Characterization of plasma cytokines in an infant population cohort of challenge-proven food allergy

Alteration of Immunoregulatory Patterns and Survival Advantage of Key Cell Types in Food Allergic Children

All allergic responses to food indicate the failure of immunological tolerance, but it is unclear why cow's milk and egg (CME) allergies resolve more readily than reactivity to peanuts (PN). We sought to identify differences between PN and CME allergies through constitutive immune status and responses to cognate and non-cognate food antigens. Children with confirmed allergy to CME (n = 6) and PN (n = 18) and non-allergic (NA) (n = 8) controls were studied. Constitutive secretion of cytokines was tested in plasma and unstimulated mononuclear cell (PBMNC) cultures. Blood dendritic cell (DC) subsets were analyzed alongside changes in phenotypes and soluble molecules in allergen-stimulated MNC cultures with or without cytokine neutralization. We observed that in allergic children, constitutively high plasma levels IL-1β, IL-2, IL-4, IL-5 and IL-10 but less IL-12p70 than in non-allergic children was accompanied by the spontaneous secretion of sCD23, IL-1β, IL-2, IL-4, IL-5, IL-10, IL-12p70, IFN-γ and TNF-α in MNC cultures. Furthermore, blood DC subset counts differed in food allergy. Antigen-presenting cell phenotypic abnormalities were accompanied by higher B and T cell percentages with more Bcl-2 within CD69+ subsets. Cells were generally refractory to antigenic stimulation in vitro, but IL-4 neutralization led to CD152 downregulation by CD4+ T cells from PN allergic children responding to PN allergens. Canonical discriminant analyses segregated non-allergic and allergic children by their cytokine secretion patterns, revealing differences and areas of overlap between PN and CME allergies. Despite an absence of recent allergen exposure, indication of in vivo activation, in vitro responses independent of challenging antigen and the presence of unusual costimulatory molecules suggest dysregulated immunity in food allergy. Most importantly, higher Bcl-2 content within key effector cells implies survival advantage with the potential to mount abnormal responses that may give rise to the manifestations of allergy. Here, we put forward the hypothesis that the lack of apoptosis of key immune cell types might be central to the development of food allergic reactions.

Sustained antigens delivery using composite microneedles for effective epicutaneous immunotherapy

Allergen-specific immunotherapy (SIT) is a desirable way of therapy for various allergic diseases such as food allergy (FA). However, frequent visits for more than 3 years and potential adverse effects often hinder patient compliance. Recently, many researchers started focusing on microneedles (MNs) as a new method for SIT. In this study, we proposed an implantable MNs system produced by a two-step casting process, consisting of OVA (antigen)-loaded silk microneedles and a dissolvable, flexible polyvinyl alcohol (PVA) pedestal. Different from PVA, silk fibroin hydrogel has preferable vaccine release ability in vivo and in vitro. Once MNs are inserted into the skin, the PVA pedestal can dissolve in the interstitial fluid of the excised skin within 5 min and implant the OVA-loaded silk microneedle tips in dermal layer as a sustained antigen depot, thus inducing long-lasting immune response for at least 2 weeks. After receiving 3 doses of MN-based immunotherapy, the immune response in OVA-sensitized mice was successfully suppressed, with no apparent side effects. Compared to conventional subcutaneous immunotherapy (total dose of 150 [Formula: see text]g), MN immunotherapy ameliorated systemic anaphylaxis more effectively even at a lower dose (total dose of 30 [Formula: see text]g), demonstrating the antigen dose-sparing potential of the proposed MNs. Moreover, due to the prolonged release effect of silk-PVA composite MNs, the frequency of immunotherapy can be significantly reduced. To sum up, through prolonged skin exposure to antigen, this implantable designed MN may offer a new therapeutic strategy for FA treatment with significant improvements in efficacy and convenience. Schematic illustration of silk-PVA composite microneedles, consisting of OVA (antigen)-loaded silk microneedles and a dissolvable, flexible PVA pedestal. Once inserted into the skin, the PVA pedestal can dissolve in the interstitial fluid of the excised skin within 5 min. Subsequently, the OVA-loaded silk microneedle tips were implanted in the dermal layer as a sustained antigen depot and induced long-lasting immune response. This MNs-based immunotherapy can significantly modulate the Th1/Th2 imbalance of sensitized mice.

