Suppressive effects of sirtinol on human cytomegalovirus (hCMV) infection and hCMV-induced activation of molecular mechanisms of senescence and production of reactive oxygen species

DNA damage response(DDR): a link between cellular senescence and human cytomegalovirus

The DNA damage response (DDR) is a signaling cascade that is triggered by DNA damage, involving the halting of cell cycle progression and repair. It is a key event leading to senescence, which is characterized by irreversible cell cycle arrest and the senescence-associated secretory phenotype (SASP) that includes the expression of inflammatory cytokines. Human cytomegalovirus (HCMV) is a ubiquitous pathogen that plays an important role in the senescence process. It has been established that DDR is necessary for HCMV to replicate effectively. This paper reviews the relationship between DDR, cellular senescence, and HCMV, providing new sights for virus-induced senescence (VIS).

Inhibition of SIRT2 promotes death of human cytomegalovirus-infected peripheral blood monocytes via apoptosis and necroptosis

Peripheral blood monocytes are the cells predominantly responsible for systemic dissemination of human cytomegalovirus (HCMV) and a significant cause of morbidity and mortality in immunocompromised patients. HCMV establishes a silent/quiescent infection in monocytes, which is defined by the lack of viral replication and lytic gene expression. The absence of replication shields the virus within infected monocytes from the current available antiviral drugs that are designed to suppress active replication. Our previous work has shown that HCMV stimulates a noncanonical phosphorylation of Akt and the subsequent upregulation of a distinct subset of prosurvival proteins in normally short-lived monocytes. In this study, we found that SIRT2 activity is required for the unique activation profile of Akt induced within HCMV-infected monocytes. Importantly, both therapeutic and prophylactic treatment with a novel SIRT2 inhibitor, FLS-379, promoted death of infected monocytes via both the apoptotic and necroptotic cell death pathways. Mechanistically, SIRT2 inhibition reduced expression of Mcl-1, an Akt-dependent antiapoptotic Bcl-2 family member, and enhanced activation of MLKL, the executioner kinase of necroptosis. We have previously reported HCMV to block necroptosis by stimulating cellular autophagy. Here, we additionally demonstrate that inhibition of SIRT2 suppressed Akt-dependent HCMV-induced autophagy leading to necroptosis of infected monocytes. Overall, our data show that SIRT2 inhibition can simultaneously promote death of quiescently infected monocytes by two distinct death pathways, apoptosis and necroptosis, which may be vital for limiting viral dissemination to peripheral organs in immunosuppressed patients.

Sirtuins: Key pieces in the host response to pathogens' puzzle

Global warming is changing the distribution of different pathogens around the globe, and humans are more susceptible to new or re-emerging infections. The human response to microbes is complex and involves different mechanisms of the immune system. Regulation of gene expression of immunity genes and of metabolism of immune cells are essential in this process. Both mechanisms could be regulated by protein lysine acetylation that will control chromatin structure affecting gene expression or key enzyme activity involved in cellular processes. Protein acetylation is crucial for the immunity and involves two families of enzymes: lysine acetyltransferases (KATs), which will promote protein acetylation, and lysine deacetylases (KDACs) that will reduce this modification. Lysine deacetylases are divided into Zinc-dependent or HDACs and NAD⁺ -dependent, or Sirtuins. These enzymes are in the nucleus, cytosol, and mitochondria of mammalian cells affecting different cellular pathways, such as metabolism, gene expression, DNA repair, cell proliferation, and apoptosis, opening the opportunity to explore these proteins as drug targets in different diseases, including cancer and neurodegenerative illness. Although widely explored in chronic diseases, very little is known about the role of Sirtuins during host response against microbes' infection. In this review we aim to explore the most recent literature evidencing a role for these enzymes during host responses to viruses, bacterial and protozoan infections, pointing out how these proteins can be manipulated by these pathogens to progress in the infection. Moreover, we will uncover the potential of host KDACs as therapeutic targets to prevent infections by activating effector immune functions.

