T-cell response relative to genotype and ethnicity during antiviral therapy for chronic hepatitis C

Reversal of T Cell Exhaustion in Chronic HCV Infection

The long-term consequences of T cell responses’ impairment in chronic HCV infection are not entirely characterized, although they may be essential in the context of the clinical course of infection, re-infection, treatment-mediated viral clearance and vaccine design. Furthermore, it is unclear whether a complete reinvigoration of HCV-specific T cell response may be feasible. In most studies, attempting to reverse the effects of compromised immune response quality by specific blockades of negative immune regulators, a restoration of functional competence of HCV-specific T cells was shown. This implies that HCV-induced immune dysfunction may be reversible. The advent of highly successful, direct-acting antiviral treatment (DAA) for chronic HCV infection instigated investigation whether the treatment-driven elimination of viral antigens restores T cell function. Most of studies demonstrated that DAA treatment may result in at least partial restoration of T cell immune function. They also suggest that a complete restoration comparable to that seen after spontaneous viral clearance may not be attained, pointing out that long-term antigenic stimulation imprints an irreversible change on the T cell compartment. Understanding the mechanisms of HCV-induced immune dysfunction and barriers to immune restoration following viral clearance is of utmost importance to diminish the possible long-term consequences of chronic HCV infection.

Modulation of Hepatitis C Virus-Specific CD8 Effector T-Cell Function with Antiviral Effect in Infectious Hepatitis C Virus Coculture Model

The antiviral effects of hepatitis C virus (HCV)-specific CD8 T cells have been shown in an HCV replicon system but not in an authentic infectious HCV cell culture (HCVcc) system. Here, we developed tools to examine the antigenicity of HCV-infected HLA-A2-positive Huh7.5 hepatoma cells (Huh7.5A2 cells) in activating HCV-specific CD8 T cells and the downstream antiviral effects. Infectious HCV epitope mutants encoding the well-defined genotype 1a-derived HLA-A2-restricted HCV NS3-1073 or NS5-2594 epitope were generated from a genotype 2a-derived HCV clone (Jc1Gluc2A) by site-directed mutagenesis. CD8 T-cell lines specific for NS3-1073 and NS5-2594 were expanded from HCV-seropositive persons by peptide stimulation in vitro or engineered from HCV-seronegative donor T cells by transduction of a lentiviral vector expressing HCV-specific T-cell receptors. HCV-specific CD8 T cells were cocultured with Huh7.5 cells that were pulsed with titrating doses of HCV epitope peptides or infected with HCV epitope mutants. HCV-specific CD8 T-cell activation (CD107a, gamma interferon, macrophage inflammatory protein 1β, tumor necrosis factor alpha) was dependent on the peptide concentrations and the relative percentages of HCV-infected Huh7.5A2 cells. HCV-infected Huh7.5A2 cells activated HCV-specific CD8 T cells at levels comparable to those achieved with 0.1 to 2 μM pulsed peptides, providing a novel estimate of the level at which endogenously processed HCV epitopes are presented on HCV-infected cells. While HCV-specific CD8 T-cell activation with cytolytic and antiviral effects was blunted by PD-L1 expression on HCV-infected Huh7.5A2 cells, resulting in the improved viability of Huh7.5A2 cells, PD-1 blockade reversed this effect, producing enhanced cytolytic elimination of HCV-infected Huh7.5A2 cells. Our findings, obtained using an infectious HCVcc system, show that the HCV-specific CD8 T-cell function is modulated by antigen expression levels, the percentage of HCV-infected cells, and the PD-1/PD-L1 pathways and has antiviral and cytotoxic effects.IMPORTANCE We developed several novel molecular and immunological tools to study the interactions among HCV, HCV-infected hepatocytes, and HCV-specific CD8 T cells. Using these tools, we show the level at which HCV-infected hepatoma cells present endogenously processed HCV epitopes to HCV-specific CD8 T cells with antiviral and cytotoxic effects. We also show the marked protective effect of PD-L1 expression on HCV-infected hepatoma cells against HCV-specific CD8 T cells.

Hepatitis B Virus--Specific and Global T-Cell Dysfunction in Chronic Hepatitis B

BACKGROUND & AIMS

T cells play a critical role in viral infection. We examined whether T-cell effector and regulatory responses can define clinical stages of chronic hepatitis B (CHB).

METHODS

We enrolled 200 adults with CHB who participated in the National Institutes of Health-supported Hepatitis B Research Network from 2011 through 2013 and 20 uninfected individuals (controls). Peripheral blood lymphocytes from these subjects were analyzed for T-cell responses (proliferation and production of interferon gamma and interleukin 10) to overlapping hepatitis B virus (HBV) peptides (preS, S, preC, core, and reverse transcriptase), influenza matrix peptides, and lipopolysaccharide. T-cell expression of regulatory markers FOXP3, programmed death-1, and cytotoxic T lymphocyte-associated antigen-4 was examined by flow cytometry. Immune measures were compared with clinical parameters, including physician-defined immune-active, immune-tolerant, or inactive CHB phenotypes, in a blinded fashion.

RESULTS

Compared with controls, patients with CHB had weak T-cell proliferative, interferon gamma, and interleukin 10 responses to HBV, with increased frequency of circulating FOXP3(+)CD127(-) regulatory T cells and CD4(+) T-cell expression of programmed death-1 and cytotoxic T lymphocyte-associated antigen-4. T-cell measures did not clearly distinguish between clinical CHB phenotypes, although the HBV core-specific T-cell response was weaker in hepatitis B e antigen (HBeAg)(+) than HBeAg(-) patients (percent responders: 3% vs 23%; P = .00008). Although in vitro blockade of programmed death-1 or cytotoxic T lymphocyte-associated antigen-4 increased T-cell responses to HBV, the effect was weaker in HBeAg(+) than HBeAg(-) patients. Furthermore, T-cell responses to influenza and lipopolysaccharide were weaker in CHB patients than controls.

CONCLUSIONS

HBV persists with virus-specific and global T-cell dysfunction mediated by multiple regulatory mechanisms, including circulating HBeAg, but without distinct T-cell-based immune signatures for clinical phenotypes. These findings suggest additional T-cell-independent or regulatory mechanisms of CHB pathogenesis that warrant further investigation.

