Enhancement of murine IgE antibody detection by IgG removal

Influence of Pore Size in Protein G'-Grafted Mesoporous Silica Nanoparticles as a Serum Pretreatment System for In Vitro Allergy Diagnosis

Particles with the capacity to bind to immunoglobulin G (IgG) can be used for the purification of IgG or to process clinical samples for diagnostic purposes. For in vitro allergy diagnosis, the high IgG levels in serum can interfere with the detection of allergen-specific IgE, the main diagnostic biomarker. Although commercially available, current materials present a low IgG capture capacity at large IgG concentrations or require complex protocols, preventing their use in the clinic. In this work, mesoporous silica nanoparticles are prepared with different pore sizes, to which IgG-binding protein G' is grafted. It is found that for one particular optimal pore size, the IgG capture capacity of the material is greatly enhanced. The capacity of this material to efficiently capture human IgG in a selective way (compared to IgE) is demonstrated in both solutions of known IgG concentrations as well as in complex samples, like serum, from healthy controls and allergic patients using a simple and fast incubation protocol. Interestingly, IgG removal using the best-performing material enhances in vitro IgE detection in sera from patients allergic to amoxicillin. These results highlight the great translation potential of this strategy to the clinic in the context of in vitro allergy diagnosis.

Recombinant multimeric dog allergen prevents airway hyperresponsiveness in a model of asthma marked by vigorous TH 2 and TH 17 cell responses

BACKGROUND

Allergy to dogs affects around 10% of the population in developed countries. Immune therapy of allergic patients with dog allergen extracts has shown limited therapeutic benefit.

METHODS

We established a mouse model of dog allergy by repeatedly administering dog dander and epithelium extracts via the intranasal route. We also assessed the efficacy of a recombinant multimeric protein containing Can f 1, f 2, f 4 and f 6 in preventing inflammatory responses to dog extracts.

RESULTS

Repeated inhalation of dog extracts induced infiltration of the airways by T_H 2 cells, eosinophils and goblet cells, reminiscent of the house dust mite (HDM) model of asthma. Dog extracts also induced robust airway hyperresponsiveness and promoted T_H 17 cell responses, which was associated with a high neutrophilic infiltration of the airways. scRNA-Seq analysis of T helper cells in the airways pinpointed a unique gene signature for T_H 17 cells. Analysis of T-cell receptors depicted a high frequency of clones that were shared between T_H 17, T_H 2 and suppressive Treg cells, indicative of a common differentiation trajectory for these subsets. Importantly, sublingual administration of multimeric Can f 1-2-4-6 protein prior to sensitization reduced airway hyperresponsiveness and type 2-mediated inflammation in this model.

CONCLUSION

Dog allergen extracts induce robust T_H 2 and T_H 17 cell-mediated responses in mice. Recombinant Can f 1-2-4-6 can induce tolerance to complex dog allergen extracts.

Targeted allergen-specific immunotherapy within the skin improves allergen delivery to induce desensitization to peanut

Aim: Epicutaneous immunotherapy (EPIT) with peanut has been demonstrated to be safe but efficacy may be limited by allergen uptake through the skin barrier. To enhance allergen uptake into the skin, the authors used peanut-coated microneedles and compared them with EPIT in a peanut allergy mouse model. Methods: Sensitized mice were treated with peanut-coated microneedles or peanut-EPIT and then challenged with peanut to determine protection. Results: Treatment with peanut-coated microneedles was safe and showed enhanced desensitization to peanut compared with peanut-EPIT administered via a similar schedule. Protection was associated with reduced Th2 immune responses and mast cell accumulation in the intestine. Conclusion: Peanut-coated microneedles have the potential to present a safe method of improving allergen delivery for cutaneous immunotherapy.

Intrinsic and extrinsic regulation of IgE B cell responses

Stringent regulation of IgE antibody production is critical for constraining allergic responses. This review discusses recent advances in understanding cell-intrinsic and extrinsic mechanisms that regulate the genesis and fate of IgE B cells. B cell-intrinsic regulation of IgE is orchestrated by the IgE B Cell Receptor (BCR). Through its antigen-independent signaling and low surface expression, the IgE BCR drives IgE B cells to differentiate into short-lived plasma cells and/or undergo apoptosis, restricting IgE-expressing cells from entering long-lived compartments. The pivotal extrinsic regulators of IgE responses are T follicular helper cells (T_FH). T_FH produce IL-4 and IL-21, which, respectively, are the major activating and inhibitory cytokines for IgE class-switching. Other newly identified T follicular subsets also contribute to IgE regulation. Although IgE responses are normally constrained, recent studies suggest that specific conditions can induce the formation of IgE responses with enhanced affinity or longevity, effectively 'breaking the rules' of IgE regulation.

