Incidence of development of hepatocellular carcinoma in Japanese patients infected with hepatitis B virus is equivalent between genotype B and C in long term.

Hepatitis B virus (HBV) genotypes B (HBV/B) and C (HBV/C) are the most prevalent genotypes among Japanese patients with hepatitis. Reportedly, HBV/C infection has been associated with more severe disease progression, manifesting as developing cirrhosis and hepatocellular carcinoma (HCC), than HBV/B infection. However, no long-term studies have examined the development of HCC in HBV/B-infected patients in Japan. The aims of our study were to compare the incidence of HCC in HBV/B- or HBV/C-infected patients. A total of 241 patients were followed up among 295 hepatitis B surface antigen (HBsAg)-positive carriers. Genotypes of HBV were A in 1% (4/295), B in 61% (179/295), C in 37% (110/295) and D in 1% (2/295) patients, and 96% of HBV/B were infected with subgenotype Bj. The mean age at HCC diagnosis was significantly higher in HBV/B than in HBV/C (67.0 ± 10.0 vs 57.7 ± 8.0 years, P < 0.001). The value of FIB-4 index was significantly higher in HBV/B than in HBV/C (P < 0.01). The rate of HCC was higher in HBV/C than in HBV/B, and a significant difference was observed until the 20-year observation period (P = 0.048). However, thereafter, HCC associated with HBV/B increased, and no significant difference was observed between HBV/B and HBV/C. HCC development was consistently observed even in HBV/B infection, especially among elderly patients with advanced fibrosis compared with HBV/C. HBV/B-infected patients developed HCC later in life, and in the long term, we found no differences in incidence of HCC development rates between these two genotypes.

Medium-chain triglycerides supplement therapy with a low-carbohydrate formula can supply energy and enhance ammonia detoxification in the hepatocytes of patients with adult-onset type II citrullinemia.

Citrin, encoded by SLC25A13, constitutes the malate-aspartate shuttle, the main NADH-shuttle in the liver. Citrin deficiency causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). Citrin deficiency is predicted to impair hepatic glycolysis and de novo lipogenesis, resulting in hepatic energy deficit. Secondary decrease in hepatic argininosuccinate synthetase (ASS1) expression has been considered a cause of hyperammonemia in CTLN2. We previously reported that medium-chain triglyceride (MCT) supplement therapy with a low-carbohydrate formula was effective in CTLN2 to prevent a relapse of hyperammonemic encephalopathy. We present the therapy for six CTLN2 patients. All the patients' general condition steadily improved and five patients with hyperammonemic encephalopathy recovered from unconsciousness in a few days. Before the treatment, plasma glutamine levels did not increase over the normal range and rather decreased to lower than the normal range in some patients. The treatment promptly decreased the blood ammonia level, which was accompanied by a decrease in plasma citrulline levels and an increase in plasma glutamine levels. These findings indicated that hyperammonemia was not only caused by the impairment of ureagenesis at ASS1 step, but was also associated with an impairment of glutamine synthetase (GS) ammonia-detoxification system in the hepatocytes. There was no decrease in the GS expressing hepatocytes. MCT supplement with a low-carbohydrate formula can supply the energy and/or substrates for ASS1 and GS, and enhance ammonia detoxification in hepatocytes. Histological improvement in the hepatic steatosis and ASS1-expression was also observed in a patient after long-term treatment.

Genome-Wide Association Study Identifies TLL1 Variant Associated With Development of Hepatocellular Carcinoma After Eradication of Hepatitis C Virus Infection.

