Immunological development of preterm infants in early infancy

Intrauterine desensitization enables long term survival of human oligodendrocyte progenitor cells without immunosuppression

Immune rejection can be reduced using immunosuppressants which are not viable for premature infants. However, desensitization can induce immune tolerance for premature infants because of underdeveloped immune system. The fetuses of Wistar rats at 15-17 days gestation were injected via hOPCs-1 into brain, muscles, and abdomen ex utero and then returned while the fetuses of control without injection. After 6 weeks of desensitization, the brain and muscles were transplanted with hOPCs-1, hNSCs-1, and hOPCs-2. After 10 and 34 weeks of desensitization, hOPCs-1 and hNSCs-1 in desensitized groups was higher than that in the control group while hOPCs-2 were rejected. Treg, CD4CD28, CD8CD28, and CD45RC between the desensitization and the control group differed significantly. Inflammatory cells in group with hOPCs-1 and hNSCs-1 was lower than that in the control group. hOPCs-1 can differentiate into myelin in desensitized groups. Wistar rats with desensitization developed immune tolerance to desensitized and transplanted cells.

Transfusion-related Gut Injury and Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) accounts for 10% of deaths in neonatal intensive care units. Several causal mechanisms are likely to lead to a final common disease phenotype. This article summarizes recent data on NEC following red blood cell (RBC) transfusion, with a focus on the most recent literature and ongoing trials. It highlights potential mechanisms from preclinical and human physiologic studies. It also discusses the role of feeding during RBC transfusion and the risk of NEC. Ongoing randomized trials will provide important data on how liberal or conservative approaches to RBC transfusion influence the risk of NEC.

Epidemiology of Necrotizing Enterocolitis: New Considerations Regarding the Influence of Red Blood Cell Transfusions and Anemia

This article summarizes available evidence on the relationship between red blood cell transfusion and anemia, and necrotizing enterocolitis (NEC). We review recent studies that highlight the uncertainty of the effect of red blood cell transfusion on NEC and the potential role of anemia. We also discuss potential pathophysiologic effects of both red blood cell transfusion and anemia and highlight strategies to prevent anemia and red blood cell transfusion. We also discuss ongoing randomized trials that are likely to provide important new evidence to guide red blood cell transfusion practices.

Increased serum Th2 chemokine levels are associated with bronchopulmonary dysplasia in premature infants

Bronchopulmonary dysplasia (BPD) is one of the most common chronic inflammatory lung disease of premature infants, with serious short- and long-term consequences. Early identification of premature infants at risk of BPD is critical to preventing the pathogenesis of disease. Thus, in the present study, we recruited 126 premature infants, collected peripheral blood samples at different time points during early life, and measured the concentration of Th1 (MCP-1, IP-10, and MIG) and Th2 (eotaxin-1, eotaxin-2, and MCP-4) chemokines in serum. We found serum eotaxin-2 levels were significantly higher in the BPD group than in the non-BPD group on day 1 [1662 pg/ml vs. 1221 pg/ml, P < 0.05], day 7 [1533 pg/ml vs. 1089 pg/ml, P < 0.05], and day 14 [1246 pg/ml vs. 704 pg/ml, P < 0.05] after birth, and serum MCP-4 levels were also significantly higher in the BPD group than in the non-BPD group on day 1 [186 pg/ml vs. 128 pg/ml, P < 0.05], day 7 [199 pg/ml vs. 101 pg/ml, P < 0.05], and day 14 [238 pg/ml vs. 106 pg/ml, P < 0.05] of life.Conclusions: Increased levels of Th2 chemokines, eotaxin-2, and MCP-4, are associated with BPD in premature infants. What is Known: • The pathogenesis of BPD is multifactorial and it is difficult to predict and prevent. • Previous studies have demonstrated that inflammation plays a major role in the pathogenesis of BPD. What is New: • Increased Th2 chemokines, eotaxin-2 and MCP-4, were associated with BPD in premature infants. • Abnormal Th1/Th2 response in early life maybe associated with the subsequent development of BPD, which provide a new insight to understand the pathogenesis of the disease.

