A
hepatitis B surface antigen (
HBsAg) chronic carrier chimpanzee experimentally superinfected with delta virus (DV) developed chronic DV
infection. Over a period of 12 months, serologic and biochemical changes were correlated with morphologic abnormalities of the liver. Severe hepatic
necrosis and
inflammation accompanied the initial acute episode of
hepatitis on Day 35 after inoculation, followed by complete resolution of these lesions over the next 3 months. A second episode of
hepatitis occurred on Day 145, and severe
necrosis and
inflammation recurred along with the reappearance of
delta antigen in the hepatocytes.
Delta antigen persisted in the liver following the second episode of
hepatitis and has remained positive throughout the observation period of 1 year. During the initial acute episode, the hepatocytes exhibited foamy cytoplasmic changes resembling microvesicular fat. However, ultrastructural studies of the same cells revealed only vacuolization of the cytoplasm without evidence of fat droplets. The inflammatory infiltrate during both episodes of
hepatitis demonstrated a striking predominance of macrophages over lymphocytes. Hepatocyte abnormalities observed by electron microscopy included vacuoles, proliferated endoplasmic reticulum, and tubules similar to those seen in posttransfusion non-A, non-B
hepatitis. However, the tubular and reticular abnormalities coincided with
delta antigen expression in liver biopsies detected by direct immunoperoxidase staining and abnormal
alanine aminotransferase levels in the serum, which suggests a possible causal relationship. Nuclear abnormalities were not seen.