Characterization of hepatitis C virus genotypes by direct sequencing of HCV 5'UTR region of isolates from Saudi Arabia

The current study was designed to determine the Hepatitis C Virus (HCV) genotypes in a representative sample of HCV chronically infected patients in Saudi Arabia. All HCV isolates were genotyped by sequencing of the 5′UTR region and newly identified HCV isolates were identified. Specific universal primers targeting 5′UTR region were used for both amplification and sequencing of all isolates that resulted in 244 bp fragment which represent about 80% of 5′UTR region. Most of HCV isolates in this study were genotype 4 (76.4%) where only few isolates were recognized as genotype 1 (19.6%). All results were compared to HCV reference sequences from LOS ALAMOS HCV database, considering only the complete full genomes for the main phylogenetic analysis. Sequences that showed maximum identity (98% –100%) were selected. Most isolates were identical with HCV genotype 4 references. Some isolates were similar to different subtypes of HCV genotypes 4, 1 and 6. Phylogenetic analysis showed resemblance of most isolates to similar ones from the Far East, North America and Egypt. Using sequence Weblogo, Alignment analysis of isolated HCV genotypes 4 and 1 showed 92% and 95.5% nucleotide conservation, respectively. There was no predominant nucleotide in the varied sites, in both genotypes. All isolated sequences were submitted to GenBank database.

Peripheral CD27-CD21- B-cells represent an exhausted lymphocyte population in hepatitis C cirrhosis

Hepatitis C cirrhosis is associated with a profound disappearance of memory B-cells. We sought to determine if this loss is associated with the expansion of the CD27(-)CD21(-) tissue-like memory B-cells with features of B-cell exhaustion. To this end, we quantified the frequency of CD27(-)CD21(-) B-cells in healthy, non-cirrhotic HCV-infected, and cirrhotic patients. We examined the expression of putative inhibitory receptors, the proliferative and immunoglobulin-secreting capacity of CD27/CD21-defined B-cell subsets upon B-cell receptor and/or CD40 stimulation. We found that CD27(-)CD21(-) B-cells are significantly increased in frequency relative to healthy donors in HCV-infected patients. CD27(-)CD21(-) B-cells were hypoproliferative relative to naïve and resting memory B-cells upon agonistic stimulation, but retained similar capacity for antibody secretion.

CONCLUSION

CD27(-)CD21(-) tissue-like memory B-cells with exhausted proliferation circulate at increased frequency in cirrhotic and non-cirrhotic HCV-infected patients. This B-cell subset does not appear anergic, exhibiting immunoglobulin-secreting capacity on CD40 agonism indistinguishable from other CD27/CD21-defined B-cell subsets.

Impact of oral silymarin on virus- and non-virus-specific T-cell responses in chronic hepatitis C infection

Silymarin displays anti-inflammatory effects on T lymphocytes in vitro. The immunomodulatory properties of oral silymarin in vivo in humans with chronic hepatitis C have not previously been characterized. We hypothesized that silymarin would suppress T-cell proliferation and pro-inflammatory cytokine production of virus- and non-virus-specific T cells while increasing anti-inflammatory IL-10 production in vivo. Patients from one site of the SyNCH-HCV double-masked, placebo-controlled study of oral silymarin in prior interferon nonresponders with chronic hepatitis C provided blood samples at baseline and treatment week 20. Mononuclear cells were stimulated with recombinant HCV proteins and controls in (3) H-thymidine proliferation assays, IFNγ ELISPOT and IL-10 ELISPOT. The frequency of CD4(+) CD25(hi) and CD4(+) foxp3(+) regulatory T cells, serum cytokine levels, serum IP-10 and lymphocyte interferon-stimulated gene expression were also quantified at baseline and week 20. Thirty-two patients were recruited (10; placebo, 11; 420 mg three times a day, 11; 700 mg three times a day). Serum ALT and HCV RNA titres did not change in any group. HCV-specific CD4(+) T-cell proliferation and the frequency of IFNγ- and IL-10-producing T cells were not significantly changed in silymarin-treated subjects. However, C. albicans-induced T-cell IFNγ and phytohaemagglutinin-induced T-cell proliferation were suppressed by silymarin therapy. A trend towards augmentation of interferon-induced ISG15 expression was present in the high-dose silymarin group. While no effect on HCV-specific T cells was identified, these data confirm that high-dose oral silymarin exerts modest nonspecific immunomodulatory effects in vivo. The impact of this anti-inflammatory effect on long-term liver health in chronic hepatitis C merits future clinical investigation.

Endogenous hepatitis C virus homolog fragments in European rabbit and hare genomes replicate in cell culture

Endogenous retroviruses, non-retroviral RNA viruses and DNA viruses have been found in the mammalian genomes. The origin of Hepatitis C virus (HCV), the major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma in humans, remains unclear since its discovery. Here we show that fragments homologous to HCV structural and non-structural (NS) proteins present in the European rabbit (Oryctolagus cuniculus) and hare (Lepus europaeus) genomes replicate in bovine cell cultures. The HCV genomic homolog fragments were demonstrated by RT-PCR, PCR, mass spectrometry, and replication in bovine cell cultures by immunofluorescence assay (IFA) and immunogold electron microscopy (IEM) using specific MAbs for HCV NS3, NS4A, and NS5 proteins. These findings may lead to novel research approaches on the HCV origin, genesis, evolution and diversity.

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.

Antigen-specific T lymphocyte proliferation decreases over time in advanced chronic hepatitis C

To evaluate T cell immunity in advanced liver disease, antigen-specific lymphoproliferative (LP) responses were prospectively studied in the context of the Hepatitis C Antiviral Long-term Treatment against Cirrhosis trial. Peripheral blood responses to hepatitis C virus (HCV), tetanus and Candida protein antigens were measured at baseline, month 12 (M12), M24, M36 and M48 in 186 patients randomized to either low-dose peginterferon-alfa-2a (PEG-IFN) only or observation. Liver histology was evaluated at baseline, M24 and M48. Patients with cirrhosis (Ishak 5-6) were less likely to have positive LP responses to HCV at baseline than patients with fibrosis (15%vs 29%, P = 0.03) and had lower levels of HCV c100 responses at baseline, M24 and M48 (P = 0.11, P = 0.05, P = 0.02, respectively). For 97 patients with complete longitudinal data, the frequency of positive LP responses to HCV, tetanus and Candida antigens declined over time (P < 0.003), and the slope of this decline was greater in the PEG-IFN treatment group than the observation group (P < 0.02). Lower levels of tetanus LP responses were associated with fibrosis progression and clinical outcomes (P = 0.009). Poorer CD4+ T cell proliferative function was associated with more advanced liver disease in chronic hepatitis C and may be further affected by long-term PEG-IFN treatment.

