Ultra-fast, high throughput and inexpensive detection of SARS-CoV-2 seroconversion

Abstract

A technique allowing high throughput, fast and low-cost quantitative analysis of human IgG antibodies reacting to SARS-CoV-2 antigens will be required to understand the levels of protecting antibodies in the population raised in response to infections and/or to immunization. We described previously a fast, simple, and inexpensive Ni2+ magnetic bead immunoassay which allowed detection of human antibodies reacting against the SARS-CoV-2 nucleocapsid protein using a minimal amount of serum or blood. A major draw-back of the previously described system was that it only processed 12 samples simultaneously. Here we describe a manually operating inexpensive 96 well plate magnetic extraction / homogenization process which allows high throughput analysis delivering results of 96 samples in chromogenic format in 12 minutes or in fluorescent ultrafast format which takes only 7 minutes. We also show that His tag antigen purification can be performed on the fly while loading antigens to the Ni2+ magnetic beads in a process which takes only 12 min reducing the pre analytical time and cost. Finally, we show that the magnetic bead immunoassay is antigen flexible and can be performed using either Nucleocapsid, Spike or Spike RBD. The method performed with low inter and intra assay variability using different antigens and detection modes and was able to deliver >99.5% specificity and >95% sensitivity for a cohort of 203 pre pandemic and 63 COVID-19 positive samples.