An allosteric inhibitor of sirtuin 2 deacetylase activity exhibits broad-spectrum antiviral activity

Most drugs used to treat viral disease target a virus-coded product. They inhibit a single virus or virus family, and the pathogen can readily evolve resistance. Host-targeted antivirals can overcome these limitations. The broad-spectrum activity achieved by host targeting can be especially useful in combating emerging viruses and for treatment of diseases caused by multiple viral pathogens, such as opportunistic agents in immunosuppressed patients. We have developed a family of compounds that modulate sirtuin 2, an NAD+-dependent deacylase, and now report the properties of a member of that family, FLS-359. Biochemical and x-ray structural studies show that the drug binds to sirtuin 2 and allosterically inhibits its deacetylase activity. FLS-359 inhibits the growth of RNA and DNA viruses, including members of the coronavirus, orthomyxovirus, flavivirus, hepadnavirus, and herpesvirus families. FLS-359 acts at multiple levels to antagonize cytomegalovirus replication in fibroblasts, causing modest reductions in viral RNAs and DNA, together with a much greater reduction in infectious progeny, and it exhibits antiviral activity in humanized mouse models of infection. Our results highlight the potential of sirtuin 2 inhibitors as broad-spectrum antivirals and set the stage for further understanding of how host epigenetic mechanisms impact the growth and spread of viral pathogens.

Suppressive effects of pterostilbene on human cytomegalovirus (HCMV) infection and HCMV-induced cellular senescence

BACKGROUND

Human cytomegalovirus (HCMV), a member of the β-herpesvirus family, causes the establishment of a latent infection that persists throughout the life of the host and can be reactivated when immunity is weakened. To date, there is no vaccine to prevent HCMV infection, and clinically approved drugs target the stage of viral replication and have obvious adverse reactions. Thus, development of novel therapeutics is urgently needed.

METHODS

In the current study, we identified a naturally occurring pterostilbene that inhibits HCMV Towne strain replication in human diploid fibroblast WI-38 cells through Western blotting, qPCR, indirect immunofluorescence assay, tissue culture infective dose assays. The time-of-addition experiment was carried out to identify the stage at which pterostilbene acted. Finally, the changes of cellular senescence biomarkers and reactive oxygen species production brought by pterostilbene supplementation were used to partly elucidate the mechanism of anti-HCMV activity.

RESULTS

Our findings revealed that pterostilbene prevented lytic cytopathic changes, inhibited the expression of viral proteins, suppressed the replication of HCMV DNA, and significantly reduced the viral titre in WI-38 cells. Furthermore, our data showed that pterostilbene predominantly acted after virus cell entry and membrane fusion. The half-maximal inhibitory concentration was determined to be 1.315 μM and the selectivity index of pterostilbene was calculated as 26.73. Moreover, cell senescence induced by HCMV infection was suppressed by pterostilbene supplementation, as shown by a decline in senescence-associated β-galactosidase activity, decreased production of reactive oxygen species and reduced expression of p16, p21 and p53, which are considered biomarkers of cellular senescence.

CONCLUSION

Together, our findings identify pterostilbene as a novel anti-HCMV agent that may prove useful in the treatment of HCMV replication.

Sulphated glucuronomannan tetramer and hexamer from Sargassum thunbergii exhibit anti-human cytomegalovirus activity by blocking viral entry

Human cytomegalovirus (HCMV) remains a major public health burden worldwide. The anti-HCMV activity of glucuronomannan oligosaccharides (Gs) and sulphated glucuronomannan oligosaccharides (SGs) was investigated. Among these Gs and SGs, G4S1 and G6S1 (higher sulphated glucuronomannan tetramer and hexamer) showed satisfactory anti-HCMV activity starting at 50 μg/mL and 10 μg/mL, respectively. The results of the morphology, western blotting, qPCR and TCID50 assay showed that they prevented lytic cytopathic changes, inhibited the expression of IE1/2 and UL44, and reduced the UL123 copy number and virus titre significantly. It was interesting to note that degree of sulphation and polymerization was more important for anti-HCMV activity. Moreover, the anti-HCMV activities of G4S1 and G6S1 were stable when stored at 4 °C, -20 °C, and -80 °C for at least three months and mainly occurred in the early stage of HCMV infection through the negative charge of the sulphate groups and the interaction between SGs and the host cells.