Hydrolyzed chicken liver used as single source of animal protein in diet and its effect on cytokines, immunoglobulins, and fecal microbiota profile of adult dogs

Dogs with food allergies and enteropathies may require hydrolyzed diets to prevent or reduce clinical signs, therefore the protein sources used in these diets must be previously characterized and evaluated in healthy dogs. This study aimed to investigate the effects of a hydrolyzed chicken liver powder-based diet (HCLP) versus a poultry by-product meal and bovine meat and bone meal-based diet (Control), on complete blood count (CBC), cytokine, immunoglobulins responses (assessed on days 0, 15, 30 and 45), and fecal microbiota (assessed on day 45) in healthy adult dogs. The CBC did not differ between diets (P>0.05), remaining within reference range. Total plasma IL-4 concentrations were decreased over time independent of the dietary treatment (P<0.001). Total plasma IgA decreased on day 30 compared to days 0 and 45 in dogs fed the control diet (P<0.001). Total plasma IgE concentrations were reduced on days 30 and 45 in dogs fed the control diet, and on days 15 vs 30 and 15 vs 45 in dogs fed HCLP diet (P = 0.001). The 16S rRNA gene sequencing showed similar species richness and abundances of phyla and genera between diets (P>0.05). β-diversity principal coordinate analysis plots demonstrated that HCLP group had a higher similarity than control. Based on our results, healthy adult dogs fed a HCLP based diet maintained normal values for hematological and immunological characteristics, and fecal microbiota after 45 days of feeding.

High-dimensional immune profiles correlate with phenotypes of peanut allergy during food-allergic reactions

BACKGROUND

Food challenges carry a burden of safety, effort and resources. Clinical reactivity and presentation, such as thresholds and symptoms, are considered challenging to predict ex vivo.

AIMS

To identify changes of peripheral immune signatures during oral food challenges (OFC) that correlate with the clinical outcome in patients with peanut allergy (PA).

METHODS

Children with a positive (OFC⁺ , n = 16) or a negative (OFC^- , n = 10) OFC-outcome were included (controls, n = 7). Single-cell mass cytometry/unsupervised analysis allowed unbiased immunophenotyping during OFC.

RESULTS

Peripheral immune profiles correlated with OFC outcome. OFC⁺ -profiles revealed mainly decreased Th2 cells, memory Treg and activated NK cells, which had an increased homing marker expression signifying immune cell migration into effector tissues along with symptom onset. OFC^- -profiles had also signs of ongoing inflammation, but with a signature of a controlled response, lacking homing marker expression and featuring a concomitant increase of Th2-shifted CD4⁺ T cells and Treg cells. Low versus high threshold reactivity-groups had differential frequencies of intermediate monocytes and myeloid dendritic cells at baseline. Low threshold was associated with increased CD8⁺ T cells and reduced memory cells (central memory [CM] CD4⁺ [Th2] T cells, CM CD8⁺ T cells, Treg). Immune signatures also discriminated patients with preferential skin versus gastrointestinal symptoms, whereby skin signs correlated with increased expression of CCR4, a molecule enabling skin trafficking, on various immune cell types.

CONCLUSION

We showed that peripheral immune signatures reflected dynamics of clinical outcome during OFC with peanut. Those immune alterations hold promise as a basis for predictive OFC biomarker discovery to monitor disease outcome and therapy of PA.

Altered immune cell profiles and impaired CD4 T-cell activation in single and multi-food allergic adolescents

BACKGROUND

Approximately 5% of adolescents have a food allergy, with peanut and tree nut allergies the most common. Having two or more food allergies in adolescence also doubles the risk of any adverse food reaction, and is associated with increased dietary and social burden. Investigations of immune function in persistently food allergic children are rare.

OBJECTIVE

In the present study, we aimed to investigate the immune mechanisms that underlie food allergy in adolescence.

