@article{RitzEnlowSchulzetal.2012,
  author    = {Ritz, Thomas and Enlow, Michelle Bosquet and Schulz, Stefan M. and Kitts, Robert and Staudenmayer, John and Wright, Rosalind J.},
  title     = {Respiratory Sinus Arrhythmia as an Index of Vagal Activity during Stress in Infants: Respiratory Influences and Their Control},
  series = {PLoS One},
  volume    = {7},
  journal   = {PLoS One},
  number    = {12},
  doi       = {10.1371/journal.pone.0052729},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-135396},
  pages     = {e52729},
  year      = {2012},
  abstract  = {Respiratory sinus arrhythmia (RSA) is related to cardiac vagal outflow and the respiratory pattern. Prior infant studies have not systematically examined respiration rate and tidal volume influences on infant RSA or the extent to which infants' breathing is too fast to extract a valid RSA. We therefore monitored cardiac activity, respiration, and physical activity in 23 six-month old infants during a standardized laboratory stressor protocol. On average, 12.6\% (range 0-58.2\%) of analyzed breaths were too short for RSA extraction. Higher respiration rate was associated with lower RSA amplitude in most infants, and lower tidal volume was associated with lower RSA amplitude in some infants. RSA amplitude corrected for respiration rate and tidal volume influences showed theoretically expected strong reductions during stress, whereas performance of uncorrected RSA was less consistent. We conclude that stress-induced changes of peak-valley RSA and effects of variations in breathing patterns on RSA can be determined for a representative percentage of infant breaths. As expected, breathing substantially affects infant RSA and needs to be considered in studies of infant psychophysiology.},
  language  = {en}
}
@article{HumbergFortmannSilleretal.2020,
  author    = {Humberg, Alexander and Fortmann, Ingmar and Siller, Bastian and Kopp, Matthias Volkmar and Herting, Egbert and G{\"o}pel, Wolfgang and H{\"a}rtel, Christoph},
  title     = {Preterm birth and sustained inflammation: consequences for the neonate},
  series = {Seminars in Immunopathology},
  volume    = {42},
  journal   = {Seminars in Immunopathology},
  organization    = {German Neonatal Network, German Center for Lung Research and Priming Immunity at the beginning of life (PRIMAL) Consortium},
  issn      = {1863-2297},
  doi       = {10.1007/s00281-020-00803-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-235019},
  pages     = {451-468},
  year      = {2020},
  abstract  = {Almost half of all preterm births are caused or triggered by an inflammatory process at the feto-maternal interface resulting in preterm labor or rupture of membranes with or without chorioamnionitis ("first inflammatory hit"). Preterm babies have highly vulnerable body surfaces and immature organ systems. They are postnatally confronted with a drastically altered antigen exposure including hospital-specific microbes, artificial devices, drugs, nutritional antigens, and hypoxia or hyperoxia ("second inflammatory hit"). This is of particular importance to extremely preterm infants born before 28 weeks, as they have not experienced important "third-trimester" adaptation processes to tolerate maternal and self-antigens. Instead of a balanced adaptation to extrauterine life, the delicate co-regulation between immune defense mechanisms and immunosuppression (tolerance) to allow microbiome establishment is therefore often disturbed. Hence, preterm infants are predisposed to sepsis but also to several injurious conditions that can contribute to the onset or perpetuation of sustained inflammation (SI). This is a continuing challenge to clinicians involved in the care of preterm infants, as SI is regarded as a crucial mediator for mortality and the development of morbidities in preterm infants. This review will outline the (i) role of inflammation for short-term consequences of preterm birth and (ii) the effect of SI on organ development and long-term outcome.},
  language  = {en}
}
@article{GlaserGradzkaLuczewskaSzymankiewiczBreborowiczetal.2019,
  author    = {Glaser, Kirsten and Gradzka-Luczewska, Anna and Szymankiewicz-Breborowicz, Marta and Kawczynska-Leda, Natalia and Henrich, Birgit and Waaga-Gasser, Ana Maria and Speer, Christian P.},
