Woodchuck hepatitis virus core gene deletions and proliferative responses of peripheral blood mononuclear cells stimulated by an immunodominant epitope: a viral immune escape in the woodchuck model of chronic hepatitis B?

Marmota monax and its natural infection by woodchuck hepatitis virus (WHV) could be used as a predictive model for evaluating mechanisms of viral persistence during chronic hepatitis B virus (HBV) infection. The aim of this study was to investigate the presence of viral variants in the core gene of chronically WHV-infected woodchucks that showed two different patterns of peripheral blood mononuclear cells' (PBMCs') responses after stimulation with a specific WHV core peptide. Sequences' analysis of the WHV core region from eight WHV chronically infected woodchucks have been performed after in vitro stimulation with an immunodominant epitope of the WHV core protein (amino acids [aa] 96-110). Following this stimulation, positive PBMC responses at each point of follow-up were observed for four animals (group A), and weak immune responses at one or a few points of follow-up were observed for the remaining four animals (group B). The WHV core gene sequences contained amino acid deletions (aa 84-126, aa 84-113) in three of four group A animals and in none of group B animals. In the group A animals, the same deletions were observed in liver specimens and in two of four tumor specimens. Hepatocellular carcinoma (HCC) was diagnosed in all group A animals and in one group B animal. In conclusion, internal deletions in the core region correlated with a sustained PBMC response to the immunogenic peptide (96-110) of the core protein. A possible role of this relationship in hepatocarcinogenesis could be hypothesized; however, this needs to be investigated in patients with chronic HBV infection. The evaluation of virus-specific T-cell responses and T-cell epitopes that are possibly related to the mechanisms of viral evasion should be further investigated in order to design combined antiviral and immune approaches to control chronic HBV infection.

Switched memory B cells maintain specific memory independently of serum antibodies: the hepatitis B example.

The immunogenicity of a vaccine is conventionally measured through the level of serum Abs early after immunization, but to ensure protection specific Abs should be maintained long after primary vaccination. For hepatitis B, protective levels often decline over time, but breakthrough infections do not seem to occur. The aim of this study was to demonstrate whether, after hepatitis B vaccination, B-cell memory persists even when serum Abs decline. We compared the frequency of anti-hepatitis-specific memory B cells that remain in the blood of 99 children five years after priming with Infanrix -hexa (GlaxoSmithKline) (n=34) or with Hexavac (Sanofi Pasteur MSD) (n=65). These two vaccines differ in their ability to generate protective levels of IgG. Children with serum Abs under the protective level, <10 mIU/mL, received a booster dose of hepatitis B vaccine, and memory B cells and serum Abs were measured 2 wk later. We found that specific memory B cells had a similar frequency in all children independently of primary vaccine. Booster injection resulted in the increase of memory B cell frequencies (from 11.3 in 10(6) cells to 28.2 in 10(6) cells, p<0.01) and serum Abs (geometric mean concentration, GMC from 2.9 to 284 mIU/mL), demonstrating that circulating memory B cells effectively respond to Ag challenge even when specific Abs fall under the protective threshold.

Recommendations for the prevention, diagnosis, and treatment of chronic hepatitis B and C in special population groups (migrants, intravenous drug users and prison inmates).

The global spread of hepatitis B virus (HBV) and hepatitis C virus (HCV), their high chronicity rates and their progression to cirrhosis and hepatocellular carcinoma, are major public health problems. Research and intervention programmes for special population groups are needed in order to assess their infection risk and set up suitable prevention and control strategies. Aim of this paper is to give health care professionals information on HBV and HCV infections amongst migrants, drug users and prison inmates. The manuscript is an official Position Paper on behalf of the following Scientific Societies: Italian Association for the Study of the Liver (A.I.S.F.), Italian Society of Infectious and Tropical Diseases (S.I.M.I.T.), Italian Federation Department's Operators and Addiction Services (FederSerD), Italian Prison Medicine and Healthcare Society (S.I.M.S.Pe.). The considered population groups, having a high prevalence HBV and HCV infections, require specific interventions. In this context, the expression "special population" refers to specific vulnerable groups at risk of social exclusion, such as migrants, prison inmates, and intravenous drug users. When dealing with special population groups, social, environmental and clinical factors should be considered when selecting candidates for therapy as indicated by national and international guidelines.

