Decreased Histone Acetylation Levels at Th1 and Regulatory Loci after Induction of Food Allergy.

Immunoglobulin E (IgE)-mediated allergy against cow's milk protein fractions such as whey is one of the most common food-related allergic disorders of early childhood. Histone acetylation is an important epigenetic mechanism, shown to be involved in the pathogenesis of allergies. However, its role in food allergy remains unknown. IgE-mediated cow's milk allergy was successfully induced in a mouse model, as demonstrated by acute allergic symptoms, whey-specific IgE in serum, and the activation of mast cells upon a challenge with whey protein. The elicited allergic response coincided with reduced percentages of regulatory T (Treg) and T helper 17 (Th17) cells, matching decreased levels of H3 and/or H4 histone acetylation at pivotal Treg and Th17 loci, an epigenetic status favoring lower gene expression. In addition, histone acetylation levels at the crucial T helper 1 (Th1) loci were decreased, most probably preceding the expected reduction in Th1 cells after inducing an allergic response. No changes were observed for T helper 2 cells. However, increased histone acetylation levels, promoting gene expression, were observed at the signal transducer and activator of transcription 6 (Stat6) gene, a proallergic B cell locus, which was in line with the presence of whey-specific IgE. In conclusion, the observed histone acetylation changes are pathobiologically in line with the successful induction of cow's milk allergy, to which they might have also contributed mechanistically.

Identification of peptides with tolerogenic potential in a hydrolysed whey-based infant formula.

BACKGROUND: Failure to induce oral tolerance may result in food allergy. Hydrolysed cow's milk-based infant formulas are recommended in subjects with a high risk of developing allergic disease. Presentation of T cell epitopes is a prerequisite to generate regulatory T cells that could contribute to oral tolerance. OBJECTIVE: To investigate whether a specific hydrolysed whey-based infant formula contains peptides that function as T cell epitopes to support the development of oral tolerance to whey. METHODS: First, a novel liquid chromatography-mass spectrometry (LC-MS) method was developed to characterize ß-lactoglobulin-derived peptides present in a specific infant formula with a focus on region AA#13-48 of ß-lactoglobulin, which has previously been described to contain T cell epitopes with tolerogenic potential. Second, the formula was subjected to the ProImmune ProPresent® antigen presentation assay and MHC class II binding algorithm to identify relevant HLA-DRB1-restricted peptides. Third, identified peptides were tested on human cow's milk protein-specific T cell lines to determine T cell recognition. RESULTS: Thirteen peptides of minimal 9AAs long that overlap with AA#13-48 of ß-lactoglobulin were identified. Six of them were found across all batches analysed. It was further confirmed that these peptides were processed and presented by human dendritic cells. The identified HLA-DRB1-restricted peptides were correlated to AA#11-30 and AA#23-39 of ß-lactoglobulin. Importantly, the proliferation assay showed that the synthetic peptides were recognized by cow's milk protein-specific T cell lines and induced T cell proliferation. CONCLUSION AND CLINICAL RELEVANCE: This study demonstrates that the tested hydrolysed infant formula contains functional HLA-DRB1-restricted T cell epitopes, which can potentially support the development of oral tolerance to whey.

A Specific Mixture of Fructo-Oligosaccharides and Bifidobacterium breve M-16V Facilitates Partial Non-Responsiveness to Whey Protein in Mice Orally Exposed to ß-Lactoglobulin-Derived Peptides.

