Limited specificity of commercially available SARS-CoV-2 IgG ELISAs in serum samples of African origin.

Specific serological tests are mandatory for reliable SARS-CoV-2 diagnostics and seroprevalence studies. Here, we assess the specificities of four commercially available SARS-CoV-2 IgG ELISAs in serum/plasma panels originating from Africa, South America, and Europe. 882 serum/plasma samples collected from symptom-free donors before the COVID-19 pandemic in three African countries (Ghana, Madagascar, Nigeria), Colombia, and Germany were analysed with three nucleocapsid-based ELISAs (Euroimmun Anti-SARS-CoV-2-NCP IgG, EDI™ Novel Coronavirus COVID-19 IgG, Mikrogen recomWell SARS-CoV-2 IgG), one spike/S1-based ELISA (Euroimmun Anti-SARS-CoV-2 IgG), and in-house common cold CoV ELISAs. High specificity was confirmed for all SARS-CoV-2 IgG ELISAs for Madagascan (93.4-99.4%), Colombian (97.8-100.0%), and German (95.9-100.0%) samples. In contrast, specificity was much lower for the Ghanaian and Nigerian serum panels (Ghana: NCP-based assays 77.7-89.7%, spike/S1-based assay 94.3%; Nigeria: NCP-based assays 39.3-82.7%, spike/S1-based assay 90.7%). 15 of 600 African sera were concordantly classified as positive in both the NCP-based and the spike/S1-based Euroimmun ELISA, but did not inhibit spike/ACE2 binding in a surrogate virus neutralisation test. IgG antibodies elicited by previous infections with common cold CoVs were found in all sample panels, including those from Madagascar, Colombia, and Germany and thus do not inevitably hamper assay specificity. Nevertheless, high levels of IgG antibodies interacting with OC43 NCP were found in all 15 SARS-CoV-2 NCP/spike/S1 ELISA positive sera. Depending on the chosen antigen and assay protocol, SARS-CoV-2 IgG ELISA specificity may be significantly reduced in certain populations probably due to interference of immune responses to endemic pathogens like other viruses or parasites.

Emmerich P ，Murawski C ，Ehmen C ，von Possel R ，Pekarek N ，Oestereich L ，Duraffour S ，Pahlmann M ，Struck N ，Eibach D ，Krumkamp R ，Amuasi J ，Maiga-Ascofaré O ，Rakotozandrindrainy R ，Asogun D ，Ighodalo Y ，Kann S ，May J ，Tannich E ，Deschermeier C ... -  《-》

Validation of Commercial SARS-CoV-2 Immunoassays in a Nigerian Population.

Ige F ，Hamada Y ，Steinhardt L ，Iriemenam NC ，Uwandu M ，Greby SM ，Aniedobe M ，Salako BL ，Rangaka MX ，Abubakar I ，Audu R ... -  《Microbiology Spectrum》

Evaluation of a SARS-CoV-2 Capture IgM Antibody Assay in Convalescent Sera.

Ha B ，Jadhao S ，Hussaini L ，Gibson T ，Stephens K ，Salazar L ，Ciric C ，Taylor M ，Rouphael N ，Edupuganti S ，Rostad CA ，Tompkins SM ，Anderson EJ ，Anderson LJ ... -  《Microbiology Spectrum》

SARS-CoV-2 Antibody Testing in Health Care Workers: A Comparison of the Clinical Performance of Three Commercially Available Antibody Assays.

Allen N ，Brady M ，Carrion Martin AI ，Domegan L ，Walsh C ，Houlihan E ，Kerr C ，Doherty L ，King J ，Doheny M ，Griffin D ，Molloy M ，Dunne J ，Crowley V ，Holmes P ，Keogh E ，Naughton S ，Kelly M ，O'Rourke F ，Lynagh Y ，Crowley B ，de Gascun C ，Holder P ，Bergin C ，Fleming C ，Ni Riain U ，Conlon N ，PRECISE Study Steering Group ... -  《Microbiology Spectrum》

Evaluation of a multiplexed coronavirus antigen array for detection of SARS-CoV-2 specific IgG in COVID-19 convalescent plasma.

Mitigation of the COVID-19 pandemic requires an understanding of the antibody response to SARS-CoV-2. However, throughout the development of SARS-CoV-2 IgG antibody assays during the past year, cross-reactivity to other coronaviruses remained a question. To address these issues, we evaluated IgG in COVID-19 convalescent plasma samples for reactivity against three SARS-CoV-2 antigens including full-length spike, receptor binding domain, and the proximal extracellular fusion domain, and spike antigens from other coronaviruses (SARS-CoV, MERS-CoV, hCoV-HKU1, hCoV-OC43, hCoV-229E and hCoV-NL63) using the VaxArray Coronavirus SeroAssay which is a multiplexed antigen assay developed by InDevR Inc. These results were compared to two commercial SARS-CoV-2 IgG ELISAs targeting either the SARS-CoV-2 nucleocapsid or spike antigens and a live virus focus reduction neutralizing antibody test (FRNT). The VaxArray platform showed high specificity for detection of SARS-CoV-2 IgG, evident from lack of reactivity to SARS-CoV-2 antigens despite significant reactivity to endemic coronavirus antigens in pre-pandemic samples. SARS-CoV-2 IgG positive samples reacted weakly to SARS-CoV spike but not to MERS-CoV. While the VaxArray platform had overall comparable results to the spike and nucleocapsid IgG ELISAs, results were more similar to the spike antigen ELISA and the platform displayed a higher sensitivity and specificity than both ELISAs. Samples with FRNT titers below 1/23 reported negative on VaxArray, while positive samples on VaxArray had significantly higher neutralizing antibody titers. These results suggest that the VaxArray Coronavirus SeroAssay performs with high sensitivity and specificity for the detection of SARS-CoV-2 IgG, and positive results on the platform indicate SARS-CoV-2 neutralizing activity.

Huey L ，Andersen G ，Merkel PA ，Morrison TE ，McCarthy M ，DomBourian MG ，Annen K ，Dawson ED ，Rowlen KL ，Knight V ... -  《-》