Quantitative and functional differences in CD8+ lymphocyte responses in resolved acute and chronic hepatitis C virus infection

Peripheral lymphocyte subsets in chronic hepatitis C: Effects of 12 weeks of antiviral treatment with interferon-alpha plus ribavirin

Chronic infection with hepatitis C virus (HCV) causes a quantitative and functional alteration in innate and adaptative immunity. In the present work, we determined by flow-cytometry the profile of blood lymphocyte of untreated HCV patients and in subjects of this group that achieved or not an early virologic response at 12-weeks of treatment with interferon-α plus ribavirin. Twenty-six untreated HCV patients and 20 control healthy individuals were enrolled in the study. Untreated HCV patients had a higher proportion of B cell and a lower proportion of CD8(+) T cell and NK cells than healthy individuals did, but the proportions of CD4(+) T cells and Treg cells (CD4(+)CD25(+)Foxp3(+)) were similar in these patients and controls. Untreated HCV patients presenting cryoglobulinemia had a lower proportion of Treg cells and a lower Treg/NK cell ratio when compared with those without cryoglobulins. Nineteen out of 26 untreated HCV patients remained in the study and were treated with Interferon-α plus ribavirin. At 12-weeks of treatment, 10 of them achieved early virologic response (EVR), whereas 9 were non-responders (NR). EVR patients differed from NR patients in the increase of their proportion of NK cells at 12 weeks of treatment. In conclusion, untreated HCV patients exhibit an altered profile of blood lymphocyte subsets, including a reduction in the proportion of CD4(+)CD25(+)FoxP3(+)T regulatory cells in patients that present cryoglobulinemia. An early virological response at 12-weeks of treatment with IFN-α plus ribavirin seems to be associated a significant improvement in the proportion of NK cells of HCV treated patients.

The host HLA-A*02 allele is associated with the response to pegylated interferon and ribavirin in patients with chronic hepatitis C virus infection

Human leukocyte antigen (HLA) alleles are associated with both the progression of chronic hepatitis C (CHC) and the sustained virological response (SVR) to antiviral therapy. HLA-A*02 is the most common HLA allele in people of European/Caucasian descent and the Chinese and Japanese population. Therefore, we investigated whether HLA-A*02 expression is associated with disease outcome in Chinese CHC patients. Three hundred thirty-one treatment-naïve CHC patients were recruited in this study. The expression of HLA-A*02 was tested by FACS and LABType SSO assays. All patients were treated weekly with pegylated interferon plus ribavirin (PEG-IFN/RBV) according to a standard protocol. Virological response was assessed by TaqMan assay at the 4th, 12th, 24th, and 48th week of therapy, and again at the 24th week post-therapy. By the end of the study, 293 CHC patients, including 144 HLA-A*02-positive patients and 149 HLA-A*02-negative patients, were evaluable for analysis. There were no statistical differences in clinicopathological parameters between HLA-A*02-positive and negative patients before antiviral therapy (P > 0.05). The HLA-A*02-positive patients had a higher rapid virological response (RVR, 74.3 % versus 62.4 %, P = 0.03) and SVR (78.5 % versus 64.4 %, P = 0.01) and a lower relapse rate (4.2 % versus 11.9 %, P = 0.03) than HLA-A*02-negative patients. Multivariable logistic regression analysis showed that HLA-A*02 expression, liver fibrosis stages <S3, HCV genotype 2a, IL-28B rs8099917 TT, and RVR were independent predictive factors of SVR (P < 0.05). Host HLA-A*02 allele expression is associated with SVR, highlighting the importance of considering HLA-A*02 as a predictor of the response to PEG-IFN/RBV treatment in the Chinese population with CHC.

Maintenance of Th1 hepatitis C virus (HCV)-specific responses in individuals with acute HCV who achieve sustained virological clearance after treatment

BACKGROUND AND AIM

T-cell responses against hepatitis C are believed to be critical in achieving both natural and treatment-induced clearance. However, rapid clearance of antigen with early treatment of primary infection may result in reduced or poorly sustained cellular immunity. This study longitudinally examined Th1 and Th2 hepatitis C virus (HCV)-specific cytokine production and T-cell effector function from subjects enrolled in the Australian Trial in Acute Hepatitis C comparing three groups: treatment-induced clearance (sustained virological response [SVR]), treatment non-response, and untreated spontaneous clearance.

