T- and B-cell responses to different hepatitis C virus antigens in patients with chronic hepatitis C infection and in healthy anti-hepatitis C virus--positive blood donors without viremia

Immunoinformatic based designing of potential immunogenic novel mRNA and peptide-based prophylactic vaccines against H5N1 and H7N9 avian influenza viruses

Influenza viruses are the most common cause of serious respiratory illnesses worldwide and are responsible for a significant number of annual fatalities. Therefore, it is crucial to look for new immunogenic sites that might trigger an effective immune response. In the present study, bioinformatics tools were used to design mRNA and multiepitope-based vaccines against H5N1 and H7N9 subtypes of avian influenza viruses. Several Immunoinformatic tools were employed to extrapolate T and B lymphocyte epitopes of HA and NA proteins of both subtypes. The molecular docking approach was used to dock the selected HTL and CTL epitopes with the corresponding MHC molecules. Eight (8) CTL, four (4) HTL, and Six (6) linear B cell epitopes were chosen for the structural arrangement of mRNA and of peptide-based prophylactic vaccine designs. Different physicochemical characteristics of the selected epitopes fitted with suitable linkers were analyzed. High antigenic, non-toxic, and non-allergenic features of the designed vaccines were noted at a neutral physiological pH. Codon optimization tool was used to check the GC content and CAI value of constructed MEVC-Flu vaccine, which were recorded to be 50.42% and 0.97 respectively. the GC content and CAI value verify the stable expression of vaccine in pET28a + vector. In-silico immunological simulation the MEVC-Flu vaccine construct revealed a high level of immune responses. The molecular dynamics simulation and docking results confirmed the stable interaction of TLR-8 and MEVC-Flu vaccine. Based on these parameters, vaccine constructs can be regarded as an optimistic choice against H5N1 and H7N9 strains of the influenza virus. Further experimental testing of these prophylactic vaccine designs against pathogenic avian influenza strains may clarify their safety and efficacy.Communicated by Ramaswamy H. Sarma.

Impact of IL28 Genotypes and Modeling the Interactions of HCV Core Protein on Treatment of Hepatitis C

BACKGROUND

Mutations in the core CVR region of hepatitis C virus (HCV) and polymorphisms of interleukin 28B (IL28B) are associated with progression toward liver disease and in response to therapy. In addition, interactions of the core protein with some cell interactors can be related to HCV liver damage.

AIM

This study aimed to evaluate the effect of core mutations as well as IL28B polymorphism on clinical features, sustained virological response (SVR) in 1a and 3a HCV genotypes amongst Iranian HCV infected patients, and the impact of mutations on core protein properties, antigenic properties, and interactions with HCV inhibitors, using several bioinformatics tools.

METHODS

Seventy-nine Iranian patients infected with HCV genotypes 1a and 3a and diagnosed with chronic active hepatitis were examined. Plasma viral RNA was used to amplify and sequence the HCV Core gene; also, HCV viral load, molecular genotyping, and the liver enzymes were determined for all samples. The sequencing results were analyzed by several reliable bioinformatics tools to determine the physicochemical properties, B cell epitopes, post-modification changes, and secondary/tertiary structures; and evaluate the interactions with 4 drugs by docking method.

RESULT

There were some substitutions in core CVR related to ALT and AST enzymes that can lead to HCV advanced liver disease. The most prevalent mutation for 3a genotypes was a substitution in aa 162 (I to V) while we did not find any mutation in 1a responder group. Polymorphism of the rs8099917 showed that the majority of patients had TG heterozygous and carried CT genotype at the rs12979860. Analysis indicated several phosphorylation sits for core protein as well as two important disulfide bonds. Immunogenic prediction showed that core protein can strongly induce the immune system. Interaction analysis, using the docking method revealed two potential interactors (Vitronectin and SETD2).

CONCLUSION

Generally, mutations in all core CVR regions in all patients showed a relationship between such substitutions and higher liver enzymes that can result in advanced liver disease progression in HCV infected patients. Furthermore, immunoinformatics analysis determined the possible immunodominant regions to be considered in HCV vaccine designs. Furthermore, no association between SVR and IL28B polymorphism was shown. In silico analysis determined modification sites, structures, B-cell epitopes of core protein and interactions with several interactors can lead to persistent HCV infection in the cell and the progress of liver diseases.

