Production of functional active human growth factors in insects used as living biofactories

• The present work describes the expression of different genetically engineered forms of three human growth factors in a system based on insect larva (Trichoplusia ni) infected by recombinant baculoviruses.
• This insect biofactory-based system is extremely efficient for expression of any kind of recombinant protein as it has been demonstrated for many different kind of proteins, some of them very difficult to express by conventional means.
• The results obtained in this work with the selected growth factor constructs demonstrated that insects represents an excellent substrate to produce these highly demanded molecules with application in different pathologies, biotechnology processes or in cosmetic.
• In our knowledge, the production yields obtained in this study represent the highest never reach with other technologies for any of the growth factors analysed.

Growth factors (GFs) are naturally signalling proteins, which bind to specific receptors on the cell surface. Numerous families of GFs have already been identified and remarkable progresses have been made in understanding the pathways that these proteins use to activate/regulate the complex signalling network involved in cell proliferation or wound healing processes. The bottleneck for a wider clinical and commercial application of these factors relay on their scalable cost-efficient production as bioactive molecules. The present work describes the capacity of Trichoplusia ni insect larvae used as living bioreactors in combination with the baculovirus vector expression system to produce three fully functional human GFs, the human epidermal growth factor (huEGF), the human fibroblast growth factor 2 (huFGF2) and the human keratinocyte growth factor 1 (huKGF1). The expression levels obtained per g of insect biomass were of 9.1, 2.6 and 3 mg for huEGF, huFGF2 and huKGF1, respectively. Attempts to increase the productivity of the insect/baculovirus system we have used different modifications to optimize their production. Additionally, recombinant proteins were expressed fused to different tags to facilitate their purification. Interestingly, the expression of huKGF1 was significantly improved when expressed fused to the fragment crystallizable region (Fc) of the human antibody IgG. The insect-derived recombinant GFs were finally characterized in terms of biological activity in keratinocytes and fibroblasts. The present work opens the possibility of a cost-efficient and scalable production of these highly valuable molecules in a system that favours its wide use in therapeutic or cosmetic applications.