OCCURRENCE AND ULTRASTRUCTURAL-LOCALIZATION OF DUCK HEPATITIS-B VIRUS IN THE LIVER OF DUCKS AFTER EXPERIMENTAL-INFECTION

A sequential study was performed to investigate the occurrence and localization of duck hepatitis B virus in the liver of domestic ducks utilizing the indirect immunoperoxidase method and electron microscopy. Seventeen ducklings were injected intravenously with duck hepatitis B virus-positive serum within 24 hr after hatching and were subsequently sacrificed on the 2nd, 3rd, 4th, 5th, 27th and 44th day after injection. Nine ducklings were not injected and were used as a negative control. Duck hepatitis B virus DNA by spot hybridization using a[32P]-labeled probe occurred in trace amounts on the 2nd day and in large amounts on th 4th day after inoculation. Immunoreactivity for DHBV was seen in the hepatocytes, sporadically on the 2nd day and diffusely on the 4th day, and also in the biliary epithelial cells on the 27th day. Both kinds of cells revealed staining in the cytoplasm but not in the nucleus. Virus particles were recognized by electron microscopy in the hepatocytes beginning on the 4th day. The hepatocytes had many incomplete virus particles, 40 to 61 nm in diameter, and a few complete virus particles, 40 nm in diameter, in the cisternae of the rough and smooth endoplasmic reticula. Such particles and the endoplasmic reticulum showed reaction products for duck hepatitis B virus by immunoelectron microscopy. There were clusters of core particles, 27 nm in diameter, in the hyaloplasm around peroxisomes where an assembly of cores appeared to occur. No conspicuous virus particles were recognized in the biliary epithelial cells. The similarities and differences in virus localization between duck hepatitis B virus and hepatitis B virus are discussed.