[Heterologous epitopes in the central part of the hepatitis B virus core protein]

A set of plasmids was constructed determining synthesis of hybrid proteins with insertions of antigenic determinants of preS1 and preS2 regions of HBV in the middle part of HBcAg. The polypeptides containing the 31-36 or monomeric 94-105 preS1 epitopes were water-soluble and formed particles similar to the 27-nm ones of native HBcAg, possessing antigenic properties of both HBcAg and the inserted epitope, while the hybrids containing 133-143 of preS2 or a trimeric form of the 94-105 preS1 epitope became membrane-bound. Another hybrid encoded by plasmid pPS2M31 contained two regions of HBcAg modification: insertion of amino acids 133-143 a.a. (preS2 region) in the N-terminal part and 31-36 (preS1) in the middle part of the carrier. The immunogenicity of the epitope inserted into the middle part of the HBcAg molecule was an order of magnitude higher than that of the same epitope in the N-part of the protein; the fact might be important for constructing artificial immunogens.