Different aspects of CD4 T cells that lead to viral clearance or persistence of HCV infection

More than 170 million people worldwide are infected with hepatitis C virus (HCV). A characteristic of this virus is a high tendency toward chronic infection. Several factors affect the viral outcome after infection. Among them, HCV-specific CD4 T cells are thought to play a crucial role in controlling viremia. Cumulative data showed that spontaneously resolved individuals have vigorous CD4 T-cell responses to a broad spectrum of HCV antigens and maintain these responses over a long period of time, whereas chronically infected patients lose their CD4 T-cell responses in the acute phase of infection. Although several possibilities of why CD4 T cells lose their function have been proposed, the mechanisms are not completely understood. Moreover, there is another subset of CD4 T cells called regulatory T cells (Tregs). These cells suppress immune reaction of T cells, B cells, and antigen-presenting cells, and are thought to protect organs from immune overreaction and autoimmunity. An increasing amount of data supports the possibility that Tregs participate in the mechanism of HCV persistence. It is obvious that CD4 T cells are the main effectors controlling HCV outcome. To achieve a better prognosis, we need to understand the mechanism of how HCV earns its chronicity by escaping from host cellular immune attacks. In this review, we will focus on the role of HCV-specific T cells in controlling viremia, particularly the aspects of these cells being either inhibitors or propellers of chronic infection.

Amino acid substitution in HCV core/NS5A region and genetic variation near IL28B gene affect treatment efficacy to interferon plus ribavirin combination therapy

OBJECTIVE

To evaluate predictive factors of treatment efficacy to interferon (IFN)/ribavirin in patients infected with HCV genotype 1b (HCV-1b).

METHODS

This study investigated pretreatment predictors, including viral- (aa substitutions in core aa 70/91 and NS5A-ISDR/IRRDR) and host-related factors (genetic variation near IL28B gene), to 48-week IFN/ribavirin in 490 Japanese adults infected with HCV-1b.

RESULTS

The proportion of patients who showed end-of-treatment response (ETR), sustained virological response (SVR), and SVR after ETR was 76, 54, and 76%, respectively. There was a significant positive correlation between the number of aa substitutions in ISDR and those in IRRDR. Concerning the substitution of core aa 91, the number of aa substitutions in ISDR/IRRDR of patients with Leu91 was significantly higher than that of patients with Met91. Furthermore, levels of viremia were influenced by aa substitutions in core aa 91 and ISDR/IRRDR. By multivariate analysis, rs8099917 genotype was an important predictor of ETR and SVR. With regard to viral factors, core aa 70/91 was an important predictor of ETR, and SVR after ETR. ISDR was an important predictor of SVR, and SVR after ETR.

CONCLUSION

aa substitution in core/NS5A region and genetic variation near IL28B were important predictors of treatment efficacy to IFN/ribavirin.

CD154, a marker of antigen-specific stimulation of CD4 T cells, is associated with response to treatment in patients with chronic HCV infection

CD4 T-cell function is crucial for the eradication of HCV, and insufficient function is observed in chronic carriers. The monitoring of T-cell responses is complicated by the scarcity of antigen-specific T cells and the relative inefficiency of virus-specific T cells to produce effector cytokines. CD154 is a marker of activation expressed on T cells induced through their T-cell receptor. We analysed CD4 T-cell responses in 72 patients with chronic or resolved HCV infection (23 treatment naïve, 49 treatment experienced, including 16 who had achieved a sustained response). In an additional prospective protocol, 20 of the chronically infected patients were analysed before and after 8-12 weeks of combination therapy with peg-interferon-α and ribavirin. T-cell responses were measured by detecting the expression of CD154 and Th1 cytokines after stimulation with recombinant HCV proteins and were correlated with pretreatment status and outcome of therapy. Broader T-cell responses were observed in treatment naïve than in experienced patients, while the outcome of a preceding therapy regimen did not influence T-cell responses. In the prospective cohort, an on-treatment increase in CD154+ cytokine- T-cell activity was associated with response to treatment, while a decrease was observed in nonresponders. Stronger antigen-independent activity of CD154+ cytokine+ T cells was observed in responders than in nonresponders. Our data indicate that CD154 as a marker of activation of CD4 T cells is a suitable tool for the analysis of T-cell responses in patients with HCV infection.

Hepatitis B immunology for clinicians

Hepatitis B virus (HBV) is a hepatotrophic DNA virus that causes acute and chronic hepatitis. Despite an effective vaccine, more than 350 million people are chronically infected with HBV worldwide and are at risk for progressive liver disease. There are marked geographic variations in HBV prevalence (ranging from 0.1% to 2% in low prevalence areas and 10% to 20% in high prevalence areas) related to the timing and mode of HBV exposure. In many developed countries, HBV exposure typically occurs in adults via sexual transmission with a low chronicity rate (5%). In regions with high HBV prevalence (eg, Asia, sub-Saharan Africa), HBV exposure tends to occur in the perinatal period (eg, vertical transmission from mother to infant) with a high rate of persistence in the absence of timely vaccination. The course of viral infection is defined by the interplay between the virus and host immune defense. This article introduces the innate and adaptive immune defense mechanisms in general and as related to HBV. In particular, the current concepts regarding the innate and adaptive immune components contributing to the clinical, virologic and therapeutic outcome in acute and chronic hepatitis B are examined.

T-cell responses at baseline and during therapy with peginterferon-alpha and ribavirin are not associated with outcome in chronic hepatitis C infected patients

BACKGROUND

Since the association between hepatitis C virus (HCV)-specific T-cell responses both pre-treatment and during interferon-alpha based therapy and viral clearance is unresolved, a combined analysis of distinctive T-cell characteristics (proliferation and interferon-gamma production) is important to clarify this issue.

METHODS

Peripheral blood mononuclear cells (PBMC) collected in 22 chronic HCV infected patients at pre-treatment and at week 4 during pegIFN-alpha/ribavirin therapy, were stimulated with overlapping peptide pools in a [3H]-thymidine assay, an interferon-gamma-ELISA, and a sensitive 12-day T-cell expansion assay.

RESULTS

Compared to the [3H]-thymidine proliferation and interferon-gamma secretion assays, the 12-day T-cell expansion assay was more sensitive in detecting T-cell responses. No significant association was demonstrated between pre-treatment HCV-specific CD4+ or CD8+ T-cell responses and either a sustained virological response (SVR) or a rapid virological response (RVR). However, a skewing of individual responses towards the non-structural antigens was observed. During pegIFN-alpha/ribavirin therapy, HCV-specific CD4+ and CD8+ T-cells declined similarly in both SVR/RVR and non-SVR/non-RVR patients.