METHODS

We used high-dimensional flow cytometry, unsupervised computational analysis and functional studies to comprehensively phenotype a range of non-antigen-specific immune parameters in a group of well-characterized adolescents with clinically defined single peanut allergy, multi-food allergy and aged-matched non-food allergic controls.

RESULTS

We show that food allergic adolescents have higher circulating proportions of dendritic cells (p = .0084, FDR-adjusted p = .087, median in no FA: 0.63% live cells, in FA: 0.93%), and higher frequency of activated, memory-like Tregs relative to non-food allergic adolescents (p = .011, FDR-adjusted p = .087, median in no FA: 0.49% live cells, in FA: 0.65%). Cytokine profiling revealed that CD3/CD28 stimulated naïve CD4 T cells from food allergic adolescents produced less IL-6 (p = .0020, FDR-adjusted p = .018, median log2 fold change [stimulated/unstimulated] in no FA: 3.03, in FA: 1.92) and TNFα (p = .0044, FDR-adjusted p = .020, median in no FA: 9.16, in FA: 8.64) and may secrete less IFNγ (p = .035, FDR-adjusted p = .11, median in no FA: 6.29, in FA: 5.67) than naïve CD4 T cells from non-food allergic controls. No differences between clinical groups were observed for LPS-stimulated monocyte secretion of cytokines.

CONCLUSIONS

These results have important implications for understanding the evolution of the immune response in food allergy throughout childhood, revealing that dendritic cell and T-cell signatures previously identified in early life may persist through to adolescence.

Hyper-Inflammatory Monocyte Activation Following Endotoxin Exposure in Food Allergic Infants

Several recent studies have reported a key role for innate cell hyper-responsiveness in food allergy. This has predominantly been observed in early life, with evidence that innate immune function may return to baseline if food allergy resolves in later childhood. Hallmarks of hyper-responsiveness include increased circulating frequency of monocytes and altered innate cell cytokine responses to in vitro exposure with bacterial endotoxin. These features mirror the defining signatures of trained innate immunity, seen in other complex diseases. In this study, detailed immune cell and cytokine profiling was performed on peripheral blood mononuclear cells at baseline from 27 1 year old infants in the HealthNuts cohort (n = 16 egg allergic and n = 11 non-allergic healthy controls) and following monocyte stimulation. We show that egg allergic infants have increased frequency of circulating monocytes, reduced numbers of regulatory CD4 T cells and increased monocyte: CD4 T cell ratios relative to healthy controls. Monocytes from both egg allergic and non-allergic infants responded to endotoxin stimulation with rapid cytokine production and downregulation of the surface receptor CD16, however monocytes from egg allergic infants were hyper-responsive, producing significantly more inflammatory cytokines (TNFα, IL-6, IL-1β, IL-8) and innate cell recruiting factors (MIP-1α) than healthy controls. This work indicates that monocytes of food allergic infants are programmed to a hyper-inflammatory phenotype and that the development of food allergy may be associated with trained immunity in early life.

Mass cytometry reveals cellular fingerprint associated with IgE+ peanut tolerance and allergy in early life

IgE-mediated peanut allergic is common, often serious, and usually lifelong. Not all individuals who produce peanut-specific IgE will react upon consumption of peanut and can eat the food without adverse reactions, known as sensitized tolerance. Here, we employ high-dimensional mass cytometry to define the circulating immune cell signatures associated with sensitized tolerance and clinical allergy to peanut in the first year of life. Key features of clinical peanut allergic are increased frequency of activated B cells (CD19^hiHLADR^hi), overproduction of TNFα and increased frequency of peanut-specific memory CD4 T cells. Infants with sensitized tolerance display reduced frequency but hyper-responsive naive CD4 T cells and an increased frequency of plasmacytoid dendritic cells. This work demonstrates the utility and power of high-dimensional mass cytometry analysis to interrogate the cellular interactions that are associated with allergic sensitization and clinical food allergy in the first year of life.

