In vitro lymphocyte proliferation with milk and a casein-whey protein hydrolyzed formula in children with cow's milk allergy

Health Implications of Bioactive Peptides: A Review

Abstract. Today, due to immobility, improper food habits, and changes in lifestyle, communities are faced with an increase in health problems such as blood pressure, cholesterol, diabetes, and thrombosis. Bioactive peptides are considered as being the main products of protein hydrolysis which exert high effects on the nervous, immune, and gastrointestinal systems. Unlike synthetic drugs, bioactive peptides have no side effects and this advantage has qualified them as an alternative to such drugs. Due to the above-mentioned properties, this paper focuses on the study of health-improving attributes of bioactive peptides such as anti-oxidative, anti-hypertensive, immunomodulatory, anti-microbial, anti-allergenic, opioid, anti-thrombotic, mineral-binding, anti-inflammatory, hypocholesterolemic, and anti-cancer effects. We also discuss the formation of bioactive peptides during fermentation, the main restrictions on the use of bioactive peptides and their applications in the field of functional foods. In general, food-derived biologically active peptides play an important role in human health and may be used in the development of novel foods with certain health claims.

Gastrointestinal food allergy in infants

Food allergies are classified into three types, "IgE-mediated," "combined IgE- and cell-mediated" and "cell-mediated/non-IgE-mediated," depending on the involvement of IgE in their pathogenesis. Patients who develop predominantly cutaneous and/or respiratory symptoms belong to the IgE-mediated food allergy type. On the other hand, patients with gastrointestinal food allergy (GI allergy) usually develop gastrointestinal symptoms several hours after ingestion of offending foods; they belong to the cell-mediated/non-IgE-mediated or combined IgE- and cell-mediated food allergy types. GI allergies are also classified into a number of different clinical entities: food protein-induced enterocolitis syndrome (FPIES), food protein-induced proctocolitis (FPIP), food protein-induced enteropathy (Enteropathy) and eosinophilic gastrointestinal disorders (EGID). In the case of IgE-mediated food allergy, the diagnostic approaches and pathogenic mechanisms are well characterized. In contrast, the diagnostic approaches and pathogenic mechanisms of GI allergy remain mostly unclear. In this review, we summarized each type of GI allergy in regard to its historical background and updated clinical features, offending foods, etiology, diagnosis, examinations, treatment and pathogenesis. There are still many problems, especially in regard to the diagnostic approaches for GI allergy, that are closely associated with the definition of each disease. In addition, there are a number of unresolved issues regarding the pathogenic mechanisms of GI allergy that need further study and elucidation. Therefore, we discussed some of the diagnostic and research issues for GI allergy that need further investigation.

Memory T cell proliferation in cow's milk allergy after CD25+ regulatory T cell removal suggests a role for casein-specific cellular immunity in IgE-mediated but not in non-IgE-mediated cow's milk allergy

BACKGROUND

Previously reported increased lymphocyte proliferative responses in cow's milk allergy (CMA) may have been influenced by the lipopolysaccharides (LPS) which contaminate most commercial cow's milk protein (CMPs). Moreover, peripheral blood mononuclear cells (PBMC) contain both B cells, CD45RA+ naïve T cells, CD25+ regulatory T cells (Tregs) in addition to antigen-specific CD45RA- memory T cells.

METHODS

PBMC from clinically reactive and tolerised patients with IgE- and non-IgE-mediated CMA were depleted of CD45RA+ T cells and putative CD25+ Tregs. The proliferative index to LPS-depleted alpha-, beta- and kappa-casein and beta-lactoglobulin was compared in the memory T-cell-enriched, Treg-depleted PBMC and in bulk PBMC.

RESULTS

Clinically reactive IgE-mediated CMA patients had increased responses to caseins only. Tolerised patients, particularly those with atopic dermatitis, had decreased responses to kappa-casein which were restored after Treg depletion. Interleukin-4 and interferon-gamma were generally not detected in the culture supernatants. No differences were seen between reactive and tolerant delayed non-IgE-mediated CMA patients.

CONCLUSIONS

Proliferative responses to alpha-, beta- and kappa-caseins (but not beta-lactoglobulin) were observed in clinically reactive IgE-mediated CMA patients only. A markedly decreased proliferative response to kappa-casein in tolerised IgE-mediated CMA patients with atopic dermatitis, which was abrogated by Treg depletion, suggested a role for kappa-casein in tolerance induction. Non-IgE-mediated CMA patients had no increased proliferative response to any milk proteins.

