A magnetic bead immunoassay to detect high affinity human IgG reactive to SARS-CoV-2 Spike S1 RBD produced in Escherichia coli

• Published in: Brazilian journal of microbiology Vol. 53; no. 3; pp. 1263 - 1269
• Main Authors: Conzentino, Marcelo S., Gonçalves, Ana C. A., Paula, Nigella M., Rego, Fabiane G. M., Zanette, Dalila L., Aoki, Mateus N., Nardin, Jeanine M., Huergo, Luciano Fernandes
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.09.2022; Springer Nature B.V
• Subjects: Affinity; Affinity chromatography; Antibodies; Antigens; Beads; Binding; Biomedical and Life Sciences; Cell lines; Clinical Microbiology - Research Paper; COVID-19; Domains; E coli; Escherichia coli; Food Microbiology; Human populations; Immunization; Immunoassay; Immunoglobulin G; Immunology; Life Sciences; Low cost; Medical Microbiology; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Mycology; Pandemics; Public health; Receptors; Sensitivity; Seroconversion; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Vaccination; Vaccines; Viral diseases; COVID-19; Magnetic immunoassay; High throughput; Magnetic beads; SARS-CoV-2
• ISSN: 1517-8382; 1678-4405
• DOI: 10.1007/s42770-022-00753-x

Immunological assays to detect SARS-CoV-2 Spike Receptor Binding Domain (RBD) antigen seroconversion in humans are important tools to monitor the levels of protecting antibodies in the population in response to infection and/or immunization. Here we describe a simple, low cost, and high throughput Ni 2+ magnetic bead immunoassay to detect human IgG reactive to Spike S1 RBD Receptor Binding Domain produced in Escherichia coli. A 6xHis-tagged Spike S1 RBD was expressed in E. coli and purified by affinity chromatography. The protein was mobilized on the surface of Ni 2+ magnetic beads and used to investigate the presence of reactive IgG in the serum obtained from pre-pandemic and COVID-19 confirmed cases. The method was validated with a cohort of 290 samples and an area under the receiver operating characteristic curve of 0.94 was obtained. The method was operated with > 82% sensitivity at 98% specificity and was also able to track human IgG raised in response to vaccination with Comirnaty at > 85% sensitivity. The IgG signal obtained with the described method was well-correlated with the signal obtained when pre fusion Spike produced in HEK cell lines was used as antigen. This novel low-cost and high throughput immunoassay may act as an important tool to investigate protecting IgG antibodies against SARS-CoV-2 in the human population.