Subversion of immune responses by hepatitis C virus: immunomodulatory strategies beyond evasion?

Liver Abnormalities after Elimination of HCV Infection: Persistent Epigenetic and Immunological Perturbations Post-Cure

Chronic hepatitis C (CHC) is a major cause of hepatocellular carcinoma (HCC) worldwide. While directly acting antiviral (DAA) drugs are now able to cure virtually all hepatitis C virus (HCV) infections, even in subjects with advanced liver disease, what happens to the liver and progression of the disease after DAA-induced cure of viremia is only beginning to emerge. Several large-scale clinical studies in different patient populations have shown that patients with advanced liver disease maintain a risk for developing HCC even when the original instigator, the virus, is eliminated by DAAs. Here we review emerging studies derived from multiple, complementary experimental systems involving patient liver tissues, human liver cell cultures, human liver slice cultures, and animal models, showing that HCV infection induces epigenetic, signaling, and gene expression changes in the liver associated with altered hepatic innate immunity and liver cancer risk. Of critical importance is the fact that these virus-induced abnormalities persist after DAA cure of HCV. These nascent findings portend the discovery of pathways involved in post-HCV immunopathogenesis, which may be clinically actionable targets for more comprehensive care of DAA-cured individuals.

Risk factors for multidrug-resistant organisms among deceased organ donors

Donor infection or colonization with a multidrug-resistant organism (MDRO) affects organ utilization and recipient antibiotic management. Approaches to identifying donors at risk of carrying MDROs are unknown. We sought to determine the risk factors for MDROs among transplant donors. A multicenter retrospective cohort study was conducted at four transplant centers between 2015 and 2016. All deceased donors who donated at least one organ were included. Cultures obtained during the donor's terminal hospitalization and organ procurement were evaluated. The primary outcome was isolation of an MDRO on culture. Multivariable Cox regression was used to determine risk factors associated with time to donor MDRO. Of 440 total donors, 64 (15%) donors grew an MDRO on culture. Predictors of an MDRO on donor culture included hepatitis C viremia (hazard ratio [HR] 4.09, 95% confidence interval [CI] 1.71-9.78, P = .002), need for dialysis (HR 4.59, 95% CI 1.09-19.21, P = .037), prior hematopoietic cell transplant (HR 7.57, 95% CI 1.03-55.75, P = .047), and exposure to antibiotics with a narrow gram-negative spectrum (HR 1.13, 95% CI 1.00-1.27, P = .045). This is the first study to determine risk factors for MDROs among deceased donors and will be important for risk stratifying potential donors and informing transplant recipient prophylaxis.

Hepatitis C Virus-Induced Myeloid-Derived Suppressor Cells Suppress NK Cell IFN-γ Production by Altering Cellular Metabolism via Arginase-1

The hepatitis C virus (HCV) infects ∼ 200 million people worldwide. The majority of infected individuals develop persistent infection, resulting in chronic inflammation and liver disease, including cirrhosis and hepatocellular carcinoma. The ability of HCV to establish persistent infection is partly due to its ability to evade the immune response through multiple mechanisms, including suppression of NK cells. NK cells control HCV replication during the early phase of infection and regulate the progression to chronic disease. In particular, IFN-γ produced by NK cells limits viral replication in hepatocytes and is important for the initiation of adaptive immune responses. However, NK cell function is significantly impaired in chronic HCV patients. The cellular and molecular mechanisms responsible for impaired NK cell function in HCV infection are not well defined. In this study, we analyzed the interaction of human NK cells with CD33(+) PBMCs that were exposed to HCV. We found that NK cells cocultured with HCV-conditioned CD33(+) PBMCs produced lower amounts of IFN-γ, with no effect on granzyme B production or cell viability. Importantly, this suppression of NK cell-derived IFN-γ production was mediated by CD33(+)CD11b(lo)HLA-DR(lo) myeloid-derived suppressor cells (MDSCs) via an arginase-1-dependent inhibition of mammalian target of rapamycin activation. Suppression of IFN-γ production was reversed by l-arginine supplementation, consistent with increased MDSC arginase-1 activity. These novel results identify the induction of MDSCs in HCV infection as a potent immune evasion strategy that suppresses antiviral NK cell responses, further indicating that blockade of MDSCs may be a potential therapeutic approach to ameliorate chronic viral infections in the liver.

Non-classical MHC-I human leukocyte antigen (HLA-G) in hepatotropic viral infections and in hepatocellular carcinoma

The human leukocyte antigen (HLA)-G is a "nonclassical" major histocompatibility complex (MHC) class Ib gene, located at chromosome 6, in the 6p21.3 region. The HLA-G presents immunomodulatory functions essential in pregnancy for the tolerance of the semi-allogenic fetus, but an abnormal expression of HLA-G has been observed in numerous pathological conditions, such as tumors, autoimmune diseases and viral infections. In recent years, numerous studies have assessed the clinical relevance of HLA-G expression in different types of cancer: in general, a higher HLA-G expression correlates with a lower survival rate or a shorter disease-free survival. Altered expression of HLA-G has been found in both HCV and HBV infection, and some genetic polymorphisms have been associated with altered susceptibility/disease development for these infections, however, whether the biologic role of HLA-G in HCV and HBV infection is beneficial or hazardous, it is not completely clear. In the context of hepatocellular carcinoma, HLA-G has shown a potential diagnostic role, moreover a prognostic value in HCC patients has been also attributed to HLA-G molecules. We revise here the role of HLA-G in hepatotropic HBV/HCV infections and in hepatocellular carcinoma (HCC).

Impact of hepatitis C virus heterogeneity on interferon sensitivity: an overview

Hepatitis C virus (HCV) is a major cause of liver disease worldwide. HCV is able to evade host defense mechanisms, including both innate and acquired immune responses, to establish persistent infection, which results in a broad spectrum of pathogenicity, such as lipid and glucose metabolism disorders and hepatocellular carcinoma development. The HCV genome is characterized by a high degree of genetic diversity, which can be associated with viral sensitivity or resistance (reflected by different virological responses) to interferon (IFN)-based therapy. In this regard, it is of importance to note that polymorphisms in certain HCV genomic regions have shown a close correlation with treatment outcome. In particular, among the HCV proteins, the core and nonstructural proteins (NS) 5A have been extensively studied for their correlation with responses to IFN-based treatment. This review aims to cover updated information on the impact of major HCV genetic factors, including HCV genotype, mutations in amino acids 70 and 91 of the core protein and sequence heterogeneity in the IFN sensitivity-determining region and IFN/ribavirin resistance-determining region of NS5A, on virological responses to IFN-based therapy.

