Which HBV antigen is most closely associated with transmissibility?

Which HBV antigen is most closely associated with transmissibility?

• A. HBsAg
• B. HBeAg
• C. HBcAg
• D. HBV

Answer: (B)

HBeAg is a marker of active HBV replication and high infectivity. When the virus replicates vigorously, the precore/core region produces HBeAg, which is secreted into the bloodstream. Its presence in serum correlates with a high viral load (HBV DNA levels) and a greater likelihood of transmitting the virus through blood, sexual contact, or from mother to child. If the immune system later clears HBeAg and anti-HBe appears, viral replication typically drops and infectivity decreases. In contrast, HBsAg simply signals that someone is infected (acute or chronic), but doesn’t by itself indicate how actively the virus is replicating or how infectious the person is. HBcAg is a core antigen largely found inside infected cells and isn’t routinely used in serum to gauge transmissibility. The HBV term refers to the virus, not an antigen detected in the blood.

HBeAg is a marker of active HBV replication and high infectivity. When the virus replicates vigorously, the precore/core region produces HBeAg, which is secreted into the bloodstream. Its presence in serum correlates with a high viral load (HBV DNA levels) and a greater likelihood of transmitting the virus through blood, sexual contact, or from mother to child. If the immune system later clears HBeAg and anti-HBe appears, viral replication typically drops and infectivity decreases.

In contrast, HBsAg simply signals that someone is infected (acute or chronic), but doesn’t by itself indicate how actively the virus is replicating or how infectious the person is. HBcAg is a core antigen largely found inside infected cells and isn’t routinely used in serum to gauge transmissibility. The HBV term refers to the virus, not an antigen detected in the blood.