African Swine Fever Virus pI215L Negatively Regulates cGAS-STING Signaling Pathway through Recruiting RNF138 to Inhibit K63-Linked Ubiquitination of TBK1

Abstract

African swine fever is a severe animal infectious disease caused by African swine fever virus (ASFV), and the morbidity and mortality associated with virulent ASFV isolates are as high as 100%. Previous studies showed that the ability of ASFV to antagonize IFN production is closely related to its pathogenicity. Here, we report that ASFV HLJ/18 infection induced low levels of type I IFN and inhibited cGMP-AMP–induced type I IFN production in porcine alveolar macrophages that were isolated from specific pathogen-free Landrace piglets. Subsequently, an unbiased screen was performed to screen the ASFV genes with inhibitory effects on the type I IFN production. ASFV pI215L, a viral E2 ubiquitin–conjugating enzyme, was identified as one of the strongest inhibitory effectors on the production of type I IFN. Knockdown of pI215L expression inhibited ASFV replication and enhanced IFN-β production. However, inhibition of type I IFN production by pI215L was independent of its E2 enzyme activity. Furthermore, we found that pI215L inhibited type I IFN production and K63-linked polyubiquitination of TANK-binding kinase 1 through pI215L-binding RING finger protein 138 (RNF138). ASFV pI215L enhanced the interaction between RNF138 and RNF128 and promoted RNF138 to degrade RNF128, which resulted in reduced K63-linked polyubiquitination of TANK-binding kinase 1 and type І IFN production. Taken together, our findings reveal a novel immune escape mechanism of ASFV, which provides a clue to the design and development of an immune-sensitive attenuated live vaccine.

The Swine IFN System in Viral Infections: Major Advances and Translational Prospects

“…Most recently, Reis and colleagues reported that deletion and interruption of several genes within MGF360 and MGF530/505 regions in virulent Benin 97/1 strain led to the induction of high levels of IFN-β mRNA in vitro, compared to the naturally virulent Benin 97/1 strain [250]. This wasconfirmed by a previously mentioned study [239,[266][267][268][269], according to which virulent strains evolved multiple strategies, in order to evade and modulate the innate immune system, by limiting or impairing type I and II IFN responses.…”

“…According to the literature, ASFV virulent strains seem to have developed mechanisms to suppress type I IFN induction; differently, attenuated strains might have partially lost some of these immune evasion mechanisms [239,[266][267][268][269]. Correia et al demonstrated that ASFV-encoded multigene families (MGFs) inhibit the type I and II IFN response by targeting different intracellular signaling intermediates.…”

I226R Protein of African Swine Fever Virus Is a Suppressor of Innate Antiviral Responses

“…For example, MGF505-7R upregulates the expression of autophagy-related protein ULK1 and promotes the degradation of STING to negatively regulate the cGAS/STING signaling pathway [ 19 ]; MGF360-12L inhibits the interaction of KPNA2, KPNA3, and KPNA4 with p65, thereby suppressing the nuclear import of NF-κB [ 46 ]. Moreover, ASFV I215L has recently been shown to inhibit type І IFN production by reducing K63-linked polyubiquitination of TBK1 [ 48 ]. Another previous study indicated that transient overexpression of I215L inhibited NF-κB and AP-1, but not IRF-3-dependent signaling [ 49 ], which is consistent with our data suggesting that overexpression of I215L had no significant effect on the activation of the IFN-β promoter by SeV in 293T cells.…”

Myxoma virus lacking the host range determinant M062 stimulates cGAS-dependent type 1 interferon response and unique transcriptomic changes in human macrophages

“…Other than negative feedback cascade to restrict the duration and extent of IFN-I responses, e.g., SOCS, regulation of IFN-α receptor (IFNAR), and USP18 (38-40), intracellular signaling events and miRNAs can also perform such function (41). Upstream of IFN-I production, there are also regulatory measures to pattern recognition receptors (PRRs) and their adaptors, e.g., AKT to cGAS (42), TMEM120A to STING (43), and RNF138 to TBK1 (44). Our work provides evidence of a novel mechanism to fine tune the IFN-I response, which may operate through cellular translation regulation to PRR activation ( Figure 7 ), and ultimately alters the global transcriptional landscape.…”