CONCLUSION

No correlation was found between the magnitude of pre-treatment HCV-specific T-cell responses and the outcome of pegIFN-alpha/ribavirin therapy in terms of SVR and RVR. Moreover, the magnitude of HCV-specific T-cell responses declined in all patients early during treatment.

Early gene expression profiles of patients with chronic hepatitis C treated with pegylated interferon-alfa and ribavirin

Responsiveness to hepatitis C virus (HCV) therapy depends on viral and host factors. Our aim was to assess sustained virologic response (SVR)-associated early gene expression in patients with HCV receiving pegylated interferon-alpha2a (PEG-IFN-alpha2a) or PEG-IFN-alpha2b and ribavirin with the duration based on genotypes. Blood samples were collected into PAXgene tubes prior to treatment as well as 1, 7, 28, and 56 days after treatment. From the peripheral blood cells, total RNA was extracted, quantified, and used for one-step reverse transcription polymerase chain reaction to profile 154 messenger RNAs. Expression levels of messenger RNAs were normalized with six "housekeeping" genes and a reference RNA. Multiple regression and stepwise selection were performed to assess differences in gene expression at different time points, and predictive performance was evaluated for each model. A total of 68 patients were enrolled in the study and treated with combination therapy. The results of gene expression showed that SVR could be predicted by the gene expression of signal transducer and activator of transcription-6 (STAT-6) and suppressor of cytokine signaling-1 in the pretreatment samples. After 24 hours, SVR was predicted by the expression of interferon-dependent genes, and this dependence continued to be prominent throughout the treatment.

CONCLUSION

Early gene expression during anti-HCV therapy may elucidate important molecular pathways that may be influencing the probability of achieving virologic response.

Immune suppression leading to hepatitis C virus re-emergence after sustained virological response

Sustained virological response SVR is defined as undetectable HCV RNA in plasma 6 months after therapy has been discontinued. Relapse or re-emergence of viremia after SVR is rare. We report two patients that relapsed when immune suppressive therapy was given within a few weeks of achieving SVR. Patient 1 received prednisone for bronchitis and patient 2 relapsed soon after immune suppression was started post renal transplantation. These data suggest that the early phase of SVR might be associated with incomplete protective immunity. They suggest that sterilizing immunity with complete elimination of virus is unlikely. The cases also caution against the use of immune suppressive therapy in the immediate aftermath of SVR.

Polymorphism in the human major histocompatibility complex and early viral decline during treatment of chronic hepatitis C

The dynamics of the viral decline immediately after the start of therapy for chronic hepatitis C virus (HCV) infection may have prognostic potential for ultimate sustained virologic response. Considerable interindividual variability in the decline has been reported, including differences by race. The human major histocompatability complex (MHC) genes encode the human leukocyte antigens, which are important in the immune response to viral infections. We examined whether carriage of specific human MHC alleles are associated with the rate of the early viral decline. Longitudinal viral level data (baseline and days 1, 2, 7, 14, and 28 of treatment), medium resolution MHC genotyping, and random coefficients models were used to examine associations between MHC class I and class II allele carriage and the dynamics of the viral decline in 180 African-Americans (AAs) and 194 Caucasian Americans (CAs) with genotype-1 HCV infection over the first 28 days of treatment with peginterferon alpha2a plus ribavirin. Baseline viral levels were similar by race, irrespective of allele carriage. However, the rate of change in the viral decline was associated with both allele and race. Among the four subgroups defined by race and specific allele, the fastest rates of decline were observed (in terms of estimated mean viral declines log(10) IU/ml during the first four weeks) in CA noncarriers for A*03 (2.75; P = 0.018), in CA carriers for Cw*03 (2.99; P = 0.046), and in CA noncarriers for DQA1*04 (2.66; P = 0.018) or DQB1*0402 (2.65; P = 0.018). MHC alleles are associated with the viral decline during the first 28 days of peginterferon therapy.

Molecular characterization of genotype 2 and 4 hepatitis C virus isolates in French blood donors

The subtype distribution of 142 genotype 2 and 97 genotype 4 hepatitis C virus (HCV) isolates from the sera of 1,319 volunteer blood donors in France was determined by gene sequencing and by phylogenetic analysis of the NS5B region and E1 envelope. Findings underlined a wide range of subtypes in both genotypes, that is, 20 in HCV-2 and 11 in HCV-4. Eighteen of these 31 subtypes had not been defined previously. Some subtypes, that is, 2a, 2b, 2c, 2i, 2k, 4a, and 4d, showed numerous strains while subtypes in donors from West Africa or Central Africa showed an endemic profile with only a few strains. A Bayesian coalescence approach was used to estimate the demographic history of each HCV subtype. The estimated mean dates of the most recent common ancestors (MRCA) were 1,889 (confidence interval (CI), 1,842-1,930) for HCV-2a, 1,886 (CI, 1,843-1,921) for HCV-2b, 1,791 (CI, 1,699-1,848) for HCV-2c, 1,846 (CI, 1,803-1,878) for HCV-2i, 1,911 (CI, 1,879-1,937) for HCV-4a, and 1,957 (CI, 1,943-1,967) for HCV-4d. The period of spread for subtype 2b, 2c, and 2i was between 1900 and 1960 whereas rapid exponential spread for subtype 2a, 4a, and 4d occurred in the 1960s. The inferred histories of population growth indicated that transmission rates differed according to HCV subtype. These results may help to predict the future burden of HCV in France.

Prospective analysis of effector and regulatory CD4+ T cells in chronic HCV patients undergoing combination antiviral therapy

BACKGROUND/AIMS

The role of HCV-specific CD4(+) T cells and regulatory T cells in influencing the outcome of antiviral therapy is incompletely defined.

METHODS

CD4(+) IFN-gamma ELISPOT assays (n=58) and flow cytometric analysis of FoxP3-expressing T regulatory cells (n=62) were performed on patients from the Virahep-C study at baseline, during and after cessation of antiviral therapy.

RESULTS

Total HCV-specific IFN-gamma CD4(+) T cell ELISPOT responses did not increase with therapy, but rather decreased by 8 weeks and remained below baseline 24 weeks after cessation of therapy. There were no statistically significant differences with respect to viral kinetics, race and virologic outcome. In contrast, viral relapse after treatment was associated with a three-fold increase in HCV-specific responses. The frequency and phenotype of regulatory T cells during therapy were not significantly different in terms of race, viral kinetic groups or virologic outcome.

