SARS-CoV-2 ORF8: an accessory protein at the interface of immune evasion and inflammation
SARS-CoV-2 ORF8 is a rapidly evolving accessory protein that modulates host immunity through both intracellular and extracellular mechanisms. Intracellularly, ORF8 disrupts antigen presentation by reducing cell-surface MHC-I and is linked to endoplasmic reticulum remodeling and altered stress responses. Extracellularly, secreted ORF8 behaves as a virokine that can amplify inflammatory programs in myeloid and dendritic cells, with potential implications for acute severity and tissue-specific pathology. ORF8 is also reported to antagonize type I interferon induction through effects on IRF3-dependent pathways. Clinically, circulating ORF8 has been associated with disease severity, and persistent detection of ORF8 after viral RNA becomes undetectable has been reported in some individuals with post-acute symptoms. However, whether this persistence reflects a direct pathogenic role or instead marks ongoing viral burden and immune activation remains unresolved. In this review, we summarize recent findings on the pleiotropic effects of ORF8 and outline key priorities to clarify when ORF8 acts primarily as an immune-evasion factor, an inflammatory amplifier, or both. Collectively, the evidence reviewed here identifies ORF8 as a promising candidate for further mechanistic studies, whose biomarker potential and therapeutic relevance warrant rigorous evaluation in acute and post-acute COVID-19.