Increased Expression of Anaphylatoxin C5a-Receptor-1 in Neutrophils and Natural Killer Cells of Preterm Infants.

Preterm infants are susceptible to infection and their defense against pathogens relies largely on innate immunity. The role of the complement system for the immunological vulnerability of preterm infants is less understood. Anaphylatoxin C5a and its receptors C5aR1 and -2 are known to be involved in sepsis pathogenesis, with C5aR1 mainly exerting pro-inflammatory effects. Our explorative study aimed to determine age-dependent changes in the expression of C5aR1 and C5aR2 in neonatal immune cell subsets. Via flow cytometry, we analyzed the expression pattern of C5a receptors on immune cells isolated from peripheral blood of preterm infants (n = 32) compared to those of their mothers (n = 25). Term infants and healthy adults served as controls. Preterm infants had a higher intracellular expression of C5aR1 on neutrophils than control individuals. We also found a higher expression of C5aR1 on NK cells, particularly on the cytotoxic CD56dim subset and the CD56- subset. Immune phenotyping of other leukocyte subpopulations revealed no gestational-age-related differences for the expression of and C5aR2. Elevated expression of C5aR1 on neutrophils and NK cells in preterm infants may contribute to the phenomenon of "immunoparalysis" caused by complement activation or to sustained hyper-inflammatory states. Further functional analyses are needed to elucidate the underlying mechanisms.

Hyperoxia/Hypoxia Exposure Primes a Sustained Pro-Inflammatory Profile of Preterm Infant Macrophages Upon LPS Stimulation.

Preterm infants are highly susceptible to sustained lung inflammation, which may be triggered by exposure to multiple environmental cues such as supplemental oxygen (O2) and infections. We hypothesized that dysregulated macrophage (MФ) activation is a key feature leading to inflammation-mediated development of bronchopulmonary dysplasia (BPD) in preterm infants. Therefore, we aimed to determine age-dependent differences in immune responses of monocyte-derived MФ comparing cord blood samples derived from preterm (n=14) and term (n=19) infants as well as peripheral blood samples from healthy adults (n=17) after lipopolysaccharide (LPS) exposure. Compared to term and adult MФ, LPS-stimulated preterm MФ showed an enhanced and sustained pro-inflammatory immune response determined by transcriptome analysis, cytokine release inducing a RORC upregulation due to T cell polarization of neonatal T cells, and TLR4 surface expression. In addition, a double-hit model was developed to study pulmonary relevant exposure factors by priming MФ with hyperoxia (O2 = 65%) or hypoxia (O2 = 3%) followed by lipopolysaccharide (LPS, 100ng/ml). When primed by 65% O2, subsequent LPS stimulation in preterm MФ led to an exaggerated pro-inflammatory response (e.g. increased HLA-DR expression and cytokine release) compared to LPS stimulation alone. Both, exposure to 65% or 3% O2 together with subsequent LPS stimulation, resulted in an exaggerated pro-inflammatory response of preterm MФ determined by transcriptome analysis. Downregulation of two major transcriptional factors, early growth response gene (Egr)-2 and growth factor independence 1 (Gfi1), were identified to play a role in the exaggerated pro-inflammatory response of preterm MФ to LPS insult after priming with 65% or 3% O2. Preterm MФ responses to LPS and hyperoxia/hypoxia suggest their involvement in excessive inflammation due to age-dependent differences, potentially mediated by downregulation of Egr2 and Gfi1 in the developing lung.

Increased Regulatory T Cells Precede the Development of Bronchopulmonary Dysplasia in Preterm Infants.

