Hepatitis B and D
- Topic
Hepatitis B hides in liver cell nuclei; the immune attack on infected cells, not the virus itself, damages the liver.
What it is
Hepatitis B virus is a DNA virus that keeps a stable copy of its genome (cccDNA) in the hepatocyte nucleus and can integrate into host DNA. The virus is not directly cytopathic: liver damage comes from cytotoxic T cells killing infected hepatocytes. Age at infection decides the outcome: most infections at birth become chronic, most adult infections resolve. The serologic markers trace each phase and are a must-know table. Hepatitis D needs HBV and makes its course worse.
Structure
- Ground-glass hepatocytes: finely granular pale pink cytoplasm full of HBsAg in the endoplasmic reticulum (chronic infection).
- Sanded nuclei from abundant core antigen, seen in some chronic infections.
- Otherwise the pattern of acute or chronic hepatitis: lobular inflammation, acidophil bodies, interface hepatitis.
Step by step
- The virus enters hepatocytes through the bile acid transporter NTCP.
- Its genome becomes cccDNA in the nucleus, a long-lived template for viral RNA.
- Viral proteins are made; excess HBsAg circulates as non-infectious particles.
- Cytotoxic T cells recognize viral peptides and kill infected hepatocytes: hepatitis.
- A strong response clears the virus; a weak or tolerant one (as in newborns) lets it persist.
- Years of inflammation, regeneration and DNA integration lead to cirrhosis and hepatocellular carcinoma.
Reading hepatitis B serology
| Pattern | HBsAg | Anti-HBs | Anti-HBc | HBeAg |
|---|---|---|---|---|
| Acute infection | Positive | Negative | IgM positive | Usually positive |
| Window period | Negative | Negative | IgM positive | Negative |
| Recovered, immune | Negative | Positive | IgG positive | Negative |
| Vaccinated | Negative | Positive | Negative | Negative |
| Chronic, replicative | Positive (over six months) | Negative | IgG positive | Positive (or HBeAg-negative with high DNA in precore mutants) |
| Chronic, low replication | Positive | Negative | IgG positive | Negative, anti-HBe positive |
Markers
- HBsAg immunostain
- HBcAg immunostain
- Orcein or Victoria blue (HBsAg)
Clinical notes
- Extrahepatic immune-complex disease: polyarteritis nodosa, membranous glomerulonephritis.
- Spread: blood, sex, mother to child at birth; vaccination at birth prevents most perinatal infection.
Test yourself
Think of the answer, then tap the question to see it.
Which marker is the only positive one in the window period of hepatitis B?
IgM anti-HBc (antibody to the core antigen).
How do you tell vaccination from past infection on serology?
Both have anti-HBs, but only past infection has anti-HBc; vaccine contains only surface antigen.
What causes liver cell damage in hepatitis B?
The host's cytotoxic T cells attacking infected hepatocytes; the virus itself is not directly cytopathic.
Why is HDV superinfection worse than coinfection?
In a chronic HBV carrier HBsAg is always present, so HDV replicates freely and the infection tends to become chronic and severe.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Hepatitis B: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Hepatitis D (Delta agent): MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Hepatitis B (World Health Organization, 2026).
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Representative model, for educational purposes only.