Neonatal monocytes exhibit a unique histone modification landscape

Adenosine kinase inhibition protects mice from abdominal aortic aneurysm via epigenetic modulation of VSMC inflammation

AIMS

Abdominal aortic aneurysm (AAA) is a common, serious vascular disease with no effective pharmacological treatment. The nucleoside adenosine plays an important role in modulating vascular homeostasis, which prompted us to determine whether adenosine kinase (ADK), an adenosine metabolizing enzyme, modulates AAA formation via control of the intracellular adenosine level, and to investigate the underlying mechanisms.

METHODS AND RESULTS

We used a combination of genetic and pharmacological approaches in murine models of AAA induced by calcium chloride (CaCl2) application or angiotensin II (Ang II) infusion to study the role of ADK in the development of AAA. In vitro functional assays were performed by knocking down ADK with adenovirus-short hairpin RNA in human vascular smooth muscle cells (VSMCs), and the molecular mechanisms underlying ADK function were investigated using RNA-sequencing, isotope tracing, and chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR). The heterozygous deficiency of ADK protected mice from CaCl2- and Ang II-induced AAA formation. Moreover, specific knockout of ADK in VSMCs prevented Ang II-induced AAA formation, as evidenced by reduced aortic extracellular elastin fragmentation, neovascularization, and aortic inflammation. Mechanistically, ADK knockdown in VSMCs markedly suppressed the expression of inflammatory genes associated with AAA formation, and these effects were independent of adenosine receptors. The metabolic flux and ChIP-qPCR results showed that ADK knockdown in VSMCs decreased S-adenosylmethionine (SAM)-dependent transmethylation, thereby reducing H3K4me3 binding to the promoter regions of the genes that are associated with inflammation, angiogenesis, and extracellular elastin fragmentation. Furthermore, the ADK inhibitor ABT702 protected mice from CaCl2-induced aortic inflammation, extracellular elastin fragmentation, and AAA formation.

CONCLUSION

Our findings reveal a novel role for ADK inhibition in attenuating AAA via epigenetic modulation of key inflammatory genes linked to AAA pathogenesis.

Macrophage memories of early-life injury drive neonatal nociceptive priming

The developing peripheral nervous and immune systems are functionally distinct from those of adults. These systems are vulnerable to early-life injury, which influences outcomes related to nociception following subsequent injury later in life (i.e., "neonatal nociceptive priming"). The underpinnings of this phenomenon are unclear, although previous work indicates that macrophages are trained by inflammation and injury. Our findings show that macrophages are both necessary and partially sufficient to drive neonatal nociceptive priming, possibly due to a long-lasting remodeling in chromatin structure. The p75 neurotrophic factor receptor is an important effector in regulating neonatal nociceptive priming through modulation of the inflammatory profile of rodent and human macrophages. This "pain memory" is long lasting in females and can be transferred to a naive host to alter sex-specific pain-related behaviors. This study reveals a mechanism by which acute, neonatal post-surgical pain drives a peripheral immune-related predisposition to persistent pain following a subsequent injury.

Epigenetic and transcriptional regulation of cytokine production by Plasmodium falciparum-exposed monocytes

Plasmodium falciparum infection causes the most severe form of malaria, where excessive production of proinflammatory cytokines can drive the pathogenesis of the disease. Monocytes play key roles in host defense against malaria through cytokine production and phagocytosis; however, they are also implicated in pathogenesis through excessive proinflammatory cytokine production. Understanding the underlying molecular mechanisms that contribute to inflammatory cytokine production in P. falciparum-exposed monocytes is key towards developing better treatments. Here, we provide molecular evidence that histone 3 lysine 4 (H3K4) methylation is key for inflammatory cytokine production in P. falciparum-exposed monocytes. In an established in vitro system that mimics blood stage infection, elevated proinflammatory TNF and IL-6 cytokine production is correlated with increased mono- and tri-methylated H3K4 levels. Significantly, we demonstrate through utilizing a pharmacological inhibitor of H3K4 methylation that TNF and IL-6 expression can be suppressed in P. falciparum-exposed monocytes. This elucidated epigenetic regulatory mechanism, controlling inflammatory cytokine production, potentially provides new therapeutic options for future malaria treatment.

Macrophage epigenetic memories of early life injury drive neonatal nociceptive priming

The developing peripheral nervous and immune systems are functionally distinct from adults. These systems are vulnerable to early life injury, which influences outcomes related to nociception following subsequent injury later in life (neonatal nociceptive priming). The underpinnings of this phenomenon are largely unknown, although previous work indicates that macrophages are epigenetically trained by inflammation and injury. We found that macrophages are both necessary and partially sufficient to drive neonatal nociceptive priming possibly due to a long-lasting epigenetic remodeling. The p75 neurotrophic factor receptor (NTR) was an important effector in regulating neonatal nociceptive priming through modulation of the inflammatory profile of rodent and human macrophages. This pain memory was long lasting in females and could be transferred to a naive host to alter sex-specific pain-related behaviors. This study reveals a novel mechanism by which acute, neonatal post-surgical pain drives a peripheral immune-related predisposition to persistent pain following a subsequent injury.