Regulatory T cells (Tregs) are important for the ontogenetic control of immune activation and tissue damage in preterm infants. However, the role of Tregs for the development of bronchopulmonary dysplasia (BPD) is yet unclear. The aim of our study was to characterize CD4+ CD25+ forkhead box protein 3 (FoxP3)+ Tregs in peripheral blood of well-phenotyped preterm infants (n = 382; 23 + 0 - 36 + 6 weeks of gestational age) with a focus on the first 28 days of life and the clinical endpoint BPD (supplemental oxygen for longer than 28 days of age). In a subgroup of preterm infants, we characterized the immunological phenotype of Tregs (n = 23). The suppressive function of Tregs on CD4+CD25- T cells was compared in preterm, term and adult blood. We observed that extreme prematurity was associated with increased Treg frequencies which peaked in the second week of life. Independent of gestational age, increased Treg frequencies were noted to precede the development of BPD. The phenotype of preterm infant Tregs largely differed from adult Tregs and displayed an overall naïve Treg population (CD45RA+/HLA-DR-/Helios+), especially in the first days of life. On day 7 of life, a more activated Treg phenotype pattern (CCR6+, HLA-DR+, and Ki-67+) was observed. Tregs of preterm neonates had a higher immunosuppressive capacity against CD4+CD25- T cells compared to the Treg compartment of term neonates and adults. In conclusion, our data suggest increased frequencies and functions of Tregs in preterm neonates which display a distinct phenotype with dynamic changes in the first weeks of life. Hence, the continued abundance of Tregs may contribute to sustained inflammation preceding the development of BPD. Functional analyses are needed in order to elucidate whether Tregs have potential as future target for diagnostics and therapeutics.

Mannose-binding lectin and mannose-binding protein-associated serine protease 2 levels and infection in very-low-birth-weight infants.

OBJECTIVE: The aim of this study was to explore the role of the lectin pathway in neonatal sepsis through the study of MBL and MASP2 levels and their relationship with infection in a cohort of very-low-birth-weight infants (VLBWI). METHODS: MBL and MASP2 were measured in plasma samples of n = 89 VLBWI using ELISA and correlated with clinical parameters. MBL plasma levels were aligned with genotyping data of mbl2 exon 1 polymorphisms, rs1800450, rs1800451, and rs5030737. RESULTS: MBL levels were clearly determined by MBL genotype, i.e., AA individuals had tenfold higher MBL levels than AO individuals. MBL and MASP2 levels did not correlate with gestational age, apart from MASP2 levels on day 7. During the first 21 days of life, we noted a gradual increase in both MBL and MASP2 levels. On day 7 of life, MASP2 levels in infants developing late-onset sepsis measured before the onset of symptoms were found to be lower, as compared to non-LOS infants. CONCLUSIONS: In our cohort of VLBWI, MBL levels were genetically determined, but not associated with gestational age or sepsis in the first 21 days of life. Lower MASP2 levels on day 7 may indicate increased risk for late-onset infection.

Antifungal Treatment and Outcome in Very Low Birth Weight Infants: A Population-based Observational Study of the German Neonatal Network.

BACKGROUND: The diagnostic proof of fungal infection in preterm infants is difficult. Antifungal treatment (AFT) is often initiated empirically when infants with suspected infection do not improve despite broad-spectrum antibiotic therapy. It was the aim of our study to determine the rate of exposure to empirical AFT in a large cohort of very low birth weight infants (VLBWI) of the German Neonatal Network and to address associated risks and outcomes. METHODS: The epidemiologic database consisted of n = 13,343 VLBWI born in 54 German Neonatal Network centers between 2009 and 2015. AFT was defined as number of neonates who got any dose of at least one of the following antifungal drugs: fluconazole, amphotericin B, voriconazole and caspofungin (denominator: number of infants enrolled in German Neonatal Network) for treatment (not prophylaxis) of (suspected) fungal infection. Univariate and logistic regression analyses were used to identify risk factors for exposure to AFT and associated short-term morbidities and long-term outcomes at 5-year follow-up. RESULTS: In our cohort, 724 out of 13,343 (5.4%) VLBWI were exposed to empiric AFT and had a mean gestational age of 25.7 (±2.1) weeks. Forty-four out of 13,343 (0.3%) had proven bloodstream infection with Candida spp. The main risk factors for exposure to AFT were gestational age, postnatal steroid treatment, need for abdominal surgery and use of carbapenems. Notably, AFT was associated with adverse outcomes such as bronchopulmonary dysplasia [adjusted odds ratio (OR): 1.9; 95% confidence interval (CI): 1.6-2.3; P < 0.001) and retinopathy of prematurity requiring intervention (adjusted OR: 1.69; 95% CI: 1.3-2.3; P <0.001) but not mortality. In the subgroup of infants available for 5-year follow-up (n = 895), exposure to AFT was associated with a risk for cerebral palsy (adjusted OR: 2.79; 95% CI: 1.11-7.04; P = 0.04) and intelligence quotient < 85 (adjusted OR: 2.07; 95% CI: 1.01-4.28; P = 0.049). CONCLUSIONS: A significant proportion of VLBWI is exposed to AFT, specifically those born <26 weeks. Exposed infants were found to have a higher risk for adverse outcomes, which may reflect their significant vulnerability in general. Given the observational design of our study, it remains unclear whether potential side effects of empirical or target AFT itself contribute to adverse outcome. Future studies need to include risk-based strategies and stewardship programs to restrict the use of antifungal management in VLBWI.

