Gabriele Missale

Different clinical behaviors of acute hepatitis C virus infection are associated with different vigor of the anti-viral cell-mediated immune response.

The anti-viral T cell response is believed to play a central role in the pathogenesis of hepatitis C virus infection. Since chronic evolution occurs in > 50% of HCV infections, the sequential analysis of the T cell response from the early clinical stages of disease may contribute to define the features of the T cell response associated with recovery or chronic viral persistence. For this purpose, 21 subjects with acute hepatitis C virus infection were sequentially followed for an average time of 44 wk. Twelve patients normalized transaminase values that remained normal throughout the follow-up period; all but two cleared hepatitis C virus-RNA from serum. The remaining nine patients showed persistent viremia and elevated transaminases. Analysis of the peripheral blood T cell proliferative response to core, E1, E2, NS3, NS4, and NS5 recombinant antigens and synthetic peptides showed that responses to all hepatitis C virus antigens, except E1, were significantly more vigorous and more frequently detectable in patients who normalized transaminase levels than in those who did not. By sequential evaluation of the T cell response, a difference between the two groups of patients was already detectable at the very early stages of acute infection and then maintained throughout the follow-up period. The results suggest that the vigor of the T cell response during the early stages of infection may be a critical determinant of disease resolution and control of infection.

Characterization of Hepatitis B Virus (HBV)-Specific T-Cell Dysfunction in Chronic HBV Infection

ABSTRACT Dysfunctional CD8+ T cells present in chronic virus infections can express programmed death 1 (PD-1) molecules, and the inhibition of the engagement of PD-1 with its ligand (PD-L1) has been reported to enhance the antiviral function of these T cells. We took advantage of the wide fluctuations in levels of viremia which are typical of chronic hepatitis B virus (HBV) infection to comprehensively analyze the impact of prolonged exposure to different virus quantities on virus-specific T-cell dysfunction and on its reversibility through the blocking of the PD-1/PD-L1 pathway. We confirm that chronic HBV infection has a profound effect on the HBV-specific T-cell repertoire. Despite the use of a comprehensive panel of peptides covering all HBV proteins, HBV-specific T cells were rarely observed directly ex vivo in samples from patients with chronic infection, in contrast to those from patients with acute HBV infection. In chronic HBV infection, virus-specific T cells were detected mainly in patients with lower levels of viremia. These HBV-specific CD8+ T cells expressed PD-1, and their function was improved by the blocking of PD-1/PD-L1 engagement. Thus, a broad spectrum of anti-HBV immunity is expressed by patients with chronic HBV infection and this spectrum is proportional to HBV replication levels and can be improved by blocking the PD-1/PD-L1 pathway. This information may be useful for the design of immunotherapeutic strategies to complement and optimize available antiviral therapies.

PD-1 Expression in Acute Hepatitis C Virus (HCV) Infection Is Associated with HCV-Specific CD8 Exhaustion

ABSTRACT Hepatitis C virus (HCV)-specific CD8 cell exhaustion may represent a mechanism of HCV persistence. The inhibitory receptor PD-1 has been reported to be up-regulated in exhausted CD8 cells. Therefore, we studied PD-1 expression longitudinally during acute HCV infection. Most HCV-specific CD8 cells expressed PD-1 at the time of acute illness, irrespective of the final outcome. PD-1 expression declined with the acquisition of a memory phenotype and recovery of an efficient CD8 cell function in resolving HCV infections, whereas high levels were maintained when HCV persisted and HCV-specific CD8 cells remained dysfunctional. Blocking PD-1/PDL-1 interaction with an anti-PDL-1 antibody improved the capacity of expansion of virus-specific CD8 cells.

Different cytokine profiles of intraphepatic T cells in chronic hepatitis B and hepatitis C virus infections

BACKGROUND & AIMS The cytokine pattern secreted by T cells at the site of viral replication may influence the final outcome of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. The aim of this study was to assess whether a cytokine imbalance oriented toward T helper (Th) 1 or Th2-type responses may play a role in chronic hepatitis B or C. METHODS Production of interferon (IFN)-gamma, interleukin (IL)-4, and IL-5 by wide series of T-cell clones derived from the liver of 6 patients with chronic hepatitis B (291 clones) and 9 patients with chronic hepatitis C (260 clones) was studied. T-cell clones were generated by limiting dilution from freshly isolated mononuclear cells derived from liver tissue to give a reliable representation of the intrahepatic inflammatory infiltrates. RESULTS The majority of liver-infiltrating T cells in chronic hepatitis C were Th1 cells able to secrete IFN-gamma but unable to secrete IL-4 or IL-5, whereas in hepatitis B, most CD4+ and CD8+ liver T cells were ThO-like cells able to produce not only IFN-gamma but also IL-4 and IL-5. CONCLUSIONS The different cytokine profiles of T cells within the liver in chronic HBV and HCV infections illustrate a different behavior of the local immune response in these two infections that may have pathogenetic implications.

