Antibody to HBcAg (anti-HBc) rises first. As a generalisation, the detection of IgM antibody specific to the hepatitis B core is the primary indicator of acute infection. It usually appears at or just before the onset of symptoms and remains detectable for at least 6 months. The IgG component of anti-HBc usually persists for life. Anti-HBe is the second antibody to appear and is associated with the rapid clearance of HBeAg. Later, anti-HBe declines and persists for only a few months or years if there is no active viral replication.
The antibody to HBsAg, anti-HBs, may not become detectable for 3-6 months after acute infection. It is associated with resolution of the illness. This antibody is recognised as the marker of immunity to HBV. There is a range of variations in the serological profile and when in doubt an expert opinion can be sought. For example, in some patients who clear HBsAg and recover clinically, the anti-HBs antibody may only be present at low levels or remains below the level of detection.
Between 1% and 10% of infected adults and older children develop chronic infection. Adults who develop chronic HBV are not usually immuno suppressed, but when they are, chronic infection is common. More than 85-95% of newborns and children infected under the age of 3 years, born to HBeAg positive mothers, become chronic carriers. This is thought to occur because of the immunological immaturity in the child and the effect of maternal HBeAg in utero. Those carriers infected in early life have an increased risk of both chronic persistent and chronic active hepatitis. From a laboratory perspective, chronic infection is defined as the persistence of HBsAg in the blood for a period of 6 months or more. The serological picture depends on the degree of viral activity in chronically infected hepatocytes.
A recently infected chronic carrier will show evidence of ongoing viral replication in liver cells. HBeAg and HBV DNA can be detected in blood for months or years after acute infection. High levels of anti-HBc IgM antibody are no longer present.