Designing a novel mRNA vaccine against SARS-CoV-2: An immunoinformatics approach

SARS-CoV-2 is the deadly virus behind COVID-19, the disease that went on to ravage the world and caused the biggest pandemic 21st century has witnessed so far. On the face of ongoing death and destruction, the urgent need for the discovery of a vaccine against the virus is paramount. This study resorted to the emerging discipline of immunoinformatics in order to design a multi-epitope mRNA vaccine against the spike glycoprotein of SARS-CoV-2. Various immunoinformatics tools were utilized to predict T and B lymphocyte epitopes. The epitopes were channeled through a filtering pipeline comprised of antigenicity, toxicity, allergenicity, and cytokine inducibility evaluation with the goal of selecting epitopes capable of generating both T and B cell-mediated immune responses. Molecular docking simulation between the epitopes and their corresponding MHC molecules was carried out. 13 epitopes, a highly immunogenic adjuvant, elements for proper sub-cellular trafficking, a secretion booster, and appropriate linkers were combined for constructing the vaccine. The vaccine was found to be antigenic, almost neutral at physiological pH, non-toxic, non-allergenic, capable of generating a robust immune response and had a decent worldwide population coverage. Based on these parameters, this design can be considered a promising choice for a vaccine against SARS-CoV-2.

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SARS-CoV-2, the causative agent for COVID-19, has caused the biggest pandemic 21st century has witnessed so far.

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Here, immunoinformatics was used for designing a muti-epitope mRNA vaccine against the spike glycoprotein of SARS-CoV-2.

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Through stringent selection of T and B cell epitopes and other necessary elements, a vaccine was constructed in silico.

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Proposed mechanism of its synthesis, delivery and action has also been presented.

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The vaccine was found to be immunogenic, almost neutral, non-toxic, non-allergenic and has a decent worldwide coverage.

Bioinformatics Analysis of Domain 1 of HCV-Core Protein: Iran

Hepatitis C virus (HCV) infection is a serious global health problem and a cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). Bioinformatics software has been an effective tool to study the HCV genome as well as core domains. Our research was based on employing several bioinformatics software applications to find important mutations in domain 1 of core protein in Iranian HCV infected samples from 2006 to 2017, and an investigation of general properties, B-cell and T-cell epitopes, modification sites, and structure of domain 1. Domain 1 sequences of 188 HCV samples isolated from 2006 to 2017, Iran, were retrieved from NCBI gene bank. Using several tools, all sequences were analyzed for determination of mutations, physicochemical analysis, B-cell epitopes prediction, T-cell and CTL epitopes prediction, post modification, secondary and tertiary structure prediction. Our analysis determined several mutations in some special positions (70, 90, 91, and 110) that are associated with HCC and hepatocarcinogenesis, efficacy of triple therapy and sustained virological response, and interaction between core and CCR6. Several B-cell, T-cell, and CTL epitopes were recognized. Secondary and tertiary structures were mapped fordomain1 and core proteins. Our study, as a first report, offered inclusive data about frequent mutation in HCV-core gene domain 1 in Iranian sequences that can provide helpful analysis on structure and function of domain 1 of the core gene.

Hepatitis C virus infection induces endoplasmic reticulum stress and apoptosis in human fetal liver stem cells

The cellular mechanisms by which hepatitis C virus (HCV) replication might mediate cytopathic effects are controversial and not entirely clear. In this study, we found that blood-borne HCV (bbHCV) infection could lead to endoplasmic reticulum (ER)-stress and mitochondria-related/caspase-dependent apoptosis at the early stages of infection based on use of the highly efficient bbHCV cell culture model established previously. Sections of bbHCV-infected human fetal liver stem cells (hFLSCs) revealed convolution and nonlinear ER, cell vacuolization, swelling of mitochondria, and numerous double membrane vesicles (DMVs). The percentage of apoptotic hFLSCs infected by bbHCV reached 29.8% at 16 h postinfection, and the amount of cytochrome c increased remarkably in the cytosolic protein fraction. However, over time, apoptosis was inhibited due to the activation of NF-κB. The expression of NF-κB-p65, Bcl-xL, XIAP, and c-FLIPL in hFLSCs was increased significantly 24 h after in infection by bbHCV. The accelerated cell death cycles involving apoptosis, regeneration and repair by bbHCV infection might give rise to the development of cirrhosis, and ultimately to hepatocellular carcinogenesis. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

IL-1α correlates with severity of hepatitis C virus-related liver diseases

BACKGROUND AND AIMS

Immunoregulatory cytokines influence the persistence of hepatitis C virus (HCV) chronic infection and the extent of liver damage. Interleukin-1 (IL-1) plays an important role in the inflammatory process. Some studies have demonstrated that IL-1α production was impaired in patients with chronic infections of HCV, implying that IL-1α may play a role in viral clearance. The aim of this study was to evaluate the serum level of proinflammatory cytokine IL-1α in patients with chronic hepatitis C (CHC).

