miR-9-5p regulates immunometabolic and epigenetic pathways in β-glucan-trained immunity via IDH3α

Overexpressed Rv0222 in M. smegmatis suppresses host innate immunity by downregulating miR-9 target SIRT1

Tuberculosis (TB) remains one of the most fatal infectious diseases, the pathogenic bacterium Mycobacterium tuberculosis (Mtb) has a thick wall to resist the invasion of extracellular substances and secretes a variety of virulence proteins to antagonize host innate immunity. Rv0222, a protein encoded by the gene Rv0222 in the RD4 region of Mtb, is a critical virulence factor in the pathogenicity of Mtb. However, the mechanism of its regulation of miRNAs during bacterial infection is unclear. We used Rv0222 gene and Mycobacterium smegmatis (M. smegmatis), which is highly homologous to Mtb, to construct Rv0222 recombinant M. smegmatis Ms_Rv0222. Ms_Rv0222 induced down-regulation of miR-9 expression and up-regulation of SIRT1 in RAW264.7 cells and mice post-infection. Up-regulation of SIRT1 caused down-regulation of p65 activity and decreased the expression of pro-inflammatory cytokine, which increased the intracellular survival of M. smegmatis. Si-SIRT1 induced up-regulation of p65 activity and increased the expression of pro-inflammatory cytokine, then decreased the intracellular survival of M. smegmatis. This study reveals that Mtb Rv0222 mediates the suppression of host innate immunity by miR-9 and its target SIRT1, and may provide a potential site for the development of new anti-TB drugs targeting Rv0222.

BCG-trained macrophages couple LDLR upregulation to type I IFN responses and antiviral immunity

Trained immunity refers to memory-like responses of innate immune cells when they re-encounter pathogenic stimuli. Bacillus Calmette-Guérin (BCG) vaccination implies enhanced antiviral immunity, whereas the underlying mechanisms remain unclear. Herein, we have uncovered elevated expression of low-density lipoprotein receptor (LDLR) on BCG-trained macrophages with robust type I interferon (IFNI) production and antiviral effects both in vivo and in vitro. Consequently, cholesterol is accumulated in BCG-trained macrophages, leading to the augmentation of NFE2L1 expression and the formation of NFE2L1/IRAK1/TRIM25 complex where TRIM25 mediates IRAK1 K63 polyubiquitination to exaggerate IFNI responses in an RIG-I-dependent manner. We have also observed LDLR+ macrophages displaying heightened IFNI responses in BCG-treated human macrophages. To antagonize LDLR degradation by PCSK9 inhibitors increases IFNI responses in the macrophages and accelerated viral clearance. Our study thus couples LDLR upregulation to antiviral activity in BCG-trained macrophages, making commercial PCSK9 inhibitors potential antiviral indications in clinic.

Trained immunity using probiotics and inactivated pathogens enhances resistance to Salmonella enterica serovar Typhimurium infection by activating the cGAS-STING signal pathway in mice and chickens

INTRODUCTION

Concerns about antibiotic resistance have prompted interest in alternative strategies for enhancing disease resistance, particularly in livestock and poultry production.

OBJECTIVES

This study explored the role of trained immunity in enhancing resistance to Salmonella enterica serovar Typhimurium (S. Typhimurium) infection in mice and chickens.

METHODS

We investigated the effects of probiotics and inactivated pathogenic bacterial strains on host immunity in Toll-like receptor 2-deficient mice (TLR2-/-) to assess whether these effects were related to bacterial outer membrane components such as peptidoglycan (PNG), lipoarabinomannan (LAM) and lipoteichoic acid (LTA). Bacterial genomes were evaluated for their ability to enhance the host immune system. Macrophage-depletion models were used to identify the key immune cells involved in trained immunity, with a focus on the cGAS-STING pathway.

RESULTS

Probiotics and inactivated pathogenic strains enhanced host immunity and protected against S. Typhimurium infection. As demonstrated in the TLR2-deficient mice, the effects were not dependent on bacterial outer membrane components. Instead, bacterial genomes played a significant role in activating trained immunity. Macrophages were identified as the primary cells that mediated the response with the cGAS-STING pathway playing a crucial role. The results observed using the mouse models led to investigating the potential application of trained immunity in poultry.

CONCLUSION

Trained immunity activated by probiotics and inactivated bacterial pathogens enhanced resistance against S. Typhimurium infection via macrophage activation and involved the cGAS-STING pathway. These findings highlight the potential of trained immunity as an alternative strategy for disease prevention in both livestock and poultry.

