- it has an efficient genomic design of four overlapping open reading frames,
- it utilizes successive strand synthesis and reverse transcription similar to retroviruses, and
- it has both glucocorticoid- and hepatocyte-specific enhancing elements.
Viral replication can be documented by measuring HBeAg (a component of the core gene product) or HBV-DNA (by a non-PCR method) in serum.
Laboratory diagnosis of Hepatitis B virus infection
- Detection of Viral Markers:Diagnosis of Hepatitis B infection rests on serological demonstration of the viral markers and can be carried out by detection of HBsAg, anti-HBs, HBeAg, anti HBe, IgM anti-HBc, IgG-anti-HBc and HBV DNA in the serum.
- HBsAg is the most important serological marker for identifying infection. It is the first marker to appear in the blood after infection. It is usually detectable 2-6 weeks in advance of clinical and biochemical evidence of hepatitis and persists throughout the clinical course of disease. It disappears with resolution of infection and persists in chronic infection.
- IgM anti-HBc is essential for the diagnosis of acute infection, but is also seen occasionally in very active chronic hepatitis.
- Anti-HBc antibodies develop and persist after all HBV infections. The loss of HBsAg and development of anti-HBc signals resolution of acute infection.
- Anti-HBs also occurs post vaccination, but anti-HBc will not be present in such cases.
Chronic infection is manifested by persistent HBsAg. Markers of viral replication such as HBeAg and HBV-DNA (non-PCR method) are detectable during the early high replication phase, but are not detectable during the later quiescent low replication phase. HBeAg is not a reliable marker of HBV replication when a precore variant is responsible for the infection. Such cases will be HBeAg negative, anti-HBe positive, but HBV-DNA (by a non-PCR method) positive