Evaluation of a high IgE-responder mouse model of allergy to bovine beta-lactoglobulin (BLG): development of sandwich immunoassays for total and allergen-specific IgE, IgG1 and IgG2a in BLG-sensitized mice

Investigation of the allergenicity alterations of shrimp tropomyosin as glycated by glucose and maltotriose containing advanced glycation end products

Tropomyosin (TM) is the major allergen in shrimp that is known to be the primary trigger for shrimp-induced food allergy. Our previous reports suggest that glycation could reduce the allergenicity of TM and the reduction of allergenicity is largely dependent on the sources of saccharides. This investigation aimed to investigate the glycation of TM by glucose and maltotriose as well as the effects of glycation on the allergenicity of TM. Compared to TM, the IgG-binding capacity and IgE-binding capacity of tropomyosin glycated by glucose (TM-G) was greatly reduced with a longer glycation time, the release of allergic mediators from RBL-2H3 mast cells was reduced in a time-dependent manner, and weaker allergic reactions were induced in BALB/c mice. Conversely, tropomyosin glycated by maltotriose (TM-MTS) exhibited a stronger allergenicity after 48 hours of glycation due to the generation of neoallergens that were derived from the advanced glycation end products (AGEs). In conclusion, glucose could be used to desensitize the shrimp TM-induced food allergy via glycation, which could significantly reduce the allergenicity and alleviate allergic symptoms. This work could provide a novel approach to reduce the allergenicity of shrimp tropomyosin and prevent the shrimp tropomyosin-induced food allergy.

Prebiotic Supplementation During Gestation Induces a Tolerogenic Environment and a Protective Microbiota in Offspring Mitigating Food Allergy

Food allergy is associated with alterations in the gut microbiota, epithelial barrier, and immune tolerance. These dysfunctions are observed within the first months of life, indicating that early intervention is crucial for disease prevention. Preventive nutritional strategies with prebiotics are an attractive option, as prebiotics such as galacto-oligosaccharides and inulin can promote tolerance, epithelial barrier reinforcement, and gut microbiota modulation. Nonetheless, the ideal period for intervention remains unknown. Here, we investigated whether galacto-oligosaccharide/inulin supplementation during gestation could protect offspring from wheat allergy development in BALB/cJRj mice. We demonstrated that gestational prebiotic supplementation promoted the presence of beneficial strains in the fecal microbiota of dams during gestation and partially during mid-lactation. This specific microbiota was transferred to their offspring and maintained to adulthood. The presence of B and T regulatory immune cell subsets was also increased in the lymph nodes of offspring born from supplemented mothers, suggestive of a more tolerogenic immune environment. Indeed, antenatal prebiotic supplementation reduced the development of wheat allergy symptoms in offspring. Our study thus demonstrates that prebiotic supplementation during pregnancy induces, in the offspring, a tolerogenic environment and a microbial imprint that mitigates food allergy development.

Route of Sensitization to Peanut Influences Immune Cell Recruitment at Various Mucosal Sites in Mouse: An Integrative Analysis

Symptom occurrence at the first ingestion suggests that food allergy may result from earlier sensitization via non-oral routes. We aimed to characterize the cellular populations recruited at various mucosal and immune sites after experimental sensitization though different routes. BALB/cJ mice were exposed to a major allergenic food (peanut) mixed with cholera toxin via the intra-gastric (i.g.), respiratory, cutaneous, or intra-peritoneal (i.p.) route. We assessed sensitization and elicitation of the allergic reaction and frequencies of T cells, innate lymphoid cells (ILC), and inflammatory and dendritic cells (DC) in broncho-alveolar lavages (BAL), lungs, skin, intestine, and various lymph nodes. All cellular data were analyzed through non-supervised and supervised uni/multivariate analysis. All exposure routes, except cutaneous, induced sensitization, but intestinal allergy was induced only in i.g.- and i.p.-exposed mice. Multivariate analysis of all cellular constituents did not discriminate i.g. from control mice. Conversely, respiratory-sensitized mice constituted a distinct cluster, characterized by high local inflammation and immune cells recruitment. Those mice also evidenced changes in ILC frequencies at distant site (intestine). Despite absence of sensitization, cutaneous-exposed mice evidenced comparable changes, albeit less intense. Our study highlights that the initial route of sensitization to a food allergen influences the nature of the immune responses at various mucosal sites. Interconnections of mucosal immune systems may participate in the complexity of clinical manifestations as well as in the atopic march.

Reducing the Allergenicity of Shrimp Tropomyosin and Allergy Desensitization Based on Glycation Modification

Shrimp is a major allergic food that could trigger severe food allergy, with the most significant and potent allergen of shrimp referred to as tropomyosin (TM). Glycation modification (Maillard reaction) could reportedly weaken the allergenicity of TM and generate hypoallergenic TM, while up to now, there is still a lack of investigations on the hypoallergenic glycated tropomyosin (GTM) as a candidate immunotherapy for desensitizing the shrimp TM-induced allergy. This study analyzed the effects of glycation modification on decreasing the allergenicity of TM and generated hypoallergenic GTM and how GTM absorbed to the Al(OH)₃ function as a candidate immunotherapy for desensitizing allergy. As the results, in comparison to TM, the saccharides of smaller molecular sizes could lead to more advanced glycation end products in GTMs than saccharides of greater molecular sizes, and TM glycated by saccharides of different molecular sizes (glucose, maltose, maltotriose, maltopentaose, and maltoheptaose) exhibited lower allergenicity as a hypoallergen upon activating the allergic reactions of the mast cell and mouse model, while TM glycated by maltose had insignificant allergenicity changes upon activating the allergic reactions of the mast cell and mouse model. In addition, the hypoallergenic GTM + Al(OH)₃ was efficient as a candidate immunotherapy; this work intended to offer preclinical data to promote GTM + Al(OH)₃ as a candidate allergen-specific immunotherapy for desensitizing the allergy reactions for patients allergic to shrimp food.

Characterization of systemic allergenicity of tropomyosin from shrimp (Macrobrachium nipponense) and anaphylactic reactions in digestive tract

BACKGROUND

Tropomyosin (TM) is the major allergen of crustaceans. The allergenicity of TM from Macrobrachium nipponense (MnTM) and the anaphylactic reaction in the digestive tract are still unclear. The aim of this study was to evaluate the allergenicity of MnTM and the anaphylactic reaction in the digestive tract.

RESULTS

Serum IgE and IgG1 binding ability in the TM group were significantly higher than those in the PBS and CT groups (P < 0.01) and CP group (P < 0.05), while serum IgG and IgG2a binding ability showed no obvious difference between the four groups (P > 0.05). The levels of cytokines IL-4, IL-5 and IL-13 in TM and CP groups were significantly higher than those in PBS and CT groups. Histamine and β-hexosaminidase in the TM and CP groups from basophil cell models were significantly higher than those in the PBS group. The highest mRNA expression of IL-4 and IL-13 was in the jejunum from TM-sensitized mice. Histopathological analysis showed that more immune cells infiltrated into the jejunum than the duodenum and ileum from the TM-sensitized mice.

