Hepatitis C virus in multiple episodes of acute hepatitis in polytransfused thalassaemic children

Phylogenetic analysis in the clinical risk management of an outbreak of hepatitis C virus infection among transfused thalassaemia patients in Italy

BACKGROUND

Occurrence of hepatitis C virus (HCV) infection is reduced by effective risk management procedures, but patient-to-patient transmission continues to be reported in healthcare settings.

AIM

To report the use of phylogenetic analysis in the clinical risk management of an HCV outbreak among 128 thalassaemia outpatients followed at a thalassaemia centre of an Italian hospital.

METHODS

Epidemiological investigation and root-cause analysis were performed. All patients with acute hepatitis and known chronic infection were tested for HCV RNA, HCV genotyping, and NS3, NS5A, and NS5B HCV genomic region sequencing. To identify transmission clusters, phylogenetic trees were built for each gene employing Bayesian methods.

FINDINGS

All patients with acute hepatitis were infected with HCV genotype 1b. Root-cause analysis, including a lookback procedure, excluded blood donors as the source of HCV transmission. The phylogenetic analysis, conducted on seven patients with acute infection and eight patients with chronic infection, highlighted four transmission clusters including at least one patient with chronic and one patient with acute HCV infection. All patients in the same cluster received a blood transfusion during the same day. Two patients with acute hepatitis spontaneously cleared HCV within four weeks and nine patients received ledipasvir plus sofosbuvir for six weeks, all achieving a sustained virological response.

CONCLUSION

Combined use of root-cause analysis and molecular epidemiology was effective in ascertaining the origin of the HCV outbreak. Antiviral therapy avoided the chronic progression of the infection and further spread in care units and in the family environment.

Beyond Metabolism: Role of the Immune System in Hepatic Toxicity

The liver is primarily thought of as a metabolic organ; however, the liver is also an important mediator of immunological functions. Key perspectives on this emerging topic were presented in a symposium at the 2018 annual meeting of the American College of Toxicology entitled "Beyond metabolism: Role of the immune system in hepatic toxicity." Viral hepatitis is an important disease of the liver for which insufficient preventive vaccines exist. Host immune responses inadequately clear these viruses and often potentiate immunological inflammation that damages the liver. In addition, the liver is a key innate immune organ against bacterial infection. Hepatocytes and immune cells cooperatively control systemic and local bacterial infections. Conversely, bacterial infection can activate multiple types of immune cells and pathways to cause hepatocyte damage and liver injury. Finally, the immune system and specifically cytokines and drugs can interact in idiosyncratic drug-induced liver injury. This rare disease can result in a disease spectrum that ranges from mild to acute liver failure. The immune system plays a role in this disease spectrum.

Hepatitis C and kidney disease: A narrative review

Hepatitis-C (HCV) infection can induce kidney injury, mostly due to formation of immune-complexes and cryoglobulins, and possibly to a direct cytopathic effect. It may cause acute kidney injury (AKI) as a part of systemic vasculitis, and augments the risk of AKI due to other etiologies. It is responsible for mesangiocapillary or membranous glomerulonephritis, and accelerates the progression of chronic kidney disease due to other causes. HCV infection increases cardiovascular and liver-related mortality in patients on regular dialysis. HCV-infected patients are at increased risk of acute post-transplant complications. Long-term graft survival is compromised by recurrent or de novo glomerulonephritis, or chronic transplant glomerulopathy. Patient survival is challenged by increased incidence of diabetes, sepsis, post-transplant lymphoproliferative disease, and liver failure. Effective and safe directly acting antiviral agents (DAAs) are currently available for treatment at different stages of kidney disease. However, the relative shortage of DAAs in countries where HCV is highly endemic imposes a need for treatment-prioritization, for which a scoring system is proposed in this review. It is concluded that the thoughtful use of DAAs, will result in a significant change in the epidemiology and clinical profiles of kidney disease, as well as improvement of dialysis and transplant outcomes, in endemic areas.

"Hep C, where art thou": What are the remaining (fundable) questions in hepatitis C virus research?

Hepatitis C virus (HCV) has dominated the field of hepatology for the past 25 years, and its cure in the majority of treated patients is one of the greatest achievements in all of medicine. However, the latter has led to the belief by some that HCV research should be shelved for other, more pressing areas. The mission for HCV eradication is far from accomplished. As a historical reference, we should consider that disease elimination has required vaccination with all previously controlled infections including smallpox and polio and that simple, effective treatment is not sufficient in most infections to lead to substantial control. Syphilis is the best example, for which a single dose of penicillin (which literally costs pennies and that we have had since 1945) is curative in early stages. Not only have we not eradicated syphilis, rates of infection have increased in many places within the United States in recent years. Most HCV-infected subjects are unaware of their infection, remaining at risk for transmission to others and disease progression, including cirrhosis and hepatocellular carcinoma. In the era of highly effective direct-acting antivirals (DAAs), many questions pertaining to HCV remain, but they are more complex and difficult to answer. Here, I provide my perspective on some of these salient issues: the residual risk for disease progression after sustained virologic response, the optimal approach to current DAA failures, the impact of targeting people who inject drugs with DAAs, vaccine prospects, and application of neutralizing HCV glycoprotein antibodies. (Hepatology 2017;65:341-349).

[Way to the peptide vaccine against hepatitis C]

In order to surpass the problem of genetic variability of hepatitis C virus envelope proteins during vaccine development, we used the so-called "reverse vaccinology"approach--"from genome to vaccine". Database of HCV protein sequences was designed, viral genome analysis was performed, and several highly conserved sites were revealed in HCV envelope proteins in the framework of this approach. These sites demonstrated low antigenic activity in full-size proteins and HCV virions: antibodies against these sites were not found in all hepatitis C patients. However, two sites, which contained a wide set of potential T-helper epitope motifs, were revealed among these highly conserved ones. We constructed and prepared by solid-phase peptide synthesis several artificial peptide constructs composed of two linker-connected highly conserved HCV envelope E2 protein sites; one of these sites contained a set of T-helper epitope motifs. Experiments on laboratory animals demonstrated that the developed peptide constructs manifested immunogenicity compared with one of protein molecules and were able to raise antibodies, which specifically bound HCV envelope proteins. We succeeded in obtaining antibodies reactive with HCV from hepatitis C patient plasma upon the immunization with some constructs. An original preparation of a peptide vaccine against hepatitis C is under development on the basis of these peptide constructs.

