Effect of trimerization motifs on quaternary structure, antigenicity, and immunogenicity of a noncleavable HIV-1 gp140 envelope glycoprotein.

The external domains of the HIV-1 envelope glycoprotein (gp120 and the gp41 ectodomain, collectively known as gp140) contain all known viral neutralization epitopes. Various strategies have been used to create soluble trimers of the envelope to mimic the structure of the native viral protein, including mutation of the gp120-gp41 cleavage site, introduction of disulfide bonds, and fusion to heterologous trimerization motifs. We compared the effects on quaternary structure, antigenicity, and immunogenicity of three such motifs: T4 fibritin, a GCN4 variant, and the Escherichia coli aspartate transcarbamoylase catalytic subunit.

Chimeras of duck and heron hepatitis B viruses provide evidence for functional interactions between viral components of pregenomic RNA encapsidation.

Packaging of hepadnavirus pregenomic RNA (pgRNA) into capsids, or encapsidation, requires several viral components. The viral polymerase (P) and the capsid subunit (C) are necessary for pgRNA encapsidation. Previous studies of duck hepatitis B virus (DHBV) indicated that two cis-acting sequences on pgRNA are required for encapsidation: epsilon, which is near the 5' end of pgRNA, and region II, located near the middle of pgRNA.

Underrepresentation of the 3' region of the capsid pregenomic RNA of duck hepatitis B virus.

The pregenomic RNA (pgRNA) of hepadnaviruses is packaged into capsids where it is reverse transcribed to yield mature DNA genomes. This report describes differences between the 3' region and other regions of the pgRNA isolated from capsids. Analysis of capsid pgRNA isolated by using an established method involving micrococcal nuclease treatment demonstrated reduced levels of the 3' region of the pgRNA compared to the 5' region.

Characterization of the cis-acting contributions to avian hepadnavirus RNA encapsidation.

Previous analysis of duck hepatitis B virus (DHBV) indicated the presence of at least two cis-acting sequences required for efficient encapsidation of its pregenomic RNA (pgRNA), epsilon and region II. epsilon, an RNA stem-loop near the 5' end of the pgRNA, has been characterized in detail, while region II, located in the middle of the pgRNA, is not as well defined. Our initial aim was to identify the sequence important for the function of region II in DHBV.

Identification and characterization of a novel replicative intermediate of heron hepatitis B virus.

We have identified and characterized a novel intracellular DNA replicative intermediate that is synthesized by heron hepatitis B virus (HHBV) and not by other avian hepadnaviruses. The new DNA form is synthesized in all host cells tested. The HHBV nucleic acid template, and not HHBV proteins, is responsible for the formation of the new form.