RIG-I-mediated protection from SARS-CoV-2 virus replication

Abstract

The COVID 19 pandemic has rapidly spread across the world highlighting its high transmissibility. In previous studies we could demonstrate that RIG-I activation induces an effective protective innate immunity against H1N1 influenza infection in vitro and in vivo. Here we analyzed the effect of prophylactic activation of RIG-I by its specific ligand 5 -triphosphate RNA (3pRNA) or of typeI/III interferons on SARS-CoV-2 infection in air-liquid interface cultivated primary nasal epithelial cells (PNEC) and Caco cells. MAVS-/- (downstream of RIG-I) deficient Caco-cells were used as a control. Viral replication was analyzed by plaque assay and qPCR. Furthermore, interferon-stimulated genes and ACE2/TMPRSS2 were determined on the transcriptional level and IP-10 protein was quantified in supernatants by ELISA. Upon transfection with 3pRNA at 6h prior to infection, Caco WT cells produced more than 8000 pg/ml IP-10. Infection with SARS-CoV-2 significantly decreased the average of 3pRNA-induced IP-10 production to 5000 pg/ml, whereas type I/III interferon and/or SARS-CoV-2 infection alone did not lead to relevant IP-10 production. 3pRNA pretreatment of Caco WT cells infected with SARS-CoV-2 significantly reduced virus replication at 48 h by an average of 91,4% . Pretreatment with type I and III interferon had little effect on virus replication. Analysis of viral RNA in RIG-I-pretreated cells revealed an average reduction of SARS-CoV-2- RNA by 40-fold. Results were also achieved in PNEC showing similar levels in reduction of viral replication and high levels of IP-10 production. Thus, our findings support the concept that RIG-mediated protection of epithelial cells from SARS-CoV-2 replication is a promising strategy to mitigate SARS-CoV-2 infection in vivo.