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The quantitative range and reproducibility of current serological tests for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are not optimized. Herein, we developed a diagnostic test that detects SARS-CoV-2 IgG and IgM with high quantitativeness and reproducibility and low interference. The system was based on the high-sensitivity chemiluminescence enzyme immunoassay (HISCL) platform and detects IgG and IgM specific to SARS-CoV-2 spike and nucleocapsid proteins. Quantification accuracy and reproducibility were evaluated using serially diluted samples from 60 SARS-CoV-2-infected patients. Assay performance was evaluated using serum samples from the SARS-CoV-2-infected patients and 500 SARS-CoV-2-negative serum samples collected before the emergence of SARS-CoV-2. The system showed high quantification accuracy (range, 102), high reproducibility (within 5%), and no cross-reaction between SARS1- and MERS-S proteins. Detection accuracy was 98.3% and 93.3% for IgG and IgM against spike proteins and 100% and 71.7% for IgG and IgM against nucleocapsid proteins, respectively. Mean antibody levels were > 10 times that in negative samples upon admission and > 100 times that at convalescent periods. Clinical severity upon admission was not correlated with IgG or IgM levels. This highly quantitative, reproducible assay system with high clinical performance may help analyze temporal serological/immunological profiles of SARS-CoV-2 infection and SARS-CoV-2 vaccine effectiveness.

Background: Programmed cell death-1 (PD-1) and PD-ligand1 (PD-L1) inhibitors have become standard therapies for advanced non-small-cell lung cancer (NSCLC) due to prolonged patient survival. However, extended survival with anti-PD-1/PD-L1 therapy is limited to a small subset of NSCLC patients. Therefore, predictive biomarkers are needed to determine which patients will benefit. Recently, we reported that serum antibodies (Abs) against NY-ESO-1 and/or XAGE1 cancer-testis antigens are useful biomarkers that predict the clinical efficacy of anti-PD-1 monotherapy for NSCLC. The serum Abs were measured with enzyme-linked immunosorbent assay (ELISA); however, the ELISA method has several technical limitations for clinical applications. To overcome limitations in Ab measurement, we have developed a fully automated immunoassay system (HISCLTM) using chemiluminescent magnetic immunoassay technology. HISCLTM is widely used in many clinical fields because it is superior to ELISA due to its rapid reaction (17 minutes), wide dynamic ranges, and high reproducibility. Patients and Methods: Sera of NSCLC patients were obtained before anti-PD-1 monotherapy (nivolumab or pembrolizumab) as a part of standard care. NY-ESO-1/XAGE1 serum Abs were measured by ELISA and HISCLTM and their clinical performance was evaluated. In HISCLTM system, serum Abs were captured by magnetic beads coated with antigens, and the antigen-Ab complex was incubated with anti-human IgG conjugated with alkaline phosphatase. The chemiluminescent intensity acquired was then used for analyses. Results: Twenty-eight NSCLC patients were selected as the initial cohort for this study. Half of the patients responded to anti-PD-1 monotherapy and the remaining half did not. There were strong correlations between HISCLTM chemiluminescence signal intensity and titers of NY-ESO-1 and XAGE1 serum Abs in ELISA (r>0.93 for both). Twelve of thirteen Ab-positive patients in HISCLTM responded to anti-PD-1 therapy, while only two of fifteen Ab-negatives did (92% vs. 13%, p Conclusions: We have developed a rapid and highly reproducible immunoassay system for detecting the serum NY-ESO-1 and XAGE1 Abs as predictive biomarkers of clinical benefits with anti-PD-1 monotherapy in NSCLC. In the future, our system would be examined in large-scale clinical trials for various other cancers. Citation Format: Yumiko Sakai, Hirotaka Abo, Kanako Sakaeda, Yusuke Atarashi, Nobuyuki Ide, Takaaki Yamaoka, Koji Kurose, Kenta Noda, Toshiyuki Sato, Toru Oga, Mikio Oka. Development of a fully automated immunoassay system for detection of serum NY-ESO-1 and XAGE1 antibodies as biomarkers predicting the clinical efficacy of anti-PD-1 therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3180.