An invertebrate NLR recognizes viral nucleic acids and balances the antiviral signaling pathway through interaction with STING and Cyclophilin A.

Intracellular recognition of viral nucleic acids by NLRs and subsequent activation of antiviral immunity are crucial for host defense against virus infection in vertebrates. However, understanding on these processes is very limited in invertebrates, especially for crustaceans. In the present study, an NLR gene belonging to the NLRC subfamily (LvNLRC) was identified in the Pacific whiteleg shrimp Litopenaeus vannamei and its functions in intracellular recognition to DNA virus and antiviral immunity during WSSV infection were elucidated. LvNLRC possesses an ability to detect DNA viral mimics such as poly(dA:dT) with a dose-dependent manner through its leucine-rich repeat (LRR) domain. The LRRs domain also recognizes the partial DNA encoding VP24 of WSSV. LvNLRC could modulate the interferon system-like antiviral response in shrimp through direct interaction between its NACHT domain and LvSTING. Different from the regulatory mechanism in vertebrates, the presence of poly(dA:dT) does not affect the release of STING from the NACHT domain of LvNLRC in shrimp. Interestingly, shrimp Cyclophilin A (LvCypA) can directly interact with the NACHT domain of LvNLRC in a dose-dependent manner in the presence of poly(dA:dT). Furthermore, LvCypA also plays an important role in the regulation of the interferon system-like antiviral immunity in shrimp. The present results provide the first evidence to show that Cyclophilin A can modulate NLR-mediated cytokine-like antiviral immunity in animals. These findings shed light on the roles of NLRs in regulating host innate immunity, contributing valuable insights into this area of study.