Dietary bovine beta-lactoglobulin is transferred to human milk

Nutritional Management of Children with Food Allergies

Purpose of the Review

The purpose of the review is to review the evidence for the nutritional management of paediatric food allergy and provide a practical approach for healthcare professionals working in this area.

Recent Findings

Dietary elimination remains the mainstay for management of food allergies in children. However, the elimination of food allergens increases the risk for growth faltering, micronutrient deficiencies and feeding difficulties. Breastmilk remains the ideal source of nutrition for infants, but when not available, the vast majority will tolerate an extensively hydrolysed formula, and rice hydrolysate has also been suggested as a suitable alternative. Only in severe cases, including anaphylaxis, eosinophilic oesophagitis and growth faltering, is an amino acid formula indicated. The early introduction of peanut and egg and avoiding the delay in the introduction of other allergens, when not already allergic, has been highlighted by recent studies.

Summary

Whilst the elimination of allergens increases the risk of developing poor growth, micronutrient deficiencies and feeding difficulties, optimal, early dietary input, including advice on active introduction of allergens and alternative feeds, ideally from a registered dietitian/nutritionist, may be prevent and improve outcomes.

Cow's Milk Antigens Content in Human Milk: A Scoping Review

The functionality of breast milk in terms of immunity is well-known. Despite this, a significant proportion of breastfed infants exhibit sensitization to different potentially allergenic proteins and clinical reactivity (including anaphylaxis) early in life and before the introduction of complementary feeding for the first time. The potential induction of early oral tolerance to overcome early allergic sensitization through exposure to allergens in breast milk also remains controversial and not yet well-established. The objective of this scoping review is to provide a critical appraisal of knowledge about the content of cow’s milk antigens in human milk. The amount of dietary derived milk antigens found in human milk and the analytical methodologies used to detect and quantify these antigens, the allergic status of the mother, the stage of lactation, the time of sampling (before or after ingestion of food), and the impact of human milk allergen on the infant were the outcomes that were assessed. Allergy risk was explored in all reviewed studies and could help to better elucidate its role in the context of allergic disease development. According to the included literature, we can conclude that there are mainly fragments derived from bovine proteins in human milk, and the presence of potentially allergenic molecules is greater in the milk of mothers with an allergic tendency. A clear relationship between maternal diet and allergen content in breast milk could not be firmly concluded though. Also, infants receiving milk from human milk banks, where donor milk is pasteurized for preservation, may be subject to greater risk of allergy development, especially for β-lactoglobulin.

Breastfeeding: Maternally Transferred Allergens in Breast Milk: Protective or Sensitizing?

According to a thorough literature search, the following allergen sources have been associated with allergy symptoms in the exclusively breastfed child: hen's egg, cow's milk, peanut, trout. Subsequently, several studies use the advantage of molecular allergology and investigate the potential transfer of single allergens into breastmilk. This is shown for caseins, whey proteins, gliadin, ovalbumin, ovomucoid, the peanut allergens Ara h 2 and Ara h 6, as well as the inhalant allergens Der p 1 and Blo t 5. It is still a matter of debate whether or not food allergens transferred via breastfeeding to the baby promote allergic sensitization or induce tolerance and via which mechanisms they may shift the immune response to the one or other side. Noteworthy, some breastfed children are described to be sensitized to foods before being exposed to solid foods, and this exposure may have occurred through breastmilk. In the light of these findings the investigation of food allergens transferred from the mother's diet into breastmilk and their impact on sensitization or allergy prevention remains a current topic in research. This review describes breastmilk in its composition and provides data on the identification of food allergens therein including human and mouse studies.

Food Proteins in Human Breast Milk and Probability of IgE-Mediated Allergic Reaction in Children During Breastfeeding: A Systematic Review

BACKGROUND

Previous reports suggested that food proteins present in human milk (HM) may trigger symptoms in allergic children during breastfeeding, but existing evidence has never been reviewed systematically.

OBJECTIVE

To assess the probability of food proteins in HM to trigger allergic reactions in infants with IgE-mediated food allergy.

METHODS

Electronic bibliographic databases (MEDLINE, EMBASE) were systematically searched from inception to November 3, 2021. The data regarding the levels of food proteins detected in HM were extracted and compared with data from the Voluntary Incidental Trace Allergen Labelling (VITAL 3.0) guide to assess the probability of food-allergic individuals to experience immediate type allergic reactions on ingesting HM.

RESULTS

A total of 32 studies were identified. Fourteen studies assessed excretion of cow's milk proteins into HM, 9 egg, 4 peanut, and 2 wheat; 3 measured levels of cow's milk and egg proteins simultaneously. We found that levels of all food proteins across the studies were much lower than the eliciting dose for 1% of allergic individuals (ED01) in most of the samples. The probability of an IgE-mediated allergic reaction in a food-allergic infant breastfed by a woman consuming the relevant food can be estimated as ≤1:1000 for cow's milk, egg, peanut, and wheat.

CONCLUSIONS

To our knowledge, this is the first systematic review that assesses and summarizes evidence on food proteins in HM and potential for IgE-mediated allergic reactions. Our data suggest that the probability of IgE-mediated allergic reactions to food proteins in HM is low.

