Characterization of proteins associated with hepatitis delta virus

The number and size of proteins associated with hepatitis delta virus (HDV) from serum and liver (human, chimpanzee and woodchuck) in the acute and chronic stages of HDV infection were analysed by immunoblotting. HDV particles in serum were separated from serum proteins by gel filtration and peak fractions of HDV antigens were subjected to PAGE. Immunoblotting with human anti-HDV-positive sera and 125I-labelled Protein A revealed two bands of 27K and 29K. It was not possible to identify any core-like structure from liver homogenates by CsCl gradient centrifugation. HDV proteins from such gradients were degraded to a size of 14K as determined by immunoblotting. HDV RNA was found in fractions at a density of 1.5 g/ml. However, direct homogenization of liver tissue in gel electrophoresis sample buffer, followed by PAGE and immunoblotting resulted in identification of HDV-associated proteins of 27K and 29K, indicating that HDV proteins in liver tissue are the same size as those in serum, but that they degrade rapidly. There was no difference in size of HDV proteins in liver samples from humans, chimpanzees or woodchucks.