Isotype-Specific Detection of Serum Immunoglobulins Against Allergens

Type-I hypersensitivity is commonly characterized by increased levels of antigen-specific immunoglobulin (Ig) E. Therefore, it is important for clinical and research investigators to reliably measure serum levels of IgE in allergic patients and animal models. While current ELISA-based methods are simple and commonly performed for the detection of allergen-specific IgE using serum or plasma, they may produce misleading results. This is in part due to decreased sensitivity for IgE in the presence of other Ig isotypes in the same sample, such as IgG, that are typically more abundant than IgE. When assessment of multiple Ig isotypes is necessary, performing optimized assays for individual isotypes requires high sample volumes. Here, we describe an approach to increase the sensitivity for IgE detection while conserving the sample volume needed. This method not only improves the accuracy of serum IgE measurements but also allows simultaneous analysis of other allergen-specific immunoglobulins.

Identification and Physicochemical Characterization of a New Allergen from Ascaris lumbricoides

To analyze the impact of Ascaris lumbricoides infection on the pathogenesis and diagnosis of allergic diseases, new allergens should be identified. We report the identification of a new Ascaris lumbricoides allergen, Asc l 5. The aim of this study was to evaluate the physicochemical and immunological features of the Asc l 5 allergen. We constructed an A. lumbricoides cDNA library and Asc l 5 was identified by immunoscreening. After purification, rAsc l 5 was physicochemically characterized. Evaluation of its allergenic activity included determination of Immunoglobulin E (IgE) binding frequency (in two populations: 254 children and 298 all-age subjects), CD203c based-basophil activation tests (BAT) and a passive cutaneous anaphylaxis (PCA) mouse model. We found by amino acid sequence analysis that Asc l 5 belongs to the SXP/RAL-2 protein family of nematodes. rAsc l 5 is a monomeric protein with an alpha-helical folding. IgE sensitization to rAsc l 5 was around 52% in general population; positive BAT rate was 60%. rAsc l 5 induced specific IgE production in mice and a positive PCA reaction. These results show that Asc l 5 has structural and immunological characteristics to be considered as a new allergen from A. lumbricoides.

Vitamin A deficiency exacerbates extrinsic atopic dermatitis development by potentiating type 2 helper T cell-type inflammation and mast cell activation

BACKGROUND

Vitamin A deficiency (VAD) has been hypothesized to play a role in the pathophysiology of atopic dermatitis (AD).

OBJECTIVE

We sought to verify whether VAD can exacerbate AD development, and explore the possible pathophysiologic mechanism.

METHODS

We detected serum vitamin A (VA) concentration in different phenotypes of AD infants (intrinsic AD, iAD and extrinsic AD, eAD), and established ovalbumin (OVA) percutaneous sensitized AD model and passive cutaneous anaphylaxis (PCA) model on VAD and vitamin A supplementation (VAS) model in wild-type mice (C57BL/6) and established AD model on both normal VA (VAN) and VAD feeding mast cell deficiency mice (ckit^w-sh/w-sh ).

RESULTS

The average serum VA concentration of eAD was significantly lower than that of iAD, as well as healthy controls. In OVA-induced C57BL/6 mouse AD model, compared with VAN group, VAD mice manifested significantly more mast cells accumulation in the skin lesions, more severe Th2-mediated inflammation, including higher serum IgG1 and IgE levels, more IL-4, IL-13 mRNA expression in OVA-sensitized skin, and lower Th1 immune response, including lower serum IgG2a and IFN-γ mRNA expression in the skin. But there was no significant difference in the expression of IL-17 mRNA between OVA-treated skin of VAN and VAD mice. However, in OVA-induced ckit^w-sh/w-sh mouse AD model, we did not find any significant differences in the above measurements between VAD and VAN group. In PCA model, VAD mice showed remarkable more blue dye leakage than that in VAN mice. Compared with VAD group, the above-mentioned inflammatory measurements in VAS group and VAN group were similar in OVA-induced AD model mice.

CONCLUSIONS AND CLINICAL RELEVANCE

VAD can exacerbate extrinsic AD by augmenting Th2-mediated inflammation and mast cell activation. Therapeutic VAS can rescue VAD-aggravated eAD. It may provide a new strategy for future prevention or treatment of atopic dermatitis.

