Intracellular cytokine production by fetal and adult monocytes

Chemokines, soluble PD-L1, and immune cell hyporesponsiveness are distinct features of SARS-CoV-2 critical illness

Critically ill patients manifest many of the same immune features seen in coronavirus disease 2019 (COVID-19), including both "cytokine storm" and "immune suppression." However, direct comparisons of molecular and cellular profiles between contemporaneously enrolled critically ill patients with and without severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are limited. We sought to identify immune signatures specifically enriched in critically ill patients with COVID-19 compared with patients without COVID-19. We enrolled a multisite prospective cohort of patients admitted under suspicion for COVID-19, who were then determined to be SARS-CoV-2-positive (n = 204) or -negative (n = 122). SARS-CoV-2-positive patients had higher plasma levels of CXCL10, sPD-L1, IFN-γ, CCL26, C-reactive protein (CRP), and TNF-α relative to SARS-CoV-2-negative patients adjusting for demographics and severity of illness (Bonferroni P value < 0.05). In contrast, the levels of IL-6, IL-8, IL-10, and IL-17A were not significantly different between the two groups. In SARS-CoV-2-positive patients, higher plasma levels of sPD-L1 and TNF-α were associated with fewer ventilator-free days (VFDs) and higher mortality rates (Bonferroni P value < 0.05). Lymphocyte chemoattractants such as CCL17 were associated with more severe respiratory failure in SARS-CoV-2-positive patients, but less severe respiratory failure in SARS-CoV-2-negative patients (P value for interaction < 0.01). Circulating T cells and monocytes from SARS-CoV-2-positive subjects were hyporesponsive to in vitro stimulation compared with SARS-CoV-2-negative subjects. Critically ill SARS-CoV-2-positive patients exhibit an immune signature of high interferon-induced lymphocyte chemoattractants (e.g., CXCL10 and CCL17) and immune cell hyporesponsiveness when directly compared with SARS-CoV-2-negative patients. This suggests a specific role for T-cell migration coupled with an immune-checkpoint regulatory response in COVID-19-related critical illness.

Frank Beach Award Winner - The future of mental health research: Examining the interactions of the immune, endocrine and nervous systems between mother and infant and how they affect mental health

Pregnancy and the postpartum period are periods of significant change in the immune and endocrine systems. This period of life is also associated with an increased risk of mental health disorders in the mother, and an increased risk of developmental and neuropsychiatric disorders in her infant. The collective data described here supports the idea that peripartum mood disorders in mother and developmental disorders in her infant likely reflects multiple pathogeneses, stemming from various interactions between the immune, endocrine and nervous systems, thereby resulting in various symptom constellations. In this case, testing the mechanisms underlying specific symptoms of these disorders (e.g. deficits in specific types of learning or anhedonia) may provide a better understanding of the various physiological interactions and multiple etiologies that most likely underlie the risk of mental health disorders during this unique time in life. The goal here is to summarize the current understanding of how immune and endocrine factors contribute to maternal mental health, while simultaneously understanding the impact these unique interactions have on the developing brain of her infant.

Innate immunity of the human newborn: distinct cytokine responses to LPS and other Toll-like receptor agonists

Human newborns are at increased risk of microbial invasion and display diminished responses to many vaccines indicating a functional immaturity of the immune system at birth. Such altered immune reactivity may reflect the demands of in utero existence, including the need to avoid potentially harmful inflammatory immune reactions. Despite normal basal expression of Toll-like receptors and membrane CD14, innate immune responses of neonatal mononuclear cells to lipopolysaccharide are characterized by markedly reduced release of the pro-inflammatory Th1-polarizing cytokines TNF-α and interferon-γ with relative preservation of anti-inflammatory Th2-polarizing cytokines. Differences between newborns and adults with respect to TLR-induced TNF-α release extend to a range of TLR agonists, including bacterial lipopeptides, and are due to differences in soluble factors present in blood plasma. Soluble factors in neonatal blood plasma suppress TLR-induced TNF-α release from monocytes and efforts to identify and characterize these inhibitors are on-going. Such altered immunity to TLR agonists is likely to alter both innate and adaptive immune responses in newborns profoundly. Definition of the mechanisms underlying distinct neonatal immunity promises to identify novel ways to prevent and treat infection in this relatively high-risk population.

