Incubation phase of acute hepatitis B in man: dynamic of cellular immune mechanisms

Immune system and hepatitis B virus infection

The immune system plays an important role in determining the outcome of hepatitis B virus (HBV) infection. This is because recovery from of acute HBV infection is associated with a clear division in the profile of adaptive immune response. Multispecific antiviral CD4 and CD8 responses with a type 1 cytokine production can be observed in patients who recover from acute HBV infection. On the other hand, those who develop chronic infection tend to have a weak virus specific T cell response. Therapeutic strategies aimed at correcting this defective T cell reactivity could represent a complementary approach to the cure of chronic HBV infection.

Does rapid oligomerization of hepatitis B envelope proteins play a role in resistance to proteasome degradation and enhance chronicity?

This review discusses the nature of hepatitis B and C chronicity from a virological perspective. Work described in the literature and our in vitro studies of HBV polypeptide morphogenesis lead us to speculate about a role for HBsAg complex formation in immune evasion that may be especially important during the initial period of infection. Briefly, although viral structural proteins do eventually provide epitopes recognized by the host, we suggest that these HBs Ag complexes, which may themselves be refractory to proteasomal degradation, are an important way by which the virus shields its epitopes and evades early recognition by the cellular immune system. This suggests a central strategy by which the virus has evolved, structurally, to enable the establishment of persistent infection of its host. The concept offers an explanation for the nearly unidirectional and rapid kinetics whereby HBV proteins form multimers and generate a surplus of viral structures that have not been thought to serve any useful structural purpose.

Expression of the interleukin-7 receptor alpha chain (CD127) on virus-specific CD8+ T cells identifies functionally and phenotypically defined memory T cells during acute resolving hepatitis B virus infection

Virus-specific CD8+ T cells play a central role in the outcome of several viral infections, including hepatitis B virus (HBV) infection. A key feature of virus-specific CD8+ T cells is the development of memory. The mechanisms resulting in the establishment of T-cell memory are still only poorly understood. It has been suggested that T-cell memory may depend on the survival of virus-specific CD8+ T cells in the contraction phase. Indeed, a population of effector cells that express high levels of the interleukin-7 receptor alpha chain (CD127) as the precursors of memory CD8+ T cells has recently been identified in mice. However, very little information is currently available about the kinetics of CD127 expression in an acute resolving viral infection in humans and its association with disease pathogenesis, viral load, and functional and phenotypical T-cell characteristics. To address these important issues, we analyzed the HBV-specific CD8+ T-cell response longitudinally in a cohort of six patients with acute HBV infection who spontaneously cleared the virus. We observed the emergence of CD127 expression on antigen-specific CD8+ memory T cells during the course of infection. Importantly, the up-regulation of CD127 correlated phenotypically with a loss of CD38 and PD-1 expression and acquisition of CCR7 expression: functionally with an enhanced proliferative capacity and clinically with the decline in serum alanine aminotransferase levels and viral clearance. These results suggest that the expression of CD127 is a marker for the development of functionally and phenotypically defined antigen-specific CD8+ memory T cells in cleared human viral infections.

Differentiating acute hepatitis B from the first episode of symptomatic exacerbation of chronic hepatitis B

In countries with intermediate or high endemicity for chronic hepatitis B virus (HBV) infection, exacerbations of chronic hepatitis B (CHB) are common. We studied the clinical, biochemical, and virologic characteristics of patients first presenting clinically with features of acute icteric hepatitis B, to identify features that might differentiate between acute viral hepatitis B (AVHB) from first episode of exacerbation of chronic hepatitis (ECHB). We retrospectively analyzed 79 patients (mean age 35.4 +/- 14 years; M:F = 60:19) who first presented clinically as AVHB, within 4 weeks of onset of symptoms. Patients who on follow-up cleared HBsAg and/or did not develop any clinical, radiologic, or histologic evidence of chronic liver disease (CLD) were categorized as AVHB (group 1). Patients who had persistence of HBsAg and developed clinical, biochemical, radiologic, or histologic evidence of chronic liver disease were categorized as ECHB (group 2). Forty-nine patients were in group 1 and 30 in group 2. The 2 groups were comparable with respect to prodrome, onset of jaundice, serum bilirubin, ALT, prothrombin time prolongation, serum albumin, and A/G ratio. Among group 1 patients, 78% had IgM anti-HBc positive in titers > 1:1000; in group 2, there were negative or positive in titers < 1:1000 in 70% patients (P < .001). Forty-seven of 49 (95.9%) patients in group 1 had HBV-DNA levels < 0.5 pg/mL, whereas 26 of 30 (86.73%) patients in group 2 had levels > 0.5 pg/mL (P < or = .001). Quantitative HBV DNA and IgM anti-HBc titers at initial presentation can differentiate patients with a true episode of acute hepatitis B from patients with first episode of symptomatic exacerbation of chronic hepatitis B. Clinical and biochemical features do not help in differentiating the two.

Immunopathogenesis of hepatitis C virus infection: multifaceted strategies subverting innate and adaptive immunity

Hepatitis C virus (HCV) infection is one of the major causes of chronic liver disease worldwide. The critical role of innate as well as adaptive immunity has been reported in HCV persistence and liver injury. In the early phase of acute infection, HCV continues to replicate in the liver, suggesting the HCV capability of inhibiting innate immunity. The sustained, vigorous and multiepitope-specific CD4+ and CD8+ T cell responses are essential for spontaneous HCV clearance. HCV-specific CD8+ T cells are primary elements for HCV clearance by inducing hepatocyte apoptosis, in which Fas/CD95 is fundamentally involved. However, once HCV persistency develops, HCV utilizes multifaceted arms to subvert various immune effectors. During IFNalpha-based therapy, the enhancement of HCV-specific CD4+ T cell response followed by HCV eradication has been reported, however, it remains obscure whether the therapeutic HCV clearance is able to restore the durable immune competency to HCV. Further investigation is still warranted to establish the means to direct HCV-specific immune responses in the desired way.

Natural Killer-Cell Cytotoxicity in HIV-Positive and HIV-Negative Patients with and Without Severe Course of Hepatitis B Virus Infection

Natural killer (NK) cells represent the first line of defence against viral infections but, in the case of hepatitis B virus (HBV), may also be involved in liver injury. We here compared NK-cell activity of 11 patients with acute HBV infection, either HIV-positive or HIV-negative, with that of 11 healthy subjects. One of the HIV-positive patients, characterized by a severe immunodeficiency, died 3 weeks after hospitalization for HBV-related fulminant hepatitis (FH). He displayed a remarkable NK-cell cytotoxicity against both cell lines and autologous dendritic cells, whereas the NK-cell activity of the remaining patients was significantly reduced as compared with healthy individuals. Our findings suggest that NK-cell-mediated cytotoxicity could contribute to the development of HBV-related acute liver failure in HIV-positive patients with severe immunodeficiency. An immunopathological model of FH in immunocompromised patients was proposed.

Kinetics of phytohemaglutinin-induced IFN-γ and TNF-α expression in peripheral blood mononuclear cells from patients with chronic hepatitis B after liver transplantation

AIM: To study the association between host immunity and hepatitis B virus (HBV) recurrence after liver transplantation.

