An oral sensitization model in Brown Norway rats to screen for potential allergenicity of food proteins.

We developed an oral sensitization protocol for food proteins for the rat. Young Brown Norway (BN) rats were exposed to 1 mg ovalbumin (OVA) by daily gavage dosing for 42 days without the use of an adjuvant. OVA-specific IgE and IgG responses were determined by ELISA. On an oral challenge with OVA some clinical symptoms of food allergy-like effects on the respiratory system, blood pressure, and permeability of the gastrointestinal barrier were studied. In addition, BN rats were orally exposed to a total hen egg white protein (HEW) extract and cow's milk (CM) and the specificities of induced antibody responses were compared with the specificities of antibodies in sera from egg- and milk-allergic patients using immunoblotting. Animals orally exposed to the allergens developed specific IgE and IgG antibodies which recognized the same proteins compared with antibodies from egg- or CM-allergic patients. Among the various clinical symptoms of food allergy, gut permeability was increased after an oral challenge. In addition, some animals demonstrated a temporary decrease in breathing frequency or systolic blood pressure. The results obtained show that the Brown Norway rat is a suitable animal model for inducing specific IgG and IgE responses on daily intragastric dosing of OVA without the use of an adjuvant. Moreover, local immune-mediated effects on oral challenge are observed. The observation that enterally exposed BN rats and food-allergic patients demonstrate antibody responses to a comparable selection of proteins on exposure to different protein mixtures (HEW and CM) further supports the suitability of the BN rat as an animal model for food allergy research and for the study of the allergenicity of (novel) food proteins.     

Allergen-independent maternal transmission of asthma susceptibility

Maternal asthma is a risk factor for development of asthma in children, but mechanisms remain unclear. Offspring of asthmatic mother mice (sensitized and repeatedly exposed to OVA Ag) showed airway hyperresponsiveness and allergic pulmonary inflammation after an intentionally suboptimal OVA sensitization and exposure protocol that had little effect on normal offspring. Similar results were obtained when offspring of OVA-allergic mothers were exposed to an unrelated allergen, casein, indicating that the maternal effect is allergen independent and not transferred by OVA-specific Abs. Premating treatment with neutralizing anti-IL-4 Ab or reduction of maternal allergen exposure abrogated the maternal effect, showing a critical mechanistic role for IL-4 and suggesting an additional benefit of allergen avoidance.     

The importance of dietary control in the development of a peanut allergy model in Brown Norway rats

This report describes the further development of a peanut allergy model in Brown Norway (BN) rats and in particular the importance of allergen-free breeding of the laboratory animals for the allergen to be used. For this purpose BN rats were bred for 3 generations on soy- and peanut-free feed since it is known that the legumes peanut and soy are cross-reactive. In addition, the effect of cholera toxin (CT), an oral adjuvant often used to increase the sensitivity of food allergy models, was investigated in the BN rat model. BN rats that were bred on both soy- and peanut-free feed could be sensitized orally to peanut (all exposed rats developed peanut-specific IgE, IgG2a and IgG1) and the adjuvant CT could only enhance this sensitization to a limited extent. We also found different protein recognition patterns against purified peanut allergens (Ara h1, Ara h2 and Ara h3) between intraperitoneally (i.p.) and orally sensitized BN rats. Orally sensitized rats recognized all tested allergens whereas i.p. sensitized rats only recognized Ara h1 and Ara h2. Our conclusion is that a model for food allergy should preferably be (A) oral and (B) if possible without the use of adjuvantia. Our model in BN rats unites these preferred characteristics. In addition, we show the importance of dietary control when conducting oral sensitization studies. Special attention must be paid to unscheduled dietary pre-exposure of the animals to the protein under investigation to obtain optimal oral sensitization.     