Cow's Milk Protein Allergy in Term and Preterm Infants: Clinical Manifestations, Immunologic Pathophysiology, and Management Strategies

Cow's milk allergy is a common food allergy among infants. Symptoms of cow's milk allergy are wide-ranging and depend on the mechanism involved. There are immunoglobulin E (IgE)-mediated, non-IgE-mediated, and mixed mechanisms of food allergy. Symptoms of IgE-mediated cow's milk allergy may be mild or may progress to anaphylaxis, which can be life-threatening. Non-IgE-mediated allergy includes food protein-induced allergic proctocolitis (FPIAP), food protein-induced enterocolitis syndrome, food protein-induced enteropathy, and Heiner syndrome (pulmonary hemosiderosis). These diagnoses comprise about half of all cow's milk allergies. The most common manifestation of cow's milk allergy in infants is FPIAP. FPIAP is commonly seen in healthy, full-term infants who present with rectal bleeding and are otherwise well-appearing. This can occur in both formula-fed and exclusively breastfed infants. Food proteins secreted in maternal breast milk can contribute to the development of these symptoms. Maternal cow's milk elimination diet is often successful in helping resolve symptoms. A period of reintroduction of cow's milk resulting in re-emergence of symptoms in stable asymptomatic infants is an excellent diagnostic tool to confirm a cow's milk allergy. Preterm infants are susceptible to food allergy, as demonstrated from several case reports of necrotizing enterocolitis-like illnesses that responded clinically to cow's milk elimination. Further study is needed about food allergy in the preterm infant population.

Discovery and Quantification of Nonhuman Proteins in Human Milk

The question whether and which nonhuman peptides or proteins are present in human milk was raised many decades ago. However, due to cross-reactivity or nonspecific antibody recognition, the accuracy of detection by immunochemical methods has been a concern. Additionally, the relative low-abundance of nonhuman peptides/proteins in the complex milk sample makes them a challenging target to detect. Here, by deep proteome profiling, we detected several nonhuman peptides, which could be grouped as nonhuman proteins. We next estimated their concentration in human milk by combining data-dependent shotgun proteomics and parallel reaction monitoring. First, we fractionated human milk at the protein level and were able to detect 1577 human proteins. Additionally, we identified 109 nonhuman peptides, of which 71 were grouped into 36 nonhuman proteins. In the next step, we targeted 37 nonhuman peptides and nine of them could be repeatedly quantified in human milk samples. Peptides/proteins originating from bovine milk products were the dominant nonhuman proteins observed, notably bovine caseins (α-S1-, α-S2-, β-, κ-caseins) and β-lactoglobulin. The method we present here can be expanded to investigate more about nonhuman peptides and proteins in human milk and give a better understanding of how human milk plays a role in allergy prevention.

Infant Colic-What works: A Systematic Review of Interventions for Breast-fed Infants

OBJECTIVES

To determine the strength of evidence for commonly used interventions for colic in breast-fed and mixed-fed infants younger than 6 months.

METHODS

Searches of PubMed, CINAHL, Embase, AMED, and Web of Science databases were conducted from July 2014 to July 2015. Included studies were randomised controlled trials involving mothers and their colicky infants younger than 6 months; assessed colic against the Wessel or modified Wessel criteria; and included phytotherapies, prescription medicines, and maternal dietary interventions. Studies with <16 participants were excluded. Meta-analyses were conducted where data were sufficient to enable pooling. Quality was assessed against the Cochrane Risk Bias Assessment Tool.

RESULTS

A total of 17 articles met the inclusion criteria for this review. The 6 studies included for subgroup meta-analysis on probiotic treatment, notably Lactobacillus reuteri, demonstrated that probiotics appear an effective treatment, with an overall mean difference in crying time at day 21 of -55.8 min/day (95% CI -64.4 to -47.3, P = 0.001). The 3 studies included for subgroup meta-analysis on preparations containing fennel suggest it to be effective, with an overall mean difference of -72.1 min/day (95% CI -126.4 to -17.7, P < 0.001).

CONCLUSIONS

Probiotics, in particular L reuteri, and preparations containing fennel oil appear effective for reducing colic, although there are limitations to these findings. The evidence for maternal dietary manipulation, lactase, sucrose, glucose, and simethicone is weak. Further well-designed clinical trials are required to strengthen the evidence for all of these interventions.

Maternal dietary antigen avoidance during pregnancy or lactation, or both, for preventing or treating atopic disease in the child

BACKGROUND

Some breastfed infants with atopic eczema benefit from elimination of cow milk, egg, or other antigens from their mother's diet. Maternal dietary antigens are also known to cross the placenta.

OBJECTIVES

To assess the effects of prescribing an antigen avoidance diet during pregnancy or lactation, or both, on maternal and infant nutrition and on the prevention or treatment of atopic disease in the child.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 July 2012).

SELECTION CRITERIA

All randomized or quasi-randomized comparisons of maternal dietary antigen avoidance prescribed to pregnant or lactating women. We excluded trials of multimodal interventions that included manipulation of the infant's diet other than breast milk or of non-dietary aspects of the infant's environment.

DATA COLLECTION AND ANALYSIS

We extracted data from published reports, supplemented by additional information received from the trialists we contacted.