IgG Fc Glycosylation Patterns of Preterm Infants Differ With Gestational Age.

Preterm infants acquire reduced amounts of Immunoglobulin G (IgG) via trans-placental transfer as compared to term infants which might explain their high susceptibility for infections. The reduced amount of IgG antibodies also results in a lower amount of anti-inflammatory Fc N-galactosylated and -sialylated IgG antibodies. This reduction or, even more, a qualitative shift in the type of IgG Fc glycosylation might contribute to the increased risk for sustained inflammatory diseases in preterm infants. It was the aim of our explorative study to investigate the IgG Fc glycosylation patterns in preterm infants of different gestational ages compared to term infants and mothers of preterm infants. In plasma samples of preterm infants (n = 38), we investigated IgG concentrations by use of ELISA. Furthermore, we analyzed IgG Fc glycosylation patterns in plasma of preterm infants (n = 86, 23-34 weeks of gestation), term infants (n = 15) and mothers from preterm infants (n = 41) using high performance liquid chromatography. Extremely low gestational age infants (born < 28 weeks of gestation during second trimester) had reduced IgG concentrations and decreased proportions of galactosylated (84.5 vs. 88.4%), sialylated (14.5 vs. 17.9%) and bisecting N-acetylglucosamine-containing (8.4 vs. 10.8%) IgG Fc N-linked glycans as compared to preterm infants born ≥28 weeks of gestation (during third trimester) and term infants. Increased non-galactosylated (agalactosylated, 16.9 vs. 10.6%) IgG Fc N-linked glycans were associated with the development of chronic inflammatory bronchopulmonary dysplasia (BPD). However, mothers of preterm infants born during second or third trimester of pregnancy did not show significant differences in IgG Fc glycosylation patterns. Thus, the IgG Fc glycosylation patterns of preterm infants depend on their gestational age. Although lack of bisecting N-acetylglucosamine has been associated with less inflammatory effector functions, the decreased IgG Fc galactosylation and sialylation with lower gestational age suggest a rather pro-inflammatory pattern. The difference in IgG Fc glycosylation patterns between preterm infants and mothers of preterm infants suggests a selective enrichment of IgG glyco forms in preterm infants, which might contribute to or result of the development of sustained inflammatory diseases like BPD.

The association of mannose-binding lectin 2 polymorphisms with outcome in very low birth weight infants.

OBJECTIVES: Studies on the influence of mannose-binding lectin (MBL) deficiency on infection susceptibility in preterm infants have yielded controversial results. We investigated the association of genotype-based MBL levels with outcome in very-low-birth weight infants (VLBWI). METHODS: We genotyped 3 genetic variants of MBL2 (rs1800450, rs1800451, rs5030737) in 6878 VLBWI. MBL plasma levels were categorized as normal (wild type, A/A), low (heterozygotes, A/O) or undetectable (homozygotes, O/O). Primary outcome was the effect of genotype-based MBL2 levels on blood-culture proven and clinical sepsis during primary stay in hospital. We also evaluated burden of infection within 24 months after discharge. RESULTS: We found no association between MBL levels and sepsis risk in the whole cohort. Infants without measurable MBL levels born between 32 0/7 to 36 6/7 weeks of gestation, however, had a higher rate of Gram-negative sepsis than infants with normal or reduced MBL levels. In a follow-up investigation at 24 months (n = 1070 infants), infants without measurable MBL levels suffered more frequently from stomatitis and urinary tract infection. CONCLUSIONS: In a large cohort of VLBWI MBL2 deficiency had no major impact on infection risk unless children were born between 32 0/7 and 36 6/7 weeks of gestation.

