Secreted SARS-CoV-2 ORF8 modulates the cytokine expression profile of human macrophages

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still adapting to its new human host. Attention has focussed on the viral spike protein, but substantial variation has been seen in the ORF8 gene. Here, we show that SARS-CoV-2 ORF8 protein undergoes signal peptide-mediated processing through the endoplasmic reticulum and is secreted as a glycosylated, disulphide-linked dimer. The secreted protein from the prototype SARS-CoV-2 virus had no major effect on viability of a variety of cell types, or on IFN or NF-{kappa}B signalling. However, it modulated cytokine expression from primary CSF1-derived human macrophages, most notably by decreasing IL-6 and IL-8 secretion. Furthermore, a sequence polymorphism L84S that appeared early in the pandemic associated with the Clade S lineage of virus, showed a markedly different effect, of increasing IL-6 production. We conclude that ORF8 sequence polymorphisms can potentially affect SARS-CoV-2 virulence and should therefore be monitored in sequencing-based surveillance.