Virus-Specific Cellular Response in Hepatitis C Virus Infection

Studies performed on chimpanzees and humans have revealed that strong, multispecific and sustained CD4(+) and CD8(+) T cell immune responses is a major determinant of hepatitis C virus (HCV) clearance. However, spontaneous elimination of the virus occurs in minority of infected individuals and cellular response directed against HCV antigens is not persistent in individuals with chronic infection. This review presents characteristics of the HCV-specific T cell response in patients with different clinical course of infection, including acute and chronic infection, persons who spontaneously eliminated HCV and non-infected subjects exposed to HCV. Detection of HCV-specific response, especially in non-infected subjects exposed to HCV, may be indicative of HCV prevalence in population and rate of spontaneous viral clearance. Understanding the mechanisms and role of HCV-specific cellular immune response would contribute to better understanding of HCV epidemiology, immunopathogenesis and may help to design an effective vaccine.

Ultra-deep sequencing provides insights into the virology of hepatitis C super-infections in a case of three sequential infections with different genotypes

The current epidemic of Hepatitis C infection in HIV-positive men who have sex with men is associated with increasing use of recreational drugs. Multiple HCV infections have been reported in haemophiliacs and intravenous drug users. Using ultra-deep sequencing analysis, we present the case of an HIV-positive MSM with evidence of three sequential HCV infections, each occurring during the acute phase of the preceding infection, following risk exposures. We observed rapid replacement of the original strain by the incoming genotype at subsequent time points. The impact of HCV super-infection remains unclear and UDS may provide new insights.

Mixed HCV infection and reinfection in people who inject drugs--impact on therapy

The majority of new and existing cases of HCV infection in high-income countries occur among people who inject drugs (PWID). Ongoing high-risk behaviours can lead to HCV re-exposure, resulting in mixed HCV infection and reinfection. Assays used to screen for mixed infection vary widely in sensitivity, particularly with respect to their capacity for detecting minor variants (<20% of the viral population). The prevalence of mixed infection among PWID ranges from 14% to 39% when sensitive assays are used. Mixed infection compromises HCV treatment outcomes with interferon-based regimens. HCV reinfection can also occur after successful interferon-based treatment among PWID, but the rate of reinfection is low (0-5 cases per 100 person-years). A revolution in HCV therapeutic development has occurred in the past few years, with the advent of interferon-free, but still genotype-specific regiments based on direct acting antiviral agents. However, little is known about whether mixed infection and reinfection has an effect on HCV treatment outcomes in the setting of new direct-acting antiviral agents. This Review characterizes the epidemiology and natural history of mixed infection and reinfection among PWID, methodologies for detection, the potential implications for HCV treatment and considerations for the design of future studies.

Molecular epidemiology of different hepatitis C genotypes in serum and peripheral blood mononuclear cells in jahrom city of iran

BACKGROUND

The Hepatitis C Virus (HCV) is considered essentially hepatotropic, yet the virus compartments have also been found in important extra hepatic sites. Detection of HCV RNA in extra hepatic reservoirs such as peripheral blood mononuclear cells (PBMCs) is important for determining disease progression and treatment effectiveness.

OBJECTIVES

The present study aimed to determine different HCV genotypes in patients' plasma and PBMC specimens, in Jahrom city of Iran.

PATIENTS AND METHODS

Blood samples of 137 patients with established HCV were collected at the Honari clinic. These patients were anti-HCV and plasma HCV RNA positive. After plasma RNA extraction and obtaining a pellet of approximately 3-5 × 10(6) PBMCs, Real-time PCR was performed, using specific-genotype primers. Finally, data analysis was done by the Statistical Package for Social Sciences (SPSS) software.

RESULTS

Subtype 3 was the most common genotype in plasma (57.7%) and PBMCs (51.1%). Subtype 1a was detected in 36.5% and 30.7% of plasma samples and PBMCs, respectively whereas subtype 4 was not detected in any of the cases. There was a genotype difference between plasma and PBMCs of 12.4% of patients. In four patients no genotype was detected in their plasma but genotype 3 was detected in the PBMCs.

CONCLUSIONS

It is suggested that determination of the target genotype by plasma subtyping for choosing the proper antiviral therapy is essential but may result in therapy failure. HCV genotyping in PBMC samples, along with plasma specimens, might be more beneficial. Therefore determining the HCV genotype in PBMCs, before beginning the therapy is useful due to the possibility of occult infection detection.

An insight into the diagnosis and pathogenesis of hepatitis C virus infection

This review focuses on research findings in the area of diagnosis and pathogenesis of hepatitis C virus (HCV) infection over the last few decades. The information based on published literature provides an update on these two aspects of HCV. HCV infection, previously called blood transmitted non-A, non-B infection, is prevalent globally and poses a serious public health problem worldwide. The diagnosis of HCV infection has evolved from serodetection of non-specific and low avidity anti-HCV antibodies to detection of viral nucleic acid in serum using the polymerase chain reaction (PCR) technique. Current PCR assays detect viral nucleic acid with high accuracy and the exact copy number of viral particles. Moreover, multiplex assays using real-time PCR are available for identification of HCV-genotypes and their isotypes. In contrast to previous methods, the newly developed assays are not only fast and economic, but also resolve the problem of the window period as well as differentiate present from past infection. HCV is a non-cytopathic virus, thus, its pathogenesis is regulated by host immunity and metabolic changes including oxidative stress, insulin resistance and hepatic steatosis. Both innate and adaptive immunity play an important role in HCV pathogenesis. Cytotoxic lymphocytes demonstrate crucial activity during viral eradication or viral persistence and are influenced by viral proteins, HCV-quasispecies and several metabolic factors regulating liver metabolism. HCV pathogenesis is a very complex phenomenon and requires further study to determine the other factors involved.

Emerging concepts in immunity to hepatitis C virus infection

Since the discovery of hepatitis C virus (HCV) by molecular cloning almost a quarter of a century ago, unprecedented at the time because the virus had never been grown in cell culture or detected serologically, there have been impressive strides in many facets of our understanding of the natural history of the disease, the viral life cycle, the pathogenesis, and antiviral therapy. It is apparent that the virus has developed multiple strategies to evade immune surveillance and eradication. This Review covers what we currently understand of the temporal and spatial immunological changes within the human innate and adaptive host immune responses that ultimately determine the outcomes of HCV infection.

