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Use of immunomodulatory therapy (other than interferon) for the treatment of chronic hepatitis B virus infection

Authors


Correspondence: GeorgeKk Lau, Division of Gastroenterology and Hepatology, University Department of Medicine, Queen Mary Hospital, 102 Pokfulum Rd, Hong Kong SAR, China. Email: GKKLau@hkstar.com

Abstract

Chronic hepatitis B virus (HBV) infection is a major health threat in Asia. In order to design a better therapeutic regimen, the underlyng mechanism of HBV viral persistence must be understood. Immunological studies have found that impaired HBV virus-specific T cell reactivity is the major cause of chronic infection, whereas strong and multispecific T cell responses to HBV are associated with long-term control, but not elimination of the virus. Furthermore, in the serological clearance of hepatitis B surface antigen (HBsAg) in allogeneic haematopoietic cell transplantation, HBsAg seroconversion is associated with activation of the donor’s hepatitis B core antigen-specific CD4+ T lymphocytes. This suggests that the donor’s hepatitis B core antigen-specific CD4+ T cells provide ‘intermolecular T cell help’ for the HBsAg seroconversion. These findings are relevant to the future development of therapeutic vaccines or DNA vaccine as immunotherapy for chronic hepatitis B. Apart from interferon-α, thymosin α1 (Tα1) has been investigated for treatment of chronic hepatitis B. Meta-analysis of 4 randomized controlled studies investigating the safety and efficacy of Tα1 monotherapy for the treatment of chronic hepatitis B showed that 6 months treatment with Tα1 (1.6 mg twice weekly) almost doubles the sustained response rate (36%) compared with controls (19%; P = 0.04). However, more specific immunological approaches are being developed; notably, hepatitis B core antigen-based therapeutic vaccine was found to induce T cell proliferative responses in chronically infected hepatitis B patients to the T helper epitope included in the construct. However, the cytokine profile observed suggested the induction of a T helper 0/T helper 2 CD4+ T cell response rather than T helper 1 response. Thus, its combination with interferon-γ or interleukin-12, which might reverse the CD4+ T cell response, should be considered. In the future, it is likely that different types of combination therapy may have to be tailor-made for chronic HBV infection with different virological and immunological profiles and different degrees of liver damage.

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