SARS-CoV-2 Spike Pseudoviruses: A Useful tool to study virus entry and address emerging neutralization escape phenotypes

Kalkeri, Raj; Cai, Zhaohui; Lin, Shuling; Farmer, John; Kuzmichev, Yury V.; Koide, Fusataka

SARS-CoV-2 genetic variants are emerging around the globe. Unfortunately, several SARS-CoV-2 variants, especially, variants of concern (VOC) are less susceptible to neutralization by the convalescent and post-vaccination sera, raising concerns of increased disease transmissibility and severity. Recent data suggests the SARS-CoV-2 neutralizing anti-body levels as a good correlate of vaccine mediated protection. However, currently used BSL3 based virus micro-neutralization (MN) assays are more laborious, time consuming and expensive, underscoring the need for BSL2 based, cost effective neutralization assays against SARS-CoV-2 variants. In light of this unmet need, we have developed a BSL2 pseudovirus based neutralization assay (PBNA) in cells expressing Angiotensin Converting Enzyme-2 (ACE2) receptor for SARS-CoV-2. The assay is reproducible (R2=0.96), demonstrates a good dynamic range and high sensitivity. Our data suggests that the biological Anti-SARS-CoV-2 research reagents such as NIBSC 20/130 show lower neutralization against B.1.351 RSA and B1.1.7 UK VOC, whereas a commercially available monoclonal antibody MM43 retains activity against both these variants. SARS-CoV-2 Spike Pseudovirus based neutralization assays for VOC would be useful tools to measure the neutralization ability of candidate vaccines in both preclinical models and clinical trials and further help develop effective prophylactic countermeasures against emerging neutralization escape phenotypes.