Impaired NK cell antiviral cytokine response against influenza virus in small-for-gestational-age neonates

The neonates, particularly small-for-gestational-age (SGA) ones, are susceptible to various microbial infections. Natural killer (NK) cells are critical components of host innate immunity system and the main source of the inflammatory cytokines, which provide critical protection during the early phase of viral infections before the development of an appropriate adaptive immune response. However, little is known about the antiviral effects of NK cells in neonates especially the SGA population. Herein, a prospective descriptive study was performed to determine the differences of NK cell immunity among adults, appropriate-for gestational-age (AGA) and SGA neonates. Adults have much higher NK cell number in peripheral blood than that in cord blood from neonates. In response to influenza virus stimulation, neonatal NK cells, especially SGA baby cells, expressed significantly lower antiviral cytokines including perforin, interferon (IFN)-γ and tumor-necrosis factor (TNF)-α responses than adult NK cells. In addition, the antiviral cytokine responses of NK cells were positively correlated with neonatal birth weight. Our data suggested that the depressed antiviral activity and less frequency of NK cells are likely to be responsible for the high susceptibility to microbial infection in neonates, at least in part. Improving the function of innate immunity may provide a new way to defend virus infection.

Transcriptome profiling of hippocampal CA1 after early-life seizure-induced preconditioning may elucidate new genetic therapies for epilepsy

Injury of the CA1 subregion induced by a single injection of kainic acid (1 × KA) in juvenile animals (P20) is attenuated in animals with two prior sustained neonatal seizures on P6 and P9. To identify gene candidates involved in the spatially protective effects produced by early-life conditioning seizures we profiled and compared the transcriptomes of CA1 subregions from control, 1 × KA- and 3 × KA-treated animals. More genes were regulated following 3 × KA (9.6%) than after 1 × KA (7.1%). Following 1 × KA, genes supporting oxidative stress, growth, development, inflammation and neurotransmission were upregulated (e.g. Cacng1, Nadsyn1, Kcng1, Aven, S100a4, GFAP, Vim, Hrsp12 and Grik1). After 3 × KA, protective genes were differentially over-expressed [e.g. Cat, Gpx7, Gad1, Hspa12A, Foxn1, adenosine A1 receptor, Ca(2+) adaptor and homeostasis proteins, Cacnb4, Atp2b2, anti-apoptotic Bcl-2 gene members, intracellular trafficking protein, Grasp and suppressor of cytokine signaling (Socs3)]. Distinct anti-inflammatory interleukins (ILs) not observed in adult tissues [e.g. IL-6 transducer, IL-23 and IL-33 or their receptors (IL-F2 )] were also over-expressed. Several transcripts were validated by real-time polymerase chain reaction (QPCR) and immunohistochemistry. QPCR showed that casp 6 was increased after 1 × KA but reduced after 3 × KA; the pro-inflammatory gene Cox1 was either upregulated or unchanged after 1 × KA but reduced by ~70% after 3 × KA. Enhanced GFAP immunostaining following 1 × KA was selectively attenuated in the CA1 subregion after 3 × KA. The observed differential transcriptional responses may contribute to early-life seizure-induced pre-conditioning and neuroprotection by reducing glutamate receptor-mediated Ca(2+) permeability of the hippocampus and redirecting inflammatory and apoptotic pathways. These changes could lead to new genetic therapies for epilepsy.

Microcirculatory changes in term newborns with suspected infection: an observational prospective study

Background. In adults severely disturbed microcirculatory flow can be observed by Orthogonal Polarized Spectral (OPS) imaging techniques during sepsis. Therefore we set out to assess for microcirculatory changes in term newborns with suspected early onset infection using OPS. Methods. OPS images were obtained prospectively from the vascular bed of the ear conch and upper arm of 47 newborns on their 1st, 2nd, and 3rd day of life. OPS sequences were analyzed semiquantitatively offline and blinded to clinical status of the infant. Flow in vessels was classified as continuous or noncontinuous flow and given as proportion of total vessels per image as in the studies in adults. Results. The proportion of vessels with continuous flow was significantly lower in the infants with infection (69% [56–81] versus 90% [87–94] (P = 0.0003)). None of the infants with infection was in shock or severely septic. Conclusion. In term neonates the microcirculatory flow is impaired in a large proportion of vessels even in mild to moderate infection. These changes can be observed at the onset of disease at the external ear, an optimal site for microcirculatory measurements in term infants.

