![]() ![]() Current tests that have been developed include the Lateral Flow Immunoassay (LFIA), Enzyme-Linked Immunosorbent Assay (ELISA), Immunofluorescent Assay (IFA), and Chemiluminescent Immunoassay (CLIA). Serological tests are also distinguished on whether they detect total antibodies, IgG, IgM, or both IgG and IgM. Methods that utilize the spike, and the RBD in particular, have been shown to correlate with SARS-CoV-2 neutralization assays 7, 8, 10, 12, 13, 14, 15, 16. Serological testing methods for SARS-CoV-2 predominantly use the virus nucleocapsid protein, the spike glycoprotein, or fragments thereof such as the spike receptor binding domain (RBD), to probe for antibodies. Accurate serological testing is crucial to develop countermeasures against SARS-CoV-2 infection, including the identification and evaluation of donors for convalescent plasma therapy and the development of a SARS-CoV-2 vaccine. Serological studies have shown that antibodies develop over several weeks following infection with SARS-CoV-2, and that antibody levels can vary significantly between individuals 8, 9, 10, 11. Thus, serological testing, which detects antibodies elicited by SARS-CoV-2 antigens, have become key to assessing the true extent of SARS-CoV-2 spread within the population 7. However, due to limitations in nucleic acid testing availability and the occurrence of mild or asymptomatic infections, many cases of COVID-19 are not diagnosed. Nucleic acid testing methods were quickly developed after the release of the virus genome 4, 5, 6 and serve as the primary, definitive diagnostic tool for active cases of COVID-19. Efficient and accurate testing is critical to understand the full breadth of impact and to developing countermeasures to limit future infections.ĭetection of SARS-CoV-2 infection relies predominantly on two approaches: nucleic acid testing, which detects viral RNA, and serological testing, which detects antibodies elicited against SARS-CoV2 antigens. As of November 10, 2020, over 51 million cases and over 1.2 million deaths have been reported due to COVID-19, and the disease continues to be a source of economic and societal strain. Officially named severe acute respiratory coronavirus 2 (SARS-CoV-2) by the International Committee on Taxonomy of Viruses due to its phylogenetic relatedness to SARS and SARS-like coronaviruses 3, the virus causes coronavirus disease 2019 (COVID-19). In the ensuing months the virus became established internationally through travel and community transmission, leading to the declaration of a pandemic by the WHO on Ma2. In December 2019, a novel coronavirus emerged in Wuhan, China, causing severe respiratory disease with initial reported fatality rates of 2–3% 1. In a broader sense, BLI-ISA can be developed as a novel diagnostic platform to evaluate antibodies and other biomolecules in clinical specimens. Importantly, our method can be immediately implemented on existing BLI platforms for urgent COVID-19 studies, such as serosurveillance and the evaluation of vaccine candidates. BLI-ISA meets or exceeds the performance of high complexity methods such as Enzyme-Linked Immunosorbent Assay (ELISA) and Chemiluminescent Immunoassay. Complete semi-quantitative results are obtained in less than 20 min. Our biolayer interferometry immunosorbent assay (BLI-ISA) utilizes single-use biosensors in an automated “dip-and-read” format, providing real-time optical measurements of antigen loading, plasma antibody binding, and antibody isotype detection. Here, we describe a novel application of biolayer interferometry for the rapid detection of antigen-specific antibody levels in plasma samples, and demonstrate its utility for quantification of SARS-CoV-2 antibodies. ![]() Serological testing to evaluate antigen-specific antibodies in plasma is generally performed by rapid lateral flow test strips that lack quantitative results or by high complexity immunoassays that are time- and labor-intensive but provide semi-quantitative results. ![]()
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