Fig. 1.

Structure of HBV and HDV virions. Both viruses use HBV surface proteins (S-, M- and L-HBsAg) for their assembly. HBV icosahedral capsid is formed by multimerisation of its core protein (HBcAg) and contains one copy of the viral partially double-stranded DNA genome (or relaxed circular DNA, rcDNA) and the viral polymerase. HDV virions contain one copy of the viral circular, single-stranded RNA genome (that has 70% of sequence complementarity, allowing its folding into a rod-like structure), associated with both forms of its only protein (large and small delta antigen or S- and L-HDAg), forming the viral ribonucleoprotein (RNP).