Active Hepatitis B Viral Replication
Untreated HBV replicates rapidly, driving high viral loads.
- 254 M: Chronic HBV carriers worldwide (global burden)
- 10¹¹: Virions produced per day (untreated infection)
- 15–40%: Lifetime cirrhosis risk (without treatment)
- 3.2 kb: HBV genome size (partly double-stranded DNA)
Viral replication cycle
HBV reverse-transcribes an RNA intermediate into new DNA.
The cccDNA reservoir
Covalently closed circular DNA persists inside the nucleus.
Key insight: cccDNA is rarely cleared, only suppressed.
Why suppression matters
High viral load drives ongoing liver inflammation and fibrosis.
Tenofovir or Entecavir Therapy Begins
First-line nucleos(t)ide analogues block viral DNA synthesis.
- 0%: Tenofovir resistance at 8 yrs (high genetic barrier)
- <1.2%: Entecavir resistance (naive) (over 5 years)
- Once daily: Dosing schedule (oral tablet)
- NRTI: Mechanism class (chain-terminating analogue)
Mechanism of action
Analogues terminate the growing viral DNA chain.
Preferred first-line agents
Tenofovir and entecavir are favored for high potency.
Adherence is essential
Daily adherence sustains durable long-term suppression.
Key insight: missed doses risk resistance and rebound.
Progressive HBV DNA Suppression
HBV DNA falls log by log as therapy continues.
- 2–3 log: Log decline by week 12 (typical response)
- 70–90%: Suppression rate by week 48 (adherent patients)
- Biphasic: Decay pattern (fast then slow phase)
- 12 wk: Monitoring interval (HBV DNA testing)
Biphasic decline kinetics
Viral decline follows a fast phase then a slower phase.
Routine monitoring
Clinicians recheck HBV DNA levels every 12 weeks.
ALT normalization trend
Liver enzymes fall as inflammation gradually subsides.
HBV DNA Below the Detection Limit
Sustained therapy pushes viral load under 20 IU/mL.
- 20 IU/mL: Assay detection limit (lower limit of quantification)
- ~90%: Suppression by year 1 (adherent patients)
- Yes: cccDNA persistence (despite suppression)
- High: Relapse risk if stopped (without seroconversion)
What undetectable means
Undetectable is not cured — cccDNA still remains.
Clinical benefit
Suppression halts fibrosis and lowers cancer risk.
Key insight: suppression cuts hepatocellular carcinoma risk significantly.
Ongoing therapy need
Most patients require indefinite continued antiviral treatment.
HBeAg Seroconversion to Anti-HBe
A favorable immune shift signals durable viral control.
- ~10%: Annual seroconversion rate (per year on therapy)
- Immune control: Anti-HBe significance (marker of response)
- Possible: Off-therapy candidacy (after consolidation period)
- Rare: HBsAg loss (functional cure) (the ultimate treatment goal)
What HBeAg signals
HBeAg is a secreted marker of active viral replication.
The seroconversion event
Anti-HBe antibodies replace circulating HBeAg protein.
The next milestone
HBsAg loss remains the rare functional-cure endpoint.
Key insight: seroconversion may allow considering therapy discontinuation.