A computational approach identifies two regions of Hepatitis C Virus E1 protein as interacting domains involved in viral fusion process.

BACKGROUND: The E1 protein of Hepatitis C Virus (HCV) can be dissected into two distinct hydrophobic regions: a central domain containing an hypothetical fusion peptide (FP), and a C-terminal domain (CT) comprising two segments, a pre-anchor and a trans-membrane (TM) region. In the currently accepted model of the viral fusion process, the FP and the TM regions are considered to be closely juxtaposed in the post-fusion structure and their physical interaction cannot be excluded. In the present study, we took advantage of the natural sequence variability present among HCV strains to test, by purely sequence-based computational tools, the hypothesis that in this virus the fusion process involves the physical interaction of the FP and CT regions of E1. RESULTS: Two computational approaches were applied. The first one is based on the co-evolution paradigm of interacting peptides and consequently on the correlation between the distance matrices generated by the sequence alignment method applied to FP and CT primary structures, respectively. In spite of the relatively low random genetic drift between genotypes, co-evolution analysis of sequences from five HCV genotypes revealed a greater correlation between the FP and CT domains than respect to a control HCV sequence from Core protein, so giving a clear, albeit still inconclusive, support to the physical interaction hypothesis.The second approach relies upon a non-linear signal analysis method widely used in protein science called Recurrence Quantification Analysis (RQA). This method allows for a direct comparison of domains for the presence of common hydrophobicity patterns, on which the physical interaction is based upon. RQA greatly strengthened the reliability of the hypothesis by the scoring of a lot of cross-recurrences between FP and CT peptides hydrophobicity patterning largely outnumbering chance expectations and pointing to putative interaction sites. Intriguingly, mutations in the CT region of E1, reducing the fusion process in vitro, strongly reduced the amount of cross-recurrence further supporting interaction between this region and FP. CONCLUSION: Our results support a fusion model for HCV in which the FP and the C-terminal region of E1 are juxtaposed and interact in the post-fusion structure. These findings have general implications for viruses, as any visualization of the post-fusion FP-TM complex has been precluded by the impossibility to obtain crystallised viral fusion proteins containing the trans-membrane region. This limitation gives to sequence based modelling efforts a crucial role in the sketching of a molecular interpretation of the fusion process. Moreover, our data also have a more general relevance for cell biology as the mechanism of intracellular fusion showed remarkable similarities with viral fusion.

HCV genetic variability: from quasispecies evolution to genotype classification.

HCV is a ssRNA virus belonging to the Flaviviruses and is found worldwide worldwide in humans. Following primary infection, persistent infection develops in more than 85% of cases, which in up to 30% of cases, may progress to liver disease, cirrhosis and hepatocellular carcinoma. The virus presents a high degree of genetic variability owing to the combination of a lack of proofreading by the RNA-dependent RNA polymerase and a high level of viral replication. This genetic variability allows the classification of genotypes, subtypes, isolates and quasispecies to which epidemiological and pathogenetic significance may be associated. The features and biological implications of HCV variability and of quasispecies dynamics in infection transmission, mechanisms of chronicity and resistance to antiviral therapy are discussed.

Microarray analysis identifies a common set of cellular genes modulated by different HCV replicon clones.