T lymphocytes in food allergy: overview of an intricate network of circulating and organ-resident cells

Although food hypersensitivity might be divided in IgE- and non-IgE mediated food allergy, there is a large body of evidence implicating T lymphocytes overall in the pathogenesis of food allergy. Priming of naive T cells will occur mainly in Peyer's patches (PP), where surface receptors (l-selectin, CCR7 and CXCR4) will help to initiate diapedesis of the cells to the submucosa. Various antigen-presenting cells (e.g. dendritic cells, M cells) will present food antigen-derived epitopes and initiate either non-responsiveness, or a food-mediated immune response. Food-specific memory T cells express various surface receptors such as the alpha4beta7-integrin, or the cutaneous lymphocyte antigen. It is speculated, that they might also express specific chemokine receptors (CCR4, CCR7 or CCR9). Organ-specific homing will be facilitated through the corresponding receptors (i.e. MAdCAM-1 in the gut, VCAM-1 or fibronectin in other mucosal organs, or E-selectin in the skin). Locally secreted chemokines might help to attract T cells through their corresponding chemokine receptors. Finally, potential T-cell directed therapeutic interventions (peptide-derived immunotherapy, DNA vaccination, or strategies preventing T cells from trafficking to target organs) are discussed.

Food protein-induced enterocolitis syndrome: laboratory perspectives

The expression of food protein allergy in man is very heterogeneous, varies with the age of the subject and is to a certain extent genetically determined. Skin prick tests with standardized food extracts are a sensitive method for detection of immunoglobulin E bound to reactive cells such as mast cells. Various tests on cellular immunity have been developed, especially because T-cell mediated reactions are considered to play a role in mainly delayed gastrointestinal reactions to cow's milk proteins. Food allergy may involve the entire gut, from mouth to rectum, including the esophagus. Abnormalities in intestinal permeability are the hallmarks of the inflamed gut, and may contribute to diagnosis of food induced enteropathy. What determines the characteristics of the intestinal inflammatory response is largely the cytokine responses triggered by the pathologic mechanism, whatever its origin, in the stomach, the small intestine, and the colon. A so-called T-helper type 2 response is characteristic of the allergic subject. A secretion of tumor necrosis factor-alpha alpha by blood cells of children allergic to milk was shown. All means of investigation may help in analyzing food substitutes for allergic infants.

The time-course of milk antigen-induced TNF-alpha secretion differs according to the clinical symptoms in children with cow's milk allergy

BACKGROUND

TNF-alpha secretion by blood mononuclear cells stimulated with cow's milk proteins is significantly higher in infants with active cow's milk allergy (CMA) manifested by digestive symptoms than in children who have recovered from CMA.

OBJECTIVE

The current study was undertaken to analyze the kinetics of TNF-alpha secretion and to evaluate the usefulness of the measurement of TNF-alpha release in whole blood cultures in the prediction of clinical outcome after milk challenge.

METHODS

Blood samples were obtained from 83 children maintained on a cow's milk-free diet and examined just before a cow's milk provocation. Children were divided into 4 groups according to clinical outcome: group I (active CMA with cutaneous symptoms), group II (active CMA with predominantly digestive symptoms), group III (children recovered from CMA), and group IV (control). The kinetics of TNF-alpha secretion was measured in blood cultured for 1 to 5 days at different cow's milk protein concentrations.

RESULTS

On day 1 TNF-alpha secretion was significantly higher in group I (485 [453] pg/mL, mean [SD], P <.005) and in group II (269 [102] pg/mL, P <. 005) than that observed in groups III and IV (149 [95] and 87 [71] pg/mL, respectively). Then TNF-alpha was rapidly degraded and a second peak of secretion was observed on day 5 but only in group II (278 [221] pg/mL), whereas in groups I, III, and IV a low secretion was observed (70 [61], 45 [40], and 11 [12] pg/mL, respectively, P <. 02).

CONCLUSION

These results show that the pattern of TNF-alpha secretion in response to cow's milk proteins is different in CMA infants with cutaneous or digestive symptoms and suggest that TNF-alpha release might predict clinical relapse on challenge.

Prevention and management of food allergy

The phenotypic expression and natural history of food allergy vary widely according to the patient's age, disease presentation and type of offending food. Prevention of food allergy might be achieved by altering the dietary factors responsible for the sensitization and phenotypic expression of the disease. Owing to the peculiarity of the atopic status, a minute amount of allergens can trigger both sensitization and symptoms in atopic individuals. The oral dose of beta-lactoglobulin causing sensitization can be estimated to be between 1 ng and several milligrams. In food allergy, sensitization and treatment are allergen specific; therefore, for primary prevention (avoiding sensitization) and secondary prevention of food allergy (avoiding symptoms in an already sensitized subject), a product without immunogenic and allergenic epitopes should be given in each case. Babies of atopic parents are particularly prone to develop food allergy and for this reason they are called high-risk babies. Cow's milk is the most commonly offending food in both gastrointestinal and cutaneous manifestations. Cow's milk proteins are potent allergens and around 2.5% of infants experience cow's milk allergy in the first years of life. The major risk factors for cow's milk allergy are positive family history of atopy and early exposure to cow's milk proteins. Hydrolysate formulae have been developed for the purpose of reducing the allergenicity of cow's milk proteins. More recently, partially and extensively hydrolysed formulae have also been used for feeding babies with a high risk of atopy for the prevention of cow's milk allergy. However, according to the results of a recent randomized controlled study, only an extensively hydrolysated formula, and not a partially hydrolysated formula, significantly decreased the prevalence of cow's milk allergy.