Natural history of hepatitis C in thalassemia major: a long-term prospective study

BACKGROUND

Transfusion-acquired hepatitis C virus (HCV) remains an important problem among patients with thalassemia. In this study, we evaluated the natural history of post-transfusional hepatitis C in thalassemia major, paying special attention to spontaneous viral clearance, to factors influencing the chronicity rate and fibrosis progression.

DESIGN AND METHODS

A prospective study to evaluate the incidence and etiology of transfusion-related hepatitis was started in 1980. In patients who developed hepatitis C, HCV RNA, ALT, and ferritin were measured over time. The correlation between interleukin-28B gene polymorphisms and viral clearance was also analyzed.

RESULTS

Seventy-three of 135 patients (62.2%) acquired HCV. An extended follow-up (22 to 30 yr) with HCV RNA assessment was available in 52 patients. Of them, 23 (44.2%) cleared the virus. The proportion of IL-28B genotypes was different between the subjects who cleared the virus and the subjects who did not. Fibrosis progression was similar in HCV RNA-positive and HCV RNA-negative patients. Liver iron was the only factor associated with the fibrosis.

CONCLUSIONS

In thalassemia patients with HCV infection, liver iron does not play a major role in influencing the chronicity rate, whereas it is significantly associated with the fibrosis.

Frequent longitudinal sampling of hepatitis C virus infection in injection drug users reveals intermittently detectable viremia and reinfection

BACKGROUND

Detection of hepatitis C virus (HCV) reinfection and intercalation (ie, intermittent recurrent bouts of viremia with homologous virus interspersed with aviremic periods) requires extensive and frequent evaluation and viral sequencing.

METHODS

HCV infection outcomes were studied prospectively in active injection drug users with recurrent HCV RNA-positive tests after serial negative results. HCV viremia and viral sequences (Core/E1) were assessed from monthly blood samples.

RESULTS

Viral clearance, reinfection, and intercalating infection were all detected. Among 44 participants with apparently resolved HCV (26 incident HCV clearers and 18 enrolled with already resolved infection), 36 (82%) remained persistently HCV RNA negative, but 8 demonstrated intermittent recurrent viremia. Four of these (50%) had confirmed reinfection with a heterologous virus; 3 demonstrated viral intercalation, and 1 was not classifiable as either. Estimated incidence of first reinfection was 5.4 per 100 person-years (95% confidence interval, 2.0-14.5). Six (75%) participants, including 3 of 4 with reinfection, demonstrated sustained viral clearance for a median of 26 months since last HCV RNA test.

CONCLUSIONS

These results show that frequent monitoring and viral sequencing are required to correctly assess HCV outcomes and estimate incidence of reinfection (which was previously overestimated). Sustained clearance may take many months and occur after episodes of reinfection and viral intercalation. Three of 4 subjects who had confirmed reinfection showed evidence of long-term clearance. Viral intercalation occurs with significant frequency. Further studies of these events, especially immunological, are needed to inform HCV clinical care and vaccine development.

Hepatitis C virus infection in the immunocompromised host: a complex scenario with variable clinical impact

The relationship between Hepatitis C Virus (HCV) infection and immunosuppression is complex and multifaceted. Although HCV-related hepatocytolysis is classically interpreted as secondary to the attack by cytotoxic T lymphocytes against infected cells, the liver disease is usually exacerbated and more rapidly evolutive in immunosuppressed patients. This generally occurs during the immunosuppression state, and not at the reconstitution of the host response after immunosuppressive therapy discontinuation. The field of immunosuppression and HCV infection is complicated both by the different outcome observed in different situations and/or by contrasting data obtained in the same conditions, with several still unanswered questions, such as the opportunity to modify treatment schedules in the setting of post-transplant follow-up. The complexity of this field is further complicated by the intrinsic tendency of HCV infection in itself to lead to disorders of the immune system. This review will briefly outline the current knowledge about the pathogenesis of both hepatic and extrahepatic HCV-related disorders and the principal available data concerning HCV infection in a condition of impairment of the immune system. Attention will be especially focused on some conditions - liver or kidney transplantation, the use of biologic drugs and cancer chemotherapy - for which more abundant and interesting data exist.

Challenges for HCV vaccine development in HIV-HCV coinfection

It is estimated that 4-5 million HIV-infected patients are coinfected with HCV. The impact of HIV on the natural course of HCV infection is deleterious. This includes a higher rate of HCV persistence and a faster rate of fibrosis progression. Coinfected patients show poor treatment outcome following standard HCV therapy. Although direct antiviral agents offer new therapeutic options, their use is hindered by potential drug interactions and toxicity in HIV-infected patients under HAART. Overtime, a large reservoir of HCV genotype 1 patients will accumulate in resource poor countries where the hepatitis C treatment is not easily affordable and HIV therapy remains the primary health issue for coinfected individuals. HCV vaccines represent a promising strategy as an adjunct or alternative to current HCV therapy. Here, the authors review the pathogenesis of hepatitis C in HIV-infected patients, with a focus on the impact of HIV on HCV-specific immune responses and discuss the challenges for vaccine development in HIV-HCV coinfection.

Hepatitis C virus clearance, reinfection, and persistence, with insights from studies of injecting drug users: towards a vaccine

Hepatitis C virus (HCV) was discovered more than two decades ago, but progress towards a vaccine has been slow. HCV infection will spontaneously clear in about 25% of people. Studies of spontaneous HCV clearance in chimpanzees and human beings have identified host and viral factors that could be important in the control of HCV infection and the design of HCV vaccines. Although data from studies of chimpanzees suggest that protection against reinfection is possible after spontaneous clearance, HCV is a human disease. Results from studies of reinfection risk after spontaneous clearance in injecting drug users are conflicting, but some people seem to have protection against HCV persistence. To guide future vaccine development, we assess data from studies of HCV reinfection after spontaneous clearance, discuss flaws in the methods of previous human studies, and suggest essential components for future investigations of control of HCV infection.

