Virus Control of Cell Metabolism for Replication and Evasion of Host Immune Responses

Enterovirus A71-induced glycolysis is essential for viral replication by activating PI3K/Akt pathway

Enterovirus A71 (EV-A71), an obligate intracellular acellular microbe, depends entirely on host cellular metabolism to accomplish viral replication. Glycolysis is a glucose metabolic pathway that generates adenosine triphosphate (ATP) and other intermediates that activate other metabolic pathways. However, the role of glycolysis in EV-A71 replication remains unknown. In this study, we systematically investigated the role and regulation of glycolysis in human tonsillar epithelial cells (HTECs) during EV-A71 infection. Concentration of glucose was decreased, the glucose-6-phosphate (G6P) level and lactate production were increased with upregulating the glucose transporter1 (Glut1) expression in EV-A71-infected HTECs. Moreover, cellular metabolism, including glycolysis, pentose phosphate pathway (PPP), tricarboxylic acid (TCA) cycle, and cellular respiration were activated. PI3K/Akt pathway was also activated by EV-A71. Concentration of glucose was significantly increased but concentrations of G6P and lactate were significantly decreased along with decreased Glut1 protein level, and EV-A71 replication was also significantly suppressed when the glycolysis was inhibited by 2-deoxy-D-glucose (2DG) and sodium oxamate (Oxamate) treatments. A time-of-addition assay revealed that glycolysis regulated EV-A71 replication at the early (attachment/entry) and late (release) stages of the EV-A71 life cycle. Addition of glucose or lactate experiments showed too low or too high concentrations of glucose and excessive lactate impaired EV-A71 replication by decreasing Glut1 expression to inhibit glycolysis. Inhibition of oxidative phosphorylation (OXPHOS) also decreased EV-A71 replication. Finally, PI3K/Akt pathway inhibition severely reduced EV-A71 replication and G6P production. Therefore, these findings indicate that EV-A71 alters the host cellular metabolism to facilitate viral replication by exploiting glycolysis via the PI3K/Akt pathway, thereby providing a novel insight into the interaction between EV-A71 and host cells.

Arctigenin derivative TZOA restores mitochondrial homeostasis to combat rhabdovirus infections

Rhabdoviruses are diverse pathogens known for their broad host range and significant economic and health impacts. Infectious hematopoietic necrosis virus (IHNV), a member of the Novirhabdovirus genus, poses a major threat to aquaculture, particularly affecting rainbow trout. In this study, we further optimize the antiviral properties of arctigenin derivatives based on our previous structure-activity relationship (SAR) research, leading to the synthesis of TZOA. TZOA was synthesized with a 45 % yield and demonstrated no cytotoxicity up to 25 μM in EPC cells. Treatment with TZOA markedly inhibited IHNV replication dose-dependently, achieving over 90 % suppression of viral N, G, and M genes at 25 μM. Notably, TZOA effectively reduced viral titers compared to controls, demonstrating its potent antiviral activity in vitro. Mechanistically, TZOA preserved mitochondrial integrity, mitigated virus-induced mitochondrial fragmentation, and maintained membrane potential in infected cells. Furthermore, TZOA facilitated mitochondrial fusion and mitophagy, clearing damaged mitochondria, which restored MAVS-mediated interferon expression, thus enhancing the host's innate antiviral response. In vivo studies in juvenile rainbow trout revealed a significant 44 % increase in survival rates with TZOA treatment, accompanied by reduced IHNV-induced mortality and viral gene expression in spleen and kidney tissues. Importantly, TZOA also inhibited IHNV horizontal transmission, highlighting its potential application in controlling viral spread. These findings emphasize TZOA as a promising therapeutic candidate, not only for IHNV but also for broader rhabdovirus infections, offering valuable insights for antiviral drug development in aquaculture and beyond.

Metabolic Profiling Reveals Potential Prognostic Biomarkers for SFTS: Insights into Disease Severity and Clinical Outcomes

Background/Objectives: Severe fever with thrombocytopenia syndrome (SFTS) is a viral infection primarily found in Asia, with a case fatality rate of about 10%. Despite its increasing prevalence, the underlying pathogenic mechanisms remain poorly understood, limiting the development of effective therapeutic interventions. Methods: We employed an untargeted metabolomics approach using liquid chromatography-mass spectrometry (LC-MS) to analyze serum samples from 78 SFTS patients during the acute phase of their illness. Differential metabolic features between survival and fatal cases were identified through multivariate statistical analysis. Furthermore, we constructed a metabolic prognostic model based on these biomarkers to predict disease severity. Results: Significant alterations were observed in four key metabolic pathways: sphingolipid metabolism, biosynthesis of phenylalanine, tyrosine, and tryptophan, primary bile acid biosynthesis, and phenylalanine metabolism. Elevated levels of phenyllactic acid and isocitric acid were strongly associated with adverse outcomes and demonstrated high discriminatory power in distinguishing fatal cases from survivors. The metabolic prognostic model incorporating these biomarkers achieved a sensitivity of 75% and a specificity of 90% in predicting disease severity. Conclusions: Our findings highlight the pivotal role of metabolic dysregulation in the pathogenesis of SFTS and suggest that targeting specific metabolic pathways could open new avenues for therapeutic development. The identification of prognostic biomarkers provides a valuable tool for early risk stratification and timely clinical intervention, potentially improving patient outcomes.

Liquid-liquid phase separation in viral infection: From the occurrence and function to treatment potentials

Liquid-liquid phase separation (LLPS) of biomacromolecules, as a widespread cellular functional mechanism, is closely related to life processes, and is also commonly present in the lifecycle of viruses. Viral infection often leads to the recombination and redistribution of intracellular components to form biomacromolecule condensates assembled from viral replication-related proteins and intracellular components, which plays an important role in the process of viral infection. In this review, the key and influencing factors of LLPS are generalized, which mainly depend on various molecular interactions and environmental conditions in solution. Meanwhile, some examples of viruses utilizing LLPS are summarized, which are conducive to further understanding the subtle and complex biological regulatory processes between phase condensation and viruses. Finally, some representative antiviral drugs targeting phase separation that have been discovered are also outlined. In conclusion, in-depth study of the role of LLPS in viral infection is helpful to understand the mechanisms of virus-related diseases from a new perspective, and also provide a new therapeutic strategy for future treatments.

Mechanisms of HAHV-1 Interaction with Hemocytes in Haliotis diversicolor supertexta: An In Vitro Study

Haliotid herpesvirus 1 (HAHV-1) causes significant damage to the abalone aquaculture industry. Knowledge of HAHV-1 invasion and host defense mechanisms is limited due to the lack of stable molluscan cell lines. The present study established an in vitro infection model of HAHV-1 using the primary suspension cultures of hemocytes from Haliotis diversicolor supertexta and Haliotis discus hannai. The cytopathic effects of HAHV-1 on adherent-cultured hemocytes of both species were also investigated. The HAHV-1 DNA loads were firstly monitored by means of quantitative PCR during the development of viral infection, and subsequently the mechanism of interaction between HAHV-1 and hemocytes was explored by means of a transcriptome analysis. H. diversicolor supertexta hemocytes exhibited a high degree of susceptibility to HAHV-1, with viral loads reaching a peak of 4.0 × 10⁷ copies/ng DNA. In contrast, no significant replication was observed in H. discus hannai hemocytes. Transcriptome analysis revealed that HAHV-1 evades the host immune response in the early stages of infection, and hijacks the host's energy and redox metabolism to promote its replication at the late stages. Consequently, this study provides a valuable reference point for the investigation of virus-host interaction between HAHV-1 and abalone in vitro.

Itaconate facilitates viral infection via alkylating GDI2 and retaining Rab GTPase on the membrane

Metabolic reprogramming of host cells plays critical roles during viral infection. Itaconate, a metabolite produced from cis-aconitate in the tricarboxylic acid cycle (TCA) by immune responsive gene 1 (IRG1), is involved in regulating innate immune response and pathogen infection. However, its involvement in viral infection and underlying mechanisms remain incompletely understood. Here, we demonstrate that the IRG1-itaconate axis facilitates the infections of VSV and IAV in macrophages and epithelial cells via Rab GTPases redistribution. Mechanistically, itaconate promotes the retention of Rab GTPases on the membrane via directly alkylating Rab GDP dissociation inhibitor beta (GDI2), the latter of which extracts Rab GTPases from the membrane to the cytoplasm. Multiple alkylated residues by itaconate, including cysteines 203, 335, and 414 on GDI2, were found to be important during viral infection. Additionally, this effect of itaconate needs an adequate distribution of Rab GTPases on the membrane, which relies on Rab geranylgeranyl transferase (GGTase-II)-mediated geranylgeranylation of Rab GTPases. The single-cell RNA sequencing data revealed high expression of IRG1 primarily in neutrophils during viral infection. Co-cultured and in vivo animal experiments demonstrated that itaconate produced by neutrophils plays a dominant role in promoting viral infection. Overall, our study reveals that neutrophils-derived itaconate facilitates viral infection via redistribution of Rab GTPases, suggesting potential targets for antiviral therapy.

