Intranuclear inclusion bodies in liver of chronic hepatitis B with delta infection

Seventy-two patients with HBsAg-positive chronic hepatitis were studied for serum antibody to delta antigen (anti-HD) by radioimmunoassay. Delta antigen (HDAg) in liver of the 72 patients was also studied immunohistochemically using peroxidase-labeled anti-HD. In one of the 72 patients, high titers of anti-HD and intrahepatic HDAg were detected. In this patient, HDAg was localized mainly in nuclei and occasionally in the cytoplasm of hepatocytes. By immunoelectron microscopy, HDAg was observed diffusely in some hepatocytic nuclei, but their nucleoli, perichromatin and heterochromatin were devoid of HDAg. Occasionally, inclusion body-like ring-shaped or irregularly shaped aggregates of HDAg were observed in nuclei. At higher magnification, these aggregates consisted of an HDAg-positive amorphous substance and microtubular structures. In their vicinity, scattered HDAg-positive granules were also present. By conventional electron microscopy, similar inclusion bodies composed of a clustered amorphous substance and microtubular structures 10-20 nm in diameter, together with 20-30 nm irregular granules were observed in hepatocyte nuclei, but no core of Dane particles were found. These novel intranuclear structures were not observed in other patients with chronic hepatitis B. It is suggested that they may represent the characteristic ultrastructure associated with delta infection.