Low H3K27 acetylation of SF1 in PBMC: a biomarker for prenatal dexamethasone exposure-caused adrenal insufficiency of steroid synthesis in male offspring

Dexamethasone is widely used to treat pregnancy disorders related to premature delivery. However, lots of researches have confirmed that prenatal dexamethasone exposure (PDE) could increase the risk of offspring multiple diseases. This study was designed to elucidate the epigenetic mechanism of adrenal developmental programming and explore its early warning marker in peripheral blood mononuclear cells (PBMC). We found the adrenal morphological and functional changes of PDE male offspring rats before and after birth, which were mainly performed as the decreased serum corticosterone concentration, steroidogenic acute regulatory (StAR) protein expression, and histone 3 lysine 27 acetylation (H3K27ac) level of steroidogenic factor 1 (SF1) promoter region and its expression. Simultaneously, the expressions of glucocorticoid receptor (GR) and histone acetylation enzyme 5 (HDAC5) in the PDE male fetal rats were increased. In vitro, dexamethasone reduced the expression of SF1, StAR, and cortisol production and still increased the expression of GR and HDAC5, the binding between GR and SF1 promoter region, and protein interaction between GR and HDAC5. GR siRNA or HDAC5 siRNA was able to reverse the above roles of dexamethasone. Furthermore, in vivo, we confirmed that H3K27ac levels of SF1 promoter region and its expression in PBMC of the PDE group were decreased before and after birth, showing a positive correlation with the same indexes in adrenal. Meanwhile, in clinical trials, we confirmed that prenatal dexamethasone application decreased H3K27ac of SF1 promoter region and its expression in neonatal PBMC. In conclusion, PDE-caused adrenal insufficiency of male offspring rats was related to adrenal GR activated by dexamethasone in uterus. The activated GR, on the one hand, increased its direct binding to SF1 promoter region to inhibit its expression, on the other hand, upregulated and recruited HDAC5 to decrease H3K27ac level of SF1 promoter region, and strengthened the inhibition of SF1 and subsequent StAR expression.

Sex-associated early-life viral innate immune response is transcriptionally associated with chromatin remodeling of type-I IFN-inducible genes

This study investigates sex-associated systemic innate immune differences by examining bone marrow-derived dendritic cells (BMDCs). BMDC grown from 7-day-old mice show enhanced type-I interferon (IFN) signaling in female compared to male BMDC. Upon respiratory syncytial virus (RSV) infection of 7-day-old mice, a significantly altered phenotype of BMDC at 4 weeks post-infection is observed in a sex-dependent manner. The alterations include heightened Ifnb/ interleukin (Il12a) and enhanced IFNAR1+ expression in BMDC from early-life RSV-infected female mice that leads to increased IFN-γ production by T cells. Phenotypic differences were verified upon pulmonary sensitization whereby EL-RSV male-derived BMDC promoted enhanced T helper 2/17 responses and exacerbated disease upon RSV infection while EL-RSV/F BMDC sensitization was relatively protective. Assay for transposase-accessible chromatin using sequencing analysis (ATAC-seq) demonstrated that EL-RSV/F BMDC had enhanced chromatin accessibility near type-I immune genes with JUN, STAT1/2, and IRF1/8 transcription factors predicted to have binding sites in accessible regions. Importantly, ATAC-seq of human cord blood-derived monocytes displayed a similar sex-associated chromatin landscape with female-derived monocytes having more accessibility in type-I immune genes. These studies enhance our understanding of sex-associated differences in innate immunity by epigenetically controlled transcriptional programs amplified by early-life infection in females via type-I immunity.

Developmental impact of peripheral injury on neuroimmune signaling

A peripheral injury drives neuroimmune interactions at the level of the injury and throughout the neuraxis. Understanding these systems will be beneficial in the pursuit to target persistent pain that involves both neural and immune components. In this review, we discuss the impact of injury on the development of neuroimmune signaling, along with data that suggest a possible cellular immune memory. We also discuss the parallel effects of injury in the nervous system and immune related areas including bone marrow, lymph node and central nervous system-related cells. Finally, we relate these findings to patient populations and current research that evaluates human tissue.

New Insights in Immunometabolism in Neonatal Monocytes and Macrophages in Health and Disease

It is well established that the neonatal immune system is different from the adult immune system. A major task of the neonatal immune system is to bridge the achievement of tolerance towards harmless antigens and commensal bacteria while providing protection against pathogens. This is highly important because neonates are immunologically challenged directly after birth by a rigorous change from a semi-allogeneic sterile environment into a world rich with microbes. A so called disease tolerogenic state is typical for neonates and is anticipated to prevent immunopathological damage potentially at the cost of uncontrolled pathogen proliferation. As a consequence, neonates are more susceptible than adults to life-threatening infections. At the basis of a well-functioning immune response, both for adults and neonates, innate immune cells such as monocytes and monocyte-derived macrophages play an essential role. A well-responsive monocyte will alter its cellular metabolism to subsequently induce certain immune effector function, a process which is called immunometabolism. Immunometabolism has received extensive attention in the last decade; however, it has not been broadly studied in neonates. This review focuses on carbohydrate metabolism in monocytes and macrophages in neonates. We will exhibit pathways involving glycolysis, the tricarboxylic acid (TCA) cycle and oxidative phosphorylation and their role in shaping neonates' immune systems to a favorable tolerogenic state. More insight into these pathways will elucidate potential treatments targets in life-threatening conditions including neonatal sepsis or expose potential targets which can be used to induce tolerance in conditions where tolerance is harmfully impaired such as in autoimmune diseases.

Viral infection in chronic otitis media with effusion in children

Background

The role of respiratory viruses in chronic otitis media with effusion (COME) in children is not clearly defined. In our study we aimed to investigate the detection of respiratory viruses in middle ear effusions (MEE) as well as the association with local bacteria, respiratory viruses in the nasopharynx and cellular immune response of children with COME.

Methods

This 2017-2019 cross-sectional study included 69 children aged 2-6 undergoing myringotomy for COME. MEE and nasopharyngeal swabs were analyzed via PCR and CT-values for the genome and loads of typical respiratory viruses. Immune cell populations and exhaustion markers in MEE related to respiratory virus detection were studied via FACS. Clinical data including the BMI was correlated.

Results

Respiratory viruses were detected in MEE of 44 children (64%). Rhinovirus (43%), Parainfluenzavirus (26%) and Bocavirus (10%) were detected most frequently. Average Ct values were 33.6 and 33.5 in MEE and nasopharynx, respectively. Higher detection rates correlated with elevated BMI. Monocytes were elevated in MEE (9.5 ± 7.3%/blood leucocytes). Exhaustion markers were elevated on CD4+ and CD8+ T cells and monocytes in MEE.