Oral tolerance is a promising approach for allergy prevention in early life, but it strongly depends on allergen exposure and proper immune environment. Small tolerance-inducing peptides and dietary immunomodulatory components may comprise an attractive method for allergy prevention in at-risk infants. This study aimed to investigate whether early oral exposure to ß-lactoglobulin-derived peptides (BLG-peptides) and a specific synbiotic mixture of short- and long- chain fructo-oligosaccharides (scFOS/lcFOS, FF) and Bifidobacterium breve (Bb) M-16V (FF/Bb) can prevent cow's milk allergy (CMA). Three-week-old female C3H/HeOuJ mice were orally exposed to phosphate buffered saline (PBS), whey protein, or a mixture of four synthetic BLG-peptides combined with a FF/Bb-enriched diet prior to intragastric sensitization with whey protein and cholera toxin. To assess the acute allergic skin response and clinical signs of allergy, mice were challenged intradermally with whole whey protein. Serum immunoglobulins were analyzed after a whey protein oral challenge. Cytokine production by allergen-reactivated splenocytes was measured and changes in T cells subsets in the spleen, mesenteric lymph nodes, and intestinal lamina propria were investigated. Pre-exposing mice to a low dosage of BLG-peptides and a FF/Bb-enriched diet prior to whey protein sensitization resulted in a significant reduction of the acute allergic skin response to whey compared to PBS-pretreated mice fed a control diet. Serum immunoglobulins were not affected, but anaphylactic symptom scores remained low and splenocytes were non-responsive in whey-induced cytokine production. In addition, preservation of the Th1/Th2 balance in the small intestine lamina propria was a hallmark of the mechanism underlying the protective effect of the BLG-peptides-FF/Bb intervention. Prior exposure to BLG-peptides and a FF/Bb-enriched diet is a promising approach for protecting the intestinal Th1/Th2 balance and reducing the allergic response to whole whey protein. Therefore, it might have implications for developing successful nutritional strategies for CMA prevention.

An Anti-EGFR IgA That Displays Improved Pharmacokinetics and Myeloid Effector Cell Engagement In Vivo.

Antibodies of IgA isotype effectively engage myeloid effector cells for cancer immunotherapy. Here, we describe preclinical studies with an Fc engineered IgA2m(1) antibody containing the variable regions of the EGFR antibody cetuximab. Compared with wild-type IgA2m(1), the engineered molecule lacked two N-glycosylation sites (N166 and N337), two free cysteines (C311 and C472), and contained a stabilized heavy and light chain linkage (P221R mutation). This novel molecule displayed improved production rates and biochemical properties compared with wild-type IgA. In vitro, Fab- and Fc-mediated effector functions, such as inhibition of ligand binding, receptor modulation, and engagement of myeloid effector cells for antibody-dependent cell-mediated cytotoxicity, were similar between wild-type and engineered IgA2. The engineered antibody displayed lower levels of terminal galactosylation leading to reduced asialoglycoprotein-receptor binding and to improved pharmacokinetic properties. In a long-term in vivo model against EGFR-positive cancer cells, improved serum half-life translated into higher efficacy of the engineered molecule, which required myeloid cells expressing human FcαRI for its full efficacy. However, Fab-mediated effector functions contributed to the in vivo efficacy because the novel IgA antibody demonstrated therapeutic activity also in non-FcαRI transgenic mice. Together, these results demonstrate that engineering of an IgA antibody can significantly improve its pharmacokinetics and its therapeutic efficacy to inhibit tumor growth in vivo.

Simultaneous Targeting of FcγRs and FcαRI Enhances Tumor Cell Killing.

Efficacy of anticancer monoclonal antibodies (mAb) is limited by the exhaustion of effector mechanisms. IgG mAbs mediate cellular effector functions through FcγRs expressed on effector cells. IgA mAbs can also induce efficient tumor killing both in vitro and in vivo. IgA mAbs recruit FcαRI-expressing effector cells and therefore initiate different effector mechanisms in vivo compared with IgG. Here, we studied killing of tumor cells coexpressing EGFR and HER2 by the IgG mAbs cetuximab and trastuzumab and their IgA variants. In the presence of a heterogeneous population of effector cells (leukocytes), the combination of IgG and IgA mAbs to two different tumor targets (EGFR and HER2) led to enhanced cytotoxicity compared with each isotype alone. Combination of two IgGs or two IgAs or IgG and IgA against the same target did not enhance cytotoxicity. Increased cytotoxicity relied on the presence of both the peripheral blood mononuclear cell and the polymorphonuclear (PMN) fraction. Purified natural killer cells were only cytotoxic with IgG, whereas cytotoxicity induced by PMNs was strong with IgA and poor with IgG. Monocytes, which coexpress FcγRs and FcαRI, also displayed increased cytotoxicity by the combination of IgG and IgA in an overnight killing assay. Coinjection of cetuximab and IgA2-HER2 resulted in increased antitumor effects compared with either mAb alone in a xenograft model with A431-luc2-HER2 cells. Thus, the combination of IgG and IgA isotypes optimally mobilizes cellular effectors for cytotoxicity, representing a promising novel strategy to improve mAb therapy.

Characterization of T cell epitopes in bovine α-lactalbumin.

