Divergent antibody isotype responses induced in mice by systemic exposure to proteins: a comparison of ovalbumin with bovine serum albumin

Design Principles for Immunomodulatory Biomaterials

The immune system is imperative to the survival of all biological organisms. A functional immune system protects the organism by detecting and eliminating foreign and host aberrant molecules. Conversely, a dysfunctional immune system characterized by an overactive or weakened immune system causes life-threatening autoimmune or immunodeficiency diseases. Therefore, a critical need exists to develop technologies that regulate the immune system to ensure homeostasis or treat several diseases. Accumulating evidence shows that biomaterials─artificial materials (polymers, metals, ceramics, or engineered cells and tissues) that interact with biological systems─can trigger immune responses, offering a materials science-based strategy to modulate the immune system. This Review discusses the expanding frontiers of biomaterial-based immunomodulation, focusing on principles for designing these materials. This Review also presents examples of immunomodulatory biomaterials, which include polymers and metal- and carbon-based nanomaterials, capable of regulating the innate and adaptive immune systems.

Systemic enhancement of antitumour immunity by peritumourally implanted immunomodulatory macroporous scaffolds

A tumour microenvironment abundant in regulatory T (Treg) cells aids solid tumours to evade clearance by effector T cells. Systemic strategies to suppress Treg cells or to augment immunity can elicit autoimmune side effects, cytokine storms and other toxicities. Here we report the design, fabrication and therapeutic performance of a biodegradable macroporous scaffold, implanted peritumourally, that releases a small-molecule inhibitor of transforming growth factor β to suppress Treg cells, chemokines to attract effector T cells and antibodies to stimulate them. In two mouse models of aggressive tumours, the implant boosted the recruitment and activation of effector T cells into the tumour and depleted it of Treg cells, which resulted in an 'immunological abscopal effect' on distant metastases and in the establishment of long-term memory that impeded tumour recurrence. We also show that the scaffold can be used to deliver tumour-antigen-specific T cells into the tumour. Peritumourally implanted immunomodulatory scaffolds may represent a general strategy to enhance T-cell immunity and avoid the toxicities of systemic therapies.

Proteolytic activity accelerates the TH17/TH22 recall response to an epicutaneous protein allergen-induced TH2 response

Epicutaneous exposure to protein allergens, such as papain, house dust mite (HDM), and ovalbumin (OVA), represents an important mode of sensitization for skin diseases including protein contact dermatitis, immunologic contact urticaria, and atopic dermatitis. These diseases are inducible by re-exposure to an allergen at both original skin sensitization and distant skin sites. In this study, we examined the serum IgE/IgG₁ response, differentiation of T-helper (T_H) cells, and epicutaneous T_H recall response in mice pre-sensitized with protein allergens through the back skin and subsequently challenged on the ear skin. Repeated epicutaneous sensitization with allergenic proteins including papain, HDM, OVA, and protease inhibitor-treated papain, but not bovine serum albumin, induced serum allergen-specific antibody production, passive cutaneous anaphylaxis responses, and T_H2 differentiation in the skin draining lymph node (DLN) cells. Sensitization with papain or HDM, which have protease activity, resulted in the differentiation of T_H17 as well as T_H2. In papain- or HDM-sensitized mice, a subsequent single challenge on the ear skin induced the expression of T_H2 and T_H17/T_H22 cytokines. These results suggest that allergenic proteins induce the differentiation of T_H2 in skin DLN cells and an antibody response. These findings may be useful for identifying proteins of high and low allergenic potential. Moreover, allergenic proteins containing protease activity may also differentiate T_H17 and induce T_H2 and T_H17/T_H22 recall responses at epicutaneous challenge sites. This suggests that allergen protease activity accelerates the onset of skin diseases caused by protein allergens.

Dually Cross-Linked Core-Shell Structure Nanohydrogel with Redox-Responsive Degradability for Intracellular Delivery

A redox-responsive nanocarrier is a promising strategy for the intracellular drug release because it protects the payload, prevents its undesirable leakage during extracellular transport, and favors site-specific drug delivery. In this study, we developed a novel redox responsive core-shell structure nanohydrogel prepared by a water in oil nanoemulsion method using two biocompatible synthetic polymers: vinyl sulfonated poly(N-(2-hydroxypropyl) methacrylamide mono/dilactate)-polyethylene glycol-poly(N-(2-hydroxypropyl) methacrylamide mono/dilactate) triblock copolymer, and thiolated hyaluronic acid. The influence on the nanohydrogel particle size and distribution of formulation parameters was investigated by a three-level full factorial design to optimize the preparation conditions. The surface and core-shell morphology of the nanohydrogel were observed by scanning electron microscope, transmission electron microscopy, and further confirmed by Fourier transform infrared spectroscopy and Raman spectroscopy from the standpoint of chemical composition. The redox-responsive biodegradability of the nanohydrogel in reducing environments was determined using glutathione as reducing agent. A nanohydrogel with particle size around 250 nm and polydispersity index around 0.1 is characterized by a thermosensitive shell which jellifies at body temperature and crosslinks at the interface of a redox-responsive hyaluronic acid core via the Michael addition reaction. The nanohydrogel showed good encapsulation efficiency for model macromolecules of different molecular weight (93% for cytochrome C, 47% for horseradish peroxidase, and 90% for bovine serum albumin), capacity to retain the peroxidase-like enzymatic activity (around 90%) of cytochrome C and horseradish peroxidase, and specific redox-responsive release behavior. Additionally, the nanohydrogel exhibited excellent cytocompatibility and internalization efficiency into macrophages. Therefore, the developed core-shell structure nanohydrogel can be considered a promising tool for the potential intracellular delivery of different pharmaceutical applications, including for cancer therapy.

