Cord blood mononuclear cell cytokine responses in relation to maternal house dust mite allergen exposure

Ascariasis as a model to study the helminth/allergy relationships

Ascariasis is the most frequent soil transmitted helminthiasis and, as well as other helminth infections, is expected to influence the clinical presentation of allergic diseases such as asthma. Indeed, several clinical and experimental works have shown an important impact either increasing or suppressing symptoms, and the same effects have been detected on the underlying immune responses. In this review we analyze the work on this field performed in Colombia, a Latin American tropical country, including aspects such as the molecular genetics of the IgE response to Ascaris; the allergenic activity of Ascaris IgE-binding molecular components and the immunological and clinical influences of ascariasis on asthma. The analysis allows us to conclude that the impact of ascariasis on the inception and evolution of allergic diseases such as asthma deserves more investigation, but advances have been made during the last years. The concurrent parasite-induced immunostimulatory and immunosuppressive effects during this helminthiasis do modify the natural history of asthma and some aspects of the practice of allergology in the tropics. Theoretically it can also influence the epidemiological trends of allergic diseases either by its absence or presence in different regions and countries.

Allergen-specific IL-5 responses in early childhood predict asthma at age eight

Background

The pattern of development of allergen-specific T cell cytokine responses in early childhood and their relation to later disease is poorly understood. Here we describe longitudinal changes in allergen-stimulated T cell cytokine responses and their relation to asthma and allergic disease during the first 8 years of life.

Methods

Subjects with a family history of asthma, who were enrolled antenatally in the Childhood Asthma Prevention Study (public trials registration number ACTRN12605000042640), had skin prick tests, clinical evaluation for asthma and eczema, and in vitro assessment of T cell cytokine responses to HDM extract performed at ages 18 months (n = 281), 3 years (n = 349), 5 years (n = 370) and 8 years (n = 275). We measured interleukin (IL-) 13 at 3, 5 and 8 years, and IL-5, IL-10, and interferon-γ (IFN-γ), at 18 months, 3, 5 and 8 years by ELISA. A cohort analysis was undertaken. Independent effects of cytokine responses at each age on the risk of asthma and allergic outcomes at age 8 years were estimated by multivariable logistic regression.

Results

HDM-specific IL-5 responses increased with age. HDM-specific IL-13 and IL-10 responses peaked at age 5 years. HDM-specific IL-5 responses at 3 years, 5 years and 8 years were significantly associated with the presence of asthma and atopy at 8 years. IL-13 responses at 3 years, 5 years and 8 years were significantly associated with atopy at 8 years, but this association was not independent of the effect of IL-5. Other HDM-specific cytokine responses were not independently related to asthma or eczema at 8 years.

Conclusion

HDM-specific IL-5 responses at age 3 years or later are the best measure of T cell function for predicting asthma at age 8 years.

Food allergens are transferred intact across the rat blood-placental barrier in vivo

We investigated the mechanism of transplacental macromolecular transport in rats on the nineteenth day of pregnancy using tracers, transmission electron microscopy and immunohistochemistry. The blood-placental barrier of full-term rat placentas was composed of a trilaminar layer of trophoblast cells that separates the fetal capillaries from the maternal blood spaces: a layer of cytotrophoblasts lining the maternal blood space and a bilayer of syncytiotrophoblast surrounding the fetal capillaries. Horseradish peroxidase, intravenously injected into the maternal circulation, was found in the maternal blood spaces, the interspaces between the cytotrophoblasts and the syncytiotrophoblast I, many pits and small vesicles in the syncytiotrophoblast I, vesicles of the syncytiotrophoblast II, fetal connective tissue and fetal capillaries. Intravenously injected ovalbumin was detected in the maternal blood spaces, a trilaminar layer and the fetal capillaries. Neonatal Fc receptor (FcRn), a receptor for IgG, was localized at the maternal side of the blood-placental barrier. These results show that the structure of the rat blood-placental barrier is quite similar to the human blood-placental barrier, and non-specific macromolecules and food allergens may penetrate through the blood-placental barrier of the full-term placenta from the maternal to fetal circulation mediated by FcRn.

