Robust and low-cost ELISA based on IgG-Fc tagged recombinant proteins to screen for anti-SARS-CoV-2 antibodies

• DOI: 10.1016/j.jim.2021.113082
• Publication Date: 2021-05-26T15:31:16Z
• Authors: Etienne Frumence; Grégorie Lebeau; Wildriss Viranaicken; Anthony Dobi; Damien Vagner; Mahary Lalarizo R...; Anne-Laure Sanden...; Claude Giry; Axelle Septembre-...; Loïc Raffray; Philippe Gasque
• Keywords: 0301 basic medicine; Recombinant protein; SARS-CoV-2; COVID-19; CHO cells; Enzyme-Linked Immunosorbent Assay; CHO Cells; Antibodies, Viral; Sensitivity and Specificity; Recombinant Proteins; COVID-19 Serological Testing; Immunoglobulin Fc Fragments; 3. Good health; [SDV] Life Sciences [q-bio]; 03 medical and health sciences; Cricetulus; Immunoglobulin G; Spike Glycoprotein, Coronavirus; Technical Note; Costs and Cost Analysis; Animals; Humans; ELISA; Serological assay

The development of new diagnostic assays become a priority for managing COVID-19. To this aim, we presented here an in-house ELISA based on the production of two major recombinant and high-quality antigens from SARS-CoV-2. Full-length N and S-RBD fragment proteins fused to mouse IgG2a-Fc were produced in the CHO cell line. Secreted recombinant proteins were easily purified with standard Protein A chromatography and were used in an in-house ELISA to detect anti-N and anti-RBD IgGs in the plasma of COVID-19 RTPCR-positive patients. High reactivity against recombinant antigens was readily detected in all positive plasma samples, whereas no recognition was observed with control healthy subject's plasmas. Remarkably, unpurified recombinant N protein obtained from cell culture supernatant was also suitable for the monitoring by ELISA of IgG levels in positive patients. This work provides an early prospection for low price but high-quality serological kit development.