Elevated serum mtDNA in COVID-19 patients is linked to SARS-CoV-2 envelope protein targeting mitochondrial VDAC1, inducing apoptosis and mtDNA release

Mitochondria dysfunction is implicated in cell death, inflammation, and autoimmunity. During viral infections, some viruses employ different strategies to disrupt mitochondria-dependent apoptosis, while others, including SARS-CoV-2, induce host cell apoptosis to facilitate replication and immune system modulation. Given mitochondrial DNAs (mtDNA) role as a pro-inflammatory damage-associated molecular pattern in inflammatory diseases, we examined its levels in the serum of COVID-19 patients and found it to be high relative to levels in healthy donors. Furthermore, comparison of serum protein profiles between healthy individuals and SARS-CoV-2-infected patients revealed unique bands in the COVID-19 patients. Using mass spectroscopy, we identified over 15 proteins, whose levels in the serum of COVID-19 patients were 4- to 780-fold higher. As mtDNA release from the mitochondria is mediated by the oligomeric form of the mitochondrial-gatekeeper-the voltage-dependent anion-selective channel 1 (VDAC1)-we investigated whether SARS-CoV-2 protein alters VDAC1 expression. Among the three selected SARS-CoV-2 proteins, small envelope (E), nucleocapsid (N), and accessory 3b proteins, the E-protein induced VDAC1 overexpression, VDAC1 oligomerization, cell death, and mtDNA release. Additionally, this protein led to mitochondrial dysfunction, as evidenced by increased mitochondrial ROS production and cytosolic Ca2+ levels. These findings suggest that SARS-CoV-2 E-protein induces mitochondrial dysfunction, apoptosis, and mtDNA release via VDAC1 modulation. mtDNA that accumulates in the blood activates the cGAS-STING pathway, triggering inflammatory cytokine and chemokine expression that contribute to the cytokine storm and tissue damage seen in cases of severe COVID-19.

The tyrosine kinase Yes1 is a druggable host factor of HEV

BACKGROUND

HEV is a positive-sense, single-stranded RNA virus of the Hepeviridae family. Although HEV accounts for more than 3 million symptomatic cases of viral hepatitis per year, specific anti-HEV therapy and knowledge about HEV pathogenesis are scarce.

METHODS

To gain a deeper understanding of the HEV infectious cycle and guide the development of novel antiviral strategies, we here used an RNAi mini screen targeting a selection of kinases, including mitogen-activated protein kinases, receptor tyrosine kinases, and Src-family kinases. Further, we used state-of-the-art HEV infection models, including primary human hepatocytes and athymic nude rats.

RESULTS

Upon knockdown of the Src-family kinase Yes1, a significant reduction of HEV susceptibility could be observed, suggesting an important role of Yes1 in the HEV infectious cycle. Selective inhibition of Yes1 kinase activity resulted in significant inhibition of HEV infection in hepatoma cells and primary human hepatocytes, as well as in a rat HEV in vivo model system. Subsequent analysis of Y1KI during the HEV infectious life cycle indicated a role of Yes1 kinase activity in the early onset of HEV infection.

CONCLUSIONS

We identified the dependence of HEV on Yes1 signaling, which may contribute to the so far scarce knowledge of HEV's pathogenesis in the future. Moreover, we provide Y1KI as a novel antiviral drug candidate specifically targeting an HEV host factor.

Viral reprogramming by nervous necrosis virus alters key metabolites and its pathways in sevenband grouper (Hyporthodus septemfasciatus) gills

Nervous necrosis virus (NNV) which mainly infects sevenband grouper (Hyporthodus Septemfasciatus) is considered a potential threat to the grouper aquaculture industry. The gills being one of the portal of entry and an active site of replication of fish viruses emphasises its role as a key region to study the metabolomic changes caused by viral reprograming and hijacking of metabolic pathways associated with immunity of the host. In the present study, liquid chromatography mass spectrometry (LC-MS) was used to detect changes of endogenous compounds of the grouper after NNV infection. A total of 75 metabolites of ten different pathways were identified. The metabolites were mainly associated with fatty acids, lipids, amino acids and nucleotides. The virus reprogramming lead to the downregulation of majority of the metabolites in their pathways. Arachidonic acid (AA), tryptophan, kynurenine and methandriol were selected as representative metabolites and challenge studies with NNV confirmed the fact that, metabolites controlled the replication of virus in a dose dependent manner. Immune gene expression studies also confirmed the effect of metabolites by upregulated expression of interleukins, cytokines and TLRs which are part of cellular immune response. This study shows the viral reprogramming of NNV in grouper gill cells resulting in alterations in basic metabolic pathways associated with normal functioning of the organism.

Autophagy promotes replication of Bombyx mori Nucleopolyhedrovirus in insect cells

BmNPV is a pathogen that infects silkworms exclusively. Although the interaction between BmNPV and the silkworm has been widely noticed and studied, its specific mechanism has still not been elucidated. In this study, we investigated whether BmNPV infection induces the onset of host cell autophagy to enhance viral replication. We observed a significant increase in double- or single-membrane vesicles and an accumulation of enhanced green fluorescent protein eGFP-ATG8 spots in virus-infected cells 72 h after BmNPV infection, accompanied by a conversion of ATG8 to ATG8-PE. In addition, we observed changes in the mitochondrial morphology of BmN cells after BmNPV infection by transmission electron microscopy. By detecting the mitochondrial membrane potential, we found that BmNPV infection resulted in the decrease of mitochondrial membrane potential, and that eGFP-ATG8 was able to co-localise with mitochondria after virus infection of the cells. Moreover, the use of drugs to regulate the occurrence of autophagy affects the replication of cellular BmNPV. Our data demonstrates that BmNPV infection induces host cell autophagy and leads to cellular mitochondrial damage, which in turn may lead to mitochondrial autophagy, and that BmNPV-induced host autophagy promotes its replication in cells. These findings will provide clues for further understanding of host-virus interactions.

Innate Immune Response to Monkeypox Virus Infection: Mechanisms and Immune Escape

BACKGROUND

The reemergence of monkeypox virus (Mpox, formerly monkeypox) in 2022 in non-endemic countries has raised significant concerns for global health due to its high transmissibility and mortality rate. A major challenge in combating Mpox is its ability to evade the host's innate immune system, the first line of defense against viral infections.

SUMMARY

Mpox encodes various proteins that interfere with key antiviral pathways and mechanisms, such as the nuclear factor kappa B signaling, cytokine production, complement and inflammasome activation, and chemokine binding. These proteins modulate the expression and function of innate immune mediators, such as interferons, interleukins, and Toll-like receptors, and impair the recruitment and activation of innate immune cells, such as natural killer cells. By suppressing or altering these innate immune responses, Mpox enhances its replication and infection in the host tissues and organs, leading to systemic inflammation, tissue damage, and organ failure.

KEY MESSAGES

This study reveals new insights into the molecular and cellular interactions between Mpox and the host's innate immune system. It identifies potential targets and strategies for antiviral interventions, highlighting the importance of understanding these interactions to develop effective treatments and improve global health responses to Mpox outbreaks.

Alphaherpesvirus manipulates retinoic acid metabolism for optimal replication

Retinoic acid (RA), derived from retinol (ROL), is integral to cell growth, differentiation, and organogenesis. It is known that RA can inhibit herpes simplex virus (HSV) replication, but the interactions between alphaherpesviruses and RA metabolism are unclear. Our present study revealed that alphaherpesvirus (HSV-1 and Pseudorabies virus, PRV) infections suppressed RA synthesis from ROL by activating P53, which increased retinol reductase 3 (DHRS3) expression-an enzyme that converts retinaldehyde back to ROL. This process depended on the virus-triggered DNA damage response, the degradation of class I histone deacetylases, and the subsequent hyperacetylation of histones H3 and H4. Counteracting DHRS3 or P53 enabled higher RA synthesis and reduced viral growth. RA enhanced antiviral defenses by promoting ABCA1- and ABCG1-mediated lipid efflux. Treatment with the retinoic acid receptor (RAR) agonist palovarotene protected mice from HSV-1 infection, thus providing a potential therapeutic strategy against viral infections.