MAIN RESULTS

The evidence from five trials, involving 952 participants, does not suggest a protective effect of maternal dietary antigen avoidance during pregnancy on the incidence of atopic eczema during the first 18 months of life. Data on allergic rhinitis or conjunctivitis, or both, and urticaria are limited to a single trial each and are insufficient to draw meaningful inferences. Longer-term atopic outcomes have not been reported. The restricted diet during pregnancy was associated with a slightly but statistically significantly lower mean gestational weight gain, a non-significantly higher risk of preterm birth, and a non-significant reduction in mean birthweight. The evidence from two trials, involving 523 participants, did not observe a significant protective effect of maternal antigen avoidance during lactation on the incidence of atopic eczema during the first 18 months or on positive skin-prick tests to cow milk, egg, or peanut antigen at one, two, or seven years. One crossover trial involving 17 lactating mothers of infants with established atopic eczema found that maternal dietary antigen avoidance was associated with a non-significant reduction in eczema severity.

AUTHORS' CONCLUSIONS

Prescription of an antigen avoidance diet to a high-risk woman during pregnancy is unlikely to reduce substantially her child's risk of atopic diseases, and such a diet may adversely affect maternal or fetal nutrition, or both. Prescription of an antigen avoidance diet to a high-risk woman during lactation may reduce her child's risk of developing atopic eczema, but better trials are needed. Dietary antigen avoidance by lactating mothers of infants with atopic eczema may reduce the severity of the eczema, but larger trials are needed.

Peanut allergens are rapidly transferred in human breast milk and can prevent sensitization in mice

BACKGROUND

Food allergens have been evidenced in breast milk under physiological conditions, but the kinetic and the role of this passage in food allergies are still unclear. We then aimed to analyze the passage of peanut allergens in human breast milk and their allergenicity/immunomodulatory properties.

METHODS

Human breast milk was collected from two non-atopic peanut-tolerant mothers before and at different time points after ingestion of 30 g of commercial roasted peanut. Ara h 6, Ara h 6 immune complexes, and the IgE binding capacity of breast milk samples were measured using specific immunoassays. Their allergenic functionality was then assessed using cell-based assay. Finally, human breast milk obtained before or after peanut ingestion was administered intragastrically to BALB/c mice at different ages, and mice were further experimentally sensitized to peanut using cholera toxin.

RESULTS

Ara h 6 is detected as soon as 10 min after peanut ingestion, with peak values observed within the first hour after ingestion. The transfer is long-lasting, small quantities of peanut allergens being detected over a 24-h period. IgG-Ara h 6 and IgA-Ara h 6 immune complexes are evidenced, following a different kinetic of excretion than free allergens. Peanut allergens transferred in milk are IgE reactive and can induce an allergic reaction in vitro. However, administration of human breast milk to young mice, notably before weaning, does not lead to sensitization, but instead to partial oral tolerance.

CONCLUSION

The low quantities of immunologically active allergens transferred through breast milk may prevent instead of priming allergic sensitization to peanut.

Whole cow's milk in infancy

Early introduction of whole cow's milk may lead to iron deficiency anemia. From a nutritional point of view, it is best to delay the introduction of whole cow's milk until the infant is one year old. While there is no evidence to suggest adverse clinical sequelae associated with the increased renal solute load in healthy infants, feeding with whole cow's milk would narrow the margin of safety in situations that may lead to dehydration. Early exposure to cow's milk proteins increases the risk of developing allergy to milk proteins. Because of the possible association between early exposure to cow's milk proteins and risk for type 1 diabetes mellitus, breast-feeding and avoidance of commercially available cow's milk and products containing intact cow's milk protein during the first year of life are strongly encouraged in families with a strong history of insulin dependent diabetes mellitus. The authors suggest that the optimal food in infancy is human breast milk. If human milk is not available, it is preferred that iron-fortified formulas rather than whole cow's milk be used during the first year of life.

Maternal dietary antigen avoidance during pregnancy or lactation, or both, for preventing or treating atopic disease in the child

BACKGROUND

Some breastfed infants with atopic eczema benefit from elimination of cow milk, egg, or other antigens from their mother's diet. Maternal dietary antigens are also known to cross the placenta.

OBJECTIVES

To assess the effects of prescribing an antigen avoidance diet during pregnancy or lactation, or both, on maternal and infant nutrition and on the prevention or treatment of atopic disease in the child.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 July 2012).

SELECTION CRITERIA

All randomized or quasi-randomized comparisons of maternal dietary antigen avoidance prescribed to pregnant or lactating women. We excluded trials of multimodal interventions that included manipulation of the infant's diet other than breast milk or of non-dietary aspects of the infant's environment.

DATA COLLECTION AND ANALYSIS

We extracted data from published reports, supplemented by additional information received from the trialists we contacted.

MAIN RESULTS

The evidence from five trials, involving 952 participants, does not suggest a protective effect of maternal dietary antigen avoidance during pregnancy on the incidence of atopic eczema during the first 18 months of life. Data on allergic rhinitis or conjunctivitis, or both, and urticaria are limited to a single trial each and are insufficient to draw meaningful inferences. Longer-term atopic outcomes have not been reported. The restricted diet during pregnancy was associated with a slightly but statistically significantly lower mean gestational weight gain, a non-significantly higher risk of preterm birth, and a non-significant reduction in mean birthweight.The evidence from two trials, involving 523 participants, did not observe a significant protective effect of maternal antigen avoidance during lactation on the incidence of atopic eczema during the first 18 months or on positive skin-prick tests to cow milk, egg, or peanut antigen at one, two, or seven years.One crossover trial involving 17 lactating mothers of infants with established atopic eczema found that maternal dietary antigen avoidance was associated with a non-significant reduction in eczema severity.

