DELETION OF THE MYRISTYLATION SIGNAL ALLOWS HIGH-LEVEL PRODUCTION OF THE HEPATITIS-B VIRUS LARGE SURFACE GLYCOPROTEIN PRES1 WITH VACCINIA VIRUS RECOMBINANTS

We have investigated the requirements necessary for high-level product ion of the hepatitis B virus (HBV strain ayw) large surface glycoprote in preS1 with vaccinia virus (VV) recombinants. In earlier studies, on ly nanogram amounts of preS1 could be obtained from cells infected wit h an appropriate recombinant VV carrying the preS1 gene under the tran scriptional control of a conventional VV promoter (p7.5). Here, we rep ort that the use of an improved promoter system, i.e., the bacteriopha ge T7 polymerase/VV hybrid expression system (T7/EMC system) in combin ation with a G-C conversion at position 5 of the preS1 open reading fr ame, deleting the myristylation moth of the polypeptide, results in an at least 12-fold increase in preS1 expression compared to the wild-ty pe preS1 expressed with the strongest homologous VV promoter system kn own so far. Although the T7/EMC promoter system was most effective, im proved expression of the modified preS1 (preS1dMyr) is independent fro m the promoter system used, from the insertion locus of the modified p reS1 within the VV genome and also from the cell line used for express ion studies.