Evaluation by SDS-PAGE and immunoblotting of residual antigenicity in hydrolysed protein formulas

Food Allergens of Plant and Animal Origin: Classification, Characteristics, and Properties

Food allergy is an adverse immune response to specific foods that can be either IgE-mediated or non-IgE mediated. The causes of IgE-mediated food allergy are multifactorial and involve genetic, dietary, and environmental factors. The prevalence of food allergy has increased over the last few decades, especially in urbanized, industrialized, and Westernized countries, and the epithelial barrier hypothesis has been recently suggested as a possible explanation for this increase. Food allergens of plant and animal origin are classified into a few families and superfamilies that are widely distributed and conserved. While it is known that food allergens share common properties, such as stability to enzymes and solubility, they also exhibit differential properties, and exceptions to the common characteristics exist. In recent years, novel characteristics of food allergens have been proposed based on their immunological properties and their ability to act as adjuvants or enhancers of the immune system.This chapter provides an overview of the current knowledge of food allergy, covering their prevalence, classification of food allergens from plant and animal origins, and recent advancements in the characterization of the properties of these allergens.

Quantitative Determination of Whey Protein to Casein Ratio in Infant Formula Milk Powder

This study was aimed to establish a method for quantitatively determining the ratio of whey protein in the total protein of infant formula by respectively selecting two characteristic peptides from whey protein and casein and calculating the ratio between the characteristic peptides. A nanoliter high-performance liquid chromatography tandem high-resolution mass spectrometry (Q Exactive) was used to simultaneously detect the characteristic peptides of two main whey proteins and two main caseins. The characteristic peptides were calculated, predicted, and screened using the ExPASy website, and peptide information was confirmed by database retrieval after the analysis by using a high-resolution mass spectrometer. The matrix effect was compensated by comparing the characteristic peptides in whey protein with those in casein protein, in which isotope internal standards were not required. The influence of the changes of the protein content in whey protein and casein on the detection method was eliminated by the calculation formula designed by ourselves. In this detection method, the sample was stable in the total protein concentration range of between 0.1 and 0.4 mg/ml. In the simulated industrial processing environment, with desalted whey powder, the recovery rate was 98.63–113.33% under different spiked levels with good reproducibility (RSD<8%). The RSDs of intraday and interday precisions were 2.03–9.35% and 0.61–11.02%, respectively. The different processing procedures of samples had no significant impact on the detection of whey protein (RSD% for milk samples treated by different processing techniques was 2.97%). The quantitation method of whey protein was applied to evaluate the whey protein content in different brands of commercially available milk powder. In summary, the proposed method was applicable for quantitative analysis of whey proteins in the infant formula.

About the mechanism of ultrasonically induced protein capsule formation

In this paper, we propose a consistent mechanism of protein microcapsule formation upon ultrasound treatment. Aqueous suspensions of bovine serum albumin (BSA) microcapsules filled with toluene are prepared by use of high-intensity ultrasound following a reported method. Stabilization of the oil-in-water emulsion by the adsorption of the protein molecules at the interface of the emulsion droplets is accompanied by the creation of the cross-linked capsule shell due to formation of intermolecular disulfide bonds caused by highly reactive species like superoxide radicals generated sonochemically. The evidence for this mechanism, which until now remained elusive and was not proven properly, is presented based on experimental data from SDS-PAGE, Raman spectroscopy and dynamic light scattering.

A consistent mechanism of protein microcapsule formation upon ultrasound treatment is proposed. The evidence for this mechanism is based on experimental data from SDS-PAGE, Raman spectroscopy and dynamic light scattering.

Design, quality, safety and efficacy of extensively hydrolyzed formula for management of cow's milk protein allergy: What are the challenges?

Cow's milk protein allergy (CMPA) is one of the most common food allergies in infancy. Clinical food allergy guidelines recommend an extensively hydrolyzed formula (EHF) as the first-line treatment in nonbreastfed infants with CMPA. Designing and commercializing EHF poses both technical and regulatory challenges. Each manufacturing step, from sourcing of raw materials to release of the final product, needs to be managed in accordance with comprehensive quality systems. To avoid cross-contamination via externally sourced ingredients, suppliers should be carefully selected based on quality requirements. Strict zoning of the manufacturing areas according to contamination risk and air flow control are effective strategies to prevent accidental allergen contamination. Furthermore, dedicated manufacturing lines for hypoallergenic products are used to prevent potential cross-contamination from other products produced on the same line. The enzymatic hydrolysis, heat treatment and ultrafiltration used are specific to each manufacturer. Consequently, EHF are a heterogenous group of products with differences in the molecular weight profile of peptides, content of residual immunogenic cow's milk allergens, and residual in-vitro allergenicity. These differences are likely to affect clinical efficacy and safety. As not all commercialized EHF products have undergone formal testing in the laboratory and clinical trials, there is a need to develop guidelines for minimum technical and regulatory requirements for EHF products, including validated assays for ongoing quality control. Clinical trials assessing new EHF products for their hypoallergenicity and ability to support normal growth remain the definitive proof of efficacy and safety in infants and young children with CMPA.