CONCLUSIONS

A contraction of HCV-specific CD4(+) T cell responses was found during treatment with recovery of responses in patients experiencing virologic relapse after treatment. The levels of FoxP3-expressing regulatory T cells did not vary by race and were not predictive of virologic outcome. Work is ongoing to explore the contribution of mechanisms independent of CD4(+) T cells in therapy-induced viral clearance.

Sustained response to interferon-alpha plus ribavirin therapy for chronic hepatitis C is closely associated with increased dynamism of intrahepatic natural killer and natural killer T cells

AIM

Previous studies have revealed that functional impairment of innate immune cells, including natural killer (NK) and natural killer T (NKT) cells, might be associated with the persistence of hepatitis C virus (HCV) infection. However, the involvement of innate immune cells, which predominate in the liver, in therapeutic HCV clearance is still unclear.

METHODS

To clarify the role of intrahepatic innate immune cells in the clinical outcome of patients with chronic hepatitis C (CHC) treated with interferon-alpha plus ribavirin (IFN/RBV), we prospectively investigated the status of NK and NKT cells in paired liver biopsy and peripheral blood (PB) samples obtained from 21 CHC patients before and immediately after IFN/RBV treatment by flow cytometry. Normal liver and PB samples were obtained from 10 healthy donors for living donor liver transplantation.

RESULTS

Before treatment, intrahepatic NK and NKT cells constituted a significantly lower proportion in CHC patients than in healthy individuals (P < 0.05). After IFN/RBV treatment, the proportions and absolute numbers of CD3(-)CD161(+) NK and CD3(+)CD56(+) NKT cells in the liver, but not in PB, were significantly increased in sustained responders (SR) as compared with poor responders (P < 0.05). The proportion of CD3(+)CD161(+) NKT cells was also increased in the liver of SR after the treatment. Moreover, there was a striking increase of activated CD152(+) cells among CD3(+)CD56(+) NKT cells in the liver of SR (P = 0.041).

CONCLUSION

These findings demonstrate that sustained response to IFN/RBV treatment for patients with CHC is closely associated with increased dynamism of NK and NKT cells in the liver.

Functional restoration of HCV-specific CD8 T cells by PD-1 blockade is defined by PD-1 expression and compartmentalization

BACKGROUND & AIMS

The immunoinhibitory receptor programmed death-1 (PD-1) is up-regulated on dysfunctional virus-specific CD8 T cells during chronic viral infections, and blockade of PD-1/PD-ligand (PD-L) interactions can restore their function. As hepatitis C virus (HCV) persists in the liver with immune-mediated disease pathogenesis, we examined the role of PD-1/PD-L pathway in antigen-specific CD8 T-cell dysfunction in the liver and blood of HCV-infected patients.

METHODS

PD-1 expression and function of circulating CD8 T cells specific for HCV, Epstein-Barr virus, and influenza virus were examined ex vivo and following antigenic stimulation in vitro in patients with acute, chronic, and resolved HCV infection using class I tetramers and flow cytometry. Intrahepatic CD8 T cells were examined from liver explants of chronically HCV-infected transplant recipients.

RESULTS

Intrahepatic HCV-specific CD8 T cells from chronically HCV-infected patients were highly PD-1 positive, profoundly dysfunctional, and unexpectedly refractory to PD-1/PD-L blockade, contrasting from circulating PD-1-intermediate HCV-specific CD8 T cells with responsiveness to PD-1/PD-L blockade. This intrahepatic functional impairment was HCV-specific and directly associated with the level of PD-1 expression. Highly PD-1-positive intrahepatic CD8 T cells were more phenotypically exhausted with increased cytotoxic T-lymphocyte antigen 4 and reduced CD28 and CD127 expression, suggesting that active antigen-specific stimulation in the liver induces a profound functional exhaustion not reversible by PD-1/PD-L blockade alone.

CONCLUSIONS

HCV-specific CD8 T-cell dysfunction and responsiveness to PD-1/PD-L blockade are defined by their PD-1 expression and compartmentalization. These findings provide new and clinically relevant insight to differential antigen-specific CD8 T-cell exhaustion and their functional restoration.

Identification and in vitro expansion of functional antigen-specific CD25+ FoxP3+ regulatory T cells in hepatitis C virus infection

CD4(+)CD25(+) regulatory T cells (CD25(+) Tregs) play a key role in immune regulation. Since hepatitis C virus (HCV) persists with increased circulating CD4(+)CD25(+) T cells and virus-specific effector T-cell dysfunction, we asked if CD4(+)CD25(+) T cells in HCV-infected individuals are similar to natural Tregs in uninfected individuals and if they include HCV-specific Tregs using the specific Treg marker FoxP3 at the single-cell level. We report that HCV-infected patients display increased circulating FoxP3(+) Tregs that are phenotypically and functionally indistinguishable from FoxP3(+) Tregs in uninfected subjects. Furthermore, HCV-specific FoxP3(+) Tregs were detected in HCV-seropositive persons with antigen-specific expansion, major histocompatibility complex class II/peptide tetramer binding affinity, and preferential suppression of HCV-specific CD8 T cells. Transforming growth factor beta contributed to antigen-specific Treg expansion in vitro, suggesting that it may contribute to antigen-specific Treg expansion in vivo. Interestingly, FoxP3 expression was also detected in influenza virus-specific CD4 T cells. In conclusion, functionally active and virus-specific FoxP3(+) Tregs are induced in HCV infection, thus providing targeted immune regulation in vivo. Detection of FoxP3 expression in non-HCV-specific CD4 T cells suggests that immune regulation through antigen-specific Treg induction extends beyond HCV.