Evaluation of the impact of food technology on the allergenicity of cow's milk proteins

The quantitative evaluation of the allergenicity of food proteins and the clinical tolerance towards antigens are problems the food industry and the clinicians have to face. The allergenicity of a protein depends on multiple factors, including the stability to digestion and the interaction with the intestinal environment. In addition to the possible reduction in allergenicity by technological treatments such as heat and enzymic hydrolysis, the complex interactions existing between the antigens, the intestinal epithelium and the underlying immune system, as well as the individual susceptibility to the sensitizing epitopes, have to be taken into account. Indeed, the intestinal cells are able to take up and process proteins, and possibly to present them directly to mucosal lymphocytes. On the other hand, pathophysiological conditions can modify the interactions between food antigens and the immune system. A large number of methods has been developed to assess the residual antigenicity of food proteins, based on the various immune responses leading to intestinal or extradigestive pathologies. Thus, the difficulty in measuring the residual allergenicity of hypoallergenic formulas is partly due to the physiology of the gastrointestinal tract, since an intricate network of interactions between enterocytes and immune cells governs the development of the immune response to food antigens.

The mucosal adhesion receptor alpha4beta7 integrin is selectively increased in lymphocytes stimulated with beta-lactoglobulin in children allergic to cow's milk

BACKGROUND

It has been shown in mice that the integrin alpha4beta7 directs the migration of memory T cells into the gut-associated lymphoid tissue. However, little is known about T-cell homing mechanisms in children with food allergies.

OBJECTIVE

We investigated the expression of this and other integrins in children with different manifestations of cow's milk allergy (urticaria, atopic dermatitis, and wheezing).

METHODS

PBMCs were stimulated with beta-lactoglobulin, 1 of the major allergenic proteins in cow's milk, and tetanus toxoid. Integrin expression was studied by flow cytometric analysis after 1 week of culture.

RESULTS

We found significantly higher expression of the alpha4beta7 integrin in cells from patients compared with control subjects with no allergies (P =. 005) when beta-lactoglobulin was used to stimulate the cells. alpha4beta7 integrin was also expressed at significantly higher levels in beta-lactoglobulin-stimulated cells than in tetanus toxoid-stimulated cells (P =.005). The alphaEbeta7 and the alpha4beta1 integrins were not upregulated by allergen stimulation. Most alpha4beta7 integrin-expressing cells were identified as CD4(+) T cells.

CONCLUSION

These results show that alpha4beta7 integrin expression after stimulation with beta-lactoglobulin correlates with the presumptive site of cow's milk sensitization (ie, the gut-associated lymphoid tissue but not with the site of symptoms of cow's milk allergy).

Cord blood mononuclear cells and milk-specific T-cell clones are tools to evaluate the residual immunogenicity of hydrolyzed milk formulas

BACKGROUND

Hydrolyzed milk formulas (HFs) are given to infants allergic to cow's milk proteins and, for preventive reasons, to atopy-prone newborns for which breast feeding is not feasible. The ultimate properties of HFs are not only a reduced allergenicity but also decreased immunogenic capacity combined with good taste and caloric value. No information is available concerning the capacity of HFs to induce immune responses.

OBJECTIVE

We sought to determine the residual immunogenic capacity of partially (pHF) and extensively hydrolyzed milk formula (eHF), and we studied the cellular reactivity of cord blood-derived (n = 71) mononuclear cells induced by 10 different HFs.

METHODS

To test the effect of HF on T-helper cells, beta-casein-specific T-cell clones (TCCs, n = 21) from individuals allergic to milk were established, and T-cell proliferation and cytokine profiles (interferon-gamma and IL-4) were determined on stimulation with HF.

RESULTS

We found significantly reduced proliferative responses of eHF compared with milk proteins. Whey-based pHF displayed the same proliferative capacity as unmodified milk proteins. As expected, extensively processed whey products displayed lower cellular responses compared with partially hydrolyzed products (pHF whey vs eHF whey, p < 0.0001). No difference in cellular response was found between casein-based pHF and casein-based eHF. Beta-casein-specific TCCs (n = 21) proliferated in response to casein-derived hydrolysates (14% with casein/whey-based pHF, 4% with casein-based pHF, and 0% with casein-based eHF). Whey-based pHF was also found to induce proliferation in beta-casein-specific TCCs, indicating the presence or the generation of peptides displaying cross-reactivity with these whey-derived hydrolysates. TCCs stimulated with whey- or casein-based pHF or eHF produced the same amount of cytokines (IL-4, interferon-gamma) as the same clones stimulated with unmodified products.