Preterm Birth Affects the Risk of Developing Immune-Mediated Diseases

Prematurity affects approximately 10% of all children, resulting in drastically altered antigen exposure due to premature confrontation with microbes, nutritional antigens, and other environmental factors. During the last trimester of pregnancy, the fetal immune system adapts to tolerate maternal and self-antigens, while also preparing for postnatal immune defense by acquiring passive immunity from the mother. Since the perinatal period is regarded as the most important “window of opportunity” for imprinting metabolism and immunity, preterm birth may have long-term consequences for the development of immune-mediated diseases. Intriguingly, preterm neonates appear to develop bronchial asthma more frequently, but atopic dermatitis less frequently in comparison to term neonates. The longitudinal study of preterm neonates could offer important insights into the process of imprinting for immune-mediated diseases. On the one hand, preterm birth may interrupt influences of the intrauterine environment on the fetus that increase or decrease the risk of later immune disease (e.g., maternal antibodies and placenta-derived factors), whereas on the other hand, it may lead to the premature exposure to protective or harmful extrauterine factors such as microbiota and nutritional antigen. Solving this puzzle may help unravel new preventive and therapeutic approaches for immune diseases.

Microbiome-Gut-Brain Axis: A Pathway for Improving Brainstem Serotonin Homeostasis and Successful Autoresuscitation in SIDS-A Novel Hypothesis

Sudden infant death syndrome (SIDS) continues to be a major public health issue. Following its major decline since the "Back to Sleep" campaign, the incidence of SIDS has plateaued, with an annual incidence of about 1,500 SIDS-related deaths in the United States and thousands more throughout the world. The etiology of SIDS, the major cause of postneonatal mortality in the western world, is still poorly understood. Although sleeping in prone position is a major risk factor, SIDS continues to occur even in the supine sleeping position. The triple-risk model of Filiano and Kinney emphasizes the interaction between a susceptible infant during a critical developmental period and stressor/s in the pathogenesis of SIDS. Recent evidence ranges from dysregulated autonomic control to findings of altered neurochemistry, especially the serotonergic system that plays an important role in brainstem cardiorespiratory/thermoregulatory centers. Brainstem serotonin (5-HT) and tryptophan hydroxylase-2 (TPH-2) levels have been shown to be lower in SIDS, supporting the evidence that defects in the medullary serotonergic system play a significant role in SIDS. Pathogenic bacteria and their enterotoxins have been associated with SIDS, although no direct evidence has been established. We present a new hypothesis that the infant's gut microbiome, and/or its metabolites, by its direct effects on the gut enterochromaffin cells, stimulates the afferent gut vagal endings by releasing serotonin (paracrine effect), optimizing autoresuscitation by modulating brainstem 5-HT levels through the microbiome-gut-brain axis, thus playing a significant role in SIDS during the critical period of gut flora development and vulnerability to SIDS. The shared similarities between various risk factors for SIDS and their relationship with the infant gut microbiome support our hypothesis. Comprehensive gut-microbiome studies are required to test our hypothesis.

Differential approaches for vaccination from childhood to old age

Primary prevention strategies, such as vaccinations at the age extremes, in neonates and elderly individuals, demonstrate a challenge to health professionals and public health specialists. The aspects of the differentiation and maturation of the adaptive immune system, the functional implications of immunological immaturity or immunosenescence and its impact on vaccine immunogenicity and efficacy will be highlighted in this review. Several approaches have been undertaken to promote Th1 responses in neonates and to enhance immune functions in elderly, such as conjugation to carrier proteins, addition of adjuvants, concomitant vaccination with other vaccines, change in antigen concentrations or dose intervals or use of different administration routes. Also, early protection by maternal vaccination seems to be beneficial in neonates. However, it also appears necessary to think of other end points than antibody concentrations to assess vaccine efficacy in neonates or elderly, as also the cellular immune response may be impaired by the mechanisms of immaturity, underlying health conditions, immunosuppressive treatments or immunosenescence. Thus, lifespan vaccine programs should be implemented to all individuals on a population level not only to improve herd protection and to maintain protective antibody levels and immune memory, but also to cover all age groups, to protect unvaccinated elderly persons and to provide indirect protection for neonates and small infants.