Critical role of preconceptional immunization for protective and nonpathological specific immunity in murine neonates

Expression of Th2 immunity against environmental Ags is the hallmark of the allergic phenotype and contrasts with the Th1-like pattern, which is stably expressed in healthy adults throughout life. Epidemiological studies indicate that the prenatal environment plays an important and decisive role in the development of allergy later in life. Since the underlying mechanisms were unclear, an animal model was developed to study the impact of maternal allergy on the development of an allergic immune response in early life. An allergic Th2 response was induced in pregnant mice by sensitization and aerosol allergen exposure. Both, IgG1 and IgG2a, but not IgE, Abs cross the placental barrier. Free allergen also crosses the placental area and was detected in serum and amniotic fluids of neonatal F(1) mice. These F(1) mice demonstrated a suppressed Th1 response, as reflected by lowered frequencies and reduced levels of IFN-gamma production. Development of an IgE response against the same allergen was completely prevented early in life. This effect was mediated by diaplacental transfer of allergen-specific IgG1 Abs. In contrast, allergic sensitization against a different allergen early in life was accelerated in these mice. This effect was mediated by maternal CD4 and OVA-specific Th2 cells induced by allergic sensitization during pregnancy. These data indicate a critical role for maternal T and B cell response in shaping pre- and postnatal maturation of specific immunity to allergens.     

Induction of IgE-secreting cells and IgE isotype-specific suppressor T cells in the respiratory lymph nodes of rats in response to antigen inhalation

Repeated exposure of high-IgE-responder Brown Norway (BN) rats to an aerosol of ovalbumin (OVA) once weekly triggered progressively increasing levels of OVA-specific IgG in serum. In contrast, responses in the IgE class were transient, declining from peak titers during the third week to background levels by Week 5, despite continuing aerosol exposure. Subsequent parenteral challenge of these animals revealed a state of antigen- and IgE isotype-specific tolerance. Adoptive transfer of splenocytes or pooled respiratory tract lymph node (RTLN) cells from aerosol-exposed animals to naive rats abrogated subsequent OVA-specific primary IgE responses in the recipients, but did not affect specific IgG responses, and kinetic studies indicated that these suppressor cells arose first in the RTLN. Transfer studies employing individual lymph node groups which constituted the RTLN pool pinpointed the superficial cervical nodes, which drain the uppermost portion of the respiratory tract, as the major source of suppressor cells. Fractionation of cell populations before adoptive transfer employing monoclonal antibodies directed against T-cell markers, defined a population of suppressor cells generated by aerosol exposure which expressed both the W3/13 (pan T-cell) and OX8 (cytotoxic/suppressor T-cell) antigens, but which was negative for the W3/25 (helper T-cell) marker. Analysis of the IgE and IgG responses induced by OVA inhalation was performed employing the ELISA plaque technique, recently developed in this laboratory. These studies revealed the parathymic and posterior mediastinal nodes draining the lower lung, as the major sites of specific IgE and IgG production; smaller numbers of OVA-specific IgG-secreting cells (but none secreting specific IgE) were detected in the nodes draining the upper respiratory tract, while antibody secretion outside the respiratory tract was restricted to comparatively few cells in the spleen. The ELISA plaque assay was also employed to enumerate total numbers of cells secreting the IgE isotype in aerosol-exposed and control rats, employing samples from 10 different lymphoid organs. Approximately 50% of the IgE-secreting cells in these animals were localized in RTLN, as opposed to 25% in gut-associated lymphoid tissues. These data are discussed in relation to the pivotal role of respiratory-tract associated lymphoid tissues in regulation of IgE responses to aeroallergens.     

Oral tolerance revisited: prior oral tolerization abrogates cholera toxin-induced mucosal IgA responses

Oral delivery of a large dose or prolonged feeding of protein Ags induce systemic unresponsiveness most often characterized as reduced IgG and IgE Ab- and Ag-specific CD4(+) T cell responses. It remains controversial whether oral tolerance extends to diminished mucosal IgA responses in the gastrointestinal tract. To address this issue, mice were given a high oral dose of OVA or PBS and then orally immunized with OVA and cholera toxin as mucosal adjuvant, and both systemic and mucosal immune responses were assessed. OVA-specific serum IgG and IgA and mucosal IgA Ab levels were markedly reduced in mice given OVA orally compared with mice fed PBS. Furthermore, when OVA-specific Ab-forming cells (AFCs) in both systemic and mucosa-associated tissues were examined, IgG AFCs in the spleen and IgA AFCs in the gastrointestinal tract lamina propria of mice given OVA orally were dramatically decreased. Furthermore, marked reductions in OVA-specific CD4(+) T cell proliferative and cytokine responses in spleen and Peyer's patches were seen in mice given oral OVA but were unaffected in PBS-fed mice. We conclude that high oral doses of protein induce both mucosal and systemic unresponsiveness and that use of mucosal adjuvants that induce both parenteral and mucosal immunity may be a better way to assess oral tolerance.     

