Abstract
1 Current Knowledge about the Pathogen 1.1 Characteristics of Hepatitis A Virus The clinical features of hepatitis A have been known for a long time. However, the pathogen (hepatitis A virus (HAV)) was firstly identified in 1973 with the aid of immune electron microscopy [1]. HAV is classified in the family of Picornaviridae , genus Hepatovirus . It is a small, spherical, non-enveloped virus with a diameter of approximately 30 nm. The capsid of the viral particle is made up of 60 copies of the three viral structural proteins VP1–VP3. The genome consists of a single- stranded (+)sense RNA molecule of 7,500 bases in length. The 5'' end of the genome is covalently bound to a small protein (VPg). The genome serves as messenger RNA and can be divided into three regions: a long open-reading frame (ORF) is flanked by the non-coding 5'' region and the non-coding 3'' region. The ORF encodes a polyprotein which is cleaved by proteolysis into the mature viral proteins. Two thirds of the genome code for non-structural proteins with enzymatic and regulatory functions. Translation is controlled by an ‘internal ribosomal entry site’ (IRES) located within the non-coding 5'' region [2]. Only one serotype of HAV has been identified so far. Analysis of HAV genome sequences has revealed 6 genotypes to date [3], with genotype I predominating worldwide. Genotypes IV–VI have only been observed in Old World monkeys. ...
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