An unbalanced PD-L1/CD86 ratio in CD14(++)CD16(+) monocytes is correlated with HCV viremia during chronic HCV infection

Circulating monocyte subsets with distinct functions play important roles in hepatitis C virus (HCV) infection. However, the mechanisms have not been well studied. In this study, we analyzed the distributions and phenotypic characteristics of three circulating monocyte subsets-CD14(++)CD16(-), CD14(++)CD16(+) and CD14(+/dim)CD16(+)-in chronic HCV-infected patients, HCV spontaneous resolvers and healthy controls, and we evaluated the possible link between HCV viremia and disease progression. Our results indicated that the frequency of the CD14(++)CD16(+) monocyte subset was decreased, and negatively correlated with HCV RNA and core antigen levels during chronic HCV infection. PD-L1 expression and the PD-L1/CD86 ratio in CD14(++)CD16(+) monocytes were higher during chronic HCV infection than in spontaneous HCV resolvers and healthy controls. The PD-L1/CD86 ratio positively correlated with HCV viral load and core antigen levels. Finally, PD-L1 was significantly increased, while cytokine secretions were dramatically decreased upon Toll-like receptor (TLR) ligand binding and HCV JFH-1stimulation. These findings indicates the compromised immune status of the CD14(++)CD16(+) monocytes during chronic HCV infection and provides new insights into the specific role of the CD14(++)CD16(+) monocytes and their significance in chronic HCV infection.

T cell receptor variable β gene repertoire in liver and peripheral blood lymphocytes of chronically hepatitis C virus-infected patients with and without mixed cryoglobulinaemia

To characterize the repertoire of T lymphocytes in chronically hepatitis C virus (HCV)-infected patients with and without mixed cryoglobulinaemia (MC). T cell receptor (TCR) variable (V) β clonalities in portal tracts isolated from liver biopsy sections with a laser capture microdissection technique in 30 HCV-positive MC patients were studied by size spectratyping. Complementarity-determining region 3 (CDR3) profiles of liver-infiltrating lymphocytes (LIL) were also compared with those circulating in the blood. The representative results of TCR Vβ by CDR3 were also obtained from liver tissues and peripheral blood lymphocytes (PBL) of 21 chronically HCV-infected patients without MC. LIL were highly restricted, with evidence of TCR Vβ clonotypic expansions in 23 of 30 (77%) and in 15 of 21 (71%) MC and non-MC patients, respectively. The blood compartment contained TCR Vβ expanded clones in 19 (63%) MC and 12 (57%) non-MC patients. The occurrence of LIL clonalities was detected irrespective of the degree of liver damage or circulating viral load, whereas it correlated positively with higher levels of intrahepatic HCV RNA. These results support the notion that TCR Vβ repertoire is clonally expanded in HCV-related MC with features comparable to those found in chronically HCV-infected patients without MC.

HCV J6/JFH1 tilts the capability of myeloid-derived dendritic cells to favor the induction of immunosuppression and Th17-related inflammatory cytokines

PURPOSE

How HCV virus affects the function of dendritic cells (DCs) and their ability to induce CD4+ T cell response remains not fully understood. This study was done to elucidate the impact of HCV on the function of DCs and on DC's capability to induce CD4+ T-cell response.

METHODS

Monocyte-derived DCs (MoDCs) were treated with cell-culture HCV (HCVcc). The effects of HCVcc on DC maturation, CD40L-induced DC maturation, and cytokine production and the capacity of DCs to induce Th cytokine production of allogeneic CD4+ T cells were evaluated.

RESULTS

HCVcc exposure increased expression of both IL-6 and IL-10 by MoDCs. HCV-exposed MoDCs also selectively facilitated allogeneic CD4+ T cells to further produce Th17-related cytokines interleukin 1 (IL-1), IL-6, and IL-17A. Pretreatment of IL-17A inhibited HCV production in Huh7.5 cells, suggesting that induction of Th17 cells may be beneficial to host anti-HCV immunity. Paradoxically, induction of IL-10 expression and the failure of HCV-exposed MoDCs to facilitate other Th cell development may hinder the anti-viral immunity.

CONCLUSIONS

This study highlights both the therapeutic potential of IL-17A in treating HCV infection and the cautious consideration of HCV-induced immunosuppression in DC-based therapy.

Construction and preparation of three recombinant adenoviruses expressing truncated NS3 and core genes of hepatitis C virus for vaccine purposes

BACKGROUND

In spite of dozens of clinical trials to establish effective therapeutic and/or preventive vaccine to resolve HCV infection, no real vaccine has been proved to date. Genetic vaccines based on replication-defective adenoviruses have proved to elicit strong and long lasting T-cell responses against a number of viral antigens and are even currently being used for vaccine trials in humans. According to the controversy in the immune modulatory effects of both core and NS3 full length genes, it seemed more practical to employ some parts of these HCV proteins for vaccine design.

OBJECTIVES

To generate recombinant Adenoviral vectors containing new overlapping-truncated region of NS3 gene or both the N- and C-terminal deleted parts of core gene, as well as a fusion fragment derived from both of them.

MATERIALS AND METHODS

The corresponding transfer vectors expressing truncated fragments of core, NS3 or a fusion fragment of both genes were prepared. The integrity and sequence of the transfer vectors were confirmed, and followed by experiments involving homologous recombination between them and the adenovirus backbone plasmid in the bacterial host. Recombinant Ad-pNS3, Ad-pCore and Ad-pNS3pCore viruses were prepared by transfection of these new recombined constructs into 293 packaging cell lines. The virus titer was then calculated by an immunohistochemistry based method. The RT-PCR, Real-Time PCR and western blotting were used to evaluate gene expression by all recombinant constructs. The production of complete virion particles was evaluated by detailed electron microscopy in addition to the appearance of typical cytopathic effects (CPE) and GFP expression patterns in 293 cells. The RT-PCR and GFP detection were employed to monitor the integrity as well as infectivity potency of the viral particles in Hep-G2 cells.

RESULTS

RT-PCR, Real-Time PCR or western blotting confirmed expression of truncated fragment of NS3, core or a fusion fragment of theirs by newly constructed Ad-pNS3, Ad-pCore, Ad- pNS3pCore particles. Electron microscopy, which revealed many adenovirus-like particles and characteristics of CPE in infected cells in addition to GFP detection, confirmed the infectivity, potency and integrity of recombinant adenoviral particles.