METHODS

This study was performed on 20 CHC patients with cirrhosis in (Group I), 20 CHC patients without cirrhosis in (Group II), 20 hepatocellular carcinoma (HCC) patients with positive anti-HCV in (Group III), and 10 healthy subjects as a control group. Serum levels of IL-1α were measured by enzyme-linked immunoassay technique.

RESULTS

IL-1α had the highest mean concentration in the HCC group and then in the group of CHC with cirrhosis compared to the group of CHC without cirrhosis. Also, it was higher in all studied groups than in the control group (P<0.001). Statistical analysis showed that IL-1α was positively correlated with bilirubin (P≤0.001), alanine aminotransferase (P=0.006), aspartate aminotransferase (P=0.001), and viral load (P=0.001) but it was negatively correlated with albumin (P≤0.001) and Hb (P≤0.001), and was not significantly correlated with other parameters (age, international normalized ratio, urea, creatinine, white blood cells, and platelet count).

CONCLUSION

Serum level of IL-1α was elevated in patients with CHC and its related liver diseases (liver cirrhosis and HCC) and can be used as an important parameter of inflammatory activity and for fibrosis evaluation in patients with chronic liver disease.

SEPPA 2.0--more refined server to predict spatial epitope considering species of immune host and subcellular localization of protein antigen

Spatial Epitope Prediction server for Protein Antigens (SEPPA) has received lots of feedback since being published in 2009. In this improved version, relative ASA preference of unit patch and consolidated amino acid index were added as further classification parameters in addition to unit-triangle propensity and clustering coefficient which were previously reported. Then logistic regression model was adopted instead of the previous simple additive one. Most importantly, subcellular localization of protein antigen and species of immune host were fully taken account to improve prediction. The result shows that AUC of 0.745 (5-fold cross-validation) is almost the baseline performance with no differentiation like all the other tools. Specifying subcellular localization of protein antigen and species of immune host will generally push the AUC up. Secretory protein immunized to mouse can push AUC to 0.823. In this version, the false positive rate has been largely decreased as well. As the first method which has considered the subcellular localization of protein antigen and species of immune host, SEPPA 2.0 shows obvious advantages over the other popular servers like SEPPA, PEPITO, DiscoTope-2, B-pred, Bpredictor and Epitopia in supporting more specific biological needs. SEPPA 2.0 can be accessed at http://badd.tongji.edu.cn/seppa/. Batch query is also supported.

Rapid early innate control of hepatitis C virus during IFN-α treatment compromises adaptive CD4+ T-cell immunity

The ability to control HCV with IFN-α-based treatments provides an opportunity in humans to study how the rate of viral clearance in vivo impinges on the development of antiviral responses. Ex vivo (IFN-γ-producing) and cultured antiviral CD4⁺ T cells, serum cytokines, and viral loads were measured repeatedly in a cohort of chronically HCV-infected subjects (n = 33) receiving IFN-α. Rapid control of virus indicated by an increased calculated rate of virus clearance, occurred in those subjects demonstrating absent/minimal T-cell responses (p < 0.0006). Surprisingly, in subjects who demonstrated the most robust T-cell responses (and reduced serum IL-10), there was actually a reduced rate of early virus clearance. A subsequent analysis of NK-cell function in available subjects (n = 8) revealed an inverse correlation between pretreatment NK-cell expression of NKp46 and the potential to upregulate cytotoxic function on exposure to IFN-α (p < 0.004), as well as the subsequent measured rate of viral clearance (p = 0.045). Thus, the CD4⁺ T-cell response during IFN-α treatment appears to be shaped by the rate of innate virus suppression. These data suggest that individuals who respond most effectively to immune intervention may be most in need of subsequent vaccination to prevent reinfection.

