-Hepatitis B virus (HBV) is an enveloped DNA virus belonging to the family hepadnavirus.
-It comprises of a partial double-stranded DNA genome surrounded by HBcAg and carrying viral DNA polymerase (reverse transcriptase) and HBeAg and wrapped in a lipid bilayer membrane containing HBsAg.
-It is the smallest known human DNA virus with respect to genome size.
-It is found in blood, saliva, and semen.
-It is transmitted through blood and blood-derived products, sexual contact, sharing needles and syringes, injecting drugs, and mother-to-child.
-The incubation period may be as brief as 30 days or as long as 180 days (mean approximately 60-90 days).
Symptoms & Signs:
Pathogenesis involves immune-mediated serum sickness-like rash and arthritis leading to constitutional symptoms – anorexia, nausea, jaundice, fatigue, loss of appetite, fullness in the right upper abdominal quadrant
-The laboratory diagnosis of acute hepatitis B infection is best made by demonstrating the presence of HBsAg and IgM antibody to HBcAg in serum, since this antibody disappears within 6 months of the acute infection
-Appearance of antibody to HBsAg signals elimination of infection
-Window period has neither HBsAg nor antibody to HBsAg but antibody to HBcAg (IgM) is present
-In patients who subsequently recover, HBsAg usually becomes undetectable after four to six months. Persistence of HBsAg for more than six months implies chronic infection.
–Chronic infection associated with HBsAg persistence and no development of antibody to HBsAg. IgG antibody to HBcAg present
-In immunity due to vaccination, antibody to HBsAg is seen.
-No specific treatment for acute infection
-Antiviral agents for chronic HBV include pegylated interferon or nucleotide analogs (entecavir and tenofovir).
-HBsAg is given as a subunit vaccine in three doses (0, 1, and 6 months) to provide long-term protection by producing IgG.
-It is recommended for use in children starting at age 0 to 2 months and in adults given in 3 doses at 0, 1 and 6 months.
– About 90% of the patients resolve the infection after acute disease that may be asymptomatic.
-The likelihood of liver failure from acute HBV is less than 1 percent.
-Less than 10% of the patients develop chronic infection.
Q: What is the serologic hallmark of HBV infection? Hepatitis B surface antigen (HBsAg)
Q: Why is Hepatitis B core antigen (HBcAg) not detectable in serum? It is an intracellular antigen that is expressed in infected hepatocytes.