Concentrations of main serum opsonins in early infancy

An IL-10/DEL-1 axis supports granulopoiesis and survival from sepsis in early life

The limited reserves of neutrophils are implicated in the susceptibility to infection in neonates, however the regulation of neutrophil kinetics in infections in early life remains poorly understood. Here we show that the developmental endothelial locus (DEL-1) is elevated in neonates and is critical for survival from neonatal polymicrobial sepsis, by supporting emergency granulopoiesis. Septic DEL-1 deficient neonate mice display low numbers of myeloid-biased multipotent and granulocyte-macrophage progenitors in the bone marrow, resulting in neutropenia, exaggerated bacteremia, and increased mortality; defects that are rescued by DEL-1 administration. A high IL-10/IL-17A ratio, observed in newborn sepsis, sustains tissue DEL-1 expression, as IL-10 upregulates while IL-17 downregulates DEL-1. Consistently, serum DEL-1 and blood neutrophils are elevated in septic adult and neonate patients with high serum IL-10/IL-17A ratio, and mortality is lower in septic patients with high serum DEL-1. Therefore, IL-10/DEL-1 axis supports emergency granulopoiesis, prevents neutropenia and promotes sepsis survival in early life.

Dysregulated monocyte-derived macrophage response to Group B Streptococcus in newborns

Introduction

Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading pathogen of neonatal sepsis. The host-pathogen interactions underlying the progression to life-threatening infection in newborns are incompletely understood. Macrophages are first line in host defenses against GBS, contributing to the initiation, amplification, and termination of immune responses. The goal of this study was to compare the response of newborn and adult monocyte-derived macrophages (MDMs) to GBS.

Methods

Monocytes from umbilical cord blood of healthy term newborns and from peripheral blood of healthy adult subjects were cultured with M-CSF to induce MDMs. M-CSF-MDMs, GM-CSF- and IFNγ-activated MDMs were exposed to GBS COH1, a reference strain for neonatal sepsis.

Results

GBS induced a greater release of IL-1β, IL-6, IL-10, IL-12p70 and IL-23 in newborn compared to adult MDMs, while IL-18, IL-21, IL-22, TNF, RANTES/CCL5, MCP-1/CCL2 and IL-8/CXCL8 were released at similar levels. MDM responses to GBS were strongly influenced by conditions of activation and were distinct from those to synthetic bacterial lipopeptides and lipopolysaccharides. Under similar conditions of opsonization, newborn MDMs phagocytosed and killed GBS as efficiently as adult MDMs.

Discussion

Altogether, the production of excessive levels of Th1- (IL-12p70), Th17-related (IL-1β, IL-6, IL-23) and anti-inflammatory (IL-10) cytokines is consistent with a dysregulated response to GBS in newborns. The high responsiveness of newborn MDMs may play a role in the progression of GBS infection in newborns, possibly contributing to the development of life-threatening organ dysfunction.

Effects of Sepsis on Immune Response, Microbiome and Oxidative Metabolism in Preterm Infants

This is a narrative review about the mechanisms involved in bacterial sepsis in preterm infants, which is an illness with a high incidence, morbidity, and mortality. The role of the innate immune response and its relationship with oxidative stress in the pathogenesis are described as well as their potential implementation as early biomarkers. Moreover, we address the impact that all the mechanisms triggered by sepsis have on the dysbiosis and the changes on neonatal microbiota.

Infection prevention for extremely low birth weight infants in the NICU

Extremely preterm infants are particularly vulnerable to systemic infections secondary to their immature immune defenses, prolonged hospitalizations, delays in enteral feeding, early antibiotic exposure, and need for life-sustaining invasive interventions. There have been several evidence-based practices for infection prevention in this population, such as human milk feedings, utilization of "bundle checklists" and decolonization of pathogenic organisms. Other practices, such as the use of probiotics, human milk-derived fortifiers, and antifungal prophylaxis are more controversial and require further investigation regarding the risks and benefits of such interventions. This chapter examines the susceptibility of the preterm newborn infant to invasive infections and describes several strategies for infection prevention, along with the associated limitations of such practices. It also addresses the various gaps in our understanding of preventing infections in this population, and the need for additional large multi-center randomized controlled trials. Additionally, the role of the SARs-CoV-2 global pandemic and associated strategies for infection prevention in the NICU are discussed.