AUTHORS' CONCLUSIONS

Prescription of an antigen avoidance diet to a high-risk woman during pregnancy is unlikely to reduce substantially her child's risk of atopic diseases, and such a diet may adversely affect maternal or fetal nutrition, or both. Prescription of an antigen avoidance diet to a high-risk woman during lactation may reduce her child's risk of developing atopic eczema, but better trials are needed.Dietary antigen avoidance by lactating mothers of infants with atopic eczema may reduce the severity of the eczema, but larger trials are needed.

Surface Plasmon Resonance imaging-based sensing for anti-bovine immunoglobulins detection in human milk and serum

Only few papers deal with Surface Plasmon Resonance imaging (SPRi) direct detection on complex matrices, limiting the biosensor application to real analytical problems. In this work a SPRi biosensor for anti-bovine IgG detection in untreated human bodily fluids, i.e. diluted human serum and milk, was developed. Enhanced levels of cow's milk antibodies in children's serum are suspected for their possible correlation with Type 1 diabetes during childhood and their detection in real samples was up to now performed by classical immunoassays based on indirect detection. The biosensor was optimised in standard samples and then in untreated human milk for anti-bovine IgG direct detection. The key novelty of the work is the evaluation of matrix effect by applying to real samples an experimental and ex ante method previously developed for SPRi signal sampling in standard solutions, called "Data Analyzer"; it punctually visualises and analyses the behaviour of receptor spots of the array, to select only spot areas with the best specific vs. unspecific signal values. In this way, benefits provide by SPRi image analysis are exploited here to quantify and minimise drawbacks due to the matrix effect, allowing to by-pass every matrix pre-treatment except dilution.

Update on optimized purification and characterization of natural milk allergens

Highly purified allergens namely cow's milk alpha-lactalbumin (ALA). (Bos d 4), beta-lactoglobulin (BLG) (Bos d 5) and casein (Bos d 8) and goat's milk casein were prepared from the raw milk from a single animal with a known genetic background. Consequently the natural isoforms are limited, constant and characterized. Purification included selective precipitations and chromatographical steps. Characterization of structure and allergenic activity assessment of milk allergens were carried out using physicochemical and immunochemical methods. Taken together data demonstrated the absence of impurities and of contamination by other milk allergens in each preparation. NMR and circular dichroism analyses confirmed the native conformation and proper folding of ALA and BLG and the expected absence of folding of bovine and caprine casein. Enzyme immuno assays confirmed the native conformation of BLG and the purity and immunoreactivity of all the proteins. The allergenic activity, e. g. the IgE binding capacity, of purified proteins was identical as that of those proteins when present in milk. The purified proteins also demonstrated the ability to provoke the degranulation of humanized rat basophilic leukaemia cells. All the data thus confirm the purity, identity, structural conformation and functionality of the prepared milk allergens.

Maternal dietary antigen avoidance during pregnancy or lactation, or both, for preventing or treating atopic disease in the child

BACKGROUND

Some breastfed infants with atopic eczema benefit from elimination of cow milk, egg, or other antigens from their mother's diet. Maternal dietary antigens are also known to cross the placenta.

OBJECTIVES

To assess the effects of prescribing an antigen avoidance diet during pregnancy or lactation, or both, on maternal and infant nutrition and on the prevention or treatment of atopic disease in the child.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (March 2006) and contacted researchers in the field.

SELECTION CRITERIA

All randomized or quasi-randomized comparisons of maternal dietary antigen avoidance prescribed to pregnant or lactating women. We excluded trials of multimodal interventions that included manipulation of the infant's diet other than breast milk or of nondietary aspects of the infant's environment.

DATA COLLECTION AND ANALYSIS

We extracted data from published reports, supplemented by additional information received from the trialists we contacted.

MAIN RESULTS

The evidence from four trials, involving 334 participants, does not suggest a protective effect of maternal dietary antigen avoidance during pregnancy on the incidence of atopic eczema during the first 18 months of life. Data on allergic rhinitis or conjunctivitis, or both, and urticaria are limited to a single trial each and are insufficient to draw meaningful inferences. Longer-term atopic outcomes have not been reported. The restricted diet during pregnancy was associated with a slightly but statistically significantly lower mean gestational weight gain, a nonsignificantly higher risk of preterm birth, and a nonsignificant reduction in mean birthweight.The evidence from one trial, involving 26 participants, did not observe a significant protective effect of maternal antigen avoidance during lactation on the incidence of atopic eczema during the first 18 months.One crossover trial involving 17 lactating mothers of infants with established atopic eczema found that maternal dietary antigen avoidance was associated with a nonsignificant reduction in eczema severity.

AUTHORS' CONCLUSIONS

Prescription of an antigen avoidance diet to a high-risk woman during pregnancy is unlikely to reduce substantially her child's risk of atopic diseases, and such a diet may adversely affect maternal or fetal nutrition, or both. Prescription of an antigen avoidance diet to a high-risk woman during lactation may reduce her child's risk of developing atopic eczema, but better trials are needed. Dietary antigen avoidance by lactating mothers of infants with atopic eczema may reduce the severity of the eczema, but larger trials are needed.

Diet of lactating women and allergic reactions in their infants

PURPOSE OF REVIEW

To evaluate whether the diet of lactating women modulates the development of allergic disease in their children.