CONCLUSIONS

MnTM could promote an allergic response in mice and lead to degranulation in basophil cells. The jejunum was more easily affected by MnTM than duodenum and ileum, and the jejunum may be the major site of allergic response in the digestive tract. © 2020 Society of Chemical Industry.

Investigation of glycated shrimp tropomyosin as a hypoallergen for potential immunotherapy

Tropomyosin (TM) is the most important allergen in shrimps that could cause food allergy. Glycation is reported to be effective in reducing TM allergenicity and produce hypoallergen; however, up to now, there are very few reports on the potential of hypoallergenic glycated TM (GTM) as allergen immunotherapy for shrimp TM-induced food allergy. This study investigated the glycation of TM-produced hypoallergen and the immunotherapeutic efficacy of GTM + Al(OH)₃ as potential allergen immunotherapy. Compared to TM, the TM glycated by glucose (TM-G), maltotriose (TM-MTS), maltopentaose (TM-MPS) and maltoheptaose (TM-MHS) had weaker allergy activation on mast cells and mouse model as a hypoallergen. However, the TM glycated by maltose (TM-M) insignificantly affected the allergenicity. In addition, the GTM absorbed into Al(OH)₃ could be efficacious as potential allergen immunotherapy, particularly for the TM glycated by the saccharides having larger molecular size (e.g., TM-MHS), which could provide preclinical data to develop GTM + Al(OH)₃ as a candidate immunotherapy for shrimp allergic patients.

Hispidulin alleviates 2,4-dinitrochlorobenzene and house dust mite extract-induced atopic dermatitis-like skin inflammation

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that affects 10-20% of the world's population. Therefore, the discovery of drugs for the treatment of AD is important for human health. Hispidulin (HPD; also known as scutellarein 6-methyl ether or dinatin) is a natural flavone that exerts anti-inflammatory effects. In the present study, the effectiveness of HPD on AD-like skin inflammation was investigated. We used a mouse AD model through repeated exposure of mice to 2,4-dinitrochlorobenzene and house dust mite extract (Dermatophagoides farinae extract, DFE) to the ears. In addition, tumor necrosis factor-α and interferon-γ-activated keratinocytes (HaCaT cells) were used to investigate the underlying mechanism of HPD action. Oral administration of HPD alleviated AD-like skin inflammations: it reduced ear thickness; serum immunoglobulin (Ig)E, DFE-specific IgE, and IgG2a levels; and inflammatory cell infiltration. HPD reduced the expression of pro-inflammatory cytokines and chemokines through inhibition of signal transducer and activator of transcription 1 nuclear factor-κB in HaCaT cells. Taken together, these results suggest that HPD could be a potential drug candidate for the treatment of AD.

Administration of Extensive Hydrolysates From Caseins and Lactobacillus rhamnosus GG Probiotic Does Not Prevent Cow's Milk Proteins Allergy in a Mouse Model

Background

Early nutrition may influence the development of food allergies later in life. In the absence of breastfeeding, hydrolysates from cow's milk proteins (CMP) were indicated as a prevention strategy in at risk infants, but their proof of effectiveness in clinical and pre-clinical studies is still insufficient. Thanks to a validated mouse model, we then assessed specific and nonspecific preventive effects of administration of extensive hydrolysates from caseins (eHC) on the development of food allergy to CMP. The additional nonspecific effect of the probiotic Lactobacillus GG (LGG), commonly used in infant formula, was also assessed.

Methods

Groups of young BALB/cByJ female mice were pretreated by repeated gavage either with PBS (control mice), or with PBS solution containing non-hydrolyzed milk protein isolate (MPI), eHC or eHC+LGG (eq. of 10 mg of protein/gavage). All mice were then experimentally sensitized to CMP by gavage with whole CM mixed with the Th2 mucosal adjuvant Cholera toxin. All mice were further chronically exposed to cow's milk. A group of mice was kept naïve. Sensitization to both caseins and to the non-related whey protein β-lactoglobulin (BLG) was evaluated by measuring specific antibodies in plasma and specific ex vivo Th2/Th1/Th17 cytokine secretion. Elicitation of the allergic reaction was assessed by measuring mMCP1 in plasma obtained after oral food challenge (OFC) with CMP. Th/Treg cell frequencies in gut-associated lymphoid tissue and spleen were analyzed by flow cytometry at the end of the protocol. Robust statistical procedure combining non-supervised and supervised multivariate analyses and univariate analyses, was conducted to reveal any effect of the pretreatments.

Results

PBS pretreated mice were efficiently sensitized and demonstrated elicitation of allergic reaction after OFC, whereas mice pretreated with MPI were durably protected from allergy to CMP. eHC+/-LGG pretreatments had no protective effect on sensitization to casein (specific) or BLG (non-specific), nor on CMP-induced allergic reactions. Surprisingly, eHC+LGG mice demonstrated significantly enhanced humoral and cellular immune responses after sensitization with CMP. Only some subtle changes were evidenced by flow cytometry.

Conclusion

Neither specific nor nonspecific preventive effects of administration of casein-derived peptides on the development of CMP food allergy were evidenced in our experimental setup. Further studies should be conducted to delineate the mechanisms involved in the immunostimulatory potential of LGG and to clarify its significance in clinical use.

Prevention of Allergy to a Major Cow's Milk Allergen by Breastfeeding in Mice Depends on Maternal Immune Status and Oral Exposure During Lactation

Background: The high incidence of food allergy in childhood points to the need of elucidating early life factors dictating allergy susceptibility. Here, we aim to address in a mouse model how the exposure to a major cow's milk allergen through breastmilk of mothers with different immune status influences food allergy outcome in offspring.

Methods: BALB/cJ future dams were either kept naïve, or sensitized through the oral route using cholera toxin (“orally sensitized”) or through the i.p. route using alum (“i.p. sensitized”), or rendered fully tolerant (oral gavage without any adjuvant) to bovine β-lactoglobulin (BLG). After mating with naïve males and delivery, mothers were orally exposed or not to BLG during the whole lactation. Then, eight groups of lactating mothers were considered: naïve, i.p. sensitized, orally sensitized, or tolerant, each exposed or not during lactation. In order to specifically address breastmilk effects on their allergy susceptibility, pups from naïve-synchronized mothers were cross-fostered by the different groups of treated dams and lactating mothers at delivery. In some experiments, mothers kept their own pups to address a possible in utero effect. BLG antigen, BLG-specific antibodies, and BLG-immune complexes were measured in breastmilk from the different lactating mother groups. Allergic sensitization was monitored in 5-weeks old female offspring (n = 7–8/group of lactating mothers) by determining BLG-specific antibodies in plasma and splenocytes cytokine secretion after i.p. injections of BLG/alum. Allergic reaction to oral BLG challenge was evaluated by measuring mMCP1 in plasma.

