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Martínez-Fleta P, Alfranca A, González-Álvaro I, Casasnovas JM, Fernández-Soto D, Esteso G, Cáceres-Martell Y, Gardeta S, López-Sanz C, Prat S, Mateu-Albero T, Gabrie L, López-Granados E, Sánchez-Madrid F, Reyburn HT, Rodríguez Frade JM, Valés-Gómez M. SARS-CoV-2 Cysteine-like Protease Antibodies Can Be Detected in Serum and Saliva of COVID-19-Seropositive Individuals. J Immunol 2020; 205:3130-3140. [PMID: 33148714 DOI: 10.4049/jimmunol.2000842] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 09/29/2020] [Indexed: 11/19/2022]
Abstract
Currently, there is a need for reliable tests that allow identification of individuals that have been infected with SARS-CoV-2 even if the infection was asymptomatic. To date, the vast majority of the serological tests for SARS-CoV-2-specific Abs are based on serum detection of Abs to either the viral spike glycoprotein (the major target for neutralizing Abs) or the viral nucleocapsid protein that is known to be highly immunogenic in other coronaviruses. Conceivably, exposure of Ags released from infected cells could stimulate Ab responses that might correlate with tissue damage and, hence, they may have some value as a prognostic indicator. We addressed whether other nonstructural viral proteins, not incorporated into the infectious viral particle, specifically the viral cysteine-like protease, might also be potent immunogens. Using ELISA tests, coating several SARS-CoV-2 proteins produced in vitro, we describe that COVID-19 patients make high titer IgG, IgM, and IgA Ab responses to the Cys-like protease from SARS-CoV-2, also known as 3CLpro or Mpro, and it can be used to identify individuals with positive serology against the coronavirus. Higher Ab titers in these assays associated with more-severe disease, and no cross-reactive Abs against prior betacoronavirus were found. Remarkably, IgG Abs specific for Mpro and other SARS-CoV-2 Ags can also be detected in saliva. In conclusion, Mpro is a potent Ag in infected patients that can be used in serological tests, and its detection in saliva could be the basis for a rapid, noninvasive test for COVID-19 seropositivity.
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Affiliation(s)
- Pedro Martínez-Fleta
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain
| | - Arantzazu Alfranca
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain.,Cardiovascular Centre for Biomedical Research Network, Health Institute Carlos III, Madrid 28029, Spain
| | - Isidoro González-Álvaro
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain.,Rheumatology Department, University Teaching Hospital "La Princesa," Madrid 28006, Spain
| | - Jose M Casasnovas
- Department of Macromolecular Structures, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain
| | - Daniel Fernández-Soto
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
| | - Gloria Esteso
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
| | - Yaiza Cáceres-Martell
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
| | - Sofía Gardeta
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
| | - Celia López-Sanz
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain
| | - Salomé Prat
- Department of Macromolecular Structures, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain
| | - Tamara Mateu-Albero
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain
| | - Ligia Gabrie
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain
| | | | - Francisco Sánchez-Madrid
- Immunology Department, University Teaching Hospital "La Princesa," La Princesa Health Research Institute, Madrid 28006, Spain.,Cardiovascular Centre for Biomedical Research Network, Health Institute Carlos III, Madrid 28029, Spain
| | - Hugh T Reyburn
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
| | - José M Rodríguez Frade
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
| | - Mar Valés-Gómez
- Department of Immunology and Oncology, National Centre for Biotechnology, National Centre for Biotechnology-Spanish National Research Council, Madrid 28049, Spain; and
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