Biodegradable Cationic Polycarbonates as Vaccine Adjuvants

In this study, biodegradable cationic polycarbonate and polylactide block copolymers were synthesized and successfully used as novel vaccine adjuvants to provide enhanced anticancer immunity. The polymers formed nanoparticles with the model vaccine, ovalbumin (OVA), and the immunostimulant toll-like receptor 3 agonist poly(I:C) (a synthetic analog of the double-stranded RNA). Higher uptake of poly(I:C) by the bone marrow-derived dendritic cells and macrophages and OVA by dendritic cells was observed when delivered using the polymer adjuvant. In vivo experiments showed that these nanoparticles remained longer in the subcutaneous injection site as compared to OVA alone and led to higher production of anti-OVA specific antibodies with prolonged immunostimulation. When OVA was combined with poly(I:C) that was either co-entrapped in the same particles or as separate particles, a comparable level of anti-OVA IgG1 antibodies and interleukin-6 (IL-6) was produced in mouse blood plasma, and a similar level of cytotoxic T lymphocyte (CTL) response in mice was stimulated as compared to OVA/Alum particles. Furthermore, tumor rejection in the mice that were vaccinated for 9 months with the formulations containing the polymer adjuvant was stronger than the other treatment groups without the polymer. Notably, the cationic polycarbonates were not associated with any adverse in vivo effects. Thus, these biodegradable polymers may be promising substitutes for aluminum-based adjuvants in vaccine formulations.

Different thermal processing effects on peanut allergenicity

BACKGROUND

Peanut allergy is one of the most common food allergies worldwide. Studies have shown that the incidence of peanut allergies in Western-born Asians is higher than that in Asia-born Asians. Notably, Europeans and Americans mostly eat roasted peanuts, whereas Asians mostly eat boiled or fried peanuts.

RESULTS

BALB/c mice were sensitized using purified protein from raw, roasted or boiled peanuts, then fed the same by oral gavage. The relevant allergic reactions were studied using BALB/c mice model, including a rat basophilic leukemia (RBL) cell model, simulated gastric fluid experiments, and ultraviolet (UV) and circular dichroism (CD) spectral analysis. Serological studies showed increased levels of immunoglobulin E, interleukin-4 and interleukin-5, and pathological studies showed mast cell degranulation and inflammatory changes in jejunal tissues, with an increase in thymic stromal lymphopoietin (TSLP) gene expression in all treatment groups compared with the control group (phosphate-buffered saline). Compared with the raw peanut group, sera from the roasted peanut group produced a significant increase in RBL β-hexosaminidase A release in vitro, and roasted peanuts showed increased resistance to digestion in simulated gastric fluid experiments. Ultraviolet and CD spectral analyses showed that the roasting and boiling processes altered the structure of the major peanut allergens, which may have contributed to the differences observed in peanut allergenicity.

CONCLUSION

Our findings indicate that peanut allergies are related to peanut thermal processing methods. In our mouse model, the raw, roasted and boiled peanuts elicited different degrees of allergic response. Compared with raw peanut, roasted peanuts show a higher allergenicity, whereas the boiled peanuts show a lower allergenicity. © 2018 Society of Chemical Industry.

Assessment of the potential allergenicity of genetically-engineered food crops

An extensive safety assessment process exists for genetically-engineered (GE) crops. The assessment includes an evaluation of the introduced protein as well as the crop containing the protein with the goal of demonstrating the GE crop is "as-safe-as" non-GE crops in the food supply. One of the evaluations for GE crops is to assess the expressed protein for allergenic potential. Currently, no single factor is recognized as a predictor for protein allergenicity. Therefore, a weight-of-the-evidence approach, which accounts for a variety of factors and approaches for an overall assessment of allergenic potential, is conducted. This assessment includes an evaluation of the history of exposure and safety of the gene(s) source; protein structure (e.g. amino acid sequence identity to human allergens); stability of the protein to pepsin digestion in vitro; heat stability of the protein; glycosylation status; and when appropriate, specific IgE binding studies with sera from relevant clinically allergic subjects. Since GE crops were first commercialized over 20 years ago, there is no proof that the introduced novel protein(s) in any commercialized GE food crop has caused food allergy.

Contrast-enhanced endoscopic ultrasound for differential diagnosis of pancreatic cancer: an updated meta-analysis

Aim

We aim to assess the diagnostic value of contrast-enhanced endoscopic ultrasound (CE-EUS) for pancreatic cancer and inflammatory lesions by pooling current evidence.

Materials and Methods

A systematical search of PubMed, Web of Science and the Cochrane Library was performed from inception to January 2016. Two authors independently screened and extracted detailed data from included studies. A random effect model was adopted to estimate the pooled sensitivity, specificity in order to determine the diagnostic ablitity of CE-EUS. Furthermore, we conducted the meta-regression and subgroup analyses to explore possible heterogeneity.

Results

Eighteen eligible studies enrolling 1668 patients were finally included in the study. The pooled sensitivity of CE-EUS for distinguishing pancreatic cancers from solid inflammatory masses was 0.93 (95% CI, 0.91–0.94), and the specificity was 0.88 (95% CI, 0.84–0.90). The area under summary receiver operating characteristic curve yielded 0.97. No publication bias was observed by Deeks’ funnel plot in current meta-analysis.