Results: Offspring was protected from one allergic i.p. sensitization when nursed by i.p. sensitized mothers, independently of BLG exposure during lactation. Orally sensitized dams conferred protection in offspring solely when exposed to BLG during lactation, while naïve mothers did not provide any protection upon BLG exposure. The levels of protection correlated with the levels of BLG-specific antibodies and BLG-immune complex in breastmilk. There was a trend for decreased sensitization in offspring breastfed by tolerant and exposed mothers, which was not associated with transfer of specific antibodies through breastmilk. Protection provided by nursing by treated/exposed mothers was not persistent after a boost i.p. injection of the progeny and then did not protect them from an allergic reaction induced at this time point. No additional in utero effects were evidenced.

Conclusion: Our study demonstrates the strong potential of breastmilk to modulate immune response to a major cow's milk allergen in the progeny. It highlights the importance of maternal immune status and of her consumption of the allergen during lactation in dictating the outcomes in offspring. This opens perspectives where modulating maternal immune status might increase the chance of cow's milk allergy prevention in breastfed children.

Induction of Oral Tolerance by Pepsin-Digested Gliadin Retaining T Cell Reactivity in a Mouse Model of Wheat Allergy

BACKGROUND

Wheat is known as the most widely consumed food all over the world. Although many types of wheat allergy have been recognized, their treatment still has a long way to go due to the complex pathogenesis. Oral immunotherapy (OIT) is under investigation for the treatment of wheat allergies. Previous studies have demonstrated that OIT using intact wheat allergens can induce tolerance, but is accompanied by a high risk of anaphylactic reactions.

OBJECTIVES

Our objective was to prepare modified wheat allergens with hypoallergenic and tolerance-inducing properties to reduce adverse effects during immunotherapy.

METHODS

Wheat gliadin was degraded by hydrolysis with pepsin and trypsin, and then the hydrolysate was deamidated with hydrochloric acid. The IgE-binding capacity and T cell reactivity of the degraded gliadins were evaluated in vitro. Pepsin-digested gliadin (peptic-GLI) was applied in a mouse model to investigate whether it would induce oral tolerance.

RESULTS

Degradation with pepsin decreased IgE-binding capacity and maintained T cell reactivity. Oral administration of peptic-GLI to mice before sensitization and challenge with gliadin could significantly suppress the production of IgE, IgG1, and type 2 T helper cytokines. Moreover, the development of anaphylactic reactions and allergic responses of the small intestine induced by gliadin challenge were inhibited by oral administration of peptic-GLI.

CONCLUSIONS

The findings of this study indicate that peptic-GLI with low allergenicity and potential for tolerance induction may become useful in wheat immunotherapy with less adverse effects.

Glycation by saccharides of different molecular sizes affected the allergenicity of shrimp tropomyosin via epitope loss and the generation of advanced glycation end products

Tropomyosin is the most potent allergen of shrimp that can cause severe food allergy. However, to date, an effective approach to eliminate this allergenicity is still lacking. Glycation is a promising approach that can reduce the allergenicity of shrimp tropomyosin by destroying the epitopes; however, advanced glycation end products (AGEs) are also generated during glycation, which can function as neoallergens to strengthen the allergenicity; therefore, it is hard to tell how the glycation of an allergen with different saccharides affects the allergenicity via epitope loss and neoallergen generation. This study was aimed at the elucidation of how the glycation of tropomyosin (TM) with saccharides of different molecular sizes (glucose, maltose, and maltotriose) affected the allergenicity through epitope loss and the generation of neoallergns that belonged to advanced glycation end products (AGEs). Saccharides of higher molecular sizes (maltotriose) could lead to higher glycated TM than saccharides of smaller molecular sizes (glucose and maltose). Compared with TM, the TM glycated by glucose (TM-G) and maltotriose (TM-MTS) had lower allergenicity and contributed to weaker mouse allergy symptoms; on the other hand, the TM glycated by maltose (TM-M) had no significant impact on the allergenicity due to the generation of AGE-related neoallergens, which might offset the glycation-induced epitope loss. The glycation of TM by maltotriose led to lower generation of AGE neoallergens (e.g. CML) than that in the cases of glucose and maltose; therefore, maltotriose could be applied to desensitize TM-induced food allergy through glycation, and this could be a potential immunotherapy for shrimp allergy patients.

Inhibitory effect of ethanol extract of Ampelopsis brevipedunculata rhizomes on atopic dermatitis-like skin inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts from various parts of Ampelopsis brevipedunculata has been used as anti-inflammatory agents in Asian folk medicine.

AIM OF THE STUDY

To demonstrate the medicinal effect of the A. brevipedunculata in skin inflammation, specifically atopic dermatitis (AD).

MATERIALS AND METHODS

The effect of ethanol extract of A. brevipedunculata rhizomes (ABE) on AD was examined using an AD-like skin inflammation model induced by repeated exposure to house dust mite (Dermatophagoides farinae extract, DFE) and 2,4-dinitrochlorobenzene (DNCB). The mechanism study was performed using tumor necrosis factor (TNF)-α and interferon (IFN)-γ-activated human keratinocytes (HaCaT). Serum histamine and immunoglobulin levels were quantified using enzymatic kits, while the gene expression of cytokines and chemokines was analyzed using quantitative real time polymerase chain reaction. The expression of signaling molecules was detected using Western blot.

RESULTS

Oral administration of ABE alleviated DFE/DNCB-induced ear thickening and clinical symptoms, as well as immune cell infiltration (mast cells and eosinophils) into the dermal layer. Serum Immunoglobulin (Ig) E, DFE-specific IgE, IgG2a, and histamine levels were decreased after the administration of ABE. ABE also inhibited CD4⁺IFN-γ⁺ and CD4⁺IL-4⁺ lymphocyte polarization in lymph nodes and expression of TNF-α, IFN-γ, IL-4, IL-13, and IL-31 in the ear tissue. In TNF-α/INF-γ-stimulated keratinocytes, ABE inhibited the gene expression of TNF-α, IL-6, IL-1β, and CCL17. In addition, ABE decreased the nuclear localization of signal transducer and activator of transcription 1 and nuclear factor-κB, and the phosphorylation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase.

CONCLUSION

Collectively, our data demonstrate the pharmacological role and signaling mechanism of ABE in the regulation of skin allergic inflammation, which supports our suggestion that ABE could be developed as a potential therapeutic agent for the treatment of AD.

