Early life: gut microbiota and immune development in infancy

Leptin and adiponectin supplementation modifies mesenteric lymph node lymphocyte composition and functionality in suckling rats

At birth, when immune responses are insufficient, there begins the development of the defence capability against pathogens. Leptin and adiponectin, adipokines that are present in breast milk, have been shown to play a role in the regulation of immune responses. We report here, for the first time, the influence of in vivo adipokine supplementation on the intestinal immune system in early life. Suckling Wistar rats were daily supplemented with leptin (0·7 μg/kg per d, n 36) or adiponectin (35 μg/kg per d, n 36) during the suckling period. The lymphocyte composition, proliferation and cytokine secretion from mesenteric lymph node lymphocytes (on days 14 and 21), as well as intestinal IgA and IgM concentration (day 21), were evaluated. At day 14, leptin supplementation significantly increased the TCRαβ + cell proportion in mesenteric lymph nodes, in particular owing to an increase in the TCRαβ + CD8+ cell population. Moreover, the leptin or adiponectin supplementation promoted the early development CD8+ cells, with adiponectin being the only adipokine capable of enhancing the lymphoproliferative ability at the end of the suckling period. Although leptin decreased intestinal IgA concentration, it had a trophic effect on the intestine in early life. Supplementation of both adipokines modulated the cytokine profile during (day 14) and at the end (day 21) of the suckling period. These results suggest that leptin and adiponectin during suckling play a role in the development of mucosal immunity in early life.

Infant Complementary Feeding of Prebiotics for theMicrobiome and Immunity

Complementary feeding transitions infants from a milk-based diet to solid foods, providing essential nutrients to the infant and the developing gut microbiome while influencing immune development. Some of the earliest microbial colonisers readily ferment select oligosaccharides, influencing the ongoing establishment of the microbiome. Non-digestible oligosaccharides in prebiotic-supplemented formula and human milk oligosaccharides promote commensal immune-modulating bacteria such as Bifidobacterium, which decrease in abundance during weaning. Incorporating complex, bifidogenic, non-digestible carbohydrates during the transition to solid foods may present an opportunity to feed commensal bacteria and promote balanced concentrations of beneficial short chain fatty acid concentrations and vitamins that support gut barrier maturation and immunity throughout the complementary feeding window.

DHA-phospholipids (DHA-PL) and EPA-phospholipids (EPA-PL) prevent intestinal dysfunction induced by chronic stress

DHA-PL and EPA-PL may effectively protect mice against intestinal dysfunction under chronic stress exposure.

Gut microbiota and pediatric obesity/non-alcoholic fatty liver disease

Huge amount microorganisms resides in human intestine, and many contribute to the maturation and homeostasis of immune system. The diversity of gut ecology are affected by the gestational age, delivery type, feeding sources, and antibiotics use in neonates. Recent studies pointed out that disturbance of gut microbiota, so called dysbiosis, could result in several pediatric diseases including obesity, non-alcoholic fatty liver disease (NAFLD), metabolic syndromes, allergic diseases, and inflammatory bowel diseases. However, there are no single species can be proven to play a key factor in pediatric obesity and NAFLD at present. Various probiotics may confer benefit to these gut microbiota-related pediatric diseases. The clinical application is still limited. This review article aimed to elucidate evidently the relationship between gut microbiota and pediatric obesity/NAFLD and to discuss the potential probiotics use in pediatric obesity and NAFLD.

Strategies for the Preservation, Restoration and Modulation of the Human Milk Microbiota. Implications for Human Milk Banks and Neonatal Intensive Care Units

Studies carried in the last years have revealed that human milk contains a site-specific microbiota and constitutes a source of potentially beneficial bacteria to the infant gut. Once in the infant gut, these bacteria contribute to the assembly of a physiological gut microbiota and may play several functions, contributing to infant metabolism, protection against infections, immunomodulation or neuromodulation. Many preterm neonates are fed with pasteurized donor's human milk (DHM) or formula and, therefore, are devoid of contact with human milk microbes. As a consequence, new strategies are required to allow the exposition of a higher number of preterm infants to the human milk microbiota early in life. The first strategy would be to promote and to increase the use of own mother's milk (OMM) in Neonatal Intensive Care Units (NICUs). Even small quantities of OMM can be very valuable since they would be added to DHM in order to microbiologically "customize" it. When OMM is not available, a better screening of donor women, including routine cytomegalovirus (CMV) screening of milk, may help to avoid the pasteurization of the milk provided by, at least, a relevant proportion of donors. Finally, when pasteurized DHM or formula are the only feeding option, their supplementation with probiotic bacteria isolated from human milk, such as lactic acid bacteria or bifidobacteria, may be an alternative to try to restore a human milk-like microbiota before feeding the babies. In the future, the design of human milk bacterial consortia (minimal human milk microbiotas), including well characterized strains representative of a healthy human milk microbiota, may be an attractive strategy to provide a complex mix of strains specifically tailored to this target population.

Isolation and Characterization of Potentially Probiotic Bacterial Strains from Mice: Proof of Concept for Personalized Probiotics

Modulation of the gut microbiota through the use of probiotics has been widely used to treat or prevent several intestinal diseases. However, inconsistent results have compromised the efficacy of this approach, especially in severe conditions such as inflammatory bowel disease (IBD). The purpose of our study was to develop a personalized probiotic strategy and assess its efficacy in a murine model of intestinal inflammation. Commensal bacterial strains were isolated from the feces of healthy mice and then administered back to the host as a personalized treatment in dextran sodium sulfate (DSS)-induced colitis. Colonic tissues were collected for histological analysis and to investigate inflammatory markers such as Il-1β, Il-6, TGF-β, and Il-10, and the enzyme myeloperoxidase as a neutrophil marker. The group that received the personalized probiotic showed reduced susceptibility to DSS-colitis as compared to a commercial probiotic. This protection was characterized by a lower disease activity index and reduced histopathological damage in the colon. Moreover, the personalized probiotic was more effective in modulating the host immune response, leading to decreased Il-1β and Il-6 and increased TGF-β and Il-10 expression. In conclusion, our study suggests that personalized probiotics may possess an advantage over commercial probiotics in treating dysbiotic-related conditions, possibly because they are derived directly from the host's own microbiota.

