A 30-year-old with chronic hepatitis B (HBeAg-negative, HBsAg-positive, anti-HBe-positive) has HBV DNA of 8000 IU/mL and ALT 3× upper limit. A mutation in the pre-core region (G1896A) is detected. This mutation causes:
- A A premature stop codon in the pre-core region preventing HBeAg secretion ✓
- B Increased replication with high HBeAg production
- C Resistance to nucleos(t)ide analogues
- D Absence of HBsAg production (occult HBV)
Correct answer: A. A premature stop codon in the pre-core region preventing HBeAg secretion
Explanation
The G1896A pre-core mutation creates a premature stop codon (tryptophan→stop at codon 28) in the pre-core open reading frame, preventing synthesis and secretion of HBeAg while viral replication continues; this is characteristic of HBeAg-negative chronic hepatitis B. This mutation does not confer nucleoside analogue resistance (which involves RT domain mutations like rtM204V/I). Occult HBV results from S-gene mutations reducing HBsAg below detection threshold.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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