Electron microscopic studies on duck hepatitis B virus particles in hepatocytes and sequential changes in various patterns of infection.

To investigate the critical factors involved in the elimination of the duck hepatitis B virus (DHBV) in acute infection, the sequential changes in the number of DHBV particles in hepatocytes were studied electron microscopically in ducks experimentally infected by DHBV. Twenty Japanese white Peking ducks were infected with DHBV on the day of hatching, and on the 7th day and 14th day after hatching. Inoculation of DHBV on the day of hatching, and on the 7th and 14th day after hatching resulted in persistent viremia, transient viremia and no viremia, respectively in ducks as tested by spot hybridization assay. The number of DHBV particles in the liver correlated well with the amount of serum DHBV-DNA, DHBV particles decreased in hepatocytes without any interaction of inflammatory cells over the observation period, and the number of particles was not associated with the degree of hepatic inflammation. From these results, the elimination of the virus was thought to be induced by a reduction of viral replication in the hepatocytes and not by destruction of their host cells. There must be an age-dependent factor which strongly suppresses the viral replication.