Developmental programming of aging trajectory

There is accumulating evidence that aging phenotype and longevity may be developmentally programmed. Main mechanisms linking developmental conditions to later-life health outcomes include persistent changes in epigenetic regulation, (re)programming of major endocrine axes such as growth hormone/insulin-like growth factor axis and hypothalamic-pituitary-adrenal axis and also early-life immune maturation. Recently, evidence has also been generated on the role of telomere biology in developmental programming of aging trajectory. In addition, persisting changes of intestinal microbiota appears to be crucially involved in these processes. In this review, experimental and epidemiological evidence on the role of early-life conditions in programming of aging phenotypes are presented and mechanisms potentially underlying these associations are discussed.

Compositional Dynamics of the Milk Fat Globule and Its Role in Infant Development

Human milk is uniquely optimized for the needs of the developing infant. Its composition is complex and dynamic, driven primarily by maternal genetics, and to a lesser extent by diet and environment. One important component that is gaining attention is the milk fat globule (MFG). The MFG is composed of a triglyceride-rich core surrounded by a tri-layer membrane, also known as the milk fat globule membrane (MFGM) that originates from mammary gland epithelia. The MFGM is enriched with glycerophospholipids, sphingolipids, cholesterol, and proteins, some of which are glycosylated, and are known to exert numerous biological roles. Mounting evidence suggests that the structure of the MFG and bioactive components of the MFGM may benefit the infant by aiding in the structural and functional maturation of the gut through the provision of essential nutrients and/or regulating various cellular events during infant growth and immune education. Further, antimicrobial peptides and surface carbohydrate moieties surrounding the MFG might have a pivotal role in shaping gut microbial populations, which in turn may promote protection against immune and inflammatory diseases early in life. This review seeks to: (1) understand the components of the MFG, as well as maternal factors including genetic and lifestyle factors that influence its characteristics; (2) examine the potential role of this milk component on the intestinal immune system; and (3) delineate the mechanistic roles of the MFG in infant intestinal maturation and establishment of the microbiota in the alimentary canal.

Decreased allergy incidence in children supplemented with E. coli O83:K24:H31 and its possible modes of action

The growing knowledge of the key role of microbiota in the maturation of neonatal immune system suggests that manipulation of microbiota could be exploited in hampering allergy development. In this study, Escherichia coli O83:K24:H31 (EcO83) was administered to newborns that were followed prospectively. Several immunological characteristics (cytokines, specific IgE, total T regulatory cells (Treg) and subpopulation of natural Treg (nTreg) and induced Treg (iTreg)) were tested in peripheral blood of 8-year-old children. Incidence of allergic disease was decreased in EcO83 supplemented children and significantly elevated levels of IL-10 and IFN-ɣ were detected in serum of EcO83 supplemented children. Probiotic supplementation did not influence the numbers of the total Treg population but their functional capacity (intracellular expression of IL-10) was significantly increased in children supplemented with EcO83 in comparison to non-supplemented children. Morover, decreased proportion of iTreg was present in peripheral blood of non-supplemented in comparison to EcO83 supplemented children. Finally, stimulation of cord blood cells with EcO83 promoted both gene expression and secretion of IL-10 and IFN-ɣ suggesting that beneficial effect of EcO83 in prevention of allergy development could be mediated by promotion of regulatory responses (by IL-10) and Th1 immune response (by IFN-ɣ).

Origination, change, and modulation of geriatric disease-related gut microbiota during life

The age-related changes in the diversity and composition of the gut microbiota are well described in recent studies. These changes have been suggested to be influenced by age-associated weakening of the immune system and low-grade chronic inflammation, resulting in numerous age-associated pathological conditions. Gut microbiota homeostasis is important throughout the life of the host by providing vital functions to regulate various immunological functions and homeostasis. Based on published results, we summarize the relationship between the gut microbiota and aging-related diseases, especially Parkinson's disease, immunosenescence, rheumatoid arthritis, bone loss, and metabolic syndrome. The change in composition of the gut microbiota and gut ecosystem during life and its influence on the host immunologic and metabolic phenotype are also analyzed to determine factors that affect aging-related diseases. Approaches to maintain host health and prevent or cure geriatric diseases are also discussed.

Current status of laboratory and imaging diagnosis of neonatal necrotizing enterocolitis

Necrotizing enterocolitis continues to be a devastating disease process for very low birth weight infants in Neonatal Intensive Care Units. The aetiology and pathogenesis of necrotizing enterocolitis are not definitively understood. It is known that necrotizing enterocolitis is secondary to a complex interaction of multiple factors that results in mucosal damage, which leads to intestinal ischemia and necrosis. Advances in neonatal care, including resuscitation and ventilation support technology, have seen increased survival rates among premature neonates and a concomitant detection in the incidence of this intestinal disease.Diagnosis can be difficult, and identifying infants at the onset of disease remains a challenge. Early diagnosis, which relies on imaging findings, and initiation of prompt therapy are essential to limit morbidity and mortality. Moreover, early management is critical and life-saving.This review summarizes what is known on the laboratory and instrumental diagnostic strategies needed to improve neonatal outcomes and, possibily, to prevent the onset of an overt necrotizing enterocolitis.

The Mammalian Intestinal Microbiome: Composition, Interaction with the Immune System, Significance for Vaccine Efficacy, and Potential for Disease Therapy

The mammalian gut is colonized by a large variety of microbes, collectively termed ‘the microbiome’. The gut microbiome undergoes rapid changes during the first few years of life and is highly variable in adulthood depending on various factors. With the gut being the largest organ of immune responses, the composition of the microbiome of the gut has been found to be correlated with qualitative and quantitative differences of mucosal and systemic immune responses. Animal models have been very useful to unravel the relationship between gut microbiome and immune responses and for the understanding of variations of immune responses to vaccination in different childhood populations. However, the molecular mechanisms underlying optimal immune responses to infection or vaccination are not fully understood. The gut virome and gut bacteria can interact, with bacteria facilitating viral infectivity by different mechanisms. Some gut bacteria, which have a beneficial effect on increasing immune responses or by overgrowing intestinal pathogens, are considered to act as probiotics and can be used for therapeutic purposes (as in the case of fecal microbiome transplantation).