  title     = {Perinatal ureaplasma exposure is associated with increased risk of late onset sepsis and imbalanced inflammation in preterm infants and may add to lung injury},
  series = {Frontiers in Cellular and Infection Microbiology},
  volume    = {9},
  journal   = {Frontiers in Cellular and Infection Microbiology},
  number    = {68},
  doi       = {10.3389/fcimb.2019.00068},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201270},
  year      = {2019},
  abstract  = {Background: Controversy remains concerning the impact of Ureaplasma on preterm neonatal morbidity. Methods: Prospective single-center study in very low birth weight infants <30 weeks' gestation. Cord blood and initial nasopharyngeal swabs were screened for Ureaplasma parvum and U. urealyticum using culture technique and polymerase chain reaction. Neonatal outcomes were followed until death or discharge. Multi-analyte immunoassay provided cord blood levels of inflammatory markers. Using multivariate regression analyses, perinatal Ureaplasma exposure was evaluated as risk factor for the development of bronchopulmonary dysplasia (BPD), other neonatal morbidities until discharge and systemic inflammation at admission. Results: 40/103 (39\%) infants were positive for Ureaplasma in one or both specimens, with U. parvum being the predominant species. While exposure to Ureaplasma alone was not associated with BPD, we found an increased risk of BPD in Ureaplasma-positive infants ventilated ≥5 days (OR 1.64; 95\% CI 0.12-22.98; p = 0.009). Presence of Ureaplasma was associated with a 7-fold risk of late onset sepsis (LOS) (95\% CI 1.80-27.39; p = 0.014). Moreover, Ureaplasma-positive infants had higher I/T ratios (b 0.39; 95\% CI 0.08-0.71; p = 0.014), increased levels of interleukin (IL)-17 (b 0.16; 95\% CI 0.02-0.30; p = 0.025) and matrix metalloproteinase 8 (b 0.77; 95\% CI 0.10-1.44; p = 0.020), decreased levels of IL-10 (b -0.77; 95\% CI -1.58 to -0.01; p = 0.043) and increased ratios of Tumor necrosis factor-α, IL-8, and IL-17 to anti-inflammatory IL-10 (p = 0.003, p = 0.012, p < 0.001). Conclusions: Positive Ureaplasma screening was not associated with BPD. However, exposure contributed to BPD in infants ventilated ≥5 days and conferred an increased risk of LOS and imbalanced inflammatory cytokine responses.},
  language  = {en}
}
@article{BoeckelKarstenGoepeletal.2023,
  author    = {Boeckel, Hannah and Karsten, Christian M. and G{\"o}pel, Wolfgang and Herting, Egbert and Rupp, Jan and H{\"a}rtel, Christoph and Hartz, Annika},
  title     = {Increased expression of anaphylatoxin C5a-receptor-1 in neutrophils and natural killer cells of preterm infants},
  series = {International Journal of Molecular Sciences},
  volume    = {24},
  journal   = {International Journal of Molecular Sciences},
  number    = {12},
  issn      = {1422-0067},
  doi       = {10.3390/ijms241210321},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-321196},
  year      = {2023},
  abstract  = {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 CD56\(^{dim}\) 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.},
  language  = {en}
}
@article{FortmannDirksGoedickeFritzetal.2022,
  author    = {Fortmann, Mats Ingmar and Dirks, Johannes and Goedicke-Fritz, Sybelle and Liese, Johannes and Zemlin, Michael and Morbach, Henner and H{\"a}rtel, Christoph},
  title     = {Immunization of preterm infants: current evidence and future strategies to individualized approaches},
  series = {Seminars in Immunopathology},
  volume    = {44},
  journal   = {Seminars in Immunopathology},
  number    = {6},
  doi       = {10.1007/s00281-022-00957-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324261},
  pages     = {767-784},
  year      = {2022},