Nicotinamide riboside, an NAD+ precursor, attenuates inflammation and oxidative stress by activating sirtuin 1 in alcohol-stimulated macrophages

Macrophages play an essential role in alcohol-induced inflammation and oxidative stress. We investigated the effects of nicotinamide riboside (NR), a natural nicotinamide adenine dinucleotide (NAD+) precursor, on alcohol-induced inflammation and oxidative stress in macrophages. NR significantly decreased ethanol-induced inflammatory gene expression, with a concomitant decrease in nuclear translocation of nuclear factor κB p65 in RAW 264.7 macrophages and mouse bone marrow-derived macrophages (BMDMs). In macrophages incubated with ethanol or acetaldehyde, NR abolished the accumulation of cellular reactive oxygen species. Ethanol decreased sirtuin 1 (SIRT1) expression and activity, and cellular NAD+ level while inducing pro-inflammatory gene expression. However, NR markedly attenuated the changes. SIRT1 inhibition augmented ethanol-induced inflammatory gene expression, but its activation elicited opposing effects. Also, ethanol did not alter glycolysis but increased glycolytic capacity, glycolytic reserve, and non-glycolytic acidification, with concomitant increases in hypoxia-induced factor 1α expression and activity, phosphorylation of pyruvate dehydrogenase, and extracellular lactate levels. Interestingly, ethanol increased mitochondrial respiration and ATP production but decreased maximal respiration and spare respiration capacity. The latter was linked to decreases in mitochondrial copy numbers. NR abolished the ethanol-induced metabolic changes in the glycolytic and oxidative phosphorylation pathways in RAW 264.7 macrophages. In conclusion, NR exerts anti-inflammatory and antioxidant properties by abrogating the inhibitory effects of ethanol on the SIRT1 pathway by increasing Sirt1 expression and its activator, NAD+. Also, SIRT1 activation and normalization of ethanol-induced changes in NAD+/NADH ratios by NR are likely crucial to counteract the changes in energy phenotypes of macrophages exposed to ethanol.

Melanoidins, extracted from Chinese traditional vinegar powder, inhibit alcohol-induced inflammation and oxidative stress in macrophages via activation of SIRT1 and SIRT3

Alcohol induces inflammation and oxidative stress with the dysregulation of proinflammatory cytokines, which are implicated in the pathogenesis of alcoholic liver injury. Melanoidins are known to exert an antioxidant effect, however, their function in inhibiting alcohol-induced inflammation is unclear. In this study, we examined the role of melanoidins from Chinese traditional vinegar powder in terms of their anti-inflammatory and antioxidant properties in RAW 264.7 macrophages and elucidated their mechanisms of function. In macrophages, melanoidins significantly suppress the mRNA expression of interleukin (Il)-6, Il-1β and tumor necrosis factor α (Tnf-α) with a concomitant inhibitory effect on IL-1β, IL-6 and TNFα secretion, which are increased by ethanol. In addition, ethanol significantly increases the cellular reactive oxygen species (ROS) levels and the expression of cytochrome β-245 and beta polypeptide (Cybb), which are repressed by melanoidins to basal level. However, the expression of genes related to oxidative stress significantly decreases in response to ethanol, while it is significantly increased by melanoidins. Importantly, treatment with ethanol led to significant decreases in SIRT1 and SIRT3 transcription, translation, and activation, as well as the nicotinamide adenine dinucleotide (NAD⁺) levels. Interestingly, all the decreases were markedly attenuated by melanoidins. Ethanol promoted the expression of proinflammatory genes, whereas coincubation with resveratrol (a potent SIRT agonist) inhibited this effect. Conversely, the addition of sirtinol (a known SIRT inhibitor) augmented the proinflammatory gene expression. Taken together, our findings suggest that melanoidins exert anti-inflammatory and antioxidant functions via abolishing decreases in SIRT1 and SIRT3 expression and cellular NAD⁺ levels in ethanol-induced macrophages and may serve as a new therapeutic agent for the prevention of alcohol-induced cell damage.

The Pleiotropic Function of Human Sirtuins as Modulators of Metabolic Pathways and Viral Infections

Sirtuins (SIRTs) are nicotinamide adenine dinucleotide-dependent histone deacetylases that incorporate complex functions in the mechanisms of cell physiology. Mammals have seven distinct members of the SIRT family (SIRT1-7), which play an important role in a well-maintained network of metabolic pathways that control and adapt the cell to the environment, energy availability and cellular stress. Until recently, very few studies investigated the role of SIRTs in modulating viral infection and progeny. Recent studies have demonstrated that SIRT1 and SIRT2 are promising antiviral targets because of their specific connection to numerous metabolic and regulatory processes affected during infection. In the present review, we summarize some of the recent progress in SIRTs biochemistry and their emerging function as antiviral targets. We also discuss the potential of natural polyphenol-based SIRT modulators to control their functional roles in several diseases including viral infections.