BACKGROUND: Hepatitis C virus (HCV) RNA synthesis and protein expression affect cell homeostasis by modulation of gene expression. The impact of HCV replication on global cell transcription has not been fully evaluated. Thus, we analysed the expression profiles of different clones of human hepatoma-derived Huh-7 cells carrying a self-replicating HCV RNA which express all viral proteins (HCV replicon system). RESULTS: First, we compared the expression profile of HCV replicon clone 21-5 with both the Huh-7 parental cells and the 21-5 cured (21-5c) cells. In these latter, the HCV RNA has been eliminated by IFN-alpha treatment. To confirm data, we also analyzed microarray results from both the 21-5 and two other HCV replicon clones, 22-6 and 21-7, compared to the Huh-7 cells. The study was carried out by using the Applied Biosystems (AB) Human Genome Survey Microarray v1.0 which provides 31,700 probes that correspond to 27,868 human genes. Microarray analysis revealed a specific transcriptional program induced by HCV in replicon cells respect to both IFN-alpha-cured and Huh-7 cells. From the original datasets of differentially expressed genes, we selected by Venn diagrams a final list of 38 genes modulated by HCV in all clones. Most of the 38 genes have never been described before and showed high fold-change associated with significant p-value, strongly supporting data reliability. Classification of the 38 genes by Panther System identified functional categories that were significantly enriched in this gene set, such as histones and ribosomal proteins as well as extracellular matrix and intracellular protein traffic. The dataset also included new genes involved in lipid metabolism, extracellular matrix and cytoskeletal network, which may be critical for HCV replication and pathogenesis. CONCLUSION: Our data provide a comprehensive analysis of alterations in gene expression induced by HCV replication and reveal modulation of new genes potentially useful for selection of antiviral targets.

Rare HVR1-HCV genotype 1b variants in patients with B non Hodgkin's lymphoma. Comparison with viral sequences detected in cases of lymphoproliferative disorders and B cell compartmentalisation.

We compared the E2-HVR1 region in HCV-1b positive B-NHL cases from a multicenter study with sequences from studies related to lymphoproliferative disorders and B cell compartmentalisation. We found rare and unique mutations both in B-NHL isolates and in cases with lymphoproliferative disorders and lymphocyte infection. These rare mutations could have an important effect on HVR1 region and, as a consequence, on the binding of E2 on CD81, with a possible implication for both antigenic stimulation and HCV entry. In conclusion, the HCV predominants circulating in B-NHL cases seem to be associated with clonal selection of rare variants.

Modulation of RANTES expression by HCV core protein in liver derived cell lines.

BACKGROUND: Hepatitis C virus (HCV) infection is associated with high percentage of chronicity which implies the ability of the virus to evade or modulate host cell immune system. Modulation of chemokines, such as RANTES may be part of the virus induced pathogenicity. We examined the effect of core and structural proteins of HCV on RANTES expression in two liver derived cell lines, HepG2 and Chang Liver (CHL). METHODS: HepG2 and Chang Liver (CHL) cell lines were established and selected for constitutive expression of HCV core and structural genes. Flow cytometry and quantitative RT-PCR analysis were performed to examine the effect of HCV core protein on RANTES expression. Luciferase analysis after RANTES-Luc-promoter transfection of established cell lines was assayed by luminometer measurements (RLU) of RANTES promoter activity. IRF-1 and IRF-7 expression was then examined by immunoblotting analysis. RESULTS: Results of flow cytometry and RT-PCR analysis indicated that RANTES is differentially regulated by HCV core protein in the two cell lines examined as its expression was inhibited in HepG2 cells, by a reduction of RANTES promoter activity. Conversely, RANTES protein and mRNA were induced by the core protein in CHL cells, through the induction of the promoter. Since HCV genome modulates IRF-1 and IRF-7 in replicon system and IRF-1, IRF-3 and IRF-7 have been reported to regulate RANTES promoter in various cell systems, analysis of the mechanism underlying RANTES modulation by the core protein revealed that IRF-1 expression was induced in HepG2 cells by the core protein, whereas in CHL cells it was expressed at a very low level that was not influenced by transfection with the core protein construct. This suggested that IRF-1 level may mediate the expression of RANTES in cell lines of liver origin. The effect of the core protein on RANTES promoter was countered by co-transfection with NF90, a double-stranded-RNA binding protein that activates some interferon response genes and acts as a component of cell defense against viral infection. CONCLUSION: HCV core protein have opposite effects on the expression of RANTES in different cell types in vitro, possibly reflecting a similar scenario in different microenvironments in vivo.