KDM4 Regulates the Glycolysis of Hemocytes in the Immune Priming of Eriocheir sinensis

Immune priming confers a sustained, augmented response of innate immune cells to a secondary challenge, a process that is characteristically reliant on metabolic reprogramming. Recent evidence suggests that histone demethylases play essential roles in the immune priming, while its regulation role in the metabolic reprogramming remains largely unknown. In the present study, the concentration of glucose was significantly down-regulated in the hemocytes of crab Eriocheir sinensis after secondary stimulation with Aeromonas hydrophila, while the expression levels of phosphofructokinase (EsPFK) pyruvate kinase (EsPK), hexokinase-2 (EsHK-2) and Glucose-6-phosphate dehydrogenase (EsG-6-PD), along with the concentrations of lactate and the ratio of NAD+/NADH, were elevated. Additionally, the levels of H3K9me3 and its enrichment at the promoters of EsPFK and EsG-6-PD were significantly decreased at 7 days after A. hydrophila stimulation. The lysine Demethylase 4 homologue (EsKDM4) was observed to translocate into the nucleus of crab hemocytes after A. hydrophila stimulation, and its activity markedly increased after secondary stimulation with A. hydrophila. Following RNA interference of EsKDM4, there was a significant increase in H3K9me3 levels, and the enrichment of H3K9me3 at the EsPFK and EsG-6-PD promoters, as well as the concentration of glucose, in the hemocytes of crabs after secondary stimulation with A. hydrophila. Furthermore, mRNA transcripts of EsPFK and EsG-6-PD, as well as the concentration of lactate and ratio of NAD+/NADH, significantly decreased after secondary stimulation. These results suggested that EsKDM4 mediates the enrichment of H3K9me3 at the promoters of EsPFK and EsG-6-PD, thereby regulating glycolysis during the immune priming of crabs.

Biological evaluation of curdlan sulfate-based nanoparticles in trained immunity enhancement: In vitro and in vivo approaches

OBJECTIVES

Recently, more and more evidences suggest that β-glucans can induce trained immunity and non-specific protections against pathogens. However, most of the reports evaluated the immunological activities of β-glucans through injection route but no nasal inhalation. In this study, the effects of curdlan sulfate-based nanoparticles, CS/O-HTCC on trained immunity through intranasal administration were evaluated.

METHODS

Macrophages were treated with CS/O-HTCC and the metabolisms of the macrophages were detected. Mice were intranasal administered with CS/O-HTCC for 3 times with a 14 days interval, then the antitumor or infection prevention effects were assessed.

RESULTS

In vitro, CS/O-HTCC enhanced the macrophage metabolism significantly through upregulating glycolysis (26.1 ± 4.3 mpH/min) and oxidative phosphorylation (36.0 ± 9.0 pmol/min) compared with that of negative group (7.5 ± 2.3 mpH/min and 19.5 ± 4.9 pmol/min). In vivo, CS/O-HTCC inhibited lung metastasis of B16F10 tumor cells and improved the survival time (26.5 days) of the nmice compared with negative group (19.5 days). Moreover, CS/O-HTCC prevented the lung infections by Escherichia coli or Streptococcus pneumoniae (less bacterial residual) and reduced lung damages.

CONCLUSIONS

CS/O-HTCC can induce trained immunity through enhancing the metabolism of macrophages and enhance the non-specific protection against pathogens through intranasal immunization.

Unlocking the potential of T-cell metabolism reprogramming: Advancing single-cell approaches for precision immunotherapy in tumour immunity

As single-cell RNA sequencing enables the detailed clustering of T-cell subpopulations and facilitates the analysis of T-cell metabolic states and metabolite dynamics, it has gained prominence as the preferred tool for understanding heterogeneous cellular metabolism. Furthermore, the synergistic or inhibitory effects of various metabolic pathways within T cells in the tumour microenvironment are coordinated, and increased activity of specific metabolic pathways generally corresponds to increased functional activity, leading to diverse T-cell behaviours related to the effects of tumour immune cells, which shows the potential of tumour-specific T cells to induce persistent immune responses. A holistic understanding of how metabolic heterogeneity governs the immune function of specific T-cell subsets is key to obtaining field-level insights into immunometabolism. Therefore, exploring the mechanisms underlying the interplay between T-cell metabolism and immune functions will pave the way for precise immunotherapy approaches in the future, which will empower us to explore new methods for combating tumours with enhanced efficacy.

