Virology USMLE Step 1 Practice Question
A 56-year-old male with a 20-year history of intravenous drug use presents to clinic with progressive fatigue, mild jaundice, and right upper quadrant discomfort. He denies alcohol use. Vital signs are stable. Laboratory studies show AST 95 U/L, ALT 120 U/L, total bilirubin 2.1 mg/dL, and albumin 3.8 g/dL. Anti-HCV antibodies are positive, and HCV RNA-PCR is positive at 850,000 IU/mL. A liver biopsy shows mild portal inflammation with preserved architecture. The patient asks why his infection has not cleared despite having detectable antibodies. Which of the following best explains the mechanism by which HCV establishes chronic infection in approximately 80% of infected individuals?
Answer choices
- ARapid mutation of the viral envelope glycoproteins (E1/E2) in the hypervariable region, generating antigenic variants that escape neutralizing antibodiesCorrect answer
- BProduction of viral NS5A protein that inhibits JAK1 kinase and blocks interferon-alpha signaling pathways
- CIntegration of viral RNA into hepatocyte chromosomal DNA, rendering the virus invisible to MHC-mediated antigen presentation
- DSelective tropism for CD4+ T lymphocytes, resulting in direct destruction of the cellular immune response
- EAcquisition of a host-derived lipid bilayer envelope during viral budding, which masks all immunogenic epitopes from antibody recognition
- FDownregulation of MHC class I molecules on chronically infected hepatocytes, preventing CD8+ T cell recognition and elimination
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