Both innate and adaptive immunity mediate protective immunity against hepatitis C virus infection in chimpanzees

Understanding the immunological correlates associated with protective immunity following hepatitis C virus (HCV) reexposure is a prerequisite for the design of effective HCV vaccines and immunotherapeutics. In this study we performed a comprehensive analysis of innate and adaptive immunity following HCV reexposure of two chimpanzees that had previously recovered from HCV-JFH1 infection. One of the chimpanzees, CH10274, became protected from active viremia by repeated challenges with homologous HCV-JFH1 and developed neutralizing antibodies, but was later infected with high-level viremia by a heterologous challenge with the HCV H77 virus that persisted for more than 1 year. The other chimpanzee, CH10273, was protected from a similar, heterologous H77 challenge without any evidence of neutralizing antibodies. Peripheral HCV-specific T-cell responses were present in both chimpanzees after challenges and, interestingly, the overall magnitude of response was lower in uninfected CH10273, which, however, exhibited a more robust CD8+ T-cell response. CH10273 showed higher hepatic expression of CD8 and CD56 (natural killer) markers than CH10274 did shortly after inoculation with H77. The heightened T-cell response was associated with an enhanced hepatic production of interferons (both type I and II) and interferon-stimulated genes (ISGs) in CH10273. Therefore, protection or clearance of HCV reinfection upon heterologous rechallenge depends on the activation of both intrahepatic innate and cellular immune responses. Furthermore, our results suggest that serum neutralizing antibodies may contribute to early control of viral replication and spread after homologous HCV rechallenges but may not be sufficient for a long-term protective immunity.

CONCLUSION

Our study shows that protective immunity against HCV reinfection is orchestrated by a complex network of innate and adaptive immune responses.

The hepatitis C virus glycan shield and evasion of the humoral immune response

Despite the induction of effective immune responses, 80% of hepatitis C virus (HCV)-infected individuals progress from acute to chronic hepatitis. In contrast to the cellular immune response, the role of the humoral immune response in HCV clearance is still subject to debate. Indeed, HCV escapes neutralizing antibodies in chronically infected patients and reinfection has been described in human and chimpanzee. Studies of antibody-mediated HCV neutralization have long been hampered by the lack of cell-culture-derived virus and the absence of a small animal model. However, the development of surrogate models and recent progress in HCV propagation in vitro now enable robust neutralization assays to be performed. These advances are beginning to shed some light on the mechanisms of HCV neutralization. This review summarizes the current state of knowledge of the viral targets of anti-HCV-neutralizing antibodies and the mechanisms that enable HCV to evade the humoral immune response. The recent description of the HCV glycan shield that reduces the immunogenicity of envelope proteins and masks conserved neutralizing epitopes at their surface constitutes the major focus of this review.

Evolution of HCV incidence in drug users in France

Over the last 40 years, the dynamics of hepatitis C virus (HCV) infection in drug users has been affected by the illicit drug market, the health environment including the devastating impact of the HIV/AIDS epidemic which erupted in the 1980s, and the diffusion of substitution treatment beginning in 1995. The purpose of this literature review is to present the dynamics of HCV infection in drug users in France over the last 40 years. Two prevalence studies of HCV infection in the general population were conducted by the French Institute for Public Health Surveillance in 1994 and 2004 and were the touchstone data sources for this analysis. Hypotheses constructed from the findings of these two studies were examined in light of results reported by multicentre prevalence and incidence studies in drug-user populations. The incidence of HCV infection in drug users in France reached a peak in the late 1980s or early 1990s after a lengthy period of epidemic expansion. Implementation of a risk reduction policy enabled a very significant reduction in the incidence of HCV infection in drug users over the last 20 years, leading to incidence figures which are now 10–15% of the 1990 estimate.

An Assessment of the Use of Chimpanzees in Hepatitis C Research Past, Present and Future: 2. Alternative Replacement Methods

The use of chimpanzees in hepatitis C virus (HCV) research was examined in the report associated with this paper ( 1: Validity of the Chimpanzee Model), in which it was concluded that claims of past necessity of chimpanzee use were exaggerated, and that claims of current and future indispensability were unjustifiable. Furthermore, given the serious scientific and ethical issues surrounding chimpanzee experimentation, it was proposed that it must now be considered redundant — particularly in light of the demonstrable contribution of alternative methods to past and current scientific progress, and the future promise that these methods hold. This paper builds on this evidence, by examining the development of alternative approaches to the investigation of HCV, and by reviewing examples of how these methods have contributed, and are continuing to contribute substantially, to progress in this field. It augments the argument against chimpanzee use by demonstrating the comprehensive nature of these methods and the valuable data they deliver. The entire life-cycle of HCV can now be investigated in a human (and much more relevant) context, without recourse to chimpanzee use. This also includes the testing of new therapies and vaccines. Consequently, there is no sound argument against the changes in public policy that propose a move away from chimpanzee use in US laboratories.

Distribution of different hepatitis C virus genotypes in patients with hepatitis C virus infection

AIM: To investigate the presence of mixed infection and discrepancy between hepatitis C virus (HCV) genotypes in plasma, peripheral blood mononuclear cells (PBMCs), and liver biopsy specimens.

METHODS: From September 2008 up to April 2009, 133 patients with chronic hepatitis C referred to Firouzgar Hospital for initiation of an antiviral therapy were recruited in the study. Five milliliters of peripheral blood was collected from each patient and liver biopsy was performed in those who gave consent or had indications. HCV genotyping was done using INNO-LiPA™ HCV II in serum, PBMCs, and liver biopsy specimens and then confirmed by sequencing of 5’-UTR fragments.

RESULTS: The mean age of patients was 30.3 ± 17.1 years. Multiple transfusion was seen in 124 (93.2%) of patients. Multiple HCV genotypes were found in 3 (2.3%) of 133 plasma samples, 9 (6.8%) of 133 PBMC samples, and 8 (18.2%) of 44 liver biopsy specimens. It is notable that the different genotypes found in PBMCs were not the same as those found in plasma and liver biopsy specimens.

CONCLUSION: Our study shows that a significant proportion of patients with chronic hepatitis C are affected by multiple HCV genotypes which may not be detectable only in serum of patients.

Hepatic disorders in chronic kidney disease

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infection are the most common and serious causes of liver damage in patients with chronic kidney disease (CKD). The natural histories of HBV and HCV infections in patients with CKD are not fully understood; however, recent evidence has emphasized the adverse effect of HBV and/or HCV infection on survival in this population. Chronic liver disease is the fourth most important cause of death after renal transplantation. The negative effect of HCV infection on survival among renal transplant recipients has been linked to liver dysfunction and extrahepatic complications, such as chronic glomerulonephritis, post-transplantation diabetes mellitus, chronic allograft nephropathy, and sepsis. The transmission of HCV by solid organ transplantation has been unequivocally demonstrated. Renal transplant recipients who receive kidneys from HCV-positive donors are at increased risk of death. Although several studies have shown that in patients with HCV infection and chronic renal failure renal transplantation is associated with better survival than is dialysis, recent clinical guidelines recommend that kidneys from HCV-infected donors should not be used in HCV-seropositive recipients without detectable HCV viremia. Monotherapy with conventional interferon has been suggested to be a useful treatment for hepatitis C infection in patients on dialysis. Although no evidence suggests that patients with CKD are more prone to suffer from hepatic toxic effects than individuals with normal kidney function, patients with CKD usually receive multiple medications; and drug interactions may, therefore, have a role in the pathogenesis of drug-induced liver disease in this population.