METHODS

HCV-specific T-cell responses were characterized by HCV peptide ELISpot, in vitro cytokine production, and T-cell flow cytometry assays.

RESULTS

Treated subjects with a sustained virological response (SVR) displayed a better maintenance of HCV-specific Th1 responses compared to treatment non-responders (higher interferon [IFN]-γ and interleukin (IL)-2 magnitude at week 24, broader IFN-γ responses at weeks 24 and 48, P < 0.05) and significantly increased IFN-γ responses between screening and week 48 (magnitude P = 0.026, breadth P = 0.009). Treatment-induced viral clearance was also associated with a trend toward decreased IL-10 responses (screening to week 48, P = 0.070), higher expression of CD45RO (P = 0.042) and CD38 (P = 0.088) on CD4+ T cells, and higher IFN-γR expression (CD56+ IFN-γR+ P = 0.033) compared to treatment non-responders. Untreated subjects with viral clearance also displayed high magnitude and broad HCV-specific IFN-γ and IL-2 responses early in infection; however, IFN-γ responses were not as well maintained compared to treated subjects with a SVR (week 48 magnitude, breadth P = 0.064).

CONCLUSION

Treatment-induced viral clearance of recent HCV infection is associated with maintenance of HCV-specific Th1 responses.

Comprehensive longitudinal analysis of hepatitis C virus (HCV)-specific T cell responses during acute HCV infection in the presence of existing HIV-1 infection

The aim of this study was to study the development of HCV-specific T cell immunity during acute HCV infection in the presence of an existing HIV-1 infection in four HIV-1 infected men having sex with men. A comprehensive analysis of HCV-specific T cell responses was performed at two time points during acute HCV infection using a T cell expansion assay with overlapping peptide pools spanning the entire HCV genome Three patients with (near) normal CD4+ T cell counts (range 400-970 x 10(6)/L) either resolved (n=1) or temporary suppressed HCV RNA. In contrast, one patient with low CD4+ T cell counts (330 x 10(6)/L), had sustained high HCV RNA levels. All four patients had low HCV-specific CD8+ T cell responses, and similar magnitudes of CD4+ T cell responses. Interestingly, individuals with resolved infection or temporary suppression of HCV-RNA had HCV-specific CD4+ T cell responses predominantly against nonstructural (NS) proteins. While the individual with high HCV RNA plasma concentrations had CD4+ T cell responses predominantly directed against Core. Our data show that an acute HCV infection in an HIV-1 infected person can be suppressed in the presence of HCV-specific CD4+ T cell response targeting non-structural proteins. However further research is needed in a larger group of patients to evaluate the role of HIV-1 on HCV-specific T cell responses in relation to outcome of acute HCV infection.

Monocyte-derived dendritic cell function in chronic hepatitis C is impaired at physiological numbers of dendritic cells

Monocyte-derived dendritic cells (MoDCs) are a promising cellular adjuvant for effector immune responses against tumours and chronic viral infections, including hepatitis C virus (HCV). If autologous DC therapeutic approaches are to be applied in persistent HCV infections in patients, it is important to have an unambiguous understanding of the functional status of the cell type used, namely MoDCs from patients with chronic hepatitis C (CHC) infection. Because of conflicting published reports of either impaired or normal MoDC function in CHC infection, we re-examined the ability of MoDCs from CHC and normal healthy donors (NHD) to mature to an inflammatory stimulus [tumour necrosis factor (TNF)-alpha] and their subsequent functional capabilities. Expression of maturation-associated phenotypic markers [human leucocyte antigen (HLA)-DR, CD83, CD86, CD40], allostimulatory capacity in mixed lymphocyte reactions (MLRs) and CD40-ligand-induced cytokine and chemokine generation were compared in CHC- versus NHD-MoDCs. TNF-alpha-stimulated CHC-MoDCs up-regulated phenotypic markers, but to significantly lower levels than NHD-MoDCs. At physiological ratios of DCs to T cells, CHC-MoDCs were less allostimulatory than NHD-MoDCs, but not when DC numbers were substantially increased. CHC- and NHD-MoDCs generated equivalent amounts of cytokines [TNF-alpha, interleukin (IL)-1beta, IL-6, IL-12p70, IL-15, IL-10] and chemokines [interferon-inducible protein (IP)-10, macrophage inflammatory protein (MIP)-1alpha, regulated upon activation, normal T expressed and secreted (RANTES)] after CD40 ligation. Because the functional defect was not apparent at high MoDC : T cell ratios, autologous MoDC therapy with sufficiently high numbers of DCs could, in theory, overcome any impairment of MoDC function in CHC.

