Enhancing yield of infectious bursal disease virus structural proteins in baculovirus expression systems: Focus on media, protease inhibitors, and dissolved oxygen

Structural proteins of the poultry pathogen, infectious bursal disease viru s (IBDV), were expressed in the baculovirus/insect cell expression system. To date, several reports have indicated that animal virus structural protei ns are expressed only at low yield in this system. In this article, several factors were examined to enhance yield. These include medium, dissolved ox ygen level, and the addition (in vivo and in vitro) of protease inhibitors. Specifically, two media were compared, and SF-900 II was superior to Ex-Ce ll 401 for cell growth and IBDV protein expression. A cocktail of protease inhibitors including phenylmethyl sulfonyl fluoride (PMSF), leupeptin, and ethylenediamine tetraacetic acid (EDTA) minimized proteolysis in vitro. Als o, aprotinin and pepstatin A deterred product degradation in vivo and incre ased the product yield nearly 2-fold. Finally, in 3 L bioreactors, a dissol ved oxygen tension of 50% DO (air saturation) was optimal. Results demonstr ated that several relatively simple adjustments to the baculovirus system s ignificantly improved the yield of IBD virus structural proteins.