Association Between Transplantation Antigens and a Viral Membrane Protein Synthesized from a Mammalian Expression Vector

Cells infected or transformed by adenovirus-2 express complexes of the viral E19 protein and class I transplantation antigens. To eliminate the complication of the numerous metabolic changes in adenovirus-infected and -transformed cells, we detached the E19 gene from its viral background by constructing transient expression vectors where the E19 coding sequence is flanked by the SV40 early promoter and the 3' region of the rabbit beta-globulin gene. E19 production was assayed 2 days after transfection of monkey COS or human HeLa cells with vector DNA. Efficient E19 gene expression depends on the presence of an intron (the second beta-globin intron), and the E19 protein is properly processed and anchored in the plasma membrane of transfected cells. The vector-synthesized E19 protein is also associated with class I transplantation antigens in human cells, since a fraction of it is coprecipitated both with antiserum against HLA antigens and with monoclonal antibodies against beta 2-microglobulin.