Eva Untersmayr

Antacid medication inhibits digestion of dietary proteins and causes food allergy: A fish allergy model in balb/c mice

BACKGROUND Digestible proteins were supposed to be irrelevant for oral sensitization and induction of food allergy. Approximately 10% of the adult population uses antacids for the treatment of dyspeptic disorders, drugs that hinder peptic digestion. In these patients, proteins that are normally degradable might act as food allergens. OBJECTIVE We aimed to study the influence of antacid intake on the allergenicity of dietary proteins, taking sturgeon caviar and parvalbumin, the major fish allergen, as examples. METHODS Caviar proteins and recombinant parvalbumin from carp, rCyp c 1, were applied for intragastric feedings with or without the antacids sucralfate, ranitidine or omeprazole, using a Balb/c mouse model. RESULTS Both caviar proteins and parvalbumin were rapidly degraded in an in vitro digestion assay at pH 2.0, but not at pH 5.0, imitating the effect of antacids. The groups fed with caviar in combination with ranitidine hydrochloride intramuscularly or sucralfate orally had significant levels of caviar-specific IgE antibodies (P <.01), T-cell reactivity, and elevated counts of gastrointestinal eosinophils and mast cells. Food allergy in these groups was further evidenced by oral provocation tests and positive immediate-type skin reactivity. In contrast, feedings with caviar alone led to antigen-specific T-cell tolerance. None of the groups showed immune reactivity against the daily mouse diet. As a proof of the principle, feeding mice with parvalbumin in combination with ranitidine or omeprazole intramuscularly induced allergen-specific IgE antibodies (P <.05). CONCLUSIONS When antacid medication impairs the gastric digestion, IgE synthesis toward novel dietary proteins is promoted, leading to food allergy.

The role of protein digestibility and antacids on food allergy outcomes

Digestion assays with simulated gastric fluid have been introduced for characterization of food proteins to imitate the effect of stomach proteolysis on dietary compounds in vitro. By using these tests, dietary proteins can be categorized as digestion-resistant class 1 (true allergens triggering direct oral sensitization) or as labile class 2 allergens (nonsensitizing elicitors). Thus the results of these digestion assays mirror situations of intact gastric proteolysis. Alterations in the gastric milieu are frequently experienced during a lifetime either physiologically in the very young and the elderly or as a result of gastrointestinal pathologies. Additionally, acid-suppression medications are frequently used for treatment of dyspeptic disorders. By increasing the gastric pH, they interfere substantially with the digestive function of the stomach, leading to persistence of labile food protein during gastric transit. Indeed, both murine and human studies reveal that antiulcer medication increases the risk of food allergy induction. Gastric digestion substantially decreases the potential of food proteins to bind IgE, which increases the threshold dose of allergens required to elicit symptoms in patients with food allergy. Thus antiulcer agents impeding gastric protein digestion have a major effect on the sensitization and effector phase of food allergy.

Anti-ulcer drugs promote IgE formation toward dietary antigens in adult patients

Recently, we have demonstrated that anti‐ulcer drugs, such as H2‐receptor blockers and proton pump inhibitors, promote the development of immediate type food allergy toward digestionlabile proteins in mice. The aim of this study was to examine the allergological relevance of these findings in humans. In an observational cohort study, we screened 152 adult patients from a gastroenterological outpatient clinic with negative case histories for atopy or allergy, who were medicated with H2‐receptor blockers or proton pump inhibitors for 3 months. IgE reactivities to food allergens before and after 3 months of anti‐acid treatment were compared serologically. Ten percent of the patients showed a boost of preexisting IgE antibodies and 15% de novo IgE formation toward numerous digestion‐labile dietary compounds, like milk, potato, celery, carrots, apple, orange, wheat, and rye flour. Thus, the relative risk to develop food‐specific IgE after anti‐acid therapy was 10.5 (95% confidence interval: 1.44–76.48). The long‐term effect was evaluated 5 months after therapy. Food‐specific IgE could still be measured in 6% of the patients, as well as significantly elevated serum concentrations of ST2, a Th2‐specific marker. An unspecific boost during the pollen season could be excluded, as 50 untreated control patients revealed no changes in their IgE pattern. In line with our previous animal experiments, our data strongly suggest that anti‐ulcer treatment primes the development of IgE toward dietary compounds in long‐term acid‐suppressed patients.

Gender-medicine aspects in allergology.