Conclusions

We provided evidence that CE-EUS is a promising modality for differential diagnosis of pancreatic adenocarcinomas. Further multicenter prospective studies should be carried out to certify its utility.

Assessment of the respiratory sensitization potential of proteins using an enhanced mouse intranasal test (MINT)

There remains a need for a simple and predictive animal model to identify potential respiratory sensitizers. The mouse intranasal test (MINT) was developed to assess the relative allergic potential of detergent enzymes, however, the experimental endpoints were limited to evaluation of antibody levels. The present study was designed to evaluate additional endpoints (serum and allergic antibody levels, pulmonary inflammation and airway hyperresponsiveness (AHR)) to determine their value in improving the predictive accuracy of the MINT. BDF1 mice were intranasally instilled on days 1, 3, 10, 17 and 24 with subtilisin, ovalbumin, betalactoglobulin, mouse serum albumin or keyhole limpet hemocyanin; challenged with aerosolized methacholine or the sensitizing protein on day 29 to assess AHR, and sacrificed on day 29 or 30. Under the conditions of this study, evaluation of AHR did not improve the predictive power of this experimental model. Allergic antibody responses and IgG isotype characterization proved to be the most sensitive and reliable indicators of the protein allergenic potential with BAL responses providing additional insight. These data highlight that the evaluation of the respiratory sensitization potential of proteins can be best informed when multiple parameters are evaluated and that further improvements and refinements of the assay are necessary.

Contrast-enhanced EUS for differential diagnosis of pancreatic mass lesions: a meta-analysis

BACKGROUND

Distinguishing pancreatic adenocarcinomas from other pancreatic masses remains challenging with current imaging techniques. Contrast-enhanced EUS further improved the efficacy of EUS to characterize pancreatic lesions.

OBJECTIVE

To assess the accuracy of contrast-enhanced EUS for diagnosing adenocarcinoma in patients with pancreatic masses by pooling data of existing trials.

DESIGN

We systematically searched the Medline, PubMed, Web of Science, Embase, and Cochrane Central Trials databases for relevant studies published. Meta-analysis was performed. Pooling was conducted in a fixed-effect model or a random-effects model.

PATIENTS

Twelve studies involving 1139 patients were included.

INTERVENTION

Contrast-enhanced EUS.

MAIN OUTCOME MEASUREMENTS

Meta-analysis and meta-regression analysis.

RESULTS

The pooled sensitivity of contrast-enhanced EUS for the differential diagnosis of pancreatic adenocarcinomas was 94% (95% CI, 0.91-0.95), and the specificity was 89% (95% CI, 0.85-0.92). The area under the curve under summary receiver operating characteristic was 0.9732. The pooled positive likelihood ratio was 8.09 (95% CI, 4.47-14.64), and the negative likelihood ratio was 0.08 (95% CI, 0.06-0.10). The subgroup analysis by exclusion of the outliers provided a sensitivity of 93% (95% CI, 0.91-0.95) and a specificity of 93% (95% CI, 0.89-0.95) for the differential diagnosis of pancreatic adenocarcinomas. The area under the curve under summary receiver operating characteristic was 0.9745.

LIMITATIONS

A small number of studies met the inclusion criteria.

CONCLUSION

Contrast-enhanced EUS is a promising, reliable modality for the differential diagnosis of pancreatic adenocarcinoma in patients with pancreatic mass lesions. The finding of a hypoenhanced lesion was a sensitive and accurate predictor of pancreatic adenocarcinomas. It seems to be a useful tool in clinical practice.

Dynamic quantitative evaluation of contrast-enhanced endoscopic ultrasonography in the diagnosis of pancreatic diseases

OBJECTIVES

This study aimed to investigate the usefulness of contrast-enhanced endoscopic ultrasonography (EUS) with time-intensity curve (TIC) in differentiating pancreatic diseases.

METHODS

Patients who underwent contrast-enhanced EUS between January 2007 and June 2009 were analyzed retrospectively, including 48 with pancreatic ductal cancer (PC), 14 with autoimmune pancreatitis (AIP), 13 with mass-forming pancreatitis (MFP), and 16 with pancreatic endocrine tumor (PET). After intravenous injection of contrast agent, contrast imaging pattern, TIC-based quantitative evaluation, and diagnostic ability of EUS in combination with TIC to diagnose benignancy or malignancy were assessed.

RESULTS

Hypovascular and heterogeneous pattern (42/48) in PC, isovascular and homogenous (21/27) in AIP and MFP, and hypervascular and rapid stained (16/16) in PET were observed. The echo intensity reduction rate from the peak at 1 minute was the greatest in PC followed by MFP, AIP, and PET (P < 0.05). The diagnostic accuracies based on contrast imaging pattern (84.0%) and TIC (88.0%) were higher than those based on B-mode imaging (82.6%) and dynamic computed tomography (81.3%). In EUS in combination with TIC, sensitivity, specificity, and accuracy rose up to 95.8%, 92.6%, and 94.7%, respectively.

CONCLUSIONS

Contrast-enhanced EUS with the dynamic quantitative analysis preparing TIC increased the diagnostic accuracy for pancreatic diseases.

A single exposure to iron oxide nanoparticles attenuates antigen-specific antibody production and T-cell reactivity in ovalbumin-sensitized BALB/c mice

Background:

Superparamagnetic iron oxide nanoparticles have been used in clinical applications as a diagnostic contrasting agent. Previous studies showed that iron oxide nanoparticles deposited in the liver and spleen after systemic administration. The present study investigated the effect of iron oxide nanoparticles on antigen-specific immune responses in mice sensitized with the T cell-dependent antigen ovalbumin (OVA).

