Identification of IgE and IgG binding epitopes on β- and κ-casein in cow's milk allergic patients

BACKGROUND: Cow's milk allergy (CMA) affects 2.5% of children aged less than 2 years of age. Although beta- and kappa-casein are considered among the major allergens responsible for CMA, no data are available on their allergenic epitopes in humans. OBJECTIVE: The aim of the study was to identify IgE- and IgG-binding epitopes on beta- and kappa-casein and to determine whether the pattern of epitope recognition is associated with the natural history of CMA. METHODS: Overlapping decapeptides representing the entire length of beta- and kappa-casein, respectively, were synthesized on a cellulose-derivatized membrane. Sera from 15 milk-allergic children, 4-18 years of age, with high levels of specific IgE antibodies to cow's milk were used to identify IgE- and IgG-binding epitopes. In addition, IgE epitopes were screened with pooled or individual sera from younger patients aged less than 3 years and who had low levels of specific serum IgE, who are likely to outgrow CMA. RESULTS: Six major and three minor IgE-binding epitopes, as well as eight major and one minor IgG binding regions, were identified on beta-casein. Eight major IgE-binding epitopes, as well as two major and two minor IgG-binding epitopes, were detected on kappa-casein. Three of the IgE binding regions on beta-casein and six on kappa-casein were recognized by the majority of patients in the older age group, but not by the younger patients. CONCLUSION: Information regarding the immunodominant epitopes in beta- and kappa-casein may be important for understanding the pathophysiology and natural history of CMA. Differences in epitope recognition may be useful in identifying children who will have persistent milk hypersensitivity.     

Cow's milk IgE and IgG antibody responses to cow's milk formulas

For comparison of the antigenicity and allergenicity of three cow's milk formulas, serum IgE antibodies to cow's milk, β‐lactoglobulin and casein, and IgG antibodies to β‐lactoglobulin were analyzed in 94 infants with a family history of allergy. They were participating in a randomized trial comparing the allergy prophylactic effect of feeding an extensively hydrolyzed (N), a partially hydrolyzed (PH), and a regular cow's milk formula (RM). Only infants who had been formula‐fed for 3 months or more were included. IgE antibodies to cow's milk proteins were more common in the RM group (22/34) than in the N (2/31) and PH groups (3/29). There was a strong correlation between sensitization to cow's milk and β‐lactoglobulin ( r =0.85, P <0.001). The IgG responses to β‐lactoglobulin were low in the N group, intermediate in the PH group, and high in the RM group. High responses, as well as detection of IgE antibodies, were associated with development of atopic disease. The low antigenicity and allergenicity of the extensively hydrolyzed formula support its use in allergy prophylaxis. The partial hydrolysate seemed to be less suitable for this purpose.     

B-cell epitopes as a screening instrument for persistent cow's milk allergy

BACKGROUND: Cow's milk is one of the most common causes of food allergy in the first years of life. We recently defined IgE-binding epitopes of all 6 major cow's milk proteins (alpha(s1)-, alpha(s2)-, beta-, and kappa-casein; alpha-lactalbumin; and beta-lactoglobulin) and had some evidence suggesting that IgE antibodies from patients with persistent cow's milk allergy (CMA) recognize different epitopes on cow's milk proteins than do those from patients who were likely to outgrow their allergy. OBJECTIVE: In this study we sought to assess whether recognition of IgE antibodies of certain epitopes of cow's milk proteins would clearly separate the patients with life-long CMA from those who will become clinically tolerant to cow's milk. METHODS: According to the known IgE-binding regions of cow's milk proteins, 25 decapeptides of alpha(s1)-casein, alpha(s2)-casein, kappa-casein, alpha-lactalbumin, and beta-lactoglobulin, comprising the core epitopes, were synthesized on a cellulose-derivatized membrane. Sera from 10 patients with persistent CMA and 10 patients who subsequently outgrew their milk allergy were used to investigate the differences in epitope recognition. RESULTS: Five IgE-binding epitopes (2 on alpha(s1)-casein, 1 on alpha(s2)-casein, and 2 on kappa-casein) were not recognized by any of the patients with transient CMA but showed binding by the majority of the patients with persistent allergy. The presence of IgE antibodies against at least 1 of 3 epitopes (amino acid [AA] 123-132 on alpha(s1)-casein, AA 171-180 on alpha(s2)-casein, and AA 155-164 on kappa-casein) identified all patients with persistent CMA. CONCLUSIONS: The presence of IgE antibodies to distinct allergenic epitopes of cow's milk proteins can be used as a marker of persistent CMA. Prospective studies are needed to investigate the usefulness of these informative epitopes in predicting life-long CMA in young children.     

