Food allergy ladders: When to use them?

Fish Allergenicity Ladder and Parvalbumin Epitopes for Predicting Clinical Cross-Reactivity and Reintroduction in Chinese Population

BACKGROUND

IgE-mediated fish allergy has long been considered an umbrella term due to the high cross-reactivity of parvalbumin, the major fish allergen. Yet, clinical tolerance to certain fish highlights allergenicity differences. In this study, we sought to construct a fish allergenicity ladder and identify fish parvalbumin epitopes to improve the diagnosis of fish allergy.

METHODS

Reported clinical history and the serum-specific IgE (sIgE) responses of 200 Chinese subjects with suspected fish allergy were collected and analyzed, while the relative parvalbumin content in different fish was measured for the construction of a fish allergenicity ladder. Double-blind placebo-controlled food challenge (DBPCFC) and open challenge against salmon, grass carp, and grouper were performed in 58 selected patients for validation of the ladder. Epitope mapping was performed by peptide array against parvalbumins of salmon (both β-1 and β-2), cod, grouper, and grass carp with sera from fish allergic (n = 11), partial fish tolerant (n = 12), and complete fish tolerant (n = 5) patients diagnosed based on oral food challenge outcome.

RESULTS

The distribution pattern of reported history of fish allergy and tolerance, sIgE and molecular data, as well as their strong positive correlation led to the construction of a 3-step fish allergenicity ladder comprising: step 1 of the least allergenic fishes (tuna, halibut, salmon and cod), steps 2 of moderately allergenic fishes (herring and grouper) to step 3 of highly allergenic fishes (catfish, grass carp and tilapia). Epitope mapping revealed one epitope from grouper parvalbumin (AA64-78) for diagnosing general fish allergy and one epitopic region from salmon parvalbumin (AA19-33) as a biomarker of specific fish tolerance. Only epitope-specific IgE differentiated these patients but not sIgE to fish extract or parvalbumin.

CONCLUSION

The fish ladder and epitopes discovery can precisely differentiate fish-allergic and tolerant subjects and guide fish reintroduction by stepping up the ladder, which innovates fish allergy care in the next millennium.

The utility of casein skin prick test and IgE values in predicting anaphylaxis and reactivity to baked milk

BACKGROUND

Most children with milk allergy can tolerate baked milk (BM); however, a small percent still react to it. Identifying indicators that might forecast potential reactions to baked goods is essential.

OBJECTIVE

To determine the predictive factors and some decision points for estimation of BM reactivity and severe reactions.

METHODS

A cross-sectional study was performed. Participants who were reactive to unheated milk underwent an oral food challenge with BM. The reactive group was classified into anaphylactic and non-anaphylactic reaction categories. The IgE and skin prick test (SPT) levels of milk and its components were compared among these groups.

RESULTS

The study was conducted with 110 patients. The median age of participants was 16 (IQR: 12-31) months. BM reactivity was observed in 41% (n = 46/110) of the patients. The optimal cutoff point for BM reactivity was 4.68 kIU/L for casein specific IgE (sIgE) (84% specificity, 75% sensitivity, area under the curve [AUC]: 0.827) and 7 mm for casein SPT (87.2% specificity, 51.1% sensitivity, AUC: 0.721) (P < .001, P < .001). The positive decision point for anaphylaxis for casein sIgE was 34 kIU/L (95% specificity, 47.6% sensitivity, AUC: 0.707). In the group younger than 24 months old, the cutoff values for casein sIgE were found to be 5.4 kIU/L (95% specificity, 66.6% sensitivity, AUC: 0.844) and casein SPT at 7 mm (91% specificity, 37% sensitivity, AUC: 0.708) (P < .001, P = .002).

CONCLUSION

Our investigation revealed that the most accurate indicator for BM reactivity was casein sIgE and SPT. Although we established a threshold for severe reaction with BM in our study population, we consider that our findings require validation before therapeutic implementation.

Effects of Food Processing on Allergenicity

PURPOSE OF REVIEW

There is an increasing awareness among clinicians that industrial and household food processing methods can increase or decrease the allergenicity of foods. Modification to allergen properties through processing can enable dietary liberations. Reduced allergenicity may also allow for lower risk immunotherapy approaches. This review will equip physicians, nurses, dieticians and other health care providers with an updated overview of the most clinically oriented research in this field. We summarize studies assessing the allergenicity of processed foods through clinically accessible means, such as oral food challenges, skin prick tests, and sIgE levels.

RECENT FINDINGS

Baking, boiling, canning, fermenting, pasteurizing, peeling, powdering, and roasting heterogenously impact the likelihood of reactivity in egg-, milk-, peanut- and other legume-, tree nut-, fruit-, and seafood-allergic patients. These variations may be due to the use of different temperatures, duration of processing, presence of a matrix, and the specific allergens involved, among other factors. Accurate prediction of tolerance to processed allergens with skin prick tests and sIgE levels remains largely elusive. Food allergy management strategies, especially with milk and egg, have capitalized on the decreased allergenicity of baking. Many milk- and egg-allergic patients tolerate baked and heated forms of these allergens, and the use of these processed foods in oral immunotherapy (OIT) continues to be extensively investigated. Heat is also well recognized to reduce allergic symptoms from some fruits and vegetables in food-pollen syndrome. Other forms of processing such as boiling, fermenting, and canning can reduce allergenicity to a diverse array of foods. Roasting, on the other hand, may increase allergenicity. The application of food processing to food allergy treatments remains largely unexplored by large clinical studies and provides a key avenue for future research. The recognition that food allergy represents a spectrum of hypersensitivity, rather than an all-or-nothing phenomenon, has led to approaches to enable dietary liberation with processed, less-allergenic foods and their use in food allergy immunotherapies.

Food Protein-Induced Allergic Proctocolitis: Real-World Experience from an Italian Cohort

Background/Objectives: Food protein-induced allergic proctocolitis (FPIAP) is a non-IgE-mediated food allergy, usually presenting as bloody stools in breastfed, well-appearing, and regularly growing infants. The aim of our study was to describe the clinical features of Italian infants affected by FPIAP and their management and natural history in a real-life setting. Methods: A retrospective, observational study was performed at two tertiary pediatric hospitals (Florence and Trieste), including FPIAP-diagnosed infants between 2012 and 2022. Results: Most of the 100 enrolled patients were breastfed (68.0%), and the majority of those who underwent diagnostic tests (n = 51) showed normal hemoglobin and total IgE levels. A maternal elimination diet was performed in 69.0%, mostly for milk only, but 40.6% underwent multiple elimination diets. The remission rate was high both in breastfed infants (76.8%) and in those who received extensively hydrolyzed formula (81.8%). Nine subjects were left on a free diet, but six were lost at follow-up. The median time of complete remission was 30 days (IQR 14-60). Culprit food reintroduction was tolerated at a median age of 8 months (IQR 6-11), in ladder modality (for hen's egg and cow's milk) in 61.7%. Nine patients relapsed (14.3%) upon reintroduction with no associated variables identified at the regression analysis. The relapse rate was slightly higher when trigger food reintroduction was attempted > 12 months (16.7%) versus <12 months (13.0%). Conclusions: In our population, FPIAP had, as expected, a benign evolution. The early reintroduction of the suspect food in a gradual manner for cow's milk and hen's egg leads to good tolerance within the first year in most patients, avoiding unnecessary elimination diets.