HDV is a small, spherical virus with a diameter of about 36 nm. It has an outer coat of HBV envelope proteins and host lipids that encapsulate its genome. The HDV circular genome exists as a single stranded RNA that contains 1672-1697 nucleotides, the smallest known genome of any animal virus. It is hypothesised that the virus may have originated from a plant pathogen smaller than viruses known as viroids. A HDV specific protein called HDAg (delta antigen) combines with the genome to form a ribonucleoprotein (a stable RNA-protein complex).
The HDV does not possess an RNA polymerase and is dependent on the host polymerase for its replication. Although HDV can replicate autonomously, the simultaneous presence of HBV (which makes the envelope proteins used by HDV) is required for complete virus assembly, secretion, cellular attachment, and infection propagation. Recently, it was shown that HDV can also use HBV-unrelated viruses for its envelope proteins. Several virus genera including vesiculovirus, flavivirus and hepacivirus, can package the HDV genome. Furthermore, hepatitis C virus (HCV) may also be capable of propagating HDV infection. It is unclear whether HBV-unrelated viruses are used in human HDV infection.
The virus is resilient and can survive dry heat at 60°C for 30 hours.
Author: Minaam Abbas