Conclusion

Respiratory viruses are associated with pediatric COME. Elevated BMI was associated with increased rates of virus associated COME. Changes in cell proportions of innate immunity and expression of exhaustion markers may be related to chronic viral infection.

Imbalanced Inflammatory Responses in Preterm and Term Cord Blood Monocytes and Expansion of the CD14+CD16+ Subset upon Toll-like Receptor Stimulation

Developmentally regulated features of innate immunity are thought to place preterm and term infants at risk of infection and inflammation-related morbidity. Underlying mechanisms are incompletely understood. Differences in monocyte function including toll-like receptor (TLR) expression and signaling have been discussed. Some studies point to generally impaired TLR signaling, others to differences in individual pathways. In the present study, we assessed mRNA and protein expression of pro- and anti-inflammatory cytokines in preterm and term cord blood (CB) monocytes compared with adult controls stimulated ex vivo with Pam3CSK4, zymosan, polyinosinic:polycytidylic acid, lipopolysaccharide, flagellin, and CpG oligonucleotide, which activate the TLR1/2, TLR2/6, TLR3, TLR4, TLR5, and TLR9 pathways, respectively. In parallel, frequencies of monocyte subsets, stimulus-driven TLR expression, and phosphorylation of TLR-associated signaling molecules were analyzed. Independent of stimulus, pro-inflammatory responses of term CB monocytes equaled adult controls. The same held true for preterm CB monocytes-except for lower IL-1β levels. In contrast, CB monocytes released lower amounts of anti-inflammatory IL-10 and IL-1ra, resulting in higher ratios of pro-inflammatory to anti-inflammatory cytokines. Phosphorylation of p65, p38, and ERK1/2 correlated with adult controls. However, stimulated CB samples stood out with higher frequencies of intermediate monocytes (CD14⁺CD16⁺). Both pro-inflammatory net effect and expansion of the intermediate subset were most pronounced upon stimulation with Pam3CSK4 (TLR1/2), zymosan (TR2/6), and lipopolysaccharide (TLR4). Our data demonstrate robust pro-inflammatory and yet attenuated anti-inflammatory responses in preterm and term CB monocytes, along with imbalanced cytokine ratios. Intermediate monocytes, a subset ascribed pro-inflammatory features, might participate in this inflammatory state.

Omics approaches: interactions at the maternal-fetal interface and origins of child health and disease

Immunoperinatology is an emerging field. Transdisciplinary efforts by physicians, physician-scientists, basic science researchers, and computational biologists have made substantial advancements by identifying unique immunologic signatures of specific diseases, discovering innovative preventative or treatment strategies, and establishing foundations for individualized neonatal intensive care of the most vulnerable neonates. In this review, we summarize the immunobiology and immunopathology of pregnancy, highlight omics approaches to study the maternal-fetal interface, and their contributions to pregnancy health. We examined the importance of transdisciplinary, multiomic (such as genomics, transcriptomics, proteomics, metabolomics, and immunomics) and machine-learning strategies in unraveling the mechanisms of adverse pregnancy, neonatal, and childhood outcomes and how they can guide the development of novel therapies to improve maternal and neonatal health. IMPACT: Discuss immunoperinatology research from the lens of omics and machine-learning approaches. Identify opportunities for omics-based approaches to delineate infection/inflammation-associated maternal, neonatal, and later life adverse outcomes (e.g., histologic chorioamnionitis [HCA]).

The Immunological Epigenetic Landscape of the Human Life Trajectory

Adaptive immunity changes over an individual’s lifetime, maturing by adulthood and diminishing with old age. Epigenetic mechanisms involving DNA and histone methylation form the molecular basis of immunological memory during lymphocyte development. Monocytes alter their function to convey immune tolerance, yet the epigenetic influences at play remain to be fully understood in the context of lifespan. This study of a healthy genetically homogenous cohort of children, adults and seniors sought to decipher the epigenetic dynamics in B-lymphocytes and monocytes. Variable global cytosine methylation within retro-transposable LINE-1 repeats was noted in monocytes compared to B-lymphocytes across age groups. The expression of the human leukocyte antigen (HLA)-DQ alpha chain gene HLA-DQA1*01 revealed significantly reduced levels in monocytes in all ages relative to B-lymphocytes, as well as between lifespan groups. High melting point analysis and bisulfite sequencing of the HLA-DQA1*01 promoter in monocytes highlighted variable cytosine methylation in children and seniors but greater stability at this locus in adults. Further epigenetic evaluation revealed higher histone lysine 27 trimethylation in monocytes from this adult group. Chromatin immunoprecipitation and RNA pulldown demonstrated association with a novel lncRNA TINA with structurally conserved similarities to the previously recognized epigenetic modifier PARTICLE. Seeking to interpret the epigenetic immunological landscape across three representative age groups, this study focused on HLA-DQA1*01 to expose cytosine and histone methylation alterations and their association with the non-coding transcriptome. Such insights unveil previously unknown complex epigenetic layers, orchestrating the strength and weakening of adaptive immunity with the progression of life.

The Phylogeny, Ontogeny, and Organ-specific Differentiation of Macrophages in the Developing Intestine

Macrophages are large highly motile phagocytic leukocytes that appear early during embryonic development and have been conserved during evolution. The developmental roles of macrophages were first described nearly a century ago, at about the time these cells were being identified as central effectors in phagocytosis and elimination of microbes. Since then, we have made considerable progress in understanding the development of various subsets of macrophages and the diverse roles these cells play in both physiology and disease. This article reviews the phylogeny and the ontogeny of macrophages with a particular focus on the gastrointestinal tract, and the role of these mucosal macrophages in immune surveillance, innate immunity, homeostasis, tissue remodeling, angiogenesis, and repair of damaged tissues. We also discuss the importance of these macrophages in the inflammatory changes in neonatal necrotizing enterocolitis (NEC). This article presents a combination of our own peer-reviewed clinical and preclinical studies, with an extensive review of the literature using the databases PubMed, EMBASE, and Scopus.

