Association between levels of Toll-like receptors 2 and 4 and CD14 mRNA and allergy in pregnant women and their offspring

From preschool wheezing to asthma: Immunological determinants

Asthma represents a chronic respiratory disease affecting millions of children worldwide. The transition from preschool wheezing to school-age asthma involves a multifaceted interplay of various factors, including immunological aspects in early childhood. These factors include complex cellular interactions among different immune cell subsets, induction of pro-inflammatory mediators and the molecular impact of environmental factors like allergens or viral infections on the developing immune system. Furthermore, the activation of specific genes and signalling pathways during this early phase plays a pivotal role in the manifestation of symptoms and subsequent development of asthma. Early identification of the propensity or risk for asthma development, for example by allergen sensitisation and viral infections during this critical period, is crucial for understanding the transition from wheeze to asthma. Favourable immune regulation during a critical 'window of opportunity' in early childhood can induce persistent changes in immune cell behaviour. In this context, trained immunity, including memory function of innate immune cells, has significant implications for understanding immune responses, potentially shaping long-term immunological outcomes based on early-life environmental exposures. Exploration of these underlying immune mechanisms that drive disease progression will provide valuable insights to understand childhood asthma development. This will be instrumental to develop preventive strategies at different stages of disease development for (i) inhibiting progression from wheeze to asthma or (ii) reducing disease severity and (iii) uncovering novel therapeutic strategies and contributing to more tailored and effective treatments for childhood asthma. In the long term, this shall empower healthcare professionals to develop evidence-based interventions that reduce the burden of asthma for children, families and society overall.

Microecology research: a new target for the prevention of asthma

The incidence and prevalence of asthma have increased remarkably in recent years. There are lots of factors contributing to the occurrence and development of asthma. With the improvement of sequencing technology, it has been found that the microbiome plays an important role in the formation of asthma in early life. The roles of the microbial environment and human microbiome in the occurrence and development of asthma have attracted more and more attention. The environmental microbiome influences the occurrence of asthma by shaping the human microbiome. The specific mechanism may be related to the immune regulation of Toll-like receptors and T cells (special Tregs). Intestinal microbiome is formed and changed by regulating diet and lifestyle in early life, which may affect the development and maturation of the pulmonary immune system through the intestinal-pulmonary axis. It is well-recognized that both environmental microbiomes and human microbiomes can influence the onset of asthma. This review aims to summarize the recent advances in the research of microbiome, its relationship with asthma, and the possible mechanism of the microbiome in the occurrence and development of asthma. The research of the microbial environment and human microbiome may provide a new target for the prevention of asthma in children who have high-risk factors to allergy. However, further study of “when and how” to regulate microbiome is still needed.

Omega-3 fatty acid addition during pregnancy

BACKGROUND

Higher intakes of foods containing omega-3 long-chain polyunsaturated fatty acids (LCPUFA), such as fish, during pregnancy have been associated with longer gestations and improved perinatal outcomes. This is an update of a review that was first published in 2006.

OBJECTIVES

To assess the effects of omega-3 LCPUFA, as supplements or as dietary additions, during pregnancy on maternal, perinatal, and neonatal outcomes and longer-term outcomes for mother and child.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (16 August 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing omega-3 fatty acids (as supplements or as foods, stand-alone interventions, or with a co-intervention) during pregnancy with placebo or no omega-3, and studies or study arms directly comparing omega-3 LCPUFA doses or types. Trials published in abstract form were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data, assessed risk of bias in trials and assessed quality of evidence for prespecified birth/infant, maternal, child/adult and health service outcomes using the GRADE approach.