Understanding lactate in the development of Hepatitis B virus-related hepatocellular carcinoma

Hepatitis B Virus (HBV) is a hepatotropic virus that can establish a persistent and chronic infection in humans. Chronic hepatitis B (CHB) infection is associated with an increased risk of hepatic decompensation, cirrhosis, and hepatocellular carcinoma (HCC). Lactate level, as the end product of glycolysis, plays a substantial role in metabolism beyond energy production. Emerging studies indicate that lactate is linked to patient mortality rates, and HBV increases overall glucose consumption and lactate production in hepatocytes. Excessive lactate plays a role in regulating the tumor microenvironment (TME), immune cell function, autophagy, and epigenetic reprogramming. The purpose of this review is to gather and summarize the existing knowledge of the lactate's functions in the dysregulation of the immune system, which can play a crucial role in the development of HBV-related HCC. Therefore, it is reasonable to hypothesize that lactate with intriguing functions can be considered an immunomodulatory metabolite in immunotherapy.

Deciphering the similarities and disparities of molecular mechanisms behind respiratory epithelium response to HCoV-229E and SARS-CoV-2 and drug repurposing, a systems biology approach

PURPOSE

Identifying the molecular mechanisms behind SARS-CoV-2 disparities and similarities will help find new treatments. The present study determines networks' shared and non-shared (specific) crucial elements in response to HCoV-229E and SARS-CoV-2 viruses to recommend candidate medications.

METHODS

We retrieved the omics data on respiratory cells infected with HCoV-229E and SARS-CoV-2, constructed PPIN and GRN, and detected clusters and motifs. Using a drug-gene interaction network, we determined the similarities and disparities of mechanisms behind their host response and drug-repurposed.

RESULTS

CXCL1, KLHL21, SMAD3, HIF1A, and STAT1 were the shared DEGs between both viruses' protein-protein interaction network (PPIN) and gene regulatory network (GRN). The NPM1 was a specific critical node for HCoV-229E and was a Hub-Bottleneck shared between PPI and GRN in HCoV-229E. The HLA-F, ADCY5, TRIM14, RPF1, and FGA were the seed proteins in subnetworks of the SARS-CoV-2 PPI network, and HSPA1A and RPL26 proteins were the seed in subnetworks of the PPI network of HCOV-229E. TRIM14, STAT2, and HLA-F played the same role for SARS-CoV-2. Top enriched KEGG pathways included cell cycle and proteasome in HCoV-229E and RIG-I-like receptor, Chemokine, Cytokine-cytokine, NOD-like receptor, and TNF signaling pathways in SARS-CoV-2. We suggest some candidate medications for COVID-19 patient lungs, including Noscapine, Isoetharine mesylate, Cycloserine, Ethamsylate, Cetylpyridinium, Tretinoin, Ixazomib, Vorinostat, Venetoclax, Vorinostat, Ixazomib, Venetoclax, and epoetin alfa for further in-vitro and in-vivo investigations.

CONCLUSION

We suggested CXCL1, KLHL21, SMAD3, HIF1A, and STAT1, ADCY5, TRIM14, RPF1, and FGA, STAT2, and HLA-F as critical genes and Cetylpyridinium, Cycloserine, Noscapine, Ethamsylate, Epoetin alfa, Isoetharine mesylate, Ribavirin, and Tretinoin drugs to study further their importance in treating COVID-19 lung complications.

Comprehensive transcriptomic and metabolomic analysis of porcine intestinal epithelial cells after PDCoV infection

Introduction

Porcine deltacoronavirus (PDCoV), an emerging swine enteropathogenic coronavirus with worldwide distribution, mainly infects newborn piglets with severe diarrhea, vomiting, dehydration, and even death, causing huge economic losses to the pig industry. However, the underlying pathogenic mechanisms of PDCoV infection and the effects of PDCoV infection on host transcripts and metabolites remain incompletely understood.

Methods

This study investigated a combined transcriptomic and metabolomic analysis of porcine intestinal epithelial cells (IPEC-J2) following PDCoV infection by LC/MS and RNA-seq techniques. A total of 1,401 differentially expressed genes and 254 differentially accumulated metabolites were detected in the comparison group of PDCoV-infected vs. mock-infected.

Results and discussion

We found that PDCoV infection regulates gene sets associated with multiple signaling pathways, including the neuroactive ligand-receptor interaction, cytokine-cytokine receptor interaction, MAPK signaling pathway, chemokine signaling pathway, ras signaling pathway and so on. Besides, the metabolomic results showed that biosynthesis of cofactors, nucleotide metabolism, protein digestion and absorption, and biosynthesis of amino acid were involved in PDCoV infection. Moreover, integrated transcriptomics and metabolomics analyses revealed the involvement of ferroptosis in PDCoV infection, and exogenous addition of the ferroptosis activator erastin significantly inhibited PDCoV replication. Overall, these unique transcriptional and metabolic reprogramming features may provide a better understanding of PDCoV-infected IPEC-J2 cells and potential targets for antiviral treatment.

Polygonum cillinerve polysaccharide inhibits transmissible gastroenteritis virus by regulating microRNA-181

Transmissible gastroenteritis virus (TGEV) is an important pathogen capable of altering the expression profile of cellular miRNA. In this study, the potential of Polygonum cillinerve polysaccharide (PCP) to treat TGEV-infected piglets was evaluated through in vivo experiments. High-throughput sequencing technology was employed to identify 9 up-regulated and 17 down-regulated miRNAs during PCP-mediated inhibition of TGEV infection in PK15 cells. Additionally, miR-181 was found to be associated with target genes of key proteins in the apoptosis pathway. PK15 cells were treated with various concentrations of PCP following transfection with miR-181 mimic or inhibitor. Real-time PCR assessed the impact on TGEV replication, while electron microscopy (TEM) and Hoechst fluorescence staining evaluated cellular functionality. Western blot analysis was utilized to assess the expression of key signaling factors-cytochrome C (cyt C), caspase 9, and P53-in the apoptotic signaling pathway. The results showed that compared with the control group, 250 μg/mL PCP significantly inhibited TGEV gRNA replication and gene N expression (P < 0.01). Microscopic examination revealed uniform cell morphology and fewer floating cells in PCP-treated groups (250 and 125 μg/mL). TEM analysis showed no typical virus structure in the 250 μg/mL PCP group, and apoptosis staining indicated a significant reduction in apoptotic cells at this concentration. Furthermore, PCP may inhibit TGEV-induced apoptosis via the Caspase-dependent mitochondrial pathway following miR-181 transfection. These findings provide a theoretical basis for further exploration into the mechanism of PCP's anti-TGEV properties.

Human muscle cells sensitivity to chikungunya virus infection relies on their glycolysis activity and differentiation stage

Changes to our environment have led to the emergence of human pathogens such as chikungunya virus. Chikungunya virus infection is today a major public health concern. It is a debilitating chronic disease impeding patients' mobility, affecting millions of people. Disease development relies on skeletal muscle infection. The importance of skeletal muscle in chikungunya virus infection led to the hypothesis that it could serve as a viral reservoir and could participate to virus persistence. Here we questioned the interconnection between skeletal muscle cells metabolism, their differentiation stage and the infectivity of the chikungunya virus. We infected human skeletal muscle stem cells at different stages of differentiation with chikungunya virus to study the impact of their metabolism on virus production and inversely the impact of virus on cell metabolism. We observed that chikungunya virus infectivity is cell differentiation and metabolism-dependent. Chikungunya virus interferes with the cellular metabolism in quiescent undifferentiated and proliferative muscle cells. Moreover, activation of chikungunya infected quiescent muscle stem cells, induces their proliferation, increases glycolysis and amplifies virus production. Therefore, our results showed that Chikungunya virus infectivity and the antiviral response of skeletal muscle cells relies on their energetic metabolism and their differentiation stage. Then, muscle stem cells could serve as viral reservoir producing virus after their activation.