The recognition pattern of sequential B cell epitopes of beta-lactoglobulin does not vary with the clinical manifestations of cow's milk allergy

BACKGROUND: beta-Lactoglobulin (BLG) represents one of the major allergens causing cow's milk allergy (CMA) - a disease with a wide spectrum of clinical symptoms. The aim of this study was to evaluate sequential B cell epitopes of BLG by the Pin-ELISA method. Furthermore, we wanted to investigate a possible association of the IgE recognition patterns in sera of patients with BLG sensitization and the type of clinical reactions following contact with cow's milk. METHODS: Overlapping sequential decapeptides corresponding to the amino acid sequence of BLG were used in Pin-ELISAs specific for human IgE. Tested sera were from 14 individuals with CMA, 8 of them with a history of immediate systemic reactions and 6 with delayed skin reactions following contact with cow's milk. All of them showed specific IgE antibodies to BLG in the CAP-RAST. Control sera were from 5 healthy nonallergic individuals. RESULTS: All sera from BLG-sensitized individuals showed IgE binding with one region of BLG corresponding to amino acids 95-113. Furthermore, individual sera showed reactions with two further regions, 12-27 and 124-135. Inhibition of IgE binding to BLG with one soluble synthetic peptide confirmed the major epitope. No differences were found in the B cell epitope recognition pattern to BLG in the two groups of patients with CMA, characterized by acute systemic or delayed skin reactions. CONCLUSIONS: Using IgE Pin-ELISAs we were able to confirm previously described sequential B cell epitopes of BLG. However, the recognition pattern of one of the major cow's milk allergens is not predictive of the clinical type of reaction.     

Role of conformational and linear epitopes in the achievement of tolerance in cow's milk allergy

BACKGROUND: Cow's milk (CM) is one of the leading causes of food allergy in children. However, approximately 85% of milk-allergic children become clinically tolerant to CM within the first 3 years of life. The mechanisms involved in the achievement of tolerance remain unknown. OBJECTIVE: To study whether IgE antibodies from children with persistent cow's milk allergy (CMA) differ from children who become clinically tolerant in their ability to recognize linear and conformational epitopes of alpha(s1)- and beta-casein. METHODS: Thirty-six milk-allergic children were included in the study: 11 of the children became clinically tolerant, and 25 had persistent CMA. Blood was obtained from all patients during the time they showed clinical reactions to milk challenge. Six non-milk-allergic children served as controls. Specific IgE antibodies against linear (denatured) as well as conformational (native) milk proteins were determined by probing dot-blots with patients' sera. In addition, selected decapeptides from alpha(s1)- and beta-casein, previously found to be suggestive of persistent CMA, were synthesized on a cellulose-derivatized membrane and probed with individual sera from 10 patients who outgrew CMA and from 10 patients with persistent CMA. RESULTS: Analysis of immunodot-blots showed that, in comparison to tolerant patients, milk-allergic children with persistent symptoms had a significantly higher ratio of specific IgE antibodies to linearized than to native alpha- and beta-casein (P < 0.005 and P < 0.02, respectively). Comparing the selected decapeptides, six of the 10 patients with persistent allergy recognized the peptide corresponding to amino acids 69-78 from alpha(s1)-casein while none of the patients who outgrew CMA had IgE binding to this epitope. CONCLUSION: Patients with persistent milk allergy possess higher detectable levels of IgE antibodies to linear epitopes from alpha(s1)- and beta-casein than children who have achieved tolerance. Specific IgE binding to particular linear epitopes in alpha(s1)-casein may be a predictive factor for persistence of CMA.     

Total IgE, specific antibodies to cow's milk proteins, beta-lactoglobulin and eczema in one month infants

Total IgE, specific IgE.IgA.IgG.IgM antibodies to whole cow's milk and beta-lactoglobulin were measured in 32 term and 23 premature infants. 1) The term infants who developed eczema till one month had significantly high specific IgG titers to whole cow's milk and beta-lactoglobulin in cord blood serum. It is concluded that specific IgG antibody to whole cow's milk and beta-lactoglobulin in cord blood serum have predictive value for the development of eczema till one month. 2) Some of mixed feeding premature infants produced specific IgE.IgA.IgG.IgM antibodies to whole cow's milk and beta-lactoglobulin till one month. These infants produced various kind of specific antibodies to whole cow's milk and beta-lactoglobulin. 3) The premature infants who developed eczema at one month had significantly high specific IgA.IgG titers to cow's milk and high specific IgA titers to beta-lactoglobulin in serum at one month. These infants had a tendency to show high total IgE value and high specific IgM titers to cow's milk and high specific IgG.IgM titers to beta-lactoglobulin. It is concluded that specific antibodies to whole cow's milk and beta-lactoglobulin are responsible for the development of eczema in one month infants.     

Adult onset of cow's milk protein allergy with small-intestinal mucosal IgE mast cells

We report a female patient with adult onset of cow's milk protein allergy. For 1 year, she experienced repeated gastrointestinal symptoms and had a single exercise-induced anaphylactic reaction. In addition to positive skin tests and specific IgE to milk proteins and a positive challenge test, immunohistochemistry of the small intestine showed a marked increase of IgE-positive mast cells. This finding is highly specific and could provide an additional tool for diagnosing cow's milk protein allergy and possibly also other food allergies.     