The utility of TNF-α, IL-6 and IL-10 in the diagnosis and/or follow-up food allergy

BACKGROUND

Several pro-inflammatory and anti-inflammatory mediators play a role in the immunopathogenesis of food allergy (FA). The aim of this study was to investigate the utility of serum biomarkers like interleukin (IL)-10, TNF-α, and IL-6 in the diagnosis and/or follow-up of FA.

METHODS

Sixty (25 females, 41.6%) newly diagnosed FA patients [IgE mediated (group-1, n=37), non-IgE (group-2, n=23)] with a median age of nine (1-33) months were enrolled. Twenty-four healthy children with a median age of eight (1-36) months constituted the control group (CG). In all the subjects, serum TNF-α, IL-6 and IL-10 levels were evaluated at the time of diagnosis and reassessed four weeks after therapeutic elimination diet (TED).

RESULTS

The mean white blood cell count and median absolute eosinophile count of the CG were significantly lower than group-1 (p values were 0.019 and 0.006, respectively). The mean absolute neutrophile count and the median IL-6 were significantly higher in group-1 when compared with group-2 (p values were 0.005 and 0.032, respectively. Median TNF-α and IL-6 levels were significantly higher in the pre-TED among all patients (p values were 0.005 and 0.018, respectively). In group-1, median TNF-α and IL-6 levels decreased significantly after TED (p values were 0.01 and 0.029, respectively).

CONCLUSIONS

Our findings support the role of inflammation in the pathogenesis of FA. Serum TNF-α and IL-6 levels may be useful markers for follow-up in FA, especially among IgE-mediated FA patients. Evaluation of IL-10 results was not sufficient for an interpretation of clinical tolerance.

A preliminary study assessing cytokine production following ex vivo stimulation of whole blood with diet in dogs with chronic enteropathy

Background

Ex vivo whole blood stimulation assays (WBSA) have been used to characterize the cytokine response to diet in cats. The present study aimed to use this assay to determine the cytokine response to diets being fed at the time of diagnosis to dogs with chronic enteropathy (CE) and to compare this to a control group of dogs presented for non-gastrointestinal (GI) causes.

Results

Dogs with chronic GI signs and dogs presented for non-GI causes were prospectively recruited. For each case, residual blood following diagnostic sampling was placed into heparin. WBSAs were performed using crude extracts of the diet currently being fed and provided by the owner. Supernatants were collected and analyzed for tumor necrosis factor (TNF)-alpha, interleukin (IL)-10 and IL-4 using an enzyme-linked immunosorbent assay. The case group consisted of 22 dogs with CE diagnosed on histopathology of GI biopsy and 9 with suspected CE. The non-GI group consisted of 18 dogs. Of the diets being fed at or prior to diagnosis, hydrolyzed protein diets elicited significantly lower IL-10 and TNF-alpha concentrations compared to commercial intact protein diets in dogs with confirmed or suspected CE (P-value 0.004 and < 0.001, respectively). Six out of 15 dogs with detectable IL-4 concentrations in the confirmed CE group had IL-4 to IL-10 ratios that exceeded the 95% confidence interval (CI) of the mean of the non-GI group (non-GI: 95% CI of IL-4:IL-10 = 0.64–2.71; confirmed CE: IL-4:IL-10 in 6 dogs = mean 22.40, range 2.77–89.11).

Conclusions

Hydrolyzed protein diets elicited a significantly reduced cytokine response when incubated with patient whole blood ex vivo compared to commercial intact protein diets in dogs with CE. The IL-4 to IL-10 ratio as a marker of dietary responsiveness warrants further investigation, together with assessment of the cytokine response to diet at the intestinal mucosal surface.

Innovation in Food Challenge Tests for Food Allergy

PURPOSE OF REVIEW

This review incorporates findings from studies of oral food challenges (OFC) over the last decade and highlights the latest innovations and understanding of the procedure.

RECENT FINDINGS

PRACTALL guidelines are widely used in OFC research, but there is still no international consensus on the OFC protocol in clinical practice. Guidelines for performing OFC in clinical practice have been updated to include oral food challenges for infants. There have been advances in predictive models for outcomes and severity of reaction during OFC that take into account multiple clinical data as well as newer laboratory modalities. Low-dose OFC and eliciting threshold dose determination are being examined for additional diagnostic and therapeutic use in the management of food allergy. Quality-of-life considerations have also been reviewed, as well as post-OFC assessment and care. The OFC remains an important diagnostic tool in the management of food allergy and in clinical research. Advances in the field should improve safety and broaden the clinical applications of this essential procedure.