Ascaris lumbricoides Cystatin Prevents Development of Allergic Airway Inflammation in a Mouse Model

Severe helminth infections are negatively associated to allergic diseases like asthma; therefore, the immunomodulatory properties of parasite-derived components have been analyzed, raising the possibility of their use as anti-inflammatory molecules. We evaluated the immunomodulatory properties of Ascaris lumbricoides recombinant cysteine protease inhibitor (rAl-CPI) in a mouse model of allergic airway inflammation induced by the house dust mite (HDM) Blomia tropicalis and its effects on human monocyte-derived dendritic cells (HmoDCs). The B. tropicalis sensitized/challenged mice developed extensive cellular airway inflammatory response, which was significantly reduced upon treatment with rAl-CPI prior to B. tropicalis sensitization, affecting particularly the perivascular/peribronchial infiltrate cells, eosinophils/neutrophils, and goblet cells. A significant decrease of Th2 cytokines, total, and specific IgE antibodies was observed in rAl-CPI treated mice. The antibody response was biased to IgG, mainly IgG2a. Administration of rAl-CPI-alone and rAl-CPI before mite sensitization were associated with a significant increase of regulatory T cells (Tregs) in spleen and elevated IL-10 levels in BAL and splenocytes culture supernatants, which was partially affected by anti-IL10 receptor use. In vitro, rAl-CPI showed a modulatory effect on HmoDCs, lowering the expression of HLA-DR, CD83, and CD86, while inducing IL-10 and IL-6 production. This suggests an inhibition of HmoDC maturation and a possible link with the inhibition of the allergic response observed in the murine model.

Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4+ T Cell- and MyD88-Dependent Pathways in Mice

Tick-borne allergies are a growing public health concern and have been associated with the induction of IgE-mediated food allergy to red meat. However, despite the increasing prevalence of tick bite-induced allergies, the mechanisms by which cutaneous exposure to ticks leads to sensitization and the production of IgE Abs are poorly understood. To address this question, an in vivo approach was used to characterize the IgE response to lone star tick proteins administered through the skin of mice. The results demonstrated that tick sensitization and challenge induced a robust production of IgE Abs and supported a role for IgE-mediated hypersensitivity reactions in sensitized animals following oral administration of meat. The induction of IgE responses was dependent on cognate CD4⁺ T cell help during both the sensitization phase and challenge phase with cutaneous tick exposure. In addition, IgE production was dependent on B cell-intrinsic MyD88 expression, suggesting an important role for TLR signaling in B cells to induce IgE responses to tick proteins. This model of tick-induced IgE responses could be used to study the factors within tick bites that cause allergies and to investigate how sensitization to food Ags occurs through the skin that leads to IgE production.

Oral sensitization to whey proteins induces age- and sex-dependent behavioral abnormality and neuroinflammatory responses in a mouse model of food allergy: a potential role of mast cells

BACKGROUND

Growing evidence has strengthened the association of food allergy with neuropsychiatric symptoms such as depression, anxiety, and autism. However, underlying mechanisms by which peripheral allergic responses lead to behavioral dysfunction are yet to be determined. Allergen-activated mast cells may serve as mediators by releasing histamine and other inflammatory factors that could adversely affect brain function. We hypothesized that eliciting food allergy in experimental animals would result in behavioral changes accompanied by mast cell accumulation in the brain. Our hypothesis was tested in a mouse model of milk allergy using bovine milk whey proteins (WP) as the allergen.

METHODS

Male and female C57BL/6 mice at 4 weeks (young) and 10 months (old) of age underwent 5-week WP sensitization with weekly intragastric administration of 20 mg WP and 10 μg cholera toxin as an adjuvant. Age-matched sham animals were given the vehicle containing only the adjuvant. All animals were orally challenged with 50 mg WP in week 6 and their intrinsic digging behavior was assessed the next day. Animals were sacrificed 3 days after the challenge, and WP-specific serum IgE, intestinal and brain mast cells, glial activation, and epigenetic DNA modification in the brain were examined.

RESULTS

WP-sensitized males showed significantly less digging activity than the sham males in both age groups while no apparent difference was observed in females. Mast cells and their activities were evident in the intestines in an age- and sex-dependent manner. Brain mast cells were predominantly located in the region between the lateral midbrain and medial hippocampus, and their number increased in the WP-sensitized young, but not old, male brains. Noticeable differences in for 5-hydroxymethylcytosine immunoreactivity were observed in WP mice of both age groups in the amygdala, suggesting epigenetic regulation. Increased microglial Iba1 immunoreactivity and perivascular astrocytes hypertrophy were also observed in the WP-sensitized old male mice.