Vancomycin and ceftriaxone can damage intestinal microbiota and affect the development of the intestinal tract and immune system to different degrees in neonatal mice

This study aimed to determine how antibiotic-driven intestinal dysbiosis impairs the development and differentiation of the digestive tract and immune organs of host animals. BALB/C neonatal mice were orally administered ceftriaxone or vancomycin from postnatal day 1 to day 21 and sacrificed on day 21. The diversity and abundance of the intestinal bacteria, morphological changes and barrier function of intestinal tract, and the splenic CD4+CD25+Foxp3+ T cells were investigated. The gut microbiota and intestinal tissue were damaged, and the numbers of Ki67-, Muc2- and ZO-1-positive cells were significantly decreased in the antibiotic treatment groups. Furthermore, the administration of ceftriaxone, but not vancomycin, led to a significant reduction in the abundance of splenic CD4+CD25+Foxp3+ T cells. Each antibiotic caused intestinal dysbiosis and characteristically influenced the regeneration of intestinal epithelial cells, formation of the intestinal mucus layer and tight junctions, and differentiation of splenic Foxp3+ Treg cells of the neonatal mice before any clinical side effects were observed. The potent ability of each antibiotic to affect the makeup of intestinal commensal microbiota may be a key determinant of the spectrum of antibiotics and influence the health of the host animal, at least partly.

Bacteriophages as New Human Viral Pathogens

The pathogenesis of numerous human multifaceted devastating diseases, including a variety of neurodegenerative and autoimmune diseases, is associated with alterations in the gut microbiota; however, the underlying mechanisms are not completely understood. Our recent human metagenome and phagobiota proteome analyses and studies in relevant animal models suggested that bacterial viruses might be implicated in the progression and maintenance of at least some pathologies, including those associated with protein misfolding. Here, for the first time, we propose the concept of bacteriophages as human pathogens. We suggest that bacterial viruses have different ways to directly and indirectly interact with eukaryotic cells and proteins, leading to human diseases. Furthermore, we suggest different causes of bacteriophages infection on the basis of the unique ways of interplay of phages, microbiota, and the human host. This concept opens a discussion of the role of bacteriophages as previously overlooked pathogenic factors and suggests that bacterial viruses have to be further explored as a diagnostic and treatment target for therapeutic intervention.

Inflammatory bowel disease and immunonutrition: novel therapeutic approaches through modulation of diet and the gut microbiome

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract, thought to at least in part reflect an aberrant immune response to gut bacteria. IBD is increasing in incidence, particularly in populations that have recently immigrated to western countries. This suggests that environmental factors are involved in its pathogenesis. We hypothesize that the increase in IBD rates might reflect the consumption of an unhealthy Western diet, containing excess calories and lacking in key nutritional factors, such as fibre and vitamin D. Several recent studies have determined that dietary factors can dramatically influence the activation of immune cells and the mediators they release through a process called immunonutrition. Moreover, dietary changes can profoundly affect the balance of beneficial versus pathogenic bacteria in the gut. This microbial imbalance can alter levels of microbiota-derived metabolites that in turn can influence innate and adaptive intestinal immune responses. If the diet-gut microbiome disease axis does indeed underpin much of the 'western' influence on the onset and progression of IBD, then tremendous opportunity exists for therapeutic changes in lifestyle, to modulate the gut microbiome and to correct immune imbalances in individuals with IBD. This review highlights four such therapeutic strategies - probiotics, prebiotics, vitamin D and caloric restriction - that have the potential to improve and add to current IBD treatment regimens.

Appropriate dose of Lactobacillus buchneri supplement improves intestinal microbiota and prevents diarrhoea in weaning Rex rabbits

This study examined the effects on intestinal microbiota and diarrhoea of Lactobacillus buchneri supplementation to the diet of weaning Rex rabbits. To this end, rabbits were treated with L. buchneri at two different doses (LC: 104 cfu/g diet and HC: 105 cfu/g diet) for 4 weeks. PCR-DGGE was used to determine the diversity of the intestinal microbiota, while real-time PCR permitted the detection of individual bacterial species. ELISA and real-time PCR allowed the identification of numerous cytokines in the intestinal tissues. Zonula occludens-1, polymeric immunoglobulin receptor and immunoglobulin A genes were examined to evaluate intestinal barriers. Results showed that the biodiversity of the intestinal microbiota of weaning Rex rabbits improved in the whole tract of the treated groups. The abundance of most detected bacterial species was highly increased in the duodenum, jejunum and ileum after L. buchneri administration. The species abundance in the HC group was more increased than in the LC group when compared to the control. Although the abundance of Enterobacteriaceae exhibited a different pattern, Escherichia coli was inhibited in all treatment groups. Toll-like receptor (TLR)2 and TLR4 genes were down-regulated in all intestinal tissues as the microbiota changed. In the LC group, the secretion of the inflammatory cytokine tumour necrosis factor-α was reduced, the gene expression of the anti-inflammatory cytokine interleukin (IL)-4 was up-regulated and the expression of intestinal-barrier-related genes was enhanced. Conversely, IL-4 expression was increased and the expression of other tested genes did not change in the HC group. The beneficial effects of LC were greater than those of HC or the control in terms of improving the daily weight gain and survival rate of weaning Rex rabbits and reducing their diarrhoea rate. Therefore, 104 cfu/g L. buchneri treatment improved the microbiota of weaning Rex rabbits and prevented diarrhoea in these animals.

