Surrogate Virus Neutralisation Test Based on Nanoluciferase-Tagged Antigens to Quantify Inhibitory Antibodies against SARS-CoV-2 and Characterise Omicron-Specific Reactivity in a Vaccination Cohort
Michael Schoefbaenker,
Rieke Neddermeyer,
Theresa Guenther,
Marlin M. Mueller,
Marie-Luise Romberg,
Nica Classen,
Marc T. Hennies,
Eike R. Hrincius,
Stephan Ludwig,
Joachim E. Kuehn,
Eva U. Lorentzen
Affiliations
Michael Schoefbaenker
Institute of Virology, Department of Molecular Virology, University of Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
Rieke Neddermeyer
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Theresa Guenther
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Marlin M. Mueller
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Marie-Luise Romberg
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Nica Classen
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Marc T. Hennies
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Eike R. Hrincius
Institute of Virology, Department of Molecular Virology, University of Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
Stephan Ludwig
Institute of Virology, Department of Molecular Virology, University of Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
Joachim E. Kuehn
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Eva U. Lorentzen
Institute of Virology, Department of Clinical Virology, University of Muenster, Von-Stauffenberg-Str. 36, D-48151 Muenster, Germany
Virus-specific antibodies are crucial for protective immunity against SARS-CoV-2. Assessing functional antibodies through conventional or pseudotyped virus neutralisation tests (pVNT) requires high biosafety levels. Alternatively, the virus-free surrogate virus neutralisation test (sVNT) quantifies antibodies interfering with spike binding to angiotensin-converting enzyme 2. We evaluated secreted nanoluciferase-tagged spike protein fragments as diagnostic antigens in the sVNT in a vaccination cohort. Initially, spike fragments were tested in a capture enzyme immunoassay (EIA), identifying the receptor binding domain (RBD) as the optimal diagnostic antigen. The sensitivity of the in-house sVNT applying the nanoluciferase-labelled RBD equalled or surpassed that of a commercial sVNT (cPass, GenScript Diagnostics) and an in-house pVNT four weeks after the first vaccination (98% vs. 94% and 72%, respectively), reaching 100% in all assays four weeks after the second and third vaccinations. When testing serum reactivity with Omicron BA.1 spike, the sVNT and pVNT displayed superior discrimination between wild-type- and variant-specific serum reactivity compared to a capture EIA. This was most pronounced after the first and second vaccinations, with the third vaccination resulting in robust, cross-reactive BA.1 construct detection. In conclusion, utilising nanoluciferase-labelled antigens permits the quantification of SARS-CoV-2-specific inhibitory antibodies. Designed as flexible modular systems, the assays can be readily adjusted for monitoring vaccine efficacy.