Evaluation of the efficiency of hydrolyzed whey formula to prevent cow's milk allergy in the BALB/c mouse model

BACKGROUND

Partially hydrolyzed milk formulas have been proposed for primary prevention in at-risk infants, but evidence of their efficiency and elucidation of the underlying mechanisms are still lacking. Thanks to a Th2-biased mouse model mimicking at-risk patients, we aimed to assess the potency of a partially hydrolyzed whey formula (pHWF) to induce oral tolerance thus preventing further cow's milk (CM) allergy.

METHODS

BALB/c mice were gavaged with pHWF, standard milk formula (SF), or vehicle only (PBS+). All mice were then orally sensitized to CM using cholera toxin and further chronically exposed to CM. Humoral (IgE, IgG1, IgG2a) and cellular (Th2/Th1/Th17 cytokine secretion; frequency of CD4+GATA3+ and CD4+CD25+Foxp3+ T cells in the spleen) responses against β-lactoglobulin (BLG) and whole caseins (CAS) were assessed, as well as a marker of elicitation of allergic reaction (mMCP-1) released after an oral challenge with CM.

RESULTS

All markers of sensitization and of allergic reaction were evidenced in the PBS+ mice and were significantly enhanced upon chronic exposure. Gavage with SF totally and durably prevented sensitization and elicitation of the allergic reaction. Conversely, pre-treatment with pHWF only reduced BLG-specific sensitization (IgE, Th2 cytokines), with no significant effect on sensitization to caseins. However, pHWF pre-treatment significantly reduced mMCP-1 concentration in plasma after CM challenges. CD4+CD25+Foxp3+ Treg cell frequency could not be correlated with tolerance efficiency.

CONCLUSION

Partially hydrolyzed whey formula only partially prevents the further development of CM allergy in this Th2-biased model. A hydrolysate from both whey and casein fractions may be more efficient.

Insight into the effects of deglycosylation and glycation of shrimp tropomyosin on in vivo allergenicity and mast cell function

Deglycosylation of TM exacerbated allergenicity and allergy response; glycation of TM by glucose led to weaker allergenicity and allergy response.

Immunoreactive properties of α-casein and κ-casein: Ex vivo and in vivo studies

The aim of this study was to evaluate the ex vivo and in vivo studies immune potential of α- and κ-casein. Ex vivo, naïve mouse splenocytes were stimulated with α- or κ-casein. After 120 h of culture, the proliferation index (PI), determined by 3-(4,5 dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and carboxyfluorescein diacetate N-succinimidyl ester (CFSE) staining, did not vary for either antigen, suggesting similar ex vivo immunogenic potential of both casein fractions. In vivo, BALB/ccmdb mice were sensitized with α- or κ-casein and then gavaged with primary antigen. Mice immunized with α-casein had higher levels of IgG (2^16.33) and IgA (2^10.22) in serum at the end of the experiment compared with mice immunized with κ-casein (2¹⁵ and 2^9.3 for IgG and IgA, respectively). The use of α-casein for mouse immunization and ex vivo lymphocyte stimulation resulted in higher concentrations of secreted cytokines (IL-4, IL-10) compared with κ-casein stimulation. This is consistent with increasing regulatory T cell (Treg) lymphocyte populations, independent of the antigen used for stimulation. In summary, the immunogenic potential of α- and κ-casein was similar. Humoral and cellular immune responses confirmed their strong, independent potential to induce B and T cells. We propose that the lymphocyte proliferation index be used as an initial screening for protein immunogenicity.

Anti‑inflammatory effect of Amomum xanthioides in a mouse atopic dermatitis model

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disorder. The present study investigated the effects of Amomum xanthioides extract (AXE) on AD‑like skin inflammation using a Dermatophagoides farinae extract (DFE) and 2,4‑dinitrochlorobenzene (DNCB)‑induced mouse AD model. Hematoxylin and eosin staining results demonstrated that repeated DFE/DNCB exposure markedly increased the thickening of the dermis and epidermis, in addition to the infiltration of eosinophils and mast cells. However, oral administration of AXE reduced these histopathological alterations in a dose‑dependent manner. Elevated serum histamine, total and DFE‑specific immunoglobulin E (IgE), and IgG2a were also decreased by treatment with AXE. In addition, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) results demonstrated that the mRNA expression of tumor necrosis factor (TNF)‑α, interferon (IFN)‑γ, interleukin (IL)‑4, IL‑13, IL‑31 and IL‑17A was reduced in ear skin following AXE administration in AD mice. Fluorescence‑activated cell sorting demonstrated that the population of CD4+/IL‑4+, CD4+/IFN‑γ+ and CD4+/IL‑17A+ cells in draining lymph nodes was also significantly decreased in AXE‑treated mice compared with AD mice without AXE treatment. Furthermore, keratinocytes that were stimulated with TNF‑α and IFN‑γ exhibited increased gene expression of pro‑inflammatory cytokines and chemokines, including TNF‑α, IL‑1β, IL‑6, IL‑8, C‑C motif chemokine ligand (CCL)17 and CCL22, as determined by RT‑qPCR. However, upregulation of these genes was reduced by AXE pretreatment. Based on these results, we hypothesize that AXE may be useful in the treatment of allergic skin inflammation, particularly AD.

Neonatal mono-colonization of germ-free mice with Lactobacillus casei enhances casein immunogenicity after oral sensitization to cow's milk

SCOPE

Food allergy is an increasing global health problem and perinatal administration of probiotic bacteria is currently under investigation in order to prevent the development of allergic diseases. Here, we investigated the impact of neonatal mono-colonization of mice with Lactobacillus casei BL23 on an oral sensitization to cow's milk.

METHODS AND RESULTS

Mono-colonized (LC) mice were obtained by inoculating L. casei to germ-free (GF) parents. Nine-week-old GF, LC, and conventional (CV) mice were orally sensitized to cow's milk with cholera toxin as adjuvant. Compared to GF and CV mice, LC mice developed higher casein-specific IgG responses. In contrast, no significant differences between GF and LC mice were observed for the humoral responses against whey proteins. Immunoblotting experiments performed on αS1-casein hydrolysates revealed the presence of small peptides immunoreactive with sera from LC mice but not from GF mice. After in vitro reactivation of splenocytes, secretion of IL-17 was higher in LC mice than in GF and CV mice.

CONCLUSION

Neonatal mono-colonization by L. casei BL23 modulated the allergic sensitization toward food antigens. Furthermore, our data suggest that casein-specific humoral responses in LC mice were enhanced because of casein hydrolysis by L. casei into immunogenic peptides.

Heat processing of peanut seed enhances the sensitization potential of the major peanut allergen Ara h 6

SCOPE

Processing of food has been shown to impact IgE binding and functionality of food allergens. In the present study, we investigated the impact of heat processing on the sensitization capacity of Ara h 6, a major peanut allergen and one of the most potent elicitors of the allergic reaction.

