Human
hepatitis delta (delta) virus (HDV) is a form of defective virus, which infects humans only in the presence of a co-infecting hepatitis B virus (HBV). HDV
superinfection in a chronic HBV carrier often results in severe
chronic hepatitis and
cirrhosis, whereas acute HDV and HBV
co-infection is frequently associated with
fulminant hepatitis. HDV consists of a 36-nm particle, which contains an envelope with HBV
surface antigen, and a nucleocapsid containing the
hepatitis delta-antigen (
HDAg) and an
RNA genome of 1.75 kilobases (kb). Recently, the genomic
RNA from an HDV serially passaged in chimpanzees has been cloned and sequenced in a study which showed that the HDV
RNA is a single-stranded circular molecule with properties similar to those of viroid or virusoid. However, it is not known whether serial passages in chimpanzees had altered the properties of human HDV. Here we report the cloning and sequencing of an HDV
RNA isolated directly from a patient with acute
delta-hepatitis. The sequence showed considerable divergence (11%) from that of the chimpanzee-adapted HDV. Five open reading frames (ORFs) of more than 100
amino acids in both genomic and anti-genomic sense were found. The largest ORF in antigenomic sense, which can code for 214
amino acids, may correspond to the
HDAg.