RECENT FINDINGS

Although maternal avoidance of common food protein allergens was previously recommended for lactating women with infants predisposed to allergic disease, recent expert reviews have concluded that there is no strong evidence to support this position. A recent well-controlled study, using egg as an allergen, confirmed that the appearance of food proteins in human milk is common, but this can be highly variable between women even after consuming the same challenge (dose) food. On the other hand, preliminary data suggest that increasing dietary n-3 fatty acids may offer protection from the development of some childhood allergies. A recent animal study offers mechanistic support, indicating that perinatal diets high in n-3 fatty acids can induce oral neonatal tolerance more effectively compared with diets predominating in n-6 fatty acids.

SUMMARY

Current data do not support the use of maternal antigen-avoidance diets during lactation as a strategy to prevent childhood allergies. Controlled trials are required to evaluate the efficacy of maternal dietary n-3 fatty acid interventions in preventing allergic disease in at-risk infants.

Effect of a low-allergen maternal diet on colic among breastfed infants: a randomized, controlled trial

BACKGROUND

There is controversy regarding whether hypersensitivity to food proteins contributes to colic among breastfed infants.

METHODS

A randomized, controlled trial of a low-allergen maternal diet was conducted among exclusively breastfed infants presenting with colic. In the active arm, mothers excluded cow's milk, eggs, peanuts, tree nuts, wheat, soy, and fish from their diet; mothers in the control group continued to consume these foods. Outcomes were assessed after 7 days, as the change in cry/fuss duration over 48 hours, with validated charts. The primary end point was a reduction in cry/fuss duration of > or =25% from baseline. Mothers also assessed the responses to diet with categorical and visual analog scales.

RESULTS

Of 107 infants, 90 completed the trial (mean age: 5.7 weeks; range: 2.9-8.6 weeks; 54 male infants). Infants in both groups presented with significant distress (geometric mean: low-allergen group: 690 minutes per 48 hours; control group: 631 minutes per 48 hours). In follow-up assessments on days 8 and 9, there were significantly more responders in the low-allergen group (74% vs 37%), ie, an absolute risk reduction of 37% (95% confidence interval: 18-56%). Cry/fuss duration per 48 hours was reduced by a substantially greater amount in the low-allergen group; the adjusted geometric mean ratio was 0.79 (95% confidence interval: 0.63-0.97), ie, an average reduction of 21% (95% confidence interval: 3-37%). Mothers' subjective assessments of the responses to diet indicated little difference between the groups.

CONCLUSION

Exclusion of allergenic foods from the maternal diet was associated with a reduction in distressed behavior among breastfed infants with colic presenting in the first 6 weeks of life.

A review of the literature examining the benefits and challenges, incidence and duration, and barriers to breastfeeding in preterm infants

Breastfeeding benefits preterm infants from a nutritional, gastrointestinal, immunological, developmental, and psychological perspective. Despite the benefits, the incidence and duration of breastfeeding preterm infants continues to be less than that of full-term infants. The lower incidence is probably related to breastfeeding challenges that preterm infants and parents face, including establishing and maintaining a milk supply and transitioning from gavage feeding to breastfeeding. In order to increase the incidence and duration of breastfeeding preterm infants, researchers must examine breastfeeding experiences longitudinally. This way, researchers and clinicians can begin to understand the barriers to breastfeeding at various time periods in the breastfeeding experience and begin implementing strategies to remove these barriers.

Risk factors for food allergy

Food allergy is a common problem that often affects young children. Numerous factors affect the development of food allergy both prenatally and postnatally. These factors are genetic and environmental. Although little can be done post-conception to alter a child's genetic risk for developing food allergy, early identification may permit alterations of the environment in which food allergy develops. Environmental factors operate both prenatally and postnatally. By understanding how these factors affect development of food allergy, it may be possible for parents to modulate the development of this difficult problem in their children.

Bovine milk allergenicity

OBJECTIVE

To provide updated data on the characteristics (eg, structure, function, stability) of the main milk proteins identified as allergens and on the characterization of their epitopes.

DATA SOURCES

Basic literature and the most relevant original recent publications on clinical and epidemiologic aspects of milk allergy and the biochemistry and immunochemistry of milk proteins.

STUDY SELECTION

The expert opinion of the author was used to select the relevant data for the review.

RESULTS

Most milk proteins, even proteins present at low concentrations, are potential allergens. Epitopes on milk proteins are both conformational and linear epitopes, widely spread throughout the protein molecules. They may be short fragments, located in hydrophobic parts of the molecule, that comprise highly conserved sequences responsible for IgE cross-reactivity with corresponding milk proteins of other mammals, including humans. Those sequential epitopes have also been proposed as good markers of persistent allergy to milk proteins and may be of particular clinical significance.

CONCLUSIONS

No specific structure or function is associated with allergenicity of milk proteins. Due to the great variability and heterogeneity of the human IgE response, no single allergen or particular structure can account for a major part of milk allergenicity. Furthermore, the available evidence is not sufficient to establish an intake threshold below which allergic reactions are not triggered or to predict reliably the effect of food processing on allergenic potential of milk proteins.

Hypoallergenic formulas--when, to whom and how long: after more than 15 years we know the right indication!

