Novel Competitive ELISA Utilizing Trimeric Spike Protein of SARS-CoV-2, Could Identify More Than RBD-RBM Specific Neutralizing Antibodies in Hybrid Sera
Petros Eliadis,
Annie Mais,
Alexandros Papazisis,
Eleni K. Loxa,
Alexios Dimitriadis,
Ioannis Sarrigeorgiou,
Marija Backovic,
Maria Agallou,
Marios Zouridakis,
Evdokia Karagouni,
Konstantinos Lazaridis,
Avgi Mamalaki,
Peggy Lymberi
Affiliations
Petros Eliadis
Immunology Laboratory, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Annie Mais
Laboratory of Molecular Biology and Immunobiotechnology, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Alexandros Papazisis
Immunology Laboratory, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Eleni K. Loxa
Immunology Laboratory, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Alexios Dimitriadis
Biotechnology Unit, Hellenic Pasteur Institute, 11521 Athens, Greece
Ioannis Sarrigeorgiou
Immunology Laboratory, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Marija Backovic
Institut Pasteur, Unité de Virologie Structurale, Université Paris Cité, CNRS-UMR3569, 75724 Paris, France
Maria Agallou
Immunology of Infection Laboratory, Microbiology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Marios Zouridakis
Structural Neurobiology Research Group, Laboratory of Molecular Neurobiology and Immunology, Department of Neurobiology, Hellenic Pasteur Institute, 11521 Athens, Greece
Evdokia Karagouni
Immunology of Infection Laboratory, Microbiology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Konstantinos Lazaridis
Immunology Laboratory, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Avgi Mamalaki
Biotechnology Unit, Hellenic Pasteur Institute, 11521 Athens, Greece
Peggy Lymberi
Immunology Laboratory, Immunology Department, Hellenic Pasteur Institute, 11521 Athens, Greece
Since the initiation of the COVID-19 pandemic, there has been a need for the development of diagnostic methods to determine the factors implicated in mounting an immune response against the virus. The most promising indicator has been suggested to be neutralizing antibodies (nAbs), which mainly block the interaction between the Spike protein (S) of SARS-CoV-2 and the host entry receptor ACE2. In this study, we aimed to develop and optimize conditions of a competitive ELISA to measure serum neutralizing titer, using a recombinant trimeric Spike protein modified to have six additional proline residues (S(6P)-HexaPro) and h-ACE2. The results of our surrogate Virus Neutralizing Assay (sVNA) were compared against the commercial sVNT (cPass, Nanjing GenScript Biotech Co., Nanjing City, China), using serially diluted sera from vaccinees, and a high correlation of ID50–90 titer values was observed between the two assays. Interestingly, when we tested and compared the neutralizing activity of sera from eleven fully vaccinated individuals who subsequently contracted COVID-19 (hybrid sera), we recorded a moderate correlation between the two assays, while higher sera neutralizing titers were measured with sVNA. Our data indicated that the sVNA, as a more biologically relevant model assay that paired the trimeric S(6P) with ACE2, instead of the isolated RBD-ACE2 pairing cPass test, could identify nAbs other than the RBD-RBM specific ones.