Host Mitochondrial Requirements of Cytomegalovirus Replication

Purpose of Review

Metabolic rewiring of the host cell is required for optimal viral replication. Human cytomegalovirus (HCMV) has been observed to manipulate numerous mitochondrial functions. In this review, we describe the strategies and targets HCMV uses to control different aspects of mitochondrial function.

Recent Findings

The mitochondria are instrumental in meeting the biosynthetic and bioenergetic needs of HCMV replication. This is achieved through altered metabolism and signaling pathways. Morphological changes mediated through biogenesis and fission/fusion dynamics contribute to strategies to avoid cell death, overcome oxidative stress, and maximize the biosynthetic and bioenergetic outputs of mitochondria.

Summary

Emerging data suggests that cytomegalovirus relies on intact, functional host mitochondria for optimal replication. HCMV large size and slow replication kinetics create a dependency on mitochondria during replication. Targeting the host mitochondria is an attractive antiviral target.

Inhibitory effects of piceatannol on human cytomegalovirus (hCMV) in vitro

Human cytomegalovirus (hCMV) is a ubiquitous herpesvirus, which results in the establishment of a latent infection that persists throughout the life of the host and can be reactivated when the immunity is low. Currently, there is no vaccine for hCMV infection, and the licensed antiviral drugs mainly target the viral enzymes and have obvious adverse reactions. Thus, it is important to search for compounds with anti-hCMV properties. The present study aimed to investigate the suppressive effects of piceatannol on hCMV Towne strain infection and the putative underlying mechanisms using human diploid fibroblast WI-38 cells. Piceatannol supplementation prevented the lytic changes induced by hCMV infection in WI-38 cells. Furthermore, piceatannol suppressed the expression of hCMV immediate-early (IE) and early (E) proteins as well as the replication of hCMV DNA in a dose-dependent manner. Moreover, hCMV-induced cellular senescence was suppressed by piceatannol, as shown by a decline in the senescence-associated β-galactosidase (SA-β-Gal) activity and decreased production of intracellular reactive oxygen species (ROS). p16^INK4a, a major senescence-associated molecule, was dramatically elevated by current hCMV infection that was attenuated by pre-incubation with piceatannol in a dose-dependent manner. These results demonstrated that piceatannol suppressed the hCMV infection via inhibition of the activation of p16^INK4a and cellular senescence induced by hCMV. Together, these findings indicate piceatannol as a novel and potent anti-hCMV agent with the potential to be developed as an effective treatment for chronic hCMV infection.

Sulfated galactofucan from Sargassum thunbergii induces senescence in human lung cancer A549 cells

Isolated compounds from Sargassum thunbergii (S. thunbergii) have shown to exhibit diverse biological activities, including anti-cancer activity. In this study, we examined the effect of sulfated galactofucan (SWZ-4-H), which was successfully isolated from S. thunbergii, and its underlying mechanism on human lung cancer (LC) A549 cell growth in vitro and in vivo. In vitro experiment indicated that SWZ-4-H decreased cell growth and number in a dose-dependent manner (P < 0.05 vs. control). Besides, cells treated with SWZ-4-H had irregular morphology, including increased cell volumes, and large nuclei, which suggested senescence-like changes. Moreover, SWZ-4-H increased senescence-related β-galactosidase (SA-β-Gal) staining in a dose-dependent manner; however, while lower (1 mg mL-1) concentration induced mainly senescence without causing cell death, higher dosage (3 mg mL-1) induced both senescence and cell death. The effect of SWZ-4-H was further confirmed by analyzing the expression of p53, p21, p16, and Rb (p-RB); SWZ-4-H significantly increased the expression of p53, p21, and p16 and decreased phosphorylated Rb (p-RB) in a dose-dependent manner. Moreover, in vivo experiment showed that SWZ-4-H significantly reduced the tumor volume without affecting the body weight. To sum up, our data indicated that SWZ-4-H could induce lung cancer senescence by regulating p53, p21, p16, and p-Rb, thus providing a novel perspective on anti-cancer mechanisms of SWZ-4-H in human lung cancer A549 cells.