Mucosal recombinant BCG vaccine induces lung-resident memory macrophages and enhances trained immunity via mTORC2/HK1-mediated metabolic rewiring

Bacillus Calmette-Guérin (BCG) vaccination induces a type of immune memory known as "trained immunity", characterized by the immunometabolic and epigenetic changes in innate immune cells. However, the molecular mechanism underlying the strategies for inducing and/or boosting trained immunity in alveolar macrophages remains unknown. Here, we found that mucosal vaccination with the recombinant strain rBCGPPE27 significantly augmented the trained immune response in mice, facilitating a superior protective response against Mycobacterium tuberculosis and non-related bacterial reinfection in mice when compared to BCG. Mucosal immunization with rBCGPPE27 enhanced innate cytokine production by alveolar macrophages associated with promoted glycolytic metabolism, typical of trained immunity. Deficiency of the mammalian target of rapamycin complex 2 and hexokinase 1 abolished the immunometabolic and epigenetic rewiring in mouse alveolar macrophages after mucosal rBCGPPE27 vaccination. Most noteworthy, utilizing rBCGPPE27's higher-up trained effects: The single mucosal immunization with rBCGPPE27-adjuvanted coronavirus disease (CoV-2) vaccine raised the rapid development of virus-specific immunoglobulin G antibodies, boosted pseudovirus neutralizing antibodies, and augmented T helper type 1-biased cytokine release by vaccine-specific T cells, compared to BCG/CoV-2 vaccine. These findings revealed that mucosal recombinant BCG vaccine induces lung-resident memory macrophages and enhances trained immunity via reprogramming mTORC2- and HK-1-mediated aerobic glycolysis, providing new vaccine strategies for improving tuberculosis (TB) or coronavirus variant vaccinations, and targeting innate immunity via mucosal surfaces.

Characteristics of conserved microRNAome and their evolutionary adaptation to regulation of immune defense functions in the spleen of silver carp and bighead carp

Immune defense functions of silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) have shown obvious evolutionary divergence. MiRNAs participate in the fine regulation of immune function. However, the evolutionary adaptation of miRNAs in the regulation of immune defense function is still poorly understood in silver carp and bighead carp. Here, small RNA libraries were constructed from the spleen tissue of one-year-old and three-year-old healthy silver carp and bighead carp, 424 and 422 known conserved miRNAs were respectively identified from the spleen of silver carp and bighead carp by bioinformatic analysis, which 398 were shared between the two species. These conserved miRNAs showed highly similar expression patterns between silver carp and bighead carp, but the abundance in spleen varied greatly in different species. Family analysis showed that miRNA families including mir-8, mir-7, mir-23, mir-338, mir-30, mir-27, mir-221, mir-19, mir-181, mir-17, mir-15, mir-148, mir-130, mir-10 and let-7 were the main miRNAs in the spleen of silver carp and bighead carp. 27 and 51 significant differentially expressed (SDE) miRNAs were identified from silver carp and bighead carp, respectively. Evolution analysis for the predicted target genes of SDE-miRNAs showed that ten biological processes such as blood coagulation, cell adhesion mediated by integrin and adaptive immune response were positively selected. In addition, immune genes including TLR3, NFATC3, MALT1, B2M, GILT and MHCII were positively selected only in silver carp, and they were specifically targeted by the SDE-miRNAs including miR-9-5p, miR-196a-5p, miR-375, miR-122, miR-722, miR-132-3p, miR-727-5p, miR-724, miR-19d-5p and miR-138-5p, respectively. PLA2G4 in Fc epsilon RI signaling pathway was positively selected only in bighead carp and was specifically targeted by the SDE-miRNAs including miR-222b, miR-22b-5p, miR-15c, miR-146a, miR-125c-3p, miR-221-5p, miR-2188-5p, miR-142a-3p, miR-212, miR-138-5p and miR-15b-5p. In particular, SDE-miRNAs such as miR-144-3p, miR-2188-3p, miR-731, miR-363-3p and miR-218b could simultaneously target multiple evolutionarily differentiated immune-related genes. These results indicated that in the spleen of silver carp and bighead carp, conserved miRNAs have obvious evolutionary adaptations in the regulation of immune defense function. The results of this study can provide valuable resources for further revealing themechanism of miRNA in the formation of resistance traits evolution between silver carp and bighead carp.