MAIN RESULTS

In this update, we included 70 RCTs (involving 19,927 women at low, mixed or high risk of poor pregnancy outcomes) which compared omega-3 LCPUFA interventions (supplements and food) compared with placebo or no omega-3. Overall study-level risk of bias was mixed, with selection and performance bias mostly at low risk, but there was high risk of attrition bias in some trials. Most trials were conducted in upper-middle or high-income countries; and nearly half the trials included women at increased/high risk for factors which might increase the risk of adverse maternal and birth outcomes.Preterm birth < 37 weeks (13.4% versus 11.9%; risk ratio (RR) 0.89, 95% confidence interval (CI) 0.81 to 0.97; 26 RCTs, 10,304 participants; high-quality evidence) and early preterm birth < 34 weeks (4.6% versus 2.7%; RR 0.58, 95% CI 0.44 to 0.77; 9 RCTs, 5204 participants; high-quality evidence) were both lower in women who received omega-3 LCPUFA compared with no omega-3. Prolonged gestation > 42 weeks was probably increased from 1.6% to 2.6% in women who received omega-3 LCPUFA compared with no omega-3 (RR 1.61 95% CI 1.11 to 2.33; 5141 participants; 6 RCTs; moderate-quality evidence).For infants, there was a possibly reduced risk of perinatal death (RR 0.75, 95% CI 0.54 to 1.03; 10 RCTs, 7416 participants; moderate-quality evidence: 62/3715 versus 83/3701 infants) and possibly fewer neonatal care admissions (RR 0.92, 95% CI 0.83 to 1.03; 9 RCTs, 6920 participants; moderate-quality evidence - 483/3475 infants versus 519/3445 infants). There was a reduced risk of low birthweight (LBW) babies (15.6% versus 14%; RR 0.90, 95% CI 0.82 to 0.99; 15 trials, 8449 participants; high-quality evidence); but a possible small increase in large-for-gestational age (LGA) babies (RR 1.15, 95% CI 0.97 to 1.36; 6 RCTs, 3722 participants; moderate-quality evidence, for omega-3 LCPUFA compared with no omega-3. Little or no difference in small-for-gestational age or intrauterine growth restriction (RR 1.01, 95% CI 0.90 to 1.13; 8 RCTs, 6907 participants; moderate-quality evidence) was seen.For the maternal outcomes, there is insufficient evidence to determine the effects of omega-3 on induction post-term (average RR 0.82, 95% CI 0.22 to 2.98; 3 trials, 2900 participants; low-quality evidence), maternal serious adverse events (RR 1.04, 95% CI 0.40 to 2.72; 2 trials, 2690 participants; low-quality evidence), maternal admission to intensive care (RR 0.56, 95% CI 0.12 to 2.63; 2 trials, 2458 participants; low-quality evidence), or postnatal depression (average RR 0.99, 95% CI 0.56 to 1.77; 2 trials, 2431 participants; low-quality evidence). Mean gestational length was greater in women who received omega-3 LCPUFA (mean difference (MD) 1.67 days, 95% CI 0.95 to 2.39; 41 trials, 12,517 participants; moderate-quality evidence), and pre-eclampsia may possibly be reduced with omega-3 LCPUFA (RR 0.84, 95% CI 0.69 to 1.01; 20 trials, 8306 participants; low-quality evidence).For the child/adult outcomes, very few differences between antenatal omega-3 LCPUFA supplementation and no omega-3 were observed in cognition, IQ, vision, other neurodevelopment and growth outcomes, language and behaviour (mostly low-quality to very low-quality evidence). The effect of omega-3 LCPUFA on body mass index at 19 years (MD 0, 95% CI -0.83 to 0.83; 1 trial, 243 participants; very low-quality evidence) was uncertain. No data were reported for development of diabetes in the children of study participants.

AUTHORS' CONCLUSIONS

In the overall analysis, preterm birth < 37 weeks and early preterm birth < 34 weeks were reduced in women receiving omega-3 LCPUFA compared with no omega-3. There was a possibly reduced risk of perinatal death and of neonatal care admission, a reduced risk of LBW babies; and possibly a small increased risk of LGA babies with omega-3 LCPUFA.For our GRADE quality assessments, we assessed most of the important perinatal outcomes as high-quality (e.g. preterm birth) or moderate-quality evidence (e.g. perinatal death). For the other outcome domains (maternal, child/adult and health service outcomes) GRADE ratings ranged from moderate to very low, with over half rated as low. Reasons for downgrading across the domain were mostly due to design limitations and imprecision.Omega-3 LCPUFA supplementation during pregnancy is an effective strategy for reducing the incidence of preterm birth, although it probably increases the incidence of post-term pregnancies. More studies comparing omega-3 LCPUFA and placebo (to establish causality in relation to preterm birth) are not needed at this stage. A further 23 ongoing trials are still to report on over 5000 women, so no more RCTs are needed that compare omega-3 LCPUFA against placebo or no intervention. However, further follow-up of completed trials is needed to assess longer-term outcomes for mother and child, to improve understanding of metabolic, growth and neurodevelopment pathways in particular, and to establish if, and how, outcomes vary by different types of omega-3 LCPUFA, timing and doses; or by characteristics of women.

