Childhood Immune Maturation and Allergy Development: Regulation by Maternal Immunity and Microbial Exposure

A health-promoting role of exclusive breastfeeding on infants through restoring delivery mode-induced gut microbiota perturbations

The establishment of human gut microbiota in early life is closely associated with both short- and long-term infant health. Delivery mode and feeding pattern are two important determinants of infant gut microbiota. In this longitudinal cohort study, we examined the interplay between the delivery mode and feeding pattern on the dynamics of infant gut microbiota from 6 weeks to 6 months post-delivery in 139 infants. We also assessed the relationship between infant respiratory infection susceptibility and gut microbial changes associated with delivery mode and feeding pattern. At 6 weeks postpartum, the composition and structure of gut microbiota of cesarean section-delivered (CSD) infants differed from those of vaginally delivered (VD) infants, with decreased Bacteroides and Escherichia-Shigella and increased Klebsiella, Veillonella, and Enterococcus. At 6 months postpartum, these delivery mode-induced microbial shifts were restored by exclusive breastfeeding, resulting in similar gut microbial profiles between VD and CSD infants who were exclusively breastfed (P = 0.57) and more variable gut microbial profiles between VD and CSD infants who were mixed fed (P < 0.001). We identified that the VD-associated genera were enriched in healthy infants, while the CSD-associated genera were enriched in infants who suffered from respiratory infections. Our findings indicate that exclusive breastfeeding may play a health-promoting role by reducing infant respiratory infection susceptibility through the restoration of gut microbiota perturbations caused by cesarean section.

Primary Prevention of Allergy - Is It Feasible?

The allergy epidemic has been attributed to environmental influences related to urbanization and the modern lifestyle. In this regard, various theories exploring the role of microbes (hygiene, old friends, microbiota, and biodiversity hypotheses), and the epithelial barrier (epithelial, dual allergen exposure and vitamin D hypotheses) have been proposed. These hypotheses have guided clinical studies that led to the formulation of intervention strategies during the proposed window of opportunity dubbed as the "first thousand days." The most significant intervention is a paradigm shift from allergen avoidance to early introduction of allergenic foods, particularly egg and peanut, around 6 months of age for the prevention of food allergy. This recommendation has been adopted globally and included in allergy prevention guidelines. Other strategies with less robust clinical evidence include: encouraging a healthy balanced diet, rich in fish, during pregnancy; continuing allergenic food intake during pregnancy and lactation; vitamin D supplementation in pregnant women with asthma; discouraging social indications for caesarean section delivery; judicious use of antibiotics in early childhood; daily emollient use from birth in high risk babies; and avoiding cow's milk formula use in the first week of life. However, if early supplementation with cow's milk formula is required, continuing at least 10 mL of formula daily until age 2 months may be considered. Translating these strategies to public health and clinical practice is still a work in progress. Long-term population studies are crucial to assess the feasibility of these measures on allergy prevention.

The Association of Prenatal C-Reactive Protein Levels With Childhood Asthma and Atopy

BACKGROUND

The pathogenesis of childhood asthma is complex, and determinants of risk may begin in utero.

OBJECTIVE

To describe the association of systemic prenatal inflammation, measured by plasma C-reactive protein (CRP), with childhood asthma, eczema, and allergic rhinitis.

METHODS

A total of 522 maternal-offspring pairs from the Vitamin D Antenatal Asthma Reduction Trial were included. Prenatal plasma CRP level was measured between 10 and 18 weeks of gestation and between 32 and 38 weeks of gestation. Offspring asthma, eczema, and allergic rhinitis were assessed quarterly between birth and age 6 years. We performed mediation analyses of prenatal CRP on the association between several maternal characteristics and offspring asthma.

RESULTS

Elevated early and late prenatal CRP and an increase in CRP from early to late pregnancy were associated with asthma by age 6 years (early: adjusted odds ratio [aOR], 1.76, 95% CI, 1.12-2.82, P = .02; late: aOR, 2.45, 95% CI, 1.47-4.18, P < .001; CRP increase: aOR, 2.06, 95% CI, 1.26-3.39, P < .004). Prenatal CRP and childhood asthma associations were strengthened among offspring with atopic asthma (early: aOR, 3.78, 95% CI, 1.49-10.64, P = .008; late: aOR, 4.84, 95% CI, 1.68-15.50, P = .005; CRP increase: aOR, 3.01, 95% CI, 1.06-9.16, P = .04). Early and late prenatal CRP mediated 96% and 86% of the association between maternal prepregnancy body mass index and offspring asthma, respectively.

CONCLUSIONS

Higher prenatal CRP and an increase in CRP from early to late pregnancy are associated with childhood asthma. Systemic inflammation during pregnancy associated with modifiable maternal characteristics may be an important determinant of childhood asthma risk.

