The Pre-S Region of Hepadnavirus Envelope Proteins

The biosynthesis and biological properties of hepadnavirus envelope (env) proteins containing the pre-S region are described in this chapter. Abundant experimental evidence indicates that the pre-S region of hepadnavirus env proteins has essential biological functions. These are (1) involvement in virus attachment to hepatocytes, (2) elicitation of virus-neutralizing antibodies, (3) high antigenicity and immunogenicity, (4) regulation of the genetic restriction of the immune response, and (5) regulation of the process of virus particle assembly. It is also suggested that the biosynthesis of hepatitis B virus (HBV) env proteins containing the pre-S region might differ at different stages of hepatitis B infections. In contrast to HBsAg subviral particles, P39/GP42 and GP33/GP36 are substantial and not minor components of the HBV envelope. The pre-S region of hepadnavirus env proteins can be mimicked very successfully with synthetic peptide analogs. Consequently, such synthetic peptides have become important resources for the development of synthetic vaccines against hepatitis B and for the preparation of diagnostic reagents.