Characterization of the cellular immune response in hepatitis C virus infection

Hepatitis C virus (HCV), a hepatotropic RNA virus, is a major causative agent of chronic hepatitis, liver cirrhosis, and hepatocellular carcinomas. The host immune responses, especially cellular immune responses, play an important role in viral clearance, liver injury, and persistent HCV infection. A thorough characterization of the HCV cellular immune responses is important for understanding the interplays between host immune system and viral components, as well as for developing effective therapeutic and prophylactic HCV vaccines. Recent advances that provide better understanding the cell immune responses in HCV infection are summarized in this article.

HCV-related hepatocellular carcinoma: From chronic inflammation to cancer

Hepatitis C virus (HCV) infection is a worldwide health problem because of its incidence and pathogenicity. It might evolve into chronic disease, cirrhosis, and/or hepatocellular carcinoma (HCC) and the outcome is mainly determined by the host immune response. For viral clearance, combined innate and adaptive immune responses are required; resolution requires a vigorous, durable, polyclonal CD4(+) and CD8(+) T-cell response, with an increase in virus-specific CD8(+) T cells or cytotoxic T lymphocytes. Failure of efficient immune response can lead to chronic inflammation, tissue remodeling through cell growth, apoptosis and/or necrosis and induction of oxidative stress. Development of fibrosis and/or cirrhosis plus a microenvironment conducive to genomic instability mutations will promote neoplastic transformation. System governance derives from cellular (regulatory cells) and humoral (cytokines and chemokines) immune networks. Therefore, HCC pathogenesis may be a model to study the disease progression from chronic inflammation to cancer allowing design of new strategies targeting the immune response, thereby modifying disease outcome.

The long and winding road leading to the identification of the hepatitis C virus

This review describes work conducted largely in my laboratory at the Chiron Corporation between 1982 and 1989 that led to the identification of the hepatitis C virus (HCV). Key colleagues included Dr. Qui-Lim Choo in my laboratory and Dr. George Kuo also of Chiron as well as my collaborator Dr. Daniel Bradley at the CDC who provided many biological samples from the NANBH chimpanzee model. Numerous molecular approaches were explored including the screening of tens of millions of bacterial cDNA clones derived from these materials. While this early genomics approach resulted in the identification of many host gene activities associated with NANBH, no genes of proven infectious etiology could be identified. A separate avenue of our research led to the molecular characterization of the complete hepatitis delta viral genome but unfortunately, this could not be used as a molecular handle for HCV. Largely following input from Dr. Kuo, I initiated a blind cDNA immunoscreening approach involving the large-scale screening of bacterial proteomic cDNA libraries derived from NANBH-infectious chimpanzee materials (prior to the development of PCR technology) using sera from NANBH patients as a presumptive source of viral antibodies. Eventually, this novel approach to identifying agents of infectious etiology led to the isolation of a single small cDNA clone that was proven to be derived from the HCV genome using various molecular and serological criteria. This discovery has facilitated the development of effective diagnostics, blood screening tests and the elucidation of promising drug and vaccine targets to control this global pathogen.

Current status of renal transplantation from HCV-positive donors

Hepatitis C virus (HCV) infection remains frequent among renal transplant (RT) recipients and has a detrimental effect on patient and graft survival. accelerated progression of liver disease due to HCV has been implicated in increased mortality after kidney transplantation but additional outcomes have been related to HCV after RT. all HCV-infected kidney transplant candidates should be considered for liver biopsy before RT. HCV infection should not be considered an absolute contraindication to renal transplantation, although the course of HCV-related liver disease is often progressive. Numerous organ procurement organizations have introduced the policy of accepting kidneys from HCV-positive donors for HCV-positive recipients, but this is still controversial. Single-center experiences have not reported adverse effects on the short-term patient and graft survival, however information from large databases has suggested that RT recipients of HCV-positive donors are independently at risk of mortality even in the modern era of immunosuppression. Renal transplantation should be considered using HCV-seropositive grafts for qualified patients with chronic kidney disease (CKD) stage 5 and HCV infection since good information indicates that the transplantation of kidneys from HCV-infected donors results in improved survival compared to wait-listed and dialysis-dependent candidates. a potential risk related to the use of donor HCV-positive kidneys cannot be excluded, and kidneys from HCV-infected donors should be restricted to recipients with evidence of active viremia at the time of kidney transplantation.

Virological and epitope evolution of HCV infection from acute hepatitis C to subsequent episodes of HCV-related acute liver cell necrosis

AIM

To evaluate the virological and clinical events occurring during a 3-year follow-up in three patients who, after symptomatic acute hepatitis C (AHC), experienced subsequent episodes of HC virus (V)-related acute liver cell necrosis.

PATIENTS AND METHODS

The three patients were investigated for viral variability in the core, E1/E2, and NS5b regions during different phases of infection, and a computer-assisted analysis of the variation of known predicted epitopes in the consensus sequence was performed.

RESULTS

The first patient showed numerous genetic variations, which may be related to the maintenance of a chronic HCV infection state and to episodes of liver disease exacerbation. The second patient showed minimal viral variations associated with apparent resolution of the infection, but the same virus isolate, based on phylogenetic analysis, produced a second acute episode after the occult phase. The third patient, after the resolution of AHC, manifested a second episode of HCV infection by a different HCV sub-genotype.

CONCLUSION

Episodes of HCV-related acute liver cell necrosis after AHC may be associated to different virological patterns, such as the establishment of a chronic HCV infection, a reactivation of an occult virus, or a reinfection by a different HCV genotype.

Treatment of chronic hepatitis C in sickle cell disease and thalassaemic patients with interferon and ribavirin

BACKGROUND/AIM

Hepatic complications are a major cause of death in patients with congenital anaemia and chronic hepatitis C. Ribavirin is usually contraindicated in patients with haemolytic anaemia. This pilot study evaluated the efficacy and safety of antiviral treatment in patients with sickle cell disease (SCD) or beta-thalassaemia major (TM).