Methods:

BALB/c mice were intravenously administered with a single dose of iron oxide nanoparticles (10–60 mg Fe/kg) 1 hour prior to OVA sensitization, and the serum antibody production and splenocyte reactivity were examined 7 days later.

Results:

The serum levels of OVA-specific IgG₁ and IgG_2a were significantly attenuated by treatment with iron oxide nanoparticles. The production of interferon-γ and interleukin-4 by splenocytes re-stimulated with OVA in culture was robustly suppressed in mice administered with iron oxide nanoparticles. The viability of OVA-stimulated splenocytes was also attenuated. In contrast, treatment with iron oxide nanoparticles did not affect the viability of splenocytes stimulated with concanavalin A, a T-cell mitogen.

Conclusion:

Collectively, these data indicate that systemic exposure to a single dose of iron oxide nanoparticles compromises subsequent antigen-specific immune reactions, including the serum production of antigen-specific antibodies, and the functionality of T cells.

Use of murine models to detect the allergenicity of genetically modified Lactococcus lactis NZ9000/pNZPNK

By introducing aprN into Lactococcus lactis NZ9000, the genetically modified L. lactis NZ9000/pNZPNK successfully expressed the nattokinase. The safety assessment of this novel strain was based on allergenicity of pepsin digestion stability and murine model serologic identity. Subjecting to the GM strain and host to pepsin digestion, the soluble fractions and cell debris were fast degraded completely. Feeding with ovalbumin resulted in significantly higher production of IgG1 and IgE as compared to that of L. lactis NZ9000/pNZPNK or L. lactis NZ9000. Further, the serum IgG2a level increased dose-dependently at week 2 and induced immune reaction toward Th1 pathway. Secretion of cytokines IL-4 and IL-10 fed with lactococci was significantly lower than that of the OVA group. L. lactis NZ9000/pNZPNK did not increase the proliferation of type 2 helper T cells in spleen or induce allergenicity in BALB/c mice. On the basis of the results, the new GM lactic acid bacterium is regarded as safe to use.

Florfenicol impairs the immune responses to vaccination against foot-and-mouth disease in mice

Florfenicol is a new type of broad-spectrum antibacterial that has been used in veterinary clinics. It showed immunosuppressive activity on the immune responses to vaccination against foot-and-mouth disease virus (FMDV) serotype O in mice. In the present study, BALB/c mice were immunized subcutaneously with FMDV serotype O antigen on days 1 and 14. Beginning on day 21, mice were treated with a single daily oral dose of florfenicol (50, 100, and 200 mg/kg) for seven consecutive days. On day 28, blood samples were collected to analyze FMDV-specific immunoglobulin G (IgG), IgG1, and IgG2b antibodies, and splenocytes were harvested to assess lymphocyte proliferation, CD3(+) T- and CD19(+) B-lymphocyte subsets. The results presented here demonstrated that florfenicol not only significantly suppressed concanavalin A-, lipopolysaccharide-induced splenocyte proliferation but also decreased the percentage of CD19(+) B-cells in a dose-dependent manner and suppressed CD3(+) T-cell at high doses. Moreover, FMDV-specific IgG, IgG1, and IgG2b antibody levels in FMDV-immunized mice were reduced by florfenicol. These results suggested that florfenicol could suppress humoral and cellular immune responses to vaccination against foot-and-mouth disease (FMD) in mice.

Immunosuppressive activity of 8-gingerol on immune responses in mice

8-gingerol is one of the principal components of ginger, which is widely used in China and elsewhere as a food, spice and herb. It shows immunosuppressive activity on the immune responses to ovalbumin (OVA) in mice. In the present study, we found that 8-gingerol suppressed lipopolysaccharide (LPS) and concanavalin A (ConA)-stimulated splenocyte proliferation in vitro. In vivo, 8-gingerol not only significantly suppressed Con A-, LPS- and OVA-induced splenocyte proliferation (P < 0.05) but also decreased the percentage of CD19+ B cells and CD3+ T cell (P < 0.05) at high doses (50, 100 mg/kg). Moreover, OVA-specific IgG, IgG1 and IgG2b levels in OVA-immunized mice were reduced by 8-gingerol at doses of 50, 100 mg/kg. These results suggest that 8-gingerol could suppress humoral and cellular immune responses in mice. The mechanism might be related to direct inhibition of sensitized T and B lymphocytes.

Fine ambient particles from various sites in europe exerted a greater IgE adjuvant effect than coarse ambient particles in a mouse model

