Foot-and-Mouth Disease Virus Antagonizes NOD2-Mediated Antiviral Effects by Inhibiting NOD2 Protein Expression

Abstract

The role of nucleotide-binding oligomerization domain 2 (NOD2) in foot-and-mouth disease virus (FMDV)-infected cells remains unknown. Here, we showed that FMDV infection activated NOD2-mediated beta interferon (IFN-␤) and nuclear factor-B (NF-B) signaling pathways. NOD2 inhibited FMDV replication in the infected cells. FMDV infection triggered NOD2 transcription, while it reduced the abundance of NOD2 protein. Our results revealed that FMDV 2B, 2C, and 3C proteinase (3C pro ) were responsible for the decrease in NOD2 protein levels. 3C pro is a viral proteinase that can cleave multiple host proteins and limit protein synthesis. Our previous studies determined that FMDV 2B suppressed protein expression of RIG-I and LGP2. Here, we found that 3C pro and 2B also decreased NOD2 expression. However, this is the first report that 2C induced the reduction of NOD2 protein levels. We determined that both 2B-and 2C-induced decreases in NOD2 were independent of the cleavage of host eukaryotic translation initiation factor 4 gamma (eIF4G), induction of cellular apoptosis, or proteasome, lysosome, and caspase pathways. The interactions between NOD2 and 2B or 2C were observed in the context of viral infection. The carboxyl-terminal amino acids 105 to 114 and 135 to 144 of 2B were essential for the reduction of NOD2, while the residues 105 to 114 were required for the interaction. Amino acids 116 to 260 of the carboxyl terminus of 2C were essential for the interaction, while truncated 2C mutants did not reduce NOD2. These data suggested novel antagonistic mechanisms of FMDV that were mediated by 2B, 2C, and 3C pro proteins. IMPORTANCE NOD2 was identified as a cytoplasmic viral pattern recognition receptor in 2009. Subsequently, many viruses were reported to activate NOD2-mediated signaling pathways. This study demonstrated that FMDV infection activated NOD2mediated IFN-␤ and NF-B signaling pathways. Host cells have developed multiple strategies against viral infection; however, viruses have evolved many strategies to escape host defenses. FMDV has evolved multiple mechanisms to inhibit host type I IFN production. Here, we showed that NOD2 suppressed FMDV replication during viral infection. FMDV 2B, 2C, and 3C pro decreased NOD2 protein expression by different mechanisms to promote viral replication. This study provided new insight into the immune evasion mechanisms mediated by FMDV and identified 2B, 2C, and 3C pro as antagonistic factors for FMDV to evade host antiviral responses.

Molecular Mechanisms of Immune Escape for Foot-and-Mouth Disease Virus

“…Another study showed that FMDV 2B protein interacts with NOD2 to reduce the expression of NOD2 protein, for which the 2B carboxyl-terminal 105-114 region was essential, thus inhibiting the activation of NF-κB and IFN-β signaling pathways (Figure 3, Table 2). The decrease in NOD2 is not related to the cleavage of EIF4G, induction of apoptosis or proteasome, nor lysosome or caspase pathways [16].…”

“…However, the exact mechanism of governing vimentin cage formation and dissolution remains to be elucidated [108]. The interaction between FMDV protein 2C and NOD2 reduces the level of NOD2 protein to help the virus evade the immune response, and the carboxyl-terminal 116-209 and 210-260 regions of 2C were essential for the interaction [16] (Figure 3, Table 2). Strikingly, the interaction between 2C and Beclin1 or NOD2 evades immune response through different pathways, which contributes to the replication of FMDV.…”

“…The interaction between FMDV 3A and DDX56 suppresses the host innate immunity by reducing the phosphorylation of IRF3 [14]. In addition, nucleotide-binding oligomerization domain 2 (NOD2), a member of the nucleotide-binding oligomerization domain-like receptor (NLR) family [15], activates the NF-κB and IFN-β signaling pathways during FMDV infection and inhibits the replication of FMDV in infected cells [16]. FMDV 2B, 2C, and 3C pro inhibit the expression of NOD2 protein, which antagonizes the antiviral response [16].…”

“…In addition, nucleotide-binding oligomerization domain 2 (NOD2), a member of the nucleotide-binding oligomerization domain-like receptor (NLR) family [15], activates the NF-κB and IFN-β signaling pathways during FMDV infection and inhibits the replication of FMDV in infected cells [16]. FMDV 2B, 2C, and 3C pro inhibit the expression of NOD2 protein, which antagonizes the antiviral response [16]. Reportedly, multiple structural and non-structural proteins of FMDV escape the killing of the host immune system.…”

Advances in Foot-and-Mouth Disease Virus Proteins Regulating Host Innate Immunity

“…Moreover, 2B can decrease the expression levels of MDA5 and RIG-I followed by disrupting the phosphorylation of key factors TBK1 and IRF3, thereby inhibiting the IFN-β production in the RLRs antiviral signaling pathway ( Zhu et al, 2016 ; Li et al, 2018 ). Recent study has demonstrated that 2B affects the NF-κB and IFN-β signaling pathway by downregulating nucleotide-binding oligomerization domain 2 (NOD2) expression to enhance FMDV replication ( Liu et al, 2019 ). In addition, interaction of 2B with the host Cyclophilin A (CypA) reduced CypA-mediated degradation of L pro to promote FMDV replication ( Liu et al, 2018 ).…”