T-cell activation genes differentially expressed at birth in CD4+ T-cells from children who develop IgE food allergy

BACKGROUND

Presymptomatic immaturity in neonatal T-cell function is a consistent antecedent of allergic disease, including reduced responsiveness to polyclonal activation.

METHODS

To elucidate the underlying mechanisms, we examined for differences in T-cell gene expression in longitudinal samples collected at birth and at 1 year of age in children with (n = 30) and without IgE-mediated food allergy (n = 30). We employed a low-level soluble anti-CD3 stimulus to activate the T-cell receptor (TCR) and surveyed gene expression by DNA microarray in purified CD4(+) T-cells. Allergen-specific responses were assessed in parallel functional studies.

RESULTS

At birth, the allergic group showed a reduced number of genes up regulated in response to anti-CD3 treatment on the microarray and a reduced lympho proliferative capacity, suggesting clear differences in T-cell signalling pathways. Polymerase chain reaction (PCR) validation of candidate genes confirmed significantly lower expression of a number of genes in the allergic group including RELB, NFKB2, LIF and FAS. By 12 months of age, there were marked changes in the anti-CD3 response in all infants, culminating in upregulation of cytokine genes (IL-5, IL-13, IL-17 and IL-22). Neonatal differences were no longer apparent. Instead, the allergic group, all symptomatic by this age, showed differential expression of T-cell lineage pathways including GATA-3, MAL and FcER1 in unstimulated T-cells. Allergen stimulation induced significantly higher cytokines production (IL-5, IL-13 and IFNγ) in the allergic group.

CONCLUSION

Although transient, suboptimal neonatal T-cell activation pathways that signal through the NF-κB complex may affect the developmental transition of T-cell phenotypes in the periphery shortly after birth and may increase the risk of food allergy.

Maternal diet during pregnancy: an emerging risk factor for childhood asthma

Evaluation of: Willers SM, Wijga AH, Brunekreef B et al. Maternal food consumption during pregnancy and the longitudinal development of childhood asthma. Am. J. Respir. Crit. Care Med. 178, 124-131 (2008). It has been hypothesized that the recent marked increase in the prevalence of asthma may, in part, be a consequence of changing diet. There is increasing interest in the possibility that childhood asthma may be influenced by maternal diet during pregnancy and an increasing number of studies have highlighted associations between childhood asthma and maternal intake of certain foods (e.g., fish, fruits and vegetables) and nutrients (e.g., vitamin E, vitamin D, zinc and polyunsaturated fatty acids) during pregnancy. Maternal diet during pregnancy has the potential to influence fetal immune and airway development during a critical period of life with long-term irreversible consequences, such as childhood asthma. Further research, particularly intervention studies, needs to be carried out to establish whether dietary intervention during pregnancy can be used as a healthy, low-cost, public-health measure to reduce the prevalence of childhood asthma.

Balance between early life tolerance and sensitization in allergy: dependence on the timing and intensity of prenatal and postnatal allergen exposure of the mother

Allergens can be maternally transferred to the fetus or neonate, though it is uncertain how this initial allergen exposure may impact the development of allergy responses. To evaluate the roles of timing and level of maternal allergen exposure in the early life sensitization of progeny, female BALB/c mice were given ovalbumin (OVA) orally during pregnancy, lactation or weekly at each stage to investigate the immunoglobulin E (IgE) antibody production and cellular responsiveness of their offspring. Exposure to OVA during pregnancy was also evaluated in OVA-specific T-cell receptor (TCR) transgenic (DO11.10) mice. The effect of prenatal antigen exposure on offspring sensitization was dependent on antigen intake, with low-dose OVA inducing tolerance followed by neonatal immunization that was sustained even when pups were immunized when 3 weeks old. These offspring received high levels of transforming growth factor-beta via breastfeeding. High-dose exposure during the first week of pregnancy or perinatal period induced transient inhibition of IgE production following neonatal immunization; although for later immunization IgE production was enhanced in these offspring. Postnatal maternal antigen exposure provided OVA transference via breastfeeding, which consequently induced increased offspring susceptibility to IgE antibody production according to week post-birth. The effect of low-dose maternal exposure during pregnancy was further evaluated using OVA transgenic TCR dams as a model. These progeny presented pronounced entry of CD4(+) T cells into the S phase of the cell cycle with a skewed T helper type 2 response early in life, revealing the occurrence of allergen priming in utero. The balance between tolerance and sensitization depended on the amount and timing of maternal allergen intake during pregnancy.