Characterization of virus-specific T-cell immunity in liver allograft recipients with HCV-induced cirrhosis

Recurrent hepatitis C infection (HCV) following liver transplantation causes accelerated allograft cirrhosis. Here we characterized HCV-specific immunity in adult liver transplant recipients (n = 74) with and without allograft cirrhosis. Patients were divided into hepatic inflammation/no cirrhosis (METAVIR scores 0-2, HIN) and hepatic cirrhosis (score 3-4, HFC). As control, 20 normal subjects and 10 non-HCV liver transplant patients were included. Twenty-five different serum cytokines were analyzed using LUMINEX. Frequency of T-cells specific to HCV-derived proteins (NS3, NS4, NS5, Core) was characterized using ELISPOT immunoassays. There was no difference in clinical characteristics between HIN (n = 49) and HFC (n = 25) groups. HIN group had high serum IFN-gamma and IL-12 while HFC demonstrated elevated IL-4, IL-5 and IL-10 (p < 0.01). HCV (NS3, NS4, NS5, Core)-specific IFN-gamma-producing CD4+ T-cells were elevated in the HIN group whereas the HFC patients showed predominance of HCV-specific IL-5 and IL-10-producing CD4+ T-cells.

CONCLUSIONS

Lack of HCV-specific Th1-type T-cell immunity is observed in liver transplant recipients with advanced allograft cirrhosis.

Does Fasciola hepatica infection modify the response of acute hepatitis C virus infection to IFN-alpha treatment?

Immunologic response to acute hepatitis C is mainly a Th1 response, whereas fasciolopsiasis is associated with a diverse T-cell response. Interferon-alpha has immunomodulatory effects and enhances Th1 immune response. Fasciola infection could theoretically interfere with the Th1 immune response, even when acquired after an initial response to interferon-alpha treatment for acute hepatitis C virus (HCV) infection. We report here the case of a male patient who acquired Fasciola hepatica infection after an initial response to IFN-alpha therapy with a favorable outcome.

New methods for detecting positive selection at single amino acid sites

Inferring positive selection at single amino acid sites is of particular importance for studying evolutionary mechanisms of a protein. For this purpose, Suzuki and Gojobori (1999) developed a method (SG method) for comparing the rates of synonymous and nonsynonymous substitutions at each codon site in a protein-coding nucleotide sequence, using ancestral codons at interior nodes of the phylogenetic tree as inferred by the maximum parsimony method. In the SG method, however, selective neutrality of nucleotide substitutions cannot be tested at codon sites, where only termination codons are inferred at any interior node or the number of equally parsimonious inferences of ancestral codons at all interior nodes exceeds 10,000. Here I present a modified SG method which is free from these problems. Specifically, I use the distance-based Bayesian method for inferring the single most likely ancestral codon from 61 sense codons at each interior node. In the computer simulation and real data analysis, the modified SG method showed a higher overall efficiency of detecting positive selection than the original SG method, particularly at highly polymorphic codon sites. These results indicate that the modified SG method is useful for inferring positive selection at codon sites where neutrality cannot be tested by the original SG method. I also discuss that the p-distance is preferable to the number of synonymous substitutions for inferring the phylogenetic tree in the SG method, and present a maximum likelihood method for detecting positive selection at single amino acid sites, which produced reasonable results in the real data analysis.

[Histopathologic and immunocytochemical changes in the liver in patients with chronic hepatitis C]

BACKGROUND

The presence of lymphocytes within the liver parenchyma is related to immunologically mediated liver damage in chronic hepatitis C. The aim of the study was to make histological, histochemical, and immunocytochemical assessment of liver biopsy specimens in patients with chronic hepatitis C virus (HCV) infection.

METHODS

Biopsy specimens of 20 patients with chronic HCV disease were analyzed, using standard staining procedures to verify histologic liver lesions, as well as immunoenzymatic staining with monoclonal antibodies to detect CD4+ T-lymphocytes, B-lymphocytes, and macrophages.

RESULTS

Micromorphologic characteristics of chronic active viral hepatitis C were present in all the patients, differing, however, by the level of their activity. Dominant changes were found within the portal space, consisting of mononuclear lympho-plasmocytic infiltration and macrophages. Immunocytochemical investigation of mononuclear and macrophageal infiltration showed the correlation between micromorphological findings and the degree of the activity.

CONCLUSION

The presence of lymphocytic and macrophageal infiltration within the hepatic tissue directly correlated with the intensity of the liver damage. Analysis of the population of cellular infiltrate in the liver together with the monitoring of viremia level and the level of hepatocyte necrosis, could be useful tools for elucidation of the pathogenesis of chronic hepatitis C.