Sustained virological response to peginterferon plus ribavirin in chronic hepatitis C genotype 1 patients is associated with a persistent Th1 immune response

BACKGROUND

An impairment of cellular immune response may contribute to the persistency of hepatitis C virus infection.

AIM

To analyse the Th1/Th2 cytokine profile in peripheral blood CD4(+) and CD8(+) T cells from patients with chronic hepatitis C (CHC) during treatment with pegylated interferon-alpha2a plus ribavirin and to correlate the Th1/Th2 balance with virological response (SVR).

METHODS

Prospective longitudinal study: 44 naïve genotype 1 CHC patients received PEG-IFNalpha2a plus ribavirin for 48 weeks: 26 (59.1%) achieved a SVR, 13 relapsed (29.5%) and 5 (11.4%) were non-responders. Sixteen healthy controls were analysed. The production of IL-4, IFNgamma and TNFalpha by CD4(+) and CD8(+) T cells was measured using flow cytometry, both in resting and phorbol-ester-stimulated cells.

RESULTS

First three months of treatment: the synthesis of TNFalpha by phorbol-ester-stimulated-CD4(+) T cells was higher in patients with SVR (P < 0.01). At the end of treatment, SVR was associated with higher intracellular expression of IFNgamma by stimulated-CD4(+) and CD8(+) T cells (P < 0.05). At the end of follow-up, a higher intracellular expression of IFNgamma by CD4(+) T cells was associated with a SVR.

CONCLUSIONS

A Th1-type immune response was associated with achievement of a SVR, as indicated by the persistent elevation of intracellular IFNgamma and TNFalpha.

The core-specific precursor T cell response is directed to the N-terminal and central parts of the protein and positively correlates to the viral load in chronically HCV-infected patients

The cellular immune response to hepatitis C virus (HCV) plays a critical role in determining the clearance or persistence of HCV. Moreover, in chronic HCV infection, these responses that are insufficient to eradicate virus completely may cause liver injury. In this study, the memory T cells responses specific to the core protein were measured by interferon-gamma Elispot assay after in vitro stimulation of peripheral blood mononuclear lymphocytes from chronically infected subjects. Ten out of the 22 patients studied (45%) present a core-specific response with a preferential recognition of the N-terminal and central parts. There was no relationship between T cell responses and the parameters of disease evolution as determined by ALT (serum alanine transaminase levels), and histologic hepatic damage (Metavir score A and F), but there was a positive relationship between the presence of a core-specific T cell responses and the viraemia.

Hepatitis C virus and the immune system: a concise review

Hepatitis C Virus (HCV) induces a chronic infection in 50%-80% of infected individuals, which can lead to cirrhosis and hepatocellular carcinoma. The inefficiency of the immune system in eliminating the virus is not well understood as humoral and cellular immune responses are induced. While a persistent infection is generally associated with a weak CD4+ and CD8+ T cell response during the acute phase, there is no good explanation as to why this response is strong enough in 20% of acutely infected people such that they spontaneously resolve the infection. However, the immune system partially controls the viral infection but due to a long-lasting inflammatory milieu, hepatic damage occurs. During the chronic phase of the infection, HCV does not seem to be cytopathic. This aspect is still controversial as the virus was linked to the development of cholestatic syndrome or acute lobular hepatitis after liver transplant in HCV infected patients. The development of new experimental systems such as HCV pseudoparticles, genomic replicon and transfected cell lines have improved our vision of the virus cycle as well as the understanding of the mechanism of persistence. However, a convincing explanation for the chronicity of the infection in the presence of a functional immune response is still missing and is an important area of research to understand HCV immune pathogenesis. Future research should dissect mechanisms that lead to quantitatively or qualitatively inadequate immune responses, the role of the high variability of the virus, the relevance of host's genetic factors and mechanisms of immunosuppression induced by the virus.