CONCLUSION

Our data indicate that whey- and casein-derived eHFs display highly reduced immunogenic properties at the T-cell level. In contrast, pHFs display residual immunogenic properties detectable at the T-cell level, reflecting a potential for the induction of pathogenetically important T-cell responses.

Evaluation of the usefulness of lymphocyte proliferation assays in the diagnosis of allergy to cow's milk

BACKGROUND

The significance of cell-mediated mechanisms in IgE-mediated milk allergy (IgE-MA) and in milk-induced enterocolitis syndrome (ME) is controversial. Some investigators have claimed that lymphocyte proliferation assays are useful in the diagnosis of food hypersensitivity, despite the great variability in study designs and results reported. This study was undertaken to address many of these variables and to determine whether lymphocyte proliferation assays correlate with clinical diagnoses.

METHODS

Lymphocyte proliferative responses to milk antigen were evaluated in two groups of children, 27 with IgE-MA, and nine with ME and in 21 pediatric control subjects. IgE-mediated food allergy was documented by positive double-blind, placebo-controlled food challenges and positive skin prick test results. ME was diagnosed by oral challenge or by a history of repeated episodes of delayed vomiting (>2 hours) after ingestion of milk and by negative skin prick test responses. Peripheral blood mononuclear cells were isolated and cultured. Cultures stimulated with milk (the food antigen of interest), soy antigen (a nonrelevant food antigen), or tetanus antigen (a positive control antigen) and unstimulated controls were performed in quadruplicate. On days 5, 7, and 9, cells were pulsed with tritium-labeled thymidine and incubated for 4 hours. Results were compared as counts per minute (cpm) and as stimulation indices (SIs).

RESULTS

Maximal proliferation was generally seen on day 7. The median cpm (20,941) and the median SI (19.2) in response to milk antigen in the 27 children with IgE-MA were significantly greater than those in the control patients (6969 cpm; SI = 14.2; p = 0.001 and p < 0.05, respectively). However, the ranges were large and overlapped extensively (IgE-MA, 5616 to 52,053 cpm; controls, 469 to 39,260 cpm). The non-soy-allergic patients with IgE-MA also had a significantly greater response to soy antigen than did the control subjects when cpm were compared (0.01 < p < 0.05). There were no differences in background or in response to tetanus antigen. The median response to milk in the patients with ME (11,975 cpm) was significantly greater than that in control subjects (6969 cpm; 0.01 < p < 0.05), when cpm were compared but not when SIs were compared. There were no significant differences between the patients with IgE-MA and those with ME.

CONCLUSION

Overall, these results indicate that lymphocyte proliferation assays are neither diagnostic nor predictive of clinical reactivity in individual patients with milk allergy. Lymphocytes of many control patients are highly responsive to milk antigens, and lymphocytes of many patients with milk allergy are not. Statistically significant differences are only evident when the patients are compared as groups.

[Nutritional physiology of whey and whey components]

Deriving from positive effects of whey drinking cures in antiquity, the Middle Ages and modern time, a review is given on nutritional significance of whey. The proteins are essential components of whey and belong to the proteins with highest biological value because of their amino acid composition. Besides, they show fundamental functional properties, which enable a varied application in foods, dietetic foods and beverages in form of different whey products (powder, protein concentrates and isolates). Whey proteins have found considerable usage in infant's nutrition as whey predominant formulas as well as whey protein hydrolysates in case of cow's milk protein intolerances. A recent field of research are biological active peptide sequences which become effective during digestion and are of importance for secretion of entero hormones as well as for immune enhancing effects. They may contribute to assess the biological value of whey proteins under enlarged points of view and to develop new application forms and areas. It is pointed to further fields of application (e.g. adipositas, gout, kidney insufficiency). Concerning the quantitatively most dominant lactose in whey, it is dealt with its importance for the healthy development of infants (adaptation to the increased lactose content of mother's milk) as well as with lactose intolerance and galactosaemia. In case of mineral salts of whey it is emphasized the high nutrient density of calcium (prophylaxis for osteoporosis), the beneficial Ca:P and Na:K proportions (antihypertensive in case of the last one), the promotion of absorption of mineral salts by lactose, and the high content of iodine. The whey is rich in B-vitamins, which contribute essentially for their satisfaction or requirement in case of a corresponding consumption. To be emphasized is the vitamin B12 in milk and whey, which is the sole source of this indispensable nutrient for blood-formation and cell division in lacto-ovo-vegetarian nutrition. In conclusion, a summarizing dietetics valuation of whey is performed.