METHODS AND RESULTS

Peanut extracts obtained from raw or heat-processed peanut and some fractions thereof were biochemically and immunochemically characterized. These extracts/fractions, purified Ara h 6, or recombinant Ara h 6 including Ara h 6 mutants lacking disulfide bridges were used in in vitro digestion tests and mouse models of experimental sensitization. Peanut roasting led to the formation of complexes of high molecular weight, notably between Ara h 6 and Ara h 1, which supported the induction of IgE specific to native Ara h 6. On the contrary, a fraction containing free monomeric 2S albumins or purified native Ara h 6 displayed no intrinsic allergenicity. In addition to complex formation, heat denaturation and/or partial destabilization enhanced Ara h 6 immunogenicity and increased its sensitivity to digestion.

CONCLUSION

These results suggest that sensitization potency and IgE binding capacity can be supported by different structures, modified and/or produced during food processing in interaction with other food constituents.

Bifidobacterium longum BBMN68-specific modulated dendritic cells alleviate allergic responses to bovine β-lactoglobulin in mice

AIMS

This study was designed to demonstrate the protective effects of Bifidobacterium longum BBMN68-specific modulated dendritic cells (DCs) on allergic inflammation in β-lactoglobulin (BLG)-sensitized mice.

METHODS AND RESULTS

BALB/c mice were sensitized to BLG in accordance with a model of food allergy protocol and given oral BBMN68 daily. BBMN68 was found to significantly reduce BLG-specific hypersensitivity reactions by suppressing the aberrant balance of Th1/Th2 responses with increasing the number of CD4+CD25+Foxp3+ Treg cells in mesenteric lymph nodes (MLN) by 48·1%. The level of CD103+DCs was up-regulated by 136·7 and 56·2% in payer's patches and MLN, respectively, in response to the lower expression levels of cell-surface molecules (CD86 and MHC-II) induced by BBMN68 supplementation. The CD11c+DCs isolated from BBMN68 mice showed 45·6% more Foxp3+ expression in vitro.

CONCLUSIONS

These data suggest that BBMN68-specific induction of CD11c+CD103+DCs and semi-mature DCs reduce BLG allergic reactions.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data confirm that BBMN68 may be a suitable therapeutic approach to the alleviation of food allergies, and BBMN68-specific induction of CD11c+CD103+DCs and semi-mature DCs are associated with this protection.

Food allergy in mice is modulated through the thymic stromal lymphopoietin pathway

Background

Thymic stromal lymphopoietin (TSLP) is involved in the pathogenesis of allergic reactions in the skin and the lung. Nevertheless, data on the role of TSLP in food allergy are scarce. We explored the role of TSLP in a mouse model with oral sensitization and oral challenge eliciting food allergy.

Methods

TSLP receptor (TSLPR)−/− mice and wild type mice were orally sensitized to β-lactoglobulin in presence of cholera toxin (CT) or CT alone. The elicited immune response was characterized in vitro and the mice were subsequently challenged with the antigen. Lymphocytes from various locations in the gut were activated either by the antigen or by CT and assayed for cytokine secretion.

Results

Here we report that TSLPR−/− are less prone to generate food-induced reactions in conjunction with a decreased antigen-specific IgG1, but not IgE response. In addition, mesenteric lymphnode lymphocytes of TSLPR−/− mice were secreting lower quantities of IL-4, IL-5 and IL-10 after in vivo Ag activation, whereas higher numbers of IL-17 secreting cells were observed. Similarly, activation by the Th2-type adjuvant cholera toxin resulted in an increased frequency of IL-12 and IL-17 secreting lamina propria and mesenteric lymphocytes, together with increased production of IL-12 by activated dendritic cells in TSLPR−/− mice.

Conclusions

TSLP can be considered as an essential, but not exclusive, mediator for elicitation of food allergy in mice, as well as a potential target for future therapeutic interventions.

Gut T cell receptor-γδ(+) intraepithelial lymphocytes are activated selectively by cholera toxin to break oral tolerance in mice

The gut immune system is usually tolerant to harmless foreign antigens such as food proteins. However, tolerance breakdown may occur and lead to food allergy. To study mechanisms underlying food allergy, animal models have been developed in mice by using cholera toxin (CT) to break tolerance. In this study, we identify T cell receptor (TCR)-γδ(+)  intraepithelial lymphocytes (IELs) as major targets of CT to break tolerance to food allergens. TCR-γδ(+)  IEL-enriched cell populations isolated from mice fed with CT and transferred to naive mice hamper tolerization to the food allergen β-lactoglobulin (BLG) in recipient mice which produce anti-BLG immunoglobulin (Ig)G1 antibodies. Furthermore, adoptive transfer of TCR-γδ(+)  cells from CT-fed mice triggers the production of anti-CT IgG1 antibodies in recipient mice that were never exposed to CT, suggesting antigen-presenting cell (APC)-like functions of TCR-γδ(+)  IELs. In contrast to TCR-αβ(+)  cells, TCR-γδ(+)  IELs bind and internalize CT both in vitro and in vivo. CT-activated TCR-γδ(+)  IELs express major histocompatibility complex (MHC) class II molecules, CD80 and CD86 demonstrating an APC phenotype. CT-activated TCR-γδ(+)  IELs migrate to the lamina propria, where they produce interleukin (IL)-10 and IL-17. These results provide in-vivo evidence for a major role of TCR-γδ(+)  IELs in the modulation of oral tolerance in the pathogenesis of food allergy.

Influence of the route of exposure and the matrix on the sensitisation potency of a major cows' milk allergen

Background

Allergic sensitisation to food may occur through non-gastrointestinal routes such as via skin or lung. We recently demonstrated in mice that cutaneous or respiratory pre-exposures to peanut proteins on intact epithelia induce a Th2 priming and allow subsequent oral sensitization without the use of adjuvant. We then aimed to assess the impact of a similar pattern of exposure to another relevant food allergen, cows’ milk.

Findings

The humoral and cellular immune response induced in BALB/cJ mice after repeated cutaneous applications on intact skin or after intranasal administration of cows’ milk proteins was analysed. In order to assess the potential effect of the food matrix, we used either a purified major cows’ milk allergen, β-lactoglobulin (BLG), or whole cows’ milk containing the same amount of BLG. We then studied the impact of these pre-exposures on a subsequent oral exposure to milk in the presence or absence of the mucosal Th2 adjuvant, Cholera toxin (CT). Cutaneous applications of milk induced production of BLG-specific IgE and IgG1 in 5 and 8 mice out of 20 respectively, whereas purified BLG alone did not. Intranasal exposure to milk, but not to BLG, led to BLG-specific IgG1 production in 8 out of 20 mice. Notably, cutaneous pre-exposure to milk favours further oral sensitisation without CT, while intra-nasal pre-exposure to BLG prevents further experimental sensitisation.

Conclusions

Altogether, our results thus demonstrated that the immune response induced after non-gastrointestinal exposure to food depends on the allergen, the matrix and the route of exposure.

