Adoptive transfer of donor-derived immunity by liver transplantation: a potential avenue to prevent hepatitis B virus reinfection

Reversal of B-cell hyperactivation and functional impairment is associated with HBsAg seroconversion in chronic hepatitis B patients

B cells play an important role in the clearance of hepatitis B virus (HBV) and protection against reinfection. However, the functional characteristics of these cells that are associated with the outcome of chronic HBV infection remain unknown. We comprehensively investigated the frequency, phenotype, and function of peripheral B-cell subsets from CHB patients in different phases: immune tolerance (IT), immune activation (IA), immune clearance (IC), responders with HBsAg seroconversion (resolved patients, RP), and healthy controls (HC). IA patients displayed lower percentages of peripheral blood memory B cells compared with the other groups. Overall polyclonal activation of B cells, indicated by higher levels of activation markers and secretion of IgG and IgM, was observed in IA patients. This B-cell hyperactivation could be induced by increased IFN-α and soluble CD40 ligands in IA patients. Notably, the expression of the co-stimulator molecule CD80 and serum HBsAb and the frequency of HBsAg-specific B cells were significantly decreased in IT, IA, and IC patients compared with HC subjects. More importantly, the B-cell hyperactivation, co-stimulatory molecule downregulation and HBsAg-specific B-cell impairment were reversed in RP patients. The reversal of B-cell hyperactivation and functional impairment is associated with HBsAg seroconversion in chronic hepatitis B patients.

Cellular and humoral immune response to a third generation hepatitis B vaccine

Liver transplantation is often the ultimate option of therapy for chronically hepatitis B virus (HBV) infected patients. Adoptive transfer of HBV immunity with the liver after vaccination of living liver donors (LLD) could be a new approach to prevent reinfection in the recipients. The time to achieve HBV immunity in LLD is usually short (1-2 months). Therefore, we established a short time immunization protocol (four injections in 2 weeks intervals) using Hepimmune, a recombinant vaccine that contains the L, M and S proteins of HBV. We examined cellular and humoral immune responses after immunization with Hepimmune and compared its immunogenicity to that of a standard HBV vaccine containing only the S protein (HBVAXPRO). Cellular immunity was measured by interferon (IFN)-gamma ELISpot and proliferation assay. HBV-specific T cells were detectable in the Hepimmune group after the second and in the standard group after the third vaccination. IFN-gamma production of T cells was significantly higher (P < 0.001) after the third vaccination with Hepimmune. Proliferative responses were also significantly (P < 0.01) higher in the Hepimmune group after the second to fourth vaccination. The humoral immune response could already be detected after the first immunization in nine of 15 Hepimmune vaccinated test persons while it was only observed in one of 15 probands of the later group. Titres differed significantly (P < 0.01) following all four vaccinations. Thus, Hepimmune appears to be a good candidate for short time immunization protocols.

Identification of hepatitis B virus-specific lymphocytes in human liver grafts from HBV-immune donors

Both animal and human studies have demonstrated the adoptive transfer of immunity against hepatitis B virus (HBV) through liver transplantation that may be attributed to the presence of HBV-specific immunocompetent cells of donor origin in liver grafts. In this study, we characterized the resident lymphocytes in 41 human liver grafts by immunohistochemical staining and flow cytometry and directly identified the intragraft HBV-specific lymphocytes in relation to the donor's and subsequent recipient's immunity using enzyme-linked immunospot assay. A significant number of HBV-specific T and B cells were detectable in 59.4% (19/32) and 28.1% (9/32), respectively, of liver grafts from HBV-immune donors. The presence of various HBV-specific lymphocytes was closely associated with each other and with a higher serum titer of antibody against hepatitis B surface antigen (anti-HBs) in donors (P < 0.05). After liver transplantation, 17 of 35 (48.6%) patients with chronic HBV infection showed a spontaneous anti-HBs production, which was significantly associated with a higher number of donor-derived T lymphocytes specific for hepatitis B surface antigen (P = 0.043). In conclusion, the presence of considerable numbers of donor-derived HBV-specific immunocompetent cells in grafts may account for the adoptive transfer of HBV immunity through liver transplantation.

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Adoptive transfer of immunity: a new strategy to interfere with severe hepatitis virus reinfection after woodchuck liver transplantation

BACKGROUND

The effective transfer of humoral immunity to hepatitis B virus was first demonstrated after clinical and experimental bone marrow transplantation. This strategy is now evaluated in the woodchuck transplantation model, in which protection from reinfection can be tested.

METHODS

Animals negative for woodchuck hepatitis virus (WHV) (n = 3) were vaccinated using plasmids expressing woodchuck hepatitis virus surface (WHs), woodchuck hepatitis virus core (WHc), and woodchuck interferon-gamma in combination with a protein vaccine (WHs antigen [Ag]) three times before liver donation. Control animals (n= 4) received the liver from non-immunized donors. Chronic WHV carriers served as recipients. The viral load in serum and liver tissue was monitored pretransplant and posttransplant for up to 11 weeks by dot blot, Northern blot, Southern blot, and immunohistochemistry for WHc and WhsAg.

RESULTS

Donor vaccination was effective, as indicated by the development of anti-WHc and anti-WHs antibodies. Transplanting the livers of these donors resulted in a reduction of viral load in two of three animals. No viral DNA was detected in repeated serum samples by dot-blot hybridization technique. However, polymerase chain reaction for viral DNA extracted from serum was always positive. WHV replication intermediates and WHV RNA were absent in repeated liver biopsies. Only few hepatocytes stained weakly positive for WHc protein and frequency, and the intensity of WHsAg positive hepatocytes was low. The third animal developed severe reinfection within 3 weeks, similar to the woodchucks in the control group.

CONCLUSIONS

Liver transplantation from immunized donors to chronic carriers seems to be a promising strategy to reduce and delay severe reinfection, which may be applicable in clinical liver transplantation.

Liver transplant and recurrent disease

Current prophylactic measures have greatly reduced recurrence rates of hepatitis B after liver transplantation. HBIG remains a critically important compound and although there is variability in dosing regimens and target anti-HBs levels, it is the backbone of recurrence prevention. Adjuvant therapies with nucleoside/nucleotide analogs alone have been limited by drug-resistant strains of HBV, but the armamentarium of these molecules continues to grow and hence the management of the post-LT HBV patient will evolve further. Currently lamivudine with HBIG remains an excellent option provided the patient has not developed resistance, especially in the pre-LT period. Adefovir is the drug of choice in that setting and perhaps the preferred drug in the pre-LT setting to allow the use of lamivudine post-LT. Further testing with tenofovir and newer compounds in development will expand these options. The use of multiple nucleoside analogs is an intriguing option, based on the HIV experience of reducing drug resistance and optimizing viral suppression, and will likely be further studied.