Examining the association between maternal atopy and birth outcomes using a retrospective cohort in the southeastern region of the USA

OBJECTIVE

To assess birth outcomes in primiparous women with diagnosis of non-asthmatic atopy (NAA). Researchers hypothesised that women with NAA would have reduced the risk of adverse birth outcomes compared with women without NAA. NAA is defined as having allergic rhinitis and/or atopic dermatitis.

SETTING

Women were mostly treated in primary care settings in South Carolina, USA.

PARTICIPANTS

This is a retrospective cohort study in which participants were identified using a Medicaid database. Participants were primiparous women aged 19 to 25. Births occurring between 2004 and 2014 were identified using the South Carolina's Vital Statistics (VS) records of live births. Incomplete records (ie, information on plural birth, gestational age at birth or birth weight missing), plural births or infants born before completing 24 weeks of gestation were excluded. This provided 65 650 complete maternal-infant dyads, representing 97.6% of the maternal records and 96.9% of the VS records. Women previously diagnosed with NAA were frequency matched 1:4 to non-atopic controls for a total of 9965 maternal-infant dyads used in the statistical analysis.

PRIMARY OUTCOME MEASURES

Low birth weight, small for gestational age and preterm birth.

RESULTS

Linear tests for trend were statistically significant (p<0.001), indicating that NAA was associated with improved birth weight and gestational age at birth. After controlling for potential confounders, mothers with NAA had equal risk for each outcome when compared with mothers with no diagnosis of NAA.

CONCLUSION

A diagnosis of NAA among women living in the southeastern region of the USA does not reduce the risk of adverse birth outcomes nor does it elevate the risk of same. Additional studies with more rigorous designs are warranted to confirm the findings in this study.

Maternal prenatal and/or postnatal n-3 long chain polyunsaturated fatty acids (LCPUFA) supplementation for preventing allergies in early childhood

BACKGROUND

Allergies have become more prevalent globally over the last 20 years. Dietary consumption of n-3 (or omega 3) long chain polyunsaturated fatty acids (LCPUFA) has declined over the same period of time. This, together with the known role of n-3 LCPUFA in inhibiting inflammation, has resulted in speculation that n-3 LCPUFA may prevent allergy development. Dietary n-3 fatty acids supplements may change the developing immune system of the newborn before allergic responses are established, particularly for those with a genetic predisposition to the production of the immunoglobulin E (IgE) antibody. Individuals with IgE-mediated allergies have both the signs and symptoms of the allergic disease and a positive skin prick test (SPT) to the allergen.

OBJECTIVES

To assess the effect of n-3 LCPUFA supplementation in pregnant and/or breastfeeding women on allergy outcomes (food allergy, atopic dermatitis (eczema), allergic rhinitis (hay fever) and asthma/wheeze) in their children.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 August 2014), PubMed (1966 to 01 August 2014), CINAHL via EBSCOhost (1984 to 01 August 2014), Scopus (1995 to 01 August 2014), Web of Knowledge (1864 to 01 August 2014) and ClinicalTrials.gov (01 August 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) evaluating the effect of n-3 LCPUFA supplementation of pregnant and/or lactating women (compared with placebo or no treatment) on allergy outcomes of the infants or children. Trials using a cross-over design and trials examining biochemical outcomes only were not eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility and trial quality and performed data extraction. Where the review authors were also investigators on trials selected, an independent reviewer assessed trial quality and performed data extraction.

