Swine acute diarrhea syndrome coronavirus nsp10 antagonizes IFN-λ1 production via synergizing with hnRNPU and blocking IRF1 NUclear Translocation.

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a bat-origin porcine enteric alphacoronavirus first identified in Guangdong, China in 2017, which causes severe watery diarrhea and high mortality in neonatal piglets, leading to in substantial economic losses to the global swine industry. Here, we report that SADS-CoV nsp10 functions as an IFN-λ1 antagonist. Specifically, nsp10 suppressed IFN-λ1 production independently of its zinc finger domains. Furthermore, nsp10 inhibits MAVS- and IRF1-driven IFN-λ1 expression within the RLR signaling pathway. Nsp10 blocks poly (I:C)-induced nuclear translocation of IRF1, although no direct physical interaction is detected between the two proteins. Pull-down assays combined with mass spectrometry identified hnRNPU as a nsp10-interacting protein and their direct interaction was verified by co-immunoprecipitation (Co-IP). hnRNPU alone inhibits IFN-λ1 production and synergizes with nsp10 to enhance this suppression, consequently facilitating SADS-CoV replication. Collectively, our findings uncover a previously unrecognized immune evasion mechanism employed by SADS-CoV and provide a potential therapeutic target for controlling coronavirus infections.