Repression of interferon regulatory factor 1 by hepatitis C virus core protein results in inhibition of antiviral and immunomodulatory genes.

Hepatitis C virus (HCV) proteins are known to interfere at several levels with both innate and adaptive responses of the host. A key target in these effects is the interferon (IFN) signaling pathway. While the effects of nonstructural proteins are well established, the role of structural proteins remains controversial. We investigated the effect of HCV structural proteins on the expression of interferon regulatory factor 1 (IRF-1), a secondary transcription factor of the IFN system responsible for inducing several key antiviral and immunomodulatory genes. We found substantial inhibition of IRF-1 expression in cells expressing the entire HCV replicon. Suppression of IRF-1 synthesis was mainly mediated by the core structural protein and occurred at the transcriptional level. The core protein in turn exerted a transcriptional repression of several interferon-stimulated genes, targets of IRF-1, including interleukin-15 (IL-15), IL-12, and low-molecular-mass polypeptide 2. These data recapitulate in a unifying mechanism, i.e., repression of IRF-1 expression, many previously described pathogenetic effects of HCV core protein and suggest that HCV core-induced IRF-1 repression may play a pivotal role in establishing persistent infection by dampening an effective immune response.

High prevalence of hepatitis B virus infection in B-cell non-Hodgkin's lymphoma.

In this hospital-based, multicenter case-control study we investigated the prevalence of hepatitis B virus (HBV)-related markers and HBV/hepatitis C virus (HCV) co-infection among B-cell non-Hodgkin's lymphoma (B-NHL) cases and controls. Four hundred newly diagnosed B-NHL cases and 392 controls from other departments of the same hospitals were studied. The prevalence of positivity for hepatitis B surface antigen (HBsAg) was 8.5% among B-NHL cases and 2.8% among controls (adjusted odds ratio, 3.67; 95% confidence interval, 1.75-7.66). HBV/HCV co-infection was found in four cases, but in no controls. The finding of a positive association between HBV infection and B-NHL raises the possibility that HBV may play an etiologic role in the induction of B-NHL.

Lack of WHV integration nearby N-myc2 and in the downstream b3n and win loci in a considerable fraction of liver tumors with activated N-myc2 from naturally infected wild woodchucks.

In liver tumors induced by chronic WHV infection in the WHV/woodchuck model of HBV infection, activation of genes of the myc family by WHV insertion has been well documented. Several studies have shown that N-myc2 is by far the most frequently involved, and in most cases, its transcriptional activation is due to WHV insertion nearby the gene. N-myc2 has been shown to be also activated by WHV insertion in two downstream loci, b3n and win. Although the extent of insertion in these latter loci in woodchuck tumors has not been investigated, their discovery has led to the notion that therein WHV insertion accounts for N-myc2 activation in the remaining tumors expressing the proto-oncogene in absence of any detectable alteration nearby the gene, a notion remained unproved and not further investigated yet. In the majority of cases, the above observations were derived from tumors developed in colony born laboratory bred woodchucks experimentally infected with standardized viral inocula, mostly of the same lineage. In the present work, we investigated a survey of liver tumors naturally developed in wild woodchucks with naturally acquired chronic WHV infection. Tumors had histological features of well to moderately differentiated HCCs. In most animals, multiple tumor nodules were observed; in the great majority of cases, they were shown to be independent tumors because their WHV integration patterns were not clonally related. 53 independent tumors were investigated for N-myc activation and WHV integration nearby N-myc genes and in the b3n and win loci. Comparison of our results with data from previous studies revealed that, in tumors from naturally infected wild woodchucks, the frequency of WHV integration nearby N-myc2 has a tendency to be lower and, in addition, N-myc2 activation is due to WHV integration nearby the gene significantly less frequently than in tumors from experimentally infected colony born animals (12/28, 43% vs. 15/20, 75%, P = 0.0397). These findings are likely related to the less uniform conditions as to infecting virus and host genetic background in naturally infected wild woodchucks with respect to experimentally infected colony born woodchucks and suggest that viral and/or host factors may influence the site of viral insertion finally detected in overt tumors. In addition, more than one third (11/28, 39%) tumors with activated N-myc2 transcription did not show rearrangement either nearby the gene, or in b3n or in win. These findings challenge the notion that integration in the downstream b3n and win loci is responsible for N-myc2 activation in tumors lacking insertion nearby N-myc2 and suggest that in a considerable fraction of liver tumors, at least from wild woodchucks, N-myc2 activation might be due either to WHV integration in further regions of the N-myc2 chromosomal domain or to other mechanisms related or unrelated to viral insertion.

