key: cord-340291-bah2ege0
authors: Kohmer, Niko; Westhaus, Sandra; Rühl, Cornelia; Ciesek, Sandra; Rabenau, Holger F.
title: Clinical performance of SARS-CoV-2 IgG antibody tests and potential protective immunity
date: 2020-05-10
journal: bioRxiv
DOI: 10.1101/2020.05.08.085506
sha: 
doc_id: 340291
cord_uid: bah2ege0

As the current SARS-CoV-2 pandemic continues, serological assays are urgently needed for rapid diagnosis, contact tracing and for epidemiological studies. So far, there is little data on how commercially available tests perform with real patient samples and if detected IgG antibodies provide protective immunity. Focusing on IgG antibodies, we demonstrate the performance of two ELISA assays (Euroimmun SARS-CoV-2 IgG & Vircell COVID-19 ELISA IgG) in comparison to one lateral flow assay ((LFA) FaStep COVID-19 IgG/IgM Rapid Test Device) and two in-house developed assays (immunofluorescence assay (IFA) and plaque reduction neutralization test (PRNT)). We tested follow up serum/plasma samples of individuals PCR-diagnosed with COVID-19. Most of the SARS-CoV-2 samples were from individuals with moderate to severe clinical course, who required an in-patient hospital stay. For all examined assays, the sensitivity ranged from 58.8 to 76.5% for the early phase of infection (days 5-9) and from 93.8 to 100% for the later period (days 10-18) after PCR-diagnosed with COVID-19. With exception of one sample, all positive tested samples in the analysed cohort, using the commercially available assays examined (including the in-house developed IFA), demonstrated neutralizing (protective) properties in the PRNT, indicating a potential protective immunity to SARS-CoV-2. Regarding specificity, there was evidence that samples of endemic coronavirus (HCoV-OC43, HCoV-229E) and Epstein Barr virus (EBV) infected individuals cross-reacted in the ELISA assays and IFA, in one case generating a false positive result (may giving a false sense of security). This need to be further investigated.

As the current SARS-CoV-2 pandemic continues, serological assays are urgently needed for rapid 25 diagnosis, contact tracing and for epidemiological studies. So far, there is little data on how 26 commercially available tests perform with real patient samples and if detected IgG antibodies 27 provide protective immunity. Focusing on IgG antibodies, we demonstrate the performance of two 28 ELISA assays (Euroimmun SARS-CoV-2 IgG & Vircell COVID-19 ELISA IgG) in comparison to one lateral 29 flow assay ((LFA) FaStep COVID-19 IgG/IgM Rapid Test Device) and two in-house developed assays 30 (immunofluorescence assay (IFA) and plaque reduction neutralization test (PRNT)). We tested follow 31 up serum/plasma samples of individuals PCR-diagnosed with COVID-19. Most of the SARS-CoV-2 32 samples were from individuals with moderate to severe clinical course, who required an in-patient 33 hospital stay. 34

For all examined assays, the sensitivity ranged from 58.8 to 76.5% for the early phase of infection 35 (days 5-9) and from 93.8 to 100% for the later period (days 10-18) after PCR-diagnosed with COVID-36 19. With exception of one sample, all positive tested samples in the analysed cohort, using the 37 commercially available assays examined (including the in-house developed IFA), demonstrated 38 neutralizing (protective) properties in the PRNT, indicating a potential protective immunity to SARS-39 there is an increasing demand in the detection of antibodies -especially of IgG antibodies. 53 Convalescent plasma may be used for therapeutic or prophylactic approaches as vaccines and other 54 drugs are under development (2). For all these purposes, sensitive and especially highly specific 55 antibody assays are needed. The spike (S) protein of SARS-CoV-2 has shown to be highly 56 immunogenic and is the main target for neutralizing antibodies (3). Currently there are many S 57 protein based commercially or in-house developed assays available, but there is limited data on how 58 these tests perform with clinical samples and if the detected IgG antibodies provide protective 59

immunity. This study aims to provide a quick overview on some of these assays (two commercial 60 available ELISA, an LFA, an IFA and a PRNT, focusing on the detection and neutralization capacity of In terms of sensitivity, our data are consistent with previously published data. In a study from Liu et 154 al., using an rS-based ELISA assay, the group found SARS-CoV-2 IgG antibodies in less than 60% of the 155 samples from days 6-10 after disease onset. The sensitivity increased to >90% in samples from days [especially for potential protective IgG antibodies against the S protein (6)] using ELISA or lateral flow 164 assays is more convenient and practicable than using the hands on-and time-intensive IFA or PRNT, 165 which can only be performed by experienced personnel, and the PRNT, only in a BSL-3 laboratory. 166 ELISA based assays can be automated and used for larger sample sizes. Lateral flow assays can be 167 used by less experienced personnel in a point-of-care setting, generating results in short time. Some 168 samples, however, were only detected with the IFA and PRNT as gold standard. The titer needed for 169 potential protective immunity is not yet (officially) defined. In one study, it is reported, that a 170 individual cleared SARS-CoV-2 without developing antibodies up to 46 days after illness (7). The 171 mechanism of immunity, especially of protective immunity (if applicable) and how long it will last, 172 need to be further investigated. Besides humoral mediated immunity, there is evidence that T-cell 173 

SARS-CoV-2 and 197 Coronavirus Disease 2019: What We Know So Far

Convalescent plasma transfusion for the treatment of COVID-19: Systematic review

Characterization of spike glycoprotein of SARS-CoV-2 on virus 204 entry and its immune cross-reactivity with SARS-CoV

207 Evaluation of Nucleocapsid and Spike Protein-based ELISAs for detecting antibodies against 208 SARS-CoV-2

Virological assessment of hospitalized patients with COVID-2019. 212 Nature

Perspectives on therapeutic neutralizing antibodies against the Novel 214

Long-term 216 Coexistence of SARS-CoV-2 with Antibody Response in COVID-19 Patients

The trinity of COVID-19: immunity, 219 inflammation and intervention

Severe Acute 223 Respiratory Syndrome Coronavirus 2-Specific Antibody Responses in Coronavirus Disease 2019 224 Patients