BACKGROUND: Children with HBV in Poland are treated with preparations ofinterferon-alpha (IFN-alpha). The continuing lack of complete response to this type of anti-viral therapyremains to be explained. The application of cell biology techniques to identify the viral componentsin situ makes it possible to clarify the association between the distribution of the virus and morphologicalinjury to the liver, the immune response of the host, and clinical symptoms in the natural course ofinfection. Our study was intended to evaluate HBV expression in liver biopsies taken an average of twoyears after completion of IFN-a therapy in 10 children with serological markers of persistent HBV infection.MATERIAL/METHODS: For the immunocytochemical detection of HBcAg and for the hybridocytochemical detectionof HBV-DNA, the avidin-biotin-peroxidase (ABC) technique was employed, as well as classical in situ hybridization,both additionally amplified using the ImmunoMax technique. HBcAg and HBV-DNA levels were estimated usinga semiquantitative technique. RESULTS: Our study demonstrated persistent active replication of HBV inthe liver in all examined children. A mixed pattern of HBcAg localization prevailed (noted in cell nuclei,cytoplasm and cell membranes) with a somewhat lower proportion of involved cells and a more evident membranelocalization of HBcAg, as compared to results obtained before treatment. HBV-DNA was observed in thecytoplasm of a fraction of hepatocytes similar to that noted before therapy. CONCLUSIONS: The ImmunoMaxtechnique was found to be highly suitable for in situ monitoring of HBV replication after terminationof IFN-a treatment. Children with focal distribution of HBcAg and HBV-DNA have the potential for earliereradication of the virus from their livers.

Keywords: Adolescent, Avidin, Biotin, Child, Cytological Techniques, Follow-Up Studies, Hepatitis B Core Antigens, Hepatitis B virus, Hepatitis, Chronic, In Situ Hybridization, Interferon-alpha, Liver, Peroxidase, Time Factors