METHODS

Eleven consecutive SCD and TM patients were included. Interferon monotherapy was administrated in the two first thalassaemic patients. Other patients received combination therapy with full dose of pegylated interferon 2b and increasing doses of ribavirin, starting with a low dose of ribavirin (400 mg/day).

RESULTS

Hepatitis C virus genotypes were 1 or 4 in nine cases. A sustained virological response achieved in five of 11 patients despite unfavourable factors to response (genotypes, nonresponders to an earlier treatment). Haemoglobin level at the end of treatment was higher than baseline levels in five of six SCD patients. No SCD patient needed a transfusion during and after treatment period, neither presented vasoocclusive crisis. The mean increase in transfusion requirements was 32.5% in the thalassaemic group.

CONCLUSION

A sustained virological response can be obtained in SCD and TM patients. No earlier study of excellent haematological tolerance among SCD patients under ribavirin has been reported to date. The results of this study suggest that full dose ribavirin could be used from the start of treatment in SCD patients.

Hepatitis C virus (HCV): a review of immunological aspects

The present manuscript represents an updated review on different aspects of immunology involved during hepatitis C virus infection in human beings. This includes a brief mention of HCV structure, presentation of viral components to host immune system, and ensuing immune response and immunopathogenesis occurring during HCV infection. The present article also highlights immunodiagnosis of HCV infection and the current status of immunotherapy available for HCV eradication. Its envelope protein, E2, is the primary mediator of virus attachment and cell entry. CD81 molecule on cell surface acts as a major receptor for viral entry into the host cells. Mature dendritic cells play an important role in presenting viral antigen, activate T-cells, and initiate anti-viral immune response. Relative T-cell populations and release of different cytokines from activated T-cells ultimately determine the clearance or persistence of HCV viremia through cellular and humoral immune responses. Natural killer (NK) cells constitute the first line of host defense against invading viruses by recruiting virus-specific T-cells and inducing antiviral immunity in liver. Diagnosis of acute or chronic hepatitis C virus (HCV) infection is established by serological assays for presence of antibodies against different sets of viral proteins during varied periods post infection. An effective immunotherapy and vaccine against HCV is still awaited.

Retracted: Genetic diversity in hepatitis C virus (HCV): A brief review

The following article from Reviews in Medical Virology, Genetic diversity in hepatitis C virus (HCV) a brief review, by M Irshad, published online on December 16 2008 in Wiley InterScience (www.interscience.wiley.com) has been retracted by agreement between the author, the journal Editor in Chief, P.D. Griffiths, and the publisher Wiley Blackwell. The retraction has been agreed due to overlap with the following article by P Simmonds, Genetic diversity and evolution of hepatitis C virus fifteen years on, published in Journal of General Virology, 2004, 85, 3173-3178.

Immunotherapy for HCV infection: next steps

With more than 170 million individuals currently infected, HCV is a global pandemic, effecting approximately 3% of the entire world's population. HCV infection is a growing infectious disease pandemic with approximately 3-4 million new cases reported each year. Due to the persistent nature of the virus, 70-90% of infected individuals will develop chronic infection, which can lead to progressive liver disease including cirrhosis and hepatocellular carcinoma. Current standard treatment with a combination of IFN-alpha and ribavirin has improved the prognosis for many HCV sufferers; however, infection is very difficult to treat successfully and the protocol for treatment is neither simple, well tolerated nor economically favorable. Standard treatment can cost an average of US$22,000, and depending on genotype, as few as 42% of treated individuals will clear the infection. This collection of treatment issues combined with new concepts in immune therapy serve to underscore an urgent need for the development of improved immunotherapies, such as novel interferons, and support the possible development of therapeutic vaccines for the treatment of chronic HCV infection.

Current approaches to HCV infection in current and former injection drug users

Injection drug use (IDU) accounts for 75% of incident cases of hepatitis C virus (HCV) infection in the developed world. Of those infected with HCV, up to 80% will go on to develop chronic disease. Intervention with effective treatment in eligible subjects will limit the impact of the long-term consequences of infection. The use of combination therapy with pegylated interferon and ribavirin may lead to a cure in up to 80% of treated individuals who carry genotype 2 or 3 isolates. Such individuals account for up to 45% of certain cohorts, such as in the inner city of Vancouver. Historically, many IDUs have not received treatment for HCV infection even if it were medically indicated. Recent data (including our own) suggest that, in the right context, response rates similar to those reported in clinical trials of HCV therapy can be achieved in IDUs, even with ongoing drug use. This is all the more important given that prior infection may protect against re-infection even in the presence of ongoing risk behaviors for HCV transmission. The keys to a successful program appear to be appropriate patient selection as well as the delivery of care within an appropriate setting, preferably with a multidisciplinary team in a way that addresses the issue of addiction and other conditions simultaneously. The development of such programs may be quite complex, but the ultimate benefit (for the treated population and for society as a whole) is certainly worth the effort.

Strong HCV NS3- and NS4A-specific cellular immune responses induced in mice and Rhesus macaques by a novel HCV genotype 1a/1b consensus DNA vaccine

Hepatitis C virus (HCV) represents a major health burden with more than 170 million individuals currently infected worldwide, equaling roughly 3% of the world's population. HCV preferentially infects hepatocytes and is able to persist in up to 70% of infected individuals. It is estimated that up to 30% of chronically infected individuals will go on to develop progressive liver disease as a result of HCV infection, making the virus the leading cause of liver transplantation in the world. Currently there is no vaccine for HCV. In this study, we have taken a multi-step approach to develop a novel genotype 1a/1b consensus HCV NS3/NS4A DNA vaccine able to induce strong cellular immunity. We show that this construct is able to induce strong anti-NS3/NS4A T cell responses in C57BL/6 mice, as well as, in Rhesus macaques. Our data suggest that DNA vaccines encoding HCV proteins NS3/NS4A merit further study in the context of future prophylactic and therapeutic HCV T cell based vaccines.

Immune responses during acute and chronic infection with hepatitis C virus

Hepatitis C virus (HCV) induces persistent infection and causes chronic liver disease in most infected patients. Vigorous HCV-specific CD4+ and CD8+ T cell responses against HCV multiple epitopes are necessary for spontaneous viral clearance during the acute phase, but the virus appears to have multiple strategies to evade these defenses. There are relatively few studies on the role of immune responses during the chronic phase of infection. CD4+ T cell responses appear to protect against liver injury and may be important to clearance during interferon and ribavirin based therapy. Classic cytotoxic T cells (CTL) may primarily damage the liver in chronic HCV, but there may be subpopulations of T cells that protect against liver inflammation. Resolution of these outstanding questions is important to the development of a prophylactic vaccine as well as improving therapeutic options for those with chronic infection.