Modulation of nucleotide metabolism by picornaviruses

Viruses actively reprogram the metabolism of the host to ensure the availability of sufficient building blocks for virus replication and spreading. However, relatively little is known about how picornaviruses-a large family of small, non-enveloped positive-strand RNA viruses-modulate cellular metabolism for their own benefit. Here, we studied the modulation of host metabolism by coxsackievirus B3 (CVB3), a member of the enterovirus genus, and encephalomyocarditis virus (EMCV), a member of the cardiovirus genus, using steady-state as well as 13C-glucose tracing metabolomics. We demonstrate that both CVB3 and EMCV increase the levels of pyrimidine and purine metabolites and provide evidence that this increase is mediated through degradation of nucleic acids and nucleotide recycling, rather than upregulation of de novo synthesis. Finally, by integrating our metabolomics data with a previously acquired phosphoproteomics dataset of CVB3-infected cells, we identify alterations in phosphorylation status of key enzymes involved in nucleotide metabolism, providing insight into the regulation of nucleotide metabolism during infection.

Viroporins Manipulate Cellular Powerhouses and Modulate Innate Immunity

Viruses have a wide repertoire of molecular strategies that focus on their replication or the facilitation of different stages of the viral cycle. One of these strategies is mediated by the activity of viroporins, which are multifunctional viral proteins that, upon oligomerization, exhibit ion channel properties with mild ion selectivity. Viroporins facilitate multiple processes, such as the regulation of immune response and inflammasome activation through the induction of pore formation in various cell organelle membranes to facilitate the escape of ions and the alteration of intracellular homeostasis. Viroporins target diverse membranes (such as the cellular membrane), endoplasmic reticulum, and mitochondria. Cumulative data regarding the importance of mitochondria function in multiple processes, such as cellular metabolism, energy production, calcium homeostasis, apoptosis, and mitophagy, have been reported. The direct or indirect interaction of viroporins with mitochondria and how this interaction affects the functioning of mitochondrial cells in the innate immunity of host cells against viruses remains unclear. A better understanding of the viroporin-mitochondria interactions will provide insights into their role in affecting host immune signaling through the mitochondria. Thus, in this review, we mainly focus on descriptions of viroporins and studies that have provided insights into the role of viroporins in hijacked mitochondria.

Lactate-lactylation-HSPA6 axis promotes PRRSV replication by impairing IFN-β production

Lactate, traditionally considered a metabolic by-product, has recently been identified as a substrate for the induction of lactylation, a newly identified epigenetic modification that plays an important role in the regulation of host gene expression. Our previous study showed that lactate levels were significantly elevated in cells infected with the porcine reproductive and respiratory syndrome virus (PRRSV), an Arterivirus that has devastated the swine industry worldwide for over 30 years. However, the role of elevated lactate in PRRSV infections remains unknown. In this study, we found that lactate was required for optimal PRRSV proliferation, and PRRSV infection increased cellular lactylation in a dose-dependent manner. Using the Cleavage Under Targets and Tagmentation (CUT&Tag) combined with RNA sequencing (RNA-seq) to screen the downstream genes regulated by lactylation in PRRSV-infected cells, we found that PRRSV-induced lactylation activated the expression of heat shock 70 kDa protein 6 (HSPA6). Follow-up experiments showed that HSPA6 is important for PRRSV proliferation by negatively modulating interferon (IFN)-β induction. Mechanistically, HSPA6 impeded the interaction between TNF-receptor-associated factor 3 (TRAF3) and inhibitor of nuclear factor kappa-B kinase subunit epsilon (IKKε), thereby hindering the production of IFN-β. Taken together, these results indicate that the activated lactate-lactylation-HSPA6 axis promotes viral growth by impairing IFN-β induction, providing new therapeutic targets for the prevention and control of PRRSV infection. The results presented here also link lactylation to the virus life cycle, improving our understanding of epigenetic regulation in viral infection.IMPORTANCEAs a newly identified epigenetic modification, lactate-induced lactylation has received attentions because it plays important roles in gene expression and contributes to tumorigenesis and the innate immune response. Previous studies showed that many viruses upregulate cellular lactate levels; however, whether virus-elevated lactate induces lactylation and the subsequent biological significance of the modification to viral infection have not been reported. In this study, we demonstrated that porcine reproductive and respiratory syndrome virus (PRRSV) infection induced cellular lactylation, which, in turn, upregulated the expression of HSPA6, an IFN-negative regulator. We also dissected the mechanism by which HSPA6 negatively regulates IFN-β production. To our knowledge, this is the first report to study virus-induced lactylation and establish the relationship between lactylation and virus infection.

Paraoxonase 1 rs662 polymorphism, its related variables, and COVID-19 intensity: Considering gender and post-COVID complications

In this study, we aimed to investigate the effect of paraoxonase 1 (PON1) rs662 polymorphism, arylesterase (ARE) activity, and the serum lipid profile in patients with coronavirus disease 2019 (COVID-19) in different stages of the disease considering post-COVID outcomes. A total of 470 COVID-19 patients (235 female and 235 male patients) were recruited into the study, and based on the World Health Organization (WHO) criteria, the patients were divided into three groups: moderate, severe, and critical. PON1 rs662 polymorphism was determined by the Alw 1 enzyme followed by agarose gel electrophoresis. Moreover, serum levels of triglycerides (TG), cholesterol (Chol), high-density lipoprotein-cholesterol (HDL-c), and low-density lipoprotein-cholesterol (LDL-c), as well as the level of the ARE activity of PON1 in the sera of patients were measured at the time of infection and one and three months after hospitalization. There was a significant relationship between the G allele and the severity of the disease. In addition, the probability of death in homozygous individuals (GG) was higher than in heterozygous patients (GA), and it was higher in heterozygous patients than in wild-type individuals (AA). There was also a significant relationship between the decrease in serum lipids and the intensity of COVID-19. On the contrary, at the onset of the disease, the HDL-c level and serum ARE activity were reduced compared to one and three months after COVID-19 infection. The findings of this study indicated the significant impact of PON1 rs662 polymorphism on ARE activity, lipid profiles, disease severity, and mortality in COVID-19 patients.

Zika virus infection induces expression of NRF2 and antioxidant systems in trophoblast cells

The nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that plays a critical role in the xenobiotic and stress responses. During viral infection, NRF2 can modulate the host metabolism and innate immunity; however, the most common activity of NRF2 in viral diseases is controlling reactive oxygen species (ROS). The Zika virus (ZIKV) is involved in a vertical infection in pregnancy, with reported fetal health consequences. However, the possibility that ZIKV regulates NRF2 expression in placental trophoblasts has not been investigated. In this report, we evaluated the upregulation of NRF2 and antioxidant enzymes in a trophoblast-like cell. These findings could help us understand the antioxidant mechanism underlying the ZIKV infection in the placenta during pregnancy.

The severity of SARS-CoV-2 infection in K18-hACE2 mice is attenuated by a novel steroid-derivative in a gender-specific manner

BACKGROUND AND PURPOSE

COVID-19 infections caused by SARS-CoV-2 disseminated through human-to-human transmission can evoke severe inflammation. Treatments to reduce the SARS-CoV-2-associated inflammation are needed and are the focus of much research. In this study, we investigated the effect of N-ethyl-N'-[(3β,5α)-17-oxoandrostan-3-yl] urea (NEOU), a novel 17α-ketosteroid derivative, on the severity of COVID-19 infections.

EXPERIMENTAL APPROACH

Studies were conducted in SARS-CoV-2-infected K18-hACE2 mice.

KEY RESULTS

SARS-CoV-2-infected K18-hACE2 mice developed severe inflammatory crises and immune responses along with up-regulation of genes in associated signalling pathways in male more than female mice. Notably, SARS-CoV-2 infection down-regulated genes encoding drug metabolizing cytochrome P450 enzymes in male but not female mice. Treatment with NEOU (1 mg·kg-1 ·day-1 ) 24 or 72 h post-viral infection alleviated lung injury by decreasing expression of genes encoding inflammatory cytokines and chemokines while increasing expression of genes encoding immunoglobins. In situ hybridization using RNA scope™ probes and immunohistochemical assays revealed that NEOU increased resident CD169+ immunoregulatory macrophages and IBA-1 immunoreactive macrophage-dendritic cells within alveolar spaces in the lungs of infected mice. Consequentially, NEOU reduced morbidity more prominently in male than female mice. However, NEOU increased median survival time and accelerated recovery from infection by 6 days in both males and females.

CONCLUSIONS AND IMPLICATIONS

These findings demonstrate that SARS-CoV-2 exhibits gender bias by differentially regulating genes encoding inflammatory cytokines, immunogenic factors and drug-metabolizing enzymes, in male versus female mice. Most importantly, we identified a novel 17α-ketosteroid that reduces the severity of COVID-19 infection and could be beneficial for reducing impact of COVID-19.