Can we back off using antibiotics in the NICU?

Antibiotics are extensively and inconsistently prescribed in neonatal ICUs, and usage does not correlate with rates of culture positive sepsis. There is mounting data describing the short and long-term adverse effects associated with antibiotic overuse in neonates, including the increased burden of multi-drug resistant organisms. Currently there is considerable variation in antibiotic prescribing practice among neonatologists. Applying the practice of antibiotic stewardship in the NICU is crucial for standardizing antibiotic use and improving outcomes in this population. Several approaches have been proposed to identify neonatal sepsis, with the hope of reducing antibiotic utilization. These strategies all have their limitations, and often include laboratory testing and treatment of well-appearing, non-septic, infants. A conservative "watch and wait" algorithm is suggested as an alternative method for when to initiate antibiotics. This observational approach relies on availability of trained personnel able to examine infants at specified intervals, without delaying antibiotics, should signs of sepsis arise.

Elevated C-reactive protein and complement C3 levels are associated with preterm birth: a nested case-control study in Chinese women

BACKGROUND

Currently, there are many studies researched the associations between maternal serum inflammatory indicators (i.e. ferritin, C-reactive protein [CRP], C3 and C4) and preterm birth (PTB). The results, however, are inconsistent. Therefore, the aim of this study was to estimate the relationship between maternal serum inflammatory indicators and PTB in a nested case-control (NCC)study.

METHODS

A NCC study was conducted by Guangxi Birth Cohort Study which enrolled a total of 6203 pregnant women between 5^0/7 and 34^6/7 weeks of gestational age (wGA) from six cities in China between 2015 and 2016. There were 206women who delivered preterm (< 37^0/7 wGA), and 412 women who delivered term birth, those women were matched by maternal age, birth place, gender of infants, and wGA at blood collection. The inflammatory indicators were quantified by immunoturbidimetric methods.

RESULTS

Highest quartile concentrations of all inflammatory indicators were determined versus median. After adjusting for maternal age, high levels of CRP (CRP > 16.60 mg/L) are related to the risk of PTB (OR = 2.16, 95% CI: 1.02-4.56, p = 0.044) in the first trimester. The association of C3 was extremely related to those who delivered PTB (OR = 2.53, 95% CI: 1.14-5.64, p = 0.023) in the first trimester. Moreover, no significant associations were found in C4 (p = 0.079) and ferritin (p = 0.067) between PTB.

CONCLUSIONS

Elevated concentrations of CRP and C3 in the first trimester were associated with increased risk of PTB. Inflammatory indicators may act a pivotal part in early diagnosis and prognosis of PTB.

Phototherapy is associated with the decrease in serum globulin levels in neonatal hyperbilirubinemia

Previous studies have indicated that phototherapy may be associated with childhood immune disorders in later life. The present study aimed to assess the effects of phototherapy as a risk factor in the decrease in serum globulin (GLB) levels during neonatal hyperbilirubinemia. A total of 430 full-term infants aged between 1 and 28 days, diagnosed with neonatal hyperbilirubinemia, were enrolled in the present study. Neonates with intrauterine infection, genetic abnormalities and congenital diseases were excluded from the cohort. All neonates received single-side phototherapy (halogen lamps for 12 h per day, for 3 days) and/or intravenous albumin (IVALB; 1 g/kg/day, for 2 days) and/or intravenous immunoglobulin (1 g/kg/day, for 2 days). Total serum bilirubin (TSB), albumin (ALB) and GLB levels were examined twice, on the first and fourth days of hospitalization. Neonatal TSB concentrations decreased from 299.6±83.9 to 163.6±57.6 µmol/l following 3 days of intensive treatment (P<0.001). Pearson correlative analysis indicated that TSB was significantly correlated to the GLB level (r=0.249; P<0.01), but not with ALB level. There was a significant decrease in GLB levels following phototherapy+IVALB (P<0.001). The GLB levels decreased to 2-4 g/l (10-20% compared with their baseline levels) and were markedly decreased in infants >16 days old compared with those in patients aged <16 days (P<0.001). The decreases in GLB levels observed were 21.3±4.1 to 18.5±4.2 g/l in the phototherapy group, and 23.0±3.9 to 16.6±4.5 g/l in the phototherapy+IVALB (P<0.001). The decrease in GLB levels was associated with age (95% confidence interval; -0.152, -0.016). The results demonstrated that phototherapy decreased serum GLB levels, particularly in infants aged >16 days, while additional IVALB treatment promoted the decrease, along with increased age.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Pneumonia

