Flaviviruses Hijack HuR to Suppress CNPY3: A Novel Pathway for Immune Evasion and Therapeutic Intervention

Flaviviruses represent a serious global health threat, infecting millions annually with high rates of cross-infection among different flaviviruses, yet no broad-spectrum antiviral therapy currently targets these pathogens. Through biological big data analysis, we observed a significant downregulation of Canopy FGF Signaling Regulator 3 (CNPY3), a positive regulator of defense responses, in flavivirus-infected patients, with the level of downregulation correlating with infection severity. This observation was validated in cellular and animal models. Mechanistically, we demonstrate that flaviviruses hijack the RNA-binding protein Human antigen R (HuR) to destabilize CNPY3 mRNA via adenine-uridine-rich elements (AREs), thus downregulating CNPY3 expression and promoting viral replication. Our findings identify CNPY3 as a novel antiviral mediator essential for the TLR-mediated type I interferon (IFN-I) pathway in defense against flaviviruses. In vitro, CNPY3 overexpression reduced DENV and ZIKV replication, confirming its antiviral role. To explore therapeutic potential, we developed lipid nanoparticles (LNPs) encapsulating CNPY3 mRNA (LNP-CNPY3), and early administration in flavivirus-infected mice improved survival, reduced viral loads, and attenuated neuroinflammation by enhancing antiviral and interferon responses. Together, these findings establish CNPY3 as a critical antiviral target and support LNP-CNPY3 as a promising therapeutic approach against flavivirus infections.