Despite the identical immunological mechanisms activating the release of mediators and consecutive symptoms in immediate‐type allergy, there is still a clear clinical difference between female and male allergic patients. Even though the risk of being allergic is greater for boys in childhood, almost from adolescence onwards it seems to be a clear disadvantage to be a woman as far as atopic disorders are concerned. Asthma, food allergies and anaphylaxis are more frequently diagnosed in females. In turn, asthma and hay fever are associated with irregular menstruation. Pointing towards a role of sex hormones, an association of asthma and intake of contraceptives, and a risk for asthma exacerbations during pregnancy have been observed. Moreover, peri‐ and postmenopausal women were reported to increasingly suffer from asthma, wheeze and hay fever, being even enhanced by hormone replacement therapy. This may be on account of the recently identified oestradiol‐receptor‐dependent mast‐cell activation. As a paradox of nature, women may even become hypersensitive against their own sex hormones, resulting in positive reactivity upon intradermal injection of oestrogen or progesterone. More importantly, this specific hypersensitivity is associated with recurrent miscarriages. Even though there is a striking gender‐specific bias in IgE‐mediated allergic diseases, public awareness of this fact still remains minimal today.

Allergen‐loaded biodegradable poly(d,l‐lactic‐co‐glycolic) acid nanoparticles down‐regulate an ongoing Th2 response in the BALB/c mouse model

Background and objective Biocompatible and biodegradable microparticles have gained interest as antigen delivery systems during the recent years. We investigated whether biodegradable poly(d,l‐lactic‐co‐glycolic) acid (PLGA) nanospheres could be used as allergen vehicles for few‐shot therapy of type I allergy.

Dose-dependent food allergy induction against ovalbumin under acid-suppression: A murine food allergy model

BACKGROUND Animal models are essential for analyzing the allergenic potential of food proteins and for investigating mechanisms underlying food allergy. Based on previous studies revealing acid-suppression medication as risk factor for food allergy induction, we aimed to establish a mouse model mimicking the natural route of sensitization in patients. METHODS The effect of acid-suppressing medication on murine gastric pH was assessed by intragastric pH measurements after two injections of a proton pump inhibitor (PPI). To investigate dose-dependency, mice were fed different concentrations of ovalbumin (OVA; 0.2, 0.5, 1.0, 2.5 or 5.0mg) either with or without anti-ulcer medication. Additionally, different routes of exposure (i.p. vs. oral) were compared in a second immunization experiment. Sera were screened for OVA-specific antibody titers (IgG1, IgG2a and IgE) in ELISA and RBL assay. Clinical reactivity was evaluated by measuring rectal temperature after oral challenge and by type I skin tests. RESULTS Two intravenous injections of PPI significantly elevated the gastric pH from 2.97 to 5.3. Only oral immunization with 0.2mg OVA under anti-acid medication rendered elevated IgG1, IgG2a and IgE titers compared to all other concentrations. Protein feeding alone altered antibody titers only marginally. Even though also i.p. immunizations induced high levels of specific IgE, only oral immunizations under anti-acids induced anaphylactic reactions evidenced by a significant decrease of body temperature. CONCLUSION Only low-dosage ovalbumin feedings under anti-acid medication resulted in IgE mediated food allergy. Based on this knowledge we have established a suitable food allergy model for further investigations of food adverse reactions.

Anti-ulcer treatment during pregnancy induces food allergy in mouse mothers and a Th2-bias in their offspring

The treatment of dyspeptic disorders with anti‐acids leads to an increased risk of sensitization against food allergens. As these drugs are taken by 30–50% of pregnant women due to reflux and heartburn, we aimed here to investigate the impact of maternal therapy with anti‐acids on the immune response in the offspring in a murine model. Codfish extract as model allergen was fed with or without sucralfate, an anti‐acid drug, to pregnant BALB/c mice during pregnancy and lactation. These mothers developed a codfish‐specific allergic response shown as high IgG1 and IgE antibody levels and positive skin tests. In the next step we analyzed whether this maternal sensi‐tization impacts a subsequent sensitization in the offspring. Indeed, in stimulated splenocytes of these off‐spring we found a relative Th2‐dominance, because the Thl‐ and T‐regulatory cytokines were significantly sup‐pressed. Our data provide evidence that the anti‐acid drug sucralfate supports sensitization against food in pregnant mice and favors a Th2‐milieu in their offspring. From these results we propose that anti‐acid treatment during pregnancy could be responsible for the increasing number of sensitizations against food allergens in young infants.—Schöll, I., Ackermann, U., Özdemir, C., Blümer, N., Dicke, T., Sel, S., Sel, S., Wegmann, M., Szalai, K., Knittelfelder, R., Untersmayr, E., Scheiner, O., Garn, H., Jensen‐Jarolim, E., Renz, H. Anti‐ulcer treatment during pregnancy induces food allergy in mouse mothers and a Th2‐bias in their offspring. FASEB J. 21, 1264–1270 (2007)