CONCLUSIONS

These adenoviruses expressing novel fragments of NS3 and core genes may be suitable tools to overcome shortcomings associated with full gene expression in the setting of HCV vaccine therapy.

Myeloid suppressor cells induced by hepatitis C virus suppress T-cell responses through the production of reactive oxygen species

Impaired T-cell responses in chronic hepatitis C virus (HCV) patients have been reported to be associated with the establishment of HCV persistent infection. However, the mechanism for HCV-mediated T-cell dysfunction is yet to be defined. Myeloid-derived suppressor cells (MDSCs) play a pivotal role in suppressing T-cell responses. In this study we examined the accumulation of MDSCs in human peripheral blood mononuclear cells (PBMCs) following HCV infection. We found that CD33(+) mononuclear cells cocultured with HCV-infected hepatocytes, or with HCV core protein, suppress autologous T-cell responses. HCV core-treated CD33(+) cells exhibit a CD14(+) CD11b(+/low) HLADR(-/low) phenotype with up-regulated expression of p47(phox) , a component of the NOX2 complex critical for reactive oxygen species (ROS) production. In contrast, immunosuppressive factors, arginase-1 and inducible nitric oxide synthase (iNOS), were not up-regulated. Importantly, treatment with an inactivator of ROS reversed the T-cell suppressive function of HCV-induced MDSCs. Lastly, PBMCs of chronic HCV patients mirror CD33(+) cells following treatment with HCV core where CD33(+) cells are CD14(+) CD11b(+) HLADR(-/low) , and up-regulate the expression of p47(phox).

CONCLUSION

These results suggest that HCV promotes the accumulation of CD33(+) MDSC, resulting in ROS-mediated suppression of T-cell responsiveness. Thus, the accumulation of MDSCs during HCV infection may facilitate and maintain HCV persistent infection.

Elevation of plasma soluble human leukocyte antigen-G in patients with chronic hepatitis C virus infection

The subversion of immune responses that hepatitis C virus (HCV) uses to escape immune surveillance and to establish persistent infection has been poorly understood. The immune-suppressive molecule human leukocyte antigen-G (HLA-G) has been supposed to play important roles in viral infection. In the current study, HCV genotype was analyzed in 67 chronic HCV-infected (CHC) patients. Plasma soluble sHLA-G (including sHLA-G1 and HLA-G5), interleukin-10 (IL-10), and interferon-γ (IFN-γ) levels were determined in these CHC patients and in healthy subjects by enzyme-linked immunosorbent assay, and the sHLA-G isoforms present in plasma were determined by Western blot. Data showed that HCV 1b was the predominant genotype, with a prevalence of 64.2%. sHLA-G was dramatically increased in CHC patients (median: 85.54 U/ml, range: 19.40-204.07) over that in normal controls (median: 9.13 U/ml, range: 5.07-69.56) (p < 0.001). Western blotting revealed that plasma sHLA-G was derived from sHLA-G1 and HLA-G5. IL-10 and IFN-γ levels were also significant higher in CHC patients than in normal controls (median: 16.3 pg/ml vs 1.8 pg/ml, p < 0.001, and 1025.3 pg/ml vs 858.3 pg/ml, p = 0.03, respectively). No significant association was observed for the HCV genotype and viral RNA load with the levels of sHLA-G, IL-10, and IFN-γ in CHC patients. These results indicate that elevation of sHLA-G expression in HCV patients was independent of viral genotype and viral RNA load. Given its immunotolerant property, an increase in sHLA-G may play a role in the persistency of HCV infection.

Extracellular hepatitis C virus core protein activates STAT3 in human monocytes/macrophages/dendritic cells via an IL-6 autocrine pathway

Hepatitis C virus (HCV) infection is highly efficient in the establishment of persistent infection, which leads to the development of chronic liver disease and hepatocellular carcinoma. Impaired T cell responses with reduced IFN-γ production have been reported to be associated with persistent HCV infection. Extracellular HCV core is a viral factor known to cause HCV-induced T cell impairment via its suppressive effect on the activation and induction of pro-inflammatory responses by antigen-presenting cells (APCs). The activation of STAT proteins has been reported to regulate the inflammatory responses and differentiation of APCs. To further characterize the molecular basis for the regulation of APC function by extracellular HCV core, we examined the ability of extracellular HCV core to activate STAT family members (STAT1, -2, -3, -5, and -6). In this study, we report the activation of STAT3 on human monocytes, macrophages, and dendritic cells following treatment with extracellular HCV core as well as treatment with a gC1qR agonistic monoclonal antibody. Importantly, HCV core-induced STAT3 activation is dependent on the activation of the PI3K/Akt pathway. In addition, the production of multifunctional cytokine IL-6 is essential for HCV core-induced STAT3 activation. These results suggest that HCV core-induced STAT3 activation plays a critical role in the alteration of inflammatory responses by APCs, leading to impaired anti-viral T cell responses during HCV infection.

Viral factors influencing the response to the combination therapy of peginterferon plus ribavirin in chronic hepatitis C

Hepatitis C virus (HCV) is a single-stranded RNA virus known for its high genetic variability owing to the lack of a proofreading mechanism of its RNA dependent RNA polymerase. Until now, numerous studies have been undertaken to clarify the correlation between pretreatment HCV genetic variability and the therapeutic response. Even with the recent combination therapy of peginterferon plus ribavirin for chronic hepatitis C, viral response is variable, and only half of treated patients could clear the virus [sustained viral response (SVR)]. In this review, the contribution of viral genetic variability affecting the treatment outcome is discussed according to each HCV genomic region.

The good, the bad and the ugly: how altered peptide ligands modulate immunity

BACKGROUND

The basis of T cell immune responses is the specific recognition of an immunogenic peptide epitope by a T cell receptor. Peptide alterations of such T cell epitopes with single or few amino acid variations can have drastic effects on the outcome of this recognition. These altered peptide ligands can act as modulators of immune responses as they are capable of downregulating or upregulating responses.

OBJECTIVE/METHODS

We review how altered peptide ligands can have 'good' 'bad' and 'ugly' outcomes in treating diseases.

RESULTS/CONCLUSION

Altered peptide ligands have been used as immunotherapeutics in autoimmune (and allergic) diseases, infectious diseases and cancer. In the next five years we anticipate seeing a number of altered peptide ligands in clinical trials, progressing from contradictory classifications of good, bad or ugly, to the exciting outcome of 'useful'.

