Questions: Viral Hepatitis: Acute Hepatocellular Necrosis, Inflammation, and Recovery vs. Chronicity

Question 1

A patient with acute HBV infection has severely elevated ALT and AST, indicating major hepatocyte damage, but a relatively modest level of HBV DNA in the blood. What does this pattern suggest?

• A. The lab results are contradictory — high viral load should always correlate with high transaminases.
• B. The liver damage is primarily immune-mediated: CD8+ T cells killing HBV-infected hepatocytes accounts for most hepatocyte destruction, independent of viral load.
• C. The HBV strain is particularly cytopathic, destroying hepatocytes directly before the immune system responds.
• D. Low viral load indicates the infection is already resolving, and elevated enzymes are a delayed measurement artifact.

Answer: (B)

The key insight is that hepatitis viruses are not strongly cytopathic — they replicate in hepatocytes without immediately destroying them. The damage reflected in elevated ALT/AST comes primarily from CD8+ cytotoxic T cells recognizing viral antigens on infected hepatocyte surfaces and killing them, plus the inflammatory cascade (macrophages, NK cells, neutrophils releasing ROS and proteases). A patient with a vigorous immune response can have extensive hepatocyte killing even with modest viremia. Conversely, immunocompromised patients may have high viral loads with minimal transaminase elevation.

Question 2

Why is hepatitis B virus so difficult to cure even when antiviral therapy successfully suppresses serum HBV DNA to undetectable levels?

• A. HBV integrates into the human genome and triggers continuous viral protein production from those integration sites.
• B. HBV establishes a nuclear reservoir of covalently closed circular DNA (cccDNA) in hepatocytes that persists even when serum viral replication is suppressed.
• C. HBV mutates rapidly like HCV, evading both antiviral drugs and immune surveillance through quasispecies diversity.
• D. HBV requires HBsAg coat proteins from HDV co-infection to maintain its reservoir.

Answer: (B)

HBV forms cccDNA — a stable, episomal mini-chromosome inside hepatocyte nuclei. cccDNA is the template for viral RNA and protein production, and current antivirals suppress serum viral DNA replication without eliminating this reservoir. When treatment stops, the reservoir reactivates. This is distinct from HCV, which evades clearance through quasispecies diversity (rapid mutation), not cccDNA. HBV can integrate into the host genome, but the cccDNA reservoir is the primary barrier to cure.

Question 3

Elevated ALT and AST in viral hepatitis directly reflect the number of virus particles replicating in the liver — higher viral load means higher transaminase levels.

• T. True
• F. False

Answer: False

Transaminases reflect hepatocyte death and membrane disruption, not viral replication per se. Since most hepatocyte killing in viral hepatitis is immune-mediated (not directly cytopathic), transaminase elevation reflects the vigor of the immune response and the number of hepatocytes being killed by CD8+ T cells — not simply how much virus is present. A patient with strong immune activity and moderate viral load can have dramatically elevated transaminases, while an immunocompromised patient with high viral load might have only mildly elevated enzymes.

Question 4

Hepatitis D virus (HDV) can only cause infection in individuals who are also infected with hepatitis B virus.

• T. True
• F. False

Answer: True

HDV is a defective satellite virus — it can replicate within a cell but requires the HBV surface antigen (HBsAg) to assemble infectious particles for spread. Without the HBsAg coat, HDV cannot produce complete virions. This creates two distinct clinical patterns: co-infection (HBV + HDV acquired simultaneously, usually self-limiting) and superinfection (HDV acquired by someone already chronically infected with HBV, which dramatically accelerates liver disease progression). Vaccination against HBV therefore also prevents HDV infection.

Question 5

Why does the liver sustain significant damage in viral hepatitis even though the hepatitis viruses themselves are not strongly cytopathic to hepatocytes?

Model answer: The viruses replicate within hepatocytes without immediately destroying them. Damage occurs when the immune system recognizes viral antigens displayed on infected hepatocyte surfaces: CD8+ cytotoxic T cells kill infected cells, and recruited inflammatory cells (macrophages, NK cells, neutrophils) release reactive oxygen species and proteases that cause bystander damage. The mechanisms that eliminate the infection simultaneously destroy liver tissue — hepatocyte damage is the collateral cost of antiviral immunity.

This immune-mediated pathogenesis explains several clinical observations: patients with stronger immune responses often have more severe acute disease; immunocompromised patients may have high viral loads with little hepatocyte killing; and the same immune processes that resolve acute infection also drive progressive fibrosis in chronic infection, where repeated rounds of hepatocyte death and immune activation stimulate stellate cells to deposit collagen.