2. Core Antigen and Its Antibodies

2. Core Antigen and Its Antibodies

In the nuclei of liver cells of hepatitis B patients, immunoelectron microscopy often reveals spherical structures about 27 nanometers in diameter. Occasionally, these structures can also be seen in the cytoplasm of liver cells. Later, this structure was named Core Antigen (HBcAg). The peripheral serum of hepatitis patients does not contain Core Antigen, but its antibody, i.e., Core Antibody, can be detected. Core Antibody typically appears shortly after infection with the Hepatitis B Virus, usually 1–2 months after the Surface Antigen becomes positive, coinciding with the appearance of hepatitis symptoms and elevated transaminase levels. The Surface Antigen in acute hepatitis B is transiently positive, but before the Surface Antigen turns negative, surface antibodies often become positive. About four months before the surface antibodies turn positive, or even earlier, Core Antibody can be detected. Chronic carriers, although they do not test positive for surface antibodies, almost always test positive for Core Antibody. In summary, the appearance of Core Antibody indicates that the infection is still ongoing; this antibody offers no protection, cannot prevent reinfection, nor is it a sign of recovery—it merely reflects the active replication of the hepatitis virus. For patients whose hepatitis symptoms have not yet disappeared but whose Surface Antigen has already turned negative, if Core Antibody is positive, it indicates that the patient is still infected with and replicating the hepatitis virus. There is also a correlation between Core Antibody and DNA polymerase: usually about 41 days after infection with the Hepatitis B Virus, DNA-P begins to test positive, and 59 days later Core Antibody turns positive. At the same time, most patients' transaminase levels may exceed normal. Once Core Antibody appears, it can remain positive for more than five years, serving as the longest-lasting marker of the hepatitis virus in the human body.