Hypoallergenic formulas are processed by enzymatic hydrolysis of different protein sources such as bovine casein/whey and soy followed by further processing such as heat treatment and/or ultrafiltration, or they are based on amino acid mixtures. The products have been classified according to the degree of protein hydrolysis as 'extensively' or 'partially' hydrolysed protein products. Product properties may be characterized by biochemical techniques, and reduction of allergenicity may be assessed in vitro with various immunological methods, and in vivo with skin prick tests, patch tests and challenge tests. In vitro tests do not predict the allergenic effects in humans, and at present there is no evidence of a specific threshold of immunogenic protein. Only pure amino acid mixtures are considered to be nonallergenic. Other 'hypoallergenic' products contain residual allergenicity. At present, the potential of a product for treatment and prevention of food allergy can only be determined by clinical trials using scientifically appropriate standards. It has been recommended that dietary products for treatment of cow's milk protein allergy in infants should be tolerated by at least 90% (with 95% confidence) of infants with documented cow's milk protein allergy. Some extensively hydrolysed products and amino-acid-based products have met these criteria. Formulas intended for prevention should have a very low, if any, allergenic activity until otherwise proven. So far there are no firm criteria available for the design of hypoallergenic foods for prevention. Newborns included in prevention studies should be from high-risk families; they should be randomized at birth and fed the formula when supplements are needed for at least the first 4-6 months of life. Follow-up should be at least 18 months, and children should be investigated when symptoms appear. Validated clinical criteria, including controlled food challenges, should be used for diagnosis. Infants fed formulas that claim to prevent or delay allergy should have a statistically significant lower prevalence of allergy when compared with infants fed a standard cow's milk formula. Feeding high-risk infants a documented hypoallergenic formula combined with avoidance of solid foods during the first 4-6 months reduces the cumulative incidence of cow's milk protein allergy and atopic dermatitis as compared with a standard cow's-milk-based formula. Partially hydrolysed formulas may have an effect, though it seems to be less than that of extensively hydrolysed formulas at present. Thus, if exclusive breast-feeding for 4-6 months is not possible in high-risk infants, a documented hypoallergenic formula and avoidance of solid foods are recommended for the first 4 months of life.

Maternal dietary antigen avoidance during pregnancy and/or lactation for preventing or treating atopic disease in the child

BACKGROUND

Some breastfed infants with atopic eczema benefit from elimination of cow milk, egg, or other antigens from their mother's diet. Maternal dietary antigens are also known to cross the placenta.

OBJECTIVES

To assess the effects of prescribing an antigen avoidance diet during pregnancy and/or lactation on maternal and infant nutrition and on the prevention or treatment of atopic disease in the child.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (October 2002) and contacted researchers in the field.

SELECTION CRITERIA

All randomized or quasi-randomized comparisons of maternal dietary antigen avoidance prescribed to pregnant or lactating women. We excluded trials of multimodal interventions that included manipulation of the infant's diet other than breast milk or of nondietary aspects of the infant's environment.

DATA COLLECTION AND ANALYSIS

We extracted data from published reports, supplemented by additional information received from the trialists we contacted.

MAIN RESULTS

The evidence from 4 trials involving approximately 451 participants does not suggest a protective effect of maternal dietary antigen avoidance during pregnancy on the incidence of atopic eczema during the first 12 to 18 months of life. Data on allergic rhinitis/conjunctivitis and urticaria are limited to a single trial each and are insufficient to draw meaningful inferences. Longer-term atopic outcomes have not been reported. The restricted diet during pregnancy was associated with a slightly but statistically significantly lower mean gestational weight gain, a nonsignificantly higher risk of preterm birth, and a nonsignificant reduction in mean birthweight.The evidence from 3 trials involving approximately 210 participants suggests a protective effect of maternal antigen avoidance during lactation on the incidence and severity of atopic eczema during the first 12 to 18 months, but methodologic shortcomings argue for caution in interpretation.One crossover trial involving 17 lactating mothers of infants with established atopic eczema found that maternal dietary antigen avoidance was associated with a nonsignificant reduction in eczema severity.

REVIEWER'S CONCLUSIONS

Prescription of an antigen avoidance diet to a high-risk woman during pregnancy is unlikely to reduce substantially her child's risk of atopic diseases, and such a diet may adversely affect maternal and/or fetal nutrition. Prescription of an antigen avoidance diet to a high-risk woman during lactation may reduce her child's risk of developing atopic eczema, but better trials are needed. Dietary antigen avoidance by lactating mothers of infants with atopic eczema may reduce the severity of the eczema, but larger trials are needed.

Cow's milk proteins/allergens

OBJECTIVE

The primary objective of this review is to provide updated data on the structure and function of the main cow's milk proteins (CMPs) identified as allergens and on the characterization of their epitopes.

DATA SOURCES

The review represents a synthesis of basic literature and most relevant original recent publications on both topics of clinical and epidemiologic aspects of milk allergy and of milk protein's bio- and immunochemistry.

STUDY SELECTION

The expert opinion of the author was used to select the relevant data for the review.

RESULTS

Most CMPs are potential allergens, even the proteins present at very low concentration. There are both conformational and linear epitopes, widely spread all along the protein molecules. They may be short fragments, located in hydrophobic parts of the molecule which comprise highly conserved sequences responsible for immunoglobulin E cross-reactivity with corresponding milk proteins of other mammals, including human beings. Those sequential epitopes have also been proposed as good markers of persistent allergy to CMPs.

CONCLUSIONS

No specific structure nor function is associated with allergenicity of CMPs. Variability and heterogeneity of the human immunoglobulin E response preclude anticipating the allergenic potential of any CMP or fragment thereof, as well as justify the need for being careful before using peptides for desensitization or proposing any milk protein hydrolysate in a diet for highly allergenic children.

