SARS-CoV-2 Open Reading Frame 8 protein (ORF8) (ORF8)

The SARS-CoV-2 Open Reading Frame 8 (ORF8) protein is a 121-amino acid accessory protein that serves as a major factor in viral pathogenesis and immune evasion (UniProt P0DTC8). It is characterized by a unique immunoglobulin (Ig)-like fold and the ability to form disulfide-linked dimers, which are essential for its structural stability and function (Flower et al., 2021). One of its primary roles is the downregulation of Major Histocompatibility Complex class I (MHC-I) molecules through a lysosome-dependent degradation pathway, which prevents the recognition of infected cells by cytotoxic T lymphocytes (Zhang et al., 2020). Furthermore, ORF8 acts as a potent antagonist of the type I interferon (IFN) signaling pathway, suppressing the host's innate antiviral response (Li et al., 2020). It is also a secreted protein, and its presence in patient serum has been linked to disease severity and the induction of pro-inflammatory pathways, contributing to the systemic inflammation observed in severe COVID-19 cases (Wang et al., 2021). While ORF8 is a promising target for therapeutic intervention, its high evolutionary rate and the occurrence of significant deletions in certain variants, such as the B.1.1.7 (Alpha) lineage, pose challenges for long-term drug and vaccine development (Neches et al., 2021).

Other names

Accessory protein 8NS8ORF8 proteinNon-structural protein 8SARS-CoV-2 ORF8

ORF8 facilitates immune evasion by mediating the autophagic and lysosomal degradation of MHC-I molecules, thereby preventing viral antigen presentation to CD8+ T cells (Zhang et al., 2020). It also acts as a potent antagonist of the type I interferon (IFN) signaling pathway by inhibiting the phosphorylation of STAT1 and STAT2, which blocks the expression of interferon-stimulated genes (Li et al., 2020).