The hepatitis B virus-associated , antigen was found in the serum of experimentally infected chimpanzees as an internal component of a discrete subpopulation of hepatitis B surface antigen (HBsAg) particles. The 35-to 37-nm particles banded in CsCl at 1.24-1.25 g/cm3 and sedimented with a mobility intermediate between that of the hepatitis B virion and that of the 22-nm form of HBsAg. The particles contained only indistinct internal structure by electron microscopy and were not unique to 5 agent infection, similar particles without 5-antigen activity being observed in the preinfection serum of HBsAg carrier chimpanzees. A small RNA (Mr, 5 X 105) was temporally associated with 5 antigen in the serum of infected chimpanzees and copurified with the -antigen-associated particles. This RNA is smaller than the genomes of known RNA viruses but larger than the viroids of higher plants. The 3 antigen (6-Ag), a relatively new specificity, first was detected by immunofluorescence in the liver of human subjects with chronic hepatitis B surface antigen (HBsAg) hepatitis (1). Ultrastructural studies have failed to demonstrate components of hepatitis B virus (HBV) in b-Ag-positive nuclei (2) and the b-Ag-anti-b-Ag system is distinct from the known antigenantibody systems of HBV (3). Prevalence studies of b-Ag-anti-3-Ag in human populations (4,5) and transmission experiments in chimpanzees (6) indicate that b-Ag is associated with a transmissible pathogenic agent, 3 agent, that is either a HBV mutant with characteristics of a defective interfering particle or a new agent which requires helper functions of HBV for its expression.After extraction from hepatocyte nuclei with guanidine hydrochloride, b-Ag was characterized as a protein with a molecular weight of approximately 68,000 (2). Although b-Ag has not been detected in the sera of patients with intrahepatic b-Ag, such individuals develop high titers of anti-3-Ag which might interfere with the available solid-phase radioimmunoassay for b-Ag. The analysis of serial specimens from chimpanzees to which 3-agent was transmitted revealed 6-Ag in the sera during the acute phase of infection and prior to the development of anti-3-Ag (6). We report here the association of 3-Ag in serum with a discrete subpopulation of HBsAg and a low molecular weight RNA. MATERIALS AND METHODSSource of 5Ag. Two chronic HBsAg-carrier chimpanzees (nos. 29 and 800) were infected with 3 agent by inoculation with serum from a patient with chronic type B hepatitis and intrahepatic b-Ag. Serum samples and percutaneous liver biopsies were taken from each animal before inoculation and weekly thereafter and analyzed for markers of b-Ag and HBV. TheseThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 6124 chimpanzees were part of a transmission study of the 3 agent and experimental details are reported elsewhere (6). Serum samples containing b-Ag...

Inoculation of hepatitis B surface antigen (HBsAg)-positive sera from patients with chronic liver disease and intrahepatic delta (delta) into chimpanzees susceptible to infection with hepatitis B virus (HBV) resulted in type B hepatitis and delta markers (delta antigen and antibody to delta) in recipient animals. A dilution (10(-8)) of serum induced type B hepatitis without delta markers in another HBV-susceptible animal. HBV infection and delta markers did not develop in animals with preexisting titers of antibody of HBsAg. In chimpanzees with circulating HBsAg at the time of inoculation, synthesis of delta occurred earlier and its extent and duration were greater than in animals previously unexposed to HBV; coincident with synthesis of delta, hepatitis occurred in chronic HBsAg carriers, and synthesis of preexisting HBV gene products (HBsAg and hepatitis B core antigen) was diminished. Delta appears to be a marker of a transmissible pathogenic agent, either an HBV variant or another agent that requires the helper functions of HBV, that is defective and interferes with HBV replication.