METHODS: Peripheral blood mononuclear cells (PBMC) were isolated from 40 patients with hepatitis B and underwent orthotopic liver transplantation (OLT) before and 2, 4, 8 wk after surgery. After being cultured in vitro for 72 h, the levels of INF-γ and TNF-α in culture supernatants were detected with ELISA. At the same time, the quantities of HBV DNA in serum and PBMCs were measured by real time PCR.

RESULTS: The levels of INF-γ and TNF-α in PBMC culture supernatants decreased before and 2, 4 wk after surgery in turns (INF-γ 155.52±72.32 ng/L vs 14.76±9.88 ng/L vs 13.22±10.35 ng/L, F = 6.946, P = 0.027<0.05; TNF-α 80.839±46.75 ng/L vs 18.59±17.29 ng/L vs 9.758±7.96 ng/L, F = 22.61, P = 0.0001<0.05). The levels of INF-γ and TNF-α were higher in groups with phytohemagglutinin (PHA) than in those without PHA before surgery. However, the difference disappeared following OLT. Furthermore, INF-γ and TNF-α could not be detected in most patients at wk 4 and none at wk 8 after OLT. The HBV detection rate and virus load in PBMC before and 2, 4 wk after surgery were fluctuated (HBV detected rate: 51.4%, 13.3%, 50% respectively; HBV DNA: 3.55±0.674 log(10) copies/mL vs 3.00±0.329 log(10) copies/mL vs 4.608±1.344 log(10) copies/mL, F = 7.582, P = 0.002<0.05). HBV DNA in serum was 4.48±1.463 log(10) copies/mL before surgery and <103 copies/mL after OLT except for one with 5.72±106 copies/mL 4 wk after OLT who was diagnosed as HBV recurrence. The levels of INF-γ and TNF-α were lower in patients with a high HBV load than in those with a low HBV load (HBV DNA detected/undetected in PBMCs: IFN-γ 138.08±72.44 ng/L vs 164.24±72.07 ng/L, t = 1.065, P = 0.297>0.05, TNF-α 80.75±47.30 ng/L vs 74.10±49.70 ng/L, t = 0.407, P = 0.686>0.05; HBV DNA positive/negative: IFN-γ 136.77±70.04 ng/L vs 175.27±71.50 ng/L, t = 1.702, P = 0.097>0.05; TNF-α 75.37±43.02 ng/L vs 81.53±52.46 ng/L, t = 0.402, P = 0.690>0.05).

CONCLUSION: The yielding of INF-γ and TNF-α from PBMCs is inhibited significantly by immunosuppressive agents following OLT with HBV load increased, indicating that the impaired immunity of host is associated with HBV recurrence after OLT.

Intrahepatic CD8+ T-lymphocyte response is important for therapy-induced viral clearance in chronic hepatitis B infection

BACKGROUND/AIMS

To determine which immune cells contribute to HBV-clearance during antiviral therapy, we performed a longitudinal analysis of intrahepatic immune cells during interferon-alpha therapy of chronic HBV-patients using the FNAB technique.

METHODS

Twenty chronic HBeAg+-patients were treated with pegylated alpha-interferon combined with lamivudine or placebo for 52 weeks. FNAB and blood specimens were obtained at week 0, 2, 8 and 52. CD4+- and CD8+ T-lymphocytes, CD56+ cells, IFNgamma and granzyme B (GrB) were immunocytochemically quantified.

RESULTS

The relative numbers of CD56+ cells and CD8+ T-lymphocytes were significantly higher in FNAB compared to blood at all time-points. Responders (n=9) exhibited significant increases in intrahepatic CD8+ and CD8+GrB+ lymphocytes, a small elevation in CD8+IFNgamma+ T-lymphocytes, no change in CD4+ T-lymphocytes, and a decrease in intrahepatic CD56+ cells during the first weeks of therapy. In non-responders (n=11) no significant changes in CD4+- and CD8+ T-lymphocytes and an increase in intrahepatic and CD56+ cells were observed during therapy.

CONCLUSIONS

The intrahepatic CD8+ T-lymphocyte, but not the CD4+ T-lymphocyte or NK/NKT-cell response, is important for HBV clearance during interferon-alpha therapy, and the antiviral effect may be mediated by both cytolytic and non-cytolytic mechanisms.

Decreased frequency and function of circulating plasmocytoid dendritic cells (pDC) in hepatitis B virus infected humans

The Type 2 precursor plasmacytoid dendritic cells (pDC) represent the most important cell type in antiviral innate immunity. To understand the function of pDC during hepatitis B virus infection, the frequency and function of circulating pDC were analyzed by flow cytometric analysis, and IFN-alpha secretion of total PBMCs was determined by ELISA assay in 25 healthy subjects and 116 patients at various stages of chronic hepatitis B virus infection (CHB). The number of circulating pDC was found to be significantly lower in patients with CHB and associated liver cirrhosis (LC). The ability of PBMCs to secrete IFN-alpha also decreased significantly. There was a corresponding decrease of circulating NK cells and CD8+ T cells. We observed that lamuvidine antiviral therapy restored the number of circulating pDC and there was a reversal of pDC frequency with the control of HBV replication in chronic HBV patients, indicating these subjects are unlikely to be totally immunocompromised. The decrease of pDC was found to be related to nosocomial infections in LC patients. Our results suggest that CHB patients probably have a quantitative and qualitative impairment of circulating pDC or NK cells, which may be associated with HBV persistent infection as well as the nosocomial infections that arise in LC patients.

Differential dynamics of the peripheral and intrahepatic cytotoxic T lymphocyte response to hepatitis B surface antigen

The distribution and dynamics of the cytotoxic T lymphocyte (CTL) response to hepatitis B surface antigen (HBsAg) were studied in mice after intramuscular DNA immunization and after hepatic infection by a recombinant adenovirus that expresses the hepatitis B virus genome (Ad-HBV). CTLs specific for HBsAg accumulate preferentially in the spleen after DNA immunization but are primarily intrahepatic after Ad-HBV infection. The secondary CTL response to Ad-HBV in DNA-primed mice is characterized by rapid depletion of effector CTLs from the spleen, and their expansion in the liver where they cause hepatitis, secrete interferon gamma (IFNgamma), and inhibit HBV gene expression. Suppression of HBsAg synthesis is accompanied by disappearance of intrahepatic IFNgamma-producing CTLs and their reaccumulation in the spleen. The data suggest a possible explanation for the paucity and functional deficiency of HBV-specific CTLs in the periphery during chronic HBV infection, and that the severity of infection can be worsened by a preexisting CTL response if neutralizing antibody is not also present.

Acute phase HBV-specific T cell responses associated with HBV persistence after HBV/HCV coinfection

To characterize acute-phase hepatitis B virus (HBV)-specific T cell responses associated with self-limited and persistent HBV infections, we compared a patient with acute HBV/HCV coinfection, who was able to control HCV but developed chronic hepatitis B, with patients who resolved acute HBV infection spontaneously. Acute-phase CD4 responses were efficient in self-limited infections but undetectable in the coinfected patient with HBV persistence. CD8 responses were multispecific irrespective of the outcome of infection, but the CD8 repertoire associated with HBV persistence lacked the most dominant specificities detectable in self-limited infections. In conclusion, insufficient CD4 help and defective CD8 repertoire may play a role at the early stages of infection in influencing HBV persistence.