Attenuated mRNA expression of inflammatory mediators in neonatal rat lung following lipopolysaccharide treatment

Neonates are known to exhibit increased susceptibility to bacterial and viral infections and increasing evidence demonstrates that the increased susceptibility is related to their attenuated immune response to infections. The lung is equipped with an innate defense system involving both cellular and humoral mediators. The present study was performed to characterize the expression of inflammatory mediators in the lung of neonatal rats in comparison with older animals. Rats at postnatal day 1 (P1), P21, and P70 were treated with saline or 0.25 mg/kg lipopolysaccharide (LPS) via intraperitoneal injection. Two hours later, animals were sacrificed and the transcriptional response of key inflammatory mediators and enzyme activity of myeloperoxidase (MPO) in the lung of these animals were examined. LPS-induced messenger RNA (mRNA) expression of pro-inflammatory cytokines, namely interleukin (IL)-1β, IL-6, and tumor necrosis factor-α, antiinflammatory cytokines, namely IL-10 and IL-1 receptor antagonist (IL-1ra), and chemokines, namely macrophage inflammatory protein (MIP)-1β, MIP-2, and monocyte chemotactic protein-1, in P1 lung was much reduced compared to that in P21 and P70 animals at 2 hours postinjection. These data suggest that LPS-induced transcriptional response of cytokines and chemokines was much reduced in P1 lung even though the protein levels of these genes were not ascertained and mRNA levels of these genes may not reflect their final protein levels. MPO activity in LPS-treated P1 lung was also significantly attenuated compared to that in LPS-treated P70 lung, suggesting impaired neutrophil infiltration in P1 lung at 2 hours following LPS treatment. In parallel, the baseline mRNA expression of LPS-binding protein (LBP) in P1 lung was much lower than that in P21 and P70 lungs. While the protein level of LBP was not examined and the mRNA level of LBP may not reflect its final protein level, the reduced transcriptional response of cytokines and chemokines in P1 lung at 2 hours following LPS treatment may be attributed to lower LBP expression in P1 lung as compared to P21 and P70 lungs.

Innate immune deficiency of extremely premature neonates can be reversed by interferon-γ

BACKGROUND

Bacterial sepsis is a major threat in neonates born prematurely, and is associated with elevated morbidity and mortality. Little is known on the innate immune response to bacteria among extremely premature infants.

METHODOLOGY/PRINCIPAL FINDINGS

We compared innate immune functions to bacteria commonly causing sepsis in 21 infants of less than 28 wks of gestational age, 24 infants born between 28 and 32 wks of gestational age, 25 term newborns and 20 healthy adults. Levels of surface expression of innate immune receptors (CD14, TLR2, TLR4, and MD-2) for Gram-positive and Gram-negative bacteria were measured in cord blood leukocytes at the time of birth. The cytokine response to bacteria of those leukocytes as well as plasma-dependent opsonophagocytosis of bacteria by target leukocytes was also measured in the presence or absence of interferon-γ. Leukocytes from extremely premature infants expressed very low levels of receptors important for bacterial recognition. Leukocyte inflammatory responses to bacteria and opsonophagocytic activity of plasma from premature infants were also severely impaired compared to term newborns or adults. These innate immune defects could be corrected when blood from premature infants was incubated ex vivo 12 hrs with interferon-γ.

CONCLUSION/SIGNIFICANCE

Premature infants display markedly impaired innate immune functions, which likely account for their propensity to develop bacterial sepsis during the neonatal period. The fetal innate immune response progressively matures in the last three months in utero. Ex vivo treatment of leukocytes from premature neonates with interferon-γ reversed their innate immune responses deficiency to bacteria. These data represent a promising proof-of-concept to treat premature newborns at the time of delivery with pharmacological agents aimed at maturing innate immune responses in order to prevent neonatal sepsis.

Postnatal development of lipopolysaccharide-induced inflammatory response in the brain

OBJECTIVE

This study aimed to characterize postnatal development of lipopolysaccharide (LPS)-induced inflammatory response in the brain.