BACKGROUND & AIMS: There is still a risk for hepatocellular carcinoma (HCC) development after eradication of hepatitis C virus (HCV) infection with antiviral agents. We investigated genetic factors associated with the development of HCC in patients with a sustained virologic response (SVR) to treatment for chronic HCV infection. METHODS: We obtained genomic DNA from 457 patients in Japan with a SVR to interferon-based treatment for chronic HCV infection from 2007 through 2015. We conducted a genome-wide association study (GWAS), followed by a replication analysis of 79 candidate single nucleotide polymorphisms (SNPs) in an independent set of 486 patients in Japan. The study end point was HCC diagnosis or confirmation of lack of HCC (at follow-up examinations until December 2014 in the GWAS cohort, and until January 2016 in the replication cohort). We collected clinical and laboratory data from all patients. We analyzed expression levels of candidate gene variants in human hepatic stellate cells, rats with steatohepatitis caused by a choline-deficient L-amino acid-defined diet, and a mouse model of liver injury caused by administration of carbon tetrachloride. We also analyzed expression levels in liver tissues of patients with chronic HCV infection with different stages of fibrosis or tumors vs patients without HCV infection (controls). RESULTS: We found a strong association between the SNP rs17047200, located within the intron of the tolloid like 1 gene (TLL1) on chromosome 4, and development of HCC; there was a genome-wide level of significance when the results of the GWAS and replication study were combined (odds ratio, 2.37; P = 2.66 × 10-8). Multivariate analysis showed rs17047200 AT/TT to be an independent risk factor for HCC (hazard ratio, 1.78; P = .008), along with male sex, older age, lower level of albumin, advanced stage of hepatic fibrosis, presence of diabetes, and higher post-treatment level of α-fetoprotein. Combining the rs17047200 genotype with other factors, we developed prediction models for HCC development in patients with mild or advanced hepatic fibrosis. Levels of TLL1 messenger RNA (mRNA) in human hepatic stellate cells increased with activation. Levels of Tll1 mRNA increased in liver tissues of rodents with hepatic fibrogenesis compared with controls. Levels of TLL1 mRNA increased in liver tissues of patients with progression of fibrosis. Gene expression levels of TLL1 short variants, including isoform 2, were higher in patients with rs17047200 AT/TT. CONCLUSIONS: In a GWAS, we identified the association between the SNP rs17047200, within the intron of TLL1, and development of HCC in patients who achieved an SVR to treatment for chronic HCV infection. We found levels of Tll1/TLL1 mRNA to be increased in rodent models of liver injury and liver tissues of patients with fibrosis, compared with controls. We propose that this SNP might affect splicing of TLL1 mRNA, yielding short variants with high catalytic activity that accelerates hepatic fibrogenesis and carcinogenesis. Further studies are needed to determine how rs17047200 affects TLL1 mRNA levels, splicing, and translation, as well as the prevalence of this variant among other patients with HCC. Tests for the TLL1 SNP might be used to identify patients at risk for HCC after an SVR to treatment of HCV infection.

[Treatment and Pathomechanism of Citrin Deficiency].

Citrin, encoded by SLC25A13, is a component of the malate-aspartate shuttle, which is the main NADH-transporting system in the liver. Citrin deficiency causes neonatal intrahepatic cholestasis (NICCD), which usually resolves within the first year of life. However, a small number of adults with citrin deficiency develop adult-onset type II citrullinemia (CTLN2), which causes hyperammonemic encephalopathy leading to death due to cerebral edema. Liver transplantation is the only definitive therapy for patients with CTLN2. Hepatic glycolysis is coupled with hepatic lipogenesis via the NADH shuttles composed of the malate-aspartate shuttle and malate-citrate shuttle. Citrin deficiency is expected to impair glycolysis and lipogenesis in hepatocytes. We noticed that a lactose (galactose)-restricted and medium-chain triglyceride (MCT)-supplemented formula is notably effective for patients with NICCD. We extended this therapy for CTLN2 and found that an MCT supplementation therapy under a low-carbohydrate formula prevented the relapse of hyperammonemic encephalopathy, normalized the liver dysfunction (including the Fisher ratio), and gradually improved the level of plasma citrulline and fatty liver. An MCT supplement can provide energy to hepatocytes and promote hepatic lipogenesis, leading to improvement of the cytosolic NAD+/NADH ratio via the malate-citrate shuttle. MCT supplementation could be a promising therapy for citrin deficiency.