Neonatal pneumonia may occur in isolation or as one component of a larger infectious process. Bacteria, viruses, fungi, and parasites are all potential causes of neonatal pneumonia, and may be transmitted vertically from the mother or acquired from the postnatal environment. The patient's age at the time of disease onset may help narrow the differential diagnosis, as different pathogens are associated with congenital, early-onset, and late-onset pneumonia. Supportive care and rationally selected antimicrobial therapy are the mainstays of treatment for neonatal pneumonia. The challenges involved in microbiological testing of the lower airways may prevent definitive identification of a causative organism. In this case, secondary data must guide selection of empiric therapy, and the response to treatment must be closely monitored.

Interaction of Streptococcus agalactiae and Cellular Innate Immunity in Colonization and Disease

Streptococcus agalactiae (Group B streptococcus, GBS) is highly adapted to humans, where it is a normal constituent of the intestinal and vaginal flora. Yet, GBS has highly invasive potential and causes excessive inflammation, sepsis, and death at the beginning of life, in the elderly and in diabetic patients. Thus, GBS is a model pathobiont that thrives in the healthy host, but has not lost its potential virulence during coevolution with mankind. It remains incompletely understood how the innate immune system contains GBS in the natural niches, the intestinal and genital tracts, and which molecular events underlie breakdown of mucocutaneous resistance. Newborn infants between days 7 and 90 of life are at risk of a particularly striking sepsis manifestation (late-onset disease), where the transition from colonization to invasion and dissemination, and thus from health to severe sepsis is typically fulminant and not predictable. The great majority of late-onset sepsis cases are caused by one clone, GBS ST17, which expresses HvgA as a signature virulence factor and adhesin. In mice, HvgA promotes the crossing of both the mucosal and the blood–brain barrier. Expression levels of HvgA and other GBS virulence factors, such as pili and toxins, are regulated by the upstream two-component control system CovR/S. This in turn is modulated by acidic epithelial pH, high glucose levels, and during the passage through the mouse intestine. After invasion, GBS has the ability to subvert innate immunity by mechanisms like glycerinaldehyde-3-phosphate-dehydrogenase-dependent induction of IL-10 and β-protein binding to the inhibitory phagocyte receptors sialic acid binding immunoglobulin-like lectin 5 and 14. On the host side, sensing of GBS nucleic acids and lipopeptides by both Toll-like receptors and the inflammasome appears to be critical for host resistance against GBS. Yet, comprehensive models on the interplay between GBS and human immune cells at the colonizing site are just emerging.

Impaired neonatal macrophage phagocytosis is not explained by overproduction of prostaglandin E2

BACKGROUND

Neonates and young infants manifest increased susceptibility to bacterial, viral and fungal lung infections. Previous work has identified a role for eicosanoids in mediating host defense functions of macrophages. This study examines the relationship between alveolar macrophage (AM) host defense and production of lipid mediators during the neonatal period compared to adult AMs.

METHODS

AMs were harvested from young (day 7 and day 14) and adult (~10 week) rats. The functionality of these cells was assessed by examining their ability to phagocytose opsonized targets, produce cytokines, eicosanoids and intracellular cAMP measured by enzyme immunoassays, and gene expression of proteins, enzymes and receptors essential for eicosanoid generation and phagocytosis measured by real time RT-PCR.

RESULTS

AMs from young animals (day 7 and 14) were defective in their ability to phagocytose opsonized targets and produce tumor necrosis factor (TNF)- α. In addition, young AMs produce more prostaglandin (PG) E(2), a suppressor of host defense, and less leukotriene (LT) B(4), a promoter of host defense. Young AMs express higher levels of enzymes responsible for the production of PGE(2) and LTB(4); however, there was no change in the expression of E prostanoid (EP) receptors or LT receptors. Despite the similar EP profiles, young AMs are more responsive to PGE(2) as evidenced by their increased production of the important second messenger, cyclic AMP. In addition, young AMs express higher levels of PDE3B and lower levels of PDE4C compared to adult AMs. However, even though the young AMs produced a skewed eicosanoid profile, neither the inhibition of PGE(2) by aspirin nor the addition of exogenous LTB(4) rescued the defective opsonized phagocytosis. Examination of a receptor responsible for mediating opsonized phagocytosis showed a significant decrease in the gene expression levels of the Fcgamma receptor in young (day 7) AMs compared to adult AMs.