The effect of gastric digestion on food allergy

Purpose of review The role of the stomach as the primary location of protein digestion is very well recognized, leading to classification of proteins as digestion-resistant or digestion-labile. This review analyses the role of gastric digestion in food allergy. Recent findings Hindrance of gastric digestion by elevation of the gastric pH, the therapeutic goal of anti-ulcer medication, was recently shown to trigger food allergy via oral sensitization in a murine food allergy model. The relevance in humans was assessed in an observational study of 152 gastroenterological patients who were medicated with anti-ulcer drugs due to dyspeptic disorders. Twenty-five percent of all patients developed a boost or de-novo IgE formation towards regular constituents of the daily diet. The clinical relevance of the induced antibodies was confirmed by positive skin and oral-provocation tests. Moreover, the importance of gastric digestion was also proven for food-allergic patients, as the allergenicity of allergens were reduced up to a 10 000-fold by gastric digestion. Summary These recent studies indicate for the first time the important gate-keeping function of gastric digestion, both in the sensitization and the effector phases of food allergy.

Active induction of tumor-specific IgE antibodies by oral mimotope vaccination

A role of IgE antibodies in cancer surveillance has been implicated for a long time. Studies dealing with IgE antibodies directly targeted to tumor antigens have shown marked anticancer effects mediated by this antibody class. Thus, the basic function of IgE antibodies may be to control tumor growth. Thus far, cancer-specific IgE has only been applied passively. Consequently, the aim of this study was to establish an active vaccination protocol to induce tumor antigen-specific IgE antibodies, and to evaluate functional properties. We previously generated epitope mimics, so-called mimotopes, for the epitope recognized by the anti-HER-2 antibody trastuzumab. Upon i.p. immunizations, IgG antibodies with trastuzumab-like properties could be elicited. In the present study, we immunized BALB/c mice via the oral route with these trastuzumab mimotopes, under simultaneous neutralization and suppression of gastric acid. As shown in preceding experiments, this feeding regimen effectively induces Th2 immune responses. Oral immunizations with trastuzumab mimotopes under hypoacidic conditions indeed resulted in the formation of IgE antibodies towards the HER-2 antigen. Moreover, anti-HER-2 IgE-sensitized effector cells mediated SK-BR-3 target cell lysis in an antibody-dependent cytotoxicity assay. We conclude that directed and epitope-specific induction of IgE against tumor antigens is feasible with an oral mimotope vaccination regimen, and that these antibodies mediate anticancer effects.

Nitration of the Egg-Allergen Ovalbumin Enhances Protein Allergenicity but Reduces the Risk for Oral Sensitization in a Murine Model of Food Allergy

Background Nitration of proteins on tyrosine residues, which can occur due to polluted air under “summer smog” conditions, has been shown to increase the allergic potential of allergens. Since nitration of tyrosine residues is also observed during inflammatory responses, this modification could directly influence protein immunogenicity and might therefore contribute to food allergy induction. In the current study we have analyzed the impact of protein nitration on sensitization via the oral route. Methodology/Principal Findings BALB/c mice were immunized intragastrically by feeding untreated ovalbumin (OVA), sham-nitrated ovalbumin (snOVA) or nitrated ovalbumin (nOVA) with or without concomitant acid-suppression. To analyze the impact of the sensitization route, the allergens were also injected intraperitoneally. Animals being fed OVA or snOVA under acid-suppressive medication developed significantly elevated levels of IgE, and increased titers of specific IgG1 and IgG2a antibodies. Interestingly, oral immunizations of nOVA under anti-acid treatment did not result in IgG and IgE formation. In contrast, intraperitoneal immunization induced high levels of OVA specific IgE, which were significantly increased in the group that received nOVA by injection. Furthermore, nOVA triggered significantly enhanced mediator release from RBL cells passively sensitized with sera from allergic mice. Gastric digestion experiments demonstrated protein nitration to interfere with protein stability as nOVA was easily degraded, whereas OVA and snOVA remained stable up to 120 min. Additionally, HPLC-chip-MS/MS analysis showed that one tyrosine residue (Y107) being very efficiently nitrated is part of an ovalbumin epitope recognized exclusively after oral sensitization. Conclusions/Significance These data indicated that despite the enhanced triggering capacity in existing allergy, nitration of OVA may be associated with a reduced de novo sensitizing capability via the oral route due to enhanced protein digestibility and/or changes in antibody epitopes.