Immunopathogenesis of hepatitis B virus recurrence after liver transplantation

What is expected from the pathologist in the diagnosis of viral hepatitis?

The clinician expects from the pathologist a clinically relevant diagnosis on the basis of liver biopsy interpretation. Today, a liver biopsy, as invasive procedure, is only justified when a significant benefit for the patient can be expected particularly with respect to the clinical management. Consequently, liver biopsy is usually not required in uncomplicated acute viral hepatitis. It is, however, an important diagnostic tool in chronic hepatitis and in transplanted liver to confirm the clinical diagnosis and to assess stage and grade of necroinflammation, treatment efficiency, and concurrent diseases. The diagnosis of liver disease is based on teamwork between clinician and pathologist. Evaluation of the biopsy in the clinical context requires clinical information and appropriate size and handling of the biopsy specimen. Aim of this review is the discussion of morphologic features of acute and chronic viral hepatitis with regard to their clinical relevance.

Hepatitis B virus-specific CD4 T cell immunity after liver transplantation for chronic hepatitis B

Cellular immunity plays an important role in the long-term control of hepatitis B virus (HBV) infection. We studied the changes in HBV-specific CD4 T cell immunity after orthotopic liver transplantation (OLT) for chronic hepatitis B under antiviral prophylaxis. T cell proliferation and interferon-gamma production in response to in vitro challenge with HBV-encoded antigens were tested in 40 OLT recipients without HBV recurrence and in 12 OLT recipients with HBV recurrence more than 1 year after transplantation, and they were compared to 40 subjects with chronic HBV infection and to 23 subjects with self-limited HBV infection. The frequency and magnitude of the HBV-specific CD4 T cell response were significantly lower in 40 OLT recipients with HBV clearance, but the T cell reactivity to mitogen (phytohemagglutinin) and recall antigen (tetanus toxoid) was maintained. In the 12 OLT recipients with HBV recurrence, however, the HBV-specific T cell immunity was enhanced to a level comparable to that of patients with chronic hepatitis B, and the level was dependent on the serum viral load. In conclusion, HBV-specific CD4 T cell immunity is antigen-driven and evanesces with viral clearance, hence providing a favorable milieu for reactivation once prophylaxis is withdrawn. The cellular immunity in recipients with recurrence is not significantly different from that of individuals with chronic hepatitis B.

Sustained and focused hepatitis B virus nucleocapsid-specific T-cell immunity in liver transplant recipients compared to individuals with chronic and self-limited hepatitis B virus infection

Hepatitis B virus (HBV) recurrence after orthotopic liver transplantation (OLT) is associated with poor graft- and patient-survival. Treatment with HBV-specific immunoglobulins (HBIG) in combination with nucleos(t)ide analogs is effective in preventing HBV reinfection of the graft and improving OLT outcome. However, the role of HBV-specific cellular immunity in viral containment in immune suppressed patients in general and in OLT recipients in particular is unclear. To test whether or not OLT recipients maintain robust HBV-specific cellular immunity, the cellular immune response against HBV was assessed in 15 OLT recipients and 27 individuals with chronic and 24 subjects with self-limited HBV infection, respectively; using an overlapping peptide set spanning the viral nucleocapsid- and envelope-protein sequences. The data demonstrate that OLT recipients mounted fewer but stronger clusters of differentiation (CD)8 T cell responses than subjects with self-limited HBV infection and showed a preferential targeting of the nucleocapsid antigen. This focused response pattern was similar to responses seen in chronically infected subjects with undetectable viremia, but significantly different from patients who presented with elevated HBV viremia and who mounted mainly immune responses against the envelope protein. In conclusion, virus-specific CD4 T cell-mediated responses were only detected in subjects with self-limited HBV infection. Thus, the profile of the cellular immunity against HBV was in immune suppressed patients similar to subjects with chronic HBV infection with suppressed HBV-DNA.

Recipient cytotoxic T lymphocyte antigen-4 +49 G/G genotype is associated with reduced incidence of hepatitis B virus recurrence after liver transplantation among Chinese patients

BACKGROUND

Single-nucleotide polymorphisms (SNP) of two-gene locus cytotoxic T lymphocyte antigen-4 (CTLA-4) +49 and CD86 +1057 were previously reported to influence the outcome of liver transplantation (LT) with respect to allograft acceptance. SNP at CTLA-4 +49 was also suggested to be associated with the individual difference in the clearance of hepatitis B virus (HBV). However, their influence on the incidence of post-LT HBV reinfection was not clear. With the increasing knowledge of costimulatory mechanisms on LT and host immune response, we designed this study to investigate the relationship between different alleles as well as genotypes at these two locations and HBV reinfection after LT.

METHODS

Genomic DNA from 167 LT recipients with HBV-related diseases was genotyped for CTLA-4 +49 and CD86 +1057 genomic polymorphisms using a sequence-specific primer-polymerase chain reaction (PCR-SSP). HBV recurrence was diagnosed based on the serological and pathological finding of HBV DNA and HBsAg.

RESULTS

The present study indicated that the recipients with CTLA-4 +49 GG genotype had a reduced risk (6.67%) of HBV recurrence compared with non-CTLA-4 +49 GG-carrying individuals (20.7%) (relative risk 3.098) (P=0.032). The allelic frequency of CTLA-4 +49 G was also significantly lower in patients with HBV recurrence, compared with that in patients without HBV recurrence (P=0.013, odds ratio 2.176, 95% confidence interval 1.170-4.046). However, no significant association was found between CD86 +1057 and HBV recurrence.