CONCLUSION

These results suggest that elevated production of PGE(2) and decreased production of LTB(4) do not contribute to impaired opsonized macrophage phagocytosis and highlight an important difference between young and adult AMs.

Phagocytic ability of neutrophils and monocytes in neonates

Background

Infections by a variety of pathogens are a significant cause of morbidity and mortality during perinatal period. The susceptibility of neonates to bacterial infections has been attributed to immaturity of innate immunity. It is considered that one of the impaired mechanisms is the phagocytic function of neutrophils and monocytes. The purpose of the present study was to investigate the phagocytic ability of neonates at birth.

Methods

The phagocytic ability of neutrophils and monocytes of 42 neonates was determined using the Phagotest flow cytometry method, that assesses the intake of E. Coli by phagocytes, in cord blood and in peripheral blood 3 days after birth. Fifteen healthy adults were included in the study as controls.

Results

The phagocytic ability of neutrophils in the cord blood of neonates was significantly reduced compared to adults. The 3^rd postnatal day the reduction of phagocytic ability of neutrophils was no longer significant compared to adults. The phagocytic ability of monocytes did not show any difference from that of adults either at birth or the 3^rd postnatal day.

Conclusions

Our findings indicate that the intake of E. Coli by phagocytes is impaired at birth in both preterm and full term neonates compared to adults. This defect is transient, with the phagocytic ability in neonates reaching that of the adults 3 days after birth.

Pathophysiology and treatment of septic shock in neonates

Neonatal septic shock is a devastating condition associated with high morbidity and mortality. Definitions for the sepsis continuum and treatment algorithms specific for premature neonates are needed to improve studies of septic shock and assess benefit from clinical interventions. Unique features of the immature immune system and pathophysiologic responses to sepsis, particularly those of extremely preterm infants, necessitate that clinical trials consider them as a separate group. Keen clinical suspicion and knowledge of risk factors will help to identify those neonates at greatest risk for development of septic shock. Genomic and proteomic approaches, particularly those that use very small sample volumes, will increase our understanding of the pathophysiology and direct the development of novel agents for prevention and treatment of severe sepsis and shock in the neonate. Although at present antimicrobial therapy and supportive care remain the foundation of treatment, in the future immunomodulatory agents are likely to improve outcomes for this vulnerable population.

Role of innate host defenses in susceptibility to early-onset neonatal sepsis

Neonatal sepsis continues to take a devastating toll globally. Although adequate to protect against invasive infection in most newborns, the distinct function of neonatal innate host defense coupled with impairments in adaptive immune responses increases the likelihood of acquiring infection early in life, with subsequent rapid dissemination and death. Unique differences exist between neonates and older populations with respect to the capacity, quantity, and quality of innate host responses to pathogens. Recent characterization of the age-dependent maturation of neonatal innate immune function has identified novel translational approaches that may lead to improved diagnostic, prophylactic, and therapeutic modalities.

Induction and termination of inflammatory signaling in group B streptococcal sepsis

SUMMARY

Group B streptococcus (GBS) is part of the normal genital and gastrointestinal flora in healthy humans. However, GBS is a major cause of sepsis and meningitis in newborn infants in the Western world and an important pathogen in many developing countries. The dissection of the host response to GBS may increase the general understanding of innate immunity in sepsis, because newborn infants lack a sufficient adaptive response. Inflammatory signal induction in macrophages by GBS seems largely preserved in newborn infants, as shown both in vitro and in vivo. The engagement of Toll-like receptor 2 (TLR2) by lipoproteins and a myeloid differentiation factor 88 (MyD88)--dependent pathway induced by GBS cell wall are both important in this context. TLR2 activation of microglia by GBS induces neuronal damage, which might account for the high morbidity of GBS meningitis. At the same time, TLR2 mediates activation-induced cell death (AICD), a process involved in the containment of inflammation. In newborn infants, AICD and anti-bacterial polymorphonuclear leukocyte activity appears to be compromised. Accordingly, neonatal aberrations in the pathogen-specific negative control of inflammatory signaling are likely to contribute to excessive inflammation and neurological sequelae in GBS sepsis and meningitis.

