General Virology and DNA Viruses
An elderly male patient with known chronic hepatitis B virus (HBV) status suddenly presents with acute hepatitis episodes. Serology confirms HDV co-infection. Which one of the following describes the delta agent?
|A||A hepatitis B mutant|
|B||A defective RNA virus|
|C||An incomplete hepatitis B virus|
|D||A defective DNA virus|
a. The delta agent was first described in 1977 and has recently been shown to be a defective RNA virus that requires HB5Ag for replication.
b. It is found most often in persons who have multiple parenteral exposures—for IV drug abusers, hemophiliacs, and multiply transfused patients.
HDV is transmitted principally by blood and blood products, but also by sexual contact. Vertical transmission is also possible. Two types of HDV infections are possible:
a. Simultaneous coinfection with HBV and HDV in the same inoculum. It most commonly results from parenteral transmission, for example, in intravenous drug users.
b. The clinical and biochemical features of such infection resemble those of acute hepatitis B alone.
c. However, coinfection with HBV and HDV may be more severe than the disease caused by HBV alone.
d. Superinfection of an HBsAg carrier by HDV. It is commoner and more serious because a large number of hepatocytes are already producing HBsAg, and HDV can replicate without delay with a relatively short incubation period.
e. It leads to severe liver damage, fulminant HBsAg positive hepatitis and elevated mortality (up to 20%).
In simultaneous acute HBV and HDV infections, IgM anti-HBc will be detectable, while in acute HDV infection superimposed on chronic HBV infections, anti-HBc will be of IgG class.