RES EARCH
CORONAVIRUS
Robust neutralizing antibodies to SARS-CoV-2 infection persist for months Ania Wajnberg1*, Fatima Amanat2,3, Adolfo Firpo4, Deena R. Altman5, Mark J. Bailey1, Mayce Mansour1, Meagan McMahon2, Philip Meade2,3, Damodara Rao Mendu4, Kimberly Muellers1, Daniel Stadlbauer2, Kimberly Stone1, Shirin Strohmeier2, Viviana Simon2, Judith Aberg5, David L. Reich6, Florian Krammer2*, Carlos Cordon-Cardo4* Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic with millions infected and more than 1 million fatalities. Questions regarding the robustness, functionality, and longevity of the antibody response to the virus remain unanswered. Here, on the basis of a dataset of 30,082 individuals screened at Mount Sinai Health System in New York City, we report that the vast majority of infected individuals with mild-to-moderate COVID-19 experience robust immunoglobulin G antibody responses against the viral spike protein. We also show that titers are relatively stable for at least a period of about 5 months and that anti-spike binding titers significantly correlate with neutralization of authentic SARS-CoV-2. Our data suggest that more than 90% of seroconverters make detectable neutralizing antibody responses. These titers remain relatively stable for several months after infection.
1
Department of General Internal Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. 3Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. 4Clinical Microbiology Laboratory, Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. 5 Division of Infectious Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. 6Department of Anesthesiology, Perioperative and Pain Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. 2
*Corresponding author. Email: ania.wajnberg@mountsinai.org (A.W.); florian.krammer@mssm.edu (F.K.); carlos. cordon-cardo@mssm.edu (C.C.-C.)
Wajnberg et al., Science 370, 1227–1230 (2020)
for characterizing the immune response to SARS-CoV-2 is the spike protein. The spike is a large trimeric glycoprotein that contains the receptor binding domain, which the virus uses to dock to its cellular receptor, angiotensinconverting enzyme 2, and for fusion of viral and cellular membranes (4, 5). It is known from other coronaviruses—and it holds true for SARS-CoV-2—that the spike is the main, and potentially the only, target for neutralizing antibodies (6). Therefore, the assay used in this study to characterize the antibody response to SARS-CoV-2 is based on the trimerized, stabilized ectodomain of the spike protein (7). An enzyme-linked immunosorbent assay (ELISA) initially developed in early 2020 has been extensively used in research (7–10). This so-called Mount Sinai ELISA has high sensitivity (92.5%) and specificity (100%), as determined with an initial validation panel of samples (table S1). Furthermore, it has a positive predictive value (PPV) of 100%, with a negative predictive value (NPV) of 99.6%. In March 2020, the Mount Sinai Health System began screening individuals for antibodies to SARS-CoV-2 to recruit volunteers as donors for convalescent plasma therapy (11). Screened patients had either polymerase chain reaction (PCR)–confirmed SARS-CoV-2 infections or suspected disease, which is defined as being told by a physician that symptoms may be related to SARS-CoV-2 or exposure to someone with confirmed SARS-CoV-2 infection. Most of the symptomatic patients who were screened experienced mild-to-moderate disease, with <5% requiring emergency department evaluation or hospitalization. Mount Sinai also offered the antibody test to all employees in its health system on a voluntary basis. By 6 October 2020, Mount Sinai had screened 72,401 individuals, with a total
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evere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected millions of individuals globally and, as of October 2020, has led to the death of >1 million individuals. Although the antibody responses in severe COVID-19 cases have been relatively well characterized (1, 2), assessing the response in mild and asymptomatic cases is of great importance because they constitute most infections. It will be critical to understand the robustness of the antibody response in these mild cases, including its longevity and functionality, so as to inform serosurveys and to determine levels and duration of antibody titers that may be protective against reinfection (3). Antibodies to SARS-CoV-2 can target many of its encoded proteins, including structural and nonstructural antigens. Thus far, two structural proteins have been used as target antigens for serological assays. One is the abundant nucleoprotein (NP), which is found inside the virus or inside infected cells. However, because of the biological function of NP and because it is shielded from antibodies by viral or cellular membranes, it is unlikely that NP antibodies can directly neutralize SARS-CoV-2. The second structural protein often used as a target
of 30,082 individuals testing positive (defined as detectable antibodies to the spike protein at a titer of 1:80 or higher) and 42,319 testing negative. The clinical laboratory ELISA set up results in discrete titers of either 1:80, 1:160, 1:320, 1:960, or ≥1:2880. Titers of 1:80 and 1:160 were categorized as low titers, 1:320 as moderate, and 1:960 and ≥1:2880 as high titers. For plasma therapy, titers of 1:320 or higher were initially deemed eligible. Of the 30,082 positive samples, 690 (2.29%) had a titer of 1:80; 1453 (4.83%), 1:160; 6765 (22.49%), 1:320; 9564 (31.79%), 1:960; and 11,610 (38.60%), ≥1:2880 (Fig. 1). Thus, we conclude that the vast majority of positive individuals have moderateto-high titers of anti-spike antibodies. Of course, the argument could be made that we could be missing a number of individuals who had been infected with SARS-CoV-2 and did not produce antibodies, given that many individuals included in our dataset had never been tested by a nucleic acid amplification test for the virus. An earlier analysis performed with a smaller subset of 568 PCR-confirmed individuals using the same ELISA showed that >99% developed an anti-spike antibody response (8). In a later dataset of 2347 patients who self-reported positive PCR, 95% had positive antibody titers, which indicates that we did not miss large numbers of patients and confirms our prior sensitivity findings. Thus, the rate of individuals who do not seroconvert after SARS-CoV-2 infection is low, although such individuals may exist, and the majority of responders mount titers of 1:320 or higher. Determining the neutralizing effects of SARSCoV-2 spike antibodies is critical to understanding possible protective effects of the immune response. Therefore, we performed a wellestablished quantitative microneutralization assay (12) based on authentic SARS-CoV-2 with 120 samples of known ELISA titers ranging from negative to ≥1:2880. Neutralization titers significantly correlated (Spearman r = 0.87, P < 0.0001) with spike-binding titers (Fig. 2A). Although there was some variability, sera with 1:320, 1:960, and ≥1:2880 ELISA titers had geometric mean 50% inhibitory dilutions (ID50) of about 1:30, 1:75, and 1:550, respectively. If any and all neutralizing activity above background is considered, then ~50% of sera in the 1:80 to 1:160 titer range, 90% in the 1:320 range, and all sera in the 1:960 to ≥1:2880 range had neutralizing activity (Fig. 2B). Only one of the negative samples showed activity slightly above background, which was potentially an ELISA false negative. Another important question is longevity of the antibody response to the spike. To assess the medium-range stability of serum antibody titers against the spike protein, we recalled 121 plasma donors at a variety of titer levels who had initially been screened at around day 30