Predictors of viral kinetics to peginterferon plus ribavirin combination therapy in Japanese patients infected with hepatitis C virus genotype 1b

For chronic hepatitis C virus (HCV) infection, evaluation of response to peginterferon (PEG-IFN) plus ribavirin (RBV) therapy based on viral kinetics is useful as an early predictor of treatment efficacy, but the underlying mechanisms of the different viral kinetics to treatment are still unclear. The response to 48-week PEG-IFN-RBV combination therapy was evaluated in 160 Japanese adult patients infected with HCV genotype 1b and determined the rapid virological response (at 4 weeks), early virological response (at 12 weeks), end-of treatment response, and sustained virological response (6 months after end of treatment). The proportion of patients who showed rapid, early and sustained virological, and end-of treatment responses were 50%, 73%, 47%, and 71%, respectively. Furthermore, 66% of patients who achieved early virological response also showed sustained virological response. Multivariate analysis identified substitutions of amino acid (aa) 70 and 91 in the HCV core region (double-wild-type) as a predictor of early HCV-RNA negativity, rapid, early, and sustained virological responses and end-of treatment response, and lipid metabolic factors (high levels of LDL cholesterol and total cholesterol) as predictors of early and rapid virological responses and end-of treatment response. Male sex and low levels of alpha-fetoprotein were other predictors of sustained virological response. Furthermore, female sex and severity of liver fibrosis were determinants of lack of sustained virological response in spite of early virological response. This study identified predictors of efficacy of PEG-IFN-RBV therapy based on viral kinetics in Japanese patients infected with HCV genotype 1b.

[Adaptive cell immune response against the hepatitis C virus infection]

Hepatitis C virus (HCV) infects around 175 million people worldwide and is one of the leading causes of chronic liver disease. Less than one third of patients infected with HCV are able to spontaneously clear the virus during acute infection, while most patients evolve to chronic infection. Control of viral replication has been associated to the cellular component of the host immune response. It is not fully understood what distinguish a successful cellular immune response. An integral interpretation of the numerous experimental findings may allow a better understanding of the immune mechanisms involved in the inability of the immune system to successfully control chronic HCV infection.

HCV-specific T-cell response in relation to viral kinetics and treatment outcome (DITTO-HCV project)

BACKGROUND & AIMS

The second slope of viral decline induced by interferon treatment has been suggested to be influenced mainly by the hepatitis C virus (HCV)-specific T-cell response; however, this hypothesis needs to be validated by results derived from experimental studies.

METHODS

To address this issue, the HCV-specific T-cell response of 32 genotype-1-infected patients of the 270 patients enrolled in the dynamically individualized treatment of hepatitis C infection and correlates of viral/host dynamics phase III, open-label, randomized, multicenter trial was studied in relation to viral kinetics and treatment outcome.

RESULTS

Greater proliferative responses by HCV-specific CD8 cells were found before treatment in patients with a fast viral decline and with a sustained viral response. However, no significant improvement of HCV-specific CD8 responses was observed in the first weeks of therapy in both rapid viral responder and non-rapid viral responder patients. A mild enhancement of proliferative T-cell responses and a partial restoration of the cytotoxic T-cell potential was expressed only late during treatment, likely favored by HCV clearance.

CONCLUSIONS

Early restoration of an efficient T-cell response does not seem to be an essential requirement for a rapid viral decline in the first weeks of treatment. However, patients presenting a better HCV-specific CD8 cell proliferative potential at baseline are more likely to present a rapid and sustained viral response. Therefore, future treatment protocols should consider the development of strategies aimed at improving HCV-specific T-cell responses.

Selective decrease in hepatitis C virus-specific immunity among African Americans and outcome of antiviral therapy

Hepatitis C virus (HCV) infection is a leading cause of chronic hepatitis, end-stage liver disease, and hepatocellular carcinoma throughout the world. Considerable evidence indicates that the risk of viral persistence, natural history, and response to antiviral therapy varies among racial groups, but limited data exist on potential mechanisms to account for these differences. Type 1 helper (Th1) responses to HCV proteins and cytomegalovirus (CMV) antigens were examined using a sensitive interferon (IFN)-gamma enzyme-linked immunospot (ELISPOT) assay in 187 Caucasian American (CA) and 187 African American (AA) patients with chronic genotype 1 infection. ELISPOT responses were examined relative to human leukocyte antigen (HLA) class II alleles and outcome of therapy with pegylated IFN and ribavirin. Th1 responses specific to hepatitis C core protein and combined HCV antigens were significantly lower in AAs compared to CAs, but CMV responses were comparable in the 2 races. The HCV difference in immunity remained after adjusting for gender, serum alanine aminotransferase, histologic severity, and viral level, and was not accounted for by the differential prevalence of human leukocyte antigen class II alleles. Pretreatment total HCV-specific CD4+ T cell response was associated with sustained virologic response (SVR) to pegylated IFN and ribavirin; 43% of patients who had more than 168 ELISPOTs/10(6) peripheral blood mononuclear cells (above background) experienced SVR compared to 28% of those who did not (P= 0.007). ELISPOT response was independently associated with SVR by multivariable analysis.

CONCLUSION

Compared to CAs, AAs have weaker HCV-specific immunity. Pretreatment HCV-specific immunity is associated with response to combination antiviral therapy.

Analysis of the relationship between cytokine secretion and proliferative capacity in hepatitis C virus infection

CD4(+) T-cell responses are important for the outcome of hepatitis C virus (HCV) infection. However, the functional status of HCV-specific CD4(+) T cells in persistent infection is poorly understood. It is generally recognized that proliferative capacity of HCV-specific CD4(+) T cells is weak or absent in persistent infection, but whether this results from deletion of antigen-specific cells or represents maintenance of antigen-specific but poorly proliferative populations is not defined. We used a set of ex vivo assays to evaluate the functionality of HCV specific CD4(+) T cells in persistent and resolved infection. Peripheral blood mononuclear cells (PBMC) from 24 prospectively recruited HCV polymerase chain reaction (PCR) positive individuals, 12 spontaneously resolved individuals (i.e. anti-HCV+, PCR-) and 11 healthy controls were analysed for interferon-gamma (IFN-gamma) and interleukin 2 (IL-2) secretion by enzyme linked immunospot assays (ELISpot). HCV-specific CD4(+) proliferative responses of carboxy fluorescein succinimidyl ester-labelled PBMC were assessed using a sensitive single cell flow cytometric assay. Sustained IFN-gamma ELISpot responses were observed in the PCR+ group. However, proliferation of HCV-specific CD4(+) T cells in the PCR+ group was substantially reduced on a per cell basis, in parallel to IL-2 secretion, compared with responses in the PCR- group. In PCR- individuals, a strong relationship between cytokine secretion and proliferative capacity was seen. However, in PCR+ individuals, IFN-gamma secretion far exceeded proliferative capacity. During persistent HCV infection, some CD4(+) T-cell specificities appear to be lost, as measured using a range of techniques, but others, potentially important, are maintained as IFN-gamma secretors but with low proliferative capacity even using a highly sensitive assay. Such subsets may yet play a significant role in vivo and also provide a template for modulation in immunotherapeutic interventions.

