Hepatitis D virus - MegaMicro

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Hepatitis D virus

Micro > Virology > RNA viruses
Hepatitis D virus (HDV) (Delta agent)

Structure:
·         Deltavirus (tentative) genus
·         Negative sense single strand circular RNA virus
·         Enveloped
·         Icosahedral nucleocapsid
Pathobiology:
·         Transmitted through blood, via body fluid, sexual contact, or transplacentally → travels in blood to hepatocytes → infects cells → replicates and released only from those cells also infected with HBV, because it requires hepatitis B surface antigen (HBsAg) to form an infectious particle (HDV is defective/non-infectious and cannot replicate alone)
o   Therefore, you must have an active hepatitis B infection to get a hepatitis D infection.  This can either be achieved by co-infection or sequential infection (B then D).
·         Viral antigens on infected hepatocytes recognized by host immune response → CTL activated → inflammation, hepatocyte necrosis → hepatitis more severe than with HBV alone
Epidemiology:
·         Those at greatest risk are IV drug users.
·         Hepatitis D is endemic to the Mediterranean basin.
Laboratory Diagnosis:
·         Delta antigen detection
·         Anti-delta antigen IgM antibodies
Disease Manifestations:
·         Clinical Presentation
o   Presents as hepatitis
o   Hepatitis D worsens the clinical symptoms experienced with hepatitis B, both with the co-infection and superinfection. This is primarily due to the fact that the hepatitis D virus is directly cytotoxic to hepatocytes.
§ Coinfection: higher chance of liver failure and quicker progression to cirrhosis.
§ Superinfection: often results in severe acute hepatitis in a patient already chronically infected with HBV.

Therapy
  • α-IFN (controls HBV infection, which limits HDV infection)
  • Vaccine: recombinant Hepatitis B Surface Antigen to prevent HBV infection
  • Getting rid of HBV guarantees elimination of HDV

Quick Facts:
·         HBV carriers who become superinfected with HDV have a much poorer prognosis, with a greater chance of fulminant hepatitis and liver failure.
·         HDV may also have a cytopathic effect independent of a host immune response.
·         The HDV genome is a ribozyme, which is an RNA particle able to cleave and ligate itself. No other human viruses behave this way, but many plant viruses in the viroid group do.

Prevention:
  • Avoid exposure (blood products, IVDU, sexual)
  • Prevent / treat Hepatis B
    • Hepatitis B vaccination
Related concepts
1.       Hepatitis D
2.       HDV
3.       Delta agent
4.       Hepatitis B
5.       HBV
6.       Co-infection
7.       Superinfection
8.       Liver failure
9.       Cirrhosis
10.   Single stranded RNA virus

 
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