Transfusion-related acute gut injury: feeding, flora, flow, and barrier defense

TRAGI (transfusion-related acute gut injury) is an acronym we proposed to characterize a severe neonatal gastrointestinal reaction temporally related to a transfusion of packed blood red cells (PRBCs) for anemia in very low birth weights. The following are in support of a causative relationship: (1) the timing of necrotizing enterocolitis after a PRBC transfusion not being random, (2) traditional risk factors for necrotizing enterocolitis are often absent, (3) significant anemia appears to be a universal finding, (4) the age of donor blood is often slightly older than controls, (5) TRAGI is not postnatal age dependent, and (6) TRAGI does not show a centering at 31 weeks' postconceptual age as does nontransfusion-related NEC. Although TRAGI is linked to the timing of PRBC transfusions, we propose a novel hypothesis that the convergence at 31 weeks' postconceptual age for classic NEC approximates the age of presentation of other oxygen delivery and neovascularization syndromes (eg, retinopathy of prematurity), suggesting its etiologic link to a generalized systemic maturational mechanism or another common developmental theme. This report will begin by reviewing the history of the clinical presentation and discovery of TRAGI and will then analyze various pathophysiologic mechanisms that may account for the phenomenon when clinicians render therapies. We will end by a call to action for randomized clinical trials to test various etiologic theories.

Late-preterm cesarean delivery and chemokines concentration in the umbilical cord blood of neonates

OBJECTIVE

The objective of the study was to investigate whether concentrations of chemokines in the umbilical cord blood of neonates are affected by delivery via cesarean section.

STUDY DESIGN

Umbilical cord blood was obtained from 116 singleton late-preterm and full-term neonates without infections, born to healthy pregnant women. Concentrations of chemokines - MIP-1α (CCL3), MIP-1β 1 (CCL4), RANTES (CCL5), GRO-α (CXCL1) and ENA-78 (CXCL5) - were measured by ELISA. Logistic regression was used to investigate regression relationships between the occurrence of neonatal chemokines concentrations in umbilical cord blood and mode and time of delivery.

RESULTS

Concentrations of CXC chemokines in late-preterm neonates were the same as those in term neonates. RANTES concentrations in late-preterm cord blood were significantly lower than concentrations in term cord blood. Concentrations of the CC chemokine - RANTES (CCL5) - were noted to be lower in neonates born to cesarean section than in neonates born vaginally. Any anesthetic taken by the mothers during cesarean section did not affect CC chemokine production in the cord blood of full-term neonates. In a logistic regression model including gestational age as a variable, late-preterm delivery was associated with RANTES concentrations (OR = 3.8). After adjustment for variable mode of delivery in regression model, RANTES concentration (OR = 4.75).

CONCLUSION

Both late-preterm and cesarean delivery are essential risk factors of low RANTES (CCL5) concentrations in the umbilical cord blood.

Transfusion-related acute gut injury: necrotizing enterocolitis in very low birth weight neonates after packed red blood cell transfusion

OBJECTIVE

This is a repeat cohort study in which we sought to determine whether an association of necrotizing enterocolitis (NEC) <48 hours of a packed red blood cells (PRBC) transfusion was a prior sampling artifact.

STUDY DESIGN

All very low birth weight neonates with NEC Stage ≥ IIB admitted over an 18-month period were categorized for NEC: (1) <48 hours after a PRBC transfusion; (2) unrelated to the timing of PRBCs; and (3) never transfused.

RESULTS

Eight hundred eighty-three admissions over 18 months were reviewed; 256 were very low birth weight that resulted in 36 NEC cases and 25% were associated with PRBC (n = 9). PRBC-associated cases had lower birth weight, hematocrit, and rapid onset of signs (<5 hours). The timing of association of PRBC transfusion and NEC differed from random, showing a distribution that was not uniform over time (χ(2) = 170.7, df = 40; P < .000001) consistent with the possibility of a causative relationship in certain cases of NEC. Current weight at onset of NEC did not differ; however, the more immature the neonate the later the onset of NEC creating a curious centering of occurrence at a median of 31 weeks postconceptual age.

CONCLUSIONS

We conclude that PRBC-related NEC exists. Transfusion-related acute gut injury is an acronym we propose to characterize a severe neonatal gastrointestinal reaction proximal to a transfusion of PRBCs for anemia. The convergence at 31 weeks postconceptual age approximates the age of presentation of other O(2) delivery and neovascularization syndromes, suggesting a link to a generalized systemic maturational mechanism.