Differences in H3K4me3 and chromatin accessibility contribute to altered T-cell receptor signaling in neonatal naïve CD4 T cells

Neonatal CD4+ T cells have reduced or delayed T-cell receptor (TCR) signaling responses compared with adult cells, but the mechanisms underlying this are poorly understood. This study tested the hypothesis that human neonatal naïve CD4+ TCR signaling and activation deficits are related to differences in H3K4me3 patterning and chromatin accessibility. Following initiation of TCR signaling using anti-CD3/anti-CD28 beads, adult naïve CD4+ T cells demonstrated increased CD69, phospho-CD3ε and interleukin (IL)-2, tumor necrosis factor-α (TNF-α), interferon-γ and IL-17A compared with neonatal cells. By contrast, following TCR-independent activation using phorbol myristate acetate (PMA)/ionomycin, neonatal cells demonstrated increased expression of CD69, IL-2 and TNF-α and equivalent phospho-ERK compared with adult cells. H3K4me3 chromatin immunoprecipitation-sequencing (ChIP-seq) and assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) were performed on separate cohorts of naïve CD4+ T cells from term neonates and adults, and RNA-seq data from neonatal and adult naïve CD4+ T cells were obtained from the Blueprint Consortium. Adult cells demonstrated overall increased chromatin accessibility and a higher proportion of H3K4me3 sites associated with open chromatin and active gene transcription compared with neonatal cells. Adult cells demonstrated increased mRNA expression of the TCR-associated genes FYN, ITK, CD4, LCK and LAT, which was associated with increased H3K4me3 at the FYN and ITK gene loci and increased chromatin accessibility at the CD4, LCK and LAT loci. These findings indicate that neonatal TCR-dependent defects in activation are epigenetically regulated and provide a potentially targetable mechanism to enhance neonatal CD4+ T-cell responses.

Epigenetics-mediated pathological alternations and their potential in antiphospholipid syndrome diagnosis and therapy

APS (antiphospholipid syndrome) is a systematic autoimmune disease accompanied with venous or arterial thrombosis and poor pregnant manifestations, partly attributing to the successive elevated aPL (antiphospholipid antibodies) and provoked prothrombotic and proinflammatory molecules production. Nowadays, most researches focus on the laboratory detection and clinic features of APS, but its precise etiology remains to be deeply explored. As we all know, the dysfunction of ECs (endothelial cells), monocytes, platelets, trophoblasts and neutrophils are key contributors to APS progression. Especially, their epigenetic variations, mainly including the promoter CpGs methylation, histone PTMs (post-translational modifications) and ncRNAs (noncoding RNAs), result in genes expression or silence engaged in inflammation initiation, thrombosis formation, autoimmune activation and APOs (adverse pregnancy outcomes) in APS. Given the potential of epigenetic markers serving as diagnostic biomarkers or therapeutic targets of APS, and the encouraging advancements in epigenetic drugs are being made. In this review, we would systematically introduce the epigenetic underlying mechanisms for APS progression, comprehensively elucidate the functional mechanisms of epigenetics in boosting ECs, monocytes, platelets, trophoblasts and neutrophils. Lastly, the application of epigenetic alterations for probing novel diagnostic, specific therapeutic and prognostic strategies would be proposed.

Genetic and epigenetic mechanisms influencing acute to chronic postsurgical pain transitions in pediatrics: Preclinical to clinical evidence

Background

Chronic postsurgical pain (CPSP) in children remains an important problem with no effective preventive or therapeutic strategies. Recently, genomic underpinnings explaining additional interindividual risk beyond psychological factors have been proposed.

Aims

We present a comprehensive review of current preclinical and clinical evidence for genetic and epigenetic mechanisms relevant to pediatric CPSP.

Methods

Narrative review.

Results

Animal models are relevant to translational research for unraveling genomic mechanisms. For example, Cacng2, p2rx7, and bdnf mutant mice show altered mechanical hypersensitivity to injury, and variants of the same genes have been associated with CPSP susceptibility in humans; similarly, differential DNA methylation (H1SP) and miRNAs (miR-96/7a) have shown translational implications. Animal studies also suggest that crosstalk between neurons and immune cells may be involved in nociceptive priming observed in neonates. In children, differential DNA methylation in regulatory genomic regions enriching GABAergic, dopaminergic, and immune pathways, as well as polygenic risk scores for enhanced prediction of CPSP, have been described. Genome-wide studies in pediatric CPSP are scarce, but pathways identified by adult gene association studies point to potential common mechanisms.

Conclusions

Bench-to-bedside genomics research in pediatric CPSP is currently limited. Reverse translational approaches, use of other -omics, and inclusion of pediatric/CPSP endophenotypes in large-scale biobanks may be potential solutions. Time of developmental vulnerability and longitudinal genomic changes after surgery warrant further investigation. Emergence of promising precision pain management strategies based on gene editing and epigenetic programing emphasize need for further research in pediatric CPSP-related genomics.

Epigenetic regulation of pediatric and neonatal immune responses

Epigenetic regulation of transcription is a collective term that refers to mechanisms known to regulate gene transcription without changing the underlying DNA sequence. These mechanisms include DNA methylation and histone tail modifications which influence chromatin accessibility, and microRNAs that act through post-transcriptional gene silencing. Epigenetics is known to regulate a variety of biological processes, and the role of epigtenetics in immunity and immune-mediated diseases is becoming increasingly recognized. While DNA methylation is the most widely studied, each of these systems play an important role in the development and maintenance of appropriate immune responses. There is clear evidence that epigenetic mechanisms contribute to developmental stage-specific immune responses in a cell-specific manner. There is also mounting evidence that prenatal exposures alter epigenetic profiles and subsequent immune function in exposed offspring. Early life exposures that are associated with poor long-term health outcomes also appear to impact immune specific epigenetic patterning. Finally, each of these epigenetic mechanisms contribute to the pathogenesis of a wide variety of diseases that manifest during childhood. This review will discuss each of these areas in detail. IMPACT: Epigenetics, including DNA methylation, histone tail modifications, and microRNA expression, dictate immune cell phenotypes. Epigenetics influence immune development and subsequent immune health. Prenatal, perinatal, and postnatal exposures alter immune cell epigenetic profiles and subsequent immune function. Numerous pediatric-onset diseases have an epigenetic component. Several successful strategies for childhood diseases target epigenetic mechanisms.

