Circulating cholesterol fuels SARS-CoV-2 replication via ORF3a.

High levels of "bad" cholesterol increase the risk of cardiovascular disease and are also linked to more severe COVID-19, though the reason has been unclear. We show that low-density lipoprotein (LDL) directly enhances SARS-CoV-2 RNA replication, especially in the Beta variant. The viral accessory protein ORF3a is both necessary and sufficient to increase cholesterol uptake in cell culture and hamster models. ORF3a stabilizes the host LDL receptor by displacing the PCSK9 chaperone, leading to greater cholesterol entry into cells. While wild-type ORF3a disrupts endosomal acidification and limits cholesterol recycling through interaction with VPS39 (part of the HOPS complex), the Beta variant does not, allowing more efficient cholesterol recovery and stronger LDL responsiveness. Overall, our findings show that SARS-CoV-2 can directly link its replication to host cholesterol levels via ORF3a. This mechanism may help guide antiviral strategies, particularly for individuals with high cholesterol.