In the European Union (EU)-funded project Respiratory Allergy and Inflammation due to Ambient Particles (RAIAP), coarse and fine ambient particulate matter (PM) was collected at traffic dominated locations in Oslo, Rome, Lodz, and Amsterdam, in the spring, summer, and winter 2001/2002. PM was also collected in de Zilk, a rural seaside background location in the Netherlands. The aim of this study was to screen the ambient PM fractions for allergy adjuvant activity measured as the production of allergen- (ovalbumin-) specific immunoglobulin (Ig) E following subcutaneous (sc) injection into the footpad of mice. A second aim was to determine whether the 6-d popliteal lymph node (PLN) assay can be used to detect an allergy adjuvant activity. Allergy screening for IgE adjuvant activity showed that in the presence of ovalbumin (Ova) 12 out of 13 of the fine ambient PM fractions exerted a significant IgE adjuvant activity. In contrast, only 3 out of 13 of the coarse PM fractions had significant adjuvant activity. Overall, fine ambient PM exerted significantly greater IgE adjuvant activity per unit mass than coarse PM. No significant differences were observed between locations or seasons. Substantial higher levels of specific components of PM such as vanadium (V), nickel (Ni), zinc (Zn), ammonium (NH(4)), and sulfate (SO(4)) were present in the fine compared to coarse PM fractions. However, differences in the content of these components among fine PM fractions did not reflect the variation in the levels of IgE anti-Ova. Still, when comparing all seasons overall, positive correlations were observed between V, Ni, and SO(4) and the allergen specific IgE levels. The PLN responses (weight and cell number) to Ova and ambient PM in combination were significantly higher than to Ova or PM alone. Still, the PLN assay appears not to be useful as a quantitative assay for screening of allergy adjuvant activity since no correlation was observed between PLN responses and allergen specific IgE levels. In conclusion, fine ambient PM fractions consistently were found to increase the allergen-specific IgE responses more than the coarse ones. Our finding is in agreement with the notion that traffic-related air pollution contributes to the disease burden in asthma and allergy, and points to fine and ultrafine ambient PM as the most important fractions in relation to allergic diseases.

Bis(tributyltin)oxide (TBTO) decreases the food allergic response against peanut and ovalbumin in Brown Norway rats

Other factors than the allergen itself may be of importance in the development of food allergy. This report describes the influence of the immunosuppressive compound bis(tributyltin)oxide (TBTO), present in the food chain, on the development of food allergy to peanut or ovalbumin in Brown Norway (BN) rats. To study these effects BN rats were sensitized to either 1 or 10mg peanut or ovalbumin by daily oral gavage and the TBTO-groups were fed a diet containing 80 mg TBTO per kg diet. Co-exposure to TBTO not only resulted in decreased general immunologic parameters such as weights of mesenteric lymph nodes and Peyer's patches, lymphocyte proliferation rates in splenocytes, but also on allergic parameters. In the peanut allergen-model TBTO decreased allergen-specific Th2 cytokine production by spleen cells, number of eosinophilic and basophilic granulocytes in the blood and production of mast cell protease II after oral food challenge. In the ovalbumin allergen-model TBTO decreased the number of eosinophilic and basophilic granulocytes, allergen-specific IgE and production of mast cell protease II after oral food challenge. The data imply that in the process of risk assessment of food allergy attention should be given to immunomodulating compounds present in the diet.

IgE binding to proteins from sesame and assessment of allergenicity: implications for biotechnology?

Successful prediction of the potential allergenicity of a protein may be a key factor in the development of novel, genetically modified foods. The use of the decision tree approach for the prediction of allergenicity is discussed. The methods currently used for identifying allergenic proteins (including use of IgE from patient sera for recognition of proteins) are reviewed. Finally, a specific review of the literature concerning identification of allergens from sesame leads to the conclusion that in the absence of validated animal models, identification of allergenicity (and, consequently, prediction of allergenicity) may be problematic.

Animal models of food allergy: opportunities and barriers

The potential for animal models to mimic the human disease process makes them an attractive tool for determining disease mechanisms, predicting disease triggers, and testing treatment regimens. With this in mind, animal models of food allergy have been receiving increasing attention as research tools to answer some of the difficult questions regarding food-allergy disease. Most of the food-allergy animal models developed to date have been designed to test reagents for immunotherapeutic treatment of allergic disease and to predict the potential human allergenicity of proteins. Current animal models under development are rodent, swine, and dog. The variables affecting development of such models include allergen concentration, allergen matrix or food source, allergen route of exposure, duration, animal age, adjuvant use, and dose range of allergens. Each model presents opportunities for and barriers to a fuller understanding of the allergic response. The conditions inherent to each model and the intended purpose of the study should therefore be considered prior to its use.

Genetically modified plants and food hypersensitivity diseases: usage and implications of experimental models for risk assessment

The recent advances in biotechnology in the plant industry have led to increasing crop production and yield that in turn has increased the usage of genetically modified (GM) food in the human food chain. The usage of GM foods for human consumption has raised a number of fundamental questions including the ability of GM foods to elicit potentially harmful immunological responses, including allergic hypersensitivity. To assess the safety of foods derived from GM plants including allergenic potential, the US FDA, Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO), and the EU have developed approaches for evaluation assessment. One assessment approach that has been a very active area of research and debate is the development and usage of animal models to assess the potential allergenicity of GM foods. A number of specific animal models employing rodents, pigs, and dogs have been developed for allergenicity assessment. However, validation of these models is needed and consideration of the criteria for an appropriate animal model for the assessment of allergenicity in GM plants is required. We have recently employed a BALB/c mouse model to assess the potential allergenicity of GM plants. We have been able to demonstrate that this model is able to detect differences in antigenicity and identify aspects of protein post-translational modifications that can alter antigenicity. Furthermore, this model has also enabled us to examine the usage of GM plants as a therapeutic approach for the treatment of allergic diseases. This review discusses the current approaches to assess the allergenic potential of GM food and particularly focusing on the usage of animal models to determine the potential allergenicity of GM foods and gives an overview of our recent findings and implications of these studies.

Effect of maternal dietary cow's milk on the immune response to beta-lactoglobulin in the offspring: a four-generation study in mice

BACKGROUND

Evaluation of immune responses to food proteins in animal models requires that the animals are not already sensitized or orally tolerized against the proteins in question. Since maternal transfer of specific immune responses has been observed, breeding of animals on an antigen-free diet for several generations may be necessary to obtain immunologically naive animals.

