Interpreting Hepatitis B Serologies

Summary

Dr. Nina Kim from the University of Washington explains the complexities of interpreting hepatitis B serologies. She provides an in-depth overview of the virus's key structures and the evolution of serologic markers during acute and chronic infections. Key markers such as hepatitis B surface antigen, surface antibody, and core antibody are discussed in detail, highlighting their roles in diagnosing and understanding immunity or infection status. The session emphasizes the importance of a standard hepatitis B panel in determining an individual’s immune status and history of exposure, with a focus on understanding various serologic profiles.

Takeaways

• 😀 Hepatitis B serology can be challenging, but understanding the evolution of viral markers helps clinicians interpret different profiles.
• 😀 Hepatitis B virus (HBV) is a partially double-stranded DNA virus with key components including the nucleocapsid core and the envelope.
• 😀 Hepatitis B surface antigen (HBsAg) is the primary marker of active infection and is the first detectable serologic marker after exposure to the virus.
• 😀 Surface antigen can circulate as part of the virion or independently as viral particles, and can be directly measured in blood.
• 😀 Hepatitis B e antigen (HBeAg) is secreted into the bloodstream, while the core antigen is part of the viral core and cannot be directly measured.
• 😀 Three main antibodies are produced in response to HBV infection: anti-HBs (surface antibody), anti-HBe (e antibody), and anti-HBc (core antibody).
• 😀 Anti-HBs indicates protection or immunity against HBV, while anti-HBc and anti-HBe show exposure to the virus without conferring immunity.
• 😀 During acute infection, HBsAg appears first, followed by the core antibody, and later, the surface antibody appears in individuals who clear the virus.
• 😀 A person with chronic infection will show persistent HBsAg, high HBV DNA levels, and may have a positive core antibody but no surface antibody.
• 😀 Individuals who are vaccinated against HBV will only show anti-HBs and no other serologic markers, confirming immunity without prior exposure.

Q & A

What are the main targets of serologic testing in hepatitis B?

The main targets of serologic testing in hepatitis B are the hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and hepatitis B core antibody (anti-HBc). These markers help identify the phase of infection and the immune status of an individual.

What is the significance of hepatitis B surface antigen (HBsAg) in diagnosis?

Hepatitis B surface antigen (HBsAg) is a key marker of active infection. It can be found in both acute and chronic hepatitis B infections. The presence of HBsAg in the blood indicates that the person is infectious.

How is hepatitis B e antigen (HBeAg) related to the infection?

Hepatitis B e antigen (HBeAg) is a nucleocapsid protein secreted into the circulation. Its presence suggests active viral replication, and it is used to monitor the level of viral activity, especially in chronic hepatitis B patients.

Why is hepatitis B core antigen not measured in the blood?

Hepatitis B core antigen is part of the viral core and is not measurable in the blood directly because it is encapsulated in the virion. Only its antibody, anti-HBc, can be detected as an indicator of infection.

What does the presence of anti-HBs (hepatitis B surface antibody) indicate?

The presence of anti-HBs (hepatitis B surface antibody) indicates immunity to hepatitis B, either from vaccination or recovery from a previous infection. It is the main marker of hepatitis B seroprotection.

How does the immune response differ between an acute and chronic hepatitis B infection?

In acute hepatitis B, the body produces antibodies like anti-HBc and eventually anti-HBs if the infection resolves. In chronic hepatitis B, surface antigen (HBsAg) remains present, and there is no development of anti-HBs, indicating a failure of the immune system to clear the virus.

What does a profile of isolated core antibody (anti-HBc) suggest?

Isolated core antibody (anti-HBc) usually indicates previous exposure to hepatitis B, and the person may have cleared the virus. It may also indicate occult hepatitis B in individuals who have chronic infection with an inability to produce HBsAg.

What serological markers are typically used to diagnose acute hepatitis B?

The diagnosis of acute hepatitis B is typically based on the presence of hepatitis B surface antigen (HBsAg), hepatitis B DNA, core IgM antibody, and total core antibody (anti-HBc). Surface antibody (anti-HBs) is usually not detectable during acute infection.

How can hepatitis B be differentiated from immunity due to vaccination versus prior infection?

Hepatitis B immunity from vaccination is characterized by the presence of only surface antibody (anti-HBs), while immunity due to prior infection is indicated by the presence of both anti-HBs and anti-HBc.

What are the key differences between resolved hepatitis B infection and chronic hepatitis B?

In resolved hepatitis B, surface antigen (HBsAg) and viral DNA are absent, while core antibody (anti-HBc) and surface antibody (anti-HBs) are present. In chronic hepatitis B, HBsAg and viral DNA are persistent, and there is no development of anti-HBs.