Orthohepadnavirus

A genus of viruses in the family Hepadnaviridae

Orthohepadnavirus is a genus of viruses in the family Hepadnaviridae. This genus includes viruses that primarily infect mammals, including humans. The most well-known species within this genus is the Hepatitis B virus, which is a significant human pathogen.

Virology

Orthohepadnaviruses are small, enveloped viruses with a partially double-stranded DNA genome. The genome is circular and approximately 3.2 kilobases in length. The viral particles are spherical and have a diameter of about 42 nm.

Genome

The genome of orthohepadnaviruses is unique in that it is partially double-stranded. It consists of a long, complete strand and a shorter, incomplete strand. The genome encodes four overlapping open reading frames (ORFs):

• The S ORF encodes the surface antigens (HBsAg).
• The C ORF encodes the core protein (HBcAg) and the e antigen (HBeAg).
• The P ORF encodes the viral polymerase.
• The X ORF encodes the X protein, which is involved in viral replication and pathogenesis.

Replication

Orthohepadnaviruses replicate through an RNA intermediate. After entry into the host cell, the viral genome is transported to the nucleus where it is converted into covalently closed circular DNA (cccDNA). This cccDNA serves as a template for transcription of viral mRNA and pregenomic RNA. The pregenomic RNA is then reverse transcribed into DNA by the viral polymerase, completing the replication cycle.

Pathogenesis

The most notable member of the Orthohepadnavirus genus is the Hepatitis B virus (HBV), which causes hepatitis B. HBV infection can lead to both acute and chronic liver disease. Chronic infection can result in liver cirrhosis and hepatocellular carcinoma.

Transmission

Hepatitis B virus is transmitted through contact with infectious body fluids, such as blood, semen, and vaginal secretions. Common routes of transmission include perinatal transmission, sexual contact, and sharing of needles.

Prevention and Treatment

Vaccination is the most effective way to prevent hepatitis B infection. The hepatitis B vaccine is safe and highly effective. For those already infected, antiviral medications can help manage the infection and reduce the risk of complications.

Related pages

• Hepatitis B
• Hepadnaviridae
• Viral hepatitis