Critical issues in the treatment of hepatitis C virus infection in methadone maintenance patients

AIMS

Hepatitis C virus (HCV) infection is a common chronic complication of injection drug use. Methadone maintenance programs contain large numbers of patients infected with HCV. This paper reviews HCV infection with emphasis on the medical care of HCV-infected, or HCV and human immunodeficiency virus co-infected, patients on methadone or buprenorphine maintenance.

METHODS

Literature searches using PubMed, PsycINFO and SocINDEX were used to identify papers from 1990-present on antiviral therapy for HCV in methadone maintenance patients and on liver transplantation in methadone maintenance patients.

RESULTS

Injection drug use is the most significant risk factor for HCV infection in most western countries. The prevalence of HCV antibody is high in injection drug users (53-96%) and in patients enrolled in methadone maintenance programs (67-96%). Studies of antiviral therapy for HCV in methadone maintenance patients show rates of sustained virological response (SVR), defined as negative HCV-RNA 24 weeks after the end of treatment, of 28-94%. In studies with contrast groups, no significant differences in SVR between methadone and contrast groups were found. Excellent completion rates of antiviral therapy (72-100%) were found in five of six studies. There are many barriers to methadone maintenance patients' receiving antiviral therapy, and research on overcoming barriers is discussed. Liver transplantation has been successful in methadone maintenance patients but has not been utilized widely.

CONCLUSION

High quality medical care for all aspects of HCV infection can be provided to methadone maintenance patients. The literature supports the effectiveness of such services, but the reality is that most patients do not receive them.

HBeAg and hepatitis B virus DNA as outcome predictors during therapy with peginterferon alfa-2a for HBeAg-positive chronic hepatitis B

The aims of this study were to evaluate the usefulness of quantitative hepatitis B e antigen (HBeAg) values for predicting HBeAg seroconversion in patients treated with peginterferon alfa-2a and to assess the dynamic changes in quantitative HBeAg during therapy, compared with conventional measures of serum hepatitis B virus DNA. Data were analyzed from a large, randomized, multinational phase III registration trial involving 271 HBV-infected HBeAg-positive patients who received peginterferon alfa-2a plus oral placebo for 48 weeks. HBeAg levels were measured serially during therapy using a microparticle enzyme immunoassay validated with in-house reference standards obtained from the Paul Ehrlich Institute (PEIU/mL). In patients who achieved HBeAg seroconversion, levels of HBeAg consistently decreased during treatment and remained at their lowest level during the 24 weeks of posttreatment follow-up. After 24 weeks of treatment, 4% of patients with the highest levels of HBeAg (>or=100 PEIU/mL) achieved HBeAg seroconversion, yielding a negative predictive value of 96%, which was greater than that obtained for levels of HBV DNA (86%). Late responders to peginterferon alfa-2a could also be differentiated from nonresponders by continued decrease in HBeAg values, which were not evident by changes in HBV DNA.

CONCLUSION

These analyses suggest quantitative HBeAg is a useful adjunctive measurement for predicting HBeAg seroconversion in patients treated with peginterferon when considering both sensitivity and specificity compared with serum HBV DNA.

Therapeutic control of hepatitis C virus: the role of neutralizing monoclonal antibodies

Liver failure associated with hepatitis C virus (HCV) accounts for a substantial portion of liver transplantation. Although current therapy helps some patients with chronic HCV infection, adverse side effects and a high relapse rate are major problems. These problems are compounded in liver transplant recipients as reinfection occurs shortly after transplantation. One approach to control reinfection is the combined use of specific antivirals together with HCV-specific antibodies. Indeed, a number of human and mouse monoclonal antibodies to conformational and linear epitopes on HCV envelope proteins are potential candidates, since they have high virus neutralization potency and are directed to epitopes conserved across diverse HCV genotypes. However, a greater understanding of the factors contributing to virus escape and the role of lipoproteins in masking virion surface domains involved in virus entry will be required to help define those protective determinants most likely to give broad protection. An approach to immune escape is potentially caused by viral infection of immune cells leading to the induction hypermutation of the immunoglobulin gene in B cells. These effects may contribute to HCV persistence and B cell lymphoproliferative diseases.

Identification of a broadly cross-reacting and neutralizing human monoclonal antibody directed against the hepatitis C virus E2 protein

Identification of anti-hepatitis C virus (anti-HCV) human antibody clones with broad neutralizing activity is important for a better understanding of the interplay between the virus and host and for the design of an effective passive immunotherapy and an effective vaccine. We report the identification of a human monoclonal Fab (e137) able to bind the HCV E2 glycoprotein of all HCV genotypes but genotype 5. The results of antibody competition assays and testing the reactivity to alanine mutant E2 proteins confirmed that the e137 epitope includes residues (T416, W420, W529, G530, and D535) highly conserved across all HCV genotypes. Fab e137 neutralized HCV pseudoparticles bearing genotype 1a, 1b, and 4 E1-E2 proteins and to a lesser extent, genotype 2b. Fab e137 was also able to inhibit cell culture-grown HCV (genotype 2a). These data indicate that broadly cross-reacting and cross-neutralizing antibodies are generated during HCV infection.

High incidence of hepatitis C virus reinfection within a cohort of injecting drug users

A retrospective cohort study was established of injecting drug users (IDUs) to assess evidence for hepatitis C virus (HCV) protective immunity through a comparison of incidence of initial HCV infection and HCV reinfection. Incidence of initial HCV infection was determined among HCV seronegative IDUs, and HCV reinfection determined among IDUs with newly acquired HCV infection, HCV viraemia and subsequent HCV RNA clearance. Serum was available for HCV RNA analysis from stored samples taken at the time of prior blood-borne virus screening. Potential HCV reinfection was defined as a positive HCV RNA following at least one negative HCV RNA. Incidence of initial HCV infection was 17/100 person-years (95% CI, 14-20/100 person-years). The incidence of potential HCV reinfection was 42/100 person-years (95% CI, 25-61/100 person-years), and after excluding cases without a change in HCV genotype and less than three consecutive HCV RNA negative assessment, incidence of reinfection was 31/100 person-years (95% CI, 17-62/100 person-years). Following adjustment for HCV risk behaviour variables the incidence rate ratio of HCV reinfection to initial infection was 1.11 (P = 0.8). Several cases of HCV reinfection appear to have developed persistent infection.