A thymine-adenine dinucleotide repeat polymorphism near IL28B is associated with spontaneous clearance of hepatitis C virus.

BACKGROUND: Genome-wide association studies have revealed several single-nucleotide polymorphisms around interleukin 28B (IL28B) that are strongly associated with hepatitis C virus (HCV) clearance. However, their predictive value is not perfect, which suggests that other genetic factors may also be involved in HCV clearance. We previously reported a wide variation in the length of a thymine-adenine (TA) dinucleotide repeat in the promoter region of IL28B and that the transcriptional activity of the promoter increased gradually in a TA repeat length-dependent manner. METHODS: We determined the length of the TA repeats of 1,060 Japanese and 201 African-American samples to investigate the relation to spontaneous HCV clearance. RESULTS: The distribution of the TA repeats greatly differed between the two ethnicities. The variation ranged from 10 to 18 repeats, and the most frequent allele, 12, accounted for over 80% for Japanese. The African-American data showed a gently sloping distribution, and the allele with six repeats was detected only in the African-American sample. The TA repeats 11 or greater were correlated with spontaneous clearance. Multiple logistic regression analysis extracted the genotype of the TA repeats as an independent factor in both the Japanese [p = 0.0004, odds ratio (OR) = 13.02 95% confidence interval (CI) = 2.59-237.0] and African-American (p = 0.027, OR = 3.70 95% CI = 1.16-11.8) populations. CONCLUSIONS: A long TA repeat in the promoter region of IL28B was associated with spontaneous HCV clearance. Although its efficacy may be limited in Japanese population because of its allele distribution, this novel genetic factor will be useful for predicting HCV clearance especially for the African Americans.

Genome-wide association study identifies a PSMD3 variant associated with neutropenia in interferon-based therapy for chronic hepatitis C.

Cytopenia during interferon-based (IFN-based) therapy for chronic hepatitis C (CHC) often necessitates reduction of doses of drugs and premature withdrawal from therapy resulting in poor response to treatment. To identify genetic variants associated with IFN-induced neutropenia, we conducted a genome-wide association study (GWAS) in 416 Japanese CHC patients receiving IFN-based therapy. Based on the results, we selected 192 candidate single nucleotide polymorphisms (SNPs) to carry out a replication analysis in an independent set of 404 subjects. The SNP rs2305482, located in the intron region of the PSMD3 gene on chromosome 17, showed a strong association when the results of GWAS and the replication stage were combined (OR = 2.18, P = 3.05 × 10(-7) in the allele frequency model). Logistic regression analysis showed that rs2305482 CC and neutrophil count at baseline were independent predictive factors for IFN-induced neutropenia (OR = 2.497, P = 0.0072 and OR = 0.998, P < 0.0001, respectively). Furthermore, rs2305482 genotype was associated with the doses of pegylated interferon (PEG-IFN) that could be tolerated in hepatitis C virus genotype 1-infected patients treated with PEG-IFN plus ribavirin, but not with treatment efficacy. Our results suggest that genetic testing for this variant might be useful for establishing personalized drug dosing in order to minimize drug-induced adverse events.

Epiregulin promotes the emergence and proliferation of adult liver progenitor cells.