Control of heterologous hepatitis C virus infection in chimpanzees is associated with the quality of vaccine-induced peripheral T-helper immune response

Prophylactic hepatitis C virus (HCV) vaccine trials with human volunteers are pending. There is an important need for immunological end points which correlate with vaccine efficacy and which do not involve invasive procedures, such as liver biopsies. By using a multicomponent DNA priming-protein boosting vaccine strategy, naïve chimpanzees were immunized against HCV structural proteins (core, E1, and E2) as well as a nonstructural (NS3) protein. Following immunization, exposure to the heterologous HCV 1b J4 subtype resulted in a peak of plasma viremia which was lower in both immunized animals. Compared to the naïve infection control and nine additional historical controls which became chronic, vaccinee 2 (Vac2) rapidly resolved the infection, while the other (Vac1) clearly controlled HCV infection. Immunization induced antibodies, peptide-specific gamma interferon (IFN-gamma), protein-specific lymphoproliferative responses, IFN-gamma, interleukin-2 (IL-2), and IL-4 T-helper responses in both vaccinees. However, the specificities were markedly different: Vac2 developed responses which were lower in magnitude than those of Vac1 but which were biased towards Th1-type cytokine responses for E1 and NS3. This proof-of-principle study in chimpanzees revealed that immunization with a combination of nonstructural and structural antigens elicited T-cell responses associated with an alteration of the course of infection. Our findings provide data to support the concept that the quality of the response to conserved epitopes and the specific nature of the peripheral T-helper immune response are likely pivotal factors influencing the control and clearance of HCV infection.

Evidence for lack of cross-genotype protection of CD4+ T cell responses during chronic hepatitis C virus infection

CD4+ T lymphocyte responses are thought to play a major role in control of the hepatitis C virus (HCV). Few, however, have been mapped down to the level of peptide and HLA restriction. Furthermore, the ability of such T cells to respond to viruses which differ in genotype has not been addressed in detail. In most cases of persistent infection with HCV, CD4 proliferative responses are weak or absent. From a large cohort of persistently infected patients, we identified an individual with unusually robust and persistent responses in the face of chronic infection. We firstly mapped two peptide epitopes to regions of the nonstructural protein NS4 (aa1686-1705 and aa 1746-1765). However, in contrast to the genotype 1a derived antigens used for mapping, the infecting virus was identified as genotype 3a. Strikingly, the patient's CD4 response to these epitopes were specific only for the genotype 1a sequence, and did not recognize genotype 3a synthetic peptides. Serologic assays indicated that prior exposure to HCV of genotype 1 had occurred. This patient therefore maintains strong CD4 proliferative responses which are genotype specific and not cross-reactive. The apparent 'misdirection' of these nonprotective responses has important implications for the role of natural and vaccine induced CD4 responses in the face of variable viruses.

Immunological markers predicting outcome in patients with hepatitis C treated with interferon-alpha and ribavirin

Type 1 (T1) cytokine responses are required for the clearance of hepatitis C virus by cytotoxic T lymphocytes, but can promote liver damage. Interferon-alpha (IFN alpha) can be expected to promote T1 cytokine responses, so treatment outcome may depend on the T1/T2 cytokine environment and levels of immune activation at baseline. This model was tested by monitoring immunological markers in a pilot study of treatment naïve patients given IFN alpha 2b and ribavirin, with the aim of finding markers that predict virological outcome. Soluble (s) CD26/dipeptidyl peptidase IV enzyme activity and levels of sCD30, bioavailable IL-6, sTNF-RI, IL-1ra and nitrite/nitrate (NO(2)(-)/NO(3)(-)) were measured. Levels of IL-1ra and bioavailable IL-6 were lower in patients than controls and did not change with therapy. Treatment decreased sCD26/dipeptidyl peptidase IV enzyme activities and sCD30 levels and increased NO(2)(-)/NO(3)(-) levels. High baseline sCD30 levels predicted an early (P = 0.008) and sustained (P = 0.03) virological response to therapy, suggesting treatment may be more effective in patients with a predominant T2 profile.

Interferon-alpha-2b plus ribavirin: a review of its use in the management of chronic hepatitis C

