Engineering luminescent biosensors for point-of-care SARS-CoV-2 antibody detection

Abstract

Current serology tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies mainly take the form of enzyme-linked immunosorbent assays, chemiluminescent microparticle immunoassays or lateral flow assays, which are either laborious, expensive or lacking sufficient sensitivity and scalability. Here we present the development and validation of a rapid, low-cost, solution-based assay to detect antibodies in serum, plasma, whole blood and to a lesser extent saliva, using rationally designed split luciferase antibody biosensors. This new assay, which generates quantitative results in 30 min, substantially reduces the complexity and improves the scalability of coronavirus disease 2019 (COVID-19) antibody tests. This assay is well-suited for point-of-care, broad population testing, and applications in low-resource settings, for monitoring host humoral responses to vaccination or viral infection.As the vaccine deployment starts worldwide for COVID-19, broad antibody testing for SARS-CoV-2 faces severe limitations. Although nucleic acid testing is critical to detecting the virus, serological antibody tests are vital tools for monitoring the dynamic human humoral response to SARS-CoV-2 vaccination and viral infection 1 . Population-scale, longitudinal evaluation of antibody responses is needed to determine the strength and duration of immunity to the primary virus, to the variants, and to vaccines, which is important in informing public policy and vaccination strategies 2-7 . In addition, antibody tests serve as a complement or an alternative to nucleic acid diagnostics for patients with a low viral load or for low-resource areas where expensive reverse transcription polymerase chain reaction (RT-PCR) testing is difficult to access [8][9][10] . Serological tests also support therapeutic development through identification of either individuals who could serve as donors for convalescent serum therapeutics 11 , or patients with potentially strong neutralizing antibodies that can be produced in vitro as new antivirals and prophylactics 12,13 . All these applications would be greatly accelerated with an assay that is simple, rapid and high throughput, without sacrificing accuracy and sensitivity.Traditional serological assays are not optimal in the face of this broad pandemic. The most widely used laboratory serological tests take the form of enzyme-linked immunosorbent assays

Current molecular diagnostics assays for SARS-CoV-2 and emerging variants

“…NanoLuc was split into two and both arms fused with viral antigens. The antibodies bind with both the arms and reconstruct the NanoLuc, hence generating the luminescence 89% for S protein; 98% for N protein Elledge et al (2021) Colorimetric and SPR Detection of N gene of SARS-CoV2 by the use of gold nanoparticles capped with thiol-modified antisense oligonucleotides that are N gene specific. The binding of the target demonstrates a change in surface plasmon resonance.…”

SARS-CoV-2/COVID-19 laboratory biosafety practices and current molecular diagnostic tools

“…For example, Elledge et al . used rationally designed split luciferase antibody biosensors to detect antibodies in whole blood, serum, plasma, and to a lesser extent, saliva, within 30 min [54] . Despite these advancements, a gold standard method to validate both Ag- and Ab-RDTs remains lacking.…”

“…Apart from Ab-RDTs, other slower methods also exist, as summarized in Table 4 and Figure 3 D and E , for the detection of human-specific SARS-CoV-2 antibodies. These methods include enzyme linked immunosorbent assays (ELISA), CLIAs that employ indirect and sandwich ELISA techniques, and fluorescent microparticle immunoassays (FMI), all of which have been reviewed in detail elsewhere 7 , 24 , 54 , 55 .…”

Deciphering the Interaction between Neonatal Fc Receptor and Antibodies Using a Homogeneous Bioluminescent Immunoassay

“…The small size of NanoBiT fragments minimizes any steric impact on interacting proteins, and because of its bright bioluminescent signal, NanoBiT can detect protein interactions at low endogenous expression levels (2325). More recently, Nano-BiT technology has been used to develop immunoassays for detection of cell signaling pathways (26), SARS-CoV-2 Abs in patient serum and plasma (27,28), and small mycotoxin molecules in food (29). NanoBiT immunoassays were enabled by chemical labeling or making genetic fusion of detection reagents (Abs, proteins, and small molecules) and performing the assays in sandwich or competitive assay format.…”