Influence of HCV genotype and co-infection with human immunodeficiency virus on CD4(+) and CD8(+) T-cell responses to hepatitis C virus

The role of T-cells in clearance of hepatitis C virus (HCV) during acute infection is critical. The relevance of the immunological response in the control of HCV replication is less clear in chronic HCV infection. HCV-specific T-cell responses were examined in 92 interferon-naive individuals with chronic hepatitis C. A panel of 441 overlapping peptides spanning all expressed HCV proteins was used to measure HCV-specific T-cell responses, using flow cytometry after stimulating peripheral blood mononuclear cells (PBMCs) with different pools of these peptides. Most patients showed responses to at least one HCV protein, with NS5B for CD8(+) responses and E2 for CD4(+) responses identified most frequently. Both the prevalence and breadth of CD4(+) and CD8(+) responses were lower in co-infected patients, independently of the HCV genotype.

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.

Evolution of T-cell Responses to Hepatitis C Virus (HCV) during Pegylated Interferon plus Ribavirin treatment in HCV-Monoinfected and in HCV/HIV-Coinfected Patients

Background

The role of T-cell immunity in chronic hepatitis C virus (HCV) infection remains controversial. As in HIV infection, virus replication could drive or be contained by T-cell immunity. We have examined the effect of HIV coinfection and of suppression of HCV replication with therapy on HCV-specific T-cell responses.

Patients and Methods

Thirty-five patients with chronic hepatitis C (17 coinfected with HIV) initiating anti-HCV therapy were analysed. HCV-specific responses were assessed at different time points using intracellular interferon-γ staining in response to a panel of overlapping peptides comprising E2, NS3, NS5a and NS5b HCV proteins.

Results

At baseline, HCV-specific responses were significantly lower in HIV-coinfected patients. At week 12 of therapy, CD8+ T-cell responses against all HCV proteins significantly decreased in HCV-monoinfected patients and this was maintained throughout the follow-up period. Although the same trend occurred in the HIV-coinfected group, differences were not significant. CD4+ T-cell responses against NS3 significantly diminished in the HCV-monoinfected group, whereas in coinfected patients CD4+ T-cell responses were low at baseline and did not experience any significant variation.

Conclusions

HCV-specific T-cell responses are lower in HIV-coinfected patients and vanish following complete suppression of HCV replication under successful HCV therapy, suggesting that they are dependent on continuous antigenic stimulation.

Predictive factors of early and sustained responses to peginterferon plus ribavirin combination therapy in Japanese patients infected with hepatitis C virus genotype 1b: amino acid substitutions in the core region and low-density lipoprotein cholesterol levels

BACKGROUND/AIMS

We showed previously that amino acid (aa) substitutions in the HCV core region (HCV-CR) are predictors of non-virological response (NVR) to peginterferon (PEG-IFN) plus ribavirin (RBV) therapy. Here, we determined the predictive factors of sustained virological response (SVR) and early virologic response (EVR) to this treatment.

METHODS

We evaluated the response to 48-week PEG-IFN-RBV therapy in 114 Japanese adults infected with HCV genotype 1b and determined the predictors of EVR and SVR.

RESULTS

EVR was achieved by 70% and SVR by 45% of patients. 64% of patients who achieved EVR also showed SVR, while none of non-EVR achieved SVR. Multivariate analysis identified low-density lipoprotein cholesterol (LDL-C) (>or=86 mg/dl), aa substitutions in HCV-CR (double-wild-type; arginine at aa 70/leucine at aa 91), gamma-glutamyl transpeptidase (GGT) (<109 IU/l), RBV dose (>or=11.0mg/kg), and leukocyte count (>or=4500/mm3) as significant determinants of EVR, and aa substitutions in HCV-CR (double-wild-type), LDL-C (>or=86 mg/dl), male gender, ICG R15 (<10%), GGT (<109 IU/l), and RBV dose (>or=11.0 mg/kg) as determinants of SVR. Prediction of response to therapy based on combination of these factors had high sensitivity, specificity, positive, and negative predictive values.

CONCLUSIONS

Our study identified aa substitutions in the core region and serum LDL-C as predictors of response to PEG-IFN-RBV therapy in Japanese patients infected with HCV genotype 1b.

Discordant role of CD4 T-cell response relative to neutralizing antibody and CD8 T-cell responses in acute hepatitis C

BACKGROUND & AIMS

Acute hepatitis C virus (HCV) infection becomes chronic in the majority of patients. Although HCV-specific CD4 T-cell response is associated with HCV clearance, less is known about virus-specific CD8 T-cell or neutralizing antibody (nAb) responses and the role of CD4 help in their induction during acute infection.

METHODS

HCV-specific CD4, CD8, and HCV pseudoparticle (HCVpp) nAb responses were monitored in acutely HCV-infected patients to define their relative contributions to viral clearance.

RESULTS

Our results show that the outcome of acute hepatitis C is associated with a functional hierarchy in HCV-specific CD4 T-cell response and the scope of virus-specific, total T-cell interferon-gamma response. HCV-specific CD8 T-cell response was readily detectable in acutely HCV-infected patients regardless of virologic outcome or virus-specific CD4 T-cell response. In contrast, HCVpp-specific nAbs were readily detected in patients with chronic evolution and impaired virus-specific CD4 T-cell response but not in patients who cleared infection with robust virus-specific CD4 T-cell response.

CONCLUSIONS

The outcome of acute hepatitis C is associated with efficient virus-specific CD4 T-cell response(s) without which HCV-specific CD8 T-cell and heterologous nAb responses may develop but fail to clear viremia. Furthermore, HCV-specific nAb responses may not be induced despite robust virus-specific CD4 T-cell response.

Flying under the radar: the immunobiology of hepatitis C

The hepatitis C virus (HCV) is a remarkably successful pathogen, establishing persistent infection in more than two-thirds of those who contract it. Its success is related to its abilities to blunt innate antiviral pathways and to evade adaptive immune responses. These two themes may be related. We propose that HCV takes advantage of the impaired innate response to delay the organization of an effective adaptive immune attack. The tolerogenic liver environment may provide cover, prolonging this delay. HCV's error-prone replication strategy permits rapid evolution under immune pressure. Persistent high levels of viral antigens may contribute to immune exhaustion. Finally, the virus may benefit from the efficient enlistment of memory T and B cells in the pursuit of a moving target.