CONCLUSIONS

Our results demonstrated that food allergy induced behavioral abnormality, increases in the number of mast cells, epigenetic DNA modification in the brain, microgliosis, and astrocyte hypertrophy in a sex- and age-dependent manner, providing a potential mechanism by which peripheral allergic responses evoke behavioral dysfunction.

Oocyst-Derived Extract of Toxoplasma Gondii Serves as Potent Immunomodulator in a Mouse Model of Birch Pollen Allergy

Introduction

Previously, we have shown that oral infection with Toxoplasma gondii oocysts prevented type I allergy in mice. Here we investigated whether the application of a T. gondii oocyst lysate antigen (OLA) could also reduce allergy development. BALB/c mice were immunised twice with OLA followed by sensitisation with the major birch pollen (BP) allergen Bet v 1 and an aerosol challenge with BP extract.

Methods

First, we tested OLA in vitro. Stimulation of splenocytes and bone marrow-derived dendritic cells (BMDC) with OLA led to the production of pro-inflammatory and regulatory cytokines such as IL-6, IFN-γ and IL-10. Moreover, BMDC exposed to OLA upregulated the maturation markers CD40, CD80, CD86, and MHCII. Furthermore, OLA was recognised by TLR2-transfected human embryonic kidney cells.

Results

Immunisation of mice with OLA induced high levels of Toxoplasma-specific IgG antibodies in sera along with increased production of IFN-γ and IL-10 in Toxoplasma-antigen restimulated splenocytes. OLA reduced allergic airway inflammation as manifested by significant reduction of eosinophils in bronchoalveolar fluids, decreased cellular infiltrates and mucus production in the lungs. Accordingly, Bet v 1-specific IgE was decreased in OLA-pretreated mice. The reduced allergic immune responses were accompanied by increased numbers of CD4⁺CD25^highFoxp3⁺ regulatory T cells in spleens as well as by increased numbers of granulocytic myeloid-derived suppressor cells in lungs when compared to sensitised controls suggesting that these two cell populations might be involved in the suppression of the allergic immune responses.

Conclusion

Our data demonstrate that pretreatment with the oocyst extract can exert anti-allergic effects comparable to T. gondii infection. Thus, the immunomodulatory properties of the parasite extract indicate that this extract and in the future defined molecules thereof might serve as immunomodulatory adjuvants in allergy treatment and prophylaxis.

Fecal antibody levels as a noninvasive method for measuring immunity to gastrointestinal nematodes in ecological studies

Among‐individual variation in antibody‐associated immunity to gastrointestinal nematode parasites (GIN) is known be associated with life‐history traits and vital rates in wild vertebrate systems. To date, measurement of levels of antibodies against GIN antigens in natural populations has exclusively been based on invasive blood sampling techniques. Previous work in laboratory rodents and ruminant livestock suggests that antibody measures from feces may provide a viable noninvasive approach. We measured total and anti‐GIN antibodies of different isotypes (immunoglobulin (Ig) G, IgA and IgE) from paired samples of plasma and feces from free‐living Soay sheep of different ages and sexes. We tested the correlations among these measures as well as their associations with body mass and Strongyle nematode fecal egg counts (FEC). Significant positive correlations were present among plasma and fecal anti‐GIN antibody levels for IgG and IgA. Generally, correlations between total antibody levels in plasma and feces were weaker and not significant. No significant relationships were found between any antibody measures and body mass; however, fecal anti‐GIN antibody levels were significantly negatively correlated with FEC. Our data clearly demonstrate the feasibility of measuring anti‐GIN antibodies from fecal samples collected in natural populations. Although associations of fecal antibody levels with their plasma counterparts and FEC were relatively weak, the presence of significant correlations in the predicted direction in a relatively small and heterogeneous sample suggests fecal antibody measures could be a useful, noninvasive addition to current eco‐immunological studies.

