Ultra-Sensitive Serial Profiling of SARS-CoV-2 Antigens and Antibodies in Plasma to Understand Disease Progression in COVID-19 Patients with Severe Disease

Abstract

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected over 21 million people worldwide since August 16, 2020. Compared to PCR and serology tests, SARS-CoV-2 antigen assays are underdeveloped, despite their potential to identify active infection and monitor disease progression. Methods We used Single Molecule Array (Simoa) assays to quantitatively detect SARS-CoV-2 spike, S1 subunit, and nucleocapsid antigens in the plasma of coronavirus disease (COVID-19) patients. We studied plasma from 64 COVID-19 positive patients, 17 COVID-19 negative patients, and 34 pre-pandemic patients. Combined with Simoa anti-SARS-CoV-2 serological assays, we quantified changes in 31 SARS-CoV-2 biomarkers in 272 longitudinal plasma samples obtained for 39 COVID-19 patients. Data were analyzed by hierarchical clustering and were compared to longitudinal RT-PCR test results and clinical outcomes. Results SARS-CoV-2 S1 and N antigens were detectable in 41 out of 64 COVID-19 positive patients. In these patients, full antigen clearance in plasma was observed a mean ± 95%CI of 5 ± 1 days after seroconversion and nasopharyngeal RT-PCR tests reported positive results for 15 ± 5 days after viral antigen clearance. Correlation between patients with high concentrations of S1 antigen and ICU admission (77%) and time to intubation (within one day) was statistically significant. Conclusions The reported SARS-CoV-2 Simoa antigen assay is the first to detect viral antigens in the plasma of COVID-19 positive patients to date. These data show that SARS-CoV-2 viral antigens in the blood are associated with disease progression, such as respiratory failure, in COVID-19 cases with severe disease.

In-depth blood proteome profiling analysis revealed distinct functional characteristics of plasma proteins between severe and non-severe COVID-19 patients

“…Although we could not directly compare our results with this study due to a difference in comparison group, both studies highlight the immune response led by neutrophils in COVID-19 patients. The other study, performed by Ogata et al, used the Simoa™ assay to measure viral antigens and antibodies in plasma 31 . In this study, antibody-coated beads were used to detect and quantify viral fragments in the blood of COVID-19 patients, suggesting possibility of using this assay for diagnosis.…”

COVID-19 Antibody Tests and Their Limitations

“…However, it requires a specialized instrument (HD-X Analyzer (Quanterix)) that is quite expensive. 240 Simultaneous IgG/IgM/unreported antigen detection of SARS-CoV-2 was achieved on an integrated microfluidic fluorescence immunoassay system. 78 Another group quantified SARS-CoV-2 N protein, IgG, IgM, and C-reactive protein in serum and saliva using a multiplexed electrochemical graphene-based platform called SARS-CoV-2 RapidPlex.…”

Head-to-Head Comparison of Rapid and Automated Antigen Detection Tests for the Diagnosis of SARS-CoV-2 Infection

“…Head-to-head comparisons of AD test performance for SARS-CoV-2 detection are scarce. The majority of the studies only included few patients, precluding a wide characterization of the “real-life” performance of these devices [ 3 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Recently, a Cochrane study found an average sensitivity of only 56.2% (95% confidence interval (CI): 29.5–79.8%) for rapid AD (RAD) tests [ 11 ].…”

“…Recently, a Cochrane study found an average sensitivity of only 56.2% (95% confidence interval (CI): 29.5–79.8%) for rapid AD (RAD) tests [ 11 ]. Independent reporting of automated AD test performance remains limited [ 18 ].…”