We have previously reported that epiregulin is a growth factor that seems to act on liver progenitor cells (LPCs) during liver regeneration. However, the relationship between epiregulin and LPCs has remained unclear. The aim of the present study was to clarify the role of epiregulin during liver regeneration. The serum levels of epiregulin in patients with acute liver failure were examined. A liver injury model was developed using mice fed a diet containing 0.1% 3.5-diethoxycarbonyl-1.4-dihydrocollidine (DDC) to induce LPCs. We then evaluated the expression of epiregulin and LPCs in these mice. The proliferation of epithelial cell adhesion molecule + LPCs cultured with epiregulin was examined in vitro, and finally epiregulin was overexpressed in mouse liver. In patients with acute liver failure, serum epiregulin levels were elevated significantly. In DDC mice, LPCs emerged around the portal area. Epiregulin was also detected around the portal area during the course of DDC-induced liver injury and was partially coexpressed with Thy1. Serum epiregulin levels in DDC mice were also significantly elevated. Recombinant epiregulin augmented the proliferative capacity of the LPCs in a dose-dependent manner. In mice showing overexpression of epiregulin, the expression of PCNA on hepatocytes was increased significantly. Finally, LPCs emerged around the portal area after epiregulin gene delivery. We concluded that epiregulin promotes the proliferation of LPCs and DNA synthesis by hepatocytes and is upregulated in the serum of patients with liver injury. Furthermore, induction of epiregulin leads to the appearance of LPCs. Epiregulin would be a useful biomarker of liver regeneration.

Clinical manifestations of liver injury in patients with anorexia nervosa.

AIM: The number of Japanese patients with anorexia nervosa (AN) is increasing as society changes. Mild liver injury is a complication of AN in around 30% of cases. In some rare instances, patients present with severe liver injury similar to acute liver failure. However, there are numerous uncertainties over the clinical characteristics of this condition. The objective of the present study was to clarify the clinical characteristics of AN complicated by liver injury and to investigate the factors related to hepatic complications. METHODS: Thirty-seven patients hospitalized at our institution with a diagnosis of AN were enrolled as the study subjects. The study used clinical data obtained at the time of hospitalization. The enrolled patients underwent subgroup analysis and were categorized into three groups: (i) normal alanine aminotransferase (ALT), (ii) moderately elevated ALT, and (iii) highly elevated ALT. RESULTS: All of the study subjects were female with a median age of 24 years and presenting with marked weight loss (mean body mass index, 13 kg/m(2) ). Thirteen of the subjects had liver injury. We found that patients in the highly elevated ALT group had a significantly high blood urea nitrogen (BUN)/creatinine ratio, and a low blood sugar level. CONCLUSIONS: Our present findings indicate that AN patients with highly elevated ALT have a severe dehydration. This suggests that dysfunction of hepatic circulation accompanying severe dehydration due to malnutrition may be an important factor in the development of liver injury in AN patients.

Possible autoimmune hepatitis induced after chronic active Epstein-Barr virus infection.

Chronic active Epstein-Barr virus infection (CAEBV) can be manifested in a variety of systemic conditions, including interstitial pneumonia, malignant lymphoma, and coronary aneurysm. Sometimes it may be associated with hepatic failure, although the mechanism underlying CAEBV-related hepatotoxicity remains unclear. We encountered a case of autoimmune hepatitis (AIH) associated with CAEBV. A 61-year-old male was referred to our hospital because of abnormal liver enzyme levels after initial diagnosis of CAEBV had been made by laboratory tests and liver biopsy. On admission, positivity for anti-nuclear antibody was evident, and examination of the liver biopsy specimen showed findings compatible with AIH. Steroid administration was initiated, and the liver function parameters subsequently improved. Although phenotypic changes in liver biopsy specimens are rare in this condition, the present case could provide clues to the possible pathogenesis of AIH.

Medium-chain triglyceride supplementation under a low-carbohydrate formula is a promising therapy for adult-onset type II citrullinemia.