Identification of immunodominant T cell epitopes of the hepatitis B virus nucleocapsid antigen.

Several lines of experimental evidence suggest that inclusion of core sequences in the hepatitis B vaccine may represent a feasible strategy to increase the efficacy of the vaccination. In order to identify immunodominant core epitopes, peripheral blood T cells purified from 23 patients with acute hepatitis B and different HLA haplotypes were tested with a panel of 18 short synthetic peptides (15 to 20 amino acids [AA]) covering the entire core region. All patients except one showed a strong T cell proliferative response to a single immunodominant 20 amino acid sequence located within the aminoterminal half of the core molecule. Two additional important sequences were also identified at the aminoterminal end and within the carboxyterminal half of the core molecule. These sequences were able to induce significant levels of T cell proliferation in 69 and 73% of the patients studied, respectively. T cell response to these epitopes was HLA class II restricted. The observations that (a) polyclonal T cell lines produced by PBMC stimulation with native HBcAg were specifically reactive with the relevant peptides and that (b) polyclonal T cell lines produced with synthetic peptides could be restimulated with native HBcAg, provide evidence that AA sequences contained within the synthetic peptides represent real products of the intracellular processing of the native core molecule. In conclusion, the identification of immunodominant T cell epitopes within the core molecule provides the molecular basis for the design of alternative and hopefully more immunogenic vaccines.

Antiviral Intrahepatic T-Cell Responses Can Be Restored by Blocking Programmed Death-1 Pathway in Chronic Hepatitis B

BACKGROUND & AIMS The antiviral function of peripheral hepatitis B virus (HBV)-specific T cells can be increased in patients with chronic hepatitis B by blocking the interaction of programmed death (PD)-1 with its ligand PD-L1. However, no information is available about the effects of this blockade on intrahepatic lymphocytes. We studied T-cell exhaustion and the effects of PD-1/PD-L1 blockade on intrahepatic and circulating HBV-specific T cells in patients with chronic hepatitis B. METHODS A total of 42 patients with chronic HBV infection who underwent liver biopsy were studied. The ex vivo phenotype of peripheral and intrahepatic HBV-specific CD8(+) T cells was assessed by flow cytometry with class I tetramers and antibodies to T-cell differentiation molecules. Functional recovery was evaluated by analyzing expansion and production of interferon (IFN)-gamma and interleukin (IL)-2 after short-term incubation of T cells with HBV peptides in the presence of anti-PD-L1 or control antibodies. RESULTS Intrahepatic HBV-specific CD8(+) cells expressed higher levels of PD-1 and lower levels of CD127 than their peripheral counterparts. Blockade of PD-1/PD-L1 interaction increased CD8(+) cell proliferation and IFN-gamma and IL-2 production by circulating intrahepatic lymphocytes, even though anti-PD-L1 had a stronger effect on intrahepatic compared with peripheral T cells. CONCLUSIONS T-cell exhaustion by high antigen concentrations promotes HBV-specific T-cell dysfunction by affecting phenotype and function of peripheral and intrahepatic T cells. By restoring antiviral T-cell functions, not only in peripheral but also in intrahepatic lymphocytes, anti-PD-L1 might be a good therapeutic candidate for chronic HBV infection.

Interferon (IFN)–γ–Inducible Protein–10: Association with Histological Results, Viral Kinetics, and Outcome during Treatment with Pegylated IFN-α2a and Ribavirin for Chronic Hepatitis C Virus Infection

BACKGROUND We investigated associations between interferon (IFN)-gamma-inducible protein (IP)-10 and liver histological results, viral kinetic response, and treatment outcome in patients infected with hepatitis C virus (HCV) genotypes 1-4. METHODS Plasma IP-10 was monitored before, during, and after treatment with pegylated IFN- alpha 2a and ribavirin in 265 HCV-infected patients. RESULTS In univariate analyses, a low baseline IP-10 level was significantly associated with low baseline viral load, rapid viral response (RVR), a sustained viral response (SVR), body mass index <25 kg/m2, and less-pronounced fibrosis, inflammation, and steatosis (for HCV genotypes other than 3). When the results of the univariate analyses were included in multivariate analyses, a low plasma IP-10 level, low baseline viral load, and genotype 2 or 3 infection were independent predictors of an RVR and SVR. IP-10 levels decreased 6 weeks into treatment and remained low in patients with an SVR. By contrast, plasma levels of IP-10 rebounded in patients who had detectable HCV RNA after the completion of treatment. Using cutoff IP-10 levels of 150 and 600 pg/mL for predicting an SVR in patients infected with HCV genotype 1 yielded a specificity and sensitivity of 81% and 95%, respectively. CONCLUSION Baseline IP-10 levels are predictive of the response to HCV treatment.

