Serological Markers of Hepatitis B Virus (HBV) Infection

Note: Harsh Mohan's textbook of pathology is not in the library, but both major Robbins books are available. The content below is drawn from Robbins & Kumar Basic Pathology (Fig. 14.10) and Robbins, Cotran & Kumar Pathologic Basis of Disease (Fig. 18.11), which contain identical, authoritative detail on this topic.

HBV Antigens and Proteins

Serological Markers - Detailed

1. HBsAg (Hepatitis B Surface Antigen)

• First marker to appear in serum, even before onset of symptoms (during incubation period)
• Peaks during acute symptomatic disease
• In self-limiting infection: declines to undetectable by 12 weeks (may persist up to 24 weeks)
• In chronic infection: persists indefinitely - the hallmark of chronic HBV
• Used for: diagnosis, blood bank screening, vaccination target

2. Anti-HBs (Antibody to HBsAg)

• Appears after resolution of acute disease, usually weeks to months after HBsAg disappears
• Indicates recovery and immunity
• Persists for life - basis of vaccination (HBsAg-containing vaccines)
• NOT produced in chronic HBV infection
• "Window period": gap between disappearance of HBsAg and appearance of anti-HBs - diagnosed in this period by IgM anti-HBc

3. HBeAg (Hepatitis B e Antigen)

• Appears in serum shortly after HBsAg (early in infection)
• Marker of active viral replication and high infectivity
• Persistence of HBeAg = strong indicator of progression to chronic hepatitis
• In resolved infection, it disappears as the infection peaks and wanes
• Caveat: HBeAg-negative mutant strains (precore mutants) exist - these do not produce HBeAg but still replicate and express HBcAg; HBV DNA remains detectable

4. Anti-HBe (Antibody to HBeAg)

• Appears as acute infection peaks and begins waning
• Signifies infection is on the wane
• In chronic infection: anti-HBe antibody is not produced or appears only very late

5. HBcAg (Hepatitis B Core Antigen)

• NOT detectable in serum - remains within hepatocytes
• Can be demonstrated only in liver biopsy (immunohistochemistry)
• Antibodies against it (anti-HBc) are the key serum markers

6. IgM Anti-HBc (IgM Antibody to HBcAg)

• Becomes detectable shortly before onset of symptoms, concurrent with elevated serum aminotransferases (reflecting hepatocyte destruction)
• Key marker during the "window period" when HBsAg has disappeared but anti-HBs has not yet appeared
• Over months, IgM anti-HBc is replaced by IgG anti-HBc

7. Total Anti-HBc (IgG Anti-HBc)

• Includes both IgM and IgG fractions
• IgG anti-HBc persists for life, even in chronic infection
• Total anti-HBc is elevated in both resolved and chronic infection
• Useful to distinguish: IgM anti-HBc = recent infection; IgG anti-HBc = past/chronic infection

8. HBV DNA (and HBV DNA Polymerase)

• Detectable in serum shortly after HBsAg
• Most sensitive marker of active viral replication
• Persists in chronic infection along with HBeAg
• Used to monitor antiviral treatment response

Classic Serology Graph (Robbins Fig. 14.10)

Summary Table: Interpretation of Serology Patterns

Key Points for SAQ

1. HBsAg is the first marker; its persistence beyond 6 months defines chronicity
2. Anti-HBs = immunity (from infection or vaccine); not seen in chronic disease
3. IgM anti-HBc is the only marker present during the window period
4. HBeAg + HBV DNA = active replication + high infectivity
5. HBcAg is never detected in serum - only in liver biopsy
6. Precore/core promoter mutants can have active infection with negative HBeAg but positive HBV DNA
7. Anti-HBc (IgG) persists lifelong and marks past or ongoing HBV exposure