Simultaneous synthesis and assembly of various hepatitis B surface proteins in Saccharomyces cerevisiae

Yeast transposon of class-1-based vectors, allowing integration at a series of chromosomal loci by homologous recombination with resident transposons, were constructed. Using such vectors, we have introduced several copies of an expression cassette encoding the major hepatitis B surface protein as well as expression cassettes encoding the middle (M) or/and the large (L) surface protein into Saccharomyces cerevisiae. In extracts of such strains, coassembly of the different proteins into a single lipoprotein structure is observed. This was demonstrated by immunoprecipitation of the major protein using monoclonal antibodies directed specifically against epitopes that are present only on the M or the L protein. These results show that hepatitis B surface antigen envelope proteins synthesized in yeast are able to assemble into structures composed of different polypeptides. This opens the possibility of producing in yeast a variety of particles carrying well-defined amounts of preS epitopes on their surface. Also, one can envisage the production of mixed particles containing different foreign epitopes on their surface, in defined relative abundance, which could be useful for vaccine applications.