Efficient Low Cost Protein Factories: Expression of Human Proteins in Baculovirus Infected Insect Larvae

Human adenosine deaminase, a key purine salvage enzyme essential for immune competence, has been overproduced in Spodoptera frugipuda cells and in Trichoplusia ni cabbage looper larvae infected with recombinant baculovirus. The coding sequence of human adenosine deaminase was recombined into a baculovirus immediately downstream from the strong polyhedrin gene promoter. Approximately 60 hours after infection of insect cells with the recombinant virus, maximal levels of intracellular adenosine deaminase mRNA, protein and enzymatic activity were detected. The recombinant human adenosine deaminase represented 10 of the total cellular protein and exhibited a specific activity of 70 unitsmg protein in crude homogenate. When the recombinant virus was injected into insect larvae, the maximum recombinant enzyme was produced four days post infection and represented about 2.0 of the total insect protein with a specific activity of 10-25 unitsmg protein.