Gastroenterology and Hepatology

Molecular Biology of Hepatitis A, B, C, D and E Viruses

Hepatitis A virus (HAV) belongs to the family Picornaviridae and genus Hepatovirus. It is usually spherical in shape and non-enveloped. HAV has a positive single stranded RNA which is enclosed inside a protein shell called as capsid. HAV is named as hepatogenous virus. It is said to have a poor internal ribosome entry site. Hepatitis B virus (HBV) belongs to the family of small DNA viruses. HBV undergoes replication in the hepatocytes of the host by reverse transcription of viral RNA. After the infection the virion DNA gets converted to nucleus and assembles to minichromosome forming a template for the viral mRNA synthesis. Hepatitis C virus (HCV) belongs to the genus Hepacivirus and the domestic Flaviviridae. HCV has an outermost covering of lipid membrane envelope. Two glycoproteins E1 and E2 are covalently embedded into the lipid membrane by means of the disulphide bridges. The genome of the HCV is positive sense single stranded RNA. E1 and E2 glycoproteins play a major role in the immune system interactions. Hepatitis D virus (HDV) is also called as hepatitis delta virus. It is spherical shaped enveloped virus. The genome of the HDV is negative sense single stranded closed and circular RNA.Hepatitis E is a single stranded RNA virus with a small envelope belonging to the family Hepeviridae.