Reduced hepatitis B virus (HBV)-specific CD4+ T-cell responses in human immunodeficiency virus type 1-HBV-coinfected individuals receiving HBV-active antiretroviral therapy

Functional hepatitis B virus (HBV)-specific T cells are significantly diminished in individuals chronically infected with HBV compared to individuals with self-limiting HBV infection or those on anti-HBV therapy. In individuals infected with human immunodeficiency virus type 1 (HIV-1), coinfection with HBV is associated with an increased risk of worsening liver function following antiviral therapy and of more rapid HBV disease progression. Total HBV-specific T-cell responses in subjects with diverse genetic backgrounds were characterized by using a library of 15-mer peptides overlapping by 11 amino acids and spanning all HBV proteins. The magnitude and breadth of CD4(+) and CD8(+) T-cell responses to HBV in peripheral blood were examined by flow cytometry to detect gamma interferon production following stimulation with HBV peptide pools. Chronic HBV carriers (n = 34) were studied, including individuals never treated for HBV infection (n = 7), HBV-infected individuals receiving anti-HBV therapy (n = 13), and HIV-1-HBV-coinfected individuals receiving anti-HBV therapy (n = 14). CD4(+) and CD8(+) HBV-specific T-cell responses were more frequently detected and the CD8(+) T-cell responses were of greater magnitude and breadth in subjects on anti-HBV treatment than in untreated chronic HBV carriers. There was a significant inverse correlation between detection of a HBV-specific T-cell response and HBV viral load. HBV-specific CD4(+) and CD8(+) T-cell responses were significantly (fivefold) reduced compared with HIV-specific responses. Although, the frequency and breadth of HBV-specific CD8(+) T-cell responses were comparable in the monoinfected and HIV-1-HBV-coinfected groups, HBV-specific CD4(+) T-cell responses were significantly reduced in HIV-1-HBV-coinfected individuals. Therefore, HIV-1 infection has a significant and specific effect on HBV-specific T-cell immunity.

T cell immunity in hepatitis B and hepatitis C virus infection: implications for autoimmunity

T cells are involved in the pathogenesis of important liver diseases including both autoimmune liver diseases and viral hepatitis. In addition to playing a crucial role in the control of hepatitis viruses, T cell responses are also responsible for the liver injury during acute and chronic phases of viral hepatitis. In this article, we reviewed current literature on T cell immunity to hepatitis B and C viruses. In addition, antigen presenting cells that are critical for T cell immunity against these viruses are also discussed. This will provide insights to the understanding of T cell immunity in autoimmune liver diseases due to the similar role of T cells in autoimmune liver diseases and viral hepatitis.

Evolution of hepatitis B virus during primary infection in humans: transient generation of cytotoxic T-cell mutants

BACKGROUND & AIMS

Acute hepatitis B is a highly dynamic human viral infection during which the hepatitis B virus can generate many genetic variants.

METHODS

We analyzed the evolution of the hepatitis B virus genome in sequential serum samples from a unique cohort of patients with acute infection acquired from a single source.

RESULTS

We showed that most mutations were nonsynonymous, that genetic diversity was greatest at the peak of viremia, and that patients who resolved their infection ("resolvers") showed a significantly higher level of diversity in the core, surface, and polymerase genes compared with those who progressed to chronic infection. Overall, the core gene showed the greatest genetic diversity. In resolvers who possessed an HLA-A*0201 haplotype, the emergence of mutants in the immunodominant HLA-A*0201-restricted core 18-27 epitope was observed. Functional studies showed that these mutants were less able to stimulate interferon-gamma release from core 18-27 specific CD8 + T-cell lines. However, they appeared only as a transient low-abundance species and were rapidly displaced by wild-type sequences before resolution of infection, and their overall significance is uncertain.

CONCLUSIONS

Overall, genetic evolution of the hepatitis B virus differs at early time points between patients who experience acute resolving hepatitis B and those who progress to chronicity. These observations suggest that the rapid development of broadly reactive host immune responses leads to clearance of hepatitis B virus, even in the presence of possible CD8+ T-cell immune escape variants.

Induction or expansion of T-cell responses by a hepatitis B DNA vaccine administered to chronic HBV carriers

Despite the availability of effective hepatitis B vaccines for many years, over 370 million people remain persistently infected with hepatitis B virus (HBV). Viral persistence is thought to be related to poor HBV-specific T-cell responses. A phase I clinical trial was performed in chronic HBV carriers to investigate whether HBV DNA vaccination could restore T-cell responsiveness. Ten patients with chronic active hepatitis B nonresponder to approved treatments for HBV infection were given 4 intramuscular injections of 1 mg of a DNA vaccine encoding HBV envelope proteins. HBV-specific T-cell responses were assessed by proliferation, ELISpot assays, and tetramer staining. Secondary end points included safety and the monitoring of HBV viraemia and serological markers. Proliferative responses to hepatitis B surface antigen were detected in two patients after DNA injections. Few HBV-specific interferon gamma-secreting T cells were detectable before immunization, but the frequency of such responses was significantly increased by 3 DNA injections. Immunization was well tolerated. Serum HBV DNA levels decreased in 5 patients after 3 vaccine injections, and complete clearance was observed in 1 patient. In conclusion, this study provides evidence that HBV DNA vaccination is safe and immunologically effective. We demonstrate that DNA vaccination can specifically but transiently activate T-cell responses in some chronic HBV carriers who do not respond to current antiviral therapies.

The use of lamivudine for patients with acute hepatitis B (a series of cases)

There are limited data on the use of lamivudine for patients with severe forms of acute hepatitis B. We report our experience with the use of lamivudine in six patients with acute HBV infection. Lamivudine was justified by disease severity for four patients and by concerns about risk of chronicity for two patients. The diagnoses of the treated patients were: fulminant liver failure (two patients), severe acute hepatitis B, protracted acute hepatitis B, and new HBV infection in the renal dialysis setting (two patients, one with severe liver injury). Serum HBV DNA titres ranged from 10(5) to 10(7) copies/mL prior to commencement of lamivudine. Lamivudine treatment was associated with a decline in serum HBV DNA and serum transaminases in all patients. All but one patient survived. A 58-year-old man with fulminant hepatitis and multiple organ failure died despite antiviral treatment. When possible, HBeAg and HBsAg seroconversion was documented during follow-up. In the absence of a randomized, prospective study of lamivudine in patients with severe acute hepatitis B, our data encourage the use of this safe and well tolerated drug.

Functional impairment of myeloid and plasmacytoid dendritic cells of patients with chronic hepatitis B

Dendritic cells (DC) play an important role in the induction of T-cell responses. We hypothesize that the hampered antiviral T-cell response in chronic hepatitis B patients is a result of impaired dendritic cell function. In this study, we compared the number, phenotype and functionality of two important blood precursor DC, myeloid DC (mDC) and plasmacytoid DC (pDC), of chronic hepatitis B patients with healthy volunteers. No differences in percentages of mDC and pDC in peripheral blood mononuclear cells were observed between chronic hepatitis B patients and healthy controls. The allostimulatory capacity of isolated and in vitro matured mDC, but not of pDC, was significantly decreased in patients compared to controls. Accordingly, a decreased percentage of mDC expressing CD80 and CD86 was observed after maturation, compared to controls. In addition, mDC of patients showed a reduced capacity to produce tumor necrosis factor alpha after a stimulus with synthetic double-stranded RNA and interferon gamma. Purified pDC from patients produced less interferon alpha, an important antiviral cytokine, in response to stimulation with Staphylococcus aureus Cowan strain I than pDC isolated from controls. In conclusion, mDC and pDC are functionally impaired in patients with chronic hepatitis B. This might be an important way by which hepatitis B virus evades an adequate immune response, leading to viral persistence and disease chronicity.