BACKGROUND: Recent studies have indicated that peptides containing T cell epitopes may be used for immunotherapy. While for several cow's milk allergens the T cell epitopes have been described, the T cell epitopes in the major allergen α-lactalbumin (α-LAC) are unknown. Therefore, the aim of this study was to determine the T cell epitopes in α-LAC. METHODS: Nineteen synthetic peptides spanning α-LAC were obtained. Cow's milk-specific T cell lines (TCLs) of 46 subjects were generated and tested for their specificity for α-LAC. The lines responding to α-LAC were subsequently tested to determine their activation in response to the peptides. RESULTS: More than half of the TCLs generated did not respond to α-LAC or lost their responsiveness during subsequent experiments, which indicates that α-LAC has low immunogenicity. Only 8 TCLs recognized 1 or more peptides. The recognition of the peptides was diverse and no major epitopes could be defined. CONCLUSION: The immunogenicity of α-LAC is very low compared to other major allergens in cow's milk. Moreover, there seems to be no dominant epitope present in the protein. Therefore, it seems unlikely that peptides of this protein can be used for immunotherapy.

Oral treatment with ß-lactoglobulin peptides prevents clinical symptoms in a mouse model for cow's milk allergy.

BACKGROUND: Prior exposure to partial whey hydrolysates has been shown to reduce the allergic response to whey in mice. This effect was more pronounced in combination with a diet containing non-digestible oligosaccharides (scGOS/lcFOS/pAOS). It is unknown which fractions/epitopes are responsible for this effect. Therefore, the prophylactic ability of synthetic peptides of ß-lactoglobulin with/without a scGOS/lcFOS/pAOS-containing diet to reduce the allergic response in a mouse model for cow's milk allergy was investigated. METHODS: Of 31 peptides, nine peptides were selected based on human T cell data. Mice were pre-treated orally with three peptide mixtures or single peptides for six consecutive days. During this period, they received a control or scGOS/lcFOS/pAOS-containing diet. Subsequently, mice were orally sensitized to whey and received an intradermal and oral challenge. After sacrifice, serum and mesenteric lymph nodes (MLN) were collected for further analysis. RESULTS: Prior exposure to peptide mixtures 1 and 3 significantly reduced the acute allergic skin response to whey. Mixture 2 showed no effect. An additive effect of the scGOS/lcFOS/pAOS-containing diet was only observed for mixture 1. Of the peptides in mixture 1, one peptide (LLDAQSAPLRVYVEELKP) showed the strongest effect on the acute allergic skin response. This peptide also tended to decrease whey-specific antibody levels and to increase the percentages of CD11b+CD103+ dendritic cells and CD25+Foxp3+ T cells in the MLN. CONCLUSIONS: Prior exposure to specific peptides of ß-lactoglobulin reduces the allergic response to whey, which may involve regulatory dendritic and T cells. Combining peptides with a sGOS/lcFOS/pAOS-containing diet enhances this effect.

IgG antibodies in food allergy influence allergen-antibody complex formation and binding to B cells: a role for complement receptors.

Allergen-IgE complexes are more efficiently internalized and presented by B cells than allergens alone. It has been suggested that IgG Abs induced by immunotherapy inhibit these processes. Food-allergic patients have high allergen-specific IgG levels. However, the role of these Abs in complex formation and binding to B cells is unknown. To investigate this, we incubated sera of peanut- or cow's milk-allergic patients with their major allergens to form complexes and added them to EBV-transformed or peripheral blood B cells (PBBCs). Samples of birch pollen-allergic patients were used as control. Complex binding to B cells in presence or absence of blocking Abs to CD23, CD32, complement receptor 1 (CR1, CD35), and/or CR2 (CD21) was determined by flow cytometry. Furthermore, intact and IgG-depleted sera were compared. These experiments showed that allergen-Ab complexes formed in birch pollen, as well as food allergy, contained IgE, IgG1, and IgG4 Abs and bound to B cells. Binding of these complexes to EBV-transformed B cells was completely mediated by CD23, whereas binding to PBBCs was dependent on both CD23 and CR2. This reflected differential receptor expression. Upon IgG depletion, allergen-Ab complexes bound to PBBCs exclusively via CD23. These data indicated that IgG Abs are involved in complex formation. The presence of IgG in allergen-IgE complexes results in binding to B cells via CR2 in addition to CD23. The binding to both CR2 and CD23 may affect Ag processing and presentation, and (may) thereby influence the allergic response.