Rhinovirus C causes heterogeneous infection and gene expression in airway epithelial cell subsets

Rhinoviruses infect ciliated airway epithelial cells, and rhinoviruses' nonstructural proteins quickly inhibit and divert cellular processes for viral replication. However, the epithelium can mount a robust innate antiviral immune response. Therefore, we hypothesized that uninfected cells contribute significantly to the antiviral immune response in the airway epithelium. Using single-cell RNA sequencing, we demonstrate that both infected and uninfected cells upregulate antiviral genes (e.g. MX1, IFIT2, IFIH1, and OAS3) with nearly identical kinetics, whereas uninfected non-ciliated cells are the primary source of proinflammatory chemokines. Furthermore, we identified a subset of highly infectable ciliated epithelial cells with minimal interferon responses and determined that interferon responses originate from distinct subsets of ciliated cells with moderate viral replication. These findings suggest that the composition of ciliated airway epithelial cells and coordinated responses of infected and uninfected cells could determine the risk of more severe viral respiratory illnesses in children with asthma, chronic obstructive pulmonary disease, and genetically susceptible individuals.

Cellular metabolism hijacked by viruses for immunoevasion: potential antiviral targets

Cellular metabolism plays a central role in the regulation of both innate and adaptive immunity. Immune cells utilize metabolic pathways to modulate the cellular differentiation or death. The intricate interplay between metabolism and immune response is critical for maintaining homeostasis and effective antiviral activities. In recent years, immunometabolism induced by viral infections has been extensively investigated, and accumulating evidence has indicated that cellular metabolism can be hijacked to facilitate viral replication. Generally, virus-induced changes in cellular metabolism lead to the reprogramming of metabolites and metabolic enzymes in different pathways (glucose, lipid, and amino acid metabolism). Metabolic reprogramming affects the function of immune cells, regulates the expression of immune molecules and determines cell fate. Therefore, it is important to explore the effector molecules with immunomodulatory properties, including metabolites, metabolic enzymes, and other immunometabolism-related molecules as the antivirals. This review summarizes the relevant advances in the field of metabolic reprogramming induced by viral infections, providing novel insights for the development of antivirals.

Glycolytic interference blocks influenza A virus propagation by impairing viral polymerase-driven synthesis of genomic vRNA

Influenza A virus (IAV), like any other virus, provokes considerable modifications of its host cell's metabolism. This includes a substantial increase in the uptake as well as the metabolization of glucose. Although it is known for quite some time that suppression of glucose metabolism restricts virus replication, the exact molecular impact on the viral life cycle remained enigmatic so far. Using 2-deoxy-d-glucose (2-DG) we examined how well inhibition of glycolysis is tolerated by host cells and which step of the IAV life cycle is affected. We observed that effects induced by 2-DG are reversible and that cells can cope with relatively high concentrations of the inhibitor by compensating the loss of glycolytic activity by upregulating other metabolic pathways. Moreover, mass spectrometry data provided information on various metabolic modifications induced by either the virus or agents interfering with glycolysis. In the presence of 2-DG viral titers were significantly reduced in a dose-dependent manner. The supplementation of direct or indirect glycolysis metabolites led to a partial or almost complete reversion of the inhibitory effect of 2-DG on viral growth and demonstrated that indeed the inhibition of glycolysis and not of N-linked glycosylation was responsible for the observed phenotype. Importantly, we could show via conventional and strand-specific qPCR that the treatment with 2-DG led to a prolonged phase of viral mRNA synthesis while the accumulation of genomic vRNA was strongly reduced. At the same time, minigenome assays showed no signs of a general reduction of replicative capacity of the viral polymerase. Therefore, our data suggest that the significant reduction in IAV replication by glycolytic interference occurs mainly due to an impairment of the dynamic regulation of the viral polymerase which conveys the transition of the enzyme's function from transcription to replication.

Defects in intratumoral arginine metabolism attenuate the replication and therapeutic efficacy of oncolytic myxoma virus

BACKGROUND

Arginine (Arg) is a semiessential amino acid whose bioavailability is required for the in vitro replication of several oncolytic viruses. In vivo, Arg bioavailability is regulated by a combination of dietary intake, protein catabolism, and limited biosynthesis through portions of the urea cycle. Interestingly, despite the importance of bioavailable Arg to support cellular proliferation, many forms of cancer are functionally auxotrophic for this amino acid due to the epigenetic silencing of argininosuccinate synthetase 1 (ASS1), an enzyme responsible for the conversion of citrulline and aspartate into the Arg precursor argininosuccinate. The impact of this silencing on oncolytic virotherapy (OV), however, has never been examined.

METHODS

To address this gap in knowledge, we generated tumor cells lacking ASS1 and examined how loss of this enzyme impacted the in vivo replication and therapeutic efficacy of oncolytic myxoma virus (MYXV). We also generated a series of recombinant MYXV constructs expressing exogenous ASS1 to evaluate the therapeutic benefit of virally reconstituting Arg biosynthesis in ASS1-/- tumors.

RESULTS

Our results show that the in vitro replication of oncolytic MYXV is dependent on the presence of bioavailable Arg. This dependence can be overcome by the addition of the metabolic precursor citrulline, however, this rescue requires expression of ASS1. Because of this, tumors formed from functionally ASS1-/- cells display significantly reduced MYXV replication as well as poorer therapeutic responses. Critically, both defects could be partially rescued by expressing exogenous ASS1 from recombinant oncolytic MYXVs.

CONCLUSIONS

These results demonstrate that intratumoral defects to Arg metabolism can serve as a novel barrier to virally induced immunotherapy and that the exogenous expression of ASS1 can improve the efficacy of OV in Arg-auxotrophic tumors.

HIV-Differentiated Metabolite N-Acetyl-L-Alanine Dysregulates Human Natural Killer Cell Responses to Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) has latently infected over two billion people worldwide (LTBI) and caused ~1.6 million deaths in 2021. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared with HIV- LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals. Plasma samples collected from healthy and HIV-infected individuals were investigated using liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using the online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, and quantitative reverse-transcription PCR (qRT-PCR) were performed using standard procedures to determine the surface markers, cytokines, and other signaling molecule expressions. Seahorse extra-cellular flux assays were used to measure mitochondrial oxidative phosphorylation and glycolysis. Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared with healthy donors. One of the HIV-upregulated metabolites, N-acetyl-L-alanine (ALA), inhibits pro-inflammatory cytokine IFN-γ production by the NK cells of LTBI+ individuals. ALA inhibits the glycolysis of LTBI+ individuals' NK cells in response to Mtb. Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK-cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV-Mtb interaction and providing insights into the implication of nutrition intervention and therapy for HIV-Mtb co-infected patients.

RHDV 3C protein antagonizes type I interferon signaling by cleaving interferon promoter stimulated 1 protein

The host innate immune response to viral infection often involves the activation of type I interferons. Not surprisingly, many viruses have evolved various mechanisms to disable the interferon pathway and evade the antiviral response involving innate immunity. Rabbit hemorrhagic disease (RHD) is caused by RHD virus (RHDV), but whether it can antagonize the production of host interferon to establish infection has not been investigated. In this study, we found that during RHDV infection, the expressions of interferon and the interferon-stimulated gene were not activated. We constructed eukaryotic expression plasmids of all RHDV proteins, and found that RHDV 3C protein inhibited poly(I:C)-induced interferon expressions. Using siRNA to interfere with the expressions of TLR3 and MDA5, we found that the MDA5 signal pathway was used by the 3C protein to inhibit poly(I:C)-induced interferon expression. This effect was mediated by cleaving the interferon promoter stimulated 1 (IPS-1) protein. Finally, our study showed that interferon was effective against RHDV infection. In summary, our findings showed that the RHDV 3C protein was a new interferon antagonist. These results increase our understanding of the escape mechanism from innate immunity mediated by the RHDV 3C protein.