Immune defence, parasite evasion strategies and their relevance for 'macroscopic phenomena' such as virulence

The discussion of host-parasite interactions, and of parasite virulence more specifically, has so far, with a few exceptions, not focused much attention on the accumulating evidence that immune evasion by parasites is not only almost universal but also often linked to pathogenesis, i.e. the appearance of virulence. Now, the immune evasion hypothesis offers a deeper insight into the evolution of virulence than previous hypotheses. Sensitivity analysis for parasite fitness and life-history theory shows promise to generate a more general evolutionary theory of virulence by including a major element, immune evasion to prevent parasite clearance from the host. Also, the study of dose-response relationships and multiple infections should be particularly illuminating to understand the evolution of virulence. Taking into account immune evasion brings immunological processes to the core of understanding the evolution of parasite virulence and for a range of related issues such as dose, host specificity or immunopathology. The aim of this review is to highlight the mechanism underlying immune evasion and to discuss possible consequences for the evolutionary ecology analysis of host-parasite interactions.

Diffuse Uterine Adenomatoid Tumor in a Patient With Chronic Hepatitis C Virus Infection

Abstract

Uterine adenomatoid tumors are usually solitary lesions. Adenomatoid tumors diffusely infiltrating the entire myometrium have rarely been reported in the literature. A feature common to half of the reported cases of diffuse uterine adenomatoid tumor was an immunocompromised status of the patient caused by the medications for renal transplantation. In this article, we describe an unusual case of diffuse uterine adenomatoid tumor in a patient with chronic hepatitis C virus infection. Pelvic examination showed an irregular and enlarged uterus. Supracervical hysterectomy and bilateral salpingo-oophorectomy was performed with a clinical diagnosis of uterine leiomyoma. Pathological examination showed, in addition to multiple leiomyomas, diffuse uterine adenomatoid tumor. We suggested that the diffuse pattern in our patient might be related to immunosuppression secondary to chronic hepatitis C virus infection.

Immune responses in hepatitis C virus infection and mechanisms of hepatitis C virus persistence

Immune responses against hepatitis C virus (HCV) play a crucial role in the pathogenesis of chronic hepatitis C. HCV infection often persists and leads to chronic hepatitis and eventually cirrhosis. Accumulated data suggest that HCV proteins suppress host immune responses through the suppression of functions of immune cells, such as cytotoxic T lymphocytes, natural killer cells, and dendritic cells. They also suppress the type 1 interferon signaling system. The resulting insufficient immune responses against HCV lead to the sustained infection. The appropriate control of immune responses would contribute to the eradication of HCV and the improvement of hepatitis, but there are still many issues to be clarified. This review describes the scientific evidence to support these emerging concepts, and will touch on the implications for improving antiviral therapy.

Blockade of PD-1/B7-H1 interaction restores effector CD8+ T cell responses in a hepatitis C virus core murine model

The impaired function of CD8(+) T cells is characteristic of hepatitis C virus (HCV) persistent infection. HCV core protein has been reported to inhibit CD8(+) T cell responses. To determine the mechanism of the HCV core in suppressing Ag-specific CD8(+) T cell responses, we generated a transgenic mouse, core(+) mice, where the expression of core protein is directed to the liver using the albumin promoter. Using a recombinant adenovirus to deliver Ag, we demonstrated that core(+) mice failed to clear adenovirus-LacZ (Ad-LacZ) infection in the liver. The effector function of LacZ-specific CD8(+) T cells was particularly impaired in the livers of core(+) mice, with suppression of IFN-gamma, TNF-alpha, and granzyme B production by CD8(+) T cells. In addition, the impaired CD8(+) T cell responses in core(+) mice were accompanied by the enhanced expression of the inhibitory receptor programmed death-1 (PD-1) by LacZ-specific CD8(+) T cells and its ligand B7-H1 on liver dendritic cells following Ad-LacZ infection. Importantly, blockade of the PD-1/B7-H1 inhibitory pathway (using a B7-H1 blocking antibody) in core(+) mice enhanced effector function of CD8(+) T cells and cleared Ad-LacZ-infection as compared with that in mice treated with control Ab. This suggests that the regulation of the PD-1/B7-H1 inhibitory pathway is crucial for HCV core-mediated impaired T cell responses and viral persistence in the liver. This also suggests that manipulation of the PD-1/B7-H1 pathway may be a potential immunotherapy to enhance effector T cell responses during persistent HCV infection.

Regulatory T cell-like responses in deer mice persistently infected with Sin Nombre virus

Hantavirus cardiopulmonary syndrome is a zoonotic illness associated with a systemic inflammatory immune response, capillary leak, noncardiogenic pulmonary edema, and shock in humans. Cytokines, including TNF, IFN-gamma, and lymphotoxin, are thought to contribute to its pathogenesis. In contrast, infected rodent reservoirs of hantaviruses experience few or no pathologic changes and the host rodent can remain persistently infected for life. Generally, it is unknown why such dichotomous immune responses occur between humans and reservoir hosts. Thus, we examined CD4(+) T cell responses from one such reservoir, the deer mouse (Peromyscus maniculatus), infected with Sin Nombre virus. Proliferation responses to viral nucleocapsid antigen were relatively weak in T cells isolated from deer mice, regardless of acute or persistent infection. The T cells from acutely infected deer mice synthesized a broad spectrum of cytokines, including IFN-gamma, IL-4, IL-5, and TGF-beta(1), but not TNF, lymphotoxin, or IL-17. However, in T cells from persistently infected deer mice, only TGF-beta(1) was expressed by all lines, whereas some expressed reduced levels of IFN-gamma or IL-5. The Forkhead box P3 transcription factor, a marker of some regulatory T cells, was expressed by most of these cells. Collectively, these data suggest that TGF-beta(1)-expressing regulatory T cells may play an important role in limiting immunopathology in the natural reservoir host, but this response may interfere with viral clearance. Such a response may have arisen as a mutually beneficial coadaptive evolutionary event between hantaviruses and their rodent reservoirs, so as to limit disease while also allowing the virus to persist.