Development and Characterization of an Effective Food Allergy Model in Brown Norway Rats

Background

Food allergy (FA) is an adverse health effect produced by the exposure to a given food. Currently, there is no optimal animal model of FA for the screening of immunotherapies or for testing the allergenicity of new foods.

Objective

The aim of the present study was to develop an effective and rapid model of FA in Brown Norway rats. In order to establish biomarkers of FA in rat, we compared the immune response and the anaphylactic shock obtained in this model with those achieved with only intraperitoneal immunization.

Methods

Rats received an intraperitoneal injection of ovalbumin (OVA) with alum and toxin from Bordetella pertussis, and 14 days later, OVA by oral route daily for three weeks (FA group). A group of rats receiving only the i.p. injection (IP group) were also tested. Serum anti-OVA IgE, IgG1, IgG2a, IgG2b and IgA antibodies were quantified throughout the study. After an oral challenge, body temperature, intestinal permeability, motor activity, and mast cell protease II (RMCP-II) levels were determined. At the end of the study, anti-OVA intestinal IgA, spleen cytokine production, lymphocyte composition of Peyer’s patches and mesenteric lymph nodes, and gene expression in the small intestine were quantified.

Results

Serum OVA-specific IgG1, IgG2a and IgG2b concentrations rose with the i.p. immunization but were highly augmented after the oral OVA administration. Anti-OVA IgE increased twofold during the first week of oral OVA gavage. The anaphylaxis in both IP and FA groups decreased body temperature and motor activity, whereas intestinal permeability increased. Interestingly, the FA group showed a much higher RMCP II serum protein and intestinal mRNA expression.

Conclusions

These results show both an effective and relatively rapid model of FA assessed by means of specific antibody titres and the high production of RMCP-II and its intestinal gene expression.     

Respiratory infection with influenza A virus interferes with the induction of tolerance to aeroallergens

Viral respiratory infections have been implicated in influencing allergen sensitization and the development of asthma, but their exact role remains controversial. Because respiratory exposure to Ag normally engenders T cell tolerance and prevents the development of airway hyperreactivity (AHR) and inflammation, we examined the effects of influenza A virus infection on tolerance induced by exposure to intranasal (i.n.) OVA and the subsequent development of AHR. We found that concurrent infection with influenza A abrogated tolerance induced by exposure to i.n. OVA, and instead led to the development of AHR accompanied by the production of OVA-specific IgE, IL-4, IL-5, IL-13, and IFN-gamma. When both IL-4 and IL-5 were neutralized in this system, AHR was still induced, suggesting that influenza-induced cytokines such as IL-13, or mechanisms unrelated to cytokines, might be responsible for the development of AHR. The length of time between influenza A infection and i.n. exposure to OVA was crucial, because mice exposed to i.n. OVA 15-30 days after viral inoculation developed neither AHR nor OVA-specific tolerance. These mice instead acquired Th1-biased OVA-specific immune responses associated with vigorous OVA-induced T cell proliferation, and reduced production of OVA-specific IgE. The protective effect of influenza A on AHR was dependent on IFN-gamma, because protection was abrogated with a neutralizing anti-IFN-gamma mAb. These results suggest that viral respiratory infection interferes with the development of respiratory allergen-induced tolerance, and that the time interval between viral infection and allergen exposure is critical in determining whether viral infection will enhance, or protect against, the development of respiratory allergen sensitization and AHR.     

Tissue-specific effects of allergic rhinitis in mouse nasal epithelia

Allergic rhinitis (AR) can cause significant olfactory loss, but few studies have specifically investigated AR effects on olfactory and nasal respiratory tissues per se. To address this, we used a murine AR protocol employing nasal allergen infusion for both sensitization and challenges. Seven- to 11-week BALB/c mice were bilaterally infused with 1% ovalbumin (OVA) in phosphate-buffered saline (PBS) or PBS alone for 6 or 11 weeks, given single bilateral PBS or OVA infusions 24 h before sacrifice, or left untreated. High OVA-specific IgE serum levels and eosinophil infiltration confirmed AR induction. Olfactory (OE) and respiratory (RE) epithelia showed distinctly different responses, most conspicuously, massive eosinophil infiltration of immediately RE-subjacent lamina propria. In OE, such infiltration was minimal. Significant RE hypertrophy and hyperplasia also occurred, although OE organization was generally maintained and extensive disruption localized despite a 20% reduction in sensory neurons and globose basal cells after 11 weeks OVA. Pronounced Bowman's gland hypertrophy crowded both OE and olfactory nerve bundles. Cellular proliferation was widely distributed in RE but in OE was localized to normally thinner OE and RE-proximal OE, suggesting possible indirect RE influences. Terminal deoxynucleotide transferase (TdT) nick end labeling was greater in OE than RE and, in contrast to other effects, occurred with acute infusions and chronic PBS alone, often unilaterally. Following chronic OVA, AR-related bilateral increases appeared superimposed on those. These findings indicate AR effects on olfactory function may be complex, reflecting various levels of RE/OE responses and interactions.     