MAIN RESULTS

Eight trials involving 3366 women and their 3175 children were included in the review. In these trials, women were supplemented with n-3 LCPUFA during pregnancy (five trials), lactation (two trials) or both pregnancy and lactation (one trial). All trials randomly allocated women to either a n-3 LCPUFA supplement or a control group. The risk of bias varied across the eight included trials in this review with only two trials with a low risk of selection, performance and attrition bias.N-3 LCPUFA supplementation showed a clear reduction in the primary outcome of any allergy (medically diagnosed IgE mediated) in children aged 12 to 36 months (risk ratio (RR) 0.66, 95% confidence interval (CI) 0.44 to 0.98; two RCTs; 823 children), but not beyond 36 months (RR 0.86, 95% CI 0.61 to 1.20; one RCT, 706 children). For any allergy (medically diagnosed IgE mediated and/or parental report), no clear differences were seen in children either at 12 to 36 months (RR 0.89, 95% CI 0.71 to 1.11; two RCTs, 823 children) or beyond 36 months of age (RR 0.96, 95% CI 0.84 to 1.09; three RCTs, 1765 children).For the secondary outcomes of specific allergies there were no clear differences for food allergies at 12 to 36 months and beyond 36 months, but a clear reduction was seen for children in their first 12 months with n-3 LCPUFA (both for medically diagnosed IgE mediated and medically diagnosed IgE mediated and/or parental report). There was a clear reduction in medically diagnosed IgE-mediated eczema with n-3 LCPUFA for children 12 to 36 months of age, but not at any other time point for both medically diagnosed IgE mediated and medically diagnosed IgE mediated and/or parental report. No clear differences for allergic rhinitis or asthma/wheeze were seen at any time point for both medically diagnosed IgE mediated, and medically diagnosed IgE mediated and/or parental report.There was a clear reduction in children's sensitisation to egg and sensitisation to any allergen between 12 to 36 months of age when mothers were supplemented with n-3 LCPUFA.In terms of safety for the mother and child, n-3 LCPUFA supplementation during pregnancy did not show increased risk of postpartum haemorrhage or early childhood infections.

AUTHORS' CONCLUSIONS

Overall, there is limited evidence to support maternal n-3 LCPUFA supplementation during pregnancy and/or lactation for reducing allergic disease in children. Few differences in childhood allergic disease were seen between women who were supplemented with n-3 LCPUFA and those who were not.

Toll-like receptor 2 agonist Pam3CSK4 up-regulates FcεRI receptor expression on monocytes from patients with severe extrinsic atopic dermatitis

BACKGROUND

Both microbial antigens and allergens are important factors that can trigger atopic dermatitis (AD). Monocytes from patients with AD have been found to express increased and sustained levels of high-affinity IgE receptor (FcεRI) and Toll-like receptor 2 (TLR2). We hypothesized that putative interactions exist between TLR2 and FcεRI on monocytes in the pathogenesis of AD.

OBJECTIVE

This study aimed to understand whether activation of TLR2 by Pam3CSK4 would influence the expression of FcεRI, and whether mitogen-activated protein kinase (MAPK) signalling pathways were involved in such regulation.

METHODS

Peripheral blood monocytes from patients with severe extrinsic AD or healthy control patients were treated with the TLR2 agonist Pam3CSK4. The expression of FcεRI, intracellular TNF-α and MAPK family members were analysed by real-time quantitative PCR, flow cytometry and western blotting.

RESULTS

Monocytes from patients with severe extrinsic AD expressed higher levels of surface FcεRIα than were found in monocytes from healthy controls. Stimulation of human monocytes from patients with Pam3CSK4, but not lipopolysaccharide (LPS), resulted in the up-regulation of surface FcεRI expression by inducing p38 phosphorylation. Pretreatment with a specific inhibitor of p38 kinase inhibited the Pam3CSK4-induced up-regulation of FcεRIα, suggesting the involvement of the p38 pathway in the regulation of this process.

CONCLUSION

Our findings indicated interactions between TLR2 and FcεRI occurred via the activation of p38 in patients with severe extrinsic AD, which might indicate insights into understanding the mechanisms of how bacterial infection can exacerbate the clinical features of AD.