Fecal microbiota in the female prairie vole (Microtus ochrogaster)

We examined the fecal microbiota of female prairie voles. This species is socially and, likely, sexually monogamous, and thus serves as a valuable model in which to examine the interaction between the microbiota-gut-brain axis and social behavior. At present, little is known about the gastrointestinal microbiota of prairie voles; therefore, we performed a first characterization of the fecal microbiota using 16S rRNA gene amplicon sequencing. Semiconductor sequencing technology on an Ion Torrent PGM platform was used to assess the composition of fecal microbiotas from twelve female prairie voles. Following quality filtering, 1,017,756 sequencing reads were classified from phylum to genus level. At the phylum level, Firmicutes, Bacteroidetes, and Saccharibacteria were the predominant taxa, while the Bacteriodales, Erysipelotrichaceae, Ruminococcaceae, and Lachnospiraceae contributed the most dominant microbial groups and genera. Microbial community membership was most similar between vole sibling pairs, but consideration of taxon abundances weakened these associations. The interdependence of host factors such as genetics and behavior with the gastrointestinal microbiota is likely to be particularly pronounced in prairie voles. Our pilot characterization of the prairie vole intestinal microbiota revealed a microbial community composition remarkably consistent with the monogastric alimentary system of these rodents and their diet rich in complex plant carbohydrates. The highly social nature of these animals poses specific challenges to microbiome analyses that nonetheless are valuable for advancing research on the microbiota-gut-brain-behavior axis. Our study provides an important basis for future microbiome research in this emerging model organism for studying social behavior.

Regulation of Allergic Immune Responses by Microbial Metabolites

Emerging evidence demonstrates that the microbiota plays an essential role in shaping the development and function of host immune responses. A variety of environmental stimuli, including foods and commensals, are recognized by the host through the epithelium, acting as a physical barrier. Two allergic diseases, atopic dermatitis and food allergy, are closely linked to the microbiota, because inflammatory responses occur on the epidermal border. The microbiota generates metabolites such as short-chain fatty acids and poly-γ-glutamic acid (γPGA), which can modulate host immune responses. Here, we review how microbial metabolites can regulate allergic immune responses. Furthermore, we focus on the effect of γPGA on allergic T helper (Th) 2 responses and its therapeutic application.

Cesarean Delivery and Risk of Infant Leukemia: A Report from the Children's Oncology Group

Background: Studies have reported increased risks of pediatric acute lymphoblastic leukemia (ALL) among children born by cesarean delivery (CD). However, no previous study has examined the impact of CD on risk of infant leukemia specifically.Methods: In this study, 443 infants diagnosed with acute leukemia, including both ALL and acute myelogenous leukemia (AML), were identified at Children's Oncology Group institutions between January 1996 and December 2006; 324 controls frequency matched by year of birth were identified though random digit dialing and random selection from U.S. birth registries. Using interview data and, for a subset of participants, medical record data, we analyzed CD overall and by indications that likely resulted in pre-labor CD (PLCD) or emergency CD (ECD). Odds ratios (ORs) and 95% confidence intervals (CIs) for risk of ALL and AML were estimated using multivariable unconditional logistic regression models, adjusted for year of birth, birth weight, and maternal race.Results: We observed an increased point estimate for the association between CD and ALL (OR, 1.52 and 95% CI, 1.02-2.25). We did not observe an association between CD and AML (OR, 1.02 and 95% CI, 0.64-1.62). In analyses of indication for CD, we observed elevated effect estimates for the associations of both PLCD and ECD and infant ALL.Conclusions: Our analysis suggests an increased risk of infant ALL following CD, including both PLCD and ECD. Altered microbiota colonization may be involved in development of leukemia in infants, but clear biological mechanisms have yet to be determined.Impact: This study provides the first in-depth examination of CD and infant leukemia. Cancer Epidemiol Biomarkers Prev; 27(4); 473-8. ©2018 AACR.

Non-digestible carbohydrates in infant formula as substitution for human milk oligosaccharide functions: Effects on microbiota and gut maturation

Human milk (HM) is the golden standard for nutrition of newborn infants. Human milk oligosaccharides (HMOs) are abundantly present in HM and exert multiple beneficial functions, such as support of colonization of the gut microbiota, reduction of pathogenic infections and support of immune development. HMO-composition is during lactation continuously adapted by the mother to accommodate the needs of the neonate. Unfortunately, for many valid reasons not all neonates can be fed with HM and are either totally or partly fed with cow-milk derived infant formulas, which do not contain HMOs. These cow-milk formulas are supplemented with non-digestible carbohydrates (NDCs) that have functional effects similar to that of some HMOs, since production of synthetic HMOs is challenging and still very expensive. However, NDCs cannot substitute all HMO functions. More efficacious NDCs may be developed and customized for specific groups of neonates such as pre-matures and allergy prone infants. Here current knowledge of HMO functions in the neonate in view of possible replacement of HMOs by NDCs in infant formulas is reviewed. Furthermore, methods to expedite identification of suitable NDCs and structure/function relationships are reviewed as in vivo studies in babies are impossible.

Diversity of Human Milk Oligosaccharides and Effects on Early Life Immune Development

One of the well-known features of human milk, is the capacity to protect against the risk and impact of neonatal infections, as well as to influence the onset of allergic and metabolic disease manifestations. The major objective of this review is to provide a detailed overview regarding the role of human milk, more specifically the diversity in human milk oligosaccharides (HMOS), on early life immune development. Novel insights in immune modulatory effects of HMOS obtained by in vitro as well as in vivo studies, adds to the understanding on how early life nutrition may impact immune development. Extensive description and analysis of single HMOS contributing to the diversity within the composition provided during breastfeeding will be discussed with specific emphasis on immune development and the susceptibility to neonatal and childhood infections.

Development of Microbiota in Infants and its Role in Maturation of Gut Mucosa and Immune System

Dysbiosis of the gut microbiota has been associated with increasing numbers of diseases, including obesity, diabetes, inflammatory bowel disease, asthma, allergy, cancer and even neurologic or behavioral disorders. The other side of the coin is that a healthy microbiota leads to a healthy human development, to a mature and well trained immune system and to an efficient metabolic machinery. What we have learned in adults is in the end the result of a good start, a programmed, healthy development of the microbiota that must occur in the early years of life, probably even starting during the fetal stage. This review aims to present and discuss reports that helps us understand what we have learned of the development of microbiota during the early times of life, from pregnancy to delivery to the early years after birth. The impact of the establishment of "healthy" bacterial communities on human surfaces in the maturation of epithelia, immune system and metabolism will also be discussed. The right process of maturation of the bacterial communities that establish a symbiosis with human surfaces depends on a number of environmental, genetic and temporal factors that need to be understand in order to have tools to monitor a healthy development and eventually intervene to correct undesired courses.

