Transmission of the Hepatitis B Virus-Associated δ Agent to the Eastern Woodchuck

δ agent of human origin was inoculated into four woodchucks chronically infected with woodchuck hepatitis virus (WHV). The animals developed δ infections with serologic patterns similar to those previously observed in human and chimpanzee infections. δ antigen was detected transiently in serum and liver and was followed by seroconversion to anti-δ antibody. Analogous to the chimpanzee model of δ infection, serum and hepatocyte markers of WHV were suppressed in the woodchuck during acute δ infection. The suppression of WHV DNA in serum was evident only during the time of δ positivity, while the inhibition of other WHV markers was more protracted. The δ antigen in woodchuck sera circulated as an internal component of a particle similar in size to the human δ particle (36-nm diameter) and was encapsidated by the woodchuck hepatitis virus surface antigen; δ antigen from infected woodchuck and chimpanzee livers had similar biophysical properties. Histologic analysis showed that experimental δ infection is associated with a transient acute hepatitis in woodchucks and loss of hepatocytes carrying WHV antigens. The lesions differed from the conspicuous hepatitis associated with reappearance of WHV replication. Hepatitis B-like viruses, therefore, appear to provide the requisite helper functions for δ replication and the woodchuck represents a useful model for study of the virology and pathology of the δ agent.