Relatively few patients (< or =20%) with chronic hepatitis C achieve a sustained virological response after interferon-alpha monotherapy. Hence, alternative treatment strategies such as the addition of the broad spectrum antiviral agent ribavirin to interferon-alpha-2b have been investigated. Combination therapy with subcutaneous interferon-alpha-2b [3 million units (MU) three times per week] plus oral ribavirin (1000 to 1200 mg/day) has proven effective in several well designed trials of 24 to 48 weeks' duration in adult patients with compensated chronic hepatitis C. Compared with interferon-alpha-2b (3 or 6 MU three times per week) with or without placebo, combination treatment with interferon-alpha-2b plus ribavirin significantly enhanced end-of-treatment and sustained virological and biochemical response rates in treatment-naive and treatment-experienced patients [sustained virological response rates in treatment-naive recipients (6 to 19% vs 31 to 43% of patients); sustained overall (virological plus biochemical) response rates in nonresponders to (1 vs 14%) or relapsers (4 to 5% vs 30 to 44%) after previous interferon-alpha monotherapy]. Forty-eight weeks of combination therapy was superior to 24 weeks in treatment-naive patients infected with hepatitis virus C (HCV) genotype 1, whereas response rates were similar at 24 and 48 weeks in those infected with other HCV genotypes. Furthermore, there were marked improvements in histological inflammatory scores in patients who responded to treatment with either interferon-alpha-2b plus ribavirin or interferon-alpha-2b alone. Although adverse events associated with either drug during combination therapy occurred frequently, these were generally mild to moderate in intensity and were consistent with those reported for each individual agent. Twenty-six percent of patients required dosage modifications of one or both drugs during combination therapy.

CONCLUSIONS

Interferon-alpha-2b plus ribavirin is an efficacious first- and second-line therapy in adult patients with compensated chronic hepatitis C, significantly improving sustained virological and biochemical responses versus interferon-alpha-2b monotherapy. The tolerability profile of interferon-alpha-2b plus ribavirin therapy is consistent with the individual profiles of these agents with no evidence of additive effects. The place of interferon-alpha-2b plus ribavirin combination therapy in relation to newer agents, including pegylated interferons-alpha and other multidrug regimens, remains to be determined in this rapidly evolving area of therapeutic management. Currently, combination therapy with interferon-alpha-2b plus ribavirin is recommended as first-line therapy for patients with chronic hepatitis C and compensated liver disease, and is an option for use as second-line therapy in those who have relapsed after, or failed to respond to, previous treatment with interferon-alpha.

Decreased frequency of the HLA-DRB1*11 allele in patients with chronic hepatitis C virus infection

A genetically determined resistance or susceptibility to chronic hepatitis C virus (HCV) infection may make an important contribution to the course of liver disease and may be linked to the human major histocompatibility complex (MHC). The aim of this study was to investigate the HLA class II genotype profile in chronic hepatitis C and to determine the HLA-hepatitis C association. The experimental population was composed of 49 unrelated chronic HCV patients (31 females, 18 males; mean age, 54.4 +/- 1.7 years; range, 34 to 73 years). The control population consisted of 43 ethnically matched healthy donors. HLA-DR and -DQ alleles were studied for patients and controls by a PCR-sequence-specific-primer low-resolution method. Anti-HCV was investigated with enzyme-linked immunosorbent assay II, and HCV RNA was investigated with reverse transcriptase nested PCR. The HLA class II allele, DRB1*11, was found at reduced frequency in 49 patients with chronic hepatitis C (anti-HCV and HCV RNA positive) compared to that for controls (22.4 versus 51.0%; P < 0.01, odds ratio = 0.3, confidence interval = 0.1 to 0.7). No further HLA associations with chronic HCV infection were observed, and there was no correlation between the stage of disease and HLA. DRB1*11 was also found at reduced frequency in all HCV antibody-positive patients compared to controls (corrected P = not significant). DRB1*11 was associated with chronic HCV infection, and it is possible that HLA-DRB1*11 may have a protective feature in chronic HCV infection. In addition, DRB1*11 was associated with protection from HCV infection. These findings suggest that host HLA class II genotype is an important factor determining the outcome of infection with HCV.

Immunopathogenesis of hepatitis C virus infection

Hepatitis C virus, a recently identified member of the family Flaviviridae, is an important cause of chronic viral hepatitis and cirrhosis. There are similarities in the nature of the immune response to this pathogen with immunity in other flavivirus and hepatotropic virus infections, such as hepatitis B. However, the high rate of viral persistence after primary hepatitis C infection, and the observation that neutralizing antibodies are not protective, would suggest that there are a number of important differences between hepatitis C, other flaviviruses, and hepatitis B. The phenomenon of quasispecies evolution and other viral factors have been proposed to contribute to immune evasion by hepatitis C virus. In the face of established persistent infection, virus-specific cytotoxic T lymphocytes may exert some control over viral replication. However, these same effectors may also be responsible for the progressive liver damage characteristic of chronic hepatitis C infection. The nature of protective immunity, including the role of innate immune responses early after hepatitis C exposure, remains to be defined.