Weaning stress and gastrointestinal barrier development: Implications for lifelong gut health in pigs

The gastrointestinal (GI) barrier serves a critical role in survival and overall health of animals and humans. Several layers of barrier defense mechanisms are provided by the epithelial, immune and enteric nervous systems. Together they act in concert to control normal gut functions (e.g., digestion, absorption, secretion, immunity, etc.) whereas at the same time provide a barrier from the hostile conditions in the luminal environment. Breakdown of these critical GI functions is a central pathophysiological mechanism in the most serious GI disorders in pigs. This review will focus on the development and functional properties of the GI barrier in pigs and how common early life production stressors, such as weaning, can alter immediate and long-term barrier function and disease susceptibility. Specific stress-related pathophysiological mechanisms responsible for driving GI barrier dysfunction induced by weaning and the implications to animal health and performance will be discussed.

They Are What You Eat: Can Nutritional Factors during Gestation and Early Infancy Modulate the Neonatal Immune Response?

The ontogeny of the human immune system is sensitive to nutrition even in the very early embryo, with both deficiency and excess of macro- and micronutrients being potentially detrimental. Neonates are particularly vulnerable to infectious disease due to the immaturity of the immune system and modulation of nutritional immunity may play a role in this sensitivity. This review examines whether nutrition around the time of conception, throughout pregnancy, and in early neonatal life may impact on the developing infant immune system.

Early Antibiotic Exposure in Low-resource Settings Is Associated With Increased Weight in the First Two Years of Life

OBJECTIVES

The potential growth-promoting effects of antibiotics are not well understood among undernourished children in environments with high pathogen exposure. We aimed to assess whether early antibiotic exposure duration and class were associated with growth to 2 years of age across 8 low-resource sites in the MAL-ED birth cohort study.

METHODS

We followed 1954 children twice per week from birth to 2 years to record maternally reported antibiotic exposures and measure anthropometry monthly. We estimated the associations between antibiotic exposure before 6 months of age and weight-for-age and length-for-age (LAZ) z scores to 2 years. We assessed the impact of class-specific exposures and duration, and compared these results to effects of antibiotic exposures after 6 months of age.

RESULTS

Antibiotic use before 6 months of age was associated with increased weight from 6 months to 2 years, whereas associations with length were less consistent across sites and antibiotic classes. Compared to unexposed children, 2 or more courses of metronidazole, macrolides, and cephalosporins were associated with adjusted increases in weight-for-age of 0.24 (95% confidence interval (CI): 0.04, 0.43), 0.23 (95% CI: 0.05, 0.42), and 0.19 (95% CI: 0.04, 0.35) from 6 months to 2 years, respectively.

CONCLUSIONS

Antibiotic use in low-resource settings was most associated with the ponderal growth of children who had multiple exposures to antibiotics with broad spectrum and anaerobic activity in early infancy. Opportunities for rational and targeted antibiotic therapy in low resource settings may also promote short-term weight gain in children, although longer-term physical growth and metabolic impacts are unknown.

Different capacity of in vitro generated myeloid dendritic cells of newborns of healthy and allergic mothers to respond to probiotic strain E. coli O83:K24:H31

Allergic diseases belong to one of the most common diseases with steadily increasing incidence even among young children. There is an urgent need to identify a prognostic marker pointing to increased risk of allergy development enabling early preventive measures introduction. It has been shown that administration of selected probiotic strains or mixtures could prevent allergy development. In our study, we have tested the capacity of probiotic strain Escherichia coli O83:K24:H31 (E. coli O83) to promote dendritic cell (DC) maturation and polarisation of immune responses. Increased presence of activation marker CD83 was observed on DC stimulated by E. coli O83 and DC of newborns of allergic mothers have significantly more increased cell surface presence of CD83 in comparison to children of healthy mothers. Increased gene expression and secretion of IL-10 was detected in DC stimulated with E. coli O83 being higher in DC of newborns of healthy mothers in comparison to allergic ones. Generally, increased presence of intracellular cytokines (IL-4, IL-13, IFN-gamma, IL-17A, IL-22, IL-10) was detected in CD4+ T cells cocultured with DC of children of allergic mothers in comparison to healthy ones. E. coli O83 primed DC significantly increased IL-10 and IL-17A in CD4 T cells of newborns of healthy mothers in comparison to the levels detected in CD4 T cells cocultured with control non-stimulated DC. We can conclude E. coli O83 induces dendritic cell maturation and IL-10 production in DC. Newborns of allergic mothers have generally increased reactivity of both DC and CD4 T cells which together with decreased capacity of DC of newborns of allergic mothers to produce IL-10 could support inappropriate immune responses development after allergen encounter.

Intestinal dysbiosis and probiotic applications in autoimmune diseases

In humans, a complex interaction between the host immune system and commensal microbiota is required to maintain gut homeostasis. In this symbiotic relationship, the microbiota provides carbohydrate fermentation and digestion, vitamin synthesis and gut-associated lymphoid tissue development, as well as preventing colonization by pathobionts, whereas the host offers a niche and nutrients for the survival of the microbiota. However, when this mutualistic relationship is compromised and an altered interaction between immune cells and microorganisms occurs, the gut microbiota may cause or contribute to the establishment of infectious diseases and trigger autoimmune diseases. Researchers have made efforts to clarify the role of the microbiota in autoimmune disease development and find new therapeutic approaches to treat immune-mediated diseases. However, the exact mechanisms involved in the dysbiosis and breakdown of the gut epithelial barrier are currently unknown. Here, we provide a general overview of studies describing gut microbiota perturbations in animal models of autoimmune diseases, such as type 1 diabetes, multiple sclerosis, rheumatoid arthritis and systemic lupus erythematosus. Moreover, we include the main studies concerning dysbiosis in humans and a critical discussion of the existing data on the use of probiotics in these autoimmune diseases.

Necrotizing enterocolitis in premature infants and newborns

Necrotizing enterocolitis (NEC) is the most common acquired disease of the gastrointestinal tract (GIT) in premature infants and newborns. It is defined as an ulcerative inflammation of the intestinal wall. The clinical signs of incipient NEC are often very discrete, and range from localized intestinal symptoms to generalized signs of sepsis. NEC is classified depending on its severity into disease states according to the modified Bell's Classification. Treatment of NEC ranges, depending on its severity, from a conservative therapeutic approach to surgery with resection of the affected parts of the intestine. Mortality is considerably high in extremely small preterm infants reaching up to 42% of the affected children. Measures such as breastfeeding or alternatively nutrition with pasteurized human donor milk from a milk bank, administration of probiotics, avoidance of histamine type II receptor antagonists, and restrictive antibiotic treatment should be considered early on for prevention of NEC.

