ABSTRACT
Hepatitis D virus is a most unusual virus incidentally discovered by Rizzetto et al. in 1977 [1] as a previously unrecognized, HBV-encoded, nuclear antigen (termed delta antigen, HDAg) in the hepatocytes of patients with hepatitis B virus (HBV) infection. Transmission of infectious hepatitis to chimpanzees using these patients’ sera proved that the HDAg belonged to a new virus, named hepatitis delta virus (HDV) [2]. HDV was found to possess a nucleocapsid consisting of viral RNA and HDAg, surrounded by a hepatitis B surface antigen (HBsAg) envelope. Structurally, HDV is very similar to viroids, a family of subviral agents infecting plants [3] but different from typical viroids in several aspects [4]. Partly because of the lack of a close relation with any other animal viruses, the HDV has been classied as the only representative of the new genus of Deltavirus, infecting humans and responsible for hepatitis delta infection.