Hepatitis C virus infection in patients with essential mixed cryoglobulinemia, multiple myeloma and chronic lymphocytic leukemia

Increased prevalence of HCV infection in some lymphoproliferative diseases has been recently reported. In the present study, the frequency of anti-HCV antibody (Ab) together with hepatitis B surface (HBs) antigen (Ag) and anti-HBs Ab were determined in 42, 45 and 23 patients with essential mixed cryoglobulinemia (EMC), multiple myeloma (MM) and B-cell chronic lymphocytic leukemia (B-CLL), respectively. Thirty hospitalized patients with chronic rheumatoid arthritis (RA) were also included as a control. Specific antibodies to HCV antigens were detected by enzyme linked immunosorbent assay (ELISA) and positive results were confirmed by a recombinant immunoblot assay (RIBA). Our results demonstrated anti-HCV positivity in 69%, 11% and 4.3% of the EMC, MM and B-CLL samples tested, respectively. None of the RA patients were found to be anti-HCV positive. No significant differences were observed between the patients groups regarding the frequency of HBs Ag and anti-HBs Ab. Considering the low incidence of HCV infection in the control group and the normal population, these results confirm and extend previous reports on the possible role of HCV infection in the etiology of EMC and further suggest involvement of this virus in a subset of MM.

Lipidation of T helper sequences from hepatitis C virus core significantly enhances T-cell activity in vitro

Successful elimination of the hepatitis C virus (HCV) during acute infection has been linked to strong HCV-specific in vitro T-cell proliferation, whereas T cells from patients with chronic hepatitis C respond only weakly to HCV antigens. Lipid-coupled peptides are immunostimulants, which might provide a basis for novel therapeutic strategies against HCV. Therefore, in 20 patients with chronic hepatitis C, we studied whether tri-palmitoyl-S-cysteine-coupled peptides could modify in vitro T-cell proliferation (by [3H]thymidine uptake) in response to virus core and NS4. The lipopeptides corresponded to five immunodominant T helper epitopes of HCV core. Contrary to unmodified peptides, the lipopeptides specifically enhanced [3H]thymidine uptake in response to HCV antigens but not to a non-HCV related control antigen. They increased the frequency of responders (stimulation index, SI > or = 4) to core (13/20 versus 2/20; p = 0.0008) and NS4 (20/20 versus 7/20; p < 0.0001) among our patients with chronic hepatitis C. This immunostimulatory effect was dose-dependent, and was observed specifically with lipopeptides corresponding to the HCV epitopes. Our data demonstrate that the poor in vitro T-cell proliferation of patients with chronic hepatitis C can be improved when T cells are co-stimulated with HCV core-derived T helper lipopeptides, while the same peptides in unlipidated form had no effects. Thus, lipopeptides corresponding to HCV T-cell epitopes may offer novel immunomodulatory strategies against HCV.

The ribavirin analog ICN 17261 demonstrates reduced toxicity and antiviral effects with retention of both immunomodulatory activity and reduction of hepatitis-induced serum alanine aminotransferase levels

The demonstrated utility of the nucleoside analog ribavirin in the treatment of certain viral diseases can be ascribed to its multiple distinct properties. These properties may vary in relative importance in differing viral disease conditions and include the direct inhibition of viral replication, the promotion of T-cell-mediated immune responses via an enhanced type 1 cytokine response, and a reduction of circulating alanine aminotransferase (ALT) levels associated with hepatic injury. Ribavirin also has certain known toxicities, including the induction of anemia upon chronic administration. To determine if all these properties are linked, we compared the D-nucleoside ribavirin to its L-enantiomer (ICN 17261) with regard to these properties. Strong similarities were seen for these two compounds with respect to induction of type 1 cytokine bias in vitro, enhancement of type 1 cytokine responses in vivo, and the reduction of serum ALT levels in a murine hepatitis model. In contrast, ICN 17261 had no in vitro antiviral activity against a panel of RNA and DNA viruses, while ribavirin exhibited its characteristic activity profile. Importantly, the preliminary in vivo toxicology profile of ICN 17261 is significantly more favorable than that of ribavirin. Administration of 180 mg of ICN 17261 per kg of body weight to rats by oral gavage for 4 weeks generated substantial serum levels of drug but no observable clinical pathology, whereas equivalent doses of ribavirin induced a significant anemia and leukopenia. Thus, structural modification of ribavirin can dissociate its immunomodulatory properties from its antiviral and toxicologic properties, resulting in a compound (ICN 17261) with interesting therapeutic potential.