Pathogenic potential of borna disease virus lacking the immunodominant CD8 T-cell epitope

Borna disease virus (BDV) is a highly neurotropic, noncytolytic virus. Experimentally infected B10.BR mice remain healthy unless specific antiviral T cells that infiltrate the infected brain are triggered by immunization. In contrast, infected MRL mice spontaneously mount an antiviral T-cell response that can result in meningoencephalitis and neurological disease. The antiviral T cells may, alternatively, eliminate the virus without inducing disease if they are present in sufficient numbers before the virus replicates to high titers. Since the immune response of H-2(k) mice is directed mainly against the epitope TELEISSI located in the viral nucleoprotein N, we generated BDV mutants that feature TQLEISSI in place of TELEISSI. We show that adoptive transfer of BDV N-specific CD8 T cells induced neurological disease in B10.BR mice persistently infected with wild-type BDV but not with the mutant virus expressing TQLEISSI. Surprisingly, the mutant virus replicated less well in adult MRL wild-type mice than in mutant mice lacking mature CD8 T cells. Furthermore, when MRL mice were infected with the TQLEISSI-expressing BDV mutant as newborns, neurological disease was observed, although at a lower rate and with slower kinetics than in mice infected with wild-type virus. These results confirm that TELEISSI is the major CD8 T-cell epitope in H-2(k) mice and suggest that unidentified minor epitopes are present in the BDV proteome which are recognized rather efficiently by antiviral T cells if the dominant epitope is absent.

Pretreatment sequence diversity differences in the full-length hepatitis C virus open reading frame correlate with early response to therapy

Pegylated alpha interferon and ribavirin therapy for hepatitis C virus (HCV) genotype 1 infection fails for half of Caucasian American patients (CA) and more often for African Americans (AA). The reasons for these low response rates are unknown. HCV is highly genetically variable, but it is unknown how this variability affects response to therapy. To assess effects of viral diversity on response to therapy, the complete pretreatment genotype 1 HCV open reading frame was sequenced using samples from 94 participants in the Virahep-C study. Sequences from patients with >3.5 log declines in viral RNA levels by day 28 (marked responders) were more variable than those from patients with declines of <1.4 log (poor responders) in NS3 and NS5A for genotype 1a and in core and NS3 for genotype 1b. These correlations remained when all T-cell epitopes were excluded, indicating that these differences were not due to differential immune selection. When the sequences were compared by race of the patients, higher diversity in CA patients was found in E2 and NS2 but only for genotype 1b. Core, NS3, and NS5A can block the action of alpha interferon in vitro; hence, these genetic patterns are consistent with multiple amino acid variations independently impairing the function of HCV proteins that counteract interferon responses in humans, resulting in HCV strains with variable sensitivity to therapy. No evidence was found for novel HCV strains in the AA population, implying that AA patients may be infected with a higher proportion of the same resistant strains that are found in CA patients.

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.

Hepatitis C virus infection--pathobiology and implications for new therapeutic options

Despite progress in therapeutic approaches for the elimination of hepatitis C, chronic hepatitis C virus infection remains an important cause of liver disease. Therapeutic intervention with the currently available interferon-based treatment regimens is quite successful, but treatment is difficult to tolerate and is contraindicated in many patients. A better understanding of the HCV biology, immunopathology, and liver disease will help to design better therapeutic strategies. The American Association for the Study of Liver Diseases sponsored a single-topic conference on hepatitis C virus infection on March 4 and 5, 2005, to enhance our current knowledge in the areas of basic and clinical research related to antiviral and immunomodulatory therapies in hepatitis C disease. The faculty consisted of 23 invited experts in the field of viral hepatitis. The program was divided into four sections including: (a) replicative mechanisms and models; (b) viral-host interactions; and (c) antiviral drug development and new strategies; and (d) back to the bedside-current issues. This report summarizes each of the presentations sections.

HCV immunopathogenesis: virus-induced strategies against host immunity

Worldwide more than 170 million people are chronically infected with the hepatitis C virus (HCV), which is a frequent cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Unlike infection with other hepatotropic viruses, only a small percentage of acute HCV infections are cleared, and most infected individuals develop lifelong HCV infection in the absence of efficient treatment. It is believed that both viral and host factors contribute to the inability of the host immune system to clear the initial infection and lead to the high propensity of chronic HCV infection.

Effect of pentoxifylline on levels of pro-inflammatory cytokines during chronic hepatitis C

The cellular and humoral natural immune response induced by hepatitis C virus (HCV) is commonly unable to eradicate the virus. HCV is a highly mutable, hepatotropic RNA virus that causes acute and chronic hepatitis, an infection that involves the production of various cytokines. The aim of the study is to analyse the expression of pro-inflammatory cytokines IL-1beta, TNF-alpha, IFN-gamma and the chemokine CXCL8 (IL-8) in liver tissue and their expression and secretion in PBMC of patients with chronic hepatitis C (CHC), in response to pentoxyfilline (PTX). We studied six CHC patients, naive to treatment. Patients received PTX 400 mg twice a day/8 weeks. Pentoxyfilline resulted in decreased expression of mRNA of liver IL-1beta, TNF-alpha and IFN-gamma: 144.2 versus 83.5 molecules of IL-1beta (P < 0.05), TNF-alpha 194.3 versus 17.6 molecules (P = 0.03) and IFN-gamma 26.1 versus 0.5 molecules (P = 0.04). Following PTX, PBMC exhibited a decrease in IFN-gamma mRNA 12.2 versus 1.5 molecules (P = 0.028) and CXCL8 4.2 versus 2.5 molecules (P = 0.027). In PBMC, only the secretion of TNF-alpha was decreased 1109 versus 933.5 pg/ml, P = 0.046. Production of cytokines both locally (within the liver) and systemically (PBMC) may serve as biomarkers of the infection with hepatitis C. PTX inhibits the expression of several pro-inflammatory cytokines in the liver. These results indicate that it is worth exploring PTX in hepatitis in future clinical trials in nonresponders to antiviral treatment.

Natural killer cells: primary target for hepatitis C virus immune evasion strategies?

