Hepatitis A virus - Classification, Morphology, Genome, Properties

Classification of Hepatitis A virus

The classification of Hepatitis A virus is:

Realm: Riboviria

Kingdom: Orthornavirae

Phylum: Pisuviricota

Class: Pisoniviricetes

Order: Picornavirales

Family: Picornaviridae

Genus: Hepatovirus

Species: Hepatovirus A

Morphology of Hepatitis A virus

Hepatovirus A is a small, non-enveloped virus measuring 27 nm in diameter with icosahedral symmetry. Hepatitis A virus has a single-stranded positive-sense liner RNA genome which is approximately 7.5kb. The capsid consists of multiple copies of 3-4 proteins (VP1 to VP4).

Genome of Hepatitis A virus

The viral genome of Hepatitis A virus can be divided into 3 parts:

1. A 5’ non-coding region (NCR) covalently linked to viral protein Vpg (733 nucleotides)

2. A short 3’ NCR terminating in a poly (A) tail

3. A single open reading frame (ORF) that appears to encode all of the viral proteins:

• The 5’ region of ORF codes for the major structural proteins of the virus (VP1-VP4)

• The 3’ region of ORF encodes a protease, which processes the polyprotein; a polymerase and other functions involved in genome replication

Antigenetically, the Hepatitis A virus (HAV) is highly conserved. It has a single serotype in spite of 4 genotypes differing by around 20% in nucleotide sequence. Most human strains belong to genotypes I or III.

Other properties of Hepatitis A virus

• Hepatitis A virus is exceptionally stable

• another property of the Hepatitis A virus is, it is ether resistant

• stable at pH 3.0

• relatively resistant to inactivation by heat (withstands 60°C for 1 hour), lipid solvents such as ether and chloroform, the action of detergents, and drying