[Protein hydrolysates: hypoallergenic milks and extensively hydrolyzed formulas. Immuno-allergic basis for their use in prevention and treatment of milk allergy]

Allergy to milk has an estimated incidence of 2.5%. Hypoallergenic milks are partial hydrolysates of proteins with lactose. Extensive hydrolysates of casein are mainly small peptides and do not include lactose in their formula. A primary allergenicity as well as a cross-sensitivity are shown for all partial hydrolysates. Even extensive hydrolysates have a weak potential of cross-allergy. The prevention of cow's milk allergy in infants at peculiar risk, born from atopic parents, is based on breast-feeding and/or partial or extensive hydrolysates. There is no conclusive evidence for the usefulness of eviction of dairy products during pregnancy or during the period of breast-feeding. The treatment needs exclusively extensive casein hydrolysates ensuring a 90% protection with 95% confidence intervals. Predictive prick tests in certain cases may help the choice of another hydrolysate. Severe cases with failure to thrive or multiple food intolerance require an amino-acid based formula (Neocate). A rational diversification of the diet is advised in order to prevent the onset of a multiple food intolerance syndrome which could avert from the recovery of cow milk allergy.

Identification of the human beta-casein C-terminal fragments that specifically bind to purified antibodies to bovine beta-lactoglobulin

The presence of foreign proteins in human milk after the ingestion of bovine dairy products is thought to be one of the possible causes of allergic sensitization in exclusively breast-fed predisposed infants. The immunologic determination of bovine beta-lactoglobulin (LG) concentration in human milk has been reported by several researchers, but the results are conflicting. Moreover, a strong cross-reactivity between antibodies to bovine beta-LG and human milk proteins and peptides was reported, throwing doubt on the reliability of radioimmunoassay and enzyme-linked immunosorbent assay detection and quantification assays for bovine beta-LG in human milk. Thus, the goal of this study was to isolate human milk peptides with a molecular mass >or= 1,000 Da cross-reactive with antibodies to bovine beta-LG in order to identify possible common epitopes between human and bovine milk proteins. The proteins were first isolated by affinity chromatography with purified polyclonal antibodies to bovine beta-LG, followed by gel filtration fast phase liquid chromatography and reverse phase-high performance liquid chromatography purification of the components specifically bound in the affinity separation step. Affinity-bound peptides were identified by determining their amino acid sequence. All the sequenced peptides belonged to the C-terminal part of human beta-casein, which confirms the cross-reactivity of human milk proteins and peptides with antibodies to bovine beta-LG and allows the identification of possible common epitopes between the two proteins. No bovine beta-LG peptides with a molecular mass >or= 1,000 Da were found in our milk samples from healthy mothers on a diet rich in bovine milk and dairy products.

Structure, genomic localization and recombinant expression of the mouse 6-pyruvoyl-tetrahydropterin synthase gene

The 6-pyruvoyl-tetrahydropterin synthase (PTPS) is the second enzyme in the biosynthetic pathway from GTP to tetrahydrobiopterin (BH4). BH4 is an essential cofactor of NO synthases and aromatic amino acid hydroxylases, the latter being responsible for hepatic phenylalanine degradation and monoamine neurotransmitter biosynthesis. BH4 deficiency due to autosomal recessive mutations in the human gene for PTPS leads to a broad range of phenotypes ranging from mild hyperphenylalaninemia to high phenylalanine levels concomitant with neurotransmitter depletion. An animal model to study PTPS deficiency is thus desired to investigate the molecular basis of the disease and its variability. Here, we report on the isolation and recombinant expression of the mouse PTPS gene, Pts. It is located on chromosome 9C-D and contains six exons with an open reading frame of 144 codons. The derived protein monomer has a molecular mass of 16187 Da and shows 82% and 93% identity to its human and rat counterparts, respectively. The mouse PTPS was expressed in bacterial cells and purified to homogeneity. The kinetic properties of the recombinant protein, apparent Km of approximately 10 microM and k(cat) of 0.27 s(-1), were similar to the native mouse enzyme in liver and brain extracts, and to the corresponding human and rat PTPS.

Presence of high levels of non-degraded gliadin in breast milk from healthy mothers

BACKGROUND

Secretion of dietary antigens into breast milk has been extensively documented. The presence of these antigens is of relevance because they could be involved in the modulation of the immune response in neonates. The objective of this study is to determine the gliadin concentration in milk, colostrum, and serum samples from healthy lactating mothers on a normal diet. Gliadin levels in milk samples from a group of six mothers after a brief period of gluten restriction were also determined. The molecular weight of secreted gliadins was also analysed.

METHODS

Gliadin concentration was determined with a highly sensitive competitive enzyme-linked immunosorbent assay, modified so as to eliminate anti-gliadin antibody interference. The level of gliadin/IgA anti-gliadin immune complexes in milk, colostrum, and serum samples was determined.

RESULTS

Gliadin was detected in all 49 milk samples. Its concentration varied between 5 and 1200 ng/ml (mean, 178 ng/ml). In colostrum (n = 14) gliadin levels were higher (range, 28-9000 ng/ml; mean, 883 ng/ml), not being detectable in one case. Gliadin was detectable in 14 of 31 serum samples, in which levels were lower than in milk and colostrum samples (mean, 41 ng/ml). Neither a correlation between gliadin levels in milk, colostrum, and serum samples from the same subject nor a relation between gluten intake and gliadin concentration in milk samples from six subjects under a 3-day gluten-free diet could be found. Higher levels of immune complexes were observed in colostrum samples than in milk and serum samples. No correlation was detected between gliadin concentration and the level of immune complexes. The analysis of milk and colostrum samples by immunoblotting showed bands of immunoreactive gliadin presenting Mr similar to those of native proteins from wheat extracts.