Degradation of major allergens and allergenicity reduction of soybean meal through solid-state fermentation with microorganisms

In this study, we determined whether solid-state fermentation could degrade major allergens and reduce potential allergenicity of soybean meal (SBM). Solid-state fermentation was realized through a mixture of Lactobacillus casei, yeast, and Bacillus subtilis. High-performance liquid chromatography, size exclusion-high-performance liquid chromatography, and capillary liquid chromatography/tandem mass spectrometry coupled with electrospray ionization were used to examine the total amino acids and molecular weight distribution of the fermented soybean meal (FSBM). In addition, the potential allergenicity of FSBM was assessed by conducting in vitro competitive inhibition ELISA and oral sensitization and challenge of a BALB/c mice model. The results indicated that the total amino acid content increased and soy protein was degraded into polypeptides with low molecular weights that were derived from the hydrolysis of the allergen sequences N232-D383, G253-I265, E169-S215, G68-G98, A365-I375, and V153-A167. Moreover, the FSBM group exhibited a lower in vitro immunoglobulin E (IgE)-binding capacity than the SBM group. The BALB/c model indicated that the FSBM group manifested milder damage to the intestine, lower mMCP-1 and IgE levels, and higher IFN-γ levels as compared to the SBM group. These findings suggested that the potential allergenicity of SBM was reduced by the solid-state fermentation induced by the mixture of Lactobacillus casei, yeast, and Bacillus subtilis.

A descriptive pilot study of cytokine production following stimulation of ex-vivo whole blood with commercial therapeutic feline hydrolyzed diets in individual healthy immunotolerant cats

Background

Hydrolyzed diets are used in companion animals for the diagnosis and treatment of adverse food reaction. Similarly, hydrolyzed formulas are used in human infants with severe inflammatory bowel disease or milk allergy, and these must meet the standard of hypoallergenicity through rigorous testing. Unfortunately, no standards are currently applied to hydrolyzed veterinary therapeutic diets, and data for the immunogenicity of feline diets is also not available. Therefore, the main aim of this pilot study was to determine if ex-vivo whole blood stimulation assays could be used to characterize the cytokine response to hydrolyzed commercial diets in a small number of individual healthy immunotolerant cats. This approach has also been used to investigate cytokine production in response to cow milk protein in humans and currently similar studies do not exist in companion animals. Nine healthy cats previously eating the same basal diet were divided into groups and fed one of three hydrolyzed diets exclusively for 6 weeks. Heparinized whole blood was collected from each cat before and after the feeding trial. Ex-vivo whole blood stimulation assays were performed using crude extracts of the basal diet as a positive control, as this diet contained the same proteins present in the hydrolyzed diet but were intact, saline as a negative control, and each cat’s respective hydrolyzed diet. Supernatants were collected and analyzed for tumor necrosis factor-alpha, interleukin-10 (IL-10), and interleukin-4 using enzyme-linked immunosorbant assay.

Results

Seven cats produced detectable amounts of the anti-inflammatory cytokine IL-10 upon stimulation with the basal diet. Two cats produced detectable amounts of IL-10 upon stimulation with a hydrolyzed soy-based diet and one cat produced a detectable amount of IL-10 upon stimulation with a hydrolyzed chicken-based diet (>125 pg/mL).

Conclusions

Results from this pilot study suggest that in some healthy immunotolerant cats, some hydrolyzed diets may elicit a similar cytokine response compared to their basal diet, which contained the same proteins intact. Therefore, animals may be able to recognize and react to some hydrolyzed forms of tolerated proteins, and may also suggest IL-10 as a target for investigation as a potential marker for dietary tolerance in cats, however further studies would be necessary to corroborate this. Further studies are also needed to determine if this would also be the same in immunologically naïve, sensitized and clinically hypersensitized cats.

