# Advancements in Research on Duck Tembusu Virus Infections
## 5 Innate Immune Responses
DTMUV has developed several strategies to disrupt innate immunity and promote productive infection. For instance, DTMUV can encode various NS proteins that inhibit the production of IFN-\(\beta\) by targeting similar cellular components [135]. Research indicates that the non-structural protein NS1 of DTMUV interacts with IPS1 through RIG-I and MDA5, impairing the RLR receptor signaling cascade. NS1 protein interacts with the CARD domains of RLR adapters, hindering the recognition and association with viral moieties. Disruption of this interaction inhibits RLR-mediated IFN-\(\beta\) production, ultimately promoting immune evasion. DTMUV NS1 disrupts the RLR pathway in HEK293 cells by targeting STING, thereby inhibiting virus-induced IFN-\(\beta\) expression [136]. DTMUV NS2A inhibits the IFN-\(\beta\) signaling pathway by competitively binding to STING, thereby reducing the phosphorylation of TBK1. The region spanning amino acids 114-143 of NS2A is crucial for its interaction with STING and inhibition of STING-mediated IFN-\(\beta\) signaling [137]. DTMUV NS2A competes with duTBK1 for binding to duSTING, disrupting duSTING-duSTING interaction and reducing duTBK1 phosphorylation, subsequently suppressing IFN-\(\beta\) production and compromising duSTING-dependent antiviral cellular defenses. Key residues in duSTING, including W164, Y167, and S361, are essential for this interaction [138]. The upregulation of the RLR genes RIG-I and MDA-5 early in the course of in vivo infection induced increased expression of type I IFNs [123; 124; 125]. [PERSON] et al. investigated the role of the NS2B protein during viral infection of HEK293T cells and found its interaction with participants in the RIG-I pathway, leading to the inhibition of type I interferon responses. The NS2B-NS3 protease complex of the virus may also suppress the production of IFN-\(\beta\). Unlike NS1, the NS2B-NS3 protease complex directly interacts with the duck STING protein in the mitochondria, a key intermediate in the RLR pathway, to inhibit signaling transduction and reduce IFN-\(\beta\) production. In this case, the synthesis rate of ISG-related proteins (Mx1 and OASL) is also downregulated [138; 139]. Interestingly, the NS2B-NS3 proteinase complexes of Zika virus (ZIKV) and DENV have the same cleavage site in duSTING as DTMUV, suggesting similarities between DTMUV and other flaviviruses in their evasion mechanisms [140]. The NS2A protein's role in RLR signaling transduction was also studied by the same research group, yielding similar results with changes in the activity of the STING protein [141]. Similar to NS2B, the binding of NS2A to STING is also associated with the inhibition of TBK1 phosphorylation, leading to the suppression of IFN-\(\beta\) production [138]. TMUV NS2B specifically interacts with mitochondrial antiviral signaling protein (duMAVS) to mediate ubiquitination and proteasomal degradation, thereby inhibiting the production of IFN [142]. NS2B is capable of inhibiting MDA5- or poly (I:C)-mediated IFN-\(\beta\) production, and this inhibitory effect is weakened when amino acid residues 51 to 92 (hydrophilic region) are deleted, indicatingthe importance of the hydrophilic region of NS2B for its interaction with the host innate immune system [143]. The DTMUV NS4B protein can inhibit IFN-\(\beta\) production. Among NS2A, NS2B, and NS4B, DTMUV's NS4B protein has been identified as a key inhibitor of the RLR pathway, leading to decreased expression of RIG-I, MDA5, MAVS, STING, and TBK1. Moreover, specific mutations in the NS4B protein modify its interaction with TBK1, resulting in phenotypic changes and reduced pathogenicity of DTMUV. Thus, NS4B seems to strongly interact with TBK1 and inhibit its recruitment via STING, ultimately leading to pathway blockade [144]. These studies confirm the importance of TBK1 in executing effective antiviral responses, as reported by [PERSON] et al., and reveal strategies employed by DTMUV to overcome immune responses [128].