Interferon-gamma is produced by CD8 T cells in response to HLA-A24-restricted hepatitis C virus epitopes after sustained virus loss

Differences in cytotoxic T lymphocyte activity in hepatitis C virus infection may account for the outcome of interferon monotherapy. To investigate this hypothesis, we analysed the response of peripheral CD8(+) T cells that recognized epitopes presented by HLA-A*2402. We synthesized HLA/beta2-microglobulin/peptide complexes using two epitopes. Production of interferon-gamma by CD8(+) T cells in response to plastic-bound monomeric HLA/peptide complex was observed frequently in sustained virus responders (SVR) (n = 13) against all the peptides, NS31296-1304 (the percentage of responding patients, 61.5%) and core 129-137 (53.8%), while no interferon-gamma production was observed in non-responders (NR) (n = 13) for any of the peptides. Tetramer-staining showed the presence of CD8(+) T cells specific for all the peptides except NS31296-1304 in two SVR at the end of interferon monotherapy, although hardly any such cells were found in four NR. Specific killing was observed against peptides NS31296-1304 (3/4) and core 129-137 (1/4) in sustained responders but none in non-responders. These results suggest that the responses of cytotoxic T lymphocytes (CTLs) were induced during interferon therapy in these patients and that interferon-gamma production by CD8(+) T lymphocytes against HCV NS31296-1304 and core 129-137 are well maintained in patients with SVR compared with those with NR. These findings emphasize the importance of the CD8(+) T cell response in controlling HCV infection.

H-2 Kd-restricted hepatitis B virus-derived epitope whose specific CD8+ T lymphocytes can produce gamma interferon without cytotoxicity

It is necessary to evaluate the cytokine secretion status of CD8+ T lymphocytes and elucidate the factors influencing cytokine secretion, because the secretion of cytokines is also an important feature of CD8+ T lymphocytes, and the cytokines usually play critical roles in the outcome of diseases. We showed here that peptide AYRPPNAPI, derived from the core antigen of hepatitis B virus (HBV), could bind to H-2 Kd and induce primed splenocytes from HBcAg expression plasmid-immunized mice to produce gamma interferon (IFN-gamma) in H-2 Kd- and CD8-dependent manners instead of in a CD4-dependent manner. The induced cells were mainly CD3 and CD8 positive but had no cytotoxic effect on the corresponding target cells. When administered into HBV transgenic mice, these cells can decrease the serum HBV load without causing liver damage. These results suggest that this peptide is a special kind of CD8+ T-cell epitope, for which specific CD8+ T cells can produce IFN-gamma when antigenic stimulation is encountered but which have no cytotoxic effect on the corresponding target cells both in vitro and in HBV transgenic mice. This phenomenon indicates initially that the functional mechanisms of CD8+ T cells can be determined by their epitope specificity, which may be associated with the development of epitope-based immunotherapeutic approaches for infectious diseases and tumors.

Humoral immunity to immunodominant epitopes of Hepatitis C virus in individuals infected with genotypes 1a or 1b

Cellular immunity against multiple Hepatitis C virus (HCV) proteins is observed in patients acutely infected with HCV most of whom later resolve infection. We wished to assess humoral immunity in patients infected with HCV 1a or 1b genotypes in relation to viral load using plasma samples from HCV-infected individuals and a panel of peptides representing immunodominant epitopes of HCV structural and nonstructural proteins. Plasma from HCV 1a- and 1b-infected patients, respectively, were divided into two groups: patients with low viral load (<==100,000 RNA copies/ml) and patients with high viral load (>/=10,000,000 RNA copies/ml). The antigens were peptides representing epitopes from immunodominant regions of HCV core, E2, NS3, and NS4 proteins, as well as the hypervariable (HVR) epitopes in E2 from genotypes 1a and 1b. Individuals infected with HCV 1a evoked a stronger immune response to many immunodominant epitopes of HCV relative to individuals infected with HCV 1b. Moreover, among individuals infected with HCV 1a, those with low viral loads mounted significantly greater responses against these epitopes than did individuals with high viral loads. Our observations demonstrate that quantitatively different antibody responses are elicited against HCV depending on the genotype of infecting virus, and suggest that humoral immunity directed against multiple immunodominant epitopes in HCV 1a-infected individuals may help lower viral load in vivo.

