Evaluation of a Rapid and Automated Surrogate Virus Neutralization Test in Comparison to a Pseudovirus and Live Virus Neutralization Assay

Abstract

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease (COVID-19) has resulted in roughly 500 million confirmed cases of COVID-19 including an estimated 6 million deaths world-wide, as of April 2022. Vaccines were developed and administered limiting the extent of the pandemic, but with the rise of emerging variants, studies to better understand immune protection against COVID-19 have become a high priority. Neutralizing antibodies represent an important correlate of protection for COVID-19. The cell-based neutralization assays that detect and quantify neutralizing antibody titers use either live virus or pseudotyped viral particles (pseudovirus). Live virus cell-based assays are time consuming and require the use of live SARS-CoV-2 but can be substituted with pseudovirus to avoid requirements for biosafety level (BSL)-3 facilities. This has motivated the development of surrogate SARS-CoV-2 neutralization assays that measure inhibition of the spike (S) protein receptor binding domain (RBD) binding its receptor, human angiotensin converting enzyme 2 (hACE2). The current surrogate virus neutralization tests (sVNTs) are ELISA-based, requiring considerable involvement by laboratory personnel for the multiple washes, incubation steps, and reagent additions as well as a plate reader to generate results. The development of a sVNT performed on an automated and rapid platform could be instrumental in furthering the research and clinical assessment of immune protection against COVID-19. Here we developed and evaluated a sVNT performed on the Simple PlexTM rapid and automated immunoassay platform. The test achieves 100% sensitivity and 99-100% specificity and shows a strong correlation with cell-based assays. This rapid and automated sVNT provides a faster and more easily completed assay for determining SARS-CoV-2 neutralizing antibody titers that can be performed in a BSL-2 laboratory.