Delivery mode and intraventricular hemorrhage risk in very-low-birth-weight infants: Observational data of the German Neonatal Network.

BACKGROUND: Very-low-birth-weight infants (VLBWI) are frequently delivered by cesarean section (CS). However, it is unclear at what gestational age the benefits of spontaneous delivery outweigh the perinatal risks, i.e. intraventricular hemorrhage (IVH) or death. OBJECTIVES: To assess the short-term outcome of VLBWI on IVH according to mode of delivery in a population-based cohort of the German Neonatal Network (GNN). STUDY DESIGN: A total cohort of 2203 singleton VLBWI with a birth weight <1500g and gestational age between 22 0/7 and 36 6/7 weeks born and discharged between 1st of January 2009 and 31st of December 2015 was available for analysis. VLBWI were stratified into three categories according to mode of delivery: (1) planned cesarean section (n=1381), (2) vaginal delivery (n=632) and (3) emergency cesarean section (n=190). Outcome was assessed in univariate and logistic regression analyses. RESULTS: Prevalence of IVH was significantly higher in the vaginal delivery (VD) (26.6%) and emergency CS group (31.1%) as compared to planned CS (17.2%), respectively. In a logistic regression analysis including known risk factors for IVH, vaginal delivery (OR 1.725 [1.325-2.202], p≤0.001) and emergency cesarean section (OR 1.916 [1.338-2.746], p≤0.001) were independently associated with IVH risk. In the subgroup of infants >30 weeks of gestation prevalence for IVH was not significantly different in VD and planned CS (5.3% vs. 4.4%). CONCLUSIONS: Our observational data demonstrate that elective cesarean section is associated with a reduced risk of IVH in preterm infants <30 weeks gestational age when presenting with preterm labor.

Media Stories on NICU Outbreaks Lead to an Increased Prescription Rate of Third-Line Antibiotics in the Community of Neonatal Care.

BACKGROUND Between 2010 and 2012, 3 outbreaks of nosocomial infections in German neonatal intensive care units (NICUs) attracted considerable public interest. Headlines on national television channels and in newspapers had important consequences for the involved institutions and a negative impact on the relationship between families and staff in many German NICUs. OBJECTIVE To determine whether NICU outbreaks reported in the media influenced provider behavior in the community of neonatal care and led to more third-line antibiotic prescribing. DESIGN Observational cohort study. METHODS To investigate secular trends, we evaluated data for very-low-birth-weight infants (VLBWIs, birth weight <1,500 g) enrolled in the German Neonatal Network (GNN) between 2009 and 2014 (N=10,253). For outbreak effects, we specifically analyzed data for VLBWIs discharged 6 months before (n=2,428) and 6 months after outbreaks (n=2,508). RESULTS The exposure of all VLBWIs to third-line antibiotics increased after outbreaks (19.4% before vs 22.5% after; P=.007). This trend particularly affected male infants (4.6% increase; P=.005) and infants with a birth weight between 1,000 and 1,499 g (3.5% increase; P=.001) In a logistic regression analysis, month of discharge as linear variable of time was associated with increased exposure to third-line antibiotics (odds ratio [OR], 1.01; 95% confidence interval [CI], 1.009-1.014; P<.001), and discharge within the 6-month period after outbreak reports independently contributed to this long-term trend (OR, 1.14; 95% CI, 1.017-1.270; P=.024). CONCLUSIONS Media reports directly affect medical practice, eg, overuse of third-line antibiotics. Future communication and management strategies must be based on objective dialogues between the scientific community and investigative journalists. Infect Control Hosp Epidemiol 2016;37:924-930.

