ABSTRACT
The hepatitis C virus is a small enveloped positive-strand RNA virus belonging to the genus Hepacivirus of the Flaviviridae family (Lindenbach et al., 2007). The HCV genome encodes a single precursor polyprotein of about 3,000 amino acids. This protein is cleaved co-and posttranslationally into functional structural and nonstructural proteins by host and viral proteases. The structural proteins assemble into HCV particles of about 55-60 nm in diameter (Kaito et al., 1994; Shimizu et al., 1996; Wakita et al., 2005). HCV is thought to adopt a classical icosahedral scaffold in which the two envelope glycoproteins E1 and E2 are anchored to the host cell-derived double-layer lipid envelope (Penin et al., 2004). E1 and E2 are type I transmembrane glycoproteins forming noncovalent heterodimers. Underneath the envelope lies the nucleocapsid which is probably composed of multiple copies of the core protein in complex with the viral genome (Penin et al., 2004). The nonstructural proteins have various functions involved in viral RNA replication and proteolytic processing: the two viral autoproteases NS2 and the serine protease NS3; the NS4A polypeptide, an essential cofactor for the NS3 protease; the NS4B and NS5A proteins; and finally the NS5B RNA-polymerase (Barth et al., 2006; Moradpour et al., 2007). The nonstructural proteins coordinate viral replication by the formation of a membrane-bound replication complex. Apart from these, an additional protein, termed F (for frameshift)-protein, has been proposed which is encoded by an overlapping reading frame in the core protein coding sequence.