Nitrogen dioxide promotes allergic sensitization to inhaled antigen

Allergen sensitization and allergic airway disease are likely to come about through the inhalation of Ag with immunostimulatory molecules. However, environmental pollutants, including nitrogen dioxide (NO2), may promote adaptive immune responses to innocuous Ags that are not by themselves immunostimulatory. We tested in C57BL/6 mice whether exposure to NO2, followed by inhalation of the innocuous protein Ag, OVA, would result in allergen sensitization and the subsequent development of allergic airway disease. Following challenge with aerosolized OVA alone, mice previously exposed via inhalation to NO2 and OVA developed eosinophilic inflammation and mucus cell metaplasia in the lungs, as well as OVA-specific IgE and IgG1, and Th2-type cytokine responses. One hour of exposure to 10 parts per million NO2 increased bronchoalveolar lavage fluid levels of total protein, lactate dehydrogenase activity, and heat shock protein 70; promoted the activation of NF-kappaB by airway epithelial cells; and stimulated the subsequent allergic response to Ag challenge. Furthermore, features of allergic airway disease were not induced in allergen-challenged TLR2-/- and MyD88-/- mice exposed to NO2 and aerosolized OVA during sensitization. These findings offer a mechanism whereby allergen sensitization and asthma may result under conditions of high ambient or endogenous NO2 levels.     

Timing of Bifidobacterium Administration Influences the Development of Allergy to Ovalbumin in Mice

C3H/HeJ mice were sensitized with ovalbumin (OVA) and choleratoxin (CT) for 5 weeks, and then Bifidobacterium bifidum BGN4 was administered continuously for 7 weeks, starting 2 weeks before (pre-treatment group) and 2 weeks after (post-treatment group) the initial sensitization. After sensitization, the OVA-induced (sham group) mice showed growth inhibition and had scab-covered tails which was associated with serum levels of 9887±175 ng OVA-specific IgE/ml and 758±525 ng IgG1/ml. The sera of the pre-treatment group had 4805±245 ng OVA-specific IgE/ml and 193±87 ng IgG1/ml, as well as less severe tail symptoms. The sera of the post-treatment group had 5723±207 ng OVA-specific IgE/ml but the IgG1 and IgG2a levels were the same as those of the sham group. In spleen cultures, both pre-treatment and post-treatment increased the levels of IFN-γ but decreased the levels of IL-6 and IL-18. Taken together, the in vivo and in vitro results show that treatment with Bifidobacterium before OVA sensitization suppresses or modulates the allergic response more effectively than treatment with Bifidobacterium following OVA sensitization.     

Secondhand smoke induces allergic sensitization in mice

Epidemiological studies have suggested increased prevalence of atopy in children of maternal smokers. Although secondhand smoke or environmental tobacco smoke (ETS) has been shown to augment allergic responses, its role in atopic sensitization is still controversial. We studied whether ETS could initiate a Th2 response and thus induce primary allergic sensitization. Mice were exposed for 10 consecutive days to either 1% aerosolized OVA, ETS (5 cigarettes), or both ETS and OVA. C57BL/6 mice receiving both ETS and OVA developed OVA-specific IgE and IgG1, 12, 14, and 25 days after the initial exposure, whereas those receiving OVA alone did not. Thirty days after the initial challenge (20 days after its completion), mice were re-exposed to OVA. Bronchoalveolar lavage performed 24 h later revealed an influx of eosinophils in the group initially challenged with both ETS and OVA, but not in those exposed to ETS alone or OVA alone. Increases in IL-5, GM-CSF, and IL-2 were observed in bronchoalveolar lavage from this OVA/ETS-exposed group, whereas IFN-gamma levels were significantly inhibited. These results suggest that ETS can induce allergic sensitization to a normally harmless Ag, and they may explain why secondhand smoke is a major risk factor for the development of allergy in children.     

