Ribonucleoprotein complexes of hepatitis delta virus

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Human hepatitis delta virus (HDV) is a subviral agent dependent on hepatitis B virus (HBV) for its envelope.
• The internal structure and composition of HDV particles remain largely uncharacterized.
• HDV possesses a small, single-stranded, circular RNA genome and multiple copies of the delta antigen.

Purpose of the Study:

• To elucidate the internal structure of HDV particles.
• To investigate the interaction between HDV RNA and delta antigen.
• To characterize HDV ribonucleoprotein (RNP) complexes in virions and infected cells.

Main Methods:

• UV cross-linking
• Equilibrium density centrifugation
• Immunoprecipitation
• Electron microscopy

Main Results:

• Evidence suggests delta antigen and genomic RNA form stable ribonucleoprotein (RNP) complexes within HDV virions.
• Electron microscopy revealed a spherical core-like structure (18.7 +/- 2.5 nm) for purified viral RNP.
• HDV-specific RNP complexes containing both genome and antigenome were isolated from infected cell nuclei.
• Equilibrium density analysis indicated approximately 70 delta antigen molecules per HDV RNA molecule in virions, and an average of 30 in nuclear RNPs.

Conclusions:

• Delta antigen and HDV RNA form stable RNP complexes, constituting the core structure of HDV virions.
• HDV RNP complexes are also present during viral genome replication in the nucleus.
• The stoichiometry of delta antigen to HDV RNA differs between virions and nuclear replication intermediates.