CONCLUSIONS

Very high levels of gliadin were detected in milk samples from healthy mothers on an unrestricted diet. Gliadin levels were higher than those reported for dietary antigens in other studies. Breast milk contained non-degraded gliadins and gliadin/anti-gliadin IgA immune complexes.

Prevention of food allergy

Development of a food allergy appears to depend on both genetic factors and exposure-especially in early infancy-to food proteins. In prospective studies, the effect of dietary allergy prevention programmes has only been demonstrated in high-risk infants, i.e. infants with at least one first degree relative with documented atopic disease. High-risk infants feeding exclusively on breast milk and/or extensively hydrolysed formula (eHF) combined with avoidance of cow's milk proteins and solid foods during at least the first 4 months of life are found to have a significant reduction in the cumulative incidence of food allergy, especially cow's milk protein allergy/intolerance (CMPA/CMPI), in the first 4 years of life. As no studies have been conducted pertaining to the preventive effect of avoidance of milk and other foods after the age of 4-6 months, recommendation of preventive elimination diets beyond this age is empirically based. In order to reduce costs and to minimize the risks of stigmatisation and malnutrition, it is important to avoid unnecessary restrictive and prolonged diets. A diet period of 4-6 months appears to be sufficient in the majority of infants. At present, eHF are recommended as a substitute for cow's milk. A few high risk infants may benefit from a maternal diet during lactation, but there is no documented beneficial effect of maternal dieting during pregnancy.

Extensively and partially hydrolysed infant formulas for allergy prophylaxis

The allergy preventive effect of extensively (N) and partially (PH) hydrolysed cows' milk formulas compared with a regular formula (RM) was assessed in 155 infants with a family history of allergy. No cows' milk was given during the first nine months of life and no egg and fish up to 12 months of age. Breast feeding mothers avoided the same foods. At weaning the infants were randomised to one of the formula groups. The cumulative incidence of atopic symptoms at 18 months was 51, 64, and 84% in the N, PH, and RM groups, respectively. From 6 to 18 months there were significantly less cumulative atopic symptoms in the N group compared with the RM group, and significantly less than the PH group up to 6 (N = 25%; PH = 46%) and 9 months (N = 34%, PH = 58%). At 9 months significantly fewer infants in the N group (10%) than in the PH group (33%) had a positive skin prick test to eggs. The findings support an allergy preventive effect of an extensively hydrolysed formula, but not of a partially hydrolysed formula, during the first 18 months of life of high risk infants.

Dietary factors influencing levels of food antibodies and antigens in breast milk

The effect of a milk-free diet during late pregnancy and lactation, on levels of cows' milk specific antibodies and antigens in breast milk, was examined. Women with an allergic condition (defined as atopic) were randomly allocated to a milk-free diet (n = 10) or an unrestricted diet (n = 12). Twelve non-atopic women followed an unrestricted diet. A significant reduction (p < 0.001) in beta-lactoglobulin-specific immunoglobulin A and alpha-casein-specific immunoglobulin A levels was observed over the first 5 days in all groups. The mean level of beta-lactoglobulin antigens in breast milk from women who adhered strictly to the milk-free diet was significantly lower than the levels of the atopic group on the unrestricted diet (p < 0.02). The allergy incidence in the infants born in the atopic diet group was significantly lower compared with that of the atopic group on the unrestricted diet.

Antibodies in milk

The immaturity of the infant's immune system and the rapid evolution of pathogens has created a demand for the mother to provide ready made specific defence factors to her offspring. This is achieved during the fetal period by transplacental transport of IgG antibodies, and after birth via IgA antibodies in the breast milk. The breast milk also contains a variety of nonspecific defence factors contributing to its antimicrobial effect. Breast feeding has been shown to decrease morbidity in gastroenteritis, septicemia, otitis media, urinary tract infection, encephalitis, pneumonia, and necrotizing enterocolitis. The antibody content in the mother's milk probably contributes not only to the immediate but also to the long term protection of the infant including both resistance to infection and development of immunological tolerance to harmless environmental antigens.

Human milk proteins may interfere in ELISA measurements of bovine beta-lactoglobulin in human milk

It is widely believed that cow's milk proteins ingested by the mother, in particular beta-lactoglobulin (beta-LG), can pass into breast milk and thus sensitize predisposed infants. However, studies to evaluate bovine beta-LG in human milk have given conflicting results. The aim of this study was to analyse the correlation between the amount of cow's milk in the mother's diet and the presence of bovine beta-LG in breast milk. Human milk samples from 14 healthy non-atopic women on diets with different cow's milk contents were examined. The total concentration of bovine beta-LG or beta-LG immuno-like proteins (beta-LGIP) was determined by enzyme-linked immunosorbent assay (ELISA). Two separation procedures utilizing ELISA plates and an affinity chromatography column were set up to identify the human whey components recognized by the anti-beta-LG antibodies. beta-LGIP reactivities of milk from three groups on different diets were not significantly different. After splitting the antigen-antibody complexes, three main protein components, human lactoferrin, human beta-casein and human alpha-lactalbumin, were identified. This study would suggest that, at least in healthy subjects, false-positive results in ELISA determinations of bovine beta-LG in human milk might be due to cross-reactions between polyclonal antibodies and different protein antigens.