Evaluation of a rapid serological test for leprosy classification using human serum albumin as the antigen carrier

The presence of anti-BSA antibodies may interfere in serological tests, as ELISA or immunochromatographic assays. BSA is frequently used as a blocking agent or as "inert" carrier of antigens, such as the NT-P-BSA, the semi-synthetic trisaccharide analogue of the PGL-I (phenolic glycolipid-I) antigen from the cell wall of the Mycobacterium leprae. PGL-I was prepared and linked to human serum albumin based in the hypothesis that replacing BSA by a human protein carrier would enhance the performance of leprosy serological tests. A total of 1162 serum samples were tested by ELISA and by the ML Flow rapid test using NT-P-BSA or NT-P-HSA antigens. When grouping leprosy patients as paucibacillary (PB) or multibacillary (MB) according to the Ridley & Jopling classification, ML Flow BSA and ML Flow HSA tests correctly allocated 70.9% and 68.6% of patients in the PB group, and 87% and 81% of patients in the MB group, respectively. Concordant results were found in 82.0% (953/1162) (kappa value=0.637; sd=0.023) of samples between ML Flow tests and 85.7% (996/1162) (kappa value=0.703; sd=0.021) between ELISA tests. ML Flow results were statistically similar and the same was true for ELISA tests using HSA or BSA. However, we noticed a tendency to decreased capacity to detect MB patients and an increased positivity among PB patients, HHC, TB patients and healthy controls by the HSA carrier in both ML Flow and ELISA. The PGL-I serology performed by the ML Flow test with BSA or HSA as antigen carriers can be a useful, friendly auxiliary tool to identify patients with higher bacterial load.

Characterization of the sensitization profile to lupin in peanut-allergic children and assessment of cross-reactivity risk

BACKGROUND

Case reports of allergy to lupin, due to primary sensitization or cross-reactions with other legumes, are increasing as a consequence of the augmented use of lupin flour in bakery, pasta formulations and other food items. The main allergens that have been associated with the sensitization to lupin are α- and β-conglutins and, to a lesser extent, γ- and δ-conglutin, but no conclusive data are available so far. The aim of this study was to characterize the sensitization pattern to lupin in a group of 12 Italian children allergic to peanut and identify the specific lupin proteins involved in the cross-reactivity with peanut.

METHODS

The immunochemical cross-reactivity among peanut and lupin was evaluated by both in vitro immunoblotting and in vivo fresh food skin prick test (FFSPT).

RESULTS

The results showed that β-conglutin was recognized by cutaneous IgEs from 7/12 peanut-allergic children in FFSPT and serum IgEs from 5/12 in immunoblotting, while 4/12 and 8/12 patients tested positive to γ-conglutin in FFSPT and immunoblotting, respectively. No significant immunoreactive responses were observed to α- and δ-conglutins under non-reducing conditions, but they were bound in FFSPT by the sera of 5/12 and 3/12 patients, respectively.

CONCLUSION

In this group of allergic children, β-conglutin has been identified as the major lupin allergen involved both in vitro and in vivo cross-reactivity with peanut proteins. The role of γ-conglutin in the cross-reactivity between lupin and peanut proteins was also relevant and clear, despite the observed unspecificity of the immunoblotting responses.

Good tolerance to goat's milk in patients with recurrent aphthous ulcers with increased immunoreactivity to cow's milk proteins

BACKGROUND

Recurrent aphthous ulcers (RAU) represent a very common, but poorly understood mucosal disorder. The connection between immunity to cow's milk proteins (CMP) and oral diseases was noted earlier. The goal of this study was to determine the prevalence of the increased levels of serum antibodies to goat's milk proteins (GMP), by enzyme-linked immunosorbent assay (ELISA) test, in subjects who have RAU and proven increased immunity to CMP.

METHODS

Fifty subjects with RAU (36 with proven increased immunity to CMP and 14 without this increased immunity) were included in this research. Levels of serum IgA, IgG, and IgE antibodies to the same quantity of the examined antigens were determined by ELISA. The statistical analysis of data was performed by Wilcoxon rank-sum test and Mann-Whitney test.

RESULTS

The levels of serum antifresh cow's milk IgA, IgG, and IgE antibodies were significantly higher than the levels of serum antifresh goat's milk, in subjects with RAU with proven increased immunoreactivity to CMP (P = 0.0003; P < 0.0001; P < 0.0001).