Mice exposed to infant formula enriched with polyamines: impact on host transcriptome and microbiome

Previous studies using a BALB/cOlaHsd model have shown the impact that the supplementation of infant formula with polyamines has on the modulation of microbial colonization and immune system development. To contribute to deciphering and identifying new complex interactions underlying the host response to polyamines, a systems biology approach integrating data from microbiota along the gastrointestinal tract, lymphocyte populations and immune system gene expression analysis of a lactating mice model fed different diets was carried out. The study design included four different dietary regimens including the following: mice fed by normal lactation; early weaned mice given commercial infant formula; and early weaned mice fed with infant formula enriched with two different concentrations of polyamines. Cluster analysis by principal component analysis and heat map demonstrated that the bacterial communities and immune system status differed between groups. The assessment of the relationship between immune system development, microbiota succession and polyamine supplementation in a global manner proved that the supplementation of infant formula with polyamines promotes similar microbial communities along the whole gastrointestinal tract, and results in similar lymphocyte populations and expression of immune related-genes to those with the normal lactated milk and the results differ from those with the infant formula without polyamines. Further studies should be conducted in human subjects to verify the current results, as the supplementation of polyamines may resemble the effect of natural breastfeeding practices in the gastrointestinal microbiota and immune system development in a mouse model.

Metaproteomics reveals functional differences in intestinal microbiota development of preterm infants

OBJECTIVE

Development of the gastrointestinal tract and immune system can be modulated by the gut microbiota. Establishment of the intestinal microbiota, in its turn, is affected by host and environmental factors. As such, development of the gut microbiota is greatly impacted in preterm infants, who have an immature gut and are exposed to factors like hospitalization, caesarean section, antibiotics, and respiratory support.

DESIGN

We analyzed fecal microbiota composition and activity of ten preterm infants (gestational age 25-30 weeks; birthweight 630-1750 g) during the first six postnatal weeks through metaproteomics (LC-MS/MS) and 16S-rRNA gene sequencing.

RESULTS

A gestational-age-dependent microbial signature is observed, enabling microbiota-based differentiation between extremely preterm (25-27 weeks gestation) and very preterm (30 weeks gestation) infants. In very preterm infants, the intestinal microbiota developed toward a Bifidobacterium-dominated community and was associated with high abundance of proteins involved in carbohydrate and energy metabolism. Extremely preterm infants remained predominantly colonized by facultative anaerobes and were associated with proteins involved in membrane transport and translation. Delayed colonization by obligate anaerobes could be associated with antibiotic treatment and respiratory support.

CONCLUSION

We speculate that gestational age and its associated intensity of care (e.g. antibiotics and respiratory support) affects intestinal microbiota composition and activity in preterm infants. As the gut microbiota plays a major role in development of the neonate, gestational age and its associated factors could set the stage for early and later life health complications via interference with microbiota development.

Effect of Synbiotic on the Gut Microbiota of Cesarean Delivered Infants: A Randomized, Double-blind, Multicenter Study

We determined the effect of short-chain galacto-oligosaccharides (scGOS), long-chain fructo-oligosaccharides (lcFOS) and Bifidobacterium breve M-16V on the gut microbiota of cesarean-born infants. Infants were randomized to receive a standard formula (control), the same with scGOS/lcFOS and B. breve M-16V (synbiotic), or with scGOS/lcFOS (prebiotic) from birth until week 16, 30 subjects born vaginally were included as a reference group. Synbiotic supplementation resulted in a higher bifidobacteria proportion from day 3/5 (P < 0.0001) until week 8 (P = 0.041), a reduction of Enterobacteriaceae from day 3/5 (P = 0.002) till week 12 (P = 0.016) compared to controls. This was accompanied with a lower fecal pH and higher acetate. In the synbiotic group, B. breve M-16V was detected 6 weeks postintervention in 38.7% of the infants. This synbiotic concept supported the early modulation of Bifidobacterium in C-section born infants that was associated with the emulation of the gut physiological environment observed in vaginally delivered infants.

Intestinal dysbiosis and probiotic applications in autoimmune diseases

In humans, a complex interaction between the host immune system and commensal microbiota is required to maintain gut homeostasis. In this symbiotic relationship, the microbiota provides carbohydrate fermentation and digestion, vitamin synthesis and gut-associated lymphoid tissue development, as well as preventing colonization by pathobionts, whereas the host offers a niche and nutrients for the survival of the microbiota. However, when this mutualistic relationship is compromised and an altered interaction between immune cells and microorganisms occurs, the gut microbiota may cause or contribute to the establishment of infectious diseases and trigger autoimmune diseases. Researchers have made efforts to clarify the role of the microbiota in autoimmune disease development and find new therapeutic approaches to treat immune-mediated diseases. However, the exact mechanisms involved in the dysbiosis and breakdown of the gut epithelial barrier are currently unknown. Here, we provide a general overview of studies describing gut microbiota perturbations in animal models of autoimmune diseases, such as type 1 diabetes, multiple sclerosis, rheumatoid arthritis and systemic lupus erythematosus. Moreover, we include the main studies concerning dysbiosis in humans and a critical discussion of the existing data on the use of probiotics in these autoimmune diseases.

