The Oral Transfection of Spodoptera exigua (Lepidoptera: Noctuidae) Larvae via an Artificial Diet as a Strategy for Recombinant Protein Production

Insects present extraordinary potential for obtaining recombinant proteins, both in terms of the quantity and quality of the synthesized product. This work proposes the use of artificial diets including pDNA as an oral transfection system for the Lepidoptera Spodoptera exigua. It is hypothesized that oral transfection can lead to the effective expression of the reporter genes carried in plasmids. Prior to their incorporation into the artificial diet, plasmids (pCMVβ and pEGFP-N2) were protected from inactivation in the digestive tract by chitosan nanoparticulation. The survival of plasmids and their oral uptake by larvae was evaluated, as well as the persistence of pDNA in larvae throughout their ontogeny. The results confirmed that transfection occurred and that pDNA persisted during the ontogeny, even after discontinuing plasmid administration. The transcription of reporter genes was quantified by qRT-PCR, and the results indicate a dose-dependent synthesis of mRNA as the inclusion level of pDNA in diets increased. Moreover, the measurement of the biological activity of the recombinant proteins (β-galactosidase activity and green fluorescence) paralleled the results obtained for gene transcription, also dose-dependently. Therefore, effective oral transfection is feasible in S. exigua, provided that pDNA is protected against gut inactivation prior to its incorporation in artificial diets.