不同浓度卵蛋白变应原对小鼠哮喘模型建立的影响

目的研究不同浓度卵蛋白(ovalbumin,OVA)变应原对小鼠的哮喘造模影响。方法 96只6～8周龄SPF级雌性BALB/c小鼠随机分为8组,分别为PBS组(对照组)、10μg组(A组)、20μg组(B组)、50μg组(C组)、100μg组(D组)、200μg组(E组)、500μg组(F组)、1000μg组(G组)。A～G组分别用含1%明矾的PBS配制相应浓度的OVA于第0、7和第14天对小鼠进行腹腔注射。于第21～27天连续7 d用含1%的OVA的PBS溶液雾化吸入激发各组小鼠。正常对照组使用PBS溶液致敏和激发。最后一次雾化吸入激发后24 h内,计数各组小鼠支气管肺泡灌洗液(BLAF)中嗜酸性粒细胞的含量,ELISA法检测IL-4、IL-5的分泌量及其血清IgG2a、IgE抗体的水平;肺组织病理切片观察各组小鼠哮喘模型的效果,评价最优哮喘造模的OVA浓度。结果 A～G组小鼠肺泡灌洗液中IL-4、IL-5含量均高于正常对照组(P<0.01),细胞因子水平随着OVA浓度的增高而逐渐下降;A～G组小鼠肺泡灌洗液中嗜酸性粒细胞数均高于正常对照组(P<0.01),从低浓度组至高浓度组嗜酸性粒细胞数从高向低变化;A～G组小鼠血清中总抗体IgE的水平均显著高于正常对照组(P<0.01),且随着OVA浓度的增高IgE水平逐渐下降。血清中IgG2a的水平则随OVA给药浓度的增高而逐渐增高;低浓度OVA致敏组小鼠肺组织标本可观察到明显的炎症浸润性病理表现,而高浓度组肺部组织病理变化不明显。结论低浓度的OVA连续致敏小鼠造成过敏性哮喘病理改变较为明显,随着OVA浓度的增高,造模效果逐渐降低,而高浓度的OVA则会导致模型小鼠发生免疫耐受。     

Cell cycle block in anergic T cells during tolerance induction

The induction of anergy, or T cell unresponsiveness to antigen, is preceded by T cell activation and cell division in response to fed antigens. These events parallel the activation observed in T cells following sensitization with antigen and adjuvant. The events that distinguish eventual sensitization versus tolerance remain unclear. Using a T lymphocyte transfer model specific to OVA, we demonstrated previously that oral encounter with antigen leads to functional anergy. Antigen-specific CD4+ T cells nevertheless become activated and cycle briefly after encounter with antigen. In this study, we measured the extent of cell cycling of antigen-specific T cells after oral encounter with their antigen. Whereas T cells cycle on the average of eight times in 4 days after conventional immunization, an abortive proliferation was observed in the draining LN T cells after oral encounter with antigen; OVA-specific T cells divided fewer times after exposure to fed OVA, compared to T cells in mice immunized with OVA. This abortive proliferation is antigen specific and not due to bystander suppression, as coadministration of an unrelated antigen that was previously used as a tolerogen does not alter the degree of abortive proliferation. Measurement of BrdU incorporation in mice that were previously fed ovalbumin indicates that up to 3 days following feeding, OVA-specific cells are actively cycling in vivo. However, by day 4, they have stopped cycling while identical T cells in OVA-sensitized mice continue to cycle. Our results indicate either that tolerance is a default pathway and a secondary stimulus is required at day 3 to progress to sensitization, or that elements that limit cell cycle progression are provided for tolerance induction.     