IL-5 T-cell responses to house dust mite are associated with the development of allergen-specific IgE responses and asthma in the first 5 years of life

BACKGROUND

Allergen-specific T(H)2-like cytokine responses are considered to be important in sensitization and allergic diseases.

OBJECTIVE

To examine the profile of house dust mite (HDM) stimulated T-cell cytokines and their relationship to allergic disease in children over the period of the first 5 years of life.

METHODS

Subjects with a family history of asthma who were enrolled antenatally in the Childhood Asthma Prevention Study and had skin prick tests, clinical evaluation for asthma and eczema, and in vitro assessment of lymphocyte cytokine responses to HDM extract performed at ages 18 months (n = 281), 3 years (n = 349), and 5 years (n = 370). IL-13 at 3 and 5 years and IL-5, IL-10, and IFN- gamma at 18 months, 3 years, and 5 years were measured by ELISA.

RESULTS

House dust mite-specific cytokine responses increased with age for all cytokines except IFN-gamma. HDM-specific IL-5 responses at 3 years and 5 years were significantly positively related to skin prick test positivity at 5 years. IL-5 responses at 5 years were also significantly related to asthma at 5 years. Other HDM-specific cytokine responses were not related to asthma or eczema at 5 years. Responses were not altered by a HDM avoidance intervention.

CONCLUSION

IL-5 responses to HDM, the dominant local inhalant allergen, are related to the expression of clinical illness at age 5 years.

CLINICAL IMPLICATIONS

The T-cell response to HDM, as reflected in IL-5 production, is acquired over the first years of life and may play a role in the expression of allergic airways disease.

T and B cell responses to HDM allergens and antigens

House dust mites provide well-characterized proteins to study human responses to inhaled antigens. Even in the absence of allergy they induce a high frequency of T cell precursors. The healthy response manifests by T cell proliferation and Th1 cytokines with little antibody. Responses of allergic people include Th1 and Th2 cytokines and IgE, IgG1, and IgG4 antibodies. Regulatory cells limit effector responses in healthy people. About half the IgE and IgG antibodies bind the group 1 and 2 allergens and 30% bind the group 4, 5, and 7 allergens. Although HLA independent, the recognition of the group 1 allergen shows an immunodominant region and a T cell receptor bias. The major allergens are not produced in higher amounts than many of the poorly non-allergenic proteins. The non-allergenic mite ferritin antigen shows high T cell proliferative responses with mixed cytokine production.

Maternal allergen exposure as a risk factor for childhood asthma

The role of early allergen exposure has been a central focus in the effort to curtail the rising rates of allergic disease. Exposures in pregnancy have been of interest because the first signs of disease are often seen in early infancy. However, so far, strategies to avoid or reduce allergen exposure in pregnancy have had disappointing results in reducing disease. Although there is growing evidence that the fetus is exposed to allergens, this appears to be physiologic and not a risk factor for allergic disease. It is still not clear if this exposure has some role in the context of normal tolerance. Although infants who later develop allergic disease show some differences in neonatal allergen-specific responses, these are not consistent. Furthermore, the magnitude and frequency of responses do not correlate well with maternal allergen exposure, and it now seems likely that these responses do not reflect true immunologic "memory." Despite this, there is accumulating evidence that a number of other exposures in pregnancy have the capacity to significantly influence immune development and alter the risk for allergic responses to allergens. This underscores the importance of further defining the events in this early period, to determine causal pathways and better strategies for prevention.