The neutralizing activity of anti-hepatitis C virus antibodies is modulated by specific glycans on the E2 envelope protein

Hepatitis C virus (HCV) envelope glycoproteins are highly glycosylated, with up to 5 and 11 N-linked glycans on E1 and E2, respectively. Most of the glycosylation sites on HCV envelope glycoproteins are conserved, and some of the glycans associated with these proteins have been shown to play an essential role in protein folding and HCV entry. Such a high level of glycosylation suggests that these glycans can limit the immunogenicity of HCV envelope proteins and restrict the binding of some antibodies to their epitopes. Here, we investigated whether these glycans can modulate the neutralizing activity of anti-HCV antibodies. HCV pseudoparticles (HCVpp) bearing wild-type glycoproteins or mutants at individual glycosylation sites were evaluated for their sensitivity to neutralization by antibodies from the sera of infected patients and anti-E2 monoclonal antibodies. While we did not find any evidence that N-linked glycans of E1 contribute to the masking of neutralizing epitopes, our data demonstrate that at least three glycans on E2 (denoted E2N1, E2N6, and E2N11) reduce the sensitivity of HCVpp to antibody neutralization. Importantly, these three glycans also reduced the access of CD81 to its E2 binding site, as shown by using a soluble form of the extracellular loop of CD81 in inhibition of entry. These data suggest that glycans E2N1, E2N6, and E2N11 are close to the binding site of CD81 and modulate both CD81 and neutralizing antibody binding to E2. In conclusion, this work indicates that HCV glycans contribute to the evasion of HCV from the humoral immune response.

Immunologic evidence for lack of heterologous protection following resolution of HCV in patients with non-genotype 1 infection

Chronic hepatitis C virus (HCV) infection is typically characterized by a lack of virus-specific CD4(+) T-cell-proliferative responses, but strong responses have been described in a subset of persons with persistent viremia. One possible explanation for these responses is that they were primed by an earlier resolved infection and do not recognize the current circulating virus. We defined all targeted epitopes using overlapping peptides corresponding to a genotype 1a strain in 44 patients chronically infected with different HCV genotypes (GT). Surprisingly, more HCV-specific CD4(+) T-cell responses were detected in patients with chronic non-GT1 infection compared with patients with chronic GT1 infection (P = .017). Notably, we found serologic evidence of a previous exposure to GT1 in 4 patients with non-GT1 infection, and these persons also demonstrated significantly more responses than non-GT1 patients in whom genotype and HCV serotype were identical (P < .001). Comparison of recognition of GT1-specific peptides to peptides representing autologous virus revealed the absence of cross-recognition of the autologous circulating virus. These data indicate that persistent HCV infection can occur in the presence of an HCV-specific T-cell response primed against a heterologous HCV strain, and suggest that clearance of 1 GT does not necessarily protect against subsequent exposure to a second GT.

A focus reduction neutralization assay for hepatitis C virus neutralizing antibodies

Background/Aim

The role of humoral immunity in hepatitis C virus (HCV) infection is poorly understood. Nevertheless, there is increasing interest in characterizing the neutralizing antibodies in the serum of HCV-infected patients. Focus reduction assays have been widely used to evaluate neutralizing antibody responses against a range of non-cytopathic viruses. Based on the recent development of a HCV cell culture system using the genotype 2 JFH-1-strain, we developed a focus reduction assay for HCV-neutralizing antibodies.

Methods

The focus reduction assay was based on a standard microneutralization assay in which immunostained foci on tissue culture plates are counted. The neutralizing anti-HCV antibodies titers of purified serum immunoglobulin samples from seventy-seven individuals were determined using a 50% focus reduction neutralization assay. Each titer was determined as the log value of the reciprocal antibody dilution that reduced the number of viral foci by 50%. IgG antibodies were first purified from each serum in order to avoid the facilitating effect of HDL on HCV entry.

Results

The assay's cut-off using an ELISA and RNA HCV-negative samples was found to be 1.25 log, corresponding to a dilution of 1:18. The assay was compared with a commercial HCV ELISA and exhibited specificity and sensitivity values of 100% and 96.5%, respectively, and good reproducibility (with intra-assay and inter-assay coefficients of variation of 6.7% and 12.6%, respectively). The assay did not show any cross-reactivity with anti-HIV, anti-HBs or heterophile antibody-positive samples. The neutralizing antibodies titers were 2.13 log (1:134) for homologous samples from HCV genotype 2 infected patients harboring the same genotype as JFH-1 and 1.93 log (1:85) for heterologous samples from patients infected by genotypes other than type 2. These results confirm the presence of broadly cross-neutralizing antibodies already reported using the HCV pseudoparticles system.

Conclusion

This study presents a simple, specific and reproducible cell culture-based assay for determination of HCV-neutralizing antibodies in human sera. The assay should be an important tool for gauging the relationship between the neutralizing antibodies response and viral load kinetics in acutely or chronically infected patients and for investigating the possible eradication or prevention of HCV infection by neutralizing antibodies.

Rapid induction of virus-neutralizing antibodies and viral clearance in a single-source outbreak of hepatitis C

In contrast to a detailed understanding of antiviral cellular immune responses, the impact of neutralizing antibodies for the resolution of acute hepatitis C is poorly defined. The analysis of neutralizing responses has been hampered by the fact that patient cohorts as well as hepatitis C virus (HCV) strains are usually heterogeneous, and that clinical data from acute-phase and long-term follow-up after infection are not readily available. Using an infectious retroviral HCV pseudoparticle model system, we studied a cohort of women accidentally exposed to the same HCV strain of known sequence. In this single-source outbreak of hepatitis C, viral clearance was associated with a rapid induction of neutralizing antibodies in the early phase of infection. Neutralizing antibodies decreased or disappeared after recovery from HCV infection. In contrast, chronic HCV infection was characterized by absent or low-titer neutralizing antibodies in the early phase of infection and the persistence of infection despite the induction of cross-neutralizing antibodies in the late phase of infection. These data suggest that rapid induction of neutralizing antibodies during the early phase of infection may contribute to control of HCV infection. This finding may have important implications for understanding the pathogenesis of HCV infection and for the development of novel preventive and therapeutic antiviral strategies.