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

Braz J Microbiol. 2022 Sep;53(3):1263-1269. doi: 10.1007/s42770-022-00753-x. Epub 2022 Apr 14.

Abstract

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 Ni2+ 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 Ni2+ 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.

Keywords: COVID-19; High throughput; Magnetic beads; Magnetic immunoassay; SARS-CoV-2.

MeSH terms

  • Antibodies, Viral
  • COVID-19*
  • Escherichia coli / genetics
  • Humans
  • Immunoassay / methods
  • Immunoglobulin G
  • Magnetic Phenomena
  • SARS-CoV-2* / genetics
  • Spike Glycoprotein, Coronavirus / genetics

Substances

  • Antibodies, Viral
  • Immunoglobulin G
  • Spike Glycoprotein, Coronavirus
  • spike protein, SARS-CoV-2