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Longitudinal analysis of CD8+ T cells specific for structural and nonstructural hepatitis B virus proteins in patients with chronic hepatitis B: implications for immunotherapy

The cytotoxic T-cell response in chronic hepatitis B virus (HBV) infection has been described as weak and mono- or oligospecific in comparison to the more robust virus-specific T-cell response present in resolved infection. However, chronic hepatitis B is a heterogeneous disease with markedly variable levels of virus replication and liver disease activity. Here we analyzed (both directly ex vivo and after in vitro stimulation) the HBV-specific CD8 T-cell responses against structural and nonstructural HBV proteins longitudinally in patients with different patterns of chronic infections. We found that the profiles of virus-specific CD8(+)-T-cell responses during chronic infections are highly heterogeneous and influenced more by the level of HBV replication than by the activity of liver disease. An HBV DNA load of <10(7) copies/ml appears to be the threshold below which circulating multispecific HBV-specific CD8(+) T cells are consistently detected. Furthermore, CD8(+) T cells with different specificities are differentially regulated during chronic infections. HBV core-specific CD8(+) T cells are associated with viral control, while CD8(+) T cells specific for envelope and polymerase epitopes can occasionally be found in the setting of high levels (>10(7) copies) of HBV replication. These findings have implications for the design of immunotherapy for chronic HBV infections.

Hepatitis B virus: pathogenesis, viral intermediates, and viral replication

Although HBV has the potential to generate an almost limitless spectrum of quasispecies during chronic infection, the viability of the majority of these quasispecies is almost certainly impaired due to constraints imposed by the remarkably compact organization of the HBV genome. On the other hand, single mutations may affect more than one gene and result in complex and unpredictable effects on viral phenotype. Better understanding of the constraints imposed by gene overlap and of genotype-phenotype relationships should help in the development of improved antiviral strategies and management approaches. Although the probability of developing viral resistance is directly proportional to the intensity of selection pressure and the diversity of quasispecies, potent inhibition of HBV replication should be able to prevent development of drug resistance because mutagenesis is replication dependent. If viral replication can be suppressed for a sufficient length of time, viral load should decline to a point where the continued production of quasispecies with the potential to resist new drug treatments no longer occurs. Clinical application of this concept will require optimization of combination therapies analogous to highly active antiretroviral therapy (HAART) for HIV infection. Total cure of hepatitis B will require elimination of the intranuclear pool of viral minichromosomes, which will probably only be achieved by normal cell turnover, reactivation of host immunity, or elucidation of the antiviral mechanisms operating during cytokine clearance in acute hepatitis B (see Fig. 1).

Kinetics of viremia and acute liver injury in relation to outcome of neonatal woodchuck hepatitis virus infection

The kinetics of serum viral responses and acute liver injury were studied during neonatal woodchuck hepatitis virus (WHV) infection in relation to the chronic or resolved outcome. The mean concentrations of serum WHV DNA and surface antigen were significantly higher by week 10 post infection in chronic infections compared to resolving infections, and diverged even further by the time of peak viral load development in serum (week 12). After week 12, these viral markers were detected less frequently with time and at lower concentrations in the resolved outcome. In both outcomes, mean serum activities of hepatic enzymes became increased significantly above baseline by weeks 10-12, peaked at week 14, and normalized by weeks 20-22, thus indicating transient acute liver injury. The increasing liver injury responses were comparable between outcomes at week 12, when serum viral load was markedly higher in the developing chronic infections. This suggested a deficiency in early non-cytolytic control of infection in the chronic outcome. At week 14, liver injury was significantly greater in the resolved outcome and associated with higher mean Fas ligand (FasL) and perforin messenger RNAs (mRNAs) in liver compared to the chronic outcome. This indicated greater immune-mediated killing of infected hepatocytes during resolution. Thus, chronicity as an outcome of neonatal WHV infection develops relatively early during the acute phase of infection due to reduced immune-mediated clearance of infected hepatocytes by both cytolytic and non-cytolytic processes.

Underwhelming the immune response: effect of slow virus growth on CD8+-T-lymphocyte responses

The speed of virus replication has typically been seen as an advantage for a virus in overcoming the ability of the immune system to control its population growth. Under some circumstances, the converse may also be true: more slowly replicating viruses may evoke weaker cellular immune responses and therefore enhance their likelihood of persistence. Using the model of lymphocytic choriomeningitis virus (LCMV) infection in mice, we provide evidence that slowly replicating strains induce weaker cytotoxic-T-lymphocyte (CTL) responses than a more rapidly replicating strain. Conceptually, we show a "bell-shaped" relationship between the LCMV growth rate and the peak CTL response. Quantitative analysis of human hepatitis C virus infections suggests that a reduction in virus growth rate between patients during the incubation period is associated with a spectrum of disease outcomes, from fulminant hepatitis at the highest rate of viral replication through acute resolving to chronic persistence at the lowest rate. A mathematical model for virus-CTL population dynamics (analogous to predator [CTL]-prey [virus] interactions) is applied in the clinical data-driven analysis of acute hepatitis B virus infection. The speed of viral replication, through its stimulus of host CTL responses, represents an important factor influencing the pathogenesis and duration of virus persistence within the human host. Viruses with lower growth rates may persist in the host because they "sneak through" immune surveillance.

Effects of zhaoyangwan on chronic hepatitis B and posthepatic cirrhosis

AIM: To study the therapeutic effects of zhaoyangwan (ZYW) on chronic hepatitis B and hepatic cirrhosis and the anti-virus, anti-fibrosis and immunoregulatory mechanisms of ZYW.

METHODS: Fifty cases of chronic hepatitis B and posthepatic cirrhosis with positive serum HBsAg, HBeAg, anti-Hbc and HBV-DNA were divided randomly and single-blindly into the treatment group (treated with ZYW) and the control group (treated with interferon). After 3 month treatment, the effects of the treatment group and the control group were evaluated.

RESULTS: The serum ALT normalization was 83.3%(30/36) in the treatment group and 85.7%(12/14) in the control group, with no significant difference (χ² = 0.043, P > 0.05). After the course, the negative expression rates of the serum HBV-DNA and HBeAg were 44.4%(16/36) and 50%(18/36) in the treatment group, and 50%(7/14) and 50%(7/14) in the control group, respectively, with no significant difference (χ² = 0.125, χ² = 0.00, both P > 0.05). Negative HBsAg and positive HBsAb appeared in 4 cases of the treatment group and 1 case of the control group. Serum anti-HBc turned negative in 6 cases of the treatment group and 1 case of the control group, respectively. After the ZYW treatment, serum CD₃⁺, CD₄⁺, CD₈⁺, CD₄⁺/CD₈⁺ and NK cell activation were significantly increased. Only serum CD₃⁺ and NK cell activation were significantly increased in the control group with a significant difference between the two groups. The serum C₄, C_1q, C₃, B and C₉ were significantly increased in the treatment group. In the control group only the serum C₄ was increased. The concentration of serum interferon had no change after treatment with ZYW, while it was significantly increased in the control group after treatment with interferon. The ultrastructure of the liver restored, which helped effectively to reduce the degeneration and necrosis of hepatic cells, infiltration of inflammatory cells and hepatic cirrhosis.