Role of asparagine biosynthesis pathway in Siniperca chuatsi rhabdovirus proliferation

Viruses are non-living organisms that rely on host cellular metabolism to complete their life cycle. Siniperca chuatsi rhabdovirus (SCRV) has caused huge economic losses to the Chinese perch (Siniperca chuatsi) industry worldwide. SCRV replication is dependent on the cellular glutamine metabolism, while aspartate metabolism plays an important role in viral proliferation in glutamine deficiency. Herein, we investigated roles of asparagine metabolism in SCRV proliferation. Results showed that SCRV infection upregulated the expression of key enzymes in the aspartate metabolic pathway in CPB cells. And the key enzymes of malate-aspartic acid shuttle pathway upregulated during the virus invasion phase, and key enzymes of the asparagine biosynthesis pathway upregulated during the viral replication and release phase. When asparagine was added to the depleted medium, the SCRV copy number restored to 90% of those in replete medium, showing that asparagine and glutamine completely rescue the replication of SCRV. Moreover, inhibition of the aspartate- malate shuttle pathway and knockdown of the expression of key enzymes in the asparagine biosynthesis pathway significantly reduced SCRV production, indicating that the aspartic acid metabolic pathway was required to the replication and proliferation of SCRV. Above results provided references for elucidating pathogenic mechanism of SCRV by regulation of aspartate metabolism.

Analysis of temporal metabolic rewiring for human respiratory syncytial virus infection by integrating metabolomics and proteomics

INTRODUCTION

Human respiratory syncytial virus (HRSV) infection causes significant morbidity, and no effective treatments are currently available. Viral infections induce substantial metabolic changes in the infected cells to optimize viral production. Metabolites that reflect the interactions between host cells and viruses provided an opportunity to identify the pathways underlying severe infections.

OBJECTIVE

To better understand the metabolic changes caused by HRSV infection, we analyzed temporal metabolic profiling to provide novel targets for therapeutic strategies for inhaled HRSV infection.

METHODS

The epithelial cells and BALB/c mice were infected with HRSV. Protein and mRNA levels of inflammation factors were measured by using quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. Untargeted metabolomics, lipidomics and proteomics were performed using liquid chromatography coupled with mass spectrometry to profile the metabolic phenotypic alterations in HRSV infection.

RESULTS

In this study, we evaluated the inflammatory responses in vivo and in vitro and investigated the temporal metabolic rewiring of HRSV infection in epithelial cells. We combined metabolomics and proteomic analyses to demonstrate that the redox imbalance was further provoked by increasing glycolysis and anaplerotic reactions. These responses created an oxidant-rich microenvironment that elevated reactive oxygen species levels and exacerbated glutathione consumption.

CONCLUSION

These observations indicate that adjusting for metabolic events during a viral infection could represent a valuable approach for reshaping the outcome of infections.

Evaluation of differentially expressed genes during replication using gene expression landscape of monkeypox-infected MK2 cells: A bioinformatics and systems biology approach to understanding the genomic pattern of viral replication

PURPOSE

The current outbreak of monkeypox (MPX) has created colossal concerns. However, immense research gaps have been noted in our understanding of the replication process, machinery, and genomic landscape during host cell infection. To fill this gap, differentially expressed genes (DEGs) were comprehensively analyzed during viral replication in host (MK2) cells.

METHODS

We used a microarray GEO dataset which was divided into three groups: control, MPXV-infected MK2 cells at 3 h, and MPXV-infected MK2 cells at 7 h. Using the dataset, DEG analysis, PPI network analysis, co-expression, and pathway analysis were conducted using bioinformatics, systems biology, and statistical approaches.

RESULTS

We identified 250 DEGs and 24 top-ranked genes. During the DEG analysis, we identified eight up-regulated genes (LOC695323, TMEM107, LOC695427, HIST1H2AD, LOC705469, PMAIP1, HIST1H2BJ, and HIST1H3D) and 16 down-regulated genes (HOXA9, BAMBI, LMO4, PAX6, AJUBA, CREBRF, CD24, JADE1, SLC7A11, EID2, SOX4, B4GALT5, PPARGC1A, BUB3, SOS2, and CDK19). We also developed PPI networks and performed co-expression analyses using the top-ranked genes. Furthermore, five genes were listed for co-expression pattern analysis.

CONCLUSIONS

This study will help in better understanding the replication process, machinery, and genomic landscape of the virus. This will further aid the discovery and development of therapeutics against viruses.

HIV-differentiated metabolite N-Acetyl-L-Alanine dysregulates human natural killer cell responses to Mycobacterium tuberculosis infection

Background

Mycobacterium tuberculosis ( Mtb ) has latently infected over two billion people worldwide (LTBI) and causes 1.8 million deaths each year. Human immunodeficiency virus (HIV) co-infection with Mtb will affect the Mtb progression and increase the risk of developing active tuberculosis by 10-20 times compared to the HIV-LTBI+ patients. It is crucial to understand how HIV can dysregulate immune responses in LTBI+ individuals.

Methods

Plasma samples collected from healthy and HIV-infected individuals were investigated by liquid chromatography-mass spectrometry (LC-MS), and the metabolic data were analyzed using an online platform Metabo-Analyst. ELISA, surface and intracellular staining, flow cytometry, quantitative reverse transcription PCR (qRT-PCR) were performed by standard procedure to determine the surface markers, cytokines and other signaling molecule expression. Seahorse extra cellular flux assays were used to measure the mitochondrial oxidative phosphorylation and glycolysis.

Results

Six metabolites were significantly less abundant, and two were significantly higher in abundance in HIV+ individuals compared to healthy donors. One of the HIV-upregulated metabolites, N-Acetyl-L-Alanine (ALA), inhibits pro-inflammatory cytokine IFN-□ production by NK cells of LTBI+ individuals. ALA inhibits glycolysis of LTBI+ individuals' NK cells in response to Mtb .

Conclusions

Our findings demonstrate that HIV infection enhances plasma ALA levels to inhibit NK cell-mediated immune responses to Mtb infection, offering a new understanding of the HIV- Mtb interaction and providing the implication of nutrition intervention and therapy for HIV- Mtb co-infected patients.

After virus exposure, early bystander naïve CD8 T cell activation relies on NAD+ salvage metabolism

CD8 T cells play a central role in antiviral immunity. Type I interferons are among the earliest responders after virus exposure and can cause extensive reprogramming and antigen-independent bystander activation of CD8 T cells. Although bystander activation of pre-existing memory CD8 T cells is known to play an important role in host defense and immunopathology, its impact on naïve CD8 T cells remains underappreciated. Here we report that exposure to reovirus, both in vitro or in vivo, promotes bystander activation of naïve CD8 T cells within 24 hours and that this distinct subtype of CD8 T cell displays an innate, antiviral, type I interferon sensitized signature. The induction of bystander naïve CD8 T cells is STAT1 dependent and regulated through nicotinamide phosphoribosyl transferase (NAMPT)-mediated enzymatic actions within NAD+ salvage metabolic biosynthesis. These findings identify a novel aspect of CD8 T cell activation following virus infection with implications for human health and physiology.

Mushrooms as future generation healthy foods

The potential of edible mushrooms as an unexploited treasure trove, although rarely included in known food guidelines, is highlighted. Their role in shielding people against the side effects of an unhealthy stylish diet is reviewed. Mushrooms complement the human diet with various bioactive molecules not identified or deficient in foodstuffs of plant and animal sources, being considered a functional food for the prevention of several human diseases. Mushrooms have been widely used as medicinal products for more than 2,000 years, but globally the potential field of use of wild mushrooms has been untapped. There is a broad range of edible mushrooms which remain poorly identified or even unreported which is a valuable pool as sources of bioactive compounds for biopharma utilization and new dietary supplements. Some unique elements of mushrooms and their role in preventative healthcare are emphasized, through their positive impact on the immune system. The potential of mushrooms as antiviral, anti-inflammatory, anti-neoplastic, and other health concerns is discussed. Mushrooms incorporate top sources of non-digestible oligosaccharides, and ergothioneine, which humans are unable to synthesize, the later a unique antioxidant, cytoprotective, and anti-inflammatory element, with therapeutic potential, approved by world food agencies. The prebiotic activity of mushrooms beneficially affects gut homeostasis performance and the balance of gut microbiota is enhanced. Several recent studies on neurological impact and contribution to the growth of nerve and brain cells are mentioned. Indeed, mushrooms as functional foods' nutraceuticals are presently regarded as next-generation foods, supporting health and wellness, and are promising prophylactic or therapeutic agents.