CONCLUSIONS

These results indicate that patients with RAU with increased immunity to CMP could consider the use of goat's milk as the alternative protein source.

Molecular diagnosis of cow's milk allergy

PURPOSE OF REVIEW

To identify and discuss studies on the molecular diagnosis of cow's milk allergy (CMA) with a view to update allergists since a general review of the methodology in 2006.

RECENT FINDINGS

Seven basic research studies reporting the use of component-resolved diagnostics in CMA were found. All studies were on children positively reacting to a formal challenge with cow's milk. Six studies used natural allergens and three used recombinant milk proteins. Microarray platforms were customized and, thus, differed across studies. Three studies assessed the association between molecular-scale patterns and different presentations of the condition, that is the association between anaphylaxis, gastrointestinal symptoms and other severe phenotypes and the pattern of protein sensitization. Two studies assessed the association between positive oral food challenge and the persistence of milk allergy over time. Protein profiling could be useful to indicate appropriate specific immunotherapy.

SUMMARY

Accurate diagnosis of CMA is challenging and essential. The determination of the immunoglobulin E (IgE)-mediated response to sequenced and characterized allergens may be more useful in predicting the presence and severity of clinical allergy than the currently used skin or blood tests performed with whole extracts. However, as component recognition pattern heterogeneity is observed in different areas, further clinical studies are essential to correlate useful molecular diagnostics and biological markers with disease and patient profiles. Until such markers are found and validated in different age groups, oral food challenge remains the reference standard for the diagnosis of CMA.

IgE-mediated cross-reactivity among leguminous seed proteins in peanut allergic children

The immunological cross-reactivity among major protein- and oil-crops, including lupin, lentil, pea, peanut, kidney bean and soybean, has been studied by a combination of in vitro and in vivo experimental approaches: SDS-PAGE separations of legume protein extracts and immuno-blot revelations with 12 peanut-sensitive subjects' sera, Immuno-CAP and Skin Prick tests on the same subjects. The immuno-blotting data showed a wide range of IgE-binding responses both displayed by one subject towards different plant extracts and among subjects. Differences were both quantitative and qualitative. The prevalent responses of most subjects' sera were seen with peanut polypeptides, as expected, as well as with various polypeptides of the other legumes, the most recurrent of which were the basic subunits of the 11S globulins. The distribution of in vivo responses generally paralleled those obtained by in vitro approaches with strong responses elicited by peanut, lentil and pea protein extracts, especially by most sensitive subjects, thus providing a consistent overall set of results. In this work, the comparison of various approaches has allowed us to get an overall broad picture of the immunological cross-reactivities among proteins of widely used different seed species and to hypothesize the role of most conserved specific polypeptides.

Molecular aspects of milk allergens and their role in clinical events

Milk allergy is the most frequent food allergy in childhood. Even though cases of newly developed milk allergy in adulthood are known, this allergy is less frequent in adults since it is normally outgrown by children during the first years of life. One of the reasons why allergy to cow's milk shows its highest prevalence in children is its early introduction into the diets of babies when breast feeding is not possible. The major allergens are caseins and beta-lactoglobulin, but allergies to other minor proteins (immunoglobulins, bovine serum albumin) have also been reported. Milk allergenicity can be reduced by various treatments (mainly hydrolysis), meaning that formulas based on cow's milk can often be safely fed to children allergic to milk proteins. Cross-reactivity has been described between different mammalian milks and between milk and meat or animal dander. Cross-contamination can result from inadequate cleaning of industrial equipment and constitutes a hidden danger for allergic subjects who unknowingly ingest milk proteins.

Evaluation of the residual antigenicity of dairy whey hydrolysates obtained by combination of enzymatic hydrolysis and high-pressure treatment

Dairy whey was hydrolyzed for 15 min with five food-grade enzymes (Alcalase, Neutrase, Corolase 7089, Corolase PN-L, and Papain) at atmospheric pressure (0.1 MPa) and in combination with high pressure (HP) at 100, 200, and 300 MPa, applied prior to or during enzymatic digestion. The peptide profile of the hydrolysates obtained was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and their residual antigenicity was assessed by immuno-blotting with anti-beta-lactoglobulin monoclonal antibodies and the sera from pediatric patients allergic to cow's milk proteins. Moreover, to evaluate the presence of residual trace amounts of casein in bovine whey hydrolysates, immunoblotting with anti-cow's milk protein polyclonal antibodies was performed. SDS-PAGE analysis showed that HP treatment increased hydrolysis by the proteases assayed, especially when it was applied during the enzymatic digestion. Positive reactions at the band corresponding to beta-lactoglobulin were detected for Corolase PN-L and Corolase 7089 hydrolysates, except for those obtained under 300 MPa by the last protease. However, the immunochemical reaction was lower in the hydrolysis products obtained under HP than in those obtained at atmospheric pressure and after the HP treatment. On the contrary, no residual immunochemical reactivity associated with beta-lactoglobulin was observed in the hydrolysates obtained by Alcalase and Neutrase under HP, and none was observed in any of the hydrolysis products obtained by Papain. The presence of traces of casein was not significant. These results suggest that HP combined with selected food-grade proteases is a treatment that can remove the antigenicity of whey protein hydrolysates for their use as ingredients of hypoallergenic infant formulae.

