A chimeric, carboxy-terminal truncated hepatitis B virus nucleocapsid (core)protein (HBc) that is engineered for both enhanced stability of self-assembledparticles and the substantial absence of nucleic acid binding by thoseparticles is disclosed. The chimeric protein molecule can include one or moreimmunogenic epitopes peptide-bonded to one or more of the N-terminus, theimmunogenic loop or the C-terminus of HBc. The enhanced stability of self-assembled particles is obtained by the presence of at least one heterologouscysteine residue near one or both of the amino-terminus and carboxy-terminusof the chimer molecule and the absence of the cysteine residues present in thenative sequence at HBc positions 48 and 107.