Sirtuin Inhibitors Are Broadly Antiviral against Arboviruses

Arthropod-borne viruses are diverse pathogens and are often associated with human disease. These viruses span multiple genera, including flaviviruses, alphaviruses, and bunyaviruses. In a high-throughput drug screen, we found that tenovin-1 was antiviral against the flaviviruses Zika virus and dengue virus. Tenovin-1 is a sirtuin inhibitor, and here we found that inhibition of sirtuins, but not inhibition of the related histone deacetylases, is potently antiviral against diverse arboviruses. Sirtuin inhibitors block infection of arboviruses in multiple human cell types. We found that sirtuin inhibitors arrest infection downstream of entry but that they do so at an early step, preventing the accumulation of viral RNA and protein. However, sirtuin inhibitors had no impact on the replication of flaviviral replicons, suggesting a defect in the establishment of replication. Consistent with this, we found that sirtuin inhibitors impacted double-stranded RNA (dsRNA) accumulation during flaviviral infection. Since these viruses infect vector insects, we also tested whether sirtuin inhibitors impacted infection of adult flies and found that these inhibitors blocked infection; therefore, they target highly conserved facets of replication. Taken together, these results suggest that sirtuin inhibitors represent a new class of potent host-targeting antivirals.IMPORTANCE Arthropod-borne viruses are diverse pathogens and are associated with human disease. Through high-throughput drug screening, we found that sirtuin inhibitors are potently antiviral against diverse arboviruses, including flaviviruses such as West Nile virus, bunyaviruses such as Rift Valley fever virus, and alphaviruses such as chikungunya virus. Sirtuin inhibitors block infection of these viruses in multiple human cell types. Moreover, we found that sirtuin inhibitors arrest infection downstream of entry but that they do so at an early step, preventing the accumulation of viral RNA and protein. Since these viruses infect vector insects, we also tested whether sirtuin inhibitors impacted infection of adult flies and found that these inhibitors blocked infection; therefore, they target highly conserved facets of replication. Taken together, these results suggest that sirtuin inhibitors represent a new class of potent host-targeting antivirals.

Chronic Low-grade Inflammatory Phenotype (CLIP) and Senescent Immune Dysregulation

PURPOSE

The aim was to provide an overview of chronic low-grade inflammatory phenotype (CLIP) and evidence for its role in the pathogenesis of frailty and other chronic conditions as well as potential causative factors and interventions.

METHODS

We reviewed evidence from published clinical and laboratory studies and summarized the opinions of experts from published reviews.

FINDINGS

CLIP is a low-grade, systemic, unresolved, and smoldering chronic inflammatory state clearly indicated by a 2- to 4-fold increase in serum levels of inflammatory mediators, such as interleukin-6 and C-reactive protein. It involves many other cellular and molecular inflammatory mediators. CLIP typically occurs during aging, also known as "inflammaging," and is an integral part of the spectrum of immunosenescence. Causative factors likely include persistent viral infections, particularly chronic cytomegalovirus infection, cellular senescence, failure to eliminate degraded materials and waste products, dysregulated microbiota and gut permeability, obesity, and others. Substantial evidence supports CLIP as a powerful contributing factor to frailty and many other chronic conditions and adverse health outcomes. Many of the inflammatory mediators and their regulatory mechanisms in CLIP may serve as potential targets for therapeutic intervention. However, development of new interventional strategies for CLIP and its associated chronic conditions should take the complexity of the inflammatory network into consideration. Nonpharmacologic interventions, such as caloric restriction and exercise, may have significant impact on CLIP and its causative factors, leading to substantial health benefits. Metformin and resveratrol have anti-inflammatory property and may serve as a promising therapeutic agent for treatment of CLIP and frailty.

IMPLICATIONS

CLIP is a chronic inflammatory pathophysiologic process that plays an important role in the pathogenesis of frailty and many other chronic conditions. Improving our understanding of this phenotype may provide opportunities to identify potential targets of effective prevention and therapeutic strategies for frailty and other CLIP-associated conditions.

Cellular Senescence, Neurological Function, and Redox State

SIGNIFICANCE

Cellular senescence, characterized by permanent cell cycle arrest, has been extensively studied in mitotic cells such as fibroblasts. However, senescent cells have also been observed in the brain. Even though it is recognized that cellular energetic metabolism and redox homeostasis are perturbed in the aged brain and neurodegenerative diseases (NDDs), it is still unknown which alterations in the overall physiology can stimulate cellular senescence induction and their relationship with the former events. Recent Advances: Recent findings have shown that during prolonged inflammatory and pathologic events, the blood-brain barrier could be compromised and immune cells might enter the brain; this fact along with the brain's high oxygen dependence might result in oxidative damage to macromolecules and therefore senescence induction. Thus, cellular senescence in different brain cell types is revised here.