BACKGROUND: Citrin, encoded by SLC25A13, is a component of the malate-aspartate shuttle, which is the main NADH-transporting system in the liver. Citrin deficiency causes neonatal intrahepatic cholestasis (NICCD), which usually resolves within the first year of life. However, small numbers of adults with citrin deficiency develop hyperammonemic encephalopathy, adult-onset type II citrullinemia (CTLN2), which leads to death due to cerebral edema. Liver transplantation is the only definitive therapy for patients with CTLN2. We previously reported that a lactose (galactose)-restricted and medium-chain triglyceride (MCT)-supplemented formula is notably effective for patients with NICCD. Citrin deficiency may impair the glycolysis in hepatocytes because of an increase in the cytosolic NADH/NAD+ ratio, leading to an energy shortage. MCT administration can provide energy to hepatocytes and was expected to have a good effect on CTLN2. METHODS: An MCT supplementation therapy under a low-carbohydrate formula was administered to five patients with CTLN2. Four of the patients had episodes of hyperammonemic encephalopathy, and one patient had postprandial hyperammonemia with no symptoms. RESULTS: One of the patients displaying hyperammonemic encephalopathy completely recovered with all normal laboratory findings. Others notably improved in terms of clinical and or laboratory findings with no hyperammonemic symptoms; however, the patients displayed persistent mild citrullinemia and occasionally had postprandial mild hyperammonemia most likely due to an irreversible change in the liver. CONCLUSIONS: An MCT supplement can provide energy to hepatocytes and promote hepatic lipogenesis, leading to a reduction in the cytosolic NADH/NAD+ ratio. MCT supplementation under a low-carbohydrate formula could be a promising therapy for CTLN2 and should also be used to prevent CTLN2 to avoid irreversible liver damage.

A case of adult type 1 Gaucher disease complicated by temporal intestinal hemorrhage.

A 21-year-old man with a history of sudden rectal hemorrhage was referred to our hospital. Examination disclosed thrombocytopenia and hepatosplenomegaly. A liver biopsy specimen demonstrated Gaucher cells in Glisson's capsule. Additional investigations revealed a low level of leukocyte ß-glucosidase activity and common mutations of the glucocerebrosidase gene, L444P/D409H. We diagnosed the patient with Gaucher disease type 1. He underwent enzyme replacement therapy. Thrombocytopenia and hepatosplenomegaly improved at a rate of approximately 50 and 20%, respectively, within 6 months. This case suggests that we must pay attention to adult Gaucher disease as a differential diagnosis for cryptogenic thrombocytopenia.

Dynamics of serum metabolites in patients with chronic hepatitis C receiving pegylated interferon plus ribavirin: a metabolomics analysis.

OBJECTIVES: Serum samples from patients with chronic hepatitis C were subjected to metabolomics analysis to clarify the pretreatment characteristics of their metabolites and also changes in specific metabolites resulting from antiviral therapy with pegylated interferon plus ribavirin (PegIFN/RBV). MATERIALS/METHODS: The serum levels of low-molecular-weight metabolites in the twenty patients before and 24weeks after completion of PegIFN/RBV therapy were analyzed using capillary electrophoresis and liquid chromatography-mass spectrometry. RESULTS: Ten patients showed a non-virological response (NVR) and 10 achieved a sustained virological response (SVR) with eradication of viremia. The pretreatment levels of tryptophan were significantly higher in the patients of SVR than in those of NVR (p=0.010). The area under the curve (AUC) value of tryptophan calculated from the receiver operating characteristic (ROC) curve for discriminating SVR from NVR was 0.84 (95% confidential interval, 0.66-1.02, p=0.010). The ROC curve of multiple logistic regression model incorporating the pretreatment levels of tryptophan and γ-glutamate-arginine showed that the AUC value was highly significant (AUC=0.92, 95% confidential interval, 0.79-1.05, p=0.002). Twenty four weeks after completion of treatment, the levels of γ-glutamyl dipeptides, glutamic acid, 5-oxoproline, glucosamine and methionine sulfoxide were decreased, whereas those of 5-methoxy-3-indoleacetate, glutamine, kynurenine and lysine were increased significantly (p<0.05) in both the NVR and SVR patients. CONCLUSIONS: The pretreatment serum levels of certain metabolites including tryptophan are associated with the response to PegIFN/RBV therapy. PegIFN/RBV therapy can ameliorate the oxidative stress responsible for glutathione metabolism.

Serum prolactin levels and prolactin mRNA expression in peripheral blood mononuclear cells in hepatitis C virus infection.