Effect of ingestion of cow's milk protein hydrolysate formulas on alpha-casein-specific immunoglobulin E and G1 antibody responses in naïve and sensitized mice

OBJECTIVES

Cow's milk protein hydrolysate formulas are widely used for genetically predisposed atopic infants. Whether hydrolysate formulas can induce oral tolerance to alpha-casein was studied for the first time in naive and sensitized mice.

METHODS

Using immunoblotting, residual antigenicity to alpha-casein was examined for in animals fed hydrolysate formulas. Naïve mice fed hydrolysate formulas for 1 to 4 weeks were later sensitized with alpha-casein. Another group of mice sensitized first with alpha-casein were then fed hydrolysate formulas continually for 12 weeks.

RESULTS

Oral tolerance measured by immunoglobulin (Ig)E and IgG1 antibody responses to alpha-casein was induced in naïve mice fed NAN for 1 week or NAN-HA for 4 weeks. IgE responses to alpha-casein were suppressed in mice fed NAN-HA for 1 week or Neoangelac FL for 4 weeks. In contrast, mice fed Alfare, Pepti-Junior, or Pregestimil for 1 to 4 weeks did not develop tolerance to alpha-casein. Antibody responses to alpha-casein were not significantly suppressed in sensitized mice fed NAN or hydrolysate formulas for 12 weeks.

CONCLUSIONS

Primary IgE responses to alpha-casein are readily suppressed in naïve mice first fed cow's milk formula or partially hydrolyzed formula for 1 week. Conversely, ongoing IgE, IgG1, and IgG antibody responses to alpha-casein are poorly suppressed in previously sensitized mice even after prolonged feeding of cow's milk formula or hydrolysate formulas.

Clinical tolerance of processed foods

OBJECTIVE

To review the effects of technological processing on selected foods of relevance to childhood allergy from the viewpoints of reduced allergenicity, contamination of processed foods by allergens introduced during processing, and ad hoc technologies to produce reduced hypoallergenic products.

DATA SOURCES

We searched the literature (PubMed/MEDLINE) for articles published between January 1994 and April 2004 using the following keywords: food allergy AND process* OR heat* OR cooking OR toleran*.

STUDY SELECTION

We drew on our collective clinical and biological experience to restrict retrieved studies to those of more frequent relevance to a hospital allergy practice.

RESULTS

Comparatively few clinical studies address the modification of allergenicity of food through cooking or processing. Dairy foods are largely unaffected by processing and may be contaminated by, or themselves become, hidden allergens. Hypoallergenic formulas based on milk, soy, or rice and homogenized beef are successful applications of allergenicity reduction via technological processing. Egg, fish, condiments, and vegetables all carry heat-resistant allergens and should also be considered contaminants. Cereals and bakery products are generally well tolerated, but their allergenicity may be enhanced by processing; the case of rice is still open. Peanut allergens are stable, and the evidence is scant that thermal processing affects the allergenicity of soybean and soy hydrolysates. The debate is ongoing about the tolerance of vegetable oils.

CONCLUSIONS

It is too early to systematize clinical studies based on single procedures. Processing affects antigenicity, but this does not always translate into safety recommendations. Industrial processing is liable to contamination, and monitoring and labeling are industry priorities. Clinicians should evaluate foods by as complete a workup as possible before recommending processed foods.

Tolerance of heat-treated kiwi by children with kiwifruit allergy

Kiwifruit allergy is increasing among children but whether heating affects clinical tolerance to kiwifruit is unknown. To assess tolerance to heated kiwifruit in children allergic to fresh kiwifruit. In this prospective trial, 20 children (median age 9.4 yr) with a history of immediate allergic reactions to fresh kiwifruit underwent double-blind placebo-controlled food challenges with steam-cooked (100 degrees C for 5') and industrially homogenised kiwifruit. Skin prick tests with a commercial kiwifruit allergen, raw kiwifruit and double-blind placebo-controlled food challenge with 25 g of fresh kiwifruit were used to confirm the history. Specific kiwifruit IgE to native and homogenized fruit were identified by immunoblotting. Fresh kiwifruit induced positive skin prick wheals in all children (confirmed during challenge in 19 patients). Commercial skin prick test elicited a positive response in five children, steam-cooked kiwifruit in five, and the homogenised kiwifruit preparation in none. UniCAP determinations were positive for kiwifruit in three patients. All children's sera showed specific IgE at immunoblotting with raw kiwifruit and one with the homogenised preparation (major allergens identified: Act c 1 and Act c 2). There was no clinical reactivity following challenge with homogenised kiwifruit but one child reacted to cooked kiwifruit challenge. Industrial heat treatment and homogenisation can make kiwifruit safe for children who are allergic to this increasingly popular fruit. This has dietary implications for children who are allergic to several fruit and vegetable proteins.