CONCLUSION

Our result on CTLA-4 +49 A/G polymorphism indicated that the CTLA-4 +49 GG genotype was related to a reduced risk in the incidence of HBV recurrence.

The immunology of hepatitis B

The hepatitis B virus (HBV) is an enveloped, hepatotrophic, oncogenic hepadnavirus that is noncytopathic for hepatocytes. HBV infection results in a variety of outcomes that are determined by the quality, quantity, and kinetics of the host innate and adaptive immune responses. Whether HBV infection is cleared or persists as a progressive or nonprogressive liver disease is determined by both viral and host factors. Replicative intermediates can persist in the liver under immunologic control after resolution of acute or chronic hepatitis B, conferring a risk for reactivation following a course of immunosuppression or chemotherapy.

Histologic findings in recurrent HBV

1. The histopathologic presentation of hepatitis B (HB) infection in liver allografts is generally similar to that seen in the nonallografts. 2. An atypical pattern of recurrent HB, i.e., fibrosing cholestatic hepatitis (FCH) occurs in a small number of patients. These patients present with a severe cholestatic syndrome, which may clinically resemble acute or chronic rejection. 3. There are several other possible causes of acute and chronic hepatitis in liver allografts that may need to be considered. 4. Hepatitis B virus (HBV) infection in the liver allograft can easily be confirmed by performing immunohistochemical stains for hepatitis B surface antigen (HBsAg) and hepatitis B core antigen (HBcAg). The expression pattern of these HBV antigens varies and is sometimes helpful in determining whether the liver injury is mainly from the HBV or from other causes in coexistence with the HBV infection. 5. Histological grading of the necroinflammatory activity and staging of the fibrosis should only be applied when the changes are related to the recurrent HB. 6. The pathology of liver transplantation is complex; therefore, clinical correlations remain extremely important in arriving at the final and correct diagnosis.

Possible role of retinoids in hepatitis B virus-associated liver damage

Liver damage following hepatitis B virus (HBV) infection may be due to the action of retinoids as modulators of viral replication. The reduced rate of survival of liver grafts in patients with HBV infection could also be due to the continued presence of the virus, stimulated by retinoids in the graft tissue. Subject to obtaining empirical support for this hypothesis, the use of retinoid-blocking agents could be explored to reduce the risk of liver damage in HBV infection and to enhance the survival of liver grafts. Continued use of such agents may need to be used in conjunction with anti-viral modalities such as HBV hyperimmune globulin and lamivudine to prevent recurrent liver damage and to increase the long-term viability of the graft.

In vitro and in vivo infectivity and pathogenicity of the lymphoid cell-derived woodchuck hepatitis virus

Woodchuck hepatitis virus (WHV) and human hepatitis B virus are closely related, highly hepatotropic mammalian DNA viruses that also replicate in the lymphatic system. The infectivity and pathogenicity of hepadnaviruses propagating in lymphoid cells are under debate. In this study, hepato- and lymphotropism of WHV produced by naturally infected lymphoid cells was examined in specifically established woodchuck hepatocyte and lymphoid cell cultures and coculture systems, and virus pathogenicity was tested in susceptible animals. Applying PCR-based assays discriminating between the total pool of WHV genomes and covalently closed circular DNA (cccDNA), combined with enzymatic elimination of extracellular viral sequences potentially associated with the cell surface, our study documents that virus replicating in woodchuck lymphoid cells is infectious to homologous hepatocytes and lymphoid cells in vitro. The productive replication of WHV from lymphoid cells in cultured hepatocytes was evidenced by the appearance of virus-specific DNA, cccDNA, and antigens, transmissibility of the virus through multiple passages in hepatocyte cultures, and the ability of the passaged virus to infect virus-naive animals. The data also revealed that WHV from lymphoid cells can initiate classical acute viral hepatitis in susceptible animals, albeit small quantities (approximately 10(3) virions) caused immunovirologically undetectable (occult) WHV infection that engaged the lymphatic system but not the liver. Our results provide direct in vitro and in vivo evidence that lymphoid cells in the infected host support propagation of infectious hepadnavirus that has the potential to induce hepatitis. They also emphasize a principal role of the lymphatic system in the maintenance and dissemination of hepadnavirus infection, particularly when infection is induced by low virus doses.

Protection or damage: a dual role for the virus-specific cytotoxic T lymphocyte response in hepatitis B and C infection?

During infection with hepatitis B or C viruses, cytotoxic T lymphocytes (CTLs) have been implicated as both the mediators of protection and the principal effectors of liver pathology. Recent studies have allowed an investigation of the relationship between virus-specific CTL responses, liver damage and viral replication. In the presence of an efficient virus-specific CTL response, a scenario is emerging where inhibition of viral replication can be independent of liver pathology. We discuss the possibility that an inadequate CTL response--unable to control viral replication--may contribute to liver pathology not only directly but also via the recruitment of non-virus-specific T cells.

Protection or damage: a dual role for the virus-specific cytotoxic T lymphocyte response in hepatitis B and C infection?

During infection with hepatitis B or C viruses, cytotoxic T lymphocytes (CTLs) have been implicated as both the mediators of protection and the principal effectors of liver pathology. Recent studies have allowed an investigation of the relationship between virus-specific CTL responses, liver damage and viral replication. In the presence of an efficient virus-specific CTL response, a scenario is emerging where inhibition of viral replication can be independent of liver pathology. We discuss the possibility that an inadequate CTL response--unable to control viral replication - may contribute to liver pathology not only directly but also via the recruitment of non-virus-specific T cells.