NOD2 Loss-of-Function Mutations and Risks of Necrotizing Enterocolitis or Focal Intestinal Perforation in Very Low-birth-weight Infants.

BACKGROUND: NOD2 loss-of-function mutations, that is, R702W [rs2066844], G908R [rs2066845], and Leu1007fsinsC [rs5743293], have been linked to inflammatory bowel diseases. It is yet unknown whether these variants are also associated with necrotizing enterocolitis (NEC) or focal intestinal perforation (FIP) in infants of very low birth weight (VLBW). METHODS: To test this hypothesis, we genotyped 9082 VLBW infants with European ancestry enrolled in a prospective, population-based cohort study of the German Neonatal Network. We assessed the effect of the NOD2 gene variants on the risk for major morbidities of the gastrointestinal tract, that is, NEC/FIP requiring surgery in multivariable logistic regression analyses. RESULTS: In the whole cohort of VLBW infants, carriers of ≥ 2 NOD2 variant alleles had an increased risk for NEC requiring surgery (odds ratio [OR], 3.57; 95% confidence interval [CI], 1.27-10.04; P = 0.03) and NEC or FIP requiring surgery (OR, 3.81; 95% CI, 1.70-8.51; P = 0.004) as compared with wild-type genotypes. In a multivariable logistic regression analysis including gestational age, birth weight, gender, multiple birth, and inborn delivery, the association between ≥ 2 NOD2 variant alleles and NEC surgery (OR, 4.14; 95% CI, 1.41-12.12; P = 0.009), FIP surgery (OR, 3.50; 95% CI, 1.02-12.04; P = 0.047), and NEC or FIP surgery (OR, 4.10; 95% CI, 1.74-9.73; P = 0.001) proved to be independent. We also performed a regression analysis in the subgroup of infants with available information on Lactobacillus acidophilus/Bifidobacterium infantis probiotic supplementation (n = 3638). Although probiotics had a protective effect on NEC and NEC or FIP requiring surgery, the NOD2 variants had no significant impact in this subgroup. CONCLUSIONS: VLBW infants carrying ≥ 2 NOD2 genetic risk factors of inflammatory bowel disease in adults have an increased risk for severe gastrointestinal complications, such as NEC requiring surgery. Therefore, infants might benefit from NOD2 genotyping followed by supplementation with probiotics. Replication studies are needed along with genome-wide arrays to allow risk-adapted prevention and therapeutic strategies.

Preterm prelabor rupture of membranes and outcome of very-low-birth-weight infants in the German Neonatal Network.

OBJECTIVE: It was the aim of our study to evaluate the independent effect of preterm prelabor rupture of membranes (PPROM) as a cause of preterm delivery on mortality during primary hospital stay and significant morbidities in very-low-birth-weight (VLBW) infants < 32 weeks of gestation. DESIGN: Observational, epidemiological study design. SETTING: Population-based cohort, German Neonatal Network (GNN). POPULATION: 6102 VLBW infants were enrolled in GNN from 2009-2012, n=4120 fulfilled criteria for primary analysis (< 32 gestational weeks, no pre-eclampsia, HELLP (highly elevated liver enzymes and low platelets syndrome) or placental abruption as cause of preterm birth). METHODS: Multivariable logistic regression analyses included PPROM as potential risk factors for adverse outcomes and well established items such as gestational age in weeks, birth weight, antenatal steroids, center, inborn delivery, multiple birth, gender and being small-for-gestational-age. RESULTS: PPROM as cause of preterm delivery had no independent effect on the risk of early-onset sepsis, clinical sepsis and blood-culture proven sepsis, while gestational age proved to be the most important contributor to sepsis risk. The diagnosis of PPROM was associated with an increased risk for bronchopulmonary dysplasia (BPD; OR: 1.25, 95% CI: 1.02-1.55, p=0.03) but not with other major outcomes. CONCLUSIONS: The diagnosis of PPROM per se is not associated with adverse outcome in VLBW infants < 32 weeks apart from a moderately increased risk for BPD. Randomized controlled trials with primary neonatal outcomes are needed to determine which subgroup of VLBW infants benefit from expectant or intentional management of PPROM.