CONCLUSION: ZYW is a pure Chinese herbal medicine. It can exert potent therapeutic effects on chronic hepatitis B and posthepatic cirrhosis. ZYW has similar therapeutic effects to those of interferon. It is cheap and easily administered with no obvious side-effects. It can be widely used in clinical practice.

Viral hepatitis B

More than 400 million people worldwide are chronically infected by the hepatitis B virus. The virus is responsible for more than 300000 cases of liver cancer every year and for similar numbers of gastrointestinal haemorrhage and ascites. Major breakthroughs have been achieved in diagnosis and treatment of this virus. Hepatitis B vaccine reduces incidence of liver cancer. As with hepatitis C, advances have been made in molecular virology, especially for naturally occurring and treatment-induced mutant viruses. The clinical significance of low viral load and genotypes are also under investigation. Currently available monotherapies-interferon, lamivudine, and adefovir dipivoxil-very rarely eradicate the virus, but greatly reduce its replication, necroinflammatory histological activity, and progression of fibrosis. Lamivudine, and presumably other nucleoside analogues, can reverse cirrhosis of the liver.

Detection of T lymphocyte subsets and mIL-2R on surface of PBMC in patients with hepatitis B

AIM: To study the levels of T lymphocyte subsets and membrane interleukin-2 receptor (mIL-2R) on surface of peripheral blood mononuclear cells (PBMCs) of patients with hepatitis B and its role in the pathogenesis of hepatitis B.

METHODS: The levels of T lymphocyte subsets and mIL-2R in PBMC before and after being stimulated with PHA were detected by biotin-streptavidin (BSA) technique in 196 cases of hepatitis B.

RESULTS: In patients with hepatitis B, the levels of CD₃⁺, CD₄⁺ cells, and the ratio of CD₄⁺ cells/CD₈⁺ cells were lower, but the level of CD₈⁺ cells was higher than those in normal controls (42.20 ± 6.01 vs 65.96 ± 6.54, 38.17 ± 5.93 vs 41.73 ± 6.40, 0.91 ± 0.28 vs 1.44 ± 0.31, 39.86 ± 6.36 vs 30.02 ± 4.54, P < 0.01). The total expression level of mIL-2R in PBMC before and after being stimulated with PHA was also lower than those in normal controls (3.47 ± 1.55 vs 4.52 ± 1.49, 34.03 ± 2.94 vs 37.95 ± 3.00, P < 0.01). In all the patients with hepatitis B, the levels of T lymphocyte subsets and mIL-2R in PBMC with HBV-DNA (+) were lower than those with HBV-DNA (-), which were significantly different (39.57 ± 7.11 vs 44.36 ± 5.43, 34.36 ± 7.16 vs 40.75 ± 5.87, 37.82 ± 6.54 vs 41.72 ± 6.21, 0.88 ± 0.33 vs 0.99 ± 0.27, 2.82 ± 1.62 vs 3.85 ± 1.47, 31.56 ± 3.00 vs 35.84 ± 2.83, P < 0.01). In addition, the levels of CD₃⁺, CD₄⁺, CD₈⁺ cells, the ratio of CD₄⁺ cells/CD₈⁺ cells and mIL-2R among different courses of hepatitis B were all significantly different (F = 3723.18, P < 0.01. F = 130.43, P < 0.01. F = 54.01, P < 0.01. F = 2.99, P < 0.05. F = 7.16, P < 0.01).

CONCLUSION: Both cellular and humoral immune functions are obviously in disorder in patients with hepatitis B, which might be closely associated with the chronicity in patients.

Molecular viral oncology of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer, but the third leading cause of cancer death, in the world, with more than 500,000 fatalities annually. The major etiology of HCC/liver cancer in people is hepatitis B virus (HBV), followed by hepatitis C virus infection (HCV), although nonviral causes also play a role in a minority of cases. Recent molecular studies confirm what was suspected: that HCC tissue from different individuals have many phenotypic differences. However, there are clearly features that unify HCC occurring in a background of viral hepatitis B and C. HCC due to HBV and HCV may be an indirect result of enhanced hepatocyte turnover that occurs in an effort to replace infected cells that have been immunologically attacked. Viral functions may also play a more direct role in mediating oncogenesis. This review considers the molecular and cellular mechanisms involved in primary hepatocellular carcinoma, using a viral perspective.

Hepatitis B virus reactivation in breast cancer patients receiving cytotoxic chemotherapy: a prospective study

Breast cancer is a rapidly increasing problem in many developing countries, and cytotoxic chemotherapy is now an integral part of its management. In several developing countries, the carriage of hepatitis B virus (HBV) in cancer patients may be as high as 12%, and such patients are at risk of developing fatal HBV reactivation during chemotherapy. HBV reactivation is well recognized in patients with hematological malignancies, but limited data are available on patients with other, more common, cancers, such as breast cancer. Recent data have suggested that increased viral replication, an indication of HBV reactivation, may precede clinical hepatitis. In the absence of serial HBV DNA monitoring, HBV reactivation during chemotherapy may have been underestimated. In this prospective study, breast cancer patients who were hepatitis B surface antigen (HBsAg) seropositive were followed up during chemotherapy. The main objectives were to determine the incidence of HBV reactivation in breast cancer patients undergoing conventional chemotherapy; to investigate whether "serial HBV DNA monitoring" improves the accuracy of diagnosing HBV reactivation when compared with previous schema that only measured HBV DNA at the time of clinical hepatitis ("conventional monitoring"); and to assess the clinical consequences as a result of developing the condition. The secondary objective was to identify risk factors associated with this condition. Over an 18-month period, 41 patients were studied. Ten developed HBV reactivation by conventional monitoring criteria, but with serial HBV DNA monitoring, seven additional patients were diagnosed when increased HBV DNA levels were detected before, but not concomitant with, clinical hepatitis. Thus, a total of 17 patients (41%) developed HBV reactivation. Premature termination of chemotherapy or delay in treatment schedules occurred in 71% of the patients who developed viral reactivation, as compared with 33% in those who did not develop the condition (P = 0.019). No risk factors associated with the development of HBV reactivation could be identified. Serial monitoring of HBV DNA, in addition to liver function, increases the sensitivity of diagnosing of HBV reactivation, and helps explain some cases that would otherwise be labeled as "cryptogenic hepatitis," for which concomitant HBV DNA measured at the time of hepatitis was undetectable. The present study highlights the importance of monitoring HBsAg-seropositive patients who are receiving chemotherapy for common solid tumors such as breast cancer.