The win locus involved in activation of the distal N-myc2 gene upon WHV integration in woodchuck liver tumors harbors S/MAR elements.

Woodchuck hepatitis virus (WHV) and the woodchuck (Marmota monax) are models for hepatocellular carcinoma (HCC) induced by hepatitis B virus (HBV). In woodchuck liver tumors, the N-myc2 proto-oncogene is frequently activated by WHV integration either close to the gene or in the b3n and win downstream loci, located 10 and 150 kb from N-myc2, respectively. A scaffold/matrix attachment region (S/MAR) regulative element was shown to be in b3n, possibly mediating activation of the upstream N-myc2 gene upon WHV integration. To investigate if S/MAR elements are in win too, a 17-kb DNA fragment corresponding to the major region of WHV insertion in this locus was cloned and sequenced. Overlapping subcloned fragments spanning candidate S/MARs predicted by sequence analysis were tested by standard in vitro binding assays. Results showed the presence of two S/MAR elements in win. The distribution of previously described WHV insertions relative to the S/MARs reinforces the hypothesis that S/MARs nearby distal WHV insertions might be involved in long-range activation of N-myc2.

Prevalence of hepatitis C virus infection in lymphoproliferative diseases other than B-cell non-Hodgkin's lymphoma, and in myeloproliferative diseases: an Italian Multi-Center case-control study.

BACKGROUND AND OBJECTIVES: Infection with hepatitis C virus (HCV) is associated with type II mixed cryoglobulinemia (MC), a lymphoproliferative disorder which, in some patients, evolves into overt B-cell non-Hodgkin's lymphoma (B-NHL). Recently, also the association between HCV infection and B-NHL, which had long been controversial, was confirmed in a large case-control study. Little knowledge is, however, available on possible associations between HCV infection and other lymphoid or myeloid malignancies. The present study was set up in order to investigate this aspect. DESIGN AND METHODS: The study was conducted in hematology departments of ten hospitals in different Italian cities. The cases consisted of consecutive patients with a new diagnosis of T-NHL, Hodgkin's disease (HD), chronic lymphocytic leukemia (CLL), acute lymphoblastic leukemia (ALL), multiple myeloma (MM), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML). The controls were patients in other departments of the same hospitals. HCV infection was investigated by testing for HCV antibodies and HCV-RNA in serum samples. RESULTS: The prevalence of HCV infection was not higher in patients with HD (3.2%, 5 out of 157 cases) or MM (4.7%, 5 out of 107) than in controls. On the other hand, it was consistently higher in T-NHL (13.8%, 4 out of 30), CLL (9.0%, 9 out of 100), ALL (7.6%, 5 out of 54), AML (7.9%, 11 out of 140), and CML (12.2%, 6 out of 49) patients. These patient groups were not, however, large enough to render statistically significant results. INTERPRETATION AND CONCLUSIONS: Our data suggest that HCV infection may be associated not only with B-NHL but also with some other lymphoid and myeloid malignancies.

