Cristina Mori

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.

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.

Outcome of acute hepatitis C is related to virus-specific CD4 function and maturation of antiviral memory CD8 responses†

A timely, efficient, and coordinated activation of both CD4 and CD8 T cell subsets following HCV infection is believed to be essential for HCV control. However, to what extent a failure of the individual T cell subsets can contribute to the high propensity of HCV to persist is still largely undefined. To address this issue, we analyzed the breadth, vigor, and quality of CD4 and CD8 responses simultaneously with panels of peptides covering the entire HCV sequence or containing the HLA‐A2–binding motif, and with recombinant HCV proteins in 16 patients with acute HCV infection by tetramer staining, ELISPOT, and intracellular cytokine staining for interferon γ, interleukin (IL)‐2, IL‐4, and IL‐10. Our results indicate that at clinical onset, CD8 responses are similarly weak and narrowly focused in both self‐limited and chronically evolving infections. At this stage, CD4 responses are deeply impaired in patients with a chronic outcome as they are weak and of narrow specificity, unlike the strong, broad and T helper 1–oriented CD4 responses associated with resolving infections. Only patients able to finally control infection show maturation of CD8 memory sustained by progressive expansion of CD127+ CD8 cells. Thus, a poor CD8 response in the acute stage of infection may enhance the overall probability of chronic viral persistence. In conclusion, the presence of functional CD4 responses represents one of the factors dictating the fate of infection by directly contributing to control of the virus and by promoting maturation of protective memory CD8 responses. (HEPATOLOGY 2006;44:126–139.)

Peginterferon-α does not improve early peripheral blood HBV-specific T-cell responses in HBeAg-negative chronic hepatitis

BACKGROUND & AIMS The effect of IFN-α therapy on HBV-specific T-cell responses in HBeAg-negative, genotype D, chronic hepatitis B is largely undefined. Understanding to what extent IFN-α can modulate HBV-specific T-cells is important to define strategies to optimize IFN efficacy and to identify immunological parameters to predict response to therapy. METHODS HBV-specific T-cell responses were analyzed longitudinally ex vivo and after expansion in vitro in 15 patients with genotype D, HBeAg-negative chronic hepatitis B treated with peginterferon-α-2a. HBV proteins and synthetic peptides were used to stimulate T-cell responses. Analysis of the CD4 and CD8 T-cell functions was performed by ELISPOT, intracellular cytokine and tetramer staining. The effect of anti-PD-L1 on T-cell functions was also analyzed. RESULTS Ex vivo IFN-γ production by total HBV-specific T-cells was significantly greater before therapy in patients who showed HBV DNA <50 IU/ml at weeks 24 and/or 48 of therapy. No significant improvement of T-cell proliferation, Th1 cytokine production and cytotoxicity was observed during IFN therapy by both ex vivo and in vitro analysis. PD-1/PD-L1 blockade showed a modest improvement of cytokine production in a total of 15% of T-cell lines. CONCLUSIONS IFN-α did not improve peripheral blood HBV-specific T-cell responses in the first 24 weeks of treatment, consistent either with a predominant antiviral/antiproliferative effect or with an immunomodulatory activity on other arms of the immune system which were not analyzed in our study. A better pre-treatment ex vivo IFN-γ production was associated with better chances to control HBV replication during therapy and represents a promising predictor of IFN efficacy.

Antiviral CD8-mediated responses in chronic HCV carriers with HBV superinfection

Hepatitis B virus (HBV) superinfection in chronic hepatitis C represents a natural model to investigate whether or not hepatitis C virus (HCV) can influence priming and maturation of antiviral T cells; whether or not HBV superinfection, which is known to determine control of HCV replication, can restore HCV‐specific T cell responsiveness; and whether or not cytokines stimulated by HBV infection can contribute to HCV control. To address these issues, the function of CD8 cells specific for HBV and HCV was studied longitudinally in two chronic HCV patients superinfected with HBV. Patients with acute hepatitis B were also examined. Frequency and function of HBV tetramer+ CD8 cells were comparable in patients acutely infected with HBV with or without chronic HCV infection. HBV‐specific CD8 cell function was efficiently expressed irrespective of serum HCV‐RNA levels. Moreover, fluctuations of HCV viremia at the time of HBV superinfection were not associated with evident changes of CD8 responsiveness to HCV. Finally, no correlation was found between serum levels of interferon α, interleukin (IL)‐12, IL‐10, or IL‐18 and control of HCV replication. In conclusion, HCV did not affect the induction of primary and memory HBV‐specific CD8 responses. HCV‐specific CD8 responses were undetectable when HCV‐RNA was negative, showing that inhibition of HCV replication in the setting of a HBV superinfection was not sufficient to induce a restoration of CD8 reactivity against HCV. (H EPATOLOGY 2004;40:289–299.)