  abstract  = {Preterm infants are at particularly high risk for infectious diseases. As this vulnerability extends beyond the neonatal period into childhood and adolescence, preterm infants benefit greatly from infection-preventive measures such as immunizations. However, there is an ongoing discussion about vaccine safety and efficacy due to preterm infants' distinct immunological features. A significant proportion of infants remains un- or under-immunized when discharged from primary hospital stay. Educating health care professionals and parents, promoting maternal immunization and evaluating the potential of new vaccination tools are important means to reduce the overall burden from infectious diseases in preterm infants. In this narrative review, we summarize the current knowledge about vaccinations in premature infants. We discuss the specificities of early life immunity and memory function, including the role of polyreactive B cells, restricted B cell receptor diversity and heterologous immunity mediated by a cross-reactive T cell repertoire. Recently, mechanistic studies indicated that tissue-resident memory (Trm) cell populations including T cells, B cells and macrophages are already established in the fetus. Their role in human early life immunity, however, is not yet understood. Tissue-resident memory T cells, for example, are diminished in airway tissues in neonates as compared to older children or adults. Hence, the ability to make specific recall responses after secondary infectious stimulus is hampered, a phenomenon that is transcriptionally regulated by enhanced expression of T-bet. Furthermore, the microbiome establishment is a dominant factor to shape resident immunity at mucosal surfaces, but it is often disturbed in the context of preterm birth. The proposed function of Trm T cells to remember benign interactions with the microbiome might therefore be reduced which would contribute to an increased risk for sustained inflammation. An improved understanding of Trm interactions may determine novel targets of vaccination, e.g., modulation of T-bet responses and facilitate more individualized approaches to protect preterm babies in the future.},
  language  = {en}
}
@article{GlaserKernSpeeretal.2023,
  author    = {Glaser, Kirsten and Kern, David and Speer, Christian P. and Schlegel, Nicolas and Schwab, Michael and Thome, Ulrich H. and H{\"a}rtel, Christoph and Wright, Clyde J.},
  title     = {Imbalanced inflammatory responses in preterm and term cord blood monocytes and expansion of the CD14\(^+\)CD16\(^+\) subset upon toll-like receptor stimulation},
  series = {International Journal of Molecular Sciences},
  volume    = {24},
  journal   = {International Journal of Molecular Sciences},
  number    = {5},
  issn      = {1422-0067},
  doi       = {10.3390/ijms24054919},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-311056},
  year      = {2023},
  abstract  = {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.},
  language  = {en}
}
@article{TwisselmannPagelKuenstneretal.2021,
  author    = {Twisselmann, Nele and Pagel, Julia and K{\"u}nstner, Axel and Weckmann, Markus and Hartz, Annika and Glaser, Kirsten and Hilgendorff, Anne and G{\"o}pel, Wolfgang and Busch, Hauke and Herting, Egbert and Weinberg, Jason B. and H{\"a}rtel, Christoph},
  title     = {Hyperoxia/Hypoxia Exposure Primes a Sustained Pro-Inflammatory Profile of Preterm Infant Macrophages Upon LPS Stimulation},
  series = {Frontiers in Immunology},
  volume    = {12},
  journal   = {Frontiers in Immunology},
  issn      = {1664-3224},
  doi       = {10.3389/fimmu.2021.762789},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250356},
  year      = {2021},
  abstract  = {Preterm infants are highly susceptible to sustained lung inflammation, which may be triggered by exposure to multiple environmental cues such as supplemental oxygen (O\(_2\)) 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 (O\(_2\) = 65\%) or hypoxia (O\(_2\) = 3\%) followed by lipopolysaccharide (LPS, 100ng/ml). When primed by 65\% O\(_2\), 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\% O\(_2\) 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\% O\(_2\). 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.},
  language  = {en}
}
@article{FaustFreitagBarrientosetal.2021,
  author    = {Faust, Kirstin and Freitag, Nancy and Barrientos, Gabriela and Hartel, Christoph and Blois, Sandra M.},
  title     = {Galectin-Levels Are Elevated in Infants Born Preterm Due to Amniotic Infection and Rapidly Decline in the Neonatal Period},
  series = {Frontiers in Immunology},
  volume    = {11},
