Hepatitis B infection in haematopoietic stem cell transplantation: still unresolved.

Impact of hepatitis B virus (HBV) infection on haematopoietic stem cell transplantation (HSCT) was reported earlier since late 1980s. It was shown that changing patterns of HBV serological markers was accompanied by variable severity of hepatitis after transplantation. Recipient's hepatitis B virus surface antigen (HBsAg) positivity was not considered an absolute contra-indication to allogeneic HSCT. However, HBsAg positivity was an important risk factor of reactivation hepatitis after transplantation, especially in allogeneic setting. Managing HBV reactivation in HSCT recipients was not successful till the availability of lamivudine since mid-1990s. For HBsAg-positive recipients, prophylactic lamivudine has been shown to significantly reduce reactivation hepatitis. As for HBsAg-negative recipients, there have been a small number of patients who develop so-called reverse seroconversion, that is, appearance of HBsAg after transplantation. In addition to chronic graft-versus-host disease, the risk was also high in allogeneic HSCT recipients who received fludarabine-antithymocyte globulin-containing conditioning regimens. The HBV is harboured earlier in the recipients before transplantation rather than transmitted via transfusion. At present, the optimal duration of lamivudine prophylaxis is not well-defined, and there are several fatal cases associated with early withdrawal and resistant HBV mutants. In conclusion, in HBV-endemic areas, the war between HBV and HSCT recipients continued even though several anti-HBV agents and molecular detection techniques are available. It deserves additional effort to overcome and also presents a chance to elucidate underlying mechanisms of HBV immunity, which are not easily studied in non-HSCT setting.