Large surface proteins of hepatitis B virus containing the pre-s sequence

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Hepatitis B virus (HBV) DNA has an open reading frame coding for proteins.
• Previously identified viral surface antigens originate from the third or fourth initiation signals.

Purpose of the Study:

• To identify and characterize novel proteins within HBV particles.
• To investigate the immunological properties and origins of these proteins.

Main Methods:

• Protein identification in HBV particles and surface antigen filaments.
• Immunological cross-reactivity assays using monoclonal antibodies.
• Proteolytic cleavage analysis and subtype-specific size difference determination.

Main Results:

• A larger protein, P39, and its glycosylated form, GP42, were discovered in HBV particles.
• P39/GP42 demonstrated partial homology to known viral proteins (P24/GP27, GP33/GP36).
• The unique sequence of P39/GP42 bound to HBV-specific monoclonal antibodies, suggesting surface exposure and immunogenicity.

Conclusions:

• P39 likely originates from the first initiation signal of the HBV open reading frame.
• The N-terminal (pre-s coded) portion of P39 is exposed on the viral surface and is potentially highly immunogenic.
• A model explaining the generation of three distinct proteins from the HBV envelope open reading frame is proposed.