  journal   = {Frontiers in Immunology},
  issn      = {1664-3224},
  doi       = {10.3389/fimmu.2020.599104},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230701},
  year      = {2021},
  abstract  = {Galectin (gal)-1, -3, and -9 are members of a family of glycan binding proteins that mediate complex interactions between decidual, inflammatory and trophoblast cells modulating several processes during gestation, control of the maternal immune system, and parturition. Their immunomodulatory role in preterm birth and postnatal expression in preterm infants is unknown. We performed a single center prospective study of 170 preterm infants with a gestational age below 35 weeks. Peripheral venous blood samples were collected during the neonatal period and galectin-1, -3, and -9 were determined by ELISA. We noted a strong decline of circulating gal-1 and -3 levels but not gal-9 from birth to day 7 of life. There was an inverse correlation of gal-1 and -3 levels at birth with gestational age. Gal-1 levels were remarkably increased in infants born to amniotic infection syndrome (AIS), which was also observed for gal-9 levels. Infants who developed early-onset sepsis had higher levels of gal-3 at day 1 as compared to unaffected infants. Our observational data imply that galectin-1, -3, and -9 levels are elevated in preterm infants born in an inflammatory milieu such as AIS or EOS. Future studies need to address whether galectins mediate inflammation-induced preterm birth and could therefore be a target for clinical trials.},
  language  = {en}
}
@article{HankeRauschSosnowskietal.2022,
  author    = {Hanke, Kathrin and Rausch, Tanja K. and Sosnowski, Runa and Paul, Pia and Spiegler, Juliane and M{\"u}ller, Mirja and K{\"o}nig, Inke R. and G{\"o}pel, Wolfgang and Herting, Egbert and H{\"a}rtel, Christoph},
  title     = {Early skin-to-skin contact does not affect cerebral tissue oxygenation in preterm infants <32 weeks of gestation},
  series = {Children},
  volume    = {9},
  journal   = {Children},
  number    = {2},
  issn      = {2227-9067},
  doi       = {10.3390/children9020211},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262290},
  year      = {2022},
  abstract  = {Aim: It was the aim of our study to determine the regional cerebral tissue oxygenation saturation (rcSO\(_2\)) as an additional monitoring parameter during early skin-to-skin contact (SSC) in preterm infants with a gestational age of <32 gestational weeks. Methods: We conducted two observational convenience sample studies using additional monitoring with near-infrared spectroscopy (NIRS) in the first 120 h of life: (a) NIRS 1 (gestational age of 26 0/7 to 31 6/7 weeks) and (b) NIRS 2 (gestational age of 24 0/7 to 28 6/7 weeks). The rcSO\(_2\) values were compared between resting time in the incubator (period I), SSC (period II) and handling nursing care (period III). For the comparison, we separated the sequential effects by including a "wash-out phase" of 1 h between each period. Results: During the first 120 h of life 38/53 infants in NIRS 1 and 15/23 infants in NIRS 2 received SSC, respectively. We found no remarkable differences for rcSO\(_2\) values of NIRS 1 patients between SSC time and period I (95\% confidence interval (CI) for the difference in \%: SSC vs. period I [1; 3]). In NIRS 2, rcSO\(_2\) values during SSC were only 2\% lower compared with period I [median [1. quartile; 3. quartile] in \%; 78 [73; 82] vs. 80 [74; 85]] but were similar to period III [78 [72; 83]]. In a combined analysis, a small difference in rcSO\(_2\) values between SSC and resting times was found using a generalized linear mixed model that included gender and gestational age (OR 95\% CI; 1.178 [1.103; 1.253], p < 0.0001). Episodes below the cut-off for "hypoxia"; e.g., <55\%, were comparable during SSC and periods I and III (0.3-2.1\%). No FiO\(_2\) adjustment was required in the vast majority of SSC episodes. Conclusions: Our observational data indicate that rcSO\(_2\) values of infants during SSC were comparable to rcSO\(_2\) values during incubator care and resting time. This additional monitoring supports a safe implementation of early SSC in extremely preterm infants in NICUs.},
  language  = {en}
}