The associations of maternal and children's gut microbiota with the development of atopic dermatitis for children aged 2 years

BACKGROUND

It is critical to investigate the underlying pathophysiological mechanisms in the development of atopic dermatitis. The microbiota hypothesis suggested that the development of allergic diseases may be attributed to the gut microbiota of mother-offspring pairs. The purpose of this study was to investigate the relationship among maternal-offspring gut microbiota and the subsequent development of atopic dermatitis in infants and toddlers at 2 years old.

METHODS

A total of 36 maternal-offspring pairs were enrolled and followed up to 2 years postpartum in central China. Demographic information and stool samples were collected perinatally from pregnant mothers and again postpartum from their respective offspring at the following time intervals: time of birth, 6 months, 1 year and 2 years. Stool samples were sequenced with the 16S Illumina MiSeq platform. Logistic regression analysis was used to explore the differences in gut microbiota between the atopic dermatitis group and control group.

RESULTS

Our results showed that mothers of infants and toddlers with atopic dermatitis had higher abundance of Candidatus_Stoquefichus and Pseudomonas in pregnancy and that infants and toddlers with atopic dermatitis had higher abundance of Eubacterium_xylanophilum_group at birth, Ruminococcus_gauvreauii_group at 1 year and UCG-002 at 2 years, and lower abundance of Gemella and Veillonella at 2 years. Additionally, the results demonstrated a lower abundance of Prevotella in mothers of infants and toddlers with atopic dermatitis compared to mothers of the control group, although no statistical difference was found in the subsequent analysis.

CONCLUSION

The results of this study support that gut microbiota status among mother-offspring pairs appears to be associated with the pathophysiological development of pediatric atopic dermatitis.

Interplay of Environmental, Individual and Genetic Factors in Rheumatoid Arthritis Provocation

In this review, we explore systemization of knowledge about the triggering effects of non-genetic factors in pathogenic mechanisms that contribute to the development of rheumatoid arthritis (RA). Possible mechanisms involving environmental and individual factors in RA pathogenesis were analyzed, namely, infections, mental stress, sleep deprivation ecology, age, perinatal and gender factors, eating habits, obesity and smoking. The non-genetic factors modulate basic processes in the body with the impact of these factors being non-specific, but these common challenges may be decisive for advancement of the disease in the predisposed body at risk for RA. The provocation of this particular disease is associated with the presence of congenital loci minoris resistentia. The more frequent non-genetic factors form tangles of interdependent relationships and, thereby, several interdependent external factors hit one vulnerable basic process at once, either provoking or reinforcing each other. Understanding the specific mechanisms by which environmental and individual factors impact an individual under RA risk in the preclinical stages can contribute to early disease diagnosis and, if the factor is modifiable, might be useful for the prevention or delay of its development.

Association of the Maternal Gut Microbiota/Metabolome with Cord Blood CCL17

Chemokine (C-C motif) ligand 17 (CCL17) is a pro-allergic factor: high CCL17 levels in cord blood (CB) precede later allergic predisposition. Short-chain fatty acid (SCFA) treatment during pregnancy has been shown to protect mouse pups against allergic diseases. The maternal microbial metabolome during pregnancy may affect fetal allergic immune responses. We therefore examined the associations between CB CCL17 and gut SCFA levels in healthy pregnant Japanese women. CB CCL17 serum levels at birth, and maternal non-specific IgE levels in maternal sera at 32 weeks of gestation were measured. Maternal stool samples were collected at 12 (n = 59) and 32 (n = 58) weeks of gestation for gut microbiota analysis, based on barcoded 16S rRNA sequencing and metabolite levels. The CB CCL17 levels correlated negatively with butyrate concentrations and positively with isobutyrate at 12 weeks; CB CCL17 correlated positively with valerate and lactate at 32 weeks. Similarly, butyrate levels correlated negatively with maternal non-specific IgE levels, whereas the lactate concentration correlated positively with IgE levels. At 32 weeks, the Shannon diversity index (SDI) of Firmicutes and Proteobacteria correlated negatively with CB CCL17 levels, while those of the total microbiota correlated positively with the CB CCL17 levels. These metabolites may alter fetal immune responses. This study provides the first link between maternal metabolites during pregnancy and the risk of allergic diseases in human offspring.