METHODS

Postnatal day (P)1, P21 and P70 Sprague-Dawley(®) rats were treated with saline or 0.25 mg/kg LPS for 2 h, and the mRNA expression of neuroinflammatory mediators in the brain was determined using reverse transcriptase-polymerase chain reaction (RT-PCR). The kinetics of LPS-induced neuroinflammatory mediators in the brain of P1 and P21 animals was determined using RT-PCR, and the kinetics of LPS-induced cytokines in the serum were determined using ELISA. The basal levels of Toll-like receptor (TLR)-4, CD14, and myeloid differentiation factor 88 (Myd88) were measured at the mRNA and protein levels using RT-PCR and Western blot assay respectively.

RESULTS

The mRNA expression levels of cytokines and chemokines were considerably increased in P21 and P70 brains but not significantly altered in P1 brain at 2 h following LPS stimulation. Instead, the induction of cytokines and chemokines was significantly delayed in the brain of P1 animals following LPS stimulation, which was associated with diminished Myd88 production in P1 brain. In parallel, the cytokine response in the serum of P1 animals after LPS stimulation was also delayed compared to P21 animals.

CONCLUSIONS

TLR-4-mediated innate immunity in the brain was significantly delayed in P1 animals, and underwent significant development during the early postnatal period.

Role of complement and CD14 in meconium-induced cytokine formation

OBJECTIVE

Meconium aspiration syndrome has a complex, poorly defined pathophysiology. Meconium is a potent activator of complement in vitro and in vivo; the latter is associated with a systemic inflammatory response. The complement system and Toll-like receptors are 2 important upstream components of the innate immune system that act partly independently in the inflammatory network. The aim of this study was to investigate the relative role of complement and CD14 in meconium-induced cytokine production.

METHODS

Human adult (n = 6) and cord whole blood (n = 6) anticoagulated with lepirudin was collected and distributed into tubes that contained inhibitory antibodies (anti-CD14, anti-C2, anti-factor D, or combinations thereof). The tubes were preincubated for 5 minutes before addition of meconium or buffer and then incubated for 4 hours at 37 degrees C. Complement activation was measured by quantification of the terminal sC5b-9 complement complex by enzyme-linked immunosorbent assay. A panel of 27 inflammatory mediators (cytokines, chemokines, and growth factors) was measured by using multiplex technology.

RESULTS

Fourteen of the 27 mediators measured were induced by meconium both in cord and adult blood. In cord blood, 2 additional chemokines were induced and the inflammatory response was, in general, more potent. Blocking of complement or CD14 differentially reduced the formation of most mediators, anti-CD14 being more effective. Notably, the combined inhibition of complement and CD14 almost completely abolished meconium-induced formation of the cytokines and the chemokines and markedly reduced the formation of growth factors. The endogenous lipopolysaccharide content of meconium could not explain the CD14-mediated response.

CONCLUSIONS

Meconium-induced triggering of the cytokine network is differentially mediated by complement and CD14. A combined inhibition of these effector mechanisms may be an alternative approach to reduce the inflammatory reaction in meconium aspiration syndrome.

Cytokine expression in response to bacterial antigens in preterm and term infant cord blood monocytes

BACKGROUND

Neonatal susceptibility to bacterial infection is associated with an immature immune system, but the role of different bacterial antigens in specific responses is largely unknown.

OBJECTIVE

To evaluate differences in intracellular cytokine response to physiologically relevant bacterial antigens in term and preterm infants as compared with adults.

METHODS

Cord blood samples from preterm and term neonates and adult peripheral blood samples were cultured ex vivo with and without whole heat-killed bacteria. Intracellular leukocyte production of interleukin (IL)-6, IL-10, IL-12, and IL-8 responses was assessed by flow cytometry.

RESULTS

Monocytes were the primary producers of all mediators. Escherichia coli was the most potent stimulant. Lactobacillus plantarum 299v activated fewer monocytes as compared with E. coli for all responses (p < 0.05), except for IL-12 in term neonates. IL-6 response to Staphylococcus epidermidis was lower in both groups of neonates as compared with adults (p = 0.023 and p = 0.001). IL-8 response to S. epidermidis was lower in term as compared with preterm neonates and adults (p = 0.003). IL-10 response to group B streptococci was lower in term neonates as compared with adults and higher in preterm as compared with term neonates (p = 0.015).