CRITICAL ISSUES

Most information related to cellular senescence in the brain has been obtained from research in glial cells since it has been assumed that the senescent phenotype is a feature exclusive to mitotic cells. Nevertheless, neurons with senescence hallmarks have been observed in old mouse brains. Therefore, although this is a controversial topic in the field, here we summarize and integrate the observations from several studies and propose that neurons indeed senesce.

FUTURE DIRECTIONS

It is still unknown which alterations in the overall metabolism can stimulate senescence induction in the aged brain, what are the mechanisms and signaling pathways, and what is their relationship to NDD development. The understanding of these processes will expose new targets to intervene age-associated pathologies.-Antioxid. Redox Signal. 28, 1704-1723.

Sirtinol regulates the balance of Th17/Treg to prevent allograft rejection

BACKGROUND

Current immunosuppressive medications used after transplantation induce significant toxicity , and a new medication regimen is needed. Based on recent research, Sirt1 exerts a proinflammatory effect on the immune response. Sirtinol is a Sirt1 inhibitor, but its impact on allograft rejection and its molecular mechanisms of action have not yet been reported.

RESLUTS

In this study, we examined the effect of sirtinol on prolonging allograft survival in a mouse cervical heterotopic heart transplantation model. Based on an examination of the allograft, allografts from sirtinol-treated recipients show significantly lower levels of IL-17A expression and higher levels of Foxp3 expression. In vivo, sirtinol reduces the proportion of Th17 cells and increases the proportion of Treg cells in splenocytes from recipients. In vitro, sirtinol reduces the proportion of Th17 cells and decreases the expression of IL-17A and RORγt in an isolated CD4⁺ T cell population. Moreover, we identified synergistic effects of sirtinol and FK506 on prolonging allograft survival, and sirtinol synergizes with FK506 to promote Foxp3 expression.

CONCLUSION

Sirtinol, a Sirt1 inhibitor, may be a promising immunosuppressive drug to prevent the rejection reaction in combination with FK506.

Recent advances in CMV tropism, latency, and diagnosis during aging

Human cytomegalovirus (CMV) is one of the largest viruses known to cause human diseases. Chronic CMV infection, as defined by anti-CMV IgG serology, increases with age and is highly prevalent in older adults. It has complex biology with significant immunologic and health consequences. This article aims to summarize research findings presented at the 6th International Workshop on CMV and Immunosenescence that relate to advances in the areas of CMV tropism, latency, CMV manipulation of cell metabolism, and T cell memory inflation, as well as novel diagnostic evaluation and translational research of chronic CMV infection in older adults. Information summarized here represents the current state of knowledge in these important fields. Investigators have also identified a number of areas that deserve further and more in-depth investigation, including building more precise parallels between mouse CMV (mCMV) and human CMV (HCMV) research. It is hoped that this article will also stimulate engaging discussion on strategies and direction to advance the science to the next level.

Up-regulation of nuclear factor E2-related factor 2 (Nrf2) represses the replication of SVCV

Generation of reactive oxygen species (ROS) and failure to maintain an appropriate redox balance contribute to viral pathogenesis. Nuclear factor E2-related factor 2 (Nrf2) is an important transcription factor that plays a pivotal role in maintaining intracellular homoeostasis and coping with invasive pathogens by coordinately activating a series of cytoprotective genes. Previous studies indicated that the transcription and expression levels of Nrf2 were up-regulated in SVCV-infected EPC cells with the unknown mechanism(s). In this study, the interactions between the Nrf2-ARE signalling pathway and SVCV replication were investigated, which demonstrated that SVCV infection induced accumulation of ROS as well as protein carbonyl groups and 8-OHdG, accompanied by the up-regulation of Nrf2 and its downstream genes. At the same time, the activation of Nrf2 with D, l-sulforaphane (SFN) and CDDO-Me could repress the replication of SVCV, and knockdown of Nrf2 by siRNA could promote the replication of SVCV. Taken together, these observations indicate that the Nrf2-ARE signal pathway activates a passive defensive response upon SVCV infection. The conclusions presented here suggest that targeting the Nrf2 pathway has potential for combating SVCV infection.