An empirical test of the biodiversity hypothesis: Exposure to plant diversity is associated with a reduced risk of childhood acute lymphoblastic leukemia

The biodiversity hypothesis posits that declining biodiversity may be responsible, at least in part, for the global increase in immune diseases. However, few studies have been able to demonstrate a link between exposure to biodiversity and specific health outcomes. We test whether exposure to plant diversity protects against childhood acute lymphoblastic leukemia (ALL) by promoting immune maturation. Our sample consisted of all children born in New Zealand from 1998 to 2013 (n = 899,126; 264 ALL cases), which we followed from birth to age five. We calculated plant-diversity metrics using the Global Biodiversity Information Facility, which contains over two million geocoded plant records in New Zealand. Consistent with previous research, children who had always lived in an urban area, or who had an older mother, were at greater risk for ALL, whereas children with older siblings were at lower risk. In addition, we found that plant-diversity metrics based on the maximum number of plant genera a child was exposed to during the first two years of life were protective of ALL. Specifically, exposure to the highest tertile of plant diversity was associated with a reduction in ALL risk of 35% (95% CI: 11%-53%). Exposure to plant diversity, and associated microbial communities, may be a viable public-health intervention to reduce the risk of ALL and possibly other immune diseases.

Changes in peripheral immune populations during pregnancy and modulation by probiotics and ω-3 fatty acids

Allergic diseases have become a major health problem, partly due to reduced microbial stimulation and a decreased dietary ω-3/ω-6 long-chain polyunsaturated fatty acid ratio. Prenatal exposures have been reported to influence allergy development, possibly induced via changes in maternal immune regulation. In a randomized double-blind placebo-controlled multicenter allergy prevention trial (PROOM-3), pregnant women were recruited at gestational week 20, and randomized to four study groups, one receiving both L. reuteri oil drops and ω-3 PUFA capsules (n = 22), the second receiving ω-3 PUFA supplementation and placebo regarding L. reuteri (n = 21), the third receiving L. reuteri and placebo regarding ω-3 PUFA (n = 22) and the fourth group receiving placebo capsules and placebo oil drops (n = 23). In this substudy, supplemental and pregnancy-related effects on maternal peripheral immune cell populations during pregnancy were assessed by flow cytometry immune phenotyping at gestational week 20, 32 and 4 days after delivery. The numbers of activated and regulatory T (Treg) cells (CD45RA⁻ Foxp3⁺⁺/CD45RA⁺Foxp3⁺) were reduced after delivery, with the lowest count in the L. reuteri supplemented group compared with the placebo group 4 days after delivery, while the ω-3 PUFA group did not differ from the placebo group. Several treatment-independent changes were observed during and after pregnancy in lymphocytes (CD4⁺/8⁺/19⁺/56⁺/45RA^+/−), CD14⁺16^+/− monocytes, and in subpopulations of T helper cells (Th) CD4⁺CD45RA⁻Tbet⁺ (Th1) and CD4⁺CD45RA⁻RORC⁺ (Th17) cells. In conclusion, probiotic supplementation to the mother during the second half of pregnancy resulted in immunomodulatory effects among activated and resting Treg cells. Furthermore, several systemic immune modifying effects of pregnancy were observed.

Altered Gut Microbiome and Environmental Factors Associated with Development of Eczema in Hong Kong Infants: A 4-Month Pilot Study

Eczema is a multifactorial skin disease that affects 20% of children worldwide and has a complex relationship with microbial, nutritional, parental and environmental factors. In this study, we investigated the potential association of eczema with the gut microbiome and environmental factors. One hundred and fifty-two newborn subjects and their mothers were recruited within 10 days postnatally at the Prince of Wales Hospital in Hong Kong, China and asked to complete questionnaires on allergies, maternal diet and environmental assessment at enrolment. Then, the participants were classified as with or without eczema at four months after birth based on the Comprehensive Early Childhood Allergy Questionnaire (CECAQ) and SCORing Atopic Dermatitis (SCORAD) index (n = 48, with 24 in each group). Stool samples were collected from both groups at the same time. Microbial DNA was extracted from each stool sample, and 16S rRNA sequencing was performed to analyze the gut microbiome profiles of the subjects. Our results indicated that the abundance of Bifidobacterium was significantly higher in the eczema group than in the control group (p = 0.04). A multivariable logistic regression analysis was conducted, and the results showed that the father’s education level and maternal intake of cereal products and nutritional supplements during pregnancy were associated with the development of eczema (p = 0.008, 0.032 and 0.015, respectively). In conclusion, this study provided preliminary information about the potential risk factors of eczema development in Hong Kong infants in support of a future full study.