Hepatitis C virus-specific cytolytic T cell responses after antiviral therapy

Antigen-specific T cells are likely to provide a critical defense against hepatitis C virus (HCV) infection. However, their detection in blood is uncommon except in persons who undergo spontaneous recovery after acute HCV infection. We postulated that virological responses after antiviral interferon-alpha therapy may be associated with enhanced cytolytic T cell immunity. Peripheral blood memory CTL responses were quantified using short term limiting dilution culture, with cytolytic function detected by standard chromium release assay. In this cross-sectional study, 5 of 11 interferon-alpha or interferon-alpha plus ribavirin-treated subjects exhibited cytolytic T cell responses after therapy completion; 4 of these 5 subjects were HCV RNA negative at the time of assay. In contrast, only 1 of 9 untreated chronically viremic subjects had detectable HCV-specific cytolytic T cell responses. Although the requisite factors necessary to achieve sustained virologic response after therapy remain largely undefined, the findings presented here suggest that antiviral therapy-induced virological clearance may be associated with the induction, expansion, and/or recirculation of HCV antigen-specific cytolytic T cells, and may play a role in the maintenance of a nonviremic state.

Novel CD4+ and CD8+ T-cell determinants within the NS3 protein in subjects with spontaneously resolved HCV infection

Spontaneous resolution of hepatitis C virus (HCV) infection is a relatively infrequent event, and these individuals provide a unique opportunity to characterize correlates of protective immunity as an important first step in the development of vaccine candidates. The aim of this study was to directly and comprehensively enumerate HCV-nonstructural protein 3 (NS3) specific CD4(+) and CD8(+) T cells ex vivo from HLA diverse individuals who had been successful in spontaneously resolving HCV infection. We measured interferon gamma (IFN-gamma) production with an ELISPOT assay using magnetic bead-separated CD4(+) or CD8(+) T cells in response to autologous DCs that had been pulsed with 15mer per peptides overlapping by 11 amino acids and spanning all of the NS3 protein (150 total peptides). All subjects with spontaneously recovered HCV infection demonstrated vigorous and multispecific CD4(+) T-cell responses to NS3 peptides, and 6 of 10 subjects demonstrated CD8(+) T-cell responses. More importantly, we identified novel, previously unpredicted antigenic regions, which in most cases elicited high frequencies within a given individual. In conclusion, subjects who have spontaneously eradicated HCV infection up to 35 years earlier demonstrate persistent CD4(+) and CD8(+) T-cell responses specific to NS3. By providing a comprehensive screening of all potential T-cell epitopes contained in the NS3 region, our strategy defines the breadth of the T-cell response and identifies novel, unpredicted specificities.

Pathogenic interactions between alcohol and hepatitis C

Alcohol is the most commonly abused substance in the United States, and alcohol abuse leads to alcoholic liver disease, a long recognized major public health concern. The high prevalence of chronic hepatitis C virus (HCV) infection, along with the clinical observation that HCV infection is common in alcoholic patients presenting with liver disease, has directed attention to the interaction between alcohol and HCV infection. Clinical studies have identified alcohol use as an independent risk factor for progression of fibrosis in chronic HCV infection. Experimental evidence suggests additive inhibitory effects between HCV and alcohol on antiviral immune responses. In addition, specific pathways have been identified by which HCV core protein and alcohol interact to activate hepatocytes. Nonspecific inflammatory cell recruitment and proinflammatory cytokine activation have also been implicated in both alcohol- and HCV-induced liver diseases. Further investigation of these and other pathways by which alcohol and HCV interact should unravel the mechanisms that accelerate the progression of liver disease.