Hydroxysafflor yellow A inhibits the hyperactivation of rat platelets by regulating the miR-9a-5p/SRC axis

Pathological platelet activation plays a vital role in the prevalence of cardiovascular diseases. Hydroxysafflor yellow A (HSYA) has been shown to have significant anti-platelet aggregation and anti-activation effects, but its mechanism of action is unclear. Our study showed that HSYA inhibited the expression of platelet surface glycoproteins IIβ/III α (GPIIβ/III α) and thromboxane A2 (TXA2) during platelet activation and reduced platelet Ca2+ accumulation. HSYA significantly reduced the number of platelets and inhibited adrenaline-induced platelet hyperaggregation in rats. Transcriptomic analysis of platelets suggested that HSYA significantly suppressed SRC and MAPK3 (ERK1/2) gene expression. YEEI peptide, an SRC activator, could significantly reverse the inhibition of HSYA on the phosphorylation of SRC/PLCγ2/PKCδ/MEK/ERK1/2 pathway proteins and reverse the effect of HSYA on platelet activation-related markers GPIIβ/IIIα protein, TXA2 and cAMP. The SRC genes were further predicted by transcriptome analysis of HSYA-regulated miRNAs combined with bioinformatics techniques. The results suggested that HSYA could significantly upregulate the expression level of the miR-9a-5p gene and further confirmed that miR-9a-5p had a targeted regulatory relationship with SRC by dual-luciferase activity reporter and cell transfection experiments. The inhibitory effect of HSYA on the SRC/PLCγ2/PKCδ/MEK/ERK1/2 pathway was significantly reversed after platelets were transfected with the miR-9a inhibitor, while SRC siRNA attenuated the effect of the miR-9a inhibitor. SRC siRNA was able to attenuate the effect of the miR-9a inhibitor. In conclusion, this study suggests that HSYA can inhibit the activation of the SRC/PLCγ2/PKC δ/MEK/ERK1/2 axis by upregulating platelet miR-9a-5p, thereby reducing the activation of platelets and inhibiting platelet aggregation.

Coordination of cross-talk between metabolism and epigenetic regulation by the SIN3 complex

Post-translational modifications of histone proteins control the expression of genes. Metabolites from central and one-carbon metabolism act as donor moieties to modify histones and regulate gene expression. Thus, histone modification and gene regulation are connected to the metabolite status of the cell. Histone modifiers, such as the SIN3 complex, regulate genes involved in proliferation and metabolism. The SIN3 complex contains a histone deacetylase and a histone demethylase, which regulate the chromatin landscape and gene expression. In this chapter, we review the cross-talk between metabolic pathways that produce donor moieties, and epigenetic complexes regulating proliferation and metabolic genes. This cross-talk between gene regulation and metabolism is tightly controlled, and disruption of this cross-talk leads to metabolic diseases. We discuss promising therapeutics that directly regulate histone modifiers, and can affect the metabolic status of the cell, alleviating some metabolic diseases.

Training vs. Tolerance: The Yin/Yang of the Innate Immune System

For almost nearly a century, memory functions have been attributed only to acquired immune cells. Lately, this paradigm has been challenged by an increasing number of studies revealing that innate immune cells are capable of exhibiting memory-like features resulting in increased responsiveness to subsequent challenges, a process known as trained immunity (known also as innate memory). In contrast, the refractory state of endotoxin tolerance has been defined as an immunosuppressive state of myeloid cells portrayed by a significant reduction in the inflammatory capacity. Both training as well tolerance as adaptive features are reported to be accompanied by epigenetic and metabolic alterations occurring in cells. While training conveys proper protection against secondary infections, the induction of endotoxin tolerance promotes repairing mechanisms in the cells. Consequently, the inappropriate induction of these adaptive cues may trigger maladaptive effects, promoting an increased susceptibility to secondary infections-tolerance, or contribute to the progression of the inflammatory disorder-trained immunity. This review aims at the discussion of these opposing manners of innate immune and non-immune cells, describing the molecular, metabolic and epigenetic mechanisms involved and interpreting the clinical implications in various inflammatory pathologies.