Levels of Growth Factors and IgA in the Colostrum of Women from Burundi and Italy

Colostrum is produced in the first days postpartum. It is a known source of immune mediators for a newborn within the first week of life. Although it is still unclear if colostrum composition varies between populations, recent data suggest differences. Hepatocyte growth factor (HGF); transforming growth factor-β (TGF-β) 1, 2, and 3; and immunoglobulin A (IgA) are key immunological components of colostrum that stimulate neonatal gastrointestinal and immune system development. We aimed to investigate the differences in the concentration between immune markers in the colostrum of mothers living in Burundi and Italy, and to identify the factors associated with differences. In this cross-sectional birth cohort study, a total of 99 colostrum samples from Burundian (n = 23) and Italian (n = 76) women were collected at 0 to 6 days postpartum. A clinical chemistry analyser was used for IgA quantification and electro-chemiluminescence, for HGF and TGFβ1-3 assessment. A univariate analysis and multivariate linear regression model were used for statistical testing. The concentrations of TGF-β2 (p = 0.01) and IgA (p < 0.01) were significantly higher in the colostrum from the women residing in Burundi than in Italy, both in a univariate analysis and upon the adjustment for confounding factors. A similar trend is seen for HGF, reaching statistical significance upon a multivariate analysis. We found a moderate to strong positive correlation between the TGF-β isoforms and IgA concentration in both countries (p < 0.01), with stronger concentration in the colostrum from Burundi. The results of this study are in support of previous data, suggesting that concentration of the immune active molecules is higher in the human milk of women residing in developing countries. However, with a small sample size, caution must be applied, as the findings require further confirmation. Future work should also be focused on other factors (e.g., lipid and microbial composition), as well as the investigation into colostrum and between populations comparison, adjusting for potential confounders.

Pre- and probiotics for allergy prevention: time to revisit recommendations?

Reduced intensity and diversity of microbial exposure is considered a major factor driving abnormal postnatal immune maturation and increasing allergy prevalence, particularly in more affluent regions. Quantitatively, the largest important source of early immune-microbial interaction, the gut microbiota, is of particular interest in this context, with variations in composition and diversity in the first months of life associated with subsequent allergy development. Attempting to restore the health consequences of the 'dysbiotic drift' in modern society, interventions modulating gut microbiota for allergy prevention have been evaluated in several randomized placebo-controlled trials. In this review, we provide an overview of these trials and discuss recommendations from international expert bodies regarding prebiotic, probiotic and synbiotic interventions. Recent guidelines from the World Allergy Organization recommend the use of probiotics for the primary prevention of eczema in pregnant and breastfeeding mothers of infants at high risk for developing allergy and in high-risk infants. It is however stressed that these recommendations are conditional, based on very low-quality evidence and great heterogeneity between studies, which also impedes specific and practical advice to consumers on the most effective regimens. We discuss how the choice of probiotic strains, timing and duration of administration can critically influence the outcome due to different effects on immune modulation and gut microbiota composition. Furthermore, we propose strategies to potentially improve allergy-preventive effects and enable future evidence-based implementation.

The mother-offspring dyad: microbial transmission, immune interactions and allergy development

The increasing prevalence of allergy in affluent countries may be caused by reduced intensity and diversity of microbial stimulation, resulting in abnormal postnatal immune maturation. Most studies investigating the underlying immunomodulatory mechanisms have focused on postnatal microbial exposure, for example demonstrating that the gut microbiota differs in composition and diversity during the first months of life in children who later do or do not develop allergic disease. However, it is also becoming increasingly evident that the maternal microbial environment during pregnancy is important in childhood immune programming, and the first microbial encounters may occur already in utero. During pregnancy, there is a close immunological interaction between the mother and her offspring, which provides important opportunities for the maternal microbial environment to influence the immune development of the child. In support of this theory, combined pre- and postnatal supplementations seem to be crucial for the preventive effect of probiotics on infant eczema. Here, the influence of microbial and immune interactions within the mother-offspring dyad on childhood allergy development will be discussed. In addition, how perinatal transmission of microbes and immunomodulatory factors from mother to offspring may shape appropriate immune maturation during infancy and beyond, potentially via epigenetic mechanisms, will be examined. Deeper understanding of these interactions between the maternal and offspring microbiome and immunity is needed to identify efficacious preventive measures to combat the allergy epidemic.

Bugging allergy; role of pre-, pro- and synbiotics in allergy prevention

Large-scale biodiversity loss and complex changes in social behaviors are altering human microbial ecology. This is increasingly implicated in the global rise in inflammatory diseases, most notably the "allergy epidemic" in very early life. Colonization of human ecological niches, particularly the gastrointestinal tract, is critical for normal local and systemic immune development and regulation. Disturbances in composition, diversity and timing of microbial colonization have been associated with increased allergy risk, indicating the importance of strategies to restore a dysbiotic gut microbiota in the primary prevention of allergic diseases, including the administration of probiotics, prebiotics and synbiotics. Here, we summarize and discuss findings of randomized clinical trials that have examined the effects of these microbiome-related strategies on short and long-term allergy preventative effects - including new guidelines from the World Allergy Organization which now recommend probiotics and prebiotics for allergy prevention under certain conditions. The relatively low quality evidence, limited comparative studies and large heterogeneity between studies, have collectively hampered recommendations on specific probiotic strains, specific timing and specific conditions for the most effective preventive management. At the same time the risk of using available products is low. While further research is needed before specific practice guidelines on supplement probiotics and prebiotics, it is equally important that the underlying dietary and lifestyle factors of dysbiosis are addressed at both the individual and societal levels.

