Localization of hepatitis A virus in marmoset liver tissue during the acute phase of experimental infection.

Electron microscopic and virological studies of marmoset liver tissue with acute infection of hepatitis A virus (HAV), especially in the earlier stages of infection, were carried out to characterize the maturation process of HAV. Four marmosets were inoculated intravenously with HAV suspension and sacrificed 1 week, 2 weeks, 3 weeks and 4 weeks after inoculation respectively. Hepatitis A antigen (HAAg) in 10% liver homogenates of marmosets was examined by radioimmunoassay and a large amount of HAAg was detected in the liver homogenate of two marmosets sacrificed 2 weeks and 3 weeks after inoculation respectively. The histodiagnosis of the marmoset sacrificed 2 weeks after HAV inoculation was normal. However, many clusters of virus-like particles about 27 nm in diameter, in both "solid" and "empty" forms were found, mainly in vesicles of Kupffer cells by electron microscopy. In the animal that developed mild hepatitis 3 weeks after inoculation HAV-like particles were found in vesicles of hepatocytes by electron microscopy. By immune electron microscopy using peroxidase-conjugated anti-hepatitis A antibody, HAAg was detected on the particles present within the cytoplasmic vesicles of Kupffer cells or hepatocytes and on the surrounding membrane of the vesicles which contained HAV-like particles.