Effet of Combined Nitrogen Dioxide and Carbon Nanoparticle Exposure on Lung Function During Ovalbumin Sensitization in Brown Norway Rat

The interaction of particulate and gaseous pollutants in their effects on the severity of allergic inflammation and airway responsiveness are not well understood. We assessed the effect of exposure to NO₂ in the presence or absence of repetitive treatment with carbon nanoparticle (CNP) during allergen sensitization and challenges in Borwn-Norway (BN) rat, in order to assess their interactions on lung function and airway responses (AR) to allergen and methacholine (MCH), end-expiratory lung volume (EELV), bronchoalveolar lavage fluid (BALF) cellular content, serum and BALF cytokine levels and histological changes. Animals were divided into the following groups (n = 6): Control; CNP (Degussa-FW2): 13 nm, 0.5 mg/kg instilled intratracheally ×3 at 7-day intervals; OVA: ovalbumin-sensitised; OVA+CNP: both sensitized and exposed to CNP. Rats were divided into equal groups exposed either to air or to NO₂, 10 ppm, 6 h/d, 5d/wk for 4 weeks. Exposure to NO₂, significantly enhanced lung inflammation and airway reactivity, with a significantly larger effect in animals sensitized to allergen, which was related to a higher expression of TH1 and TH2-type cytokines. Conversely, exposure to NO₂ in animals undergoing repeated tracheal instillation of CNP alone, increased BALF neutrophilia and enhanced the expression of TH1 cytokines: TNF-α and IFN-γ, but did not show an additive effect on airway reactivity in comparison to NO₂ alone. The exposure to NO₂ combined with CNP treatment and allergen sensitization however, unexpectedly resulted in a significant decrease in both airway reactivity to allergen and to methacholine, and a reduction in TH2-type cytokines compared to allergen sensitization alone. EELV was significantly reduced with sensitization, CNP treatment or both. These data suggest an immunomodulatory effect of repeated tracheal instillation of CNP on the proinflammatory effects of NO₂ exposure in sensitized BN rat. Furthermore, our findings suggest that NO₂, CNP and OVA sensitization may significantly slow overall lung growth in parenchymally mature animals.     

Allergen-Specific Immunotherapy with Monomeric Allergoid in a Mouse Model of Atopic Dermatitis

Atopic dermatitis (AD) is a widespread and difficult to treat allergic skin disease and is a tough challenge for healthcare. In this study, we investigated whether allergen-specific immunotherapy (ASIT) with a monomeric allergoid obtained by succinylation of ovalbumin (sOVA) is effective in a mouse model of atopic dermatitis. An experimental model of AD was reproduced by epicutaneous sensitization with ovalbumin (OVA). ASIT was performed with subcutaneous (SC) administration of increasing doses of OVA or sOVA. The levels of anti-OVA antibodies, as well as cytokines, were detected by ELISA. Skin samples from patch areas were taken for histologic examination. ASIT with either OVA or sOVA resulted in a reduction of both the anti-OVA IgE level and the IgG1/IgG2a ratio. Moreover, ASIT with sOVA increased the IFN-γ level in supernatants after splenocyte stimulation with OVA. Histologic analysis of skin samples from the sites of allergen application showed that ASIT improved the histologic picture by decreasing allergic inflammation in comparison with untreated mice. These data suggest that ASIT with a succinylated allergen represents promising approach for the treatment of AD.     

Oral-tolerance induction in diet-induced obese mice

OBJECTIVE: It is known that immune functions are altered in various ways by obesity. However, changes in the intestinal immune system resulting from obesity remain poorly understood. Oral tolerance is a system that suppresses antigen specific immune responses to orally administrated antigens. The intestinal immune system is intimately associated with the oral tolerance system, that acts to prevent allergic and inflammatory diseases. In this study we investigated the effect of obesity on induction of oral tolerance to ovalbumin (OVA) in an animal model of obesity. RESEARCH METHODS AND PROCEDURES: Obese mice induced by a high fat diet and control mice were allowed free access for 3 days to a 1%-ovalbumin (OVA) solution in drinking water. After continuous feeding of the antigen, all the mice were immunized by two intraperitoneal injections of OVA administered 7 days apart. RESULTS: In the control mice, induction of oral tolerance caused an increase in antigen specific IgG1 levels and a decrease in IgG2a levels. In contrast, the IgG1/IgG2a ratio was reversed in obese mice. OVA-specific IL-2 production was suppressed by antigen feeding in both the control and obese mice; however, suppression of OVA-specific IL-10 was observed only in the control mice. Although OVA-specific IgA and IgM were not affected by antigen feeding, the obese groups of mice had significantly lower titers of antibodies. DISCUSSION: These findings suggest that obesity may affect induction of oral tolerance following antigen feeding and that these changes may be related to the inflammatory reaction.     