Aberrant IgA responses to the gut microbiota during infancy precede asthma and allergy development

BACKGROUND

Although a reduced gut microbiota diversity and low mucosal total IgA levels in infancy have been associated with allergy development, IgA responses to the gut microbiota have not yet been studied.

OBJECTIVE

We sought to determine the proportions of IgA coating together with the characterization of the dominant bacteria, bound to IgA or not, in infant stool samples in relation to allergy development.

METHODS

A combination of flow cytometric cell sorting and deep sequencing of the 16S rDNA gene was used to characterize the bacterial recognition patterns by IgA in stool samples collected at 1 and 12 months of age from children staying healthy or having allergic symptoms up to 7 years of age.

RESULTS

The children with allergic manifestations, particularly asthma, during childhood had a lower proportion of IgA bound to fecal bacteria at 12 months of age compared with healthy children. These alterations cannot be attributed to differences in IgA levels or bacterial load between the 2 groups. Moreover, the bacterial targets of early IgA responses (including coating of the Bacteroides genus), as well as IgA recognition patterns, differed between healthy children and children with allergic manifestations. Altered IgA recognition patterns in children with allergy were observed already at 1 month of age, when the IgA antibodies are predominantly maternally derived in breast-fed children.

CONCLUSION

An aberrant IgA responsiveness to the gut microbiota during infancy precedes asthma and allergy development, possibly indicating an impaired mucosal barrier function in allergic children.

Developmental origins of inflammatory and immune diseases

Epidemiological and experimental animal studies show that suboptimal environments in fetal and neonatal life exert a profound influence on physiological function and risk of diseases in adult life. The concepts of the 'developmental programming' and Developmental Origins of Health and Diseases (DOHaD) have become well accepted and have been applied across almost all fields of medicine. Adverse intrauterine environments may have programming effects on the crucial functions of the immune system during critical periods of fetal development, which can permanently alter the immune function of offspring. Immune dysfunction may in turn lead offspring to be susceptible to inflammatory and immune diseases in adulthood. These facts suggest that inflammatory and immune disorders might have developmental origins. In recent years, inflammatory and immune disorders have become a growing health problem worldwide. However, there is no systematic report in the literature on the developmental origins of inflammatory and immune diseases and the potential mechanisms involved. Here, we review the impacts of adverse intrauterine environments on the immune function in offspring. This review shows the results from human and different animal species and highlights the underlying mechanisms, including damaged development of cells in the thymus, helper T cell 1/helper T cell 2 balance disturbance, abnormal epigenetic modification, effects of maternal glucocorticoid overexposure on fetal lymphocytes and effects of the fetal hypothalamic-pituitary-adrenal axis on the immune system. Although the phenomena have already been clearly implicated in epidemiologic and experimental studies, new studies investigating the mechanisms of these effects may provide new avenues for exploiting these pathways for disease prevention.

Current evidence on whether perinatal risk factors influence coeliac disease is circumstantial

Coeliac disease is triggered by an interplay of environmental and genetic factors and is one of the most prevalent autoimmune diseases in children, occurring in about 1% of Europeans. Over the last few decades, there has been a growing interest in the role of the perinatal environment in coeliac disease and this review discusses the growing body of literature on coeliac disease and perinatal risk factors.

CONCLUSION

There is still only circumstantial evidence that the perinatal environment influences coeliac disease development. Large-scale cohort studies and emerging scientific concepts, such as epigenetics, may help us establish the role of these environmental factors.

Probiotics for treatment and primary prevention of allergic diseases and asthma: looking back and moving forward

Microbial ecosystems cover the surface of the human body and it is becoming increasingly clear that our modern environment has profound effects on microbial composition and diversity. A dysbiotic gut microbiota has been associated with allergic diseases and asthma in cross-sectional and observational studies. In an attempt to restore this dysbiosis, probiotics have been evaluated in randomized controlled trials. Here, we review treatment and primary prevention studies, recent meta-analyses, and discuss the current understanding of the role of probiotics in this context. Many meta-analyses have shown a moderate benefit of probiotics for eczema prevention, whereas there is less evidence of a benefit for other allergic manifestations. Because of very low quality evidence and heterogeneity between studies, specific advice on the most effective regimens cannot yet be given - not even for eczema prevention. To be able to adopt results into specific recommendations, international expert organizations stress the need for well-designed studies.