Characterization of bovine serum albumin epitopes and their role in allergic reactions

OBJECTIVE

This review provides updated information on conformational and sequential epitopes identified in bovine serum albumin (BSA) and summarizes available data about the role of structural modifications on BSA antigenicity/allergenicity.

DATA SOURCES

Data on beef allergy and BSA antigenicity are reported, with reference both to the basic literature and to clinical results obtained by our group.

RESULTS AND DISCUSSION

BSA is an important allergen involved in milk and beef allergy. The presence of conformational epitopes has been suggested by indirect evidence, while at least one sequential epitope has been experimentally identified. The role of structural modifications on BSA antigenicity is discussed as well as the increased tolerance observed in allergic subjects consuming beef as strained (homogenized) and freeze-dried derivatives.

CONCLUSION

Study of the molecular characteristics of a known major allergen allows the identification of technological processes that may be capable of improving the tolerance of allergic subjects to a specific food. Even though any hoped for reduced allergenicity must be verified under medical supervision, the use of new products could obviate the need to avoid important foods such as meat in childhood.

Effect of ingestion of cow's milk hydrolysed formulas on whey protein-specific Th2 immune responses in naive and sensitized mice

BACKGROUND

For genetically predisposed atopic infants, cow's milk protein hydrolysed formulas have been widely used.

OBJECTIVE

Whether hydrolysed formulas can induce oral tolerance to whey proteins will be extensively studied in naïve and sensitized mice.

METHODS

Antigenicity of hydrolysed formulas was first studied using immunoblotting. Naïve mice fed hydrolysed formulas for 1-4 weeks were sensitized with whey allergens. In contrast, mice sensitized with whey allergens were fed hydrolysed formulas continually for 12 weeks.

RESULTS

Whey allergens were found in Nan and Neoangelac FL. Large whey peptides with antigenicity were found in Nan-HA. Profound suppression of IgE, IgG1 and IgG responses to whey allergens were induced in those fed Nan for 1 week, or Nan-HA for 4 weeks. IgE responses to whey allergens were suppressed in those fed Neoangelac FL for 4 weeks, or Nan-HA for 1-2 weeks. In contrast, those fed extensively hydrolysed formulas for 1-4 weeks failed to show decreased responses. On the other hand, IgE responses to beta-lactoglobulin, but not to bovine serum albumin or alpha-lactalbumin, were decreased in sensitized mice fed Nan for 12 weeks. There was no suppression in sensitized mice fed hydrolysed formulas.

CONCLUSION

Suppression of IgE responses to whey proteins was readily induced in naïve mice fed Nan or Nan-HA for 1 week. In contrast, it was hardly induced in sensitized mice even after prolonged feeding of Nan for 12 weeks, let alone hydrolysed formulas.

Clinical tolerance to lactose in children with cow's milk allergy

OBJECTIVE

Adverse reactions following the ingestion of lactose have been reported in children with cow's milk (CM) allergy. Whether this is attributable to the contamination of lactose with CM proteins is unknown. In this paper, we assessed clinical tolerance of lactose derived from CM whey in children hypersensitive to CM from 2 university hospital pediatric departments.

DESIGN

Twenty-four children (5 girls and 19 boys, median 25 months old; range: 2-107 months) with immediate CM allergy confirmed at history or during double-blind, placebo-controlled food challenge (DBPCFC) were enrolled. DBPCFC with CM could be conducted in 11 of 24 patients. Children with a history of immediate/delayed reactions to soy formula (SF) were excluded. Clinical tolerance to CM, SF, and SF + lactose was assessed by: 1) skin prick test with casein, lactalbumin, soy commercial allergen preparations, fresh CM, SF, SF and lactose, lactose (Official Pharmacopoeia) in 4 concentrations (0.01%, 0.1%, 1%, 10%); 2) specific serum immunoglobulin E determination by CAP system technology; 3) DBPCFC in 8 incremental doses of SF + lactose and using SF as a placebo to make up a total of 240 mL of reconstituted formula.