Nutritional modulation of the gut microbiota and immune system in preterm neonates susceptible to necrotizing enterocolitis

The gastrointestinal inflammatory disorder, necrotizing enterocolitis (NEC), is among the most serious diseases for preterm neonates. Nutritional, microbiological and immunological dysfunctions all play a role in disease progression but the relationship among these determinants is not understood. The preterm gut is very sensitive to enteral feeding which may either promote gut adaptation and health, or induce gut dysfunction, bacterial overgrowth and inflammation. Uncontrolled inflammatory reactions may be initiated by maldigestion and impaired mucosal protection, leading to bacterial overgrowth and excessive nutrient fermentation. Tumor necrosis factor alpha, toll-like receptors and heat-shock proteins are identified among the immunological components of the early mucosal dysfunction. It remains difficult, however, to distinguish the early initiators of NEC from the later consequences of the disease pathology. To elucidate the mechanisms and identify clinical interventions, animal models showing spontaneous NEC development after preterm birth coupled with different forms of feeding may help. In this review, we summarize the literature and some recent results from studies on preterm pigs on the nutritional, microbial and immunological interactions during the early feeding-induced mucosal dysfunction and later NEC development. We show that introduction of suboptimal enteral formula diets, coupled with parenteral nutrition, predispose to disease, while advancing amounts of mother's milk from birth (particularly colostrum) protects against disease. Hence, the transition from parenteral to enteral nutrition shortly after birth plays a pivotal role to secure gut growth, digestive maturation and an appropriate response to bacterial colonization in the sensitive gut of preterm neonates.

Immunological investigation of the hepatic tissue from infants with biliary atresia

PURPOSE

Matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors [tissue inhibitors of metalloproteinases (TIMPs)] have been implicated in tissue injury and remodeling in many organs. The objective of this study was to evaluate the expression of MMP-3 and -9, and TIMP-1, -2, and -3 and their relationship to liver fibrosis in infants with biliary atresia.

METHODS

The expression of MMP-3 and-9 and TIMP-1, -2 and -3 was investigated in liver tissue samples of nine patients with biliary atresia. In addition, the expression of CCR-4 and CCR-5 was analyzed to investigate the activation of Th1 and Th2 cells. The mRNA levels were measured by semiquantitative reverse transcriptase polymerase chain reaction.

RESULTS

The expression of MMP-3 was higher than that of MMP-9 in all samples (P < 0.01). The expression of TIMP-1 was higher than that of TIMP-2 and -3 in all samples (P < 0.01). The expression of CCR-5 was higher than that of CCR-4 (P < 0.05), which implied higher activation of Th1 cells relative to Th2 cells.

CONCLUSION

Our findings suggest that MMP-3, possibly induced by Th1 cytokines, and its balance with TIMP-1, may be one of the factors involved in the pathogenesis of biliary atresia.

Association of preterm birth with sustained postnatal inflammatory response

OBJECTIVE

To investigate fetal or neonatal inflammatory patterns based on 25 inflammatory markers in neonatal dried blood spots samples from infants born preterm and term, collected several days after birth.

METHODS

Dried blood spots samples from 160 neonates were analyzed for 25 inflammatory markers using multiplex technology: 26 neonates born very preterm (before 32 weeks of gestation), drawn at a mean 6 days (95% confidence interval [CI], 5-7 days) after birth; 52 born preterm (32-36 weeks of gestation), drawn at mean 5 days (95% CI, 5-6 days) after birth; and 82 born at term (at or after 37 weeks of gestation), drawn at mean 5 days (95% CI, 5-5 days) after birth. Markers statistically significantly associated with preterm birth were analyzed in a multivariable model together with maternal and neonatal risk factors for preterm birth.

RESULTS

Elevated levels of interleukin (IL)-1beta, IL-6, soluble IL-6ralpha, IL-8, matrix metalloproteinase-9, and transforming growth factor-beta1 and decreased levels of IL-18, brain-derived neurotrophic factor, and C-reactive protein were associated with preterm birth. Maternal risk factors could explain only an increase of IL-1beta, whereas neonatal factors could explain several of the elevated and decreased inflammatory markers in the dried blood spots samples from the infants born preterm compared with the infants born at term.

CONCLUSION

The differences in levels of inflammatory markers in dried blood spots samples from infants born preterm compared with infants born at term supports the hypothesis that inflammation of fetal origin might be a cause of preterm birth.

LEVEL OF EVIDENCE

II.