The gut microbiota and its role in the development of allergic disease: a wider perspective

The gut microbiota are critical in the homoeostasis of multiple interconnected host metabolic and immune networks. If early microbial colonization is delayed, the gut-associated lymphoid tissues (GALT) fail to develop, leading to persistent immune dysregulation in mice. Microbial colonization has also been proposed as a major driver for the normal age-related maturation of both Th1 and T regulatory (Treg) pathways that appear important in suppressing early propensity for Th2 allergic responses. There is emerging evidence that resident symbionts induce tolerogenic gut-associated Treg cells and dendritic cells that ensure the preferential growth of symbionts; keeping pathogenic strains in check and constraining proinflammatory Th1, Th2, and Th17 clones. Some effects of symbionts are mediated by short-chain fatty acids, which play a critical role in mucosal integrity and local and systemic metabolic function and stimulate the regulatory immune responses. The homoeostatic IL-10/TGF-β dominated tolerogenic response within the GALT also signals the production of secretory IgA, which have a regulating role in mucosal integrity. Contrary to the 'sterile womb' paradigm, recent studies suggest that maternal microbial transfer to the offspring begins during pregnancy, providing a pioneer microbiome. It is likely that appropriate microbial stimulation both pre- and postnatally is required for optimal Th1 and Treg development to avoid the pathophysiological processes leading to allergy. Disturbed gut colonization patterns have been associated with allergic disease, but whether microbial variation is the cause or effect of these diseases is still under investigation. We are far from understanding what constitutes a 'healthy gut microbiome' that promotes tolerance. This remains a major limitation and might explain some of the inconsistency in human intervention studies with prebiotics and probiotics. Multidisciplinary integrative approaches with researchers working in networks, using harmonized outcomes and methodologies, are needed to advance our understanding in this field.

Relationship between in utero C-reactive protein levels and asthma in at-risk children

BACKGROUND

Asthma research has focused on postnatal exposures, but there is recent evidence to indicate atopic immune responses might be initiated in utero. Systemic inflammation during pregnancy might indicate an environment that could increase propensity in the child to develop allergic disease.

OBJECTIVE

To investigate the association of systemic inflammation, as measured by C-reactive protein (CRP) levels, with asthma and wheezing in offspring within an at-risk, mostly Mexican, cohort.

METHODS

Using data from a randomized education intervention of families at risk for asthma from 1998 followed through 2009 in urban Chicago, asthma was defined as ever having a physician diagnosis of asthma by 3 years of age and wheezing before the third year. Logistic regression models controlling for confounders investigated the effect of prenatal CRP levels on these outcomes.

RESULTS

There were 244 mother-child pairs included in the study analysis with median prenatal CRP levels of 4.9 mg/L (interquartile range 3.2-7.7). Continuous prenatal CRP levels were predictive of asthma by year 3 (relative risk 2.4, 95% confidence interval 1.3, 3.6) and wheezing in year 3 (relative risk 1.7, 95% confidence interval 1.1, 2.4) after adjustment. Associations remained significant in mothers who were of Mexican ethnicity and were nonsmokers, suggesting that effects might be stronger in children at lower risk of disease.

CONCLUSION

Prenatal CRP levels are associated with asthma by year 3 and wheezing in year 3 within a high-risk, urban, mostly Mexican, cohort. Maternal systemic inflammation might reflect a prenatal environment that could increase offspring susceptibility to develop wheezing and asthma young in life.

The composition of the gut microbiota throughout life, with an emphasis on early life

The intestinal microbiota has become a relevant aspect of human health. Microbial colonization runs in parallel with immune system maturation and plays a role in intestinal physiology and regulation. Increasing evidence on early microbial contact suggest that human intestinal microbiota is seeded before birth. Maternal microbiota forms the first microbial inoculum, and from birth, the microbial diversity increases and converges toward an adult-like microbiota by the end of the first 3-5 years of life. Perinatal factors such as mode of delivery, diet, genetics, and intestinal mucin glycosylation all contribute to influence microbial colonization. Once established, the composition of the gut microbiota is relatively stable throughout adult life, but can be altered as a result of bacterial infections, antibiotic treatment, lifestyle, surgical, and a long-term change in diet. Shifts in this complex microbial system have been reported to increase the risk of disease. Therefore, an adequate establishment of microbiota and its maintenance throughout life would reduce the risk of disease in early and late life. This review discusses recent studies on the early colonization and factors influencing this process which impact on health.

Pre- and postnatal administration of Lactobacillus reuteri decreases TLR2 responses in infants

Background

Mice models indicate that intact Toll like receptor (TLR) signaling may be essential for the allergy protective effects of diverse bacterial exposure observed in clinical trials and epidemiological studies. Probiotic supplementation with Lactobacillus reuteri from pregnancy week 36 and to the infant through the first year of life decreased the prevalence of IgE-associated eczema at two years (ClinicalTrials.gov NCT01285830). The effect of this supplementation on innate immune responses to bacterial products and the expression of associated TLRs were explored.