Exposure of the fetus and infant to hens' egg ovalbumin via the placenta and breast milk in relation to maternal intake of dietary egg

BACKGROUND

Maternally derived allergens may be transferred to the developing infant during pregnancy and lactation. However, it is not known how manipulation of environmental allergen levels might impact on this early-life exposure.

OBJECTIVE

To measure dietary egg allergen (ovalbumin (OVA)) in gestation-associated environments, in relation to maternal dietary egg intake.

METHOD

OVA was measured by allergen-specific ELISA in maternal blood collected throughout pregnancy, infant blood at birth (umbilical cord) and in breast milk at 3 months post-partum. Samples derived from pregnant women undergoing diagnostic amniocentesis at 16-18 weeks gestation who were not subject to any dietary intervention, and from pregnant women, with personal or partner atopy, randomized to complete dietary egg exclusion or an unmodified healthy diet before 20 weeks gestation as a primary allergy prevention strategy. Maternal dietary egg intake was monitored closely throughout the study period by diary record and serial measurement of OVA-specific immunoglobulin G concentration.

RESULTS

Circulating OVA was detected throughout pregnancy in 20% of women and correlated with both presence (P<0.001) and concentration (r=0.754, P<0.001) of infant OVA at birth (umbilical cord). At 3 months post-partum OVA was detected in breast milk samples of 35% women, in higher concentrations than measured in blood. Blood and breast milk OVA were not related to maternal dietary intake or atopic pre-disposition.

CONCLUSIONS

Rigorous dietary egg exclusion does not eliminate trans-placental and breast milk egg allergen passage. This early-life exposure could modulate developing immune responses.

The potential impact of early exposures to geohelminth infections on the development of atopy

Microbial exposures in early life may provide important signals for immune maturation and the development of an antiinflammatory network thereby preventing the development of dysregulated immune responses such as that associated with allergic disease. The human immune system has evolved in the presence of intense helminth infections and has developed regulatory mechanisms to limit the harmful inflammation that can be caused by the potent allergens secreted by these chronic pathogens. Geohelminth infections are highly prevalent childhood infections, and there is strong evidence that chronic geohelminth infections provide protection against atopy in the rural tropics. Because the early environmental exposures that may lead to the development of atopy are likely to occur in the first few years of life, geohelminth infections may exert their protective effects at this time. Early exposures to geohelminth antigens could occur transplacentally, through breast milk, or through early infant exposures, and could induce tolerance to parasite antigens resulting in suppressed allergic responses to the parasite. Tolerization to parasite antigens could suppress allergic responses to inhalant allergens through bystander effects or through tolerization of crossreactive epitopes that are shared between geohelminth parasites and inhalant allergens. Tolerization to crossreactive allergens could occur by thymic deletion or through peripheral mechanisms such as regulatory T cells. Immunologic studies of the mechanisms by which early exposures to geohelminth infections affect immune polarization to inhalant allergens are likely to provide important insights into the early regulation of the immune response and may lead to the design of novel interventions for the prevention of allergic disease.

Intestinal worms and human allergy

The immunoepidemiological interactions between intestinal worm (or geohelminth) infections and allergy are of great interest to parasitologists, immunologists, and allergists because of the close similarities between the human immune response to geohelminth parasites and environmental allergens. Allergic diseases appear to be most rare in populations living in the rural tropics with high rates of infection with geohelminth parasites, and this has led to suggestions that the relationship between geohelminth infections and allergy may be causal. Allergic sensitization and disease results from a complex interaction between environmental exposures and genetic background, and the numerous epidemiological studies that have investigated the relationship between allergy and geohelminth infections have provided conflicting findings. The strongest epidemiological evidence for a causal association is provided by intervention studies that demonstrate evidence for an effect of anthelmintic treatment on atopy or asthma risk. There is evidence also for an inverse relationship between geohelminth infection and either atopy or asthma symptoms from cross-sectional studies that have been conducted in areas of high infection prevalence. Chronic geohelminth infections could affect allergy risk by modulation of the immune response to environmental allergens, and an area of great research activity at present is the investigation of the role of regulatory T cells in modulating host inflammatory responses. However, a causal association between geohelminth infections and allergy remains to be proven, and prospective and intervention studies are required that investigate the development of allergy in early life at a time when humans are first exposed to geohelminth parasites and their antigens.