Hepatitis B virus-induced defect of monocyte-derived dendritic cells leads to impaired T helper type 1 response in vitro: mechanisms for viral immune escape

Dendritic cells (DC) are the most potent antigen-presenting cells and play a central role in the induction of antiviral immune responses. Recently, we have shown that monocyte-derived DC (MoDC) from patients with chronic hepatitis B virus (HBV) infection are functionally impaired. In our present study MoDC from healthy subjects were propagated in vitro and inoculated with HBV particles to investigate the precise mechanisms that underly MoDC dysfunction. T-cell proliferation assays revealed an impaired allostimulatory capacity of HBV-inoculated MoDC (HBV-MoDC) as well as a lower potential of stimulating autologous T cells against a recall antigen in comparison to control-MoDC. Interleukin-2, tumour necrosis factor-alpha and interferon-gamma production by T cells in proliferation assays with HBV-MoDC was significantly lower than with control-MoDC and correlated with lower IL-12 production in HBV-MoDC cultures. The presence of the nucleoside analogue lamivudine (3TC), an inhibitor of HBV replication, restored impaired allostimulatory function of HBV-MoDC and up-regulated major histocompatibility complex class II expression. These results show that HBV infection compromises the antigen-presenting function of MoDC with concomitant impairment of T helper cell type 1 responses. This may play an important role for viral immune escape leading to chronic HBV infection. However, 3TC treatment can overcome HBV-MoDC-related T-cell hyporeactivity and this underscores its important role in enhanced immune responses to HBV.

Kinetics of the immune response during HBV and HCV infection

The innate immune system has a role not only in protecting the host during the initial period of virus infection, but also in shaping the nature of the adaptive immune response. In this review, we follow the kinetics of the virologic and immunologic events occurring from the time of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. We primarily discuss how the early events after infection might influence the development of the adaptive immune response in these 2 important viral infections and how new strategies for more efficient preventive and therapeutic vaccines can be derived from this knowledge.

HBcAg-specific CD8 T cells play an important role in virus suppression, and acute flare-up is associated with the expansion of activated memory T cells

We analyzed the prevalence and longitudinal fluctuation of hepatitis B virus (HBV)-specific CD8 T cells in chronic HBV infection using an HLA-A2-HBc18-27 tetramer. Thirty-five HLA-A2-positive patients with chronic HBV infection were divided into 17 HBe antigen (HBeAg)-positive and 18 anti-HBe antibody (anti-HBe)-positive patients. Five HLA-A2-positive normal subjects, five HLA-A2-negative patients with chronic HBV infection, and two HLA-A2-positive patients with acute HBV infection were included as controls. HBc18-27-specific CD8 T cells (c18-27-CD8Ts) were detected at a significantly higher prevalence in patients with anti-HBe (6/18) than in those with HBeAg (1/17), and their frequency reached 0.28% of the total CD8 T cells. The prevalence was significantly higher in patients with HBV DNA below 4.0 log genome equivalents (LGE)/ml (5/12) than in those with HBV DNA above 4.0 LGE/ml (2/23). The frequency of c18-27-CD8Ts was consistently higher in liver-infiltrating lymphocytes, ranging from 0.18 to 1.28%, than in autologous peripheral blood lymphocytes. Longitudinal analysis of patients with acute flare-up demonstrated that the elevation of alanine aminotransferase (ALT) was intimately associated with the expansion of c18-27-CD8Ts. Phenotypic analysis revealed that most c18-27-CD8Ts during acute flare-up expressed HLA-DR and CCR5, while those during low-ALT periods showed low expression. Furthermore, most liver-infiltrating c18-27-CD8Ts were positive for HLA-DR and CCR5, suggesting selective recruitment of activated c18-27-CD8Ts into the liver. In conclusion. HBV-specific CD8 T cells play an important role in the suppression of virus replication, and acute flare-up is associated with the expansion and activation of HBV-specific memory cells.

The role of intrahepatic immune effector cells in inflammatory liver injury and viral control during chronic hepatitis B infection

Cytotoxic T lymphocytes (CTL) and Kupffer cells play an important role in the immune control of hepatitis B virus (HBV), but may also induce liver injury during infection. We investigated the intrahepatic immune response in liver biopsies of chronic HBV patients in relation to inflammatory liver injury and viral control. Forty-seven liver biopsies from patients with chronic HBV with varying degrees of inflammation (ALT values) were selected. Acute hepatitis and normal liver specimens served as controls. Immune effector cells, cytotoxic effector molecules and cytokine producing cells were quantified after immunohistochemical staining in lobular and portal areas of the biopsies. The intralobular number of CD8+ T-lymphocytes was significantly decreased in biopsies of patients with high ALT (r = -0.54; P < 0.001). Higher ALT-values were correlated with increased numbers of granzyme+ cells in portal areas (r = 0.65; P < 0.001) and higher numbers of intralobular Fas-L+ cells (r = 0.32; P = 0.05). Fas-L was expressed on Kupffer and lymphoid cells. More intralobular CD8+ T-lymphocytes were found in HBeAg- than in HBeAg+ patients (P = 0.002). But IFN-gamma and TNF-alpha producing cells were observed sporadically in chronic HBV patients. Hence, in chronic HBV infection, low viral replication and HBeAg negativity is related to increased presence of intralobular CD8+ T-lymphocytes. Persistence of the virus may be caused by the absence of cells producing anti-viral cytokines in the liver. Inflammatory liver injury during chronic HBV infection is probably not the result of increased numbers of infiltrating CD8+ T-lymphocytes, but of Fas-L expression by Kupffer cells and increased cytolytic activity of cells in portal areas.

Molecular epidemiology and immunology of hepatitis B virus infection - an update

Hepatitis B virus (HBV) continues to be one of the most important viral pathogens in humans. This review provides an update on the molecular epidemiology and immunology of HBV infection. DNA sequencing has allowed replacement of the initial serotypic classification of HBV strains by a more systematic genotype system that currently consists of 7 members (genotypes A-G). More recently, sequence analysis of virus isolates from many individual patients has revealed the occurrence of certain mutational hot spots in the genome, some of which appear to correlate with the patient's immunological and/or disease status; however, cause and effect are not always easily discernible. This holds particularly for the issue of whether virus variants exist that have, per se, an increased pathogenic potential; due to the scarcity of appropriate experimental in vivo models, such hypotheses are difficult to prove. Similarly, because of the compact organization of the HBV genome, almost every single mutation may have pleiotropic phenotypic effects. Nonetheless, there is accumulating evidence that at least some frequently observed mutations are causally related to viral escape from selective pressures, such as the presence of antibodies against dominant B cell epitopes, or drugs that inhibit the viral reverse transcriptase; possibly, this is also true for the cellular immune response. Therefore, despite the availability of an effective prophylactic vaccine, further extensive efforts are required to monitor the emergence of vaccination- and therapy-resistant HBV variants and to prevent their spread in the general population.