Liver cirrhosis and hepatocellular carcinoma secondary to chronic hepatitis C virus (HCV) infection requiring transplantation represents a significant public health problem. The most remarkable feature of hepatitis C virus is the ability to establish chronic infection in the vast majority of cases. Efforts to define clinical correlates of HCV persistence have focused primarily on CD4 and CD8 T cell responses. Until recently, the role of innate immunity in determining the outcome of HCV infection had received relatively little attention. Natural killer (NK) cells are an important antiviral effector population eliminating virus through direct killing and cytokine production. Recent studies highlighting the cross-talk between NK cells, dendritic cells (DCs) and T cells have prompted reevaluation of the important role NK cells play in regulating and maintaining specific immune responses. Like many other viruses, HCV has evolved strategies to evade detection and elimination by NK cells. T cell defects observed in HCV infection may be a consequence of inhibition of NK:DC interactions. We propose a theoretical model for HCV persistence that places the NK cell at the center of HCV immune evasion strategies. While this model is only theoretical, it provides a plausible interpretation of many published observations and a useful working model to test the role of NK cells in HCV persistence. In conclusion, the role of innate immune cells and their regulation of antigen-specific responses by the initial innate response to the virus, in particular NK cells, may prove to be an informative and clinically relevant avenue of investigation.

gC1q receptor ligation selectively down-regulates human IL-12 production through activation of the phosphoinositide 3-kinase pathway

gC1qR, a complement receptor for C1q, plays a pivotal role in the regulation of inflammatory and antiviral T cell responses. Several pathogens, including hepatitis C virus, exploit gC1qR-dependent regulatory pathways to manipulate host immunity. However, the molecular mechanism(s) of gC1qR signaling involved in regulating inflammatory responses remains unknown. We report the selective inhibition of TLR4-induced IL-12 production after cross-linking of gC1qR on the surface of macrophages and dendritic cells. Suppression of IL-12 did not result from increased IL-10 or TGF-beta, but was dependent on PI3K activation. Activation of PI3K and subsequent phosphorylation of Akt define an intracellular pathway mediating gC1qR signaling and cross-talk with TLR4 signaling. This is the first report to identify signaling pathways used by gC1qR-mediated immune suppression, and it establishes a means of complement-mediated immune suppression to inhibit Th1 immunity crucial for clearing pathogenic infection.

Natural insect host-parasite systems show immune priming and specificity: puzzles to be solved

Study of the multiplicity of interactions between invertebrate hosts and their parasites helps to define the aspects of the host immune systems that have ecological and evolutionary significance. Such study, however, reveals how much is yet unknown. For instance, the costs of mounting an immune response, the nature of the long-lasting protection sometimes attained, and the high degree of specificity observed in certain hosts are phenomena that still await full explanation. An additional puzzle is the high degree of specificity achieved in light of the apparent low degree of specificity in the recognition and effector mechanisms of insect immune systems. Furthermore, while protective immunity is typically associated with vertebrate adaptive immune systems, invertebrates may have analogous capacities, whose nature is still largely unknown. This review will illustrate how the traditional host-centred view of immune defence can be usefully extended by taking account of parasite immune evasion strategies and the variation that such strategies create in the observed outcomes of infection.

Viral strategies for evading antiviral cellular immune responses of the host

The host invariably responds to infecting viruses by activating its innate immune system and mounting virus-specific humoral and cellular immune responses. These responses are aimed at controlling viral replication and eliminating the infecting virus from the host. However, viruses have evolved numerous strategies to counter and evade host's antiviral responses. Providing specific examples from the published literature, we discuss in this review article various strategies that viruses have developed to evade antiviral cellular responses of the host. Unraveling these viral strategies allows a better understanding of the host-pathogen interactions and their coevolution. This knowledge is important for identifying novel molecular targets for developing antiviral reagents. Finally, it may also help devise new knowledge-based strategies for developing antiviral vaccines.

Shared alterations in NK cell frequency, phenotype, and function in chronic human immunodeficiency virus and hepatitis C virus infections

Human immunodeficiency virus (HIV) and hepatitis C virus (HCV) cause clinically important persistent infections. The effects of virus persistence on innate immunity, including NK cell responses, and the underlying mechanisms are not fully understood. We examined the frequency, phenotype, and function of peripheral blood CD3- CD56+ NK subsets in HIV+ and HCV+ patients and identified significantly reduced numbers of total NK cells and a striking shift in NK subsets, with a marked decrease in the CD56(dim) cell fraction compared to CD56(bright) cells, in both infections. This shift influenced the phenotype and functional capacity (gamma interferon production, killing) of the total NK pool. In addition, abnormalities in the functional capacity of the CD56(dim) NK subset were observed in HIV+ patients. The shared NK alterations were found to be associated with a significant reduction in serum levels of the innate cytokine interleukin 15 (IL-15). In vitro stimulation with IL-15 rescued NK cells of HIV+ and HCV+ patients from apoptosis and enhanced proliferation and functional activity. We hypothesize that the reduced levels of IL-15 present in the serum during HIV and HCV infections might impact NK cell homeostasis, contributing to the common alterations of the NK pool observed in these unrelated infections.

Challenges and successes in developing new therapies for hepatitis C

Hepatitis C virus (HCV) will continue to be a serious global health threat for many years to come because of the chronic nature of the infection, its high prevalence and the significant morbidity of the resulting disease. Recently, a small number of molecules have produced encouraging results in proof-of-concept clinical trials. At the same time, preclinical evidence is accumulating that development of resistance will eventually limit the efficacy of new drugs. Thus, combinations of multiple agents will be required to treat chronic HCV infection.

Adaptive immune responses in acute and chronic hepatitis C virus infection

The hepatitis C virus (HCV) persists in the majority of infected individuals and is a significant cause of human illness and death globally. Recent studies have yielded important insights into immunity to HCV, in particular revealing the central role of T cells in viral control and clearance. Other key features of adaptive immune responses remain obscure, including mechanisms by which T cells control HCV replication, the role of antibodies in conferring protection and how cellular and humoral immunity are subverted in persistent infection.

Hypervariable region 1 variant acting as TCR antagonist affects hepatitis C virus-specific CD4+ T cell repertoire by favoring CD95-mediated apoptosis

We have described previously that hypervariable region 1 (HVR1) variants of hepatitis C virus (HCV) frequently act as T cell receptor (TCR) antagonists for HVR1-specific helper T cells. These naturally occurring HVR1-antagonistic sequences interfered with the effects of HVR1-agonistic sequences such as TCR down-regulation and early activatory signals. By taking advantage of these findings, in this paper, we have analyzed the fate of these HVR1-specific antagonized CD4+ T cells. We present the evidence that TCR antagonism renders agonist-activated T cells susceptible to bystander CD95-mediated killing by suppressing the expression of cellular Fas-associated death domain-like interleukin-1beta-converting enzyme-like inhibitor proteins. To verify whether the TCR repertoire of a HVR1-specific T cell population could be modified consequently, we used a HVR1-agonistic sequence to induce in vitro CD4+ T cells and another HVR1 sequence with antagonistic property to mediate suppressive phenomena. HVR1-specific T cells were cultured with the agonist alone or with the agonist plus the antagonist. HVR1 specificity and T cell repertoires were followed over time by analyzing TCR beta-variable gene segment by "spectratyping". The results showed that the specificity for the agonist was rapidly spoiled after culture in the presence of the antagonist, and the TCR repertoire was strongly modified as a result of CD95-mediated apoptosis of agonist-specific clonal expansions. These data support the hypothesis that in HCV infection, the generation of TCR antagonists may reshape the T cell repertoire, representing an efficacious immune evasion strategy of a highly mutant pathogen.