Allergenicity of major cow's milk and peanut proteins determined by IgE and IgG immunoblotting

BACKGROUND: Specific IgG antibodies are frequently observed in food-allergic patients. However, the allergen-fraction specificity of IgG antibodies in relation to IgE antibodies is not well defined. Our aim was to determine the IgE and IgG antibody profile to major cow's milk and peanut-antigen fractions in food-allergic patients and tolerant individuals. METHODS: Sera were collected from 10 patients allergic to cow's milk and 10 patients allergic to peanuts, as well as from 20 control subjects. Cow's milk and peanut proteins were migrated on SDS-PAGE and immunoblotted for IgE, IgG, and IgG4 antibodies. Food-specific IgE concentrations were measured by CAP System FEIA, and IgG and IgG4 concentrations by ELISA. RESULTS: In food-allergic children, similar fraction-specific IgE, IgG, and IgG4 antibody-binding profiles to the major cow's milk or peanut antigens were found. In nonallergics, the presence of fraction-specific IgG antibodies was mostly dependent on regular ingestion of the food. The presence of specific antibody on immunoblots correlated with their quantitative measurement. The mean value for specific IgE in cow's milk-allergic patients was 450 +/- 1,326 IU/ml, and 337 +/- 423 IU/ml in peanut-allergic patients. Specific IgG antibody values in milk-allergic patients were not different (median OD 1.5, range 0.3-2.3) from controls (median OD 1, range 0.2-1.8). However, in peanut-allergic patients, IgG concentrations were significantly higher than in controls (OD 1.2 [0.5-1.3] vs 0.5 [0.3-0.7]; P< 0.01). CONCLUSIONS: Similar fraction-specific IgE and IgG antibody profiles in allergic individuals suggest a common switching trigger involving both isotypes. Intrinsic allergenicity might explain identical IgG antibody fraction specificity in nonallergics and in allergics. The presence of IgG antibodies in nonallergics was related to regular ingestion of the food.     

A mouse monoclonal IgE antibody anti bovine milk beta-lactoglobulin allows studies of allergy in the gastrointestinal tract.

A monoclonal IgE antibody directed against bovine milk beta-lactoglobulin (beta-LG) was produced by fusion of NSI myeloma cells with spleen cells of Balb/c mice immunized with alum-precipitated beta-LG. This antibody was found by radioimmunoassay to react with both native and aggregated beta-LG, but a positive passive cutaneous anaphylaxis reaction (PCA) was evident only with aggregated beta-LG. 1 ng of this purified antibody was capable of eliciting a PCA. The chemical and physical properties were characterized by amino acid and carbohydrate analysis and by ultracentrifugation. The epsilon-chain had an apparent molecular weight of 86,000 +/- 2,000 by polyacrylamide gel electrophoresis. An immediate hypersensitivity reaction within the gut was elicited by intravenous (i.v.) administration of the hybridoma ascitic fluid followed by feeding with aggregated beta-LG. Accumulation of liquid within the small intestine and diarrhoea were evident 30-90 min later. Intravenous injection of carbon particles revealed an increased permeability of the venulae from the submucosa and serosa. Histological examination showed oedema within the villae, without modification of the epithelium.     

Diagnostic value of skin-prick and patch tests and serum eosinophil cationic protein and cow's milk-specific IgE in infants with cow's milk allergy

The diagnosis of cow's milk allergy is based on a clinical response to an elimination-challenge test with cow's milk. We studied the usefulness of the skin-prick and patch tests and measurement of cow's milk-specific IgE and eosinophil cationic protein in serum as diagnostic tools for cow's milk allergy in a cohort of 6209 unselected infants followed from birth for the development of cow's milk allergy. Of the 239 infants challenged with cow's milk, 118 showed a positive and 121 a negative response at a mean age of 6.9 months. A positive reaction to a skin-prick test with cow's milk (> or = 3 mm) was seen in 72 (61%) and 29 (24%) infants with positive and negative challenges, elevated serum cow's milk-specific IgE (> or = 0.7 kU/L) in 52 (45%) and 15 (13%) infants, a positive reaction to patch test with cow's milk protein fractions in 26 (26%) and eight (8%) infants, and elevated serum eosinophil cationic protein (> or = 20 microg/L) in 22 (21%) and seven (13%) infants, respectively. Parallel use of the four tests with the above-mentioned cut-off values correctly classified 73% of the infants with a sensitivity of 0.76 and a specificity of 0.67. An immediate reaction to cow's milk challenge correlated with skin prick test positivity and elevated serum milk-specific IgE, and tended to correlate with patch test positivity. No single test or parallel use of the four tests could predict the challenge outcome acceptably in this prospectively followed, unselected cohort of 6209 infants. A positive reaction to one or more tests needs to be confirmed by a challenge test and a negative response to all four tests does not rule out the possibility of cow's milk allergy.