Role of type 1 versus type 2 immune responses in liver during the onset of chronic woodchuck hepatitis virus infection

Immune response messenger RNAs (mRNA) were compared in liver during self-limited (resolved) and chronic neonatal woodchuck hepatitis virus (WHV) infection. At week 14 postinfection (mid-acute phase), mRNAs for leukocyte markers (CD3, CD4, CD8), type 1 cytokines and related transcription factors (IFN-gamma, TNF-alpha, STAT4, T-bet), and IL-10 were increased in livers from resolving infections, but mRNAs of other type 1 (IL-2) and type 2 (IL-4, STAT6, and GATA3 markers remained at baseline levels. Increased coexpression of IFN-gamma and TNF-alpha mRNAs correlated in most cases with lower levels of intrahepatic WHV covalently closed circular DNA (cccDNA). At the same time point postinfection, livers from woodchucks that eventually progressed to chronic infection had baseline or slightly elevated levels of CD and type 1 mRNAs, which were significantly lower (or elevated less frequently) compared with resolving woodchucks. Earlier, at week 8, there were no differences between the two outcome settings. During these early time points and at a later stage in chronic infection (15 months), type 2 mRNAs in carrier liver remained at baseline levels or, when elevated, were never in excess of those in resolving woodchucks. In conclusion, the onset and maintenance of neonatal chronic WHV infection are not associated with antagonistic type 2 immunoregulation of type 1 responses in liver. Accordingly, chronicity develops in association with a primary deficiency in the intrahepatic CD responses, especially involving CD8(+) T lymphocytes, and in both extracellular (cytokine) and intracellular (transcriptional) type 1 response mediators. This has relevant implications for future treatment of chronic hepatitis B virus (HBV) infection in humans.

CD8(+) T cells mediate viral clearance and disease pathogenesis during acute hepatitis B virus infection

Although the CD4(+)- and CD8(+)-T-cell responses to the hepatitis B virus (HBV) are thought to be crucial for the control of HBV infection, the relative contribution of each T-cell subset as an effector of viral clearance is not known. To examine this question, we monitored the course of HBV infection in control, CD4-depleted, and CD8-depleted chimpanzees. Our results demonstrate that CD8(+) cells are the main effector cells responsible for viral clearance and disease pathogenesis during acute HBV infection, and they suggest that viral clearance is mediated by both noncytolytic and cytolytic effector functions of the CD8(+)-T-cell response.

A prospective study characterizing full-length hepatitis B virus genomes during acute exacerbation

BACKGROUND & AIMS

Hepatitis B virus (HBV) evolves rapidly in patients with chronic hepatitis B, and HBV variation may trigger acute exacerbation. To study this relationship, we investigated full-length viral sequences before, during, and after exacerbation.

METHODS

We prospectively studied 14 patients with exacerbation of hepatitis B, either spontaneously (n = 4) or after receiving various medical interventions (n = 10), and measured their serum alanine aminotransferase (ALT) and HBV DNA levels monthly. Full-length HBV genomes at baseline, at the peak of serum viral load, at ALT peak, and after ALT peak were obtained by polymerase chain reaction, sequenced, and compared. Replication activities of serial HBV variants were assayed by in vitro transfection.

RESULTS

Serum viral load was increased in all exacerbations. Viral peak preceded ALT peak in 13 (93%) of the 14 patients. At virologic peak, 12 patients (86%) harbored viral genome identical to the corresponding baseline genome. At and after ALT peak, 9 (64%) and 7 (50%) of the viral genomes remained identical to baseline, respectively. Mean nucleotide change per genome was 0.2 at virologic peak but increased to 4.4 and 8.1 at and after ALT peak, respectively. The replication potential of the viral variant that emerged during or after exacerbation was equivalent to that at baseline.

CONCLUSIONS

Most exacerbations were preceded by an upsurge of serum HBV identical to the preexisting HBV strain. After exacerbation, about half of the patients were repopulated by a different viral variant, which was likely a result of immune selection.

Intrahepatic CD8 T-lymphocytes and HBV core expression in relation to response to antiviral therapy for chronic hepatitis B patients

Recognition of HBV-infected hepatocytes by CD8 T-lymphocytes is important for viral clearance. Expression of hepatitis B core antigen (HBcAg) in HBV-infected hepatocytes can trigger this antiviral T-cell response. The intrahepatic CD8 T-lymphocytes and HBcAg expression were investigated in relation to response to antiviral therapy. Forty chronic HBeAg-positive patients treated with either lamivudine (n = 20) or interferon-alpha (n = 20) were investigated. Ten patients from each treatment group exhibited a response. Liver biopsies were carried out before and after therapy. CD8 T-lymphocytes and HBcAg expression were detected by immunohistochemistry. The number of pretreatment intrahepatic CD8 T-lymphocytes was significantly higher in responders (P = 0.008). In responders baseline nuclear HBcAg expression tended to be lower (P = 0.09). Cytoplasmic expression was not significantly different between responders and non-responders (P = 0.46). The number of CD8 T-lymphocytes correlated with cytoplasmic HBcAg (r(s) = 0.31; P = 0.04); CD8 T-lymphocytes were situated in clusters of hepatocytes with cytoplasmic HBcAg. Longitudinal analysis showed a significant reduction of CD8 T-lymphocytes after treatment in responders (P < 0.001). Multivariate analysis revealed pretreatment CD8 T-lymphocytes and age as independent prognostic factors for response (n = 40). The number of pretreatment CD8 T-lymphocytes was the only independent prognostic indicator for response to interferon-alpha (P = 0.03); it was of borderline significance for lamivudine therapy (P = 0.06). It is concluded that the number of pretreatment intrahepatic CD8 T-lymphocytes is an important predictor of response to HBV therapy with either interferon-alpha or lamivudine. Response to therapy led to a significant reduction of intrahepatic CD8 T-lymphocytes. Co-localisation of CD8 T-lymphocytes and HBcAg-positive hepatocytes suggests antiviral activity predominantly at the site of maximum HBV replication.

HIV-1, hepatitis B virus, and risk of liver-related mortality in the Multicenter Cohort Study (MACS)

BACKGROUND

Although coinfection with HIV-1 and hepatitis B virus (HBV) is common, few long-term studies on liver-disease mortality in coinfected people have been undertaken. Our aim was to examine liver-related mortality among people at risk for HIV-1 and HBV infections.

METHODS

We used data from a multicentre, prospective cohort study to classify 5293 men who had sex with men, according to their HIV-1 antibody status, ascertained semiannually, and their hepatitis-B surface antigen status (HBsAg), which we ascertained at baseline. Mortality rates were estimated in terms of person-years and Poisson regression methods were used to test for significance of relative risks.

FINDINGS

326 (6%) men were HBsAg positive, of whom 213 (65%) were HIV-1 positive. Of the 4967 HBsAg negative men, 2346 (47%) were infected with HIV-1. The liver-related mortality rate was 1.1/1000 person years, and was higher in men with HIV-1 and HBsAg (14.2/1000) than in those with only HIV-1 infection (1.7/1000, p<0.001) or only HBsAg (0.8/1000, p<0.001). In coinfected individuals, the liver-related mortality rate was highest with lower nadir CD4+ cell counts and was twice as high after 1996, when highly active antiretroviral therapy (HAART) was introduced.

INTERPRETATION

Individuals coinfected with HIV-1 and HBV, especially those with low CD4+ nadir counts, are at increased risk for liver-related mortality, underscoring the importance of prevention, identification, and comprehensive management of hepatitis B in people infected with HIV-1.

