Dengue Virus 2 NS2B Targets MAVS and IKKε to Evade the Antiviral Innate Immune Response.

Dengue virus (DENV) is a widespread arbovirus. To efficiently establish infection, DENV evolves multiple strategies to hijack the host innate immune response. Herein, we examined the inhibitory effects of DENV serotype 2 (DENV2) nonstructural proteins on RIG-I-directed antiviral immune response. We found that DENV2 NS2A, NS2B, NS4A, and NS4B significantly inhibited RIG-I-mediated IFN-ß promoter activation. The roles of NS2B in RIG-I-directed antiviral immune response are unknown. Our study further showed that NS2B could dose-dependently suppress RIG-I/MAVS-induced activation of IFN-ß promoter. Consistently, NS2B significantly decreased RIG-I- and MAVS-induced transcription of IFNB1, ISG15, and ISG56. Mechanistically, NS2B was found to interact with MAVS and IKKε to impair RIG-I-directed antiviral response. Our findings demonstrated a previously uncharacterized function of NS2B in RIG-I-mediated antiviral response, making it a promising drug target for anti-DENV treatments.

SARS-CoV-2 ORF3a positively regulates NF-κB activity by enhancing IKKß-NEMO interaction.

Coronavirus disease 2019 (COVID-19) is a global pandemic caused by SARS-CoV-2 infection. Patients with severe COVID-19 exhibit robust induction of proinflammatory cytokines, which are closely associated with the development of acute respiratory distress syndrome. However, the underlying mechanisms of the NF-κB activation mediated by SARS-CoV-2 infection remain poorly understood. Here, we screened SARS-CoV-2 genes and found that ORF3a induces proinflammatory cytokines by activating the NF-κB pathway. Moreover, we found that ORF3a interacts with IKKß and NEMO and enhances the interaction of IKKß-NEMO, thereby positively regulating NF-κB activity. Together, these results suggest ORF3a may play pivotal roles in the pathogenesis of SARS-CoV-2 and provide novel insights into the interaction between host immune responses and SARS-CoV-2 infection.