Role of Maternal Infections and Inflammatory Responses on Craniofacial Development

Pregnancy is a tightly regulated immunological state. Mild environmental perturbations can affect the developing fetus significantly. Infections can elicit severe immunological cascades in the mother's body as well as the developing fetus. Maternal infections and resulting inflammatory responses can mediate epigenetic changes in the fetal genome, depending on the developmental stage. The craniofacial development begins at the early stages of embryogenesis. In this review, we will discuss the immunology of pregnancy and its responsive mechanisms on maternal infections. Further, we will also discuss the epigenetic effects of pathogens, their metabolites and resulting inflammatory responses on the fetus with a special focus on craniofacial development. Understanding the pathophysiological mechanisms of infections and dysregulated inflammatory responses during prenatal development could provide better insights into the origins of craniofacial birth defects.

Cord-Blood-Derived Professional Antigen-Presenting Cells: Functions and Applications in Current and Prospective Cell Therapies

Human umbilical cord blood (UCB) represents a valuable source of hematopoietic stem cells, particularly for patients lacking a matching donor. UCB provides practical advantages, including a lower risk of graft-versus-host-disease and permissive human leukocyte antigen mismatching. These advantageous properties have so far been applied for stem cell, mesenchymal stromal cell, and chimeric antigen receptor T cell therapies. However, UCB-derived professional antigen-presenting cells are increasingly being utilized in the context of immune tolerance and regenerative therapy. Here, we review the cell-specific characteristics as well as recent advancements in UCB-based cell therapies focusing on dendritic cells, monocytes, B lymphocytes, innate lymphoid cells, and macrophages.

Metabolic Flexibility Assists Reprograming of Central and Peripheral Innate Immunity During Neurodevelopment

Central innate immunity assists time-dependent neurodevelopment by recruiting and interacting with peripheral immune cells. Microglia are the major player of central innate immunity integrating peripheral signals arising from the circumventricular regions lacking the blood-brain barrier (BBB), via neural afferent pathways such as the vagal nerve and also by choroid plexus into the brain ventricles. Defective and/or unrestrained activation of central and peripheral immunity during embryonic development might set an aberrant connectome establishment and brain function, leading to major psychiatric disorders in postnatal stages. Molecular candidates leading to central and peripheral innate immune overactivation identified metabolic substrates and lipid species as major contributors of immunological priming, supporting the role of a metabolic flexibility node during trained immunity. Mechanistically, trained immunity is established by an epigenetic program including DNA methylation and histone acetylation, as the major molecular epigenetic signatures to set immune phenotypes. By definition, immunological training sets reprogramming of innate immune cells, enhancing or repressing immune responses towards a second challenge which potentially might contribute to neurodevelopment disorders. Notably, the innate immune training might be set during pregnancy by maternal immune activation stimuli. In this review, we integrate the most valuable scientific evidence supporting the role of metabolic cues assisting metabolic flexibility, leading to innate immune training during development and its effects on aberrant neurological phenotypes in the offspring. We also add reports supporting the role of methylation and histone acetylation signatures as a major epigenetic mechanism regulating immune training.

Neurobehavioral outcomes in young adults with perinatally acquired HIV

BACKGROUND

With combination antiretroviral therapy (cART), infants with perinatally acquired HIV (pHIV) are living into adolescence and adulthood. Worldwide, many have not received cART in the first years of life, and challenges of adolescence complicate transition to adulthood. Neurobehavioral outcomes in pHIV young adults (pHIVAd) are infrequently reported.

OBJECTIVES

To examine neurobehavioral characteristics of pHIVAd ages 21-30 years, and to compare them with age-matched young adults infected in the second or third decade of life (HIVagematch), and older adults with similar duration HIV disease (HIVOA).

METHODS

A comprehensive neuropsychological test battery and questionnaires to determine cognitive function and mood, and reviews of neuromedical and behavioral records were undertaken in three groups of 13 individuals each. Descriptive analysis and bivariate techniques were used for comparisons.

RESULTS

Rates of cognitive impairment were highest in pHIVAd (85%) compared with HIVagematch (38%) and HIVOA (62%). pHIVAd had the worst scores in global cognition, speed of information processing, working memory, and verbal fluency (0.5--1.0 SD below other groups). There was a trend for higher rates of psychiatric dysfunction (predominantly mood disorders) in pHIVAd (85%) compared with HIV-agematch (46%) and HIVOA (54%). Only four pHIVAd reported employment or enrollment in school. Four had autoimmune disorders.

CONCLUSION

These pHIVAd displayed high rates of cognitive, psychiatric, and autoimmune dysfunction, greater than age-matched or HIV duration-matched comparators. Although this small study is largely descriptive in nature, it suggests that a lack of cART in early life may result in long-term neurobehavioral and immune abnormalities manifesting into adulthood.