Functional effects of TGF-β1 on mesenchymal stem cell mobilization in cockroach allergen-induced asthma

Mesenchymal stem cells (MSCs) have been suggested to participate in immune regulation and airway repair/remodeling. TGF-β1 is critical in the recruitment of stem/progenitor cells for tissue repair, remodeling, and cell differentiation. In this study, we sought to investigate the role of TGF-β1 in MSC migration in allergic asthma. We examined nestin expression (a marker for MSCs) and TGF-β1 signaling activation in airways in cockroach allergen extract (CRE)-induced mouse models. Compared with control mice, there were increased nestin(+) cells in airways and higher levels of active TGF-β1 in serum and p-Smad2/3 expression in lungs of CRE-treated mice. Increased activation of TGF-β1 signaling was also found in CRE-treated MSCs. We then assessed MSC migration induced by conditioned medium from CRE-challenged human epithelium in air/liquid interface culture in Transwell assays. MSC migration was stimulated by epithelial-conditioned medium, but was significantly inhibited by either TGF-β1-neutralizing Ab or TβR1 inhibitor. Intriguingly, increased migration of MSCs from blood and bone marrow to the airway was also observed after systemic injection of GFP(+) MSCs and from bone marrow of Nes-GFP mice following CRE challenge. Furthermore, TGF-β1-neutralizing Ab inhibited the CRE-induced MSC recruitment, but promoted airway inflammation. Finally, we investigated the role of MSCs in modulating CRE-induced T cell response and found that MSCs significantly inhibited CRE-induced inflammatory cytokine secretion (IL-4, IL-13, IL-17, and IFN-γ) by CD4(+) T cells. These results suggest that TGF-β1 may be a key promigratory factor in recruiting MSCs to the airways in mouse models of asthma.

Allergome: the characterization of allergens based on a 2D gel electrophoresis approach

Type I hypersensitivity reactions are in constant progression in industrialized countries. The physiopathologic mechanism of these diseases implicates the production of specific immunoglobulin (Ig)E to allergenic molecules, their binding to the Fcepsilon receptor on the surface of mast cells and basophils, and the release of inflammatory mediators when allergens are introduced into the body and crosslink with the IgE bound to the cell surface. An allergen is defined as a molecule that induces the production of, and binds to, IgE. The identification of the allergenic molecules is an important goal to improve diagnosis and treatment of allergy. This characterization aims to extract proteins from the allergenic source, to analyze IgE specificity by immunoblotting and to identify the proteins that bind IgE.

The influence of chitin on the immune response to the house dust mite allergen Blo T 12

BACKGROUND

Information about the biological properties of Blomia tropicalis allergens is scarce. It is predicted that Blo t 12, an allergen with two described isoforms, contains a chitin-binding domain, similar to that found in peritrophins. Th2 adjuvant properties have been described for chitin. Therefore, it is feasible that binding to this carbohydrate influences its allergenicity. We aimed to evaluate the chitin-binding activity of Blo t 12 isoallergens and its effect on airway inflammation and antibody responses in a murine model of allergen sensitization.

METHODS

Chitin-binding assays were conducted with the recombinant isoallergens Blo t 12.0101 and Blo t 12.0102. BALB/c mice were sensitized via i.p. with any of the two isoforms (alone, with chitin or alum) and then challenged intranasally. Methacholine-induced bronchial hyperreactivity was tested by whole-body plethysmography and lung sections were stained with hematoxylin and eosin and periodic-acid Schiff. Total IgE and allergen-specific IgE, IgG1 and IgG2 levels were measured by ELISA.

RESULTS

The two isoforms bound chitin, but Blo t 12.0101 showed a stronger binding capacity. Both isoforms induced total and allergen-specific IgE, airway hyperreactivity, bronchial inflammation and mucus secretion without any adjuvant; however, when administered with chitin, Blo t 12.0101 induced higher total IgE levels. The IgG1/IgG2a ratio was significantly higher in mice immunized with Blo t 12.0101 than those immunized with Blo t 12.0102. As peritrophins, Blo t 12 was detected in mite feces.

CONCLUSIONS

Blo t 12 isoforms are chitin-binding proteins that induce airway inflammation and bronchial hyperreactivity. However, for Blo t 12.0101, chitin reinforces its effects on total IgE production.