Virus-specific CD8+ lymphocytes share the same effector-memory phenotype but exhibit functional differences in acute hepatitis B and C

Hepatitis B and hepatitis C viruses (HBV and HCV) are both noncytopathic and can cause acute and chronic infections of the liver. Although they share tropism for the same organ, development of chronic hepatitis is much more frequent following HCV infection, suggesting different mechanisms of viral persistence. In this study, we show that circulating HBV- and HCV-specific tetramer-positive CD8 cells during the acute phase of hepatitis B and C belong almost entirely to an effector-memory subset (CCR7(-) CD45RA(-)). Despite this phenotypic similarity, HBV- and HCV-specific CD8 cells show striking functional differences. HBV-specific tetramer-positive CD8 cells express high perforin content ex vivo, expand vigorously, and display efficient cytotoxic activity and gamma interferon (IFN-gamma) production upon peptide stimulation. A comparable degree of functional efficiency is maintained after the resolution of hepatitis B. In contrast, HCV-specific CD8 cells in the acute phase of hepatitis C express significantly lower levels of perforin molecules ex vivo and show depressed CD8 function in terms of proliferation, lytic activity, and IFN-gamma production, irrespective of the final outcome of the disease. This defect is transient, because HCV-specific CD8 cells can progressively improve their function in patients with self-limited hepatitis C, while the CD8 function remains persistently depressed in subjects with a chronic evolution.

Reduction in the circulating pDC1/pDC2 ratio and impaired function of ex vivo-generated DC1 in chronic hepatitis B infection

Dendritic cells (DCs) induce and regulate T-cell-mediated immune responses. Circulating precursor (p)DC1 and pDC2 from patients with chronic hepatitis B virus (HBV) infection were quantified by flow cytometry. To assess their function, DC1 were cultured from patients and compared to those of healthy volunteers. HBV patients exhibited a significant decrease in the proportion of freshly isolated pDC1 to pDC2. DC1 propagated from patients showed lower expression of costimulatory molecules and impaired allostimulatory capacity in comparison to controls. After exposure to proinflammatory cytokines, expression of costimulatory molecules, secretion of interleukin-12 (IL-12) and allostimulatory properties increased, but capacity for T-cell stimulation and IL-12 production remained inferior to that of control DCs. HBV-DNA was amplified by polymerase chain reaction in DC1 cultured from all patients. Viral particles were visible in DC1 by electron microscopy. These results suggest that intracellular presence of HBV impairs DC1 functional maturation and subsequent deficits in T-lymphocyte activation may contribute to viral persistence.

Viral determinants and host immune responses in the pathogenesis of HBV infection

Hepatitis B virus (HBV) is a virus that infects about 350,000,000 people worldwide with a clinical spectrum of acute hepatitis, the healthy carrier state, cirrhosis and hepatocellular carcinoma (HCC). The outcome of HBV infection is the result of complicated viral-host interactions. As in other infections with non-cythopatic viruses, the immune response is thought to play a crucial role in disease pathogenesis but there is increasing evidence that a variety of viral mechanisms, some depending on the function of virally encoded proteins, have a profound impact on the infected hepatocytes, the liver microenvironment, and host anti-viral responses. Indeed, the virus has evolved multiple mechanisms to ensure its success in infecting a susceptible host. The essential aspects of the life cycle of HBV and the host immune response are reviewed and recent new developments in the molecular virology of HBV, including experimental animal models, in the role of accessory viral proteins in disease pathogenesis and HCC development and in the characterisation of the T cell response in the control of HBV infection, are highlighted.

Biology and significance of T-cell apoptosis in the liver

The liver has emerged as an organ with distinct immunological properties. In this review, we summarize evidence that shows that the liver can remove apoptotic, or non-apoptotic but activated, CD8+ T cells from the circulation and induce apoptosis in these activated T cells by either active or passive mechanisms. Hepatitis viruses, particularly hepatitis C virus, often establish persistent infection. We review evidence that suggests that these viruses exploit intrahepatic tolerance mechanisms to protect themselves from immune attack.

Control or persistence of hepatitis B virus: the critical role of initial host-virus interactions

Following infection with hepatitis B virus (HBV), the period before symptomatic disease is now recognized as a time of dynamic interaction between virus and host. Recent work has shown that this period is the phase of infection during which maximal changes in virus replication and the activation of critical components of the immune system occurs. This suggests that the different outcomes following exposure might be determined during the early phase of infection, before the onset of clinical disease. The hypothesis that small differences in the dynamic relationship between host and virus, such as in the kinetics of HBV replication, may influence the final outcome of infection, will be discussed.

Deficiencies in the acute-phase cell-mediated immune response to viral antigens are associated with development of chronic woodchuck hepatitis virus infection following neonatal inoculation

In vitro proliferation of peripheral blood mononuclear cells was used to measure virus-specific cell-mediated immunity (vCMI) following neonatal woodchuck hepatitis virus (WHV) infection. Fifteen neonates were inoculated with the W8 strain of WHV. In 11, infection was resolved, and 4 became chronic carriers. Nineteen neonates were inoculated with the W7 strain and all became chronic carriers. Seven age-matched uninfected woodchucks served as controls. Virologic and vCMI profiles among the W8 and W7 infections were compared and related to the outcome of infection. Resolving woodchucks had robust, acute-phase vCMI to WHV antigens (core, surface, and x) and to several nonoverlapping core peptides. The acute-phase vCMI was associated temporally with the clearance of viral DNA and of surface antigen from serum at 14 to 22 weeks postinfection. In contrast, in approximately half of the W8 and W7 infections that progressed to chronicity, no significant acute-phase vCMI was detected. In the remaining carriers, acute-phase vCMI was observed, but it was less frequent and incomplete compared to that of resolved woodchucks. Serum viral load developed less rapidly in those carriers that had evidence of acute-phase vCMI, but it was still increased compared to that of resolving woodchucks. Thus, vigorous and multispecific acute-phase vCMI was associated with resolution of neonatal WHV infection. Absent or incomplete acute-phase vCMI was associated with the progression to chronic infection. By analogy, these results suggest that the onset of chronic hepatitis B virus (HBV) infection in humans may be associated with deficiencies in the primary T-cell response to acute HBV infection.

The role of hepatitis B virus-specific memory CD8 T cells in the control of viral replication

BACKGROUND/AIMS

The aim of this study is to clarify the differences of host immune responses between acute self-limited and chronic persistent hepatitis B virus (HBV) infections by quantitative and qualitative analysis of HLA-A*2402-restricted HBV-specific CD8+ T cells.

METHODS

HBV-specific CD8+ T cells in peripheral blood mononuclear cells (PBMCs) from patients infected with HBV were analyzed by flow cytometry using two HLA-A*2402-HBV peptide tetrameric complexes.

RESULTS

High numbers of HBV-specific CD8+ T cells were detected in acute phase PBMCs from most individuals with acute HBV infection while the number of these cells was greatly reduced in recovery phase PBMCs. HBV-specific CD8+ T cells were not detected in PBMCs from individuals with chronic HBV infection except for one patient during acute exacerbation. HBV-specific CD8+ T cells were induced by in vitro peptide stimulation in PBMCs from chronic HBV carriers with a low level of serum HBV-DNA but not from those with a high level of serum HBV-DNA. CD28CD45RA phenotype analysis showed that HBV-specific CD8+ T cells in acute phase PBMCs predominantly express a memory T cell phenotype.

CONCLUSIONS

HBV-specific memory CD8+ T cells may play a crucial role in complete clearance of HBV from patients with acute HBV hepatitis.