Expression of Epstein-Barr Virus Membrane Antigen gp340/220 in Mouse Fibroblasts Using a Bovine Papillomavirus Vector

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Abstract
Summary Epstein-Barr virus (EBV) membrane antigen glycoproteins gp340 and gp220 are encoded by a single gene. We have inserted this gene into a bovine papillomavirus (BPV) vector and expressed gp340/220 in mammalian cells under the control of the mouse metallothionein promoter. The proteins produced were of similar M r, showed similar antigenic specificity and were transported to the same subcellular location as the authentic gp340/220. The inclusion of heavy metal ions in the medium had no effect on the levels of gp340/220, which were approximately the same as those found in standard EBV-transformed lymphoblastoid cell lines, e.g. B95-8. Cells that expressed gp340/220 were selected by several rounds of fluorescence-activated cell sorting, but on passage they rapidly lost the ability to express this glycoprotein. In contrast to this we found that BPV-transformed cells expressing a truncated version of gp340/220 still produced it at significant levels after extended passage.