Bacterial toxins and the immune system: show me the in vivo targets

Microorganisms that cause persistent infection often exhibit specific adaptations that allow them to avoid the adaptive immune response. Recently, several bacterial toxins have been shown in vitro to disrupt immune cell functions. However, it remains to be established whether these activities are relevant during infection and whether these toxins have specifically evolved to disrupt the adaptive immune system.

DNA shuffling and screening strategies for improving vaccine efficacy

The efficacy of vaccines can be improved by increasing their immunogenicity, broadening their crossprotective range, as well as by developing immunomodulators that can be coadministered with the vaccine antigen. One technology that can be applied to each of these aspects of vaccine development is MolecularBreeding directed molecular evolution. Essentially, this technology is used to evolve genes in vitro through an iterative process consisting of recombinant generation followed by selection of the desired recombinants. We have used DNA shuffling and screening strategies to develop and improve vaccine candidates against several infectious pathogens including Plasmodium falciparum (a common cause of severe and fatal human malaria), dengue virus, encephalitic alphaviruses such as Venezuelan, western and eastern equine encephalitis viruses (VEEV, WEEV, and EEEV, respectively), human immunodeficiency virus-1 (HIV-1), and hepatitis B virus (HBV). By recombining antigen-encoding genes from different serovar isolates, new chimeras are selected for crossreactivity; these vaccine candidates are expected to provide broader crossprotection than vaccines based on a single serovar. Furthermore, the vaccine candidates can be selected for improved immunogenicity, which would also improve their efficacy. In addition to vaccine candidates, we have applied the technology to evolve several immunomodulators that when coadministered with vaccines can improve vaccine efficacy by fine-tuning the T cell response. Thus, DNA shuffling and screening technology is a promising strategy to facilitate vaccine efficacy.

Consequences of immunodominant epitope deletion for minor influenza virus-specific CD8+-T-cell responses

The extent to which CD8+ T cells specific for other antigens expand to compensate for the mutational loss of the prominent DbNP366 and DbPA224 epitopes has been investigated using H1N1 and H3N2 influenza A viruses modified by reverse genetics. Significantly increased numbers of CD8+ KbPB1(703)+, CD8+ KbNS2(114)+, and CD8+ DbPB1-F2(62)+ T cells were found in the spleen and in the inflammatory population recovered by bronchoalveolar lavage from mice that were first given the -NP-PA H1N1 virus intraperitoneally and then challenged intranasally with the homologous H3N2 virus. The effect was less consistent when this prime-boost protocol was reversed. Also, though the quality of the response measured by cytokine staining showed some evidence of modification when these minor CD8+-T-cell populations were forced to play a more prominent part, the effects were relatively small and no consistent pattern emerged. The magnitude of the enhanced clonal expansion following secondary challenge suggested that the prime-boost with the -NP-PA viruses gave a response overall that was little different in magnitude from that following comparable exposure to the unmanipulated viruses. This was indeed shown to be the case when the total response was measured by ELISPOT analysis with virus-infected cells as stimulators. More surprisingly, the same effect was seen following primary challenge, though individual analysis of the CD8+ KbPB1(703)+, CD8+ KbNS2(114)+, and CD8+ DbPB1-F2(62)+ sets gave no indication of compensatory expansion. A possible explanation is that novel, as yet undetected epitopes emerge following primary exposure to the -NP-PA deletion viruses. These findings have implications for both natural infections and vaccines.

Hepatitis C virus and the related bovine viral diarrhea virus considerably differ in the functional organization of the 5' non-translated region: implications for the viral life cycle

The 5' non-translated regions (5'NTRs) of hepatitis C virus (HCV) and bovine viral diarrhea virus (BVDV) initiate translation of the viral RNA genome through an internal ribosomal entry site (IRES) and operate as major determinants of the RNA replication cycle. We report on comparative studies with both virus systems demonstrating that the functional organization of the 5'NTRs of HCV and BVDV shows evident differences despite a similar RNA structure. In the BVDV 5'NTR, replication signals are restricted to the 5' terminal domain I. With HCV, we defined specific replication signals in domain I but also in domains II and III that constitute the functional IRES. While the BVDV domain I supports IRES activity, the HCV domain I appears to down-regulate IRES function. These data suggest that HCV and BVDV apply different mechanisms to coordinate viral protein and RNA synthesis, which may explain differences in the replication efficiency of both related viruses.

Overcoming antigenic diversity and improving vaccines using DNA shuffling and screening technologies

Viral, bacterial and parasitic pathogens have evolved multiple strategies to evade the immune response, facilitate transmission and establish chronic infections. One of the underlying strategies that pathogens have evolved is antigenic variation of immune response targets that reduce the affinity of antigen binding to antibodies and major histocompatability complex class I and II receptors. Vaccine candidates generally target a limited number of these antigen variants or combine antigens from several variants to include in multivalent vaccine formulations. DNA shuffling and screening technologies, also known as MolecularBreeding (Maxygen, Inc.) directed molecular evolution, have been successfully used to identify and develop novel and chimaeric vaccine candidates capable of inducing immune responses that recognise and control multiple antigenic variants. DNA shuffling and screening strategies also select vaccine candidates with improved immunogenicity, increased expression as recombinant polypeptides and improved growth of whole viruses in cell culture. As DNA shuffling and screening strategies can be applied to many pathogens, there remain numerous applications of DNA shuffling to solve challenging problems in vaccine process development and manufacture.

T cell response in hepatitis C virus infection

Hepatitis C virus (HCV) is a hepatotropic RNA virus that causes acute and chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. It is widely accepted that cellular immune responses play an important role in viral clearance and disease pathogenesis. However, HCV often evades effective immune recognition and has a propensity to persist in the majority of acutely infected individuals (ca. 80%). The immunological and virological basis for the inefficiency of the cellular immune response to clear or control the virus is not known. Recent studies, however, have provided new insights into the mechanisms of viral clearance and persistence that will be discussed in detail.