Cellular immune responses associated with occult hepatitis C virus infection of the liver

Occult hepatitis C virus (HCV) infection is a type of recently identified chronic infection that is evidenced only by detection of HCV RNA in liver; patients consistently test negative for antibodies to HCV and HCV RNA in serum. Using ex vivo and in vitro measures of T-cell responses, we have identified functional virus-specific memory CD4(+) and CD8(+) T cells in the peripheral blood of patients with occult HCV infection. The features of the virus-specific T cells were consistent with immune surveillance functions, supporting previous exposure to HCV. In addition, the magnitudes of CD4(+) and CD8(+) T-cell responses were in parallel and correlated inversely with the extent of liver HCV infection. The detection of HCV-specific T cells in individuals in whom HCV RNA can persist in the liver despite the absence of viremia and antibodies indicates that HCV replication is prolonged in the face of virus-specific CD4(+) and CD8(+) T-cell responses. These findings demonstrate that HCV-specific cellular immune responses are markers not only of previous exposure to and recovery from HCV but also of ongoing occult HCV infection.

Hepatitis C virus genotype and HIV coinfection affect cytokine mRNA levels in unstimulated PBMC but do not shift the T1/T2 balance

Rapid progression of hepatitis C virus (HCV) disease in patients with HIV/HCV may reflect different cytokine responses and be influenced by HCV genotype. This is addressed by a study of patients with HIV/HCV coinfection and infection with HCV genotype 2 or 3 (2/3). They are compared with coinfected patients infected with genotype 1 and HCV monoinfected patients matched for HCV genotype. IFN-gamma, IL-10, IL-4 and IL-4delta2 mRNA were quantified by real-time PCR in unstimulated PBMC and after in vitro stimulation with HCV core or nonstructural 3/4A antigen. In unstimulated PBMC, levels of IFN-gamma and IL-4 mRNA were lowest in HIV/HCV genotype 1 patients, intermediate in HIV/HCV genotype 2/3 patients and highest in HCV genotype 2/3 patients. Neither HCV genotype nor HIV affected levels of IL-10 mRNA in unstimulated PBMC or IFN-gamma, IL-4 and IL-10 mRNA in PBMC stimulated with HCV antigens. Levels of IL-4 and IL-4delta2 mRNA correlated in mitogen-stimulated PBMC from all patient groups but both were low in HIV/HCV genotype 1 patients. Serum soluble CD30 levels (a putative marker of a T2 cytokine environment) did not differ between patient groups. The data do not suggest a shift in the T1/T2 balance driven by HIV coinfection or HCV genotype but either may affect IL-4 bioavailability.

Immunomodulatory Activities of IFN-γ1b in Combination with Type I IFN: Implications for the Use of IFN-γ1b in the Treatment of Chronic HCV Infections

The standard of care for chronic hepatitis C, pegylated interferon-alpha (IFN-alpha) and ribavirin (RBV), causes a sustained virologic response (SVR) in approximately 50% of patients. SVR is correlated with innate and adaptive immune system responses, such as natural killer (NK) cell activation, production of IFN-alpha from immature plasmocytoid dendritic cells (pDC), and polarization of CD4(+) cells to a T helper 1 (Th1) cell phenotype. To examine how these immunologic responses vary with currently available regimens for chronic hepatitis C, cell populations purified from human peripheral blood mononuclear cells (PBMC) were treated with the clinically available combinations of pegylated IFN-alpha2b (PEG-IFN-alpha2b) + RBV, IFN-alphacon1 + RBV, or IFN- alphacon1 + IFN-gamma1b, and activation of cellular immune system components was monitored. The magnitude of NK cell activation depended on regimen, with IFN-alphacon1 + IFN-gamma1b > IFN-alphacon1 + RBV > PEG-IFN- alphaa2b + RBV. The maximum human serum concentrations of IFN-alphacon1 + IFN-gamma1b saturated NK cell activation, whereas the maximum human serum concentrations of IFN-alphacon1 + RBV or PEG-IFN-alpha2b + RBV did not. IFN-gamma1b also enhanced the production of IFN-alpha from immature pDCs, which are the dominant source of IFN-alpha upon viral infection. The rank order for induction of Th1 cell phenotype and repression of Th2 cell phenotype by the cocktails described was identical to that observed for NK cell activation. Additionally, IFN- gamma1b suppressed the ability of the hepatitis C virus (HCV) NS4 protein to enhance monocyte secretion of interleukin- 10 (IL-10), a cytokine whose expression level is correlated with viral persistence. These results suggest that addition of IFN-gamma1b to HCV treatment regimens may provide unique benefits.

Influence of genotype 3 hepatitis C coinfection on liver enzyme elevation in HIV-1-positive patients after commencement of a new highly active antiretroviral regimen: results from the EPOKA-MASTER Cohort

BACKGROUND

The independent role of hepatitis C virus (HCV) genotype 3 in liver transaminase elevation following highly active antiretroviral regimens is still controversial.

METHODS

Analysis of data from a cohort of 492 HIV/HCV-coinfected patients was conducted using an intention-to-treat approach. Incidence of grade > or = III liver transaminase elevation was estimated per 100 patient-years of follow-up. Univariate and multiple proportional hazards regression analysis of factors that may predict liver enzyme elevation was performed.

RESULTS

The incidence of grade > or = III hepatotoxicity was 25 per 100 patient-years among patients coinfected with HCV genotype 3 and 11 per 100 patient-years among those with other genotypes. On multiple proportional hazard regression analysis, time-to-grade > or = III liver enzyme elevation was directly correlated with HCV genotype 3 (hazards ratio [HR]: 2.0, 95% CI: 1.3 to 2.9; P = 0.001), male gender (HR: 2.7; 95% CI: 1.3 to 5.7; P = 0.007), chronic hepatitis B virus infection (HR: 2.9, 95% CI: 1.5 to 5.9; P = 0.002), and alanine aminotransferase level at baseline (per 10 IU/L HR: 1.10; 95% CI: 1.06 to 1.15; P < 0.001). In the same model, higher CD4 T-cell counts at baseline were inversely correlated with risk of hepatotoxicity (HR: 0.998; 95% CI: 0.997 to 0.999; P = 0.036). Moreover, among patients experienced to antiretroviral drugs, previous grade > or = III hepatotoxicity (HR: 2.8; 95% CI: 1.8 to 4.3; P < 0.001) was an adjunctive independent risk factor.

CONCLUSIONS

HIV-positive patients coinfected with HCV genotype 3 displayed a higher risk of relevant hepatotoxicity, independently from other clinical variables. The impact of HCV genotype outweighed the role of drugs in determining hepatotoxicity.

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.