CLINICAL AND IMMUNOLOGICAL ASPECTS OF HEPATITIS-B VIRUS-INFECTION IN CHILDREN RECEIVING MULTIDRUG CANCER-CHEMOTHERAPY

For two reasons hepatitis B virus infection is an important problem in patients with cancer. First, multidrug cancer chemotherapy may reacti vate or worsen a previously benign chronic HBV infection. Second, pati ents undergoing cancer chemotherapy are at an increased risk of acquir ing and spreading HBV which may result in an endemic infection. HBV re activation may precipitate into a severe acute disease including fulmi nant hepatitis. In contrast, the acquisition of HBV during cancer chem otherapy commonly takes a mild clinical course but frequently leads to persistently high viremia. This state of immunotolerance to viral ant igens allows viral replication without any sign of liver cell destruct ion. Withdrawal of chemotherapy does not cause significant changes if infection occurred during cytotoxic chemotherapy. Infection with HBV d uring cancer chemotherapy, therefore, may be considered as a model of an induced antigen-specific immunotolerance. In agreement with this hy pothesis, vaccination against HBV during cancer chemotherapy does not prevent spread of HBV in oncology wards as it does not produce signifi cant anti-HBs titers. Furthermore, vaccination even suppresses the imm une response to later booster doses after chemotherapy has been withdr awn.