Development of single chain variable fragment (scFv) against SARS-CoV-2

Abstract

For the last one year, severe acute respiratory syndrome coronavirus 19 (SARS-CoV-19) has become the most urgent pathogenic problem as threatening health of all the human on earth with terrible pandemic contagiousness. The recent emergence of new virus, SARS-CoV-19, has changed social living style and taken our happiness of daily life away. Facing recent serious situation, the development of new antibodies against rapidly-spreading pandemic SARS-CoV-19 for early diagnosis and treatment is urgently required. Here, I developed the single chain variable antibody fragments (scFv) against SARS-CoV-19 for therapeutic purpose. First, human synthetic antibody library was constructed in Escherichia coli host. For antibody (scFv) screening, anchored periplasmic expression (APEx) system in which antibodies are displayed on inner membrane of E. coli by anchored-expression of antibodies was employed. And I prepared receptor binding domain (RBD) part of SARS-CoV-19 spike protein as screening target by protein synthesis with recombinant mammalian cell and following purification. After labeling spheroplast cells with RBD protein, which is conjugated with Alexa fluorescence dye, highly fluorescent cells were selectively sorted by FACS screening with high speed. After several rounds of sorting with synthetic antibody library, antibody candidates showing higher affinity to target antigen was finally isolated. Binding affinity of isolated antibodies was measured numerically by ELSIA analysis. After that, in order to increase screening efficiency, the optimization of antigen labeling concentration was performed and the result of screening was confirmed through individual colony analysis.