Immune development in HIV-exposed uninfected children born to HIV-infected women

Immunological and clinical findings suggestive of some immune dysfunction have been reported among HIV-exposed uninfected (HEU) children and adolescents. Whether these defects are persistent or transitory is still unknown. HEU pediatric population at birth, 12 months, 6-12 years were evaluated in comparison to healthy age-matched HIV-unexposed controls. Plasma levels of LPS, sCD14, cytokines, lymphocyte immunophenotyping and T-cell receptor excision circles (TREC) were assessed. HEU and controls had similar LPS levels, which remained low from birth to 6-12 years; for plasma sCD14, IL-2, IL-6, IL-7, IL-10, IL-12p70, IL-13, IL-17, IFN-γ, TNF-α, G-CSF, GM-CSF and MCP-1, which increased from birth to 12 months and then decreased at 6-12 years; and for TREC/10⁶ PBMC at birth in HEU and controls. By contrast, plasma MIP-1β levels were lower in HEU than in controls (p=0.009) at 12 months, and IL-4 levels were higher in HEU than controls (p=0.04) at 6-12 years. Immune activation was higher in HEU at 12 months and at 6-12 years than controls based on frequencies of CD38+HLA-DR+CD8+T cells (p=0.05) and of CD38+HLA-DR+CD4+T cells (p=0.006). Resting memory and activated mature B cells increased from birth to 6-12 years in both groups. The development of the immune system in vertically HEU individuals is comparable to the general population in most parameters, but subtle or transient differences exist. Their role in influencing clinical incidences in HEU is unknown.

Diet and microbiota in inflammatory bowel disease: The gut in disharmony

Bacterial colonization of the gut shapes both the local and the systemic immune response and is implicated in the modulation of immunity in both healthy and disease states. Recently, quantitative and qualitative changes in the composition of the gut microbiota have been detected in Crohn's disease and ulcerative colitis, reinforcing the hypothesis of dysbiosis as a relevant mechanism underlying inflammatory bowel disease (IBD) pathogenesis. Humans and microbes have co-existed and co-evolved for a long time in a mutually beneficial symbiotic association essential for maintaining homeostasis. However, the microbiome is dynamic, changing with age and in response to environmental modifications. Among such environmental factors, food and alimentary habits, progressively altered in modern societies, appear to be critical modulators of the microbiota, contributing to or co-participating in dysbiosis. In addition, food constituents such as micronutrients are important regulators of mucosal immunity, with direct or indirect effects on the gut microbiota. Moreover, food constituents have recently been shown to modulate epigenetic mechanisms, which can result in increased risk for the development and progression of IBD. Therefore, it is likely that a better understanding of the role of different food components in intestinal homeostasis and the resident microbiota will be essential for unravelling the complex molecular basis of the epigenetic, genetic and environment interactions underlying IBD pathogenesis as well as for offering dietary interventions with minimal side effects.

Morphogenesis and maturation of the embryonic and postnatal intestine

The intestine is a vital organ responsible for nutrient absorption, bile and waste excretion, and a major site of host immunity. In order to keep up with daily demands, the intestine has evolved a mechanism to expand the absorptive surface area by undergoing a morphogenetic process to generate finger-like units called villi. These villi house specialized cell types critical for both absorbing nutrients from food, and for protecting the host from commensal and pathogenic microbes present in the adult gut. In this review, we will discuss mechanisms that coordinate intestinal development, growth, and maturation of the small intestine, starting from the formation of the early gut tube, through villus morphogenesis and into early postnatal life when the intestine must adapt to the acquisition of nutrients through food intake, and to interactions with microbes.

Role of the Human Breast Milk-Associated Microbiota on the Newborns' Immune System: A Mini Review

The human milk is fundamental for a correct development of newborns, as it is a source not only of vitamins and nutrients, but also of commensal bacteria. The microbiota associated to the human breast milk contributes to create the "initial" intestinal microbiota of infants, having also a pivotal role in modulating and influencing the newborns' immune system. Indeed, the transient gut microbiota is responsible for the initial change from an intrauterine Th2 prevailing response to a Th1/Th2 balanced one. Bacteria located in both colostrum and mature milk can stimulate the anti-inflammatory response, by stimulating the production of specific cytokines, reducing the risk of developing a broad range of inflammatory diseases and preventing the expression of immune-mediated pathologies, such as asthma and atopic dermatitis. The aim of the present Mini Review is to elucidate the specific immunologic role of the human milk-associated microbiota and its impact on the newborn's health and life, highlighting the importance to properly study the biological interactions in a bacterial population and between the microbiota and the host. The Auto Contractive Map, for instance, is a promising analytical methodology based on artificial neural network that can elucidate the specific role of bacteria contained in the breast milk in modulating the infants' immunological response.

Gut microbiome and liver diseases

The gut microbiota has recently evolved as a new important player in the pathophysiology of many intestinal and extraintestinal diseases. The liver is the organ which is in closest contact with the intestinal tract, and is exposed to a substantial amount of bacterial components and metabolites. Various liver disorders such as alcoholic liver disease, non-alcoholic liver disease and primary sclerosing cholangitis have been associated with an altered microbiome. This dysbiosis may influence the degree of hepatic steatosis, inflammation and fibrosis through multiple interactions with the host's immune system and other cell types. Whereas few results from clinical metagenomic studies in liver disease are available, evidence is accumulating that in liver cirrhosis an oral microbiome is overrepresented in the lower intestinal tract, potentially contributing to disease process and severity. A major role for the gut microbiota in liver disorders is also supported by the accumulating evidence that several complications of severe liver disease such as hepatic encephalopathy are efficiently treated by various prebiotics, probiotics and antibiotics. A better understanding of the gut microbiota and its components in liver diseases might provide a more complete picture of these complex disorders and also form the basis for novel therapies.

Preclinical Immunomodulation by the Probiotic Bifidobacterium breve M-16V in Early Life

This study aimed to investigate the effect of supplementation with the probiotic Bifidobacterium breve M-16V on the maturation of the intestinal and circulating immune system during suckling. In order to achieve this purpose, neonatal Lewis rats were supplemented with the probiotic strain from the 6th to the 18th day of life. The animals were weighed during the study, and faecal samples were obtained and evaluated daily. On day 19, rats were euthanized and intestinal wash samples, mesenteric lymph node (MLN) cells, splenocytes and intraepithelial lymphocytes (IEL) were obtained. The probiotic supplementation in early life did not modify the growth curve and did not enhance the systemic immune maturation. However, it increased the proportion of cells bearing TLR4 in the MLN and IEL, and enhanced the percentage of the integrin αEβ7+ and CD62L+ cells in the MLN and that of the integrin αEβ7+ cells in the IEL, suggesting an enhancement of the homing process of naïve T lymphocytes to the MLN, and the retention of activated lymphocytes in the intraepithelial compartment. Interestingly, B. breve M-16V enhanced the intestinal IgA synthesis. In conclusion, supplementation with the probiotic strain B. breve M-16V during suckling improves the development of mucosal immunity in early life.