Prolactin is not only a pituitary hormone but an immunoregulatory hormone secreted from lymphocytes. Prolactin induction in relation to hepatitis C virus (HCV) infection has not been elucidated. The serum levels of prolactin were examined in 232 HCV-infected subjects positive for anti-HCV antibody and 65 healthy controls negative for it, who were recruited in the cohort study. The prolactin mRNAs were measured in peripheral blood mononuclear cells (PBMCs) of eleven healthy volunteers including five men and six women before and after stimulation by HCV in vitro. The serum level of prolactin and prolactin mRNA in PBMCs were measured by chemiluminescence immunoassay and real-time PCR, respectively. The serum levels of prolactin were significantly higher in the HCV-infected subjects (median: 7.5, IQR: 5.7-10.9 ng/ml) than in the controls (median: 5.6, IQR: 4.4-8.3 ng/ml) (P < 0.01). They were significantly higher in HCV-infected males (median: 8.0, IQR: 5.9-11.8 ng/ml) than in the controls (median: 4.8, IQR: 4.2-5.9 ng/ml) (P < 0.001), however, the difference was not significant between HCV-infected females (median: 7.3, IQR: 5.6-10.5 ng/ml) and the controls (median: 6.4, IQR: 5.3-9.8 ng/ml). The mRNA expression of prolactin was induced in PBMCs of all males, but it was induced in PBMCs of the two of six females examined in vitro. These results suggest that the serum level of prolactin is higher in HCV-infected males than in healthy males, and that HCV infection induces the mRNA expression of prolactin in PBMCs that is more apparent in male than in females.

Impaired mitochondrial ß-oxidation in patients with chronic hepatitis C: relation with viral load and insulin resistance.

BACKGROUND: Hepatic steatosis is often seen in patients with chronic hepatitis C (CH-C). It is still unclear whether these patients have an impaired mitochondrial ß-oxidation. In this study we assessed mitochondrial ß-oxidation in CH-C patients by investigating ketogenesis during fasting. METHODS: This study consisted of thirty patients with CH-C. Serum levels of insulin and hepatitis C virus (HCV) core protein were measured by chemiluminescence enzyme immunoassay. The subjects were then fasted, and venous blood samples were drawn 12 h and 15 h after the start of fasting. The levels of blood ketone bodies were measured by an enzymatic cycling method. The rate of change in total ketone body concentration was compared with that in eight healthy volunteers. RESULTS: The rate of change in total ketone body concentration between 12 h and 15 h after the start of fasting was significantly lower in CH-C patients than in healthy volunteers (129.9% (8.5-577.3%) vs. 321.6% (139.6-405.4%); P <0.01). The rate of change in total ketone body concentration in patients with a serum level of HCV core protein of 10000 fmol/L or higher was significantly lower than in patients with a level of less than 10000 fmol/L (54.8% (8.5-304.3%) vs. 153.6% (17.1-577.3%); P <0.05). The rate of change in total ketone body concentration in patients with a homeostasis model assessment of insulin resistance (HOMA-IR) of 2.5 or higher was significantly lower than in patients with a HOMA-IR of less than 2.5 (56.7% (8.5-186.7%) vs. 156.4% (33.3-577.3%); P <0.01). CONCLUSIONS: These results suggest that mitochondrial ß-oxidation is impaired, possibly due to HCV infection in patients with CH-C.

An elderly Japanese patient with adult-onset type II citrullinemia with a novel D493G mutation in the SLC25A13 gene.

Mutations in the SLC25A13 gene lead to neonatal intrahepatic cholestasis caused by citrin deficiency and/or adult-onset type II citrullinemia (CTLN2). A 62-year-old man presented with recurrent episodes of neuropsychiatric manifestations. On admission, he had disorientation and flapping tremor. Laboratory data showed hyperferritinemia in addition to postprandial hyperammonemia and citrullinemia. A liver biopsy specimen revealed moderate hemosiderin deposits and hepatocytes with macrovesicular fat droplets. Genetic analysis of the SLC25A13 gene identified the previously reported p.S225X mutation and a novel p.D493G mutation. Hyperferritinemia might also be a characteristic finding of CTLN2-related fatty changes of the liver.

