EXPRESSION AND CHARACTERIZATION OF THE HEPATITIS-E VIRUS ORF3 PROTEININ THE METHYLOTROPHIC YEAST, PICHIA-PASTORIS

We have used the methylotrophic yeast, Pichia pastoris, to express the open reading frame 3 (ORF3) of the hepatitis E virus (HEV). The ORF3 gene codes for a 123-amino-acid protein that contains highly immunodom inant epitopes and is a potentially useful diagnostic and immunoprophy lactic antigen. The expressed protein showed positive on immunoblots p robed against antibodies raised in rabbit and infected human patient s era. In order to optimize the ORF3 protein expression, we have examine d the regulated expression of this protein and characterized it. Unlik e its expression in E. coli, the ORF3 protein was present in both the soluble and insoluble fractions of the cell lysate. The expressed prot ein is not glycosylated and does not undergo any major processing in t he host strain.