Changes in the intestinal bacterial community, short-chain fatty acid profile, and intestinal development of preweaned Holstein calves. 1. Effects of prebiotic supplementation depend on site and age

Digestive disorders are common during the first few weeks of life of newborn calves. Prebiotics are nondigestible but fermentable oligosaccharides that modulate growth and activity of beneficial microbial populations, which can result in enhanced gut health and function. Galactooligosaccharides (GOS) have demonstrated such prebiotic potential. In this study, the effect of GOS supplementation on intestinal bacterial community composition and fermentation profiles; intestinal health, development, and function; and growth was evaluated in dairy calves fed for high rates of growth. Eighty male Holstein calves were assigned either to a control treatment consisting of commercial milk replacer or to a GOS-rich (i.e., 3.4% of dry matter) milk replacer treatment. After 2 and 4wk, 8 calves per treatment were slaughtered at each age. Samples of intestinal digesta and tissue were collected for assessment of bacterial communities, short-chain fatty acid concentrations, in vitro measurement of nutrient transport and permeability, histomorphology, and gastrointestinal organ size. The remaining 48 calves continued to wk 8 to measure body growth, nutrient intake, and fecal and respiratory scores. Calves fed GOS displayed greater Lactobacillus and Bifidobacterium relative abundance and more developed intestinal epithelial structures, but also had greater fecal scores presumably related to greater colonic water secretion. Control calves showed slightly better growth and milk dry matter intake. Size of intestinal organs, intestinal nutrient transport, and epithelium paracellular resistance were not affected by treatment. Excessive GOS supplementation had both prebiotic and laxative effects, which led to slightly lower growth performance while promoting commensal bacteria population and greater intestinal epithelium growth.

Effects of prebiotics on immune system and cytokine expression

Nowadays, use of prebiotics as feed and food additives has received increasing interest because of the beneficial effects of prebiotics on the health of animals and humans. One of the beneficial effects of prebiotics is stimulation of immune system, which can be direct or indirect through increasing population of beneficial microbes or probiotics, especially lactic acid bacteria and bifidobacteria, in the gut. An important mechanism of action of probiotics and prebiotics, by which they can affect the immune system, is changing the expression of cytokines. The present review tried to summarize the findings of studies that investigated the effects of prebiotics on immune system with focusing on their effects on cytokine expression. Generally, most of reviewed studies indicated beneficial effects for prebiotics in terms of improving immune system, by increasing the expression of anti-inflammatory cytokines, while reducing the expressions of proinflammatory cytokines. However, most of studies mainly considered the indirect effects of prebiotics on the immune system (through changing the composition and population of gut microbiota), and their direct effects still need to be further studied using prebiotics with different degree of polymerization in different hosts.

Environmental Factors Associated with Altered Gut Microbiota in Children with Eczema: A Systematic Review

Eczema is a common skin condition that impairs children's daily life activities and quality of life. Previous research shows that gut microbiome composition plays an important role in the development of eczema. The present review summarizes evidence on environmental factors related to altered gut microbiota in children with eczema. We searched Medline, PubMed, Embase, and the Cochrane database of Systematic Reviews through October 2015. The search strategy focused on articles published in peer-reviewed, English-language journals with no publication year limit. Only original studies and review articles that reported environmental factors on gut microbiome specific to eczema were included in this review. We selected six studies (total 1990 participants) for full review and identified that the composition of gut microbiota specific to eczema could be influenced by the following environmental factors: length of gestation, mode of delivery, type of feeding, method of treatment, number of older siblings, and other lifestyle factors. There has been inconsistent empirical evidence as to the modulatory effects of gut microbiota on immunological functions in children with eczema. Further research on the environmental-host-microbial interaction is needed to develop a strong base of knowledge for the development and implementation of prevention strategies and policies for eczema.

Caesarean delivery and risk of childhood leukaemia: a pooled analysis from the Childhood Leukemia International Consortium (CLIC)

BACKGROUND

Results from case-control studies have shown an increased risk of acute lymphoblastic leukaemia (ALL) in young children born by caesarean delivery, and prelabour caesarean delivery in particular; however, an association of method of delivery with childhood leukaemia subtypes has yet to be established. We therefore did a pooled analysis of data to investigate the association between childhood leukaemia and caesarean delivery.

METHODS

We pooled data from 13 case-control studies from the Childhood Leukemia International Consortium done in nine countries (Canada, Costa Rica, Egypt, France, Germany, Greece, Italy, New Zealand, and the USA) for births from 1970-2013. We analysed caesarean delivery overall and by indications that probably resulted in prelabour caesarean delivery or emergency caesarean delivery. We used multivariable logistic regression models, adjusted for child's birthweight, sex, age, ethnic origin, parental education, maternal age, and study, to estimate odds ratios (ORs) and 95% CIs for the risk of ALL and acute myeloid leukaemia (AML) in children aged 0-14 years at diagnosis.

FINDINGS

The studies provided data for 8780 ALL cases, 1332 AML cases, and 23 459 controls, of which the birth delivery method was known for 8655 (99%) ALL cases, 1292 (97%) AML cases, and 23 351 (>99%) controls. Indications for caesarean delivery were available in four studies (there were caesarean deliveries for 1061 of 4313 ALL cases, 138 of 664 AML cases, and 1401 of 5884 controls). The OR for all indications of caesarean delivery and ALL was 1·06 (95% CI 0·99-1·13), and was significant for prelabour caesarean delivery and ALL (1·23 [1·04-1·47]; p=0·018). Emergency caesarean delivery was not associated with ALL (OR 1·02 [95% CI 0·81-1·30]). AML was not associated with caesarean delivery (all indications OR 0·99 [95% CI 0·84-1·17]; prelabour caesarean delivery 0·83 [0·54-1·26]; and emergency caesarean delivery 1·05 [0·63-1·77]).

INTERPRETATION

Our results suggest an increased risk of childhood ALL after prelabour caesarean delivery. If this association is causal, maladaptive immune activation due to an absence of stress response before birth in children born by prelabour caesarean delivery could be considered as a potential mechanism.

FUNDING

National Cancer Institute.