Genetics of allergic diseases

Genome-wide association studies (GWAS) have been employed in the field of allergic disease, and significant associations have been published for nearly 100 asthma genes/loci. An outcome of GWAS in allergic disease has been the formation of national and international collaborations leading to consortia meta-analyses, and an appreciation for the specificity of genetic associations to sub-phenotypes of allergic disease. Molecular genetics has undergone a technological revolution, leading to next-generation sequencing strategies that are increasingly employed to hone in on the causal variants associated with allergic diseases. Unmet needs include the inclusion of diverse cohorts and strategies for managing big data.

Cutaneous or respiratory exposures to peanut allergens in mice and their impacts on subsequent oral exposure

BACKGROUND

Recent data suggested that non-gastrointestinal exposure can lead to sensitisation to food allergens. We thus assessed the immune impact of respiratory or cutaneous exposure to peanut proteins on non-altered epithelium and investigated the effect of such pre-exposure on subsequent oral administration of peanut.

METHODS

BALB/cJ mice were exposed to purified Ara h 1 or to a non-defatted roasted peanut extract (PE) by simple deposit of allergens solutions on non-altered skin or in the nostrils. Exposures were performed 6 times at weekly intervals. Pre-exposed mice then received intra-gastric administrations of PE alone or in the presence of the Th2 mucosal adjuvant cholera toxin (CT). The specific humoral and cellular immune response was assessed throughout the protocol.

RESULTS

Both cutaneous and respiratory exposures led to the production of specific IgG1. Local and systemic IL-5 and IL-13 production were also evidenced, demonstrating activation of specific Th2 cells. This effect was dose-dependent and most efficient via the respiratory route. Moreover, these pre-exposures led to the production of specific IgE antibodies after gavage with PE, whatever the presence of CT.

CONCLUSIONS

Cutaneous or respiratory exposures to peanut induce Th2 priming in mice. Moreover, pre-exposures promote further sensitisation via the oral route without the use of CT; this proposes a new adjuvant-free experimental model of sensitisation to food that may reflect a realistic exposure pattern in infants. These results also suggest that non-gastrointestinal peanut exposure should be minimised in high-risk infants, even those with non-altered skin, to potentially reduce allergic sensitisation to this major food allergen.

Immune response elicited by DNA vaccination using Lactococcus lactis is modified by the production of surface exposed pathogenic protein

In this study, we compared immune responses elicited by DNA immunization using Lactococcus lactis or L. lactis expressing the Staphylococcus aureus invasin Fibronectin Binding Protein A (FnBPA) at its surface. Both strains carried pValac:BLG, a plasmid containing the cDNA of Beta-Lactoglobulin (BLG), and were designated LL-BLG and LL-FnBPA+ BLG respectively. A T_H2 immune response characterized by the secretion of IL-4 and IL-5 in medium of BLG reactivated splenocytes was detected after either oral or intranasal administration of LL-FnBPA+ BLG. In contrast, intranasal administration of LL-BLG elicited a T_H1 immune response. After BLG sensitization, mice previously intranasally administered with LL-BLG showed a significantly lower concentration of BLG-specific IgE than the mice non-administered. Altenatively administration of LL-FnBPA+ BLG didn't modify the BLG-specific IgE concentration obtained after sensitization, thus confirming the T_H2 orientation of the immune response. To determine if the T_H2-skewed immune response obtained with LL-FnBpA+ BLG was FnBPA-specific or not, mice received another L. lactis strain producing a mutated form of the Listeria monocytogenes invasin Internalin A intranasally, allowing thus the binding to murine E-cadherin, and containing pValac:BLG (LL-mInlA+ BLG). As with LL-FnBPA+ BLG, LL-mInlA+ BLG was not able to elicit a T_H1 immune response. Furthermore, we observed that these difference were not due to the peptidoglycan composition of the cell wall as LL-FnBPA+ BLG, LL-mInlA+ BLG and LL-BLG strains shared a similar composition. DNA vaccination using LL-BLG elicited a pro-inflammatory T_H1 immune response while using LL-FnBPA+ BLG or LL-mInlA+ BLG elicited an anti-inflammatory T_H2 immune response.

Immunomodulatory potential of partially hydrolyzed β-lactoglobulin and large synthetic peptides

The immunomodulatory potential of fragments derived from the cow's milk allergen bovine β-lactoglobulin (BLG) was assessed in a mouse model of oral tolerance (OT) [Adel-Patient, K.; Wavrin, S.; Bernard, H.; Meziti, N.; Ah-Leung, S.; Wal, J. M. Oral tolerance and Treg cells are induced in BALB/c mice after gavage with bovine β-lactoglobulin. Allergy 2011, 66 (10), 1312-1321]. Native BLG (nBLG) and chemically denatured BLG (lacking S-S bridges, dBLG), products resulting from their hydrolysis using cyanogen bromide (CNBr) and some synthetic peptides, were produced and precisely characterized. CNBr hydrolysates correspond to pools of peptides of various sizes that are still associated by S-S bridges when derived from nBLG. nBLG, dBLG, and CNBr hydrolysate of nBLG efficiently prevented further sensitization. CNBr hydrolysate of dBLG was less efficient, suggesting that the association by S-S bridges of peptides increased their immunomodulatory potential. Conversely, synthetic peptides were inefficient even if covering 50% of the BLG sequence, demonstrating that the immunomodulatory potential requires the presence of all derived fragments of BLG and further supporting the use of partially hydrolyzed milk proteins to favor OT induction in infants with a risk of atopy.

Delayed bacterial colonization of the gut alters the host immune response to oral sensitization against cow's milk proteins

SCOPE

Cow's milk allergy is the most prevalent food allergy in infants whose immune system development is critically stimulated during postnatal gut colonization by commensal bacteria. Allergenic potential of cow's milk β-lactoglobulin (BLG) and caseins (CAS) was investigated in germ-free (GF) BALB/c mice and in GF mice conventionalized (CVd) at 6 weeks of age.

METHODS AND RESULTS

Oral sensitization to cow's milk in the presence of cholera toxin led to higher BLG-specific IgE, IgG1, and IgG2a responses in GF mice than in conventional (CV) mice. No significant difference was observed for CAS-specific IgE responses although IgG1 responses to αS1- and κ-caseins were higher in GF mice than in CV mice. CVd mice, orally inoculated with fecal preparations from CV mice, also displayed biased antibody responses compared to CV mice. Secretion of Th2 cytokines by BLG- and CAS-reactivated splenocytes of CVd mice was similar to that of GF mice whereas cytokine production by reactivated cells from mesenteric lymph nodes of CVd mice was equivalent to that of CV mice.

CONCLUSION

Oral sensitization to BLG and CAS was differentially affected by the absence of gut microbiota and delayed bacterial colonization altered persistently the host immune response to oral sensitization against food antigens.

