Poster abstracts
Poster number 3 submitted by Julia Faraone
SARS-CoV-2 spike mutation I692V drives destabilization of spike and attenuates viral infectivity
Julia N Faraone (Molecular, Cellular, and Developmental Biology Program, The Ohio State University), John Evans (Veterinary Biosciences, The Ohio State University), Kai Xu (Veterinary Biosciences, The Ohio State University), Shan-Lu Liu (Veterinary Biosciences, The Ohio State University)
Abstract:
Abstract (300 word limit) Throughout the COVID-19 pandemic, SARS-CoV-2 has demonstrated the ability to infect a variety of animal hosts. Some of these infections, particularly in farmed mink, have resulted in new variants of the virus. One such variant, called mink cluster five variant (MC5V), carries five mutations in the spike protein including I692V and M1229I in the S2 subunit. While MC5V has been reported to have reduced pathogenicity in humans compared to the ancestral Wuhan strain, the underlying mechanism is unclear. Here we conducted mutational analyses of ancestral and MC5V spike proteins and characterized the impacts of these key residues. We identified the I692V mutation, located near the furin cleavage site, as the key determinant of the low infectivity of MC5V. Specifically, we observed that introduction of I692V into D614G reduces the spike furin processing, impairs spike-mediated cell-cell fusion, and diminishes pseudotyped lentivirus infectivity. Consistently, introducing the V692I reversion mutation into MC5V greatly restored MC5V spike processing and fusogenicity and increased pseudotyped virus infectivity to levels comparable with D614G. Additionally, we have found that I692V mutation promotes instability of the spike trimer, evidenced by increased spontaneous S1 shedding, as well as contributes to conformational changes, demonstrated by disruption of binding to RBD-targeting monoclonal antibody S309. This destabilization of spike can be explained through homology modeling that shows the loss of critical hydrophobic interactions upon mutation of the residue. The results of this study suggest a critical role for the I692V mutation, which is not in the receptor-binding domain of S1, for impacting furin cleavage site accessibility, therefore underscoring the critical role of non-RBD spike mutations in modulating viral infectivity, transmission capability and pathogenesis of SARS-CoV-2.
Keywords: SARS-CoV-2, reverse zoonosis, mink cluster 5 variant