Cumulative mitoxantrone-induced haematological and hepatic adverse effects in a subchronic in vivo study

Mitoxantrone (MTX) is an antineoplastic agent that can induce hepato- and haematotoxicity. This work aimed to investigate the occurrence of cumulative early and late MTX-induced hepatic and haematological disturbances in an vivo model. A control group and two groups treated with three cycles of 2.5 mg/kg MTX at days 0, 10 and 20 were formed. One of the treated groups suffered euthanasia on day 22 (MTX22) to evaluate early MTX toxic effects, while the other suffered euthanasia on day 48 (MTX48), to allow the evaluation of MTX late effects. An early immunosuppression with a drop in the IgG levels was observed, causing a slight decrease in the plasma total protein content. The early bone marrow depression was followed by signs of recovery in MTX48. The genotoxic potential of MTX was demonstrated by the presence of several micronuclei in MTX22 leucocytes. Increases in plasma iron and cholesterol levels in the MTX22 rats were observed, while in both groups increases in the unconjugated bilirubin, C4 complement, and decreases in the triglycerides, alanine aminotransferase, alkaline phosphatase and transferrin were found in plasma samples. On MTX 48, the liver histology showed more hepatotoxic signs, the hepatic levels of reduced and oxidized glutathione were increased, and ATP hepatic levels were decreased. However, the hepatic total protein levels were decreased only in the livers of MTX22 group. Results demonstrated the MTX genotoxic effects, haemato- and direct hepatotoxicity. While the haematological toxicity is ameliorated with time, the same was not observed in the hepatic injury.

Detection of Allergen-Specific IgE Antibody Responses

Allergen-specific IgE production is the central event in the pathogenesis of atopic disorders and increases in specific IgE serum antibodies are an indicator of immediate hypersensitivity responses in humans and in animal models of allergy. Consequently, accurate and user-friendly methods are needed to measure serum levels of allergen-specific IgE. This review examines historical and recent developments in in vivo and in vitro methods for the detection of allergen-specific IgE in humans and in animal models. Routinely, in vitro methods such as enzyme-linked immunosorbant assays or radioallergosorbant tests and in vivo methods such as the skin prick test (SPT) for humans and the passive cutaneous anaphylaxis assay (PCA) used in animals are utilized to detect allergen-specific IgE. While in vivo assays are usually more accurate than in vitro assays since they provide a functional readout of IgE activity, they are relatively costly and require considerable expertise. On the other hand in vitro assays are limited by the fact that the amount of allergen-specific serum IgG exceeds IgE antibody by several orders of magnitude, resulting in competition for allergen binding. Consequently, methods that use allergen as a direct capture step are limited by the availability of free allergen binding sites for IgE. In order to circumvent this problem, in vitro methods usually require prior depletion of IgG or use high amounts of allergen in order to facilitate availability of free binding sites for IgE detection. Clearly, these approaches are limited for small sample volumes and allergens that are in short supply. New methods such as protein microarray could potentially overcome this problem by providing high allergen concentrations in a relatively small reaction volume. Currently, in vitro methods are rarely used in isolation for prognosis but are used primarily to complement the information obtained from in vivo assays. With the emergence of new technologies it is conceivable that in vitro assays may in the future replace in vivo assays, however until then in vivo assays remain the gold standard of allergen-specific IgE detection.

Heat-induced structural changes affect OVA-antigen processing and reduce allergic response in mouse model of food allergy

Background and Aims

The egg protein ovalbumin (OVA) belongs to six most frequent food allergens. We investigated how thermal processing influences its ability to induce allergic symptoms and immune responses in mouse model of food allergy.

Methodology/Principal Findings

Effect of increased temperature (70°C and 95°C) on OVA secondary structure was characterized by circular dichroism and by the kinetics of pepsin digestion with subsequent HPLC. BALB/c mice were sensitized intraperitoneally and challenged with repeated gavages of OVA or OVA heated to 70°C (h-OVA). Levels of allergen-specific serum antibodies were determined by ELISA (IgA and IgGs) or by β-hexosaminidase release test (IgE). Specific activities of digestive enzymes were determined in brush border membrane vesicles of jejunal enterocytes. Cytokine production and changes in regulatory T cells in mesenteric lymph nodes and spleen were assessed by ELISA and FACS. Heating of OVA to 70°C caused mild irreversible changes in secondary structure compared to boiling to 95°C (b-OVA), but both OVA treatments led to markedly different digestion kinetics and Tregs induction ability in vitro, compared to native OVA. Heating of OVA significantly decreased clinical symptoms (allergic diarrhea) and immune allergic response on the level of IgE, IL-4, IL-5, IL-13. Furthermore, h-OVA induced lower activities of serum mast cell protease-1 and enterocyte brush border membrane alkaline phosphatase as compared to native OVA. On the other hand h-OVA stimulated higher IgG2a in sera and IFN-γ secretion by splenocytes.