Allergy Takes Its Toll: The Role of Toll-like Receptors in Allergy Pathogenesis

Reduced early microbial exposure in early life has become a leading candidate to explain the escalating rate of allergic disease and has generated intense interest in the interaction between the developing immune system and the microbial environment. Infants depend on "signal" from the microbial environment to mature both T-helper cell type 1 and regulatory immune function. These signals, mediated through microbial pattern-recognition receptors, namely toll-like receptors (TLRs), seem essential to achieving the immunologic balance required for (1) pathogen protection and (2) normal immune tolerance. Despite this, the normal development of TLR function has never been documented. There is preliminary evidence that TLR function is under the influence of both genetic factors (genetic polymorphisms) and early environmental exposures including microbial exposure and breast feeding, and maternal smoking. This review explores the evidence that allergy is associated with developmental variations in TLR-mediated immune function and how this may be relevant for disease prevention.

Neonatal cytokine profile in the airway mucosal lining fluid is skewed by maternal atopy

RATIONALE

Heredity from mother or father may impact differently in complex diseases, such as atopy. Maternal atopy is a stronger risk factor than paternal atopy for the development of atopy in the offspring. We hypothesized that mother's and father's atopy would have a differential imprinting on the cytokines and chemokines in the upper airway mucosal lining fluid of healthy neonates.

OBJECTIVES

To study parental atopic imprinting on the cytokines and chemokines in the upper airway mucosal lining fluid of healthy neonates.

METHODS

Eighteen cytokines and chemokines were quantified in nasal mucosal lining fluid in 309 neonates from the novel unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC) birth cohort.

MEASUREMENTS AND MAIN RESULTS

Maternal, but not paternal, atopic status (asthma, hay fever, or eczema with or without sensitization) was associated with general down-regulation of all 18 mediators assessed by principal component analysis (overall P = 0.015).

CONCLUSIONS

Maternal atopy, but not paternal atopy, showed a strong linkage with a suppressed mucosal cytokine and chemokine signature in asymptomatic neonates, suggesting imprinting by the maternal milieu in utero or perinatal life.

Prenatal animal contact and gene expression of innate immunity receptors at birth are associated with atopic dermatitis

BACKGROUND

Cross-sectional studies have suggested that prenatal farm exposures might protect against allergic disease and increase the expression of receptors of the innate immune system. However, epidemiologic evidence supporting the association with atopic dermatitis remains inconsistent.

OBJECTIVE

To study the association between prenatal farm-related exposures and atopic dermatitis in a prospective study. We further analyzed the association between the expression of innate immune genes at birth and atopic dermatitis.

METHODS

A total of 1063 children who participated in a birth cohort study, Protection against Allergy-Study in Rural Environments, were included in this study. Doctor diagnosis of atopic dermatitis was reported by the parents from 1 to 2 years of age by questionnaire. Gene expression of Toll-like receptors (TLRs) and CD14 was assessed in cord blood leukocytes by quantitative PCR.

RESULTS

Maternal contact with farm animals and cats during pregnancy had a significantly protective effect on atopic dermatitis in the first 2 years of life. The risk of atopic dermatitis was reduced by more than half among children with mothers having contact with 3 or more farm animal species during pregnancy compared with children with mothers without contact (adjusted odds ratio, 0.43; 95% CI, 0.19-0.97). Elevated expression of TLR5 and TLR9 in cord blood was associated with decreased doctor diagnosis of atopic dermatitis. A significant interaction between polymorphism in TLR2 and prenatal cat exposure was observed in atopic dermatitis.

CONCLUSION

Maternal contact with farm animals and cats during pregnancy has a protective effect on the development of atopic dermatitis in early life, which is associated with a lower expression of innate immune receptors at birth.

Lifestyle and parental allergen sensitization are reflected in the intrauterine environment at gene expression level

BACKGROUND

Environmental factors, including the intrauterine environment, can influence the risk of allergy development. In the present study, we investigated whether lifestyle and parental allergen sensitization status are reflected at gene expression level in the intrauterine environment.

METHODS

  mRNA expression of 17 genes was determined by means of quantitative real-time PCR in term placenta of 36 families participating in the ALADDIN study (Assessment of Lifestyle and Allergic Disease During Infancy). Data were analysed using a linear regression model to estimate the influence of lifestyle and parental allergen sensitization on the relative mRNA expression levels. Immunohistochemistry on placenta biopsies was used to verify protein expression.