Neonatal monocytes demonstrate impaired homeostatic extravasation into a microphysiological human vascular model

Infections are most frequent at the extremes of life, especially among newborns, reflecting age-specific differences in immunity. Monocytes maintain tissue-homeostasis and defence-readiness by escaping circulation in the absence of inflammation to become tissue-resident antigen presenting cells in vivo. Despite equivalent circulating levels, neonates demonstrate lower presence of monocytes inside peripheral tissues as compared to adults. To study the ability of monocytes to undergo autonomous transendothelial extravasation under biologically accurate circumstances we engineered a three-dimensional human vascular-interstitial model including collagen, fibronectin, primary endothelial cells and autologous untreated plasma. This microphysiological tissue construct enabled age-specific autonomous extravasation of monocytes through a confluent human endothelium in the absence of exogenous chemokines and activation. Both CD16- and CD16+ newborn monocytes demonstrated lower adherence and extravasation as compared to adults. In contrast, pre-activated tissue constructs were colonized by newborn monocytes at the same frequency than adult monocytes, suggesting that neonatal monocytes are capable of colonizing inflamed tissues. The presence of autologous plasma neither improved newborn homeostatic extravasation nor shaped age-specific differences in endothelial cytokines that could account for this impairment. Newborn monocytes demonstrated significantly lower surface expression of CD31 and CD11b, and mechanistic experiments using blocking antibodies confirmed a functional role for CD31 and CD54 in neonatal homeostatic extravasation. Our data suggests that newborn monocytes are intrinsically impaired in extravasation through quiescent endothelia, a phenomenon that could contribute to the divergent immune responsiveness to vaccines and susceptibility to infection observed during early life.

The Role of Iron in the Susceptibility of Neonatal Mice to Escherichia coli K1 Sepsis

Sepsis from Escherichia coli expressing the K1 antigen is a leading cause of death in neonates. In a murine model, E. coli K1 grew rapidly in the peritoneal cavity of neonatal mice, causing fatal disease. In contrast, adult mice cleared the infection. Neonatal mice mounted a rapid and equivalent antimicrobial immune response compared to adult mice. Interestingly, peritoneal fluid from neonatal mice contained significantly more total iron than that of adult mice, which was sufficient to support enhanced E. coli growth. Transient iron overload in adult mice infected with E. coli resulted in 100% mortality. Maternal diet-induced mild iron deficiency decreased offspring peritoneal iron, decreased bacterial growth, and conferred protection against sepsis. Taken together, neonatal susceptibility to E. coli K1 sepsis is enhanced by a localized excess of peritoneal iron that allows for unchecked bacterial growth. Targeting this excess iron may provide a new therapeutic target in human patients.

Advantages and Limitations of the Neonatal Immune System

During early post-natal life, neonates must adjust to the transition from the sheltered intra-uterine environment to the microbe-laden external world, wherein they encounter a constellation of antigens and the colonization by the microbiome. At this vulnerable stage, neonatal immune responses are considered immature and present significant differences to those of adults. Pertinent to innate immunity, functional and quantitative deficiencies in antigen-presenting cells and phagocytes are often documented. Exposure to environmental antigens and microbial colonization is associated with epigenetic immune cell reprogramming and activation of effector and regulatory mechanisms that ensure age-depended immune system maturation and prevention of tissue damage. Moreover, neonatal innate immune memory has emerged as a critical mechanism providing protection against infectious agents. Still, in neonates, inexperience to antigenic exposure, along with enhancement of tissue-protective immunosuppressive mechanisms are often associated with severe immunopathological conditions, including sepsis and neurodevelopmental disorders. Despite significant advances in the field, adequate vaccination in newborns is still in its infancy due to elemental restrictions associated also with defective immune responses. In this review, we provide an overview of neonatal innate immune cells, highlighting phenotypic and functional disparities with their adult counterparts. We also discuss the effects of epigenetic modifications and microbial colonization on the regulation of neonatal immunity. A recent update on mechanisms underlying dysregulated neonatal innate immunity and linked infectious and neurodevelopmental diseases is provided. Understanding of the mechanisms that augment innate immune responsiveness in neonates may facilitate the development of improved vaccination protocols that can protect against pathogens and organ damage.

Upregulation of H3K27 Demethylase KDM6 During Respiratory Syncytial Virus Infection Enhances Proinflammatory Responses and Immunopathology

Severe disease following respiratory syncytial virus (RSV) infection has been linked to enhanced proinflammatory cytokine production that promotes a Th2-type immune environment. Epigenetic regulation in immune cells following viral infection plays a role in the inflammatory response and may result from upregulation of key epigenetic modifiers. In this study, we show that RSV-infected bone marrow-derived dendritic cells (BMDC) as well as pulmonary dendritic cells (DC) from RSV-infected mice upregulated the expression of Kdm6b/Jmjd3 and Kdm6a/Utx, H3K27 demethylases. KDM6-specific chemical inhibition (GSK J4) in BMDC led to decreased production of chemokines and cytokines associated with the inflammatory response during RSV infection (i.e., CCL-2, CCL-3, CCL-5, IL-6) as well as decreased MHC class II and costimulatory marker (CD80/86) expression. RSV-infected BMDC treated with GSK J4 altered coactivation of T cell cytokine production to RSV as well as a primary OVA response. Airway sensitization of naive mice with RSV-infected BMDCs exacerbate a live challenge with RSV infection but was inhibited when BMDCs were treated with GSK J4 prior to sensitization. Finally, in vivo treatment with the KDM6 inhibitor, GSK J4, during RSV infection reduced inflammatory DC in the lungs along with IL-13 levels and overall inflammation. These results suggest that KDM6 expression in DC enhances proinflammatory innate cytokine production to promote an altered Th2 immune response following RSV infection that leads to more severe immunopathology.

Impact of pregravid obesity on maternal and fetal immunity: Fertile grounds for reprogramming

Maternal pregravid obesity results in several adverse health outcomes during pregnancy, including increased risk of gestational diabetes, preeclampsia, placental abruption, and complications at delivery. Additionally, pregravid obesity and in utero exposure to high fat diet have been shown to have detrimental effects on fetal programming, predisposing the offspring to adverse cardiometabolic, endocrine, and neurodevelopmental outcomes. More recently, a deeper appreciation for the modulation of offspring immunity and infectious disease-related outcomes by maternal pregravid obesity has emerged. This review will describe currently available animal models for studying the impact of maternal pregravid obesity on fetal immunity and review the data from clinical and animal model studies. We also examine the burden of pregravid obesity on the maternal-fetal interface and the link between placental and systemic inflammation. Finally, we discuss future studies needed to identify key mechanistic underpinnings that link maternal inflammatory changes and fetal cellular reprogramming events.

