Immunoblot analysis demonstrates that the large and small forms of hepatitis delta virus antigen have different C-terminal amino acid sequences

Antisera to a peptide representing the extreme carboxy terminus of the hepatitis delta virus antigen (HDAg) open reading frame (residues 197 to 211) recognized only the large (p27^δ) and not the small (p24^δ) form of HDAg in immunoblots of infected liver extracts, thereby providing direct proof that p27^δ and p24^δ differ in their carboxyl-terminal sequence and that p27^δ results from mutation within the stop codon terminating translation of p24^δ. Reactions with other peptide antisera demonstrated that multiple smaller virus-specified proteins were carboxy-terminally truncated forms of HDAg, and immunoprecipitation studies suggested that different forms of HDAg were present as heterologous complexes within the liver extract.