Immune dysfunction signatures predict outcomes and define checkpoint blockade-unresponsive microenvironments in acute myeloid leukemia

BackgroundImmune exhaustion and senescence are dominant dysfunctional states of effector T cells and major hurdles for the success of cancer immunotherapy. In the current study, we characterized how acute myeloid leukemia (AML) promotes the generation of senescent-like CD8+ T cells and whether they have prognostic relevance.METHODSWe analyzed NanoString, bulk RNA-Seq and single-cell RNA-Seq data from independent clinical cohorts comprising 1,896 patients treated with chemotherapy and/or immune checkpoint blockade (ICB).ResultsWe show that senescent-like bone marrow CD8+ T cells were impaired in killing autologous AML blasts and that their proportion negatively correlated with overall survival (OS). We defined what we believe to be new immune effector dysfunction (IED) signatures using 2 gene expression profiling platforms and reported that IED scores correlated with adverse-risk molecular lesions, stemness, and poor outcomes; these scores were a more powerful predictor of OS than 2017-ELN risk or leukemia stem cell (LSC17) scores. IED expression signatures also identified an ICB-unresponsive tumor microenvironment and predicted significantly shorter OS.ConclusionThe IED scores provided improved AML-risk stratification and could facilitate the delivery of personalized immunotherapies to patients who are most likely to benefit.TRIAL REGISTRATIONClinicalTrials.gov; NCT02845297.FUNDINGJohn and Lucille van Geest Foundation, Nottingham Trent University's Health & Wellbeing Strategic Research Theme, NIH/NCI P01CA225618, Genentech-imCORE ML40354, Qatar National Research Fund (NPRP8-2297-3-494).

Neuroinflammation in retinitis pigmentosa: Therapies targeting the innate immune system

Retinitis pigmentosa (RP) is an important cause of irreversible blindness worldwide and lacks effective treatment strategies. Although mutations are the primary cause of RP, research over the past decades has shown that neuroinflammation is an important cause of RP progression. Due to the abnormal activation of immunity, continuous sterile inflammation results in neuron loss and structural destruction. Therapies targeting inflammation have shown their potential to attenuate photoreceptor degeneration in preclinical models. Regardless of variations in genetic background, inflammatory modulation is emerging as an important role in the treatment of RP. We summarize the evidence for the role of inflammation in RP and mention therapeutic strategies where available, focusing on the modulation of innate immune signals, including TNFα signaling, TLR signaling, NLRP3 inflammasome activation, chemokine signaling and JAK/STAT signaling. In addition, we describe epigenetic regulation, the gut microbiome and herbal agents as prospective treatment strategies for RP in recent advances.

Cromileptes altivelis microRNA Transcriptome Analysis upon Nervous Necrosis Virus (NNV) Infection and the Effect of cal-miR-155 on Cells Apoptosis and Virus Replication

MicroRNAs (miRNAs) could regulate various biological processes. Nervous necrosis virus (NNV) is one of the primary germs of the Humpback grouper (Cromileptes altivelis), a commercial fish of great importance for Asian aquaculture. However, there is limited available information on the host-virus interactions of C. altivelis. miRNAs have been shown to play key roles in the host response to infection by a variety of pathogens. To better understand the regulatory mechanism of miRNAs, we constructed miRNA transcriptomes and identified immune-related miRNAs of C. altivelis spleen in response to NNV infection. Reads from the three libraries were mapped onto the Danio rerio reference genome. As a result, a total of 942 mature miRNAs were determined, with 266 known miRNAs and 676 novel miRNAs. Among them, thirty-two differentially expressed miRNAs (DEmiRs) were identified compared to the PBS control. These DEmiRs were targeted on 895 genes, respectively, by using miRanda v3.3a. Then, 14 DEmiRs were validated by qRT-PCR and showed consistency with those obtained from high-throughput sequencing. In order to study the relationship between viral infection and host miRNA, a cell line from C. altivelis brain (CAB) was used to examine the expressions of five known DEmiRs (miR-132-3p, miR-194a, miR-155, miR-203b-5p, and miR-146) during NNV infection. The results showed that one miRNA, cal-miRNA-155, displayed significantly increased expression in response to the virus infection. Subsequently, it was proved that overexpression of cal-miR-155 enhanced cell apoptosis with or without NNV infection and inhibited virus replication in CAB cells. Oppositely, the cal-miRNA-155 inhibitor markedly suppressed apoptosis in CAB cells. The results of the apoptosis-related genes mRNA expression also showed the regulation of cal-miR-155 on the apoptosis process in CAB cells. These findings verify that miR-155 might exert a function as a pro-apoptotic factor in reply to NNV stimulation in CAB cells and help us further study the molecular mechanisms of the pathogenesis of NNV in C. altivelis.