Stability of pro- and anti-inflammatory immune biomarkers for human cohort studies

BACKGROUND

Although discovery research has identified the importance of dozens of pro- and anti-inflammatory immune mediators in the pathogenesis, maintenance, exacerbation and resolution of inflammatory diseases, most human cohort studies have incorporated few or no immunological intermediate phenotypes in their analyses. Significant hindrances have been (1) the limited panel of biomarkers known to be readily detected in healthy human populations and (2) the stability, hence utility, of such biomarkers to repeated analysis.

METHODS

The frequency and stability of 14 plasma biomarkers linked to in vivo immune regulation of allergic and autoimmune inflammatory disorders was determined in 140 healthy pediatric and adult participants. The impact of initial and multiple subsequent freeze/thaw cycles on pro-inflammatory (CCL2, CXCL10, IL-18, TNFα, IL-6), anti-inflammatory (IL-10, sTNF-RII, IL-1Ra), acute phase proteins (CRP, PTX3) and other biomarkers (sST2, IL-1RAcP) was subsequently quantified.

RESULTS

Multiple biomarkers capable of providing an innate immune signature of inflammation were readily detected directly ex vivo in healthy individuals. These biomarker levels were unaffected when comparing paired data sets from freshly obtained, never frozen plasma or serum and matched aliquots despite extensive freeze/thaw cycles. Neither age nor sex affected stability. Similarly, no quantitative differences were found following repetitive analysis of inflammatory biomarkers in culture samples obtained following in vitro stimulation with TLR and RLR ligands.

CONCLUSIONS

A broad panel of in vivo and ex vivo cytokine, chemokine and acute phase protein biomarkers that have been linked to human chronic inflammatory disorders are readily detected in vivo and remain stable for analysis despite multiple freeze thaw cycles. These data provide the foundation and confidence for large scale analyses of panels of inflammatory biomarkers to provide better understanding of immunological mechanisms underlying health versus disease.

Changes in biomarkers during a six-month oral immunotherapy intervention for cow's milk allergy

AIM

Oral immunotherapy (OIT) is a promising but still experimental method to treat children with cow's milk (CM) allergy (CMA). We evaluated changes in allergic, immunological and inflammatory parameters, which happened during the six-month OIT for CMA.

METHODS

We treated 28 school-aged children with CMA using OIT with a double-blind placebo-controlled design. After the controlled study finished, the placebo group was treated with the same but open-label OIT protocol. Sixteen immune variables were tested before and after the six-month OIT.

RESULTS

Before OIT, the median serum CM-specific immunoglobulin (Ig) E was 18.0kIU/L in the intervention group and 9.4kIU/L in the placebo group (p = 0.46). At six months, interleukin (IL)-6 and IL-10 were significantly higher in the intervention group. When the changes during the blinded and open OIT were analysed together for both groups, blood eosinophils and serum total IgE decreased and milk-specific IgG and IgG4, serum IL-4 and IL-6, and serum leptin and resistin increased significantly.

CONCLUSION

Preliminary evidence was found that markers of allergy such as blood eosinophils and serum IgE decreased and milk-specific IgG and IgG4 increased during OIT. Adipokines, leptin and resistin, which functionally are cytokines linked to Th1-type response, increased during OIT.

Asthma, hay fever, and food allergy are associated with caregiver-reported speech disorders in US children

BACKGROUND

Children with asthma, hay fever, and food allergy may have several factors that increase their risk of speech disorder, including allergic inflammation, ADD/ADHD, and sleep disturbance. However, few studies have examined a relationship between asthma, allergic disease, and speech disorder. We sought to determine whether asthma, hay fever, and food allergy are associated with speech disorder in children and whether disease severity, sleep disturbance, or ADD/ADHD modified such associations.

METHODS

We analyzed cross-sectional data on 337,285 children aged 2-17 years from 19 US population-based studies, including the 1997-2013 National Health Interview Survey and the 2003/4 and 2007/8 National Survey of Children's Health.