RESULTS

With a positive cutoff point of > or = 3 mm wheal diameter at SPT, all patients were sensitized to fresh CM, lactalbumin, and/or casein. Twenty-three of 24 patients (95.8%) were SPT-positive to CM formula, 16 of 24 to lactalbumin (66.6%), 14 of 24 to casein (58.3%), and none to SF, SF + lactose, or lactose alone at all dilutions. Complexed immunoglobulin E determinations were positive for CM in 23 of 24 cases and negative in all cases for soy. Challenge with SF + lactose was negative in all cases.

CONCLUSIONS

Even children hypersensitive to CM are clinically tolerant to lactose and can safely consume foods and drugs with lactose from bovine sources as an ingredient. Lactose exclusion is unwarranted from soy preparations on grounds of potential allergic reactions to CM protein residue.

Allergenicity of a hydrolyzed rice infant formula in a guinea pig model

BACKGROUND

Because sensitization to cow's milk is a common finding in children, the identification of safe alternative protein sources is important in the management of childhood allergy.

OBJECTIVE

To evaluate, in an animal model, the allergenicity of a novel formula based on hydrolyzed rice proteins.

METHODS

We conducted an experiment involving 130 guinea pigs, from 7 to 12 days old at the onset of the study. The animals were divided into 13 groups and were given, ad libitum, one of the following liquids to drink: (1) rice hydrolysate formula (RF), (2) a conventional cow's milk formula (CMF), or (3) water. After a 37-day sensitization period, a challenge was given, consisting of an intravenous injection of either isolated proteins or ultracentrifuged formulas (uCMF and uRF). Specific IgG antibodies to beta-lactoglobulin, casein, and whole rice protein were measured by enzyme-linked immunosorbent assay.

RESULTS

When animals fed CMF were challenged with beta-lactoglobulin, casein, or whole uCMF, they showed significantly more reactions than did those fed RF when challenged with the same proteins (P < 0.001). In the groups fed RF, no reaction was observed after challenge with uRF, and only 2 mild reactions occurred after challenge with rice protein. Very low levels of specific IgG antibodies to rice protein were noted in all the groups, including the RF-fed animals, and no significant differences were evident between groups.

CONCLUSIONS

The findings suggest that this new formula based on hydrolyzed rice proteins has a very low sensitizing capability.

Use of hydrolysates in the treatment of cow's milk allergy

BACKGROUND

Hydrolyzed formulas (HFs) are in general well tolerated by children with cow's milk allergy (CMA), although cases of allergic reactions have been reported and residual allergenicity of HF has been demonstrated

OBJECTIVE

To review the most relevant studies of the HFs for residual allergenicity, tolerance, and safety in the past 20 years.

DATA SOURCES AND METHODS

MEDLINE searches for the years 1970 to 2001 using the following algorithm (hydrolysate and allergy; food intolerance/allergy; protein hydrolysate).

RESULTS

The literature confirmed that although some antigenicity remains, HFs are well tolerated by children with CMA. Rice HF has proven safe when tested by double-blind, placebo-controlled food challenge in a study population of 18 children allergic both to cow's milk (CM) and soy protein.

CONCLUSIONS

Absolute avoidance of CM proteins means substitution by soy-, rice-, or amino acid-based formulas. As 8 to 14% of infants allergic to CM react to soy and amino acid-based formulas are expensive, scientific societies recommend the use of formulas based on extensively hydrolyzed CM proteins as first alternatives in children with CMA. Although both soy- and rice-based HFs have now been shown to be safe for these children, further nutritional and clinical studies are needed.

Cross-reactivity between mammalian proteins

BACKGROUND

Cross-reactivity between food allergens occurs when they share part of their amino acid sequence, or when their three-dimensional molecular structure causes them to have a similar capacity to bind specific antibodies.

OBJECTIVES

To review data from our laboratory on cross-reactivity between mammalian proteins (milk and meat allergens).

METHODS

Studies used immunoelectrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis/polyacrylamide gel electrophoresis and immunoblotting), and animal monoclonal antibodies.

RESULTS

The findings suggest that animal monoclonal antibodies specific for cow's milk proteins are able to recognize the major part of milk proteins from mammals bred in Mediterranean countries (sheep, goat, and buffalo); weak cross-reactivity was observed with milk proteins from mares and donkeys. None of the antibodies used in our studies reacted with proteins from an exotic mammalian species: the camel. Similar cross-reactions were found with human circulating immunoglobulin E from children allergic to milk. With regard to beef allergy, monoclonal antibodies specific for bovine serum albumin cross-reacted only with ovine serum albumin, whereas the number of sera from allergic children able to recognize other mammalian serum albumins depended directly on the closeness of phylogenetic relationship between animal species and inversely on the percent identity with human serum albumin in the main epitopic sequence.