Molecular and cellular mechanisms involved in tissue-specific metabolic modulation by SARS-CoV-2

Coronavirus disease 2019 (COVID-19) is triggered by the SARS-CoV-2, which is able to infect and cause dysfunction not only in lungs, but also in multiple organs, including central nervous system, skeletal muscle, kidneys, heart, liver, and intestine. Several metabolic disturbances are associated with cell damage or tissue injury, but the mechanisms involved are not yet fully elucidated. Some potential mechanisms involved in the COVID-19-induced tissue dysfunction are proposed, such as: (a) High expression and levels of proinflammatory cytokines, including TNF-α IL-6, IL-1β, INF-α and INF-β, increasing the systemic and tissue inflammatory state; (b) Induction of oxidative stress due to redox imbalance, resulting in cell injury or death induced by elevated production of reactive oxygen species; and (c) Deregulation of the renin-angiotensin-aldosterone system, exacerbating the inflammatory and oxidative stress responses. In this review, we discuss the main metabolic disturbances observed in different target tissues of SARS-CoV-2 and the potential mechanisms involved in these changes associated with the tissue dysfunction.

Metabolic reprogramming as a novel therapeutic target for Coxsackievirus B3

Coxsackievirus B3 (CVB3) is a single-stranded RNA virus that belongs to the Enterovirus genus. CVB3 is a human pathogen associated with serious conditions such as myocarditis, dilated cardiomyopathy, and pancreatitis. However, there are no therapeutic interventions to treat CVB3 infections. In this study, we found that CVB3 induced metabolic alteration in host cells through increasing glycolysis level, as indicated by an increase in the extracellular acidification rate (ECAR). CVB3-mediated metabolic alteration was confirmed by metabolite change analysis using gas chromatography-mass spectrometry (GC-MS). Based on findings, a strategy to inhibit glycolysis has been proposed to treat CVB3 infection. Indeed, glycolysis inhibitors (2-Deoxy-D-glucose, sodium oxide) significantly reduced CVB3 titers after CVB3 infection, indicating that glycolysis inhibitors can be used as effective antiviral agents. Taken together, our results reveal a novel mechanism by which CVB3 infection is controlled by regulation of host cell metabolism.

Interplay between cellular metabolism and DNA viruses

Viruses as intracellular pathogens take over the host metabolism and reprogram to facilitate optimal virus production. DNA viruses can cause alterations in several metabolic pathways, including aerobic glycolysis also known as the Warburg effect, pentose phosphate pathway activation, and amino acid catabolism such as glutaminolysis, nucleotide biosynthesis, lipid metabolism, and amino acid biosynthesis. The available energy for productive infection can be increased in infected cells via modification of different carbon source utilization. This review discusses the metabolic alterations of the DNA viruses that will be the basis for future novel therapeutic approaches.

The Efficient Antiviral Response of A549 Cells Is Enhanced When Mitochondrial Respiration Is Promoted

When exposed to a viral infection, the attacked cells promptly set up defense mechanisms. As part of the antiviral responses, the innate immune interferon pathway and associated interferon-stimulated genes notably allow the production of proteins bearing antiviral activity. Numerous viruses are able to evade the interferon response, highlighting the importance of controlling this pathway to ensure their efficient replication. Several viruses are also known to manipulate the metabolism of infected cells to optimize the availability of amino acids, nucleotides, and lipids. They then benefit from a reprogramming of the metabolism that favors glycolysis instead of mitochondrial respiration. Given the increasingly discussed crosstalk between metabolism and innate immunity, we wondered whether this switch from glycolysis to mitochondrial respiration would be beneficial or deleterious for an efficient antiviral response. We used a cell-based model of metabolic reprogramming. Interestingly, we showed that increased mitochondrial respiration was associated with an enhanced interferon response following polyriboinosinic:polyribocytidylic acid (poly:IC) stimulation. This suggests that during viral infection, the metabolic reprogramming towards glycolysis is also part of the virus’ strategies to inhibit the antiviral response.

Coronavirus disease 2019 (COVID-19) update: From metabolic reprogramming to immunometabolism

The field of immunometabolism investigates and describes the effects of metabolic rewiring in immune cells throughout activation and the fates of these cells. Recently, it has been appreciated that immunometabolism plays an essential role in the progression of viral infections, cancer, and autoimmune diseases. Regarding COVID-19, the aberrant immune response underlying the progression of diseases establishes two major respiratory pathologies, including acute respiratory distress syndrome (ARDS) or pneumonia-induced acute lung injury (ALI). Both innate and adaptive immunity (T cell-based) were impaired in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Current findings have deciphered that macrophages (innate immune cells) are involved in the inflammatory response seen in COVID-19. It has been demonstrated that immune system cells can change metabolic reprogramming in some conditions, including autoimmune diseases, cancer, and infectious disease, including COVID-19. The growing findings on metabolic reprogramming in COVID-19 allow an exploration of metabolites with immunomodulatory properties as future therapies to combat this hyperinflammatory response. The elucidation of the exact role and mechanism underlying this metabolic reprograming in immune cells could help apply more precise approaches to initial diagnosis, prognosis, and in-hospital therapy. This report discusses the latest findings from COVID-19 on host metabolic reprogramming and immunometabolic responses.

Ferroptosis in viral infection: the unexplored possibility

Virus-induced cell death has long been thought of as a double-edged sword in the inhibition or exacerbation of viral infections. The vital role of iron, an essential element for various enzymes in the maintenance of cellular physiology and efficient viral replication, places it at the crossroads and makes it a micronutrient of competition between the viruses and the host. Viruses can interrupt iron uptake and the antioxidant response system, while others can utilize iron transporter proteins as receptors. Interestingly, the unavailability of iron facilitates certain viral infections and causes cell death characterized by lipid peroxide accumulation and malfunction of the antioxidant system. In this review, we discuss how iron uptake, regulation and metabolism, including the redistribution of iron in the host defense system during viral infection, can induce ferroptosis. Fenton reactions, a central characteristic of ferroptosis, are caused by the increased iron content in the cell. Therefore, viral infections that increase cellular iron content or intestinal iron absorption are likely to cause ferroptosis. In addition, we discuss the hijacking of the iron regulatoy pathway and the antioxidant response, both of which are typical in viral infections. Understanding the potential signaling mechanisms of ferroptosis in viral infections will aid in the development of new therapeutic agents.

Emerging role of the cGAS-STING signaling pathway in autoimmune diseases: Biologic function, mechanisms and clinical prospection

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway, as vital component of innate immune system, acts a vital role in distinguishing invasive pathogens and cytosolic DNA. Cytosolic DNA sensor cGAS first binds to cytosolic DNA and catalyze synthesis of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), which is known as the secondmessenger. Next, cGAMP activates the adaptor protein STING, triggering a molecular chain reaction to stimulate cytokines including interferons (IFNs). Recently, many researches have revealed that the regulatory role of cGAS-STING signaling pathway in autoimmune diseases (AIDs) such as Rheumatoid arthritis (RA), Aicardi Goutières syndrome (AGS) and systemic lupus erythematosus (SLE). Moreover, accumulated evidence showed inhibition of the cGAS-STING signaling pathway can remarkably suppress joint swelling and inflammatory cell infiltration in RA mice. Therefore, in this review, we describe the molecular properties, biologic function and mechanisms of the cGAS-STING signaling pathway in AIDs. In addition, potential clinical applications especially selective small molecule inhibitors targeting the cGAS-STING signaling pathway are also discussed.

SARS-CoV-2 couples evasion of inflammatory response to activated nucleotide synthesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the global COVID-19 pandemic. Although ongoing vaccination drastically reduces SARS-CoV-2 infection, mutant viruses are emerging under the pressure of neutralizing antibodies, calling for new antiviral strategies. Here, we report that SARS-CoV-2 couples evasion of inflammatory response to activated nucleotide synthesis. Inhibition of a key metabolic enzyme not only depletes the nucleotide pool but also restores host inflammatory defense, thereby effectively impeding SARS-CoV-2 replication. Targeting cellular enzymes offers an avenue to combat rapidly evolving SARS-CoV-2 variants.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolves rapidly under the pressure of host immunity, as evidenced by waves of emerging variants despite effective vaccinations, highlighting the need for complementing antivirals. We report that targeting a pyrimidine synthesis enzyme restores inflammatory response and depletes the nucleotide pool to impede SARS-CoV-2 infection. SARS-CoV-2 deploys Nsp9 to activate carbamoyl-phosphate synthetase, aspartate transcarbamoylase, and dihydroorotase (CAD) that catalyzes the rate-limiting steps of the de novo pyrimidine synthesis. Activated CAD not only fuels de novo nucleotide synthesis but also deamidates RelA. While RelA deamidation shuts down NF-κB activation and subsequent inflammatory response, it up-regulates key glycolytic enzymes to promote aerobic glycolysis that provides metabolites for de novo nucleotide synthesis. A newly synthesized small-molecule inhibitor of CAD restores antiviral inflammatory response and depletes the pyrimidine pool, thus effectively impeding SARS-CoV-2 replication. Targeting an essential cellular metabolic enzyme thus offers an antiviral strategy that would be more refractory to SARS-CoV-2 genetic changes.

