Characterization of an attenuated SARS-CoV-2 variant with a deletion at the S1/S2 junction of the spike protein
Pui Wang, S. Lau, Shaofeng Deng, Pin Chen, Bobo Wing-Yee Mok, Jinxia Zhang, Andrew Chak-Yiu Lee, Kwok‐Hung Chan, Rachel Chun-Yee Tam, Haoran Xu, Runhong Zhou, Wenjun Song, Li Liu, Kelvin Kai‐Wang To, Jasper Fuk‐Woo Chan, Zhiwei Chen, Kwok‐Yung Yuen, Honglin Chen
Abstract
SARS-CoV-2 is of zoonotic origin and contains a PRRA polybasic cleavage motif which is considered critical for efficient infection and transmission in humans. We previously reported on a panel of attenuated SARS-CoV-2 variants with deletions at the S1/S2 junction of the spike protein. Here, we characterize pathogenicity, immunogenicity, and protective ability of a further cell-adapted SARS-CoV-2 variant, Ca-DelMut, in in vitro and in vivo systems. Ca-DelMut replicates more efficiently than wild type or parental virus in Vero E6 cells, but causes no apparent disease in hamsters, despite replicating in respiratory tissues. Unlike wild type virus, Ca-DelMut causes no obvious pathological changes and does not induce elevation of proinflammatory cytokines, but still triggers a strong neutralizing antibody and T cell response in hamsters and mice. Ca-DelMut immunized hamsters challenged with wild type SARS-CoV-2 are fully protected, with little sign of virus replication in the upper or lower respiratory tract, demonstrating sterilizing immunity.