Oral tolerance and Treg cells are induced in BALB/c mice after gavage with bovine β-lactoglobulin

BACKGROUND

Food allergy is considered as resulting from an impaired development or a breakdown of oral tolerance. We aimed to induce oral tolerance to the major cow's milk allergen bovine β-lactoglobulin (BLG) or corresponding trypsin hydrolysates (BLG-Try) and to investigate the mechanisms involved.

METHODS

Wild-type BALB/cJ mice were gavaged on days 1-3 and 8-10 with different doses of native BLG (nBLG) or with nBLG-Try and were then sensitized on day 14 by i.p. administration of BLG in alum. Sensitization was assessed by measurement of BLG-specific antibodies in sera and of cytokines secreted by BLG-reactivated splenocytes. Elicitation of the allergic reaction was assessed by measurement of cytokines and mMCP-1 in sera collected 35 min after an oral challenge. Cellular and biochemical markers of the allergic reaction were also analysed in bronchoalveolar lavage fluids (BAL) collected 24 h after intra-nasal challenge. Analysis of the CD4(+) CD25(+) Foxp3(+) cells in different organs obtained 3 days after gavage and in vivo depletion of CD25(+) cells before oral tolerance induction were then performed.

RESULTS

Systemic sensitization and elicitation of the allergic reaction were totally inhibited in mice gavaged with 2 mg of nBLG whereas nBLG-Try was far less efficient. A high percentage of CD4(+) Foxp3(+) cells were observed in BAL from tolerant mice, and a negative correlation between the number of eosinophils and the percentage of Foxp3(+) cells was evidenced. Efficient induction of CD4(+) CD25(+) Foxp3(+) cells after nBLG gavage and impaired oral tolerance induction after in vivo depletion of CD25 cells were then demonstrated.

CONCLUSION

For the first time, allergen-induced Treg cells that inhibited both the sensitization and the elicitation of the allergic reaction were evidenced in gavaged wild-type mice.

Allergenic and immunogenic potential of cow's milk β-lactoglobulin and caseins evidenced without adjuvant in germ-free mice

SCOPE

In most animal models of allergy, the development of an IgE response requires the use of an adjuvant. Germ-free (GF) mice exhibit Th2-polarized antibody responses combined with defective immunosuppressive mechanisms. The sensitizing potential of milk proteins was investigated in GF mice in the absence of adjuvant.

METHODS AND RESULTS

β-lactoglobulin (BLG) and whole casein (CAS) allergenicity was evaluated by means of intraperitoneal injections without adjuvant. Injections of BLG induced significant IgE and IgG1 responses in GF mice, while CAS injections provoked the production of IgG1 toward κ- and αS1-caseins. No significant antibody response was evidenced in conventional (CV) mice. After in vitro BLG-reactivation, IL-4, IL-5, IL-13 and IFN-γ productions by splenocytes were higher in GF mice than in CV mice. Heat-treatment decreased BLG allergenicity as indicated by the absence of IgE production in GF mice. However, heat-treatment increased protein immunogenicity and led to the production of anti-BLG and anti-κ-casein IgG1 in both GF and CV mice. This correlated with enhanced productions of IL-4, IL-5 and IL-13 in BLG-reactivated splenocytes from CV mice.

CONCLUSION

Gut colonization by commensal bacteria appeared then to significantly reduce the susceptibility of mice toward the intrinsic allergenic and immunogenic potential of milk proteins.

Recognition of the major cat allergen Fel d 1 through the cysteine-rich domain of the mannose receptor determines its allergenicity

Dendritic cells are professional antigen-presenting cells that are specialized in antigen uptake and presentation. Allergy to cat has increased substantially in recent years and has been shown to be positively associated with asthma. We have recently shown that the mannose receptor (MR), a C-type lectin expressed by dendritic cells, recognizes various glycoallergens from diverse sources and is involved in promoting allergic responses to a major house dust mite allergen in vitro. Here we investigated the potential role of MR in allergic responses to Fel d 1, a major cat allergen. Fel d 1 binding to MR was confirmed by ELISA. Using blocking, gene silencing (siRNA) experiments, and MR knock-out (MR(-/-)) cells, we have demonstrated that MR plays a major role in internalization of Fel d 1 by human and mouse antigen-presenting cells. Intriguingly, unlike other glycoallergens, recognition of Fel d 1 by MR is mediated by the cysteine-rich domain, which correlates with the presence of sulfated carbohydrates in natural Fel d 1. WT and MR(-/-) mice were used to study the role of MR in allergic sensitization to Fel d 1 in vivo. MR(-/-) mice sensitized with cat dander extract and Fel d 1 produced significantly lower levels of total IgE, Fel d 1-specific-IgE and IgG1, the hallmarks of allergic response, compared with WT mice. Our data show for the first time that Fel d 1 is a novel ligand of the cysteine-rich domain of MR and that MR is likely to play a pivotal role in allergic sensitization to airborne allergens in vivo.

Immunological and metabolomic impacts of administration of Cry1Ab protein and MON 810 maize in mouse

We have investigated the immunological and metabolomic impacts of Cry1Ab administration to mice, either as a purified protein or as the Cry1Ab-expressing genetically modified (GM) MON810 maize. Humoral and cellular specific immune responses induced in BALB/cJ mice after intra-gastric (i.g.) or intra-peritoneal (i.p.) administration of purified Cry1Ab were analyzed and compared with those induced by proteins of various immunogenic and allergic potencies. Possible unintended effects of the genetic modification on the pattern of expression of maize natural allergens were studied using IgE-immunoblot and sera from maize-allergic patients. Mice were experimentally sensitized (i.g. or i.p. route) with protein extracts from GM or non-GM maize, and then anti-maize proteins and anti-Cry1Ab–induced immune responses were analyzed. In parallel, longitudinal metabolomic studies were performed on the urine of mice treated via the i.g. route. Weak immune responses were observed after i.g. administration of the different proteins. Using the i.p. route, a clear Th2 response was observed with the known allergenic proteins, whereas a mixed Th1/Th2 immune response was observed with immunogenic protein not known to be allergenic and with Cry1Ab. This then reflects protein immunogenicity in the BALB/c Th2-biased mouse strain rather than allergenicity. No difference in natural maize allergen profiles was evidenced between MON810 and its non-GM comparator. Immune responses against maize proteins were quantitatively equivalent in mice treated with MON810 vs the non-GM counterpart and no anti-Cry1Ab–specific immune response was detected in mice that received MON810. Metabolomic studies showed a slight “cultivar” effect, which represented less than 1% of the initial metabolic information. Our results confirm the immunogenicity of purified Cry1Ab without evidence of allergenic potential. Immunological and metabolomic studies revealed slight differences in mouse metabolic profiles after i.g. administration of MON810 vs its non-GM counterpart, but no significant unintended effect of the genetic modification on immune responses was seen.