IP-10 predicts viral response and therapeutic outcome in difficult-to-treat patients with HCV genotype 1 infection

Plasma from 173 patients with HCV genotype 1 infection was analyzed for IP‐10 levels prior to treatment with pegylated interferon‐α‐2a and ribavirin. Significantly lower IP‐10 levels were observed in patients achieving a rapid viral response (RVR) (P < .0001), even in those with body mass index (BMI) ≥ 25 kg/m2 (P = .004) and with baseline viral load ≥ 2 million IU/mL (P = .001). Similarly, significantly lower IP‐10 levels were observed in patients obtaining a sustained viral response (SVR) (P = .0002), including those having higher BMI (P < .05), higher viral load (P = .0005), and both higher BMI and viral load (P < .03). In multivariate logistic regression analyses, a low IP‐10 value was independently predictive of both RVR and SVR. A baseline cutoff IP‐10 value of 600 pg/mL yielded a negative predictive value (NPV) of 79% (19/24) for all genotype 1–infected patients, which was comparable with that observed using a reduction in HCV‐RNA by at least 2 logs after 12 weeks of therapy (NPV 86%; 19/22); by combining the two, 30 of 38 patients (NPV 79%) potentially could have been spared unnecessary therapy. In patients having both higher BMI and viral load, cut‐off levels of 150 and 600 pg/mL yielded a positive predictive value (PPV) of 71% and NPV of 100%, respectively. In conclusion, pretreatment IP‐10 levels predict RVR and SVR in patients infected with HCV genotype 1, even in those with higher BMI and viral load. A substantial proportion of the latter patients may achieve SVR in spite of unfavorable baseline characteristics if their pretreatment IP‐10 level is low. Thus, pretreatment IP‐10 analysis may prove helpful in decision‐making regarding pharmaceutical intervention. (HEPATOLOGY 2006;44:1617–1625.)

Transient restoration of anti-viral T cell responses induced by lamivudine therapy in chronic hepatitis B

BACKGROUND/AIMS Lamivudine therapy in patients with chronic hepatitis B can induce the recovery of antiviral T cell responses. It is unknown whether the recovery of T cell responsiveness is long-lasting and persists throughout the treatment and whether the elevation of viremia which follows therapy withdrawal can restore a condition of T cell unresponsiveness. METHODS Frequency and function of circulating hepatitis B virus (HBV)-specific CD4 and CD8 cells from 12 hepatitis e surface antigen + patients with chronic hepatitis B were studied longitudinally before, during and after lamivudine therapy by intracellular cytokine staining, proliferation and cytotoxicity assays against HBV proteins and peptides. CD4-mediated responses were analyzed in all patients, whereas CD8 cells were studied in 6 HLA-A2+ patients. RESULTS HBV-specific CD4 and CD8 reactivity showed a bi-phasic behavior under lamivudine therapy with an early enhancement of T cell frequency and intensity of responses followed by a persistent decline starting from the 5th to 6th month of treatment. CONCLUSIONS Since restoration of HBV-specific T cell reactivity is only transient, our study indicates that therapeutic stimulation of HBV-specific T cell responses to complement lamivudine treatment should be done early after the initiation of lamivudine. Moreover, the transient nature of the immune reconstitution may represent a favorable condition for virus reactivation once lamivudine therapy is withdrawn.

Early kinetics of innate and adaptive immune responses during Hepatitis B Virus infection

Background and Aim: Innate immunity appears to be silent in acutely heptitis B virus (HBV)-infected chimpanzees, as shown by microarray analysis of intrahepatic gene expression. Whether this observation also applies to HBV pathogenesis in man remains undefined. The aim of this study was thus to characterise natural killer (NK) and CD56+ natural T (NT) cell responses early after human HBV infection and their relationship to the induction of adaptive immunity. Methods: Two HBV-seronegative blood donors who became hepatitis B surface antigen (HBsAg) and HBV DNA positive but had persistently normal alanine aminotransferase (ALT) were followed from a very early stage of HBV infection. The phenotype (CD69 and NKG2D) and function (cytotoxicity and interferon γ (IFNγ) production) of NK and NT cells were analysed. CD4- and CD8-mediated responses were studied in parallel with overlapping peptides covering the entire HBV sequence by ex vivo intracellular cytokine staining (ICS) for IFNγ, interleukin 2 (IL2), IL4 and IL10, and by ex vivo Elispot for IFNγ. Healthy subjects, and patients with chronic and acute HBV infection were studied for comparison. Results: An early induction of both innate and adaptive responses was observed. NK and NT cells showed faster kinetics than HBV-specific T cells with an earlier peak of activity, while CD4+ and CD8+ cell responses were mounted with a similar profile, with higher frequencies of IFNγ-producing CD8+ cells at the peak of the response. Conclusions: The innate immune system is able to sense HBV infection, as shown by the early development of NK and NT cell responses, which probably contribute to contain the HBV infection and to allow timely induction of adaptive responses.