METHODS

To determine the most appropriate breeding conditions of mice to be used in immunological studies on food proteins, we examined immune responses towards beta-lactoglobulin (BLG) in mice bred on a milk-containing diet (F0) and then for three generations (F1-F3) on a commercially available milk-free diet. The specific antibody and cell-proliferative response to BLG was compared in non-immunized and immunized BALB/c mice, and in mice orally tolerized to BLG prior to immunization.

RESULTS

The immune response to BLG in the F1 generation deviated from the response observed in the F0 and F2/F3 generations. Importantly, trace amounts of BLG detected in the commercial milk-free diet did not induce oral tolerance.

CONCLUSIONS

The study showed that breeding mice on an antigen-free diet for at least two generations is required to attain animals appropriate for immunological studies of food proteins. Although the small quantity of BLG in the milk-free diet did not induce detectable oral tolerance in the present study, it is strongly recommended that the potential effect of contaminating dietary antigen is considered in future studies on food proteins.

Lipopolysaccharide contamination of beta-lactoglobulin affects the immune response against intraperitoneally and orally administered antigen

BACKGROUND

Microbial components in the environment are potent activators of the immune system with capacity to shift the active immune response towards priming of Th1 and/or Th2 cells. Lipopolysaccharide (LPS), a cell-wall component of Gram-negative bacteria, is extensively present in food products like cow's milk. It is not well established, however, how this presence of LPS affects oral tolerance induction.

METHODS

We studied the effect of LPS contamination in a commercial preparation of the cow milk protein beta-lactoglobulin (beta-LG) on antigen-specific immune responses. IgG1/IgG2a production upon intraperitoneal immunization without adjuvant was measured, and oral tolerance induction against beta-LG after administration of either an aqueous solution or water-in-oil (w/o) emulsion of beta-LG was evaluated.

RESULTS

LPS contamination of beta-LG provoked a beta-LG-specific IgG2a response, as well as an enhanced beta-LG-specific IgG1 response upon intraperitoneal immunization. Oral tolerance induction to beta-LG was induced by aqueous solutions of beta-LG with and without LPS administration. Conversely, oral administration of w/o-emulsified beta-LG prevented oral tolerance to beta-LG only when the beta-LG was contaminated with LPS.

CONCLUSIONS

LPS contamination of an aqueous protein solution does not affect oral tolerance induction, whereas LPS present in emulsion prevents oral tolerance induction towards the food protein.

An oral Brown Norway rat model for food allergy: comparison of age, sex, dosing volume, and allergen preparation

The purpose of the presented experiments was to study the possibility of using the Brown Norway rat as a model for food allergy in our laboratory. Specific serum IgE against ovalbumin (OVA) was induced after dosing male and female Brown Norway rats daily by gavage for 35 days. The influence of various preparations of allergen: OVA grade II, OVA grade V, and fresh egg white, age (4 versus 8 weeks), dosing volumes, and animal suppliers was studied. A general finding was that females had statistically significantly higher specific IgE and IgG titres and number of responders than males. Egg white preparation, age, dosing volume, and animal supplier did not statistically significantly influence the median IgE and IgG titres and number of responders. The difference between immune responses in males and females could not be attributed to variations in daily intake of OVA or exposure via the lung. In our hands, the oral Brown rat food allergy model gives rise to a moderate number of IgE responders, 13-38 and 38-75% in males and females, respectively. For further experiments with this model in our laboratory, females seem the sex of choice.

Assessment of the allergenic potential of proteins

The development of novel foods, including foods derived from genetically modified plants, has generated considerable interest in the design and application of appropriate safety assurance measures. A specific focus of attention has been on allergenicity, and in particular the need to determine whether the products of novel genes introduced into food plants have the potential to cause allergic sensitisation. Among the approaches applied currently are considerations of whether a new protein has structural, sequence and/or antigenic similarities with known food allergens, and whether or not it displays resistance to digestion within a simulated gastric fluid, or by pepsin. Although such data are useful in an overall hazard assessment, they are neither individually, nor collectively, able to provide a direct evaluation of inherent sensitising potential. For this reason there is a need to develop and apply appropriate animal models that will offer a more holistic view of sensitising activity. Several methods have been suggested, but as yet none has been evaluated fully or validated. Nevertheless, significant progress has been made and in this article an experimental approach using BALB/c strain mice in which animals are exposed to the test protein via systemic (intraperitoneal, or in certain circumstances, intradermal) administration is described. Inherent sensitising potential is measured as a function of induced IgE antibody responses. Experience to date is encouraging and the data available reveal that this method is able to distinguish between proteins of different allergenic potential.

Investigation of the adjuvant and immuno-suppressive effects of benzyl butyl phthalate, phthalic acid and benzyl alcohol in a murine injection model

In a recent study, di-(2-ethylhexyl) phthalate (DEHP) and its metabolite, mono-2-ethylhexyl phthalate, were shown to possess adjuvant effect [Toxicology 169 (2001) 37; Toxicology Letters 125 (2001) 11]. The present study investigates the adjuvant effect of another important commercial phthalate plasticizer, benzyl butyl phthalate (BBP) as well as its degradation products, phthalic acid and benzyl alcohol (BA) in a murine model. The model antigen, ovalbumin (OA), was injected either alone (OA control group), together with one of the test substances (test group) or together with aluminium hydroxide, which served as the positive adjuvant control. The mice were boosted either once or twice with OA before blood was collected and assayed for the content of OA-specific IgE, IgG1 and IgG2a antibodies by ELISA methods. Adjuvant effect was defined as a statistically significant increased antibody level in the test groups compared with the OA control group. Conversely, if the antibody production in a test group was significantly lower than the OA control group, it was deemed to be immunosuppression. This study demonstrated that BBP, in contrast to DEHP, did not possess adjuvant effect. Furthermore, immunosuppression was apparent in the case of BA. The study also demonstrated that if the injections give rise to formation of wounds, it may cause false positive results.