Methods

Blood mononuclear cells were collected at birth, 6, 12 and 24 months from 61 infants and cultured with TLR2, 4 and 9 ligands. Cytokine and chemokine secretion was determined as well as TLR2, 4 and 9 mRNA expression.

Results

Probiotic supplementation was associated with decreased LTA (lipoteichoic acid) induced CCL4, CXCL8, IL-1β and IL-6 responses at 12 months and decreased CCL4 and IL-1β secretion at 24 months. TLR2 mRNA expression was not affected by probiotic treatment.

Conclusions

Decreased responses to TLR2, the main receptor for LTA from Gram positive bacteria, in probiotic treated children seem to be dependent on factors downstream of TLR mRNA expression.

Th2-like chemokine levels are increased in allergic children and influenced by maternal immunity during pregnancy

BACKGROUND

The influence of the intra-uterine environment on the immunity and allergy development in the offspring is unclear. We aimed to investigate (i) whether the pregnancy magnifies the Th2 immunity in allergic and non-allergic women, (ii) whether the maternal chemokine levels during pregnancy influenced the offspring's chemokine levels during childhood and (iii) the relationship between circulating Th1/Th2-associated chemokines and allergy in mothers and children.

METHODS

The Th1-associated chemokines CXCL9, CXCL10, CXCL11, and the Th2-associated chemokines CCL17, CCL18 and CCL22 were quantified by Luminex and ELISA in 20 women with and 36 women without allergic symptoms at gestational week (gw) 10-12, 15-16, 25, 35, 39 and 2 and 12 months post-partum and in their children at birth, 6, 12, 24 months and 6 years of age. Total IgE levels were measured using ImmunoCAP Technology.

RESULTS

The levels of the Th2-like chemokines were not magnified by pregnancy. Instead decreased levels were shown during pregnancy (irrespectively of maternal allergy status) as compared to post-partum. In the whole group, the Th1-like chemokine levels were higher at gw 39 than during the first and second trimester and post-partum. Maternal CXCL11, CCL18 and CCL22 levels during and after pregnancy correlated with the corresponding chemokines in the offspring during childhood. Increased CCL22 and decreased CXCL10 levels in the children were associated with sensitisation and increased CCL17 levels with allergic symptoms during childhood. Maternal chemokine levels were not associated with maternal allergic disease.

CONCLUSIONS

Allergic symptoms and sensitisation were associated with decreased Th1- and increased Th2-associated chemokine levels during childhood, indicating a Th2 shift in the allergic children, possibly influenced by the maternal immunity during pregnancy.

Decreased gut microbiota diversity, delayed Bacteroidetes colonisation and reduced Th1 responses in infants delivered by caesarean section

OBJECTIVE

The early intestinal microbiota exerts important stimuli for immune development, and a reduced microbial exposure as well as caesarean section (CS) has been associated with the development of allergic disease. Here we address how microbiota development in infants is affected by mode of delivery, and relate differences in colonisation patterns to the maturation of a balanced Th1/Th2 immune response.

DESIGN

The postnatal intestinal colonisation pattern was investigated in 24 infants, born vaginally (15) or by CS (nine). The intestinal microbiota were characterised using pyrosequencing of 16S rRNA genes at 1 week and 1, 3, 6, 12 and 24 months after birth. Venous blood levels of Th1- and Th2-associated chemokines were measured at 6, 12 and 24 months.

RESULTS

Infants born through CS had lower total microbiota diversity during the first 2 years of life. CS delivered infants also had a lower abundance and diversity of the Bacteroidetes phylum and were less often colonised with the Bacteroidetes phylum. Infants born through CS had significantly lower levels of the Th1-associated chemokines CXCL10 and CXCL11 in blood.

CONCLUSIONS

CS was associated with a lower total microbial diversity, delayed colonisation of the Bacteroidetes phylum and reduced Th1 responses during the first 2 years of life.

Febrile and gynecological infections during pregnancy are associated with a greater risk of childhood eczema

BACKGROUND

Mounting evidence suggests that fetal exposures may exert long-term effects on the function of the skin and of the immune system. This study aimed at assessing whether maternal complications during pregnancy are associated with an increased risk of eczema during childhood.

METHODS

The associations between hypertension/preeclampsia, febrile infections, or gynecological infections during pregnancy and the occurrence of childhood eczema were studied in a population (n = 3907) of children, aged 3-14 yrs, living in Italy. Their parents filled in a standardized questionnaire about the presence of children's eczema and the events that occurred during pregnancy, birth, and the first year of the child's life.