Compositional bias and mimicry toward the nonself proteome in immunodominant T cell epitopes of self and nonself antigens

We investigated whether and how molecular mimicry affects the shaping of the helper T cell repertoire. We implemented an algorithm that measures the probability of mimicry between epitopes of known immunogenicity and self or nonself proteomes. This algorithm yields 'similarity profiles', which represent the probability of matching between all contiguous overlapping peptides of the antigen under examination and those in the proteome(s) considered. Similarity profiles between helper T cell epitopes (of self or microbial antigens and allergens) and human or microbial SWISSPROT collections were produced. For each antigen, both collections yielded largely overlapping profiles, demonstrating that self-nonself discrimination does not rely on qualitative features that distinguish human from microbial peptides. However, epitopes whose probability of mimicry with self or nonself prevails are, respectively, tolerated or immunodominant and coexist within the same (auto-)antigen regardless of its self/nonself nature. Epitopes (on self and nonself antigens) can cross-stimulate T cells at increasing potency as their similarity with nonself augments. Mimicry, rather than complicating self-nonself discrimination, assists in the shaping of the immune repertoire and helps define the defensive or autoreactive potential of a T cell. Being a predictor of epitope immunogenicity, it bears relevance to vaccine design.

Impaired Allostimulatory Capacity of Peripheral Blood Dendritic Cells Recovered from Hepatitis C Virus-Infected Individuals

In hepatitis C virus (HCV) infection, Th responses are implicated in the pathogenesis of liver disease. The dendritic cell (DC) is the most potent activator of CD4 T cells for supporting Th1 differentiation. To clarify the roles of DC of HCV-infected individuals in the development of CD4 T cell responses, we generated peripheral DC with GM-CSF and IL-4 from 24 chronic hepatitis C patients and 14 healthy donors. We then compared their potentials for stimulating allogeneic CD4 T cells, autologous CD4 T cells against influenza A or HCV core Ags, and cytokine production. The DC from the patients (HCV-DC) expressed lower degrees of CD86 than DC from the donors (N-DC), whereas no difference was found in the HLA molecules and other costimulators. HCV-DC stimulated allogeneic T cells less than N-DC; however, influenza A- or core-pulsed HCV-DC retained the potentials for autologous T cell proliferation. In allogeneic DC/T cell cultures, the IFN-γ levels with HCV-DC were lower than those with N-DC, which may be related to the low expressions of IL-12 p35 and p40 transcripts in HCV-DC. The stimulation with LPS disclosed that HCV-DC is less potent in IL-12 p70 production than N-DC. In the autologous cultures, the pulsing of the Ags to HCV-DC increased the IL-12 p40 and IFN-γ production and up-regulated the transcription of both IL-12 subunits. Exogenous IL-2 or IL-12 restored the low allogeneic T cell proliferation with HCV-DC in a dose-dependent manner. Therefore, low expression of CD86 and/or IL-12 is crucially involved in the low allostimulatory capacity of HCV-DC. Low IL-12 and low IFN-γ milieu with HCV-DC on encounters with alloantigens may impede Th1 polarization.

Acute hepatitis C virus structural gene sequences as predictors of persistent viremia: hypervariable region 1 as a decoy

We hypothesized that hepatitis C virus (HCV) persistence is related to the sequence variability of putative envelope genes. This hypothesis was tested by characterizing quasispecies in specimens collected every six months from a cohort of acutely HCV-infected subjects (mean duration of specimen collection, 72 months after seroconversion). We evaluated 5 individuals who spontaneously cleared viremia and 10 individuals with persistent viremia by cloning 33 1-kb amplicons that spanned E1 and the 5' half of E2, including hypervariable region 1 (HVR1). To assess the quasispecies complexity and to detect variants for sequencing, the first PCR-positive sample was examined by using a previously described method that combines heteroduplex analysis and analysis of single-stranded conformational polymorphisms. The ratio of nonsynonymous to synonymous substitutions (dN/dS) within each sample was evaluated as an indicator of relative selective pressure. Amino acid sequences were analyzed for signature patterns, glycosylation signals, and charge. Quasispecies complexity was higher and E1 dN/dS ratios (selective pressure) were lower in those with persistent viremia; the association with persistence was strengthened by the presence of a combination of both characteristics. In contrast, a trend toward higher HVR1 dN/dS ratios was detected among those with persistent viremia. We did not detect any such association for factors that may affect complexity such as serum HCV RNA concentration. HVR1 had a lower positive charge in subjects with persistent viremia, although no consistent motifs were detected. Our data suggest that HCV persistence is associated with a complex quasispecies and immune response to HVR1.