Expression of HCV E1 protein in baculovirus-infected cells: effects on cell viability and apoptosis induction.

The molecular mechanisms of pathogenesis in hepatitis C virus (HCV) infection are not yet understood. Recently, we reported that the expression of the envelope protein E1 is toxic for Escherichia coli cells. The toxicity is related to the ability of C-terminal transmembrane (TM) domain of E1 to modify membrane permeability. In this study we expressed the E1 protein, complete (a.a. 192-383) or deleted (a.a. 192-340) of the TM region, fused to the C-terminus of glutathione-S-transferase by two recombinant baculoviruses. Infection of Sf9 insect cells by E1 baculovirus induced a rapid decrease in cell viability in the first 18-24 h postinfection. Premature cytopathic changes and low level of E1 protein expression were also reported. The analysis of DNA isolated from cells revealed a typical internucleosomal ladder pattern characteristic of apoptosis. The DNA degradation was first detected at 18 h postinfection by ethidium bromide gel electrophoresis and was confirmed by TUNEL assay. The results indicated that the C-terminal domain of E1 is essential for apoptosis induction as neither cell death nor DNA degradation were observed following infection with the recombinant baculovirus expressing the C-terminal-deleted E1. These findings support the hypothesis that the TM domain of E1 may play a role in viral pathogenesis.

Hepatitis C virus and B-cell non-Hodgkin lymphomas: an Italian multicenter case-control study.

The existence of an association between infection with hepatitis C virus (HCV) and B-cell non-Hodgkin lymphoma (B-NHL) remains controversial, largely because previous studies were based on prevalent case series or comparisons with less than optimal control groups. This hospital-based case-control study was conducted from January 1998 through February 2001 to evaluate the association between HCV infection and B-NHL of different types. Cases were consecutive patients with a new diagnosis of B-NHL; controls were patients from other departments of the same hospitals. Both groups were interviewed using a standardized questionnaire. The prevalence of HCV infection was calculated by histologic type of B-NHL and clinical behavior (indolent or aggressive). Adjusted odds ratio (OR) and HCV-attributable risk (AR) were estimated. HCV prevalence was 17.5% among the 400 lymphoma patients and 5.6% among the 396 controls. The OR of B-NHL (patients vs controls), adjusted by age, sex, level of education, and place of birth, was 3.1 (95% confidence interval [CI], 1.8-5.2); an OR indicative of positive association was found for indolent and aggressive B-NHL. The estimated AR was 4.6%. This study confirms an association between HCV and B-NHL. In Italy, 1 of 20 instances of B-NHL may be attributable to HCV infection and may, thus, benefit from antiviral treatment.

Viral determinants and host immune responses in the pathogenesis of HBV infection.

Hepatitis B virus (HBV) is a virus that infects about 350,000,000 people worldwide with a clinical spectrum of acute hepatitis, the healthy carrier state, cirrhosis and hepatocellular carcinoma (HCC). The outcome of HBV infection is the result of complicated viral-host interactions. As in other infections with non-cythopatic viruses, the immune response is thought to play a crucial role in disease pathogenesis but there is increasing evidence that a variety of viral mechanisms, some depending on the function of virally encoded proteins, have a profound impact on the infected hepatocytes, the liver microenvironment, and host anti-viral responses. Indeed, the virus has evolved multiple mechanisms to ensure its success in infecting a susceptible host. The essential aspects of the life cycle of HBV and the host immune response are reviewed and recent new developments in the molecular virology of HBV, including experimental animal models, in the role of accessory viral proteins in disease pathogenesis and HCC development and in the characterisation of the T cell response in the control of HBV infection, are highlighted.