Safety assessment of genetically modified crops

The development of genetically modified (GM) crops has prompted widespread debate regarding both human safety and environmental issues. Food crops produced by modern biotechnology using recombinant techniques usually differ from their conventional counterparts only in respect of one or a few desirable genes, as opposed to the use of traditional breeding methods which mix thousands of genes and require considerable efforts to select acceptable and robust hybrid offspring. The difficulties of applying traditional toxicological testing and risk assessment procedures to whole foods are discussed along with the evaluation strategies that are used for these new food products to ensure the safety of these products for the consumer.

The atopic dog as a model of peanut and tree nut food allergy

BACKGROUND

Animal models are needed that mimic human IgE-mediated peanut and tree nut allergy. Atopic dogs have been previously used in a model of food allergy to cow's milk, beef, wheat, and soy, with the demonstration of specific IgE production and positive oral challenges similar to those seen in human subjects.

OBJECTIVE

We sought to sensitize dogs to peanut, walnut, and Brazil nut and to assess whether sensitization is accompanied by clinical reactions and whether there is cross-reactivity among the different preparations.

METHODS

Eleven dogs were sensitized subcutaneously by using an established protocol with 1 microg each of peanut, English walnut, or Brazil nut protein extracts in alum first at birth and then after modified live virus vaccinations at 3, 7, and 11 weeks of age. The dogs were sensitized to other allergens, including soy and either wheat or barley. Intradermal skin tests, IgE immunoblotting to nut proteins, and oral challenges were performed with ground nut preparations.

RESULTS

At 6 months of age, the dogs' intradermal skin test responses were positive to the nut extracts. IgE immunoblotting to peanut, walnut, and Brazil nut showed strong recognition of proteins in the aqueous preparations. Each of the 4 peanut- and the 3 Brazil nut-sensitized dogs and 3 of the 4 walnut-sensitized dogs reacted on oral challenge with the corresponding primary immunogen at age 2 years. None of the peanut-sensitized dogs reacted clinically with walnut or Brazil nut challenges. One of the walnut-sensitized dogs had delayed (overnight) vomiting to Brazil nut.

CONCLUSIONS

On the basis of measurements of the mean amount of allergen eliciting a skin test response in dogs, the hierarchy of reactivity by skin testing is similar to the clinical experience in human subjects (peanut > tree nuts > wheat > soy > barley). Cross-reactivity, which was not apparent between soy and peanut or tree nuts or between peanut and tree nuts, was slight between walnut and Brazil nut. The results give further support to the dog as a model of human food allergy.

Factors affecting the development of food allergy

Food allergy is an important health issue. The estimated prevalence among adults in Western Europe is thought to be between 1 and 2%, with the frequency in infants being greater (approximately 5%). Most confirmed food allergies are associated with a relatively limited range of produce, including cow's milk, eggs, tree nuts, peanuts, wheat, fish and shellfish, although the prevalence of allergy to individual foods is known to vary geographically, due largely to differences in dietary practices. Although formal evidence is lacking, it is assumed that (in line with other forms of atopic disease) the incidence of food allergy is increasing. There is no doubt that genetic predisposition is an important determinant. However, acquisition of sensitisation to food proteins and subsequent allergic disease is known to be influenced by a variety of environmental factors and the timing, duration and extent of exposure. Moreover, the nature of the allergen itself may have an important impact on the severity and persistence of clinical disease. The purpose here is to discuss the relevance of some of these variables in the context of immunoglobulin E antibody-mediated allergic responses.

Adjuvant effect of di-n-butyl-, di-n-octyl-, di-iso-nonyl- and di-iso-decyl phthalate in a subcutaneous injection model using BALB/c mice

During the last decades, the prevalence of the allergic airway diseases, asthma and rhinitis, has increased world-wide. Introduction of environmental chemicals with adjuvant effect may play a role in this increase. In the present study, the adjuvant effects of di-n-butyl-, di-n-octyl-, di-iso-nonyl- and di-iso-decyl phthalate are studied in a screening model. Ovalbumin, used as the model antigen, was injected subcutaneously in the neck region of BALB/cJ mice with the selected phthalate in concentrations from 2-2000 microg/ml. Additionally, the mice were boosted once or twice with ovalbumin alone. Immunization with ovalbumin alone, the ovalbumin control group, served as the baseline for antibody production, whereas aluminium hydroxide served as the positive control. The levels of ovalbumin-specific IgE, IgG1 and IgG2a antibodies in sera were determined. Adjuvant effect was accepted to be present if a statistical increase in antibody production occurred in a test group as compared to an ovalbumin control group together with the fulfillment of dose-response relationships. Adjuvant effect varied strongly between the phthalates investigated. Phthalates with 8 or 9 carbon atoms in the alkyl side chains were the stronger adjuvants whereas phthalates with shorter or longer alkyl side chains possessed less adjuvant activity. Adjuvant effects were apparent either from the IgE or the IgG1 response or both, whereas no effect was seen on the IgG2a response. Additional studies with airborne exposure are required to establish whether the hazards also result in a significant risk for the development of allergy in man.