Trained immunity: A Yin-Yang balance

Traditionally, immune memory is regarded as an exclusive hallmark of adaptive immunity. However, a growing body of evidence suggesting that innate immune cells show adaptive characteristics has challenged this dogma. In the past decade, trained immunity, a de facto innate immune memory, has been defined as a long-term functional reprogramming of cells of the innate immune system: the reprogramming is evoked by endogenous or exogenous insults, the cells return to a nonactivated state and subsequently show altered inflammatory responses against a second challenge. Trained immunity became regarded as a mechanism selected in evolution to protect against infection; however, a maladaptive effect might result in hyperinflammation. This dual effect is consistent with the Yin-Yang theory in traditional Chinese philosophy, in which Yang represents active, positive, and aggressive factors, whereas Yin represents passive, negative, and inhibitory factors. In this review, we give a brief overview of history and latest progress about trained immunity, including experimental models, inductors, molecular mechanisms, clinical application and so on. Moreover, this is the first time to put forward the theory of Yin-Yang balance to understand trained immunity. We envision that more efforts will be focused on developing novel immunotherapies targeting trained immunity in the coming years.

Hypoxia signalling in the regulation of innate immune training

Innate immune function is shaped by prior exposures in a phenomenon often referred to as 'memory' or 'training'. Diverse stimuli, ranging from pathogen-associated molecules to atherogenic lipoproteins, induce long-lasting training, impacting on future responses, even to distinct stimuli. It is now recognised that epigenetic modifications in innate immune cells, and their progenitors, underpin these sustained behavioural changes, and that rewired cellular metabolism plays a key role in facilitating such epigenetic marks. Oxygen is central to cellular metabolism, and cells exposed to hypoxia undergo profound metabolic rewiring. A central effector of these responses are the hypoxia inducible factors (or HIFs), which drive transcriptional programmes aiming to adapt cellular homeostasis, such as by increasing glycolysis. These metabolic shifts indirectly promote post-translational modification of the DNA-binding histone proteins, and also of DNA itself, which are retained even after cellular oxygen tension and metabolism normalise, chronically altering DNA accessibility and utilisation. Notably, the activity of HIFs can be induced in some normoxic circumstances, indicating their broad importance to cell biology, irrespective of oxygen tension. Some HIFs are implicated in innate immune training and hypoxia is present in many disease states, yet many questions remain about the association between hypoxia and training, both in health and disease. Moreover, it is now appreciated that cellular responses to hypoxia are mediated by non-HIF pathways, suggesting that other mechanisms of training may be possible. This review sets out to define what is already known about the topic, address gaps in our knowledge, and provide recommendations for future research.

Fighting the SARS-CoV-2 pandemic requires a global approach to understanding the heterogeneity of vaccine responses

Host genetic and environmental factors including age, biological sex, diet, geographical location, microbiome composition and metabolites converge to influence innate and adaptive immune responses to vaccines. Failure to understand and account for these factors when investigating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine efficacy may impair the development of the next generation of vaccines. Most studies aimed at identifying mechanisms of vaccine-mediated immune protection have focused on adaptive immune responses. It is well established, however, that mobilization of the innate immune response is essential to the development of effective cellular and humoral immunity. A comprehensive understanding of the innate immune response and environmental factors that contribute to the development of broad and durable cellular and humoral immune responses to SARS-CoV-2 and other vaccines requires a holistic and unbiased approach. Along with optimization of the immunogen and vectors, the development of adjuvants based on our evolving understanding of how the innate immune system shapes vaccine responses will be essential. Defining the innate immune mechanisms underlying the establishment of long-lived plasma cells and memory T cells could lead to a universal vaccine for coronaviruses, a key biomedical priority.

Proline dehydrogenase in cancer: apoptosis, autophagy, nutrient dependency and cancer therapy

L-proline catabolism is emerging as a key pathway that is critical to cellular metabolism, growth, survival, and death. Proline dehydrogenase (PRODH) enzyme, which catalyzes the first step of proline catabolism, has diverse functional roles in regulating many pathophysiological processes, including apoptosis, autophagy, cell senescence, and cancer metastasis. Notably, accumulated evidence demonstrated that PRODH plays complex role in many types of cancers. In this review, we briefly introduce the function of PRODH, then its expression in different types of cancer. We next discuss the regulation of PRODH in cancer, the downstream pathways of PRODH and the therapies that are under investigation. Finally, we propose novel insights for future perspectives on the modulation of PRODH.