High-level expression, purification and production of the fungal immunomodulatory protein-gts in baculovirus-infected insect larva

Fip-gts, a fungal immunomodulatory protein (Fip) isolated from Ganoderma tsugae (gts), has been reported to possess therapeutic effects in the treatment of cancer and autoimmune disease. To cost-effectively produce Fip-gts and bypass the bottleneck involved in its time-consuming purification from G. tsugae, in this study, we incorporated the SPbbx secretion signal into recombinant baculovirus for expressing glycosylated and bioactive rFip-gts in baculovirus-infected insect cells and Trichoplusia ni larva. This is the first study to employ the aerosol infecting T. ni larva with recombinant baculovirus for economical and high-level production of foreign proteins. In this study, one purification could yield 10 mg of rFip-gts protein merely from ~100 infected T. ni larvae by aerosol inoculation, corresponding to 5 L (5×109 cells) of the infected Sf21 culture. In addition, the rFip-gts purified from T. ni larvae could induce the expression of interleukin-2 in murine splenocytes with an immunoresponsive level similar to that induced by LZ-8 (a known potent immunomodulatory protein purified from Ling zhi, Ganoderma lucidum). Thus, our results demonstrated that the larva-based baculovirus expression system can successfully express rFip-gts with the assembling capability required for maintaining immunomodulatory and anticancer activity. Our approach will open a new avenue for the production of rFip-gts and facilitate the immunoregulatory activity of rFip-gts available in the future.