RESULTS

In multivariate models, controlling for age, demographic factors, healthcare utilization, and history of eczema, lifetime history of asthma (odds ratio [95% confidence interval]: 1.18 [1.04-1.34], p = 0.01), and one-year history of hay fever (1.44 [1.28-1.62], p < 0.0001) and food allergy (1.35 [1.13-1.62], p = 0.001) were associated with increased odds of speech disorder. Children with current (1.37 [1.15-1.59] p = 0.0003) but not past (p = 0.06) asthma had increased risk of speech disorder. In one study that assessed caregiver-reported asthma severity, mild (1.58 [1.20-2.08], p = 0.001) and moderate (2.99 [1.54-3.41], p < 0.0001) asthma were associated with increased odds of speech disorder; however, severe asthma was associated with the highest odds of speech disorder (5.70 [2.36-13.78], p = 0.0001).

CONCLUSION

Childhood asthma, hay fever, and food allergy are associated with increased risk of speech disorder. Future prospective studies are needed to characterize the associations.

Food-allergic infants have impaired regulatory T-cell responses following in vivo allergen exposure

BACKGROUND

Regulatory T cells (Tregs) are critical for development of oral tolerance, and studies suggest that dysfunction of Tregs may lead to food allergy. However, to date, no study has investigated Treg responses following in vivo exposure to peanut or egg allergens in humans.

OBJECTIVES

To examine changes in peripheral blood CD4(+) CD25(+) Foxp3(+) Treg populations (total, activated and naive) in food-allergic, food-sensitized but tolerant, and healthy (non-sensitized non-allergic) patients over time following in vivo allergen exposure.

METHODS

A subset of infants from the HealthNuts study with egg or peanut allergy (n = 37), egg or peanut sensitization (n = 35), or who were non-sensitized non-allergic (n = 15) were studied. All subjects underwent oral food challenge (OFC) to egg or peanut. PBMCs were obtained within 1 h of OFC (in vivo allergen exposure), and Treg populations enumerated ex vivo on day 0, and after 2 and 6 days rest in vitro.

RESULTS

Non-allergic infants showed stable total Treg frequencies over time; food-sensitized infants had a transient fall in Treg percentage with recovery to baseline by day 6 (6.87% day 0, 5.27% day 2, 6.5% day 6); and food-allergic infants showed persistent reduction in Treg (6.85% day 0, 5.4% day 2, 6.2% day 6) following in vivo allergen exposure. Furthermore, food-allergic infants had a significantly lower ratio of activated Treg:activated T cells (10.5 ± 0.77) at day 0 compared to food-sensitized (14.6 ± 1.24) and non-allergic subjects (16.2 ± 1.23).

CONCLUSION

Our data suggest that the state of allergen sensitization is associated with depletion of Treg following allergen exposure. Impaired capacity to regenerate the Treg pool following allergen exposure may be an important factor that determines clinical allergy vs. sensitization without allergic reaction.

Lipopolysaccharides facilitate colonic motor alterations associated to the sensitization to a luminal antigen in rats

Background/Aims

Enteric dysbiosis is a risk factor for dietary proteins-associated intestinal alterations, contributing to the development of food allergies and the symptomatology of functional gastrointestinal disorders, mainly irritable bowel syndrome (IBS). We explored if a dysbiotic-like state, simulated by intraperitoneal administration of bacterial lipopolysaccharides (LPS), facilitates the sensitization to a luminal antigen, ovalbumin (OVA), in rats.

Methods

Rats were exposed to oral OVA for 1 week, alone or with LPS. Thereafter, colonic histology, goblet cell density, mucosal eosinophils and mucosal mast cell (MMC) and connective tissue mast cell (CTMC) were evaluated. Colonic expression (real-time quantitative polymerase chain reaction) of interleukins, IFN-α1 and integrins was assessed to determine local immune responses. Luminal and wall adhered microbiota were characterized by fluorescence in situ hybridization. Colonic contractility (in vitro) served to assess functional changes associated to OVA and/or LPS.

