Expression of recombinant human tumor necrosis factor-a in a baculovirus expression system

A cDNA fragment coding human tumor necrosis factor-alpha (TNF-a) was inserted into the vector pSXIVVI‡X3 with the control of Syn XIV promoter. The Sf9 cells (Spodoptera frugiperda) were co-transfected with the recombinant plasmid and TnNPV DNA (Trichoplusia ni nuclear polyhedrosis virus DNA). Cells infected with recombinant virus synthesized TNF-a protein at a level of about 38% of total cellular protein. TNF-a activity in infected cells was measured by L929 cytotoxic assay, the highest expression level, 1.5* 104 U/106 cells, was obtained at 76 h after infection. Western blot analysis of protein extracts from infected larvae showed that the virus-mediated TNF-a had immunoreactivity