CONCLUSION

An area of heterogeneity between animal and human species in a critical amino acid sequence (epitope) of an allergen can determine the degree of immunogenic activity.

Proteolysis of bovine beta-lactoglobulin during thermal treatment in subdenaturing conditions highlights some structural features of the temperature-modified protein and yields fragments with low immunoreactivity

Bovine beta-lactoglobulin was hydrolyzed with trypsin or chymotrypsin in the course of heat treatment at 55, 60 and 65 degrees C at neutral pH. At these temperatures beta-lactoglobulin undergoes significant but reversible structural changes. In the conditions used in the present study, beta-lactoglobulin was virtually insensitive to proteolysis by either enzyme at room temperature, but underwent extensive proteolysis when either protease was present during the heat treatment. High-temperature proteolysis occurs in a progressive manner. Mass spectrometry analysis of some large-sized breakdown intermediates formed in the early steps of hydrolysis indicated that both enzymes effectively hydrolyzed some regions of beta-lactoglobulin that were transiently exposed during the physical treatments and that were not accessible in the native protein. The immunochemical properties of the products of beta-lactoglobulin hydrolysis were assessed by using various beta-lactoglobulin-specific antibodies, and most epitopic sites were no longer present after attack of the partially unfolded protein by the two proteases.

Evaluation of the residual antigenicity and allergenicity of cow's milk substitutes by in vitro tests

BACKGROUND

This study aimed the to investigate presence of residual allergenic cow's milk proteins (CMP) in some milk substitutes employed in the treatment of cow's milk allergy (CMA). These allergens may interfere with the treatment, and elicit allergic reactions in sensitized individuals.

METHODS

The protein composition of the different extracts was evaluated by Lowry's method and tricine SDS-PAGE. Different immunoenzymatic methods were used (ELISA, EAST and immunoblotting) to quantify total serum IgE and specific serum IgE, as well as to detect the presence of antigenic and allergenic components.

RESULTS

The results showed a higher protein content in mammalian milks (cow, sheep, mare, goat, and human) than in hydrolyzed substitutes (partially or extensively hydrolyzed casein or whey proteins). Residual native, processed, or contaminant polypeptides have been identified in the moderate hydrolysates, whereas extensive hydrolysates did not show the presence of residual components by immunoblotting. However, specific antibodies with capacity to bind to peptides have been detected by EAST and ELISA, suggesting that extensive hydrolysates contain residual peptides that preserve immunoreactive epitopes. We were unable to demonstrate either residual antigenicity or allergenicity in an amino-acid-based formula.

CONCLUSIONS

Immunoenzymatic methods were used to detect the presence of cross-reactive components in mammalian milks. Residual allergenic components from cow's milk could be identified in both the moderate and extensive hydrolysates analyzed. This information may be relevant to the treatment of CMA.

Cow's milk-specific cellular and humoral immune responses and atopy skin symptoms in infants from atopic families fed a partially (pHF) or extensively (eHF) hydrolyzed infant formula

BACKGROUND

Hydrolyzed milk formulas are recommended to feed infants at high risk of atopy if breast-feeding is not possible. We studied the specific cellular and humoral immune response to cow's milk proteins and occurrence of atopic dermatitis under different feeding regimens: two hydrolyzed infant milk formulas (partially [pHF] and extensively hydrolyzed [eHF]) and under exclusive breast-feeding (BF).

METHODS

Seventy-two infants from families with atopic symptoms were randomized in the pHF and eHF groups, respectively. At 6 and 12 months of age, peripheral blood mononuclear cell proliferation along with specific IgG and IgE to cow's milk proteins was determined in infants fed pHF or eHF, respectively, and those who had not yet received any formula at 6 months of age (BF). Cases of atopic dermatitis were recorded throughout the first 12 months of life, and their severity was evaluated with SCORAD points.

RESULTS

A significantly decreased proliferation to cow's milk caseins was found in the pHF group compared to the exclusively breast-fed group. Medians of stimulation indexes for CAS at 6 months were as follows: pHF 1.18; n=24; BF 1.70; n=24 (P=0.033, Mann-Whitney U-test). Higher levels of plasma IgG antibodies to BCAS were found in infants fed pHF than in those fed eHF at 12 months. Optical density (OD): (25th percentile; median; 75th percentile): pHF: 0.00; 0.14; 0.38; n=30; eHF: 0.00; 0.03; 0.14; n=28; P=0,089, Mann-Whitney U-test. Cow's milk-specific IgE was detected at 6 months as follows: BF: 3 of 24; eHF: 2 of 21; pHF: 0 of 23. The number of cases of atopic dermatitis and their severity did not differ among the groups during the first 12 months.