CONCLUSIONS

Monocytes from term neonates compared to preterm neonates show a downregulated anti-inflammatory response to specific bacteria. High neonatal response to pathogenic E. coli in the preterm infant could cause uncontrolled inflammatory response, while lower IL-6 response to S. epidermidis in neonates may indicate a basis for vulnerability to S. epidermidis infection.

Gene expression profiles of adult peripheral and cord blood mononuclear cells altered by lipopolysaccharide

BACKGROUND

Neonatal Gram-negative sepsis is often characterized by a fulminant clinical course, compared to adults, resulting in higher morbidity and mortality. Genome-wide gene expression analysis can provide insights into the molecular alterations in sepsis.

OBJECTIVES

To evaluate in vitro activation of the neonatal and adult immune system, gene expression patterns were compared in mononuclear cells from cord (CBMNC) and adult peripheral blood (APBMNC).

METHODS

To better understand the influence of early molecular signals on the effects of sepsis, Affymetrix gene profiling (8,475 genes) was done on RNA isolated from CBMNC and APBMNC without and after incubation with 100 ng/ml lipopolysaccharide (LPS).

RESULTS

We demonstrated significant alterations in the expression of 108 CBMNC and APBMNC genes compared with basal levels, 188 significant changes in CBMNC and 97 in APBMNC, including cytokines, chemokines and immunoregulatory genes. Furthermore, we found 5 genes showing a significant interaction effect between cell type and LPS stimulation, including tumor necrosis factor receptor superfamily, member 6 (FAS), absent in melanoma 2, malic enzyme 1, hemoglobin epsilon 1, and trans-prenyltransferase.

CONCLUSIONS

These results provide further support for a marked difference in the pathogenesis of neonatal and adult sepsis and may stimulate additional studies to investigate some of the altered genes as potential new targets for diagnostic tools and therapeutic strategies.

Levels of pro-inflammatory cytokines produced from cord blood in-vitro are pathogen dependent and increased in comparison to adult controls

BACKGROUND

Overproduction of pro-inflammatory cytokines may play a role in increased morbidity and mortality from neonatal sepsis. Objective of this study was to compare secretion of pro-inflammatory cytokines by the cord blood cells of healthy term neonates to the venous blood cells of healthy adults in vitro after stimulation with common neonatal pathogens.

METHOD

Blood samples were cultured in the presence of heat-killed group B beta-hemolytic streptococci (GBS), Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epi). Concentrations of secreted cytokines (interleukine-6, IL-6, tumor necrosis factor-alpha, TNF-alpha, interleukine-1 beta, IL-1beta and interleukine-8, IL-8) were measured after 0, 1, 2 and 4 h of incubation using chemiluminescent immunometric automated assay.

RESULTS

Blood samples from 22 neonates and 16 adults were compared. After stimulation by GBS and E. coli, cord blood cells secreted significantly higher levels of IL-6 and IL-8 than blood cells of healthy adults. In cord blood, E. coli induced secretion of higher concentration of IL-6, TNF-alpha, IL-1beta and IL-8 than S. epi, and more IL-6 than GBS; GBS induced more IL-1beta than S.epi.

CONCLUSIONS

Response of cord blood to microbial activators is different from that of adult controls. Each isolate of heat-killed bacteria induced different amount of pro-inflammatory cytokines in vitro. This may represent a useful in vitro virulence test.

Neonatal B cells suppress innate toll-like receptor immune responses and modulate alloimmunity

It has been known for decades that neonates are susceptible to transplant tolerance, but the immunological mechanisms involved remain to be fully elucidated. Recent evidence indicates that the maturation state of DCs responding to an allograft may have a profound impact on whether immunity or tolerance ensues. Given that TLR activation is a key process leading to DC maturation, we hypothesized that DCs from neonates have defective TLR immune responses. Contrary to our hypothesis, we found that murine neonatal DCs demonstrated enhanced TLR responses in comparison to adult counterparts in vitro. However, we found that neonatal B cells possess unique immunoregulatory functions as they impaired DC responses to TLR activation in an IL-10-dependent fashion. Functionally, we demonstrated that TLR-activated neonatal, but not adult, B cells impaired Th1, but not Th2, T cell alloimmune responses in vitro and in vivo, in models of alloimmune priming and allotransplantation. We conclude that neonatal B cells possess unique immunoregulatory properties that inhibit DC function and modulate alloimmunity in our murine experimental systems.