Fas and TNFR1, but not cytolytic granule-dependent mechanisms, mediate clearance of murine liver adenoviral infection

After intravenous injection of replication-deficient adenovirus, hepatocytes are transduced and express high levels of adenovirus-encoded genes. However, adenovirally encoded gene expression is ablated rapidly by CD8+ T-cell-dependent mechanisms. Thus, this model is suitable for examining intrahepatic cytotoxic T lymphocyte (CTL) effector mechanisms. In the present studies, recombinant adenoviruses encoding secreted (human apolipoprotein A-I) or intracellular (beta-galactosidase) gene products were infused into mice with genetic deficiencies affecting the granule exocytosis-, Fas-, or tumor necrosis factor receptor 1 (TNFR1)-mediated pathways of CTL and natural killer cell effector function; the rates of clearance of adenovirus-encoded gene products were assessed. Clearance of secreted or intracellular adenoviral gene products was not delayed in perforin-deficient mice or dipeptidyl peptidase I-deficient mice, which fail to process and activate granzyme A or granzyme B. TNFR1-deficient mice also exhibited no delay in clearance of adenoviral gene products. However, adenoviral clearance from Fas-deficient mice was delayed, and such delays were much greater in mice deficient in both TNFR1 and Fas. In contrast, chimeric mice lacking both hepatic Fas and lymphocyte perforin function exhibited no greater delay in adenoviral clearance than chimeras deficient only in hepatic Fas expression. In conclusion, Fas-dependent mechanisms are required for efficient clearance of virally infected hepatocytes and, in Fas-deficient animals, TNFR1-dependent mechanisms provide an alternative mechanism for hepatic adenovirus clearance. In contrast, perforin- and granule protease-dependent cytotoxicity mechanisms play no apparent role in clearance of adenovirus from the liver.

The virus-immunity ecosystem

The ecology of pathogenic viruses can be considered both in the context of survival in the macro-environments of nature, the theme pursued generally by epidemiologists, and in the micro-environments of the infected host. The long-lived, complex, higher vertebrates have evolved specialized, adaptive immune systems designed to minimise the consequences of such parasitism. Through evolutionary time, the differential selective pressures exerted variously by the need for virus and host survival have shaped both the "one-host" viruses and vertebrate immunity. With the development of vaccines to protect us from many of our most familiar parasites, the most dangerous pathogens threatening us now tend to be those "emerging", or adventitious, infectious agents that sporadically enter human populations from avian or other wild-life reservoirs. Such incursions must, of course, have been happening through the millenia, and are likely to have led to the extraordinary diversity of recognition molecules, the breadth in effector functions, and the persistent memory that distinguishes the vertebrate, adaptive immune system from the innate response mechanisms that operate more widely through animal biology. Both are important to contemporary humans and, particularly in the period immediately following infection, we still rely heavily on an immediate response capacity, elements of which are shared with much simpler, and more primitive organisms. Perhaps we will now move forward to develop useful therapies that exploit, or mimic, such responses. At this stage, however, most of our hopes for minimizing the threat posed by viruses still focus on the manipulation of the more precisely targeted, adaptive immune system.

Kinetics of soluble tumour necrosis factor (TNF)-alpha receptors and cytokines in the early phase of treatment for chronic hepatitis C: comparison between interferon (IFN)-alpha alone, IFN-alpha plus amantadine or plus ribavirin

We have previously studied the effect of three different treatment regimens with interferon (IFN)-alpha alone or in combination with amantadine or ribavirin on viral kinetics in the first month of therapy. To understand the regulation of cytokine immune response during early inhibition of HCV replication, we analysed the longitudinal profile of proinflammatory markers (soluble TNFRs), of type 1 cytokines [IFN-gamma and interleukin (IL-12)], and of a type 2 cytokine (IL-10). Twenty-two chronic hepatitis C patients received daily therapy for 6 months. Sera were collected at baseline, at 6, 12, 24, 30 and 48 h and at the 3rd, 7th, 15th and 30th days of treatment. All cytokines and receptors were evaluated by enzyme linked immunosorbent assay (ELISA). At baseline, a correlation was found between the two soluble TNFRs (P < 0.0001) and between the soluble TNFRs and ALT levels (P < 0.003), as shown previously. Regardless of the type of treatment, lower levels of soluble TNFR-p75 were present from day 3 in patients who had significant virus decay at day 30 (P < 0.01). Baseline IL-10 levels correlated with TNFR-p75 (P < 0.01) and with treatment response (P < 0.05) and a significant IL-10 reduction from baseline was observed from day 3 among responders, irrespective of the type of treatments (P < 0.05). IL-12 and IFN-gamma levels did not differ according to treatment or outcome. These findings suggest a pivotal role for IL-10 in orchestrating the antiviral immune response. Its early decline can favour the shift from a Th2 to a Th1 immune response, which has been shown to be associated with a long-term virological response to treatment.

Hepatitis C virus

Hepatitis C virus is a common blood-borne pathogen that is now declining as a new infection in the population. However, women and men who were infected 2 to 3 decades ago are now developing liver damage. To prevent further damage, treatment with IFN and ribavirin is available. Because of adverse events, this treatment requires close supervision over 6 to 12 months, which is often provided by a clinic nurse in collaboration with the physician and pharmacist. Educational outreach to the public and health care providers may help identify patients earlier and promote screening of high-risk groups.

Hepatitis C virus infection in dialysis and chronic liver patients: Viraemia dependent anti-E2-antibody response

Cryptic hepatitis C virus (HCV) infection relates to patients infected chronically with HCV that are seronegative but have HCV-RNA. These patients are not identified by the standard serological tests for HCV, which are based on detection of antibodies to core, NS3 and NS5 antigens. They will, therefore, be wrongly diagnosed as non-infected, and are considered as a potential risk for others. Cryptic HCV infection in dialysis units occurs frequently and, due to medical procedures, is a major factor for contracting the virus when unrecognised. This study was conducted in order to assess the humoral immune responses to E2-antigen in sera of patients infected chronically with HCV. Recombinant E2 protein in enzyme linked immunosorbent assay (ELISA) and Western blot (WB) were used to test the occurrence of anti-E2 antibodies in the sera of patients from the liver clinic and of dialysis patients. The presence of E2 antibodies was found to be correlated with the presence of HCV-RNA and with viral load. Antibodies to the E2 protein could be detected in as many as 30% of the sera from dialysis patients with cryptic HCV infection (HCV-RNA only). The results suggest that detection of anti-E2 antibodies may enhance significantly HCV serological standard testing; especially among patients on dialysis, and that antibodies to envelope E2 protein appear to depend on and correlate with the presence of HCV particles.