HBVDNA

HBV DNA refers to the genetic material of the Hepatitis B virus. The HBV genome is a compact, circular DNA about 3.2 kilobases in length that exists in virions as partially double-stranded, relaxed circular DNA (rcDNA). After infection of hepatocytes, rcDNA is repaired to covalently closed circular DNA (cccDNA), which serves as the reservoir and transcription template for viral RNAs.

The genome contains four overlapping open reading frames: S, which encodes the surface antigens (HBsAg); C, encoding core protein (HBcAg) and e antigen (HBeAg); P, encoding the polymerase with reverse transcriptase activity; and X, encoding the regulatory HBx protein. Regulatory elements and promoters control transcription of pregenomic RNA and subgenomic RNAs.

Replication occurs when cccDNA is transcribed by host RNA polymerase II to produce pregenomic RNA from which both mRNA and a template for reverse transcription are generated. The pregenomic RNA is encapsidated with the HBV polymerase and reverse-transcribed inside nucleocapsids to form new rcDNA. Mature nucleocapsids can be recycled to the nucleus to replenish cccDNA or budded and secreted as virions. The virus enters hepatocytes via the NTCP receptor, and the envelope is removed within the cytoplasm prior to nucleocapsid formation.

HBV DNA levels in serum, measured by PCR-based assays, indicate active replication and are used to diagnose infection, stage disease, and monitor therapy. Quantitative HBV DNA, alongside HBsAg, HBeAg status, ALT level, and genotype, informs treatment decisions. Antiviral therapy with nucleos(t)ide analogs (e.g., tenofovir, entecavir) suppresses HBV DNA replication but does not reliably eradicate cccDNA. Vaccination prevents infection by eliciting anti-HBs antibodies. Genotypes A through H influence regional epidemiology and, in some settings, response to therapy and disease progression.