Conclusions
In this work, we show that SARS-CoV-2 recombinant S protein could be produced inexpensively after infection of R. nu larvae and easily purified later after a single chromatographic step. Noteworthy, the antigenic properties of this large, complex, highly glycosylated protein are retained, as evidenced during its application for developing a serologic ELISA test. One gram of insect larvae produces an amount of S protein sufficient for 150 determinations in the ELISA method. The scale-up of S protein production is linear in this biotechnological platform, avoiding the use of complex equipment like bioreactors. Thus, it is straightforward to conclude that our approach represents a rapid, easy, and cost-effective method for the production of recombinant S for diagnostic applications. We expect that our approach will bring new tools for serologic test producers to face the unprecedented demand for these products during the current COVID 19 pandemic.