Conclusions

Minor irreversible changes in OVA secondary structure caused by thermal processing changes both its digestion and antigenic epitopes formation, which leads to activation of different T cell subpopulations, induces shift towards Th1 response and ultimately reduces its allergenicity.

Effects of Lactobacillus rhamnosus GG supplementation on cow's milk allergy in a mouse model

BACKGROUND

Cow's milk allergy (CMA) is one of the most prevalent human food-borne allergies, particularly in infants and young children from developed countries. Our study aims to evaluate the effects of Lactobacillus rhamnosus GG (LGG) administration on CMA development using whole cow's milk proteins (CMP) sensitized Balb/C mice by two different sensitization methods.

METHODS

LGG supplemented mice were either sensitized orally with CMP and cholera toxin B-subunit (CTB) as adjuvant, or intraperitoneally (IP) with CMP but without the adjuvant. Mice were then orally challenged with CMP and allergic responses were accessed by monitoring hypersensitivity scores, measuring the levels of CMP-specific immunoglobulins (IgG1, IgG2a and IgG) and total IgE from sera, and cytokines (IL-4 and IFN-γ) from spleen lysates.

RESULTS

Sensitization to CMP was successful only in IP sensitized mice, but not in orally sensitized mice with CMP and CTB. Interestingly, LGG supplementation appeared to have reduced cow's milk allergy (CMA) in the IP group of mice, as indicated by lowered allergic responses.

CONCLUSIONS

Adjuvant-free IP sensitization with CMP was successful in inducing CMA in the Balb/C mice model. LGG supplementation favourably modulated immune reactions by shifting Th2-dominated trends toward Th1-dominated responses in CMP sensitized mice. Our results also suggest that oral sensitization by the co-administration of CMP and CTB, as adjuvant, might not be appropriate to induce CMA in mice.

Neonatal colonization of mice with Lactobacillus plantarum producing the aeroallergen Bet v 1 biases towards Th1 and T-regulatory responses upon systemic sensitization

BACKGROUND

The use of recombinant lactic acid bacteria (LAB) as vehicles for mucosal delivery of recombinant allergens is an attractive concept for antigen-defined allergy prevention/treatment. Interventions with LAB are of increasing interest early in life when immune programming is initiated. Here, we investigated the effect of neonatal colonization with a recombinant LAB producing the major birch pollen allergen Bet v 1 in a murine model of type I allergy.

METHODS

We constructed a recombinant Lactobacillus (L.) plantarum NCIMB8826 strain constitutively producing Bet v 1 to be used for natural mother-to-offspring mono-colonization of germ-free BALB/c mice. Allergen-specific immunomodulatory effects of the colonization on humoral and cellular immune responses were investigated prior and after sensitization to Bet v 1.

RESULTS

Mono-colonization with the Bet v 1 producing L. plantarum induced a Th1-biased immune response at the cellular level, evident in IFN-γ production of splenocytes upon stimulation with Bet v 1. After sensitization with Bet v 1 these mice displayed suppressed IL-4 and IL-5 production in spleen and mesenteric lymph node cell cultures as well as decreased allergen-specific antibody responses (IgG1, IgG2a, and IgE) in sera. This suppression was associated with a significant up-regulation of the regulatory marker Foxp3 at the mRNA level in the spleen cells.

CONCLUSION

Intervention at birth with a live recombinant L. plantarum producing a clinically relevant allergen reduces experimental allergy and might therefore become an effective strategy for early intervention against the onset of allergic diseases.

Enzyme-linked immunosorbent assays with high sensitivity for antigen-specific and total murine IgE: a useful tool for the study of allergies in mouse models

BACKGROUND

In studies on allergies in mouse models, IgE production is an essential parameter to be evaluated. Here, we examine the effect of commercially available immunoreaction enhancer solutions and different blocking reagents in enzyme-linked immunosorbent assay (ELISA) for total or antigen-specific murine IgE in order to improve the assays.

METHODS

Sera from mice immunized with recombinant house dust mite major allergens, Der f 1 and Der p 1, were used for the assays. Total IgE was measured by sandwich ELISA using monoclonal antibodies against murine IgE. Antigen-specific IgE was assayed using allergen-coated plates. Sensitivity or signal intensity in ELISA was compared among conditions differing in the use of enhancer solutions, blocking reagents, or monoclonal antibodies, and incubation time.

RESULTS

Use of enhancer solutions improved the sensitivity of ELISA for total IgE by approximately 30-fold of that using a conventional buffer. A blocking reagent caused more unwanted enhancement of the background signal in blank wells in ELISA for total IgE compared with another blocking reagent, however, improved signal intensity in ELISA for antigen-specific ELISA without significant enhancement of the background signal. Optimal assay conditions were determined.