RESULTS

Significant differences in mRNA expression levels were detected at the foetal side of the placenta, where CD14 was expressed at higher levels in placentas from families living on a farm compared to not living on a farm, and IL-12(p40) was expressed at lower levels when the father was sensitized compared to nonsensitized. At the maternal side of the placenta, higher expression of STAT4 and lower expression of GATA3 were detected in families with sensitized compared to nonsensitized mothers, and IL-12(p40) was lower expressed when the families were living on a farm compared to not living on a farm. Immunohistochemistry performed for STAT4 and GATA3 showed that protein and mRNA levels correlated well.

CONCLUSION

Living on a farm and parental allergen sensitization are reflected in the intrauterine environment at the gene expression level.

Impaired Toll-like receptor 2 signalling in monocytes from 5-year-old allergic children

The relative composition of the two major monocytic subsets CD14(+)CD16(-) and CD14(+)CD16(+) is altered in some allergic diseases. These two subsets display different patterns of Toll-like receptor levels, which could have implications for activation of innate immunity leading to reduced immunoglobulin E-specific adaptive immune responses. This study aimed to investigate if allergic status at the age of 5 years is linked to differences in monocytic subset composition and their Toll-like receptor levels, and further, to determine if Toll-like receptor regulation and cytokine production upon microbial stimuli is influenced by the allergic phenotype. Peripheral blood mononuclear cells from 5-year-old allergic and non-allergic children were stimulated in vitro with lipopolysaccharide and peptidoglycan. Cells were analysed with flow cytometry for expression of CD14, Toll-like receptors 2 and 4 and p38-mitogen-activated protein kinase (MAPK). The release of cytokines and chemokines [tumour necrosis factor, interleukin (IL)-1 beta, IL-6, IL-8, IL-10, IL-12p70] into culture supernatants was measured with cytometric bead array. For unstimulated cells there were no differences in frequency of the monocytic subsets or their Toll-like receptor levels between allergic and non-allergic children. However, monocytes from allergic children had a significantly lower up-regulation of Toll-like receptor 2 upon peptidoglycan stimulation. Further, monocytes from allergic children had a higher spontaneous production of IL-6, but there were no differences between the two groups regarding p38-MAPK activity or cytokine and chemokine production upon stimulation. The allergic subjects in this study have a monocytic population that seems to display a hyporesponsive state as implicated by impaired regulation of Toll-like receptor 2 upon peptidoglycan stimulation.

Presymptomatic differences in Toll-like receptor function in infants who have allergy

BACKGROUND

Microbial exposure might play a key role in allergy development, but little is known about the role of Toll-like receptors (TLRs).

OBJECTIVE

This study explored the association between neonatal TLR microbial recognition/function, allergy risk (maternal allergy), and prospective allergy development.

METHODS

Cord blood mononuclear cells (n = 111) were cultured either alone or with optimal concentrations of TLR ligands: lipoteichoic acid (TLR2), polyinosinicpolycytidylic acid (TLR3), LPS with IFN-gamma (TLR4), flagellin (TLR5), imiquimod R837 (TLR7), or CpG (TLR9). Cytokine responses were assessed in relation to allergy risk (maternal allergy) and allergy outcomes (sensitization, food allergy, and atopic dermatitis) at 12 months of age.

RESULTS

Maternal allergy (n = 59) was associated with significantly higher neonatal IL-12 and IFN-gamma responses to TLR2, TLR3, and TLR4 activation, whereas TNF-alpha and IL-6 responses to TLR2, TLR4, and TLR5 activation were significantly higher in newborns who subsequently had allergic disease (n = 32). Notably, consistent with previous reports, newborns who had disease had lower T(H)1 IFN-gamma response to mitogens (PHA).

CONCLUSION

Allergic disease was associated with increased (rather than decreased) perinatal TLR responses. Further studies are needed to determine how these responses track in the postnatal period and whether this relative hyperresponsiveness is a product of intrauterine influences, including maternal atopy, functional genetic polymorphisms, or both.

Lower expression of TLR2 and SOCS-3 is associated with Schistosoma haematobium infection and with lower risk for allergic reactivity in children living in a rural area in Ghana

Background

Helminth infections are prevalent in rural areas of developing countries and have in some studies been negatively associated with allergic disorders and atopy. In this context little is known of the molecular mechanisms of modulation involved. We have characterized the innate immune responses, at the molecular level, in children according to their helminth infection status and their atopic reactivity to allergens.

