Patterns and persistence of SARS-CoV-2 IgG antibodies in Chicago to monitor COVID-19 exposure
Alexis R. Demonbreun, … , Brian Mustanski, Elizabeth M. McNally
Alexis R. Demonbreun, … , Brian Mustanski, Elizabeth M. McNally
Published March 23, 2021
Citation Information: JCI Insight. 2021;6(9):e146148. https://doi.org/10.1172/jci.insight.146148.
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Clinical Research and Public Health COVID-19

Patterns and persistence of SARS-CoV-2 IgG antibodies in Chicago to monitor COVID-19 exposure

Abstract

BACKGROUND Estimates of seroprevalence to SARS-CoV-2 vary widely and may influence vaccination response. We ascertained IgG levels across a single US metropolitan site, Chicago, from June 2020 through December 2020.METHODS Participants (n = 7935) were recruited through electronic advertising and received materials for a self-sampled dried-blood spot assay through the mail or a minimal contact in-person method. IgG against the receptor-binding domain of SARS-CoV-2 was measured using an established highly sensitive and highly specific assay.RESULTS Overall seroprevalence was 17.9%, with no significant difference between method of contact. Only 2.5% of participants reported having had a diagnosis of COVID-19 based on virus detection, consistent with a 7-fold greater exposure to SARS-CoV-2 measured by serology than that detected by viral testing. The range of IgG level observed in seropositive participants from this community survey overlapped with the range of IgG levels associated with COVID-19 cases having a documented positive PCR test. From a subset of those who participated in repeat testing, half of seropositive individuals retained detectable antibodies for 3 to 4 months.CONCLUSION Quantitative IgG measurements with a highly specific and sensitive assay indicated more widespread exposure to SARS-CoV-2 than observed by viral testing. The range of IgG concentrations produced from these asymptomatic exposures was similar to IgG levels occurring after documented nonhospitalized COVID-19, which were considerably lower than those produced from hospitalized COVID-19 cases. The differing ranges of IgG response, coupled with the rate of decay of antibodies, may influence response to subsequent viral exposure and vaccine.Funding National Science Foundation grant 2035114, NIH grant 3UL1TR001422-06S4, NIH National Center for Advancing Translational Sciences grants UL1 TR001422 and UL1 TR002389, Dixon Family Foundation, Northwestern University Cancer Center (NIH grant P30 CA060553), and Walder Foundation’s Chicago Coronavirus Assessment Network.

Authors

Alexis R. Demonbreun, Thomas W. McDade, Lorenzo Pesce, Lauren A. Vaught, Nina L. Reiser, Elena Bogdanovic, Matthew P. Velez, Ryan R. Hsieh, Lacy M. Simons, Rana Saber, Daniel T. Ryan, Michael G. Ison, Judd F. Hultquist, John T. Wilkins, Richard T. D’Aquila, Brian Mustanski, Elizabeth M. McNally

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Figure 2

Quantitative measure of IgG directed to the receptor-binding domain of SARS-CoV-2 spike glycoprotein.

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Quantitative measure of IgG directed to the receptor-binding domain of S...
Samples were acquired through Screening for Coronavirus Antibodies in Neighborhood (SCAN) between June 2020 and December 2020 (n = 7935). (A) Samples acquired before 2019 constituted the negative, pre-COVID group (leftmost column; black dots; median, 0.09 μg/ml), and the mean IgG was similar to that in the SCAN seronegative group (second column; gray dots; median, 0.09 μg/ml). The median IgG range in SCAN seropositive samples (middle column; light purple) was 0.75 μg/ml. The median IgG range in outpatient, nonhospitalized COVID-19 samples (4th column, dark purple) was 5.2 μg/ml. The range between SCAN seropositive and outpatient COVID-19 samples showed significant overlap. Both SCAN seropositive and outpatient COVID-19 cases had much lower IgG levels than ICU-hospitalized COVID-19 cases (rightmost column, dark blue, median 98.5 μg/ml). The SARS-CoV-2 receptor-binding domain (RBD) IgG ELISA seropositive threshold is marked by the red line at 0.39 μg/ml, as validated previously (16). *P < 0.0001, comparing seropositive groups, by Wilcoxon-Mann-Whitney test. Both true negatives and the SCAN seronegative groups were significantly different compared with all seropositive groups. (B) 17.95% (1424 of 7935) of SCAN samples were seropositive. (C) 2.46% (195 of 7935) reported having a positive SARS-CoV-2 viral diagnostic test.