SARS-CoV-2 Spike evolution influences GBP and IFITM sensitivity

Abstract

SARS-CoV-2 spike requires proteolytic processing for viral entry. The presence of a polybasic furin-cleavage site (FCS) in spike, and evolution towards an optimised FCS by dominant variants of concern (VOCs), are linked to enhanced infectivity and transmission. Here we show that interferon-inducible antiviral restriction factors Guanylate binding proteins (GBP) 2 and 5 interfere with furin-mediated cleavage of SARS-CoV-2 spike and inhibit the infectivity of early-lineage Wuhan-Hu-1, while VOCs Alpha and Delta have evolved to escape restriction. Strikingly, we find Omicron is unique amongst VOCs, being restricted by GBP2/5, and also IFITM1, 2 and 3. Replacing the spike S2 domain in Omicron with Delta shows S2 is the determinant of entry route and IFITM sensitivity. We conclude that VOC evolution under different selective pressures has influenced sensitivity to spike-targeting restriction factors, with Omicron selecting spike changes that not only mediate antibody escape, and altered tropism, but also sensitivity to innate immunity.