The innate immune system and its relevance to neonatal sepsis

PURPOSE OF REVIEW

The advent of human Toll-like receptors has revolutionized our understanding of innate immunity. This review summarizes recent discoveries about the role of Toll-like receptors and innate immunity in neonatal sepsis with a particular emphasis on the paradigmatic organism S. agalactiae.

RECENT FINDINGS

S. agalactiae stimulates phagocytes to excessive formation of inflammatory cytokines such as tumor necrosis factor, and Toll-like receptors are essential for this response both in vivo and in vitro. On the molecular level, distinct signaling pathways are engaged by released S. agalactiae toxins such as lipoteichoic acid (Toll-like receptor-2 dependent) and cell-bound toxins (Toll-like receptor-2 independent). In contrast, complement receptors and Fc receptors, but not Toll-like receptors, are directly involved in phagocytosis and therefore elimination of S. agalactiae. Notably, neonatal phagocytes potently activate cytokines in response to S. agalactiae but are deficient in S. agalactiae uptake and killing. Interference with the Toll-like receptor-dependent mitogen activated protein kinase cJun N-terminal Kinase improves outcome in a neonatal model of S. agalactiae sepsis by inhibiting cytokine formation but preserving clearance of S. agalactiae.

SUMMARY

Recent progress in the understanding of S. agalactiae recognition and phagocytic signaling in neonatal sepsis suggests intermediates in the Toll-like receptor pathways as valuable targets for adjunctive sepsis therapy.

Reference distributions for complement proteins C3 and C4: a comparison of a large cohort to the world's literature

The lack of credible reference materials and satisfactory methods for quantifying serum levels has limited the bedside use of complement protein (C3 and C4) measurements. However, great technological strides have been made in the last few years. The remaining barrier to a more relevant and cost-effective use of serum protein data for diagnosis and prognosis is the availability of reliable reference intervals from birth to old age for both males and females. Fifty-one publications reporting reference intervals were identified that meet the criteria used in our prior four studies, and these were analyzed statistically. Previous small studies with constrained age ranges agree, on average, with our larger series of life-long reference ranges. This meta-analysis provides support for our reference ranges and places them in the context of previous publications.

Effect of gestational age on plasma fibronectin concentrations in the neonate

BACKGROUND

Fibronectin (FN) is known to have important roles in host defense against infection. The risk for neonatal sepsis increases with the degree of immaturity of the host. Conflicting results have been reported on the relationship between plasma FN levels and gestational age (GA) in the preterm neonate.

METHODS

In the present study, we determined plasma FN concentrations with an immunodiffusion method in 40 newborns of various gestational ages, ranging from 30 to 42 weeks.

RESULTS

We found a strong direct correlation between plasma FN levels and GA (r = 0.86; P < 0.001).

CONCLUSIONS

We speculate that the increased risk for neonatal sepsis with degree of prematurity may, in part, be explained by impaired defense with decreasing plasma FN levels seen with lessening GA.

Is there an effect of immunoglobulins and G-CSF on neutrophil phagocytic activity in preterm infants?

The percentage of neutrophils phagocytosing group B streptococci (GBS) in vitro was determined in ten healthy preterm infants (< 32 weeks of gestation) and adult controls by using an acridine orange fluorescence whole blood assay. When GBS were opsonized with adult serum, no difference in phagocytic activity was found between both groups after 10 and 30 min (preterms: 40% and 68%, adults: 32% and 56%, respectively). Phagocytosis rates in preterm infants decreased significantly to 6% and 18% (at 10 and 30 min) when pool serum of preterm infants was used instead. Supplementation of the preterm serum with either intravenous immunoglobulin or IgM-enriched immunoglobulin did not change the results significantly. The addition of granulocyte colony-stimulating factor (G-CSF) accelerated phagocytosis significantly after 10 min, but did not increase the overall phagocytic activity after 30 min in either group. Hence the potential benefits of intravenous immunoglobulins and G-CSF in neonatal sepsis may not be attributable to an immediate increase in and direct effect on neutrophil phagocytic activity.