CONCLUSIONS

Feeding pHF appears to suppress cow's milk-specific cellular responses and stimulate specific IgG production. Specific IgE sensitization can occur also with breast-feeding.

Severe anaphylaxis induced by latex as a contaminant of plastic balls in play pits

BACKGROUND

Latex causes anaphylaxis in specific contexts among children. We present 2 cases that show that severe reactions may occur in everyday circumstances with latex as a contaminant.

OBJECTIVE

Because 2 cases of severe reactions to latex suggested similar circumstances of exposure, we investigated the immediate environment in which episodes occurred.

METHODS

A 5-year-old girl presented to our casualty department with anaphylaxis after playing in a ball pit filled with approximately 10-cm diameter plastic balls in an American-style fast-food outlet. Two months later, a 9-year-old boy had severe anaphylaxis followed by an asthma attack with loss of consciousness while playing in the playpen of a different outlet belonging to the same company. Latex sensitization was confirmed in both cases by means of skin prick testing, latex glove skin prick testing, and 1-glove finger testing. Immunoblotting of elutions from a ball, the natural rubber latex foam pit lining, and its polyvinyl chloride sheet were performed.

RESULTS

In the girl's immunoblot high levels of IgE specific to Hev b 4, Hev b 7, and Hev b 2 were found. The boy's immunoblot showed positivity to Hev b 7. The polyvinyl chloride ball sample showed a high concentration of specific Hevea species allergen similar to that of the foam layer sample.

CONCLUSION

Severe anaphylaxis can result from contact with latex proteins as a contaminant, rather than as a component, of play area ball pits and therefore outside the reported settings. Emergency health care workers should be aware of this kind of risk. A latex-reduced environment might prevent potentially severe reactions in young customers of fast-food outlets.

Detection of potentially allergenic material in 12 hydrolyzed milk formulas

Hypoallergenic milk formulas are used as an alternative diet for infants who have allergies to cow's milk when breast-feeding is not possible. These products are based on proteins, which have been heat-treated and hydrolyzed to a different degree in order to cleave antibody-binding structures. Even extensively hydrolyzed products have occasionally been observed to elicit allergic reactions in sensitized infants, however. Therefore, the parameters of relevance to allergenic potential require more investigation. The objective of the present study was to investigate 12 different hydrolyzed milk formulas for their contents of potentially allergenic protein material, i.e. material that may induce allergenicity or elicit allergic responses in already sensitized individuals. Analytical methods applied were gel filtration, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), native PAGE, immunoblotting, dot-immunobinding, and ELISA. Care was taken to assure that all protein fractions were investigated, including supernatants and precipitates following centrifugation of the milk formulas. By gel filtration, protein material with apparent molecular masses of 7 to >30 kDa was detected. Analysis by SDS-PAGE of formula precipitates showed that proteins with a molecular mass above 20 kDa were present even in some of the extensively hydrolyzed formulas. Residual antigenic beta-lactoglobulin was found by ELISA in all products. By immunoblotting and dot-immunobinding with antibodies against total whey, caseins, or Kunitz soybean trypsin inhibitor, we observed antigenic material mainly in partially hydrolyzed products. We concluded that SDS-PAGE of formula supernatants and precipitates gave the most differentiated profile of hydrolyzed formulas and that this method is well suited for screening potential allergenicity.

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.

Cross-reactivity between milk proteins from different animal species

BACKGROUND

Cow's milk allergy is quite frequent in the first years of human life. When breast-feeding is not possible, a cow's milk substitute must be provided for allergic subjects. Different alternatives to cow's milk have been suggested as protein sources (soy, hydrolysed proteins, goat's milk, etc.), but all these dietetic solutions are not without risks for polyallergic or more sensitive subjects.

OBJECTIVE

To obtain new information on the suitability of other mammalian milks for allergic children, we evaluated the cross-reactivity between milk proteins from different animal species.

METHODS

Milk samples were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). To detect antibody-antigen complexes, immunoblotting was performed by using sera from children allergic to cow's and ewe's milk (RAST class >/= 4) and monoclonal antibodies (MoAb) specific for bovine proteins (caseins and beta-lactoglobulin).

RESULTS

IgEs from children allergic to cow's milk are capable of recognizing most part of milk proteins from mammals bred in European countries (ewe, goat, buffalo), while no serum used in this study contains IgEs reacting with camel's milk proteins. Camel's milk was also not recognized from circulating IgEs from a child specifically allergic to ewe's milk. Specific antibovine monoclonal antibodies cross-reacted with proteins from other mammalian species, apart from those of camel.

CONCLUSIONS

Homologies in amino acidic composition could justify the cross-reactivity observed between proteins from different animal species. On the other hand, the phylogenetic difference could be responsible for the failed recognition of camel's proteins by circulating IgEs and monoclonal antibodies.