Hepatitis B virus precore mutations and HBeAg negative reactivation of chronic hepatitis B after interferon therapy

Hepatitis B reactivation after chemotherapy: two decades of clinical research

Hepatitis due to hepatitis B virus reactivation after cytotoxic or immunosuppressive therapy is a serious cause of liver-related morbidity and mortality. With the characterization of the underlying pathogenesis, much progress in the management of this important clinical problem has been made in the past 2 decades. By year 2008, it is mandatory to screen for hepatitis B surface antigen status before initiating intensive chemotherapy or immunosuppressive therapy. All those who are hepatitis B surface antigen positive should be started on preemptive nucleos(t)ide analogues. However, there remains important issues, such as the type and duration of nucleos(t)ide analogue therapy, which need to be understood. As not all hepatitis B surface antigen-positive patients will suffer from HBV reactivation, it is therefore useful to identify risk factors related to HBV reactivation so that patients will not be treated unnecessarily with nucleos(t)ide analogues. To date, a high baseline level of viral replication, as reflected by high serum HBV DNA level, positive serum hepatitis B e antigen, and a high intrahepatic covalently closed circular DNA level, is the most important predictor for HBV reactivation. Recently, there has been an increased awareness of reactivation of occult hepatitis B virus, especially in hepatitis B virus endemic area, such as the Asia-Pacific region. Careful epidemiological study will be needed to clarify the impact of occult hepatitis B infection in patients treated with cytotoxic or immunosuppressive therapy.

Hepatitis B reactivation in patients positive for hepatitis B surface antigen undergoing autologous hematopoietic cell transplantation

Hepatitis due to reactivation of hepatitis B virus is an important cause of liver-related morbidity and mortality in hepatitis B surface antigen (HBsAg) positive patients undergoing autologous hematopoeitic cell transplantation. With the recent introduction of sensitive serum HBV DNA quantitation assay, the diagnosis of hepatitis B reactivation can now be made more reliably. As these hepatitis are driven by the host immune response to a surge of hepatitis B viral load, the availability of effective nucleoside analogues which can inhibit hepatitis B viral replication has opened up new approaches to this previously untreatable condition. Up till now, two such nucleoside analogues, lamivudine and adefovir dipivoxil, have been approved for the treatment of chronic hepatitis B infection. However, further studies are needed to determine which nucleoside analogues should be chosen in this transplant setting. Due to the high dose chemotherapy generally needed in autologous hematopoeitic cell transplantation, there is a high risk of post-transplant hepatitis B reactivation. Hence, all HBsAg positive patients undergoing autologous hematopoeitic cell transplantation should preferably be treated pre-emptively with nucleoside analogous. An alternative approach is to defer treatment with nucleoside analogous until there is evidence of hepatitis B virological reactivation. However, the latter approach would need the patient's hepatitis B viral load be monitored at a very close interval and might not be cost-effective.

Diagnosis and management of pre-core mutant chronic hepatitis B

Chronic hepatitis due to pre-core hepatitis B virus (HBV) mutants presents as hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB). HBeAg-negative CHB represents a late phase in the natural course of chronic HBV infection that develops after HBeAg loss and seroconversion to anti-HBe. It is usually associated with pre-core stop codon mutation at nucleotide 1896 (mainly selected in non-A HBV genotypes), but also with other pre-core changes or with mutations in the basic core promoter region (mainly in HBV genotype A). In chronic HBV infections, pre-core mutants can be detected both in patients with HBeAg-negative CHB and in inactive hepatitis B surface antigen (HBsAg) carriers. The diagnosis of HBeAg-negative CHB is based on HBsAg positivity, HBeAg negativity, and mainly on increased alanine aminotransferase (ALT) and serum HBV-DNA levels and exclusion of other causes of liver disease. The differential diagnosis between patients with CHB and inactive HBsAg carriers can be made only by close follow-up of aminotransferase activity and viraemia levels, although the cut-off level of serum HBV DNA has not been definitely determined. IgM anti-HBc levels have also been suggested as an index that increases the diagnostic accuracy for transient hepatitis flares, while liver biopsy confirms the diagnosis and evaluates the severity of the liver disease. Interferon-alpha (IFN-alpha) and lamivudine are the two drugs that have been tried, mainly in the management of HBeAg-negative CHB. A 12-month course of IFN-alpha achieves sustained biochemical remission in about 20% of patients, which has been associated with improvement in the long-term outcome of this subset. A 12-month course of lamivudine is rather ineffective, maintaining remission in less than 15% of patients after cessation of therapy. Long-term lamivudine is associated with progressively increasing rate of virological and subsequent biochemical breakthroughs due to YMDD mutants, with approximately 30% of patients remaining in remission in the third year of therapy. Several other antiviral agents are currently being evaluated in this setting with combined regimens being the most reasonable step for the near future.