Age-Dependent Effects of Immunoproteasome Deficiency on Mouse Adenovirus Type 1 Pathogenesis

Acute respiratory infection with mouse adenovirus type 1 (MAV-1) induces activity of the immunoproteasome, an inducible form of the proteasome that shapes CD8 T cell responses by enhancing peptide presentation by major histocompatibility complex (MHC) class I. We used mice deficient in all three immunoproteasome subunits (triple-knockout [TKO] mice) to determine whether immunoproteasome activity is essential for control of MAV-1 replication or inflammatory responses to acute infection. Complete immunoproteasome deficiency in adult TKO mice had no effect on MAV-1 replication, virus-induced lung inflammation, or adaptive immunity compared to C57BL/6 (B6) controls. In contrast, immunoproteasome deficiency in neonatal TKO mice was associated with decreased survival and decreased lung gamma interferon (IFN-γ) expression compared to B6 controls, although without substantial effects on viral replication, histological evidence of inflammation, or expression of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-1β in lungs or other organs. T cell recruitment and IFN-γ production was similar in lungs of infected B6 and TKO mice. In lungs of uninfected B6 mice, we detected low levels of immunoproteasome subunit mRNA and protein that increased with age. Immunoproteasome subunit expression was lower in lungs of adult IFN-γ-deficient mice compared to B6 controls. Together, these results demonstrate developmental regulation of the immunoproteasome that is associated with age-dependent differences in MAV-1 pathogenesis.IMPORTANCE MAV-1 infection is a useful model to study the pathogenesis of an adenovirus in its natural host. Host factors that control MAV-1 replication and contribute to inflammation and disease are not fully understood. The immunoproteasome is an inducible component of the ubiquitin proteasome system that shapes the repertoire of peptides presented by MHC class I to CD8 T cells, influences other aspects of T cell survival and activation, and promotes production of proinflammatory cytokines. We found that immunoproteasome activity is dispensable in adult mice. However, immunoproteasome deficiency in neonatal mice increased mortality and impaired IFN-γ responses in the lungs. Baseline immunoproteasome subunit expression in lungs of uninfected mice increased with age. Our findings suggest the existence of developmental regulation of the immunoproteasome, like other aspects of host immune function, and indicate that immunoproteasome activity is a critical protective factor early in life.

Robust health-score based survival prediction for a neonatal mouse model of polymicrobial sepsis

Infectious disease and sepsis represent a serious problem for all, but especially in early life. Much of the increase in morbidity and mortality due to infection in early life is presumed to relate to fundamental differences between neonatal and adult immunity. Mechanistic insight into the way newborns' immune systems handle infectious threats is lacking; as a result, there has only been limited success in providing effective immunomodulatory interventions to reduce infectious mortality. Given the complexity of the host-pathogen interactions, neonatal mouse models can offer potential avenues providing valuable data. However, the small size of neonatal mice hampers the ability to collect biological samples without sacrificing the animals. Further, the lack of a standardized metric to quantify newborn mouse health increases reliance on correlative biomarkers without a known relationship to 'clinical' outcome. To address this bottleneck, we developed a system that allows assessment of neonatal mouse health in a readily standardized and quantifiable manner. The resulting health scores require no special equipment or sample collection and can be assigned in less than 20 seconds. Importantly, the health scores are highly predictive of survival. A classifier built on our health score revealed a positive relationship between reduced bacterial load and survival, demonstrating how this scoring system can be used to bridge the gap between assumed relevance of biomarkers and the clinical outcome of interest. Adoption of this scoring system will not only provide a robust metric to assess health of newborn mice but will also allow for objective, prospective studies of infectious disease and possible interventions in early life.

Early Life Respiratory Syncytial Virus Infection and Asthmatic Responses

The infant's developing immune response is central to establishing a balanced system that reacts appropriately to infectious stimuli, but does not induce altered disease states with potential long-term sequelae. Respiratory syncytial virus may alter the immune system, affecting future responses. Early infection may have direct effects on the lung itself. Other early life processes contribute to the development of immune responses including assembly of the microbiome, which seems to have a particularly important role for establishing the immune environment. This review covers studies that have set up important paradigms and discusses recent data that direct research toward informative hypotheses.

Chorioamnionitis exposure remodels the unique histone modification landscape of neonatal monocytes and alters the expression of immune pathway genes

Chorioamnionitis is an intrauterine infection involving inflammation of the chorion, amnion, and placenta. It leads to a fetal systemic inflammatory response that can alter the transcription of neonatal immune genes. We have previously shown that neonatal monocytes gain the activating histone tail modification H3K4me3 at promoter sites of immunologically important genes as development progresses from preterm neonate to adult. In this study, we applied ChIP-seq and RNA-seq to evaluate the impact of chorioamnionitis on the neonatal monocyte H3K4me3 histone modification landscape over the course of fetal and neonatal immune system development. Chorioamnionitis exposure in neonatal monocytes resulted in a net increase in total monocyte H3K4me3, primarily in introns and intergenic regions. Immune gene expression was decreased in chorioamnionitis-exposed monocytes, with the majority of enriched transcripts falling into pathways that are not linked to the immune system. Over half of all neonatal monocyte H3K4me3 peaks, independent of their location, were associated with active gene transcription. Overall, chorioamnionitis exposure resulted in the global remodeling of the neonatal monocyte H3K4me3 landscape and changes in the expression of known immune genes. These changes resulted in a less robust inflammatory response upon exposure to a secondary challenge, which may explain why chorioamnionitis-exposed neonates have an increased risk of sepsis. DATABASE: ChIP-seq data for U30/O30/Term: GEO GSE81957 ChIP-seq data for U30C/O30C/TermC: GEO GSE111873 RNA-seq data for U/L/CU/CL: GEO GSE111927.

