An affordable anti-SARS-COV-2 spike protein ELISA test for early detection of IgG seroconversion suited for large-scale surveillance studies in low-income countries | medRxiv preprints (not peer reviewed)

Type Journal Article Author Renata G. F. Alvim Author Tulio M. Lima Author Danielle A. S. Rodrigues Author Federico F. Marsili Author Vicente B. T. Bozza Author Luiza M. Higa Author Fabio L. Monteiro Author Isabela C. Leitao Author Renato S. Carvalho Author Rafael M. Galliez Author Terezinha M. P. P. Castineiras Author Alberto Nobrega Author Leonardo H. Travassos Author Orlando C. Ferreira Author Amilcar Tanuri Author Andre M. Vale Author Leda R. Castilho URL https://www.medrxiv.org/content/10.1101/2020.07.13.20152884v3 Rights © 2020, Posted by Cold Spring Harbor Laboratory. This pre-print is available under a Creative Commons License (Attribution-NonCommercial-NoDerivs 4.0 International), CC BY-NC-ND 4.0, as described at http://creativecommons.org/licenses/by-nc-nd/4.0/ Pages 2020.07.13.20152884 Publication medRxiv ISSN 2015-2884 Date 15/07/2020 Extra Publisher: Cold Spring Harbor Laboratory Press DOI 10.1101/2020.07.13.20152884 Library Catalog www.medrxiv.org Language en Abstract Background: Accurate serological tests are essential tools to allow adequate monitoring and control of COVID-19 spread. Production of a low-cost and high-quality recombinant viral antigen can enable the development of reliable and affordable serological assays, which are urgently needed to facilitate epidemiological surveillance studies in low-income economies. Methods: Trimeric SARS-COV-2 spike (S) protein was produced in serum-free, suspension-adapted HEK293 cells. Highly purified S protein was used to develop an ELISA, named S-UFRJ test. It was standardized to work with different types of samples: (i) plasma or serum from venous blood samples; (ii) dried blood spots (DBS) from blood drops collected by finger prick. Findings: We developed a cost-effective, scalable technology to produce S protein based on its stable expression in HEK293 cells. The S-UFRJ ELISA displayed 98.4% specificity and sensitivity above 90% already 10 days after symptoms onset, allowing early detection of anti-S IgG seroconversion. Endpoint titers were shown to correlate with virus neutralization assessed as PRNT90. There was excellent agreement between plasma and DBS samples, significantly simplifying sample collection, storing and shipping. The overall cost per test was estimated to be approximately one US dollar. Interpretation: The S-UFRJ assay developed herein meets the quality requirements of high sensitivity and specificity. The low cost and the use of mailable DBS samples allow for serological surveillance of populations regardless of geographical and socio-economic aspects, with special relevance for public health policy actions in low-income countries.