Methodology/Principal Findings

The mRNA expression of several genes of the innate immune system that have been associated with microbial exposure and allergy was examined in 120 school children in a rural area in Ghana. Helminth infections were common and atopy rare in the study area. The analysis of gene expression in ex vivo whole blood samples reflected the levels of corresponding proteins. Using this approach in a population of school children in whom the presence of Schistosoma haematobium infection was associated with protection from atopic reactivity, we found that the level of TLR2 and SOCS-3, genes associated with atopy in the children, were significantly downregulated by presence of S. haematobium infection.

Conclusions

S. haematobium infections modulate the expression of genes of the innate immune system (TLR2 and SOCS-3); these are genes that are associated with increased allergic inflammatory processes, providing a molecular link between the negative association of this infection and atopy in rural children in Ghana.

Inflammatory diseases such as atopic disorders are a major health problem in the Western world, but their prevalence is also increasing in developing countries, especially in urban centres. There is increasing evidence that exposure to a rural environment with high burden of compounds derived from parasites and microorganisms is associated with protection from atopic disorders. Since urbanisation is progressing at a rapid pace, particularly in less-developed nations, there is a need to understand the molecular processes that control the progress towards the development of allergic diseases in developing countries. In this study we have examined a population of school children living in a rural area of Ghana, where helminth (worm) infections are prevalent and associated with protection from skin reactivity to house dust mite. Blood samples were collected from these children and analysed for the expression levels of several genes involved in the development of a pro allergic immune system. The results point at a potential molecular link that might explain the negative association between schistosome infections and allergies.

Maternal smoking in pregnancy: do the effects on innate (toll-like receptor) function have implications for subsequent allergic disease?

Subtle increases in immaturity of immune function in early infancy have been implicated in the rising susceptibility to allergic disease, particularly relative impairment of type 1 interferon (IFN)-γ responses in the neonatal period. Although genetic predisposition is a clear risk factor, the escalating rates of allergic disease in infancy suggest that environmental factors are also implicated. We previously showed that maternal smoking in pregnancy may impair neonatal IFN-γ responses. Our more recent studies now indicate that this common avoidable toxic exposure is also associated with attenuation of innate immune function, with attenuated Toll-like receptor (TLR)-mediated microbial responses (including TLR-2, -3, -4, and -9 responses). Most notably, the effects were more marked if the mothers were also allergic. In this review, we discuss the significance of these observations in the context of the emerging hypothesis that variations in TLR function in early life may be implicated in allergic propensity. There is now growing evidence that many of the key pathways involved in subsequent T-cell programming and regulation (namely, antigen-presenting cells and regulatory T cells) rely heavily on microbe-driven TLR activation for maturation and function. Factors that influence the function and activity of these innate pathways in early life may contribute to the increasing predisposition for allergic disease. Although "cleaner" environments have been implicated, here we explore the possibility that other common environmental exposures (such as maternal smoking) could also play a role.

Could peripartum antibiotics have delayed health consequences for the infant?

Antibiotics are increasingly prescribed in the peripartum period, for both maternal and fetal indications. Their effective use undoubtedly reduces the incidence of specific invasive infections in the newborn, such as group B streptococcal septicaemia. However, the total burden of infectious neonatal disease may not be reduced, particularly if broad-spectrum agents are used, as the pattern of infections has been shown to alter to allow dominance of previously uncommon organisms. This area has been relatively understudied, and there are almost no studies of long-term outcome. Recent findings suggest that such long-term data should be sought. First, there is evidence that organisms initially colonising the gut at birth may establish chronic persistence in many children, in contrast to prompt clearance if first encountered in later infancy, childhood or adulthood. Second, there is a rapidly advancing basic scientific data showing that individual members of the gut flora specifically induce gene activation within the host, modulating mucosal and systemic immune function and having an additional impact on metabolic programming. We thus review the published data on the impact of perinatal antibiotic regimens upon composition of the flora and later health outcomes in young children and summarise the recent scientific findings on the potential importance of gut flora composition on immune tolerance and metabolism.