Influence of Immunological Maturity on Respiratory Syncytial Virus-Induced Morbidity in Young Children

Respiratory syncytial virus (RSV) is a very frequent viral respiratory pathogen of the young (<5 years old) with a significant portion of young toddlers having been infected before 2 years of age. Although we understand that some of the morbidity associated with RSV in neonates is due to immunological maturation that favors immunosuppression over antiviral innate and/or adaptive immune responses, the rapid development of the immune system right after birth suggests that each age group (newborn, early infant, older infant, toddler, and older) may respond to the virus in different ways. In this study, we summarize the morbidity associated with infection in young children in the context of immunological maturation of monocytes/macrophages and the ramifications for poor innate control of viral pathogenesis. We also summarize key mechanisms that contribute to the diminished antiviral innate immune responses of these young children.

Deubiquitinase Mysm1 regulates macrophage survival and polarization

Macrophages play pivotal roles in innate and adaptive immune response, tissue homeostasis and cancer development. Their development and heterogeneity are tightly controlled by epigenetic program and transcription factors. Deubiquitinase Mysm1 plays crucial roles in regulating stem cell maintenance and immune cell development. Here we show that Mysm1 expression is up regulated during bone marrow macrophage development. Mysm1 deficient cells exhibit accelerating proliferation with more cells going to S phase and higher cyclin D1, cyclin D2 and c-Myc expression. However, compared to WT counterparts, more cell death is also detected in Mysm1 deficient cells no matter M-CSF deprived or not. In LPS-condition medium, Mysm1^-/- macrophages show more pro-inflammatory factors IL-1β, TNFα and iNOS production. In addition, much higher expression of surface marker CD86 is detected in Mysm1^-/- macrophages. In vivo tumor model data demonstrate that in contrast to WT macrophages promoting tumor growth, Mysm1^-/- macrophages inhibit tumor growth, showing the properties of M1 macrophages. Collectively, these data indicate that Mysm1 is essential for macrophage survival and plays an important role in macrophage polarization and might be a target for cell therapy.

Exposure to chorioamnionitis alters the monocyte transcriptional response to the neonatal pathogen Staphylococcus epidermidis

Preterm infants are uniquely susceptible to late-onset sepsis that is frequently caused by the skin commensal Staphylococcus epidermidis. Innate immune responses, particularly from monocytes, are a key protective mechanism. Impaired cytokine production by preterm infant monocytes is well described, but few studies have comprehensively assessed the corresponding monocyte transcriptional response. Innate immune responses in preterm infants may be modulated by inflammation such as prenatal exposure to histologic chorioamnionitis which complicates 40-70% of preterm pregnancies. Chorioamnionitis alters the risk of late-onset sepsis, but its effect on monocyte function is largely unknown. Here, we aimed to determine the impact of exposure to chorioamnionitis on the proportions and phenotype of cord blood monocytes using flow cytometry, as well as their transcriptional response to live S. epidermidis. RNA-seq was performed on purified cord blood monocytes from very preterm infants (<32 weeks gestation, with and without chorioamnionitis-exposure) and term infants (37-40 weeks), pre- and postchallenge with live S. epidermidis. Preterm monocytes from infants without chorioamnionitis-exposure did not exhibit an intrinsically deficient transcriptional response to S. epidermidis compared to term infants. In contrast, chorioamnionitis-exposure was associated with hypo-responsive transcriptional phenotype regarding a subset of genes involved in antigen presentation and adaptive immunity. Overall, our findings suggest that prenatal exposure to inflammation may alter the risk of sepsis in preterm infants partly by modulation of monocyte responses to pathogens.

Factors Affecting the Immunity to Respiratory Syncytial Virus: From Epigenetics to Microbiome

Respiratory syncytial virus (RSV) is a common pathogen that infects virtually all children by 2 years of age and is the leading cause of hospitalization of infants worldwide. While most children experience mild symptoms, some children progress to severe lower respiratory tract infection. Those children with severe disease have a much higher risk of developing childhood wheezing later in life. Many risk factors are known to result in exacerbated disease, including premature birth and early age of RSV infection, when the immune system is relatively immature. The development of the immune system before and after birth may be altered by several extrinsic and intrinsic factors that could lead to severe disease predisposition in children who do not exhibit any currently known risk factors. Recently, the role of the microbiome and the resulting metabolite profile has been an area of intense study in the development of lung disease, including viral infection and asthma. This review explores both known risk factors that can lead to severe RSV-induced disease as well as emerging topics in the development of immunity to RSV and the long-term consequences of severe infection.

Cutting Edge: Plasmodium falciparum Induces Trained Innate Immunity

Malarial infection in naive individuals induces a robust innate immune response. In the recently described model of innate immune memory, an initial stimulus primes the innate immune system to either hyperrespond (termed training) or hyporespond (tolerance) to subsequent immune challenge. Previous work in both mice and humans demonstrated that infection with malaria can both serve as a priming stimulus and promote tolerance to subsequent infection. In this study, we demonstrate that initial stimulation with Plasmodium falciparum-infected RBCs or the malaria crystal hemozoin induced human adherent PBMCs to hyperrespond to subsequent ligation of TLR2. This hyperresponsiveness correlated with increased H3K4me3 at important immunometabolic promoters, and these epigenetic modifications were also seen in Kenyan children naturally infected with malaria. However, the use of epigenetic and metabolic inhibitors indicated that the induction of trained immunity by malaria and its ligands may occur via a previously unrecognized mechanism(s).

Histone methylation is critical in monocyte to macrophage differentiation

Monocyte derived macrophages contribute to many human diseases, and a prescribed set of transcription factors control the differentiation of monocytes into macrophages. In this issue of The FEBS Journal, Jin and colleagues demonstrate that histone methylation changes in monocytes alter chromatin structure and ultimately direct the expression of numerous transcription factors crucial in this differentiation process.