Results

Neither OVA nor LPS, alone or combined, lead to structural alterations, except for a reduced goblet cell density in OVA-LPS-treated rats. MMC density was unaffected, while CTMC counts increased within the submucosa of OVA-LPS-treated animals. Marginal immune activation (IFN-α1 up-regulation) was observed in OVA-LPS-treated rats. LPS induced a dysbiotic-like state characterized by decreased luminal bacterial counts, with a specific loss of clostridia. LPS facilitated Clostridium spp. wall adherence, an effect prevented by OVA. Colonic contractility was altered in OVA-LPS-treated animals, showing increased basal activity and enhanced motor responses to OVA.

Conclusions

Changes in gut microbiota and/or direct effects of LPS might enhance/facilitate local neuroimmune responses to food antigens leading to motor alterations similar to those observed in IBS.

Cohort Profile: The HealthNuts Study: Population prevalence and environmental/genetic predictors of food allergy

HealthNuts is a single-centre, multi-wave, population-based longitudinal study designed to assess prevalence, determinants, natural history and burden of allergy (particularly food allergy) in the early years of life. It is novel in the use of serial food challenge measures within its population frame to confirm food allergy. The cohort comprises 5276 children initially recruited at age 12 months from council-run immunization sessions across Melbourne, Australia. As well as parent-completed questionnaires and researcher-observed eczema status, all infants underwent skin-prick testing to egg, peanut, sesame and either cow's milk or shellfish, and those with detectable wheals underwent food challenges to determine clinical allergy. In wave 2, conducted at age 4 years, validated questionnaires collected data on asthma, allergic rhinitis (hay fever), eczema and food allergies. Food challenges were repeated in children previously identified as food allergic to determine resolution. In wave 3, all children (irrespective of food allergy status) were invited for clinical assessment at age 6 years, including lung function, physical measurements, skin-prick testing to foods and aeroallergens and food challenges if food sensitized. Biological specimens (blood, cheek swabs) were collected at each wave for ancillary immunological, genetic and epigenetic studies. Applications to access data and/or samples can be submitted to [katrina.allen@mcri.edu.au].

The impact of family history of allergy on risk of food allergy: a population-based study of infants

The apparent rapid increase in IgE-mediated food allergy and its implications are now widely recognized, but little is known about the relationship between family history (an indirect measure of genetic risk) and the risk of food allergy. In a population-based study of 5,276 one year old infants (HealthNuts), the prevalence of oral food challenge-confirmed food allergy was measured. Associations between family history of allergic disease and food allergy in infants were examined using multiple logistic regression. Food allergy was diagnosed in 534 infants. Compared to those with no family history of allergic disease, children meeting the current definition of "high risk" for allergic disease (one immediate family member with a history of any allergic disease) showed only a modest increase (OR 1.4, 95% CI 1.1-1.7) in food allergy, while having two or more allergic family members was more strongly predictive of food allergy in the child (OR 1.8, 95% CI 1.5-2.3). There were also differences in the associations between family history and egg and peanut allergy in the child. Re-defining "high risk" as two or more allergic family members may be more useful for identification of groups with a significantly increased risk of food allergy both clinically and within research studies.

The natural history of IgE-mediated food allergy: can skin prick tests and serum-specific IgE predict the resolution of food allergy?

IgE-mediated food allergy is a transient condition for some children, however there are few indices to predict when and in whom food allergy will resolve. Skin prick test (SPT) and serum-specific IgE levels (sIgE) are usually monitored in the management of food allergy and are used to predict the development of tolerance or persistence of food allergy. The aim of this article is to review the published literature that investigated the predictive value of SPT and sIgE in development of tolerance in children with a previous diagnosis of peanut, egg and milk allergy. A systematic search identified twenty-six studies, of which most reported SPT or sIgE thresholds which predicted persistent or resolved allergy. However, results were inconsistent between studies. Previous research was hampered by several limitations including the absence of gold standard test to diagnose food allergy or tolerance, biased samples in retrospective audits and lack of systematic protocols for triggering re-challenges. There is a need for population-based, prospective studies that use the gold standard oral food challenge (OFC) to diagnose food allergy at baseline and follow-up to develop SPT and sIgE thresholds that predict the course of food allergy.