Unlipidated Outer Membrane Protein Omp16 (U-Omp16) from Brucella spp. as Nasal Adjuvant Induces a Th1 Immune Response and Modulates the Th2 Allergic Response to Cow’s Milk Proteins

The discovery of novel mucosal adjuvants will help to develop new formulations to control infectious and allergic diseases. In this work we demonstrate that U-Omp16 from Brucella spp. delivered by the nasal route (i.n.) induced an inflammatory immune response in bronchoalveolar lavage (BAL) and lung tissues. Nasal co-administration of U-Omp16 with the model antigen (Ag) ovalbumin (OVA) increased the amount of Ag in lung tissues and induced OVA-specific systemic IgG and T helper (Th) 1 immune responses. The usefulness of U-Omp16 was also assessed in a mouse model of food allergy. U-Omp16 i.n. administration during sensitization ameliorated the hypersensitivity responses of sensitized mice upon oral exposure to Cow’s Milk Protein (CMP), decreased clinical signs, reduced anti-CMP IgE serum antibodies and modulated the Th2 response in favor of Th1 immunity. Thus, U-Omp16 could be used as a broad Th1 mucosal adjuvant for different Ag formulations.     

Proteinase-activated receptor-2 promotes allergic sensitization to an inhaled antigen through a TNF-mediated pathway

The reason why particular inhaled Ags induce allergic sensitization while others lead to immune tolerance is unclear. Along with a genetic predisposition to atopy, intrinsic characteristics of these Ags must be important. A common characteristic of many allergens is that they either possess proteinase activity or are inhaled in particles rich in proteinases. Many allergens, such as house dust mite and cockroach allergens, have the potential to activate the proteinase-activated receptor (PAR)-2. In this study, we report that PAR-2 activation in the airways at the same time as exposure to inhaled Ags induces allergic sensitization, whereas exposure to Ag alone induces tolerance. BALB/c mice were administered OVA with a PAR-2 activating peptide intranasally. Upon allergen re-exposure mice developed airway inflammation and airway hyperresponsiveness, as well as OVA-specific T cells with a Th2 cytokine profile when restimulated with OVA in vitro. Conversely, mice given OVA alone or OVA with a PAR-2 control peptide developed tolerance. These tolerant mice did not develop airway inflammation or airway hyperresponsiveness, and developed OVA-specific T cells that secreted high levels of IL-10 when restimulated with OVA in vitro. Furthermore, pulmonary dendritic cell trafficking was altered in mice following intranasal PAR-2 activation. Finally, we showed that PAR-2-mediated allergic sensitization was TNF-dependent. Thus, PAR-2 activation in the airways could be a critical factor in the development of allergic sensitization following mucosal exposure to allergens with serine proteinase activity. Interfering with this pathway may prove to be useful for the prevention or treatment of allergic diseases.     

Role of Maternal Dietary Peanut Exposure in Development of Food Allergy and Oral Tolerance

Background

The impact of maternal ingestion of peanut during pregnancy and lactation on an offspring’s risk for peanut allergy is under debate.

Objective

To investigate the influence of maternal dietary peanut exposure and breast milk on an offspring’s allergy risk.

Methods

Preconceptionally peanut-exposed C3H/HeJ females were either fed or not fed peanut during pregnancy and lactation. The offsprings’ responses to peanut sensitization or oral tolerance induction by feeding antigen prior to immunization were assessed. We also assessed the impact of immune murine milk on tolerance induction pre- or post-weaning. For antigen uptake studies, mice were gavaged with fluorescent peanut in the presence or absence of immune murine milk; Peyer’s patches were harvested for immunostaining.

Results

Preconceptional peanut exposure resulted in the production of varying levels of maternal antibodies in serum (and breast milk), which were transferred to the offspring. Despite this, maternal peanut exposure either preconceptionally or during pregnancy and lactation, when compared to no maternal exposure, had no impact on peanut allergy. When offspring were fed peanut directly, dose-dependent tolerance induction, unaltered by maternal feeding of peanut, was seen. Although peanut uptake into the gut-associated lymphoid tissues was enhanced by immune milk as compared to naïve milk, tolerance induction was not affected by the co-administration of immune milk either pre- or post-weaning.

Conclusion

Maternal peanut exposure during pregnancy and lactation has no impact on the development of peanut allergy in the offspring. Tolerance to peanut can be induced early, even pre-weaning, by giving moderate amounts of peanut directly to the infant, and this is neither enhanced nor impaired by concurrent exposure to immune milk.