RESULTS

7.7%, 3.8%, and 6.1% of the pregnancies were complicated by hypertension/preeclampsia, febrile infections, and gynecological infections, respectively. The prevalence of eczema was significantly higher in children born to mothers who had experienced febrile (35.5% vs. 22.0%; p < 0.001) or gynecological infections (35.3% vs. 21.6%; p < 0.001) compared with those born to mothers who had not suffered from that specific pregnancy complication, while hypertension/preeclampsia was not significantly associated with childhood eczema. After adjusting for potential confounders, the risk of eczema was significantly higher in children born to mothers who reported febrile infections during the 1st trimester (OR: 2.32; 95% CI: 1.11-4.82) and gynecological infections during the 3rd trimester of pregnancy (OR: 2.73; 95% CI:1.73-4.31).

CONCLUSIONS

Fetal exposure to febrile and gynecological infections might enhance the risk of eczema in the offspring, especially when occurring in specific trimesters of pregnancy. These findings suggest that febrile and gynecological infections might interfere with fetal and perinatal programming of the immune function and skin through different mechanisms.

No effect of probiotics on respiratory allergies: a seven-year follow-up of a randomized controlled trial in infancy

BACKGROUND

Supplementation with the probiotic Lactobacillus reuteri reduced the incidence of IgE-associated allergic disease in infancy. This treatment might therefore also reduce the risk of asthma and allergic rhinoconjunctivitis in school age.

OBJECTIVE

To evaluate whether perinatal and infant supplementation with L. reuteri reduced the prevalence of respiratory allergic disease in school age and to explore whether this supplementation was associated with any long-term side effects.

METHODS

A randomized, placebo-controlled trial with oral supplementation with L. reuteri ATCC 55730 (1 × 10(8) CFU) during the last month of gestation and through the first year of life comprising 232 families with allergic disease, of whom 184 completed a 7-yr follow-up. The primary outcomes at 7 yr of age were allergic disease and skin prick test reactivity (ClinicalTrials.gov ID NCT01285830).

RESULTS

The prevalence of asthma (15% in the probiotic vs. 16% in placebo group), allergic rhinoconjunctivitis (27% vs. 20%), eczema (21% vs. 19%) and skin prick test reactivity (29% vs. 26%) was similar in the probiotic and placebo group. Growth indices and gastrointestinal symptoms were similar in the two groups. No severe adverse events were reported.

CONCLUSION

The effect of L. reuteri on sensitization and IgE-associated eczema in infancy did not lead to a lower prevalence of respiratory allergic disease in school age. Thus, the effect of L. reuteri on the immune system seems to be transient. Administration of L. reuteri during the last weeks of gestation and in infancy was not associated with any long-term side effects.

Fetal growth and risk of childhood asthma and allergic disease

Introduction

Early genetic and environmental factors have been discussed as potential causes for the high prevalence of asthma and allergic disease in the western world, and knowledge on fetal growth and its consequence on future health and disease development is emerging.

Objective

This review article is an attempt to summarize research on fetal growth and risk of asthma and allergic disease. Current knowledge and novel findings will be reviewed and open research questions identified, to give basic scientists, immunologists and clinicians an overview of an emerging research field.

Methods

PubMed-search on pre-defined terms and cross-references.

Results

Several studies have shown a correlation between low birth weight and/or gestational age and asthma and high birth weight and/or gestational age and atopy. The exact mechanism is not yet clear but both environmental and genetic factors seem to contribute to fetal growth. Some of these factors are confounders that can be adjusted for, and twin studies have been very helpful in this context. Suggested mechanisms behind fetal growth are often linked to the feto-maternal circulation, including the development of placenta and umbilical cord. However, the causal link between fetal growth restriction and subsequent asthma and allergic disease remains unexplained. New research regarding the catch-up growth following growth restriction has posited an alternative theory that diseases later on in life result from rapid catch-up growth rather than intrauterine growth restriction per se. Several studies have found a correlation between a rapid weight gain after birth and development of asthma or wheezing in childhood.

Conclusion and clinical relevance

Asthma and allergic disease are multifactorial. Several mechanisms seem to influence their development. Additional studies are needed before we fully understand the causal links between fetal growth and development of asthma and allergic diseases.

Influence and mechanisms of maternal and infant diets on the development of childhood asthma

Perinatal nutrition has been implicated in the programming of diseases in children and adults. The prevalence of asthma has dramatically increased in the past few decades, particularly in children. This suggests that the perinatal environment, including maternal and infant diets, may be involved in the increase in the prevalence of asthma. Recent studies have demonstrated that certain maternal and infant diets have a protective or augmentative effect on the development of asthma. Maternal diets with higher vitamin D, vitamin E, or/and probiotics are related to asthma prevention. Infants with breast feeding for at least 4 months and/or complementary diets between 4 and 6 months may have regulatory effects on the prevention of asthma. In summary, diets may have epigenetic or immune regulatory effects on the promotion or prevention of asthma. This article analyzes recent reports on the potential mechanism and mechanism-driven early prevention of childhood asthma by modification of maternal and infant diets.