CONCLUSIONS

Enhancer solutions are effective in improving ELISAs for total and antigen-specific murine IgE. Selection of blocking reagents was important to decrease unwanted enhancement of background signals and was effective in enhancing signals for positive samples. The ELISAs improved in this study are useful for the study of allergies in mouse models.

Th1 and Th2 cells are required for both eosinophil- and neutrophil-associated airway inflammatory responses in mice

Most current animal models focus on eosinophil-mediated asthma, despite compelling evidence that a neutrophil-mediated disease occurs in some asthma patients. Using intranasal challenge of mice sensitized either orally or nasally with whole peanut protein extract in the presence of cholera toxin, we developed mouse models of eosinophil- and neutrophil-mediated asthma, respectively. In this study, mice deficient in Th1 (IL-12 and IFN-gamma) or Th2 (IL-4 and IL-13) pathways were used to characterize the role played by Th1 and Th2 cytokines during the initial priming phase in the two models. Antigen-specific Ab responses were controlled primarily by Th2 cytokines in mice sensitized by the oral route, whereas Th1 cytokines appeared to play a predominant role in mice sensitized by the nasal route. Furthermore, the absence of key Th1 or Th2 cytokines during the initial phase of priming reduced lung reactivity in both mouse models of airway inflammation.

Application of Immunoreaction Enhancer Solutions to an Enzyme-Linked Immunosorbent Assay for Antigen-Specific IgE in Mice Immunized with Recombinant Major Mite Allergens or Ovalbumin

BACKGROUND

Weak signals for allergen-specific IgE are a problem in murine models for the study of allergies. It has been reported that the removal of IgG from murine sera enhances signal intensity. Very recently, buffer solutions designed to enhance signals in immunoassays have been developed and made commercially available.

METHODS

Sera from mice immunized either with a recombinant form of one of the major mite allergens Der p 1, Der f 1 and Der f 2, or with ovalbumin adsorbed to alum were used for the assays. Total IgE was measured by a sandwich enzyme-linked immunosorbent assay (ELISA). Allergen-specific IgE was assayed using plates coated with the allergens after the removal of IgG from sera with protein G-coupled sepharose beads in wells of other plates or with the use of commercially available enhancer solutions without the removal of IgG. IgE binding was detected with horseradish peroxidase-conjugated anti-murine IgE monoclonal antibody as the secondary antibody.

RESULTS

Significant levels of total IgE were produced after the immunizations. The in-well pretreatment of diluted sera (1/10 dilution) with protein G-coupled beads enhanced the signals for allergen-specific IgE. The use of the enhancer solutions for dilution of the sera and secondary antibody and prolonged incubation remarkably enhanced the signals at a more extensive dilution of sera (1/200 or less) without the removal of IgG.

CONCLUSIONS

An ELISA simply modified with the use of immunoreaction enhancer solutions has advantages in terms of signal intensity and ease of handling for the detection of allergen-specific murine IgE and would be useful for the study of allergies with murine models.

Oral and nasal sensitization promote distinct immune responses and lung reactivity in a mouse model of peanut allergy

Despite structural and functional differences between the initial sites of contact with allergens in the gastrointestinal and nasal tracts, few animal models have examined the influence of the mucosal routes of sensitization on host reactivity to food or environmental antigens. We compared the oral and nasal routes of peanut sensitization for the development of a mouse model of allergy. Mice were sensitized by administration of peanut proteins in the presence of cholera toxin as adjuvant. Antibody and cytokine responses were characterized, as well as airway reactivity to nasal challenge with peanut or unrelated antigens. Oral sensitization promoted higher levels of IgE, but lower IgG responses, than nasal sensitization. Both orally and nasally sensitized mice experienced airway hyperreactivity on nasal peanut challenge. The peanut challenge also induced lung eosinophilia and type 2 helper T-cell-type cytokines in orally sensitized mice. In contrast, peanut challenge in nasally sensitized mice promoted neutrophilia and higher levels of lung MAC-1(+) I-A(b low) cells and inflammatory cytokines. In addition, nasal but not oral, sensitization promoted lung inflammatory responses to unrelated antigens. In summary, both oral and nasal peanut sensitization prime mice for airway hyperreactivity, but the initial mucosal route of sensitization influences the nature of lung inflammatory responses to peanut and unrelated allergens.