Prenatal exposure to house dust mite allergen (Der p 1), cord blood T cell phenotype and cytokine production and atopic dermatitis during the first year of life

This study investigated the influence of prenatal exposure to house dust mite (HDM, D. pteronyssinus) on interleukin (IL)-2, interferon-gamma (IFN-gamma) and IL-4 producing CD4(+) and CD8(+) T lymphocytes in cord blood as well as on the development of sensitization and occurrence of atopic dermatitis (AD) as the first symptom of allergy during the first year of life. Dust samples (n = 22) were collected by vacuum cleaning the maternal mattress during early to mid-pregnancy. In these samples, the amount of the major HDM antigen (Der p 1) was assessed by a sensitive enzyme-linked immunosorbent assay technique (detection limit 0.004 microg/g dust). Flow cytometry was used to determine cord blood lymphocyte subtypes and to quantify the intracellular amounts of IL-2, IFN-gamma and IL-4 produced by cord blood CD4(+) helper and CD8(+) cytotoxic T lymphocytes, both spontaneously and after stimulation with phorbol-12-mirystate-13-acetate and ionomycin. Children were followed for 1 yr for the presence of symptoms associated with allergy. In addition, at the age of 1 yr specific IgE to different classical inhalant and food allergens was measured. Higher prenatal exposure to Der p 1 (>0.2 microg/g dust) was associated with a significant lower percentage of IFN-gamma producing stimulated CD4(+) T lymphocytes, compared with lower prenatal Der p 1 exposure (p = 0.03). The presence of AD during the first year of life (n = 9) was associated with an increased number of naive CD4(+) CD45RA(+) lymphocytes (p = 0.03), with an increased spontaneous IL-4 production by CD8(+) lymphocytes (p = 0.04) and with a decreased percentage of IFN-gamma producing stimulated CD4(+) lymphocytes (p = 0.04). Furthermore, exposure to HDM during pregnancy tended to be higher in mothers of children with AD during the first year of life when compared with those without AD (p = 0.08). This study shows that the level of prenatal exposure to Der p 1 influences the immune profile of cord blood T lymphocytes and the clinical outcome in early life. Therefore, the prenatal environment must be regarded as a possible early risk factors for allergic diseases in children.

Early origins of allergic disease: a review of processes and influences during early immune development

PURPOSE OF REVIEW

With the disturbing increase in allergic disease, there is a pressing need to determine the causes, pathogenesis and safe avenues for disease prevention. Although events in early life appear important, no causal pathways have been identified. This review examines new developments in the area of foetal and early postnatal immune maturation. It secondly addresses early predisposing influences and protective factors that may have a future role in allergy prevention.

RECENT FINDINGS

New developments in the understanding of the ontogeny of allergen-specific immune responses in atopic infants are discussed, including the role of early type 1 and 2 immune responses, and how these are influenced by perinatal antigen presenting cell and T-cell immaturity. The controversial role of early dietary exposures including breastfeeding, food allergens, hydrolyzed formulae and other dietary factors including omega-3 fatty acids are discussed in the context of the most recent literature. Equally contentious, the role of early house dust and pet allergen exposure is discussed in light of new epidemiological studies and disappointing early results of multicentre allergen avoidance studies. Finally, a number of studies in animals and humans suggest that bacterial products can influence early immune development, providing a new potential therapeutic avenue for disease treatment and prevention.

SUMMARY

Complex multifactorial genetic and environmental interactions make research in this area difficult and apparent associations with allergic disease may not be causal in nature. Many current targets for prevention, such as early allergen exposure and infant feeding practices, are proving to be ineffective and may not be directly implicated in rising rates of disease.