Evaluation of biotechnology-derived novel proteins for the risk of food-allergic potential: advances in the development of animal models and future challenges

Increasing concern from the public about the safety of genetically modified food has made critical to have suitable methods for recognizing associated potential hazards. Hierarchical approaches to allergenicity determination were proposed, and these include evaluation of the structural and sequence homology and serological identity of novel proteins with existing allergens, measuring the resistance to proteolytic digestion and assessment of sensitizing potential using animal models. Allergic individuals have a predisposed (i.e. atopic) genetic background, and a close resemblance to this setup is therefore desirable in animal models, which is possible by using a strain of an animal species that is prone for allergic disorders. So far, none of the animal model has been validated for the purpose of hazard identification in the context of safety assessment. However, the available knowledge suggests that the judicious use of an appropriate animal model could provide important information about the allergic potential of novel proteins. This paper provides an up-to-date review of the progress made in the field of development of in vivo models in this direction and the further goals that have to be achieved.

In vitro digestion of Cry1Ab proteins and analysis of the impact on their immunoreactivity

A pepsin resistance test performed at pH 1.2 and with high pepsin to protein ratio is one of the steps of the weight-of-evidence approach used for assessment of allergenicity of new proteins. However, the use of other in vitro digestibility tests, performed in more physiologically relevant conditions and in combination with immunological assays so as to increase the value of the information gained from the studies of stability of a novel protein to digestion for the overall allergenicity assessment, has been proposed. This study then aimed to investigate the stability to digestion of Cry1Ab protoxin and toxin, insecticidal proteins expressed in genetically modified crops, using simulated gastric fluid (SGF) at different pH values and pepsin-to-substrate ratios, in the presence or absence of physiological surfactant phosphatidylcholine (PC). Electrophoresis and immunoblot patterns and residual immunoreactivity of digesta were analyzed. Although Cry1Ab protoxin is extensively degraded at pH 1.2 with high pepsin-to-protein ratio, it is only slightly degraded at pH 2.0 and conserved its immunoreactivity. Furthermore, Cry1Ab proteins were demonstrated to be stable in a more physiologically relevant in vitro digestibility test (pH 2.5, pepsin-to-substrate ratio 1:20 (w/w) with PC). Factors such as pH, SGF composition, and pepsin-to-substrate ratio then greatly influence the digestion of Cry1Ab proteins, confirming that new and more physiologically relevant in vitro digestibility tests should be also considered to study the relationship between the resistance of a protein to digestion and its allergenicity.

Block copolymers have differing adjuvant effects on the primary immune response elicited by genetic immunization and on further induced allergy

Block copolymers were recently used to promote gene delivery in various tissues. Using a plasmid encoding a food allergen, bovine beta-lactoglobulin (BLG), we studied the effects of block copolymers on gene expression levels and primary immune response and on further induced allergy. Block copolymers (i.e., Tetronic 304, 908, and 1107) and various quantities of DNA were injected into the tibialis muscles of BALB/c mice. The BLG levels in injected muscle and the BLG-specific induced immune response were analyzed after injection. DNA-immunized mice were further experimentally sensitized with BLG, and the effects of block copolymer and DNA doses on allergic sensitization and elicitation were compared. Tetronic 304 induced a 12-fold increase in BLG production, while Tetronic 1107 increased the duration of BLG expression. Different Th1 primary specific immune responses were observed, either strong humoral and cellular (304), only cellular (1107), or weak cellular and humoral (908) responses. After BLG sensitization, increased BLG-specific IgG2a production was observed in all groups of mice independently of the presence and nature of the block copolymer. Increased BLG-specific IgG1 production was also detected after sensitization, except with Tetronic 1107. Compared with naked DNA, Tetronic 304 was the only block polymer that decreased BLG-specific IgE concentrations. However, after allergen challenge, Tetronic 1107 was the only block copolymer to reduce eosinophils and Th2 cytokines in bronchoalveolar lavage (BAL) fluid. Tetronic 304 amplified local inflammation. Each block copolymer elicited a different immune response, although always Th1 specific, in BALB/c mice.

Selection of recombinant IgE antibodies binding the beta-lactoglobulin allergen in a conformation-dependent manner

Cow's milk allergy (CMA) is a common food allergy, especially among infants and young children. Approximately 85% of milk-allergic children outgrow their allergy by the age of three but the remaining 15% remain allergic. Bovine beta-lactoglobulin (BLG) is one of the major allergens in cow's milk. There is a definite need for the specific and sensitive detection of allergenic substances. Validated methods are obligatory to demonstrate allergen contamination and even fatal hidden allergens and, thus, to prevent life-threatening conditions of allergic persons. In this study, we constructed human IgE scFv libraries from an adult milk-allergic patient and isolated the first recombinant IgE antibodies specific to a food allergen, BLG. The selection of the IgE antibody libraries with two distinct panning procedures resulted in the enrichment of four clones having different BLG-binding profiles; two of the clones recognize the native BLG whereas the other two recognize only the heat-denatured form of BLG. For further characterization, the scFv fragments were converted to Fab fragments with human IgG1 isotype. The D1 Fab fragment, binding native BLG with nanomolar affinity, also partially inhibited serum IgE binding to BLG. These BLG-specific IgE antibodies can be applied for the detection of both native and denatured BLG in cow's milk products and furthermore, for the optimization of manufacturing processes to develop safe hypoallergenic milk products.

Inter-laboratory comparisons of assessment of the allergenic potential of proteins in mice

Assessment of the potential allergenicity of novel proteins, including those expressed in genetically modified plants, is an important issue. In previous studies, we have shown that the IgE measurement induced by systemic exposure of BALB/c mice to a range of proteins correlates broadly with what is known of their allergenic potential in humans. The approach used a homologous passive cutaneous anaphylaxis (PCA) assay that reflects IgE-dependent biological activity and is of sufficient sensitivity to detect IgE production in the absence of adjuvant. In previous studies, the immunization phase was conducted independently in two separate facilities, and the subsequent analytical work (PCA) conducted in a single facility. The purpose here was to further evaluate the transferability of this approach. To this end, BALB/c mice were exposed to a range of doses of peanut agglutinin or ovalbumin, allergenic proteins of peanut and hen's egg, respectively, in two independent laboratories. Serial doubling dilutions of serum pooled for each treatment group were analyzed for specific IgE. At higher doses of allergen very similar, or identical, IgE titers were achieved in both laboratories, although at lower doses, responses were somewhat more variable. These data demonstrate that, although technically demanding, the measurement of protein allergen-induced IgE antibody production in mice using PCA is relatively robust and is transferable and reproducible between laboratories. This approach may provide a useful tool for the safety assessment of novel proteins and suggests that continued evaluation of the approach with a wider range of protein allergens and non-sensitising proteins is justified.