A point mutation at Asn-534 that disrupts a conserved N-glycosylation motif of the E2 glycoprotein of hepatitis C virus markedly enhances the sensitivity to antibody neutralization.

The molecular basis of antibody neutralization against hepatitis C virus (HCV) is poorly understood. The E2 glycoprotein of HCV is critically involved in viral infectivity through specific binding to the principal virus receptor component CD81, and is targeted by anti-HCV neutralizing antibodies. A previous study showed that a mutation at position 534 (N534H) within the sixth N-glycosylation motif of E2 of the J6/JFH1 strain of HCV genotype 2a (HCV-2a) was responsible for more efficient access of E2 to CD81 so that the mutant virus could infect the target cells more efficiently. The purpose of this study was to analyze the sensitivity of the parental J6/JFH1, its cell culture-adapted variant P-47 possessing 10 amino acid mutations and recombinant viruses with the adaptive mutations to neutralization by anti-HCV antibodies in sera of HCV-infected patients. The J6/JFH1 virus was neutralized by antibodies in sera of patients infected with HCV-2a and -1b, with mean 50% neutralization titers being 1:670 and 1:200, respectively (P < 0.00001). On the other hand, the P-47 variant showed 50- to 200-times higher sensitivity to antibody neutralization than the parental J6/JFH1 without genotype specificity. The N534H mutation, and another one at position 416 (T416A) near the first N-glycosylation motif to a lesser extent, were shown to be responsible for the enhanced sensitivity to antibody neutralization. The present results suggest that the residues 534, and 416 to a lesser extent, of the E2 glycoprotein are critically involved in the HCV infectivity and antibody neutralization.

New neutralizing antibody epitopes in hepatitis C virus envelope glycoproteins are revealed by dissecting peptide recognition profiles.

One of the greatest challenges to HCV vaccine development is the induction of effective immune responses using recombinant proteins or vectors. In order to better understand which vaccine-induced antibodies contribute to neutralization of HCV the quality of polyclonal anti-E1E2 antibody responses in immunized mice and chimpanzees was assessed at the level of epitope recognition using peptide scanning and neutralization of chimeric 1a/2a, 1b/2a and 2a HCVcc after blocking or affinity elution of specific antibodies. Mice and chimpanzees were immunized with genotype 1a (H77) HCV gpE1E2; all samples contained cross-neutralizing antibody against HCVcc. By functionally dissecting the polyclonal immune responses we identified three new regions important for neutralization within E1 (aa264-318) and E2 (aa448-483 and aa496-515) of the HCV glycoproteins, the third of which (aa496-515) is highly conserved (85-95%) amongst genotypes. Antibodies to aa496-515 were isolated by affinity binding and elution from the serum of a vaccinated chimpanzee and found to specifically neutralize chimeric 1a/2a, 1b/2a and 2a HCVcc. IC50 titres (IgG ng/mL) for the aa496-515 eluate were calculated as 142.1, 239.37 and 487.62 against 1a/2a, 1b/2a and 2a HCVcc, respectively. Further analysis demonstrated that although antibody to this new, conserved neutralization epitope is efficiently induced with recombinant proteins in mice and chimpanzees; it is poorly induced during natural infection in patients and chimpanzees (7 out of 68 samples positive) suggesting the epitope is poorly presented to the immune system in the context of the viral particle. These findings have important implications for the development of HCV vaccines and strategies designed to protect against heterologous viruses. The data also suggest that recombinant or synthetic antigens may be more efficient at inducing neutralizing antibodies to certain epitopes and that screening virally infected patients may not be the best approach for finding new cross-reactive epitopes.