Production and Functionalities of Specialized Metabolites from Different Organic Sources

Medicinal plants are rich sources of specialized metabolites that are of great importance to plants, animals, and humans. The usefulness of active biological compounds cuts across different fields, such as agriculture, forestry, food processing and packaging, biofuels, biocatalysts, and environmental remediation. In recent years, research has shifted toward the use of microbes, especially endophytes (bacteria, fungi, and viruses), and the combination of these organisms with other alternatives to optimize the production and regulation of these compounds. This review reinforces the production of specialized metabolites, especially by plants and microorganisms, and the effectiveness of microorganisms in increasing the production/concentration of these compounds in plants. The study also highlights the functions of these compounds in plants and their applications in various fields. New research areas that should be explored to produce and regulate these compounds, especially in plants and microbes, have been identified. Methods involving molecular studies are yet to be fully explored, and next-generation sequencing possesses an interesting and reliable approach.

Distinguishing the Pros and Cons of Metabolic Reprogramming in Oncolytic Virus Immunotherapy

Oncolytic viruses (OVs) represent a class of cancer immunotherapies that rely on hijacking the host cell factory for replicative oncolysis and eliciting immune responses for tumor clearance. An increasing evidence suggests that the metabolic state of tumor cells and immune cells is a putative determinant of the efficacy of cancer immunotherapy. However, how therapeutic intervention with OVs affects metabolic fluxes within the tumor microenvironment (TME) remains poorly understood. Herein, we review the complexities of metabolic reprogramming involving the effects of viruses and their consequences on tumor cells and immune cells. We highlight the inherent drawback of oncolytic virotherapy, namely that treatment with OVs inevitably further exacerbates the depletion of nutrients and the accumulation of metabolic wastes in the TME, leading to a metabolic barrier to antitumor immune responses. We also describe targeted metabolic strategies that can be used to unlock the therapeutic potential of OVs.

Transcriptome profiling in swine macrophages infected with African swine fever virus at single-cell resolution

African swine fever virus (ASFV) causes a severe and highly contagious disease in pigs and wild boars, but no commercial vaccines or antivirals are available currently. Understanding the mutual antagonism between virus and host factors during ASFV infection may facilitate the development of new vaccines and antivirals. Our work profiled transcriptomes of swine macrophages infected with ASFV through single-cell RNA-sequencing technology. Identified dynamic transcriptome events of viral genes provide molecular characteristics of ASFV during infection. Moreover, virus–host interactions imply the regulation pathway of viral replication in host cells, which may guide research on antiviral strategies and dissection of ASFV pathogenesis.

African swine fever virus (ASFV) is the causative agent of African swine fever, a highly contagious and usually fatal disease in pigs. The pathogenesis of ASFV infection has not been clearly elucidated. Here, we used single-cell RNA-sequencing technology to survey the transcriptomic landscape of ASFV-infected primary porcine alveolar macrophages. The temporal dynamic analysis of viral genes revealed increased expression of viral transmembrane genes. Molecular characteristics in the ASFV-exposed cells exhibited the activation of antiviral signaling pathways with increased expression levels of interferon-stimulated genes and inflammatory- and cytokine-related genes. By comparing infected cells with unexposed cells, we showed that the unfolded protein response (UPR) pathway was activated in low viral load cells, while the expression level of UPR-related genes in high viral load cells was less than that in unexposed cells. Cells infected with various viral loads showed signature transcriptomic changes at the median progression of infection. Within the infected cells, differential expression analysis and coregulated virus–host analysis both demonstrated that ASFV promoted metabolic pathways but inhibited interferon and UPR signaling, implying the regulation pathway of viral replication in host cells. Furthermore, our results revealed that the cell apoptosis pathway was activated upon ASFV infection. Mechanistically, the production of tumor necrosis factor alpha (TNF-α) induced by ASFV infection is necessary for cell apoptosis, highlighting the importance of TNF-α in ASFV pathogenesis. Collectively, the data provide insights into the comprehensive host responses and complex virus–host interactions during ASFV infection, which may instruct future research on antiviral strategies.

Proteomic landscape of SARS-CoV-2- and MERS-CoV-infected primary human renal epithelial cells

Acute kidney injury is associated with mortality in COVID-19 patients. However, host cell changes underlying infection of renal cells with SARS-CoV-2 remain unknown and prevent understanding of the molecular mechanisms that may contribute to renal pathology. Here, we carried out quantitative translatome and whole-cell proteomics analyses of primary renal proximal and distal tubular epithelial cells derived from human donors infected with SARS-CoV-2 or MERS-CoV to disseminate virus and cell type-specific changes over time. Our findings revealed shared pathways modified upon infection with both viruses, as well as SARS-CoV-2-specific host cell modulation driving key changes in innate immune activation and cellular protein quality control. Notably, MERS-CoV infection-induced specific changes in mitochondrial biology that were not observed in response to SARS-CoV-2 infection. Furthermore, we identified extensive modulation in pathways associated with kidney failure that changed in a virus- and cell type-specific manner. In summary, we provide an overview of the effects of SARS-CoV-2 or MERS-CoV infection on primary renal epithelial cells revealing key pathways that may be essential for viral replication.

A first glimpse into the transcriptomic changes induced by the PaV1 infection in the gut of Caribbean spiny lobsters, Panulirus argus (Latreille, 1804) (Decapoda: Achelata: Palinuridae)

The Caribbean spiny lobster, Panulirus argus (Latreille, 1804) supports important fisheries in the Caribbean region. This species is affected by a deadly virus, Panulirus argus Virus 1 (PaV1), the only known pathogenic virus for this species. As infection progresses, the effects of PaV1 on its host become systemic, with far reaching impacts on the host's physiology, including structural injuries to its gastrointestinal organs, such as the hepatopancreas and the gut. This last one becomes highly compromised in the last stages of infection. Since the gut is a key organ for the physiological stability of lobsters, we compared the transcriptomic changes in the gut of juvenile individuals of Panulirus argus naturally infected with PaV1. In the RNA-Seq analysis, we obtained a total of 485 × 10⁶ raw reads. After cleaning, reads were de novo assembled into 68,842 transcripts and 50,257 unigenes. The length of unigenes ranged from 201 bp to 28,717 bp, with a N50 length of 2079, and a GC content of 40.61%. In the differential gene expression analysis, we identified a total of 3,405 non redundant differential transcripts, of which 1,920 were up-regulated and 1,485 were down-regulated. We found alterations in transcripts encoding for proteins involved in transcriptional regulation, splicing, postraductional regulation, protein signaling, transmembrane transport, cytoskeletal regulation, and proteolysis, among others. This is the first insight into the transcriptomic regulation of PaV1-P. argus interaction. The information generated can help to unravel the molecular mechanisms that may intervene in the gut during PaV1 infection.

Activation of TCA cycle restrains virus-metabolic hijacking and viral replication in mouse hepatitis virus-infected cells

Background

One of coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused coronavirus disease 2019 (COVID-19) pandemic and threatened worldwide. However, therapy for COVID-19 has rarely been proven to possess specific efficacy. As the virus relies on host metabolism for its survival, several studies have reported metabolic intervention by SARS-CoV-2.

Results

We investigated the coronavirus-metabolic hijacking using mouse hepatitis virus (MHV) as a surrogate for SARS-CoV-2. Based on the altered host metabolism by MHV infection, an increase of glycolysis with low mitochondrial metabolism, we tried to investigate possible therapeutic molecules which increase the TCA cycle. Endogenous metabolites and metabolic regulators were introduced to restrain viral replication by metabolic intervention. We observed that cells deprived of cellular energy nutrition with low glycolysis strongly suppress viral replication. Furthermore, viral replication was also significantly suppressed by electron transport chain inhibitors which exhaust cellular energy. Apart from glycolysis and ETC, pyruvate supplement suppressed viral replication by the TCA cycle induction. As the non-glucose metabolite, fatty acids supplement decreased viral replication via the TCA cycle. Additionally, as a highly possible therapeutic metabolite, nicotinamide riboside (NR) supplement, which activates the TCA cycle by supplying NAD+, substantially suppressed viral replication.

Conclusions

This study suggests that metabolite-mediated TCA cycle activation suppresses replication of coronavirus and suggests that NR might play a role as a novel therapeutic metabolite for coronavirus.