The dog as a model for food allergy

Research during the past decade has shown the dog to be an excellent model for human food allergies. Humans and dogs share many of the same allergies to foods. Furthermore, the dog model shows clinical symptoms typical of humans, that is, both experience vomiting and diarrhea. Present results suggest that the dog may provide a means to test genetically modified foods for unsuspected allergens.

Immunogenic properties of rapidly digested food proteins following gavage exposure of mice: a comparison of ovalbumin with a potato acid phosphatase preparation

The ability of food proteins to resist digestion in simulated gastric fluid (SGF) correlates with allergenic potential. The purpose of the current investigations was to determine whether this association is due solely to the failure of unstable proteins to elicit an immune response when administered orally. We have examined immune responses induced in BALB/c mice by gavage administration of ovalbumin (OVA) and a crude potato protein extract (PPE) containing acid phosphatase activity. The stability of OVA and PPE in SGF was measured using sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The ability of these proteins to stimulate specific IgG and IgE antibody production in mice following parenteral (intraperitoneal; ip) or oral (gavage) exposure was compared using enzyme-linked immunosorbent and homologous passive cutaneous anaphylaxis assays, respectively. Both OVA and PPE induced specific IgG antibody responses when administered either by gavage or by ip injection. Parenteral, but not gavage, exposure to OVA was associated with robust IgE antibody responses. Administration of PPE failed to stimulate strong IgE production via either route of exposure. Differential stability in SGF was observed, with PPE being digested extremely rapidly (within 1 min), whereas OVA was more resistant. The strong association reported by others between stability in SGF and allergenic potential is unlikely to be solely due to orally-ingested labile proteins failing to provoke immune responses due to degradation in the stomach.

Food allergy animal models: an overview

Specific food allergy is characterized by sensitization to innocuous food proteins with production of allergen-specific IgE that binds to receptors on basophils and mast cells. Upon recurrent exposure to the same allergen, an allergic response is induced by mediator release following cross-linking of cell-bound allergen-specific IgE. The determination of what makes an innocuous food protein an allergen in predisposed individuals is unknown; however, mechanistic and protein allergen predictive models are being actively investigated in a number of animal models. Currently, there is no animal model that will actively profile known food allergens, predict the allergic potential of novel food proteins, or demonstrate clinically the human food allergic sensitization/allergic response. Animal models under investigation include mice, rats, the guinea pig, atopic dog, and neonatal swine. These models are being assessed for production of IgE, clinical responses to re-exposure, and a ranking of food allergens (based on potency) including a nonfood allergen protein source. A selection of animal models actively being investigated that will contribute to our understanding of what makes a protein an allergen and future predictive models for assessing the allergenicity of novel proteins is presented in this review.

Protein allergenicity assessment of foods produced through agricultural biotechnology

Foods produced through agricultural biotechnology are reaching the consumer marketplace. These novel foods should be assessed for their safety, including their potential allergenicity. Agricultural biotechnology involves the introduction of novel proteins into the modified foods, and proteins can be allergenic. The potential allergenicity of the introduced proteins can be evaluated by focusing on the source of the gene, the homology of the newly introduced protein to known allergens, the reactivity of the novel protein with IgE antibodies from the serum of individuals with known allergies to the source of the transferred DNA or to materials that are broadly related to the source of the transferred DNA, the resistance of the novel protein to pepsin, and the immunoreactivity of the novel protein in appropriate animal models. Additional factors, such as the level of expression of the novel protein in the modified food and expression in the edible portion of the food, may also yield valuable insights. Applying such criteria provides a reasonable approach to determining whether or not the novel protein is likely to become an allergen.

A neonatal swine model for peanut allergy

BACKGROUND

Peanut allergy represents a significant health threat in the United States. The factors contributing to the severity of the allergic response and the immunopathogenic mechanisms underlying peanut allergy remain to be completely characterized. As yet, no animal model has been developed that will completely mimic the physical, immunologic, and histologic features of food allergy.

OBJECTIVE

The purpose of this investigation was to develop a neonatal pig model of peanut allergy that would mimic the allergic symptoms and the immunologic and histologic profile of human peanut allergy.

METHODS

Newborn piglets sensitized intraperitoneally with peanut extract and cholera toxin were orally challenged repeatedly with peanut meal. Physical symptoms, including emesis, lethargy, diarrhea, and respiratory distress, were monitored to determine the allergic response. Immunologic assessment was conducted through use of skin testing and the antigenic response to peanut proteins. Histologically, tissues derived from the esophagus, stomach, small intestine, and colon were assessed for morphologic changes after the oral challenge.

RESULTS

Peanut-sensitized pigs responded with physical symptoms that mimicked those seen in double-blinded, placebo-controlled oral food challenges to peanuts in children and adults. Skin testing suggested an IgE-mediated response; this was confirmed by a negative passive cutaneous anaphylaxis response of heat-treated sera obtained from peanut-sensitized animals. Damage to villi of the small intestine was similar to that seen in endoscopically obtained tissue specimens from certain food-allergic individuals.

CONCLUSION

The neonatal pig model of peanut allergy mimics the physical and immunologic characteristics of peanut allergy in human beings. The model will be useful for determining IgE-mediated mechanisms and conducting endoscopic histologic assessment of tissues and immunotherapeutic intervention strategies with repeated allergen challenges.