified as MSM. Data on clinical and laboratory findings and therapies were collected from medical records. Serum or stool samples were obtained from 13 patients and subjected to sequence analysis. RESULTS: Of all patients, 12 reported to have male-to-male homosexual contact within 7 weeks prior to symptom onset, and 6 visited sex-on-premises venues in the same area. Furthermore, 12 patients were infected with HIV and consequently received antiretroviral therapy with sustained viral suppression. Ten patients received pulsed methylprednisolone therapy. Plasma exchange was additionally carried out in one patient. All patients received inpatient hospital care and were discharged alive. Sequence information, which was available in all cases, showed that the hepatitis A virus strain was identical to the EuroPride strain (RIVM-HAV16-090). CONCLUSIONS: Results of sequence analysis suggest that the ongoing hepatitis A outbreak among MSM in Japan is linked to the 2016 European outbreaks. A vaccination program is urgently required for high-risk populations to control this ongoing outbreak.

Favorable outcome with direct-acting antiviral treatment in hepatitis C patients coinfected with HIV.

AIM: To investigate the efficacy and safety of all-oral direct-acting antiviral treatments in patients coinfected with hepatitis C virus (HCV) and HIV. METHODS: In all, 35 patients with HCV/HIV coinfection (22 patients with HCV genotype 1 infection, 6 with genotype 2, and 7 with genotype 3) were treated with sofosbuvir and ledipasvir (for genotype 1 patients) or sofosbuvir and ribavirin (for genotypes 2 and 3). Sustained virological response (SVR) at 24 weeks after end of treatment and adverse events were assessed. RESULTS: The overall SVR rate was 91.4% (32/35). One patient with genotype 1 infection discontinued treatment on day 2 due to severe headache, which subsided after the cessation of medication; all other patients completed their treatment without severe adverse events. Two patients who had a relapse of HCV were infected with a genotype 3 strain. We observed hyperbilirubinemia in a patient with genotype 3, who was under antiretroviral therapy including atazanavir. He completed the treatment and achieved SVR. CONCLUSION: Direct-acting antiviral treatment for patients coinfected with HCV/HIV is as effective as in patients infected only with HCV. It was generally well tolerated, except in one patient who discontinued the treatment due to severe headache.

Incidence and risk factors of hepatocellular carcinoma change over time in patients with hepatitis C virus infection who achieved sustained virologic response.

AIM: In patients with chronic hepatitis C, hepatocellular carcinoma (HCC) occurs at a certain frequency, even if a sustained virologic response (SVR) is achieved by antiviral treatment. Old age, liver fibrosis, and high post-treatment α-fetoprotein (AFP) level are typical risk factors of post-SVR HCC. We examined whether the frequencies and factors of HCC in patients with an SVR achieved from interferon treatment changed. Methods Among patients prospectively registered for pegylated interferon and ribavirin treatment, 2021 with an SVR without HCC development during the treatment period were followed up. The mean observation period was 49.5 ± 26.2 months. RESULTS: The multivariable Cox regression analysis showed that older age, diabetes mellitus, advanced liver disease, and higher post-treatment AFP level were the independent risk factors throughout the observation period. The annual occurrence rate of HCC was 0.74% in the third year, 0.54% in the fourth year, and 0.40% in the fifth year; it gradually decreased from the third year. Because the time course hazards for HCC changed at 48 months, we separately analyzed its risk factors before and after this change point. The multivariable Cox regression analysis showed that the four above-mentioned factors were significantly related to HCC development within 4 years. Conversely, the univariable Cox regression analysis only identified diabetes mellitus as a significant factor for HCC development after 4 years. CONCLUSION: The frequency of HCC in hepatitis C patients who achieved an SVR from interferon treatment decreased during the observation period, and its risk factors changed between the early and late periods.

[A case of refractory pouchitis following surgery for ulcerative colitis successfully treated with adalimumab].

Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) is widely accepted as the operation of choice for refractory ulcerative colitis (UC), UC with dysplasia or cancer, or familial adenomatous polyposis. Pouchitis is the most frequent complication after IPAA for UC. Although the pathogenesis of pouchitis remains unclear, current evidence suggests that dysbiosis and mucosal immune response are important mechanisms. Antibiotics are the first-line treatment for the condition, but some patients develop chronic refractory pouchitis. Such cases can be treated with regimens such as longer courses of antibiotic combinations, mesalazine, corticosteroids, probiotics, or biologics. But if pouch inflammation is not ameliorated, a permanent ileostomy may be required. A 40-year-old man had undergone IPAA for UC and was diagnosed with pouchitis according to the Pouchitis Disease Activity Index. Antibiotics, mesalazine, and corticosteroids were given, but the inflammation was difficult to control. He developed chronic refractory pouchitis associated with perianal abscesses and anal fistulae. Following a seton procedure for fistulae, adalimumab (ADA) was administered. After 42 weeks, the ulcers in the pouch became scarred, and the anal fistulae were closed endoscopically. After remission was induced, it has been maintained. ADA is a fully human anti-tumor necrosis factor-α (TNF-α) monoclonal antibody that has been successfully used to treat refractory Crohn disease of the ileoanal pouch. Although some studies report that infliximab, a chimeric anti-TNF-α monoclonal antibody, is efficacious in patients with refractory pouchitis, clinical evidence for the use of ADA is limited. This case illustrates achievement of induction and maintenance of remission of refractory pouchitis with ADA. It is possible that patients with this condition can avoid a permanent ileostomy with anti-TNF-α therapy. In the near future, further study of long-term clinical outcomes of anti-TNF-α therapy is expected.

Peritoneal Seeding after Gastric Perforation during Endoscopic Submucosal Dissection for Gastric Cancer.

BACKGROUND/AIMS: Since the risk of cancer cells seeding the peritoneum after perforation during endoscopic submucosal dissection (ESD) is unclear, we retrospectively examined peritoneal relapse after gastric perforation during ESD for gastric cancer at a single institution. METHODS: Of 876 patients who underwent ESD for early gastric cancer between January 2002 and December 2015, 22 patients (2.5%) experienced gastric perforation during ESD at the Osaka National Hospital in Osaka, Japan. Clinical data from these 22 patients were reviewed for information on pathology, clinical course, and evidence of peritoneal dissemination. RESULTS: Patients were followed for a median of 55 (range 2-108) months. Two patients had peritoneal seeding following perforation during ESD. Multivariate analysis to explore the influence of clinical factors on the peritoneal seeding revealed that an intra-abdominal fluid collection on the CT imaging just after ESD, tumor location at the upper lesion of stomach, and pathologically marginal invasion were independently associated with an incidence of peritoneal relapse. CONCLUSION: Although rare, we should recognize the possibility of cancer cells seeding the peritoneum after perforation during gastric ESD.

Indoleamine-2,3-dioxygenase as an effector and an indicator of protective immune responses in patients with acute hepatitis B.

UNLABELLED: Indoleamine-2, 3-dioxygenase (IDO), an interferon-γ-inducible enzyme catalyzing tryptophan into kynurenine, exerts dual functions in infectious diseases, acting as a suppressor of intracellular pathogens and as an immune regulator. We explored the roles of IDO in hepatitis B virus (HBV) clearance from infected patients. We examined IDO activity, serum chemokines, and cytokines in 53 HBV-positive patients (25 acute hepatitis, 14 chronic hepatitis, and 14 hepatic flare) and 14 healthy volunteers. In order to clarify the mechanisms of IDO induction and its impact on HBV replication, we used a culture model consisting of human natural killer cells, plasmacytoid dendritic cells, and HBV-transfected Huh7 cells in which IDO expression is controlled. A robust activation of IDO with an inverse correlation of alanine aminotransferase at the peak was observed in patients with acute hepatitis B but not in patients with hepatic flare. In acute hepatitis patients who eventually cleared HBV, IDO activity, chemokine (C-X-C motif) ligand 9 (CXCL9), CXCL10, and CXCL11 increased at the peak of alanine aminotransferase. In contrast, in patients with hepatic flare, IDO activity remained at lower levels during the observation period, regardless of the surge of CXCL9, CXCL10, and CXCL11 at the alanine aminotransferase peak. Natural killer cells and plasmacytoid dendritic cells synergistically produced interferon-γ and interferon-α, thereby enhancing IDO activity and HBV suppression in Huh7 cells. Such suppressor capacity of IDO on HBV was abrogated in IDO-knockout cells and recovered by the reinduction of IDO in the cells. CONCLUSION: IDO is an anti-HBV effector and an indicator of subsequent immune responses operative during the early phase of infection; its activity is boosted by coexisting natural killer cells and plasmacytoid dendritic cells.