Role of nucleotide-binding oligomerization domain 1 (NOD1) and its variants in human cytomegalovirus control in vitro and in vivo

Abstract

Induction of nucleotide-binding oligomerization domain 2 (NOD2) and downstream receptor-interacting serine/threonine-protein kinase 2 (RIPK2) by human cytomegalovirus (HCMV) is known to up-regulate antiviral responses and suppress virus replication. We investigated the role of nucleotide-binding oligomerization domain 1 (NOD1), which also signals through RIPK2, in HCMV control. NOD1 activation by Tri-DAP (NOD1 agonist) suppressed HCMV and induced IFN-β. Mouse CMV was also inhibited through NOD1 activation. NOD1 knockdown (KD) or inhibition of its activity with small molecule ML130 enhanced HCMV replication in vitro. NOD1 mutations displayed differential effects on HCMV replication and antiviral responses. In cells overexpressing the E56K mutation in the caspase activation and recruitment domain, virus replication was enhanced, but in cells overexpressing the E266K mutation in the nucleotidebinding domain or the wild-type NOD1, HCMV was inhibited, changes that correlated with IFN-β expression. The interaction of NOD1 and RIPK2 determined the outcome of virus replication, as evidenced by enhanced virus growth in NOD1 E56K mutant cells (which failed to interact with RIPK2). NOD1 activities were executed through IFN-β, given that IFN-β KD reduced the inhibitory effect of Tri-DAP on HCMV. Signaling through NOD1 resulting in HCMV suppression was IKKα-dependent and correlated with nuclear translocation and phosphorylation of IRF3. Finally, NOD1 polymorphisms were significantly associated with the risk of HCMV infection in women who were infected with HCMV during participation in a glycoprotein B vaccine trial. Collectively, our data indicate a role for NOD1 in HCMV control via RIPK2-IKKα-IRF3 and suggest that its polymorphisms predict the risk of infection.H uman cytomegalovirus (HCMV), a member of the herpesvirus family, induces complex innate immune responses (1, 2). Despite this effective and multifaceted induction, HCMV has developed strategies to counteract its recognition (3), allowing for its productive replication and the establishment of latency. Identification and characterization of HCMV-induced innate immune responses and resulting signaling pathways may provide novel strategies for its control.Mounting evidence indicates that HCMV sensing is an intricate process involving activities of membrane, cytoplasmic, and nuclear receptors. Several HCMV-encoded proteins directly activate innate immune response molecules; the glycoprotein B (gB) binds to and activates TLR2 (4), and pp65 interacts with IFI16 (5). Other viral proteins, dsDNA, or dsRNA are likely to activate or inhibit host innate response molecules. Several previous reports have highlighted a complex role of the IFN pathway in response to HCMV. The activity of the promyeolcytic leukemia protein, a regulator of type I IFN response, is counteracted by HCMV-encoded immediate early 1 protein (IE1) (6). A cytoplasmic dsDNA sensor, ZBP1, activates IRF3 on infection, and its overexpression inhibits HCMV replication (7). IFN-inducible protein IFI16 modestly in...

NOD1 and NOD2: Beyond Peptidoglycan Sensing

“…In the context of viral infection, however, pre-stimulation of NOD2 with bacterial ligands may be beneficial, since MDP treatment of dendritic cells improved their ability to prime virus-specific CD8 T cells in the context of influenza A virus infection [59]. While the NOD2-activating viruses discussed above all have ssRNA genomes, it is interesting to note that both NOD1 and NOD2 have been implicated in the response to human cytomegalovirus (HCMV), which has a double-stranded DNA genome [61, 62]. This raises the question of the stimulus sensed by NOD1 and NOD2 during HCMV infection.…”

NOD1 and NOD2 in inflammatory and infectious diseases

“…NOD1 can also participate in type I IFN signaling independently of MAVS. Stimulation of intestinal epithelial cells or hepatocytes with NOD1 ligand (ie, iE‐DAP or TriDAP) induces IFN‐β production that is dependent on RIPK2 91,92 . In particular, stimulation of cells with NOD1 ligand results in RIP2 binding to TRAF3, which then leads to recruitment and activation of TANK‐binding kinase 1 (TBK1), IκB kinase e (IKKε), and IRF7 to induce IFN‐β production and signaling via the ISGF3 pathway 92 …”

“…Consequently, administration of DAP in vivo resulted in increased hepatitis B virus (HBV)‐specific T cell responses in vivo and replication of HBV 140 . Mice pretreated with the NOD1 ligand iE‐DAP also exhibited reduced CMV load after infection, 91 and the combination of iE‐DAP and MDP enhanced inhibition of CMV replicative activity which required type I IFNs 91 . These results suggest that exposure to bacteria and stimulation of NOD1 and NOD2 can augment antiviral immunity.…”

Polymorphisms in pattern recognition receptor genes of indigenous and White Leghorn breeds of chicken

“…Expression of the NOD1 gene is found to be induced in Salmonella enterica serovar Enteritidis (Tao et al, 2015) and Salmonella pullorum (Tao et al, 2017) infections in chickens (Tao et al, 2015). Polymorphism in the NOD1 gene in humans was reported to be linked with Helicobacter pylori pathogenesis (Hofner et al, 2007;Kara et al, 2010), Chlamydia trachomatis infection (Branković et al, 2015) and cytomegalovirus control (Fan et al, 2016). The NS SNPs observed in this study could play a role in resistance to various infectious diseases in chickens, S. Haunshi et al: Polymorphisms in pattern recognition receptor genes and their effect on innate immunity needs to be investigated in detail through pathogen challenge studies.…”