Ana o 3 sIgE testing increases the accuracy of cashew allergy diagnosis using a two-step model

BACKGROUND

Measurement of cashew-specific IgE (sIgE) is often used to confirm sensitization but does not reliably diagnose clinical allergy. Ana o 3 is the dominant cashew allergen detected in 75-100% of patients with cashew allergy but not currently used in clinical practice.

OBJECTIVES

To determine if component-resolved diagnostics using specific IgE to the 2 S albumin from cashew, Ana o 3, improves the accuracy of diagnosing cashew allergy, thereby circumventing the need for an oral food challenge (OFC) in some patients.

METHODS

A population-based sample of 5276 children was recruited at age 1 year and followed up at age 6 years. Children with positive cashew skin prick test at age 6 underwent an OFC to clarify allergy status. Forty-seven children (mean age 5.02 ± 0.2) (33 cashew-allergic and 14 cashew-tolerant) had cashew sIgE and Ana o 3 sIgE quantified by ImmunoCAP System FEIA.

RESULTS

A cutoff of >0.32 kUA/L for Ana o 3 sIgE provided 95% specificity and 90% sensitivity and correctly identified 90% of clinical cashew allergy. At the same specificity, the sensitivity for cashew sIgE (>8.5 kUA/L) was only 26%. Sequential measurement of cashew sIgE followed by Ana o 3 sIgE diagnosed 90% of children with cashew allergy without the need for an OFC.

CONCLUSION

Ana o 3 sIgE testing provides higher diagnostic accuracy than cashew sIgE. Sequential measurement of cashew sIgE followed by Ana o 3 removed the need for a food challenge from 66% down to 12.8% (5-fold) of children compared with cashew sIgE testing alone.

The prevalence of food allergy and other allergic diseases in early childhood in a population-based study: HealthNuts age 4-year follow-up

BACKGROUND

The HealthNuts study previously reported interim prevalence data showing the highest prevalence of challenge-confirmed food allergy in infants internationally. However, population-derived prevalence data on challenge-confirmed food allergy and other allergic diseases in preschool-aged children remain sparse.

OBJECTIVE

This study aimed to report the updated prevalence of food allergy at age 1 year from the whole cohort, and to report the prevalence of food allergy, asthma, eczema, and allergic rhinitis at age 4 years.

METHODS

HealthNuts is a population-based cohort study with baseline recruitment of 5276 one-year-old children who underwent skin prick test (SPT) to 4 food allergens and those with detectable SPT results had formal food challenges. At age 4 years, parents completed a questionnaire (81.3% completed) and those who previously attended the HealthNuts clinic at age 1 year or reported symptoms of a new food allergy were invited for an assessment that included SPT and oral food challenges. Data on asthma, eczema, and allergic rhinitis were captured by validated International Study of Asthma and Allergies in Childhood questionnaires.

RESULTS

The prevalence of challenge-confirmed food allergy at age 1 and 4 years was 11.0% and 3.8%, respectively. At age 4 years, peanut allergy prevalence was 1.9% (95% CI, 1.6% to 2.3%), egg allergy was 1.2% (95% CI, 0.9% to 1.6%), and sesame allergy was 0.4% (95% CI, 0.3% to 0.6%). Late-onset peanut allergy at age 4 years was rare (0.2%). The prevalence of current asthma was 10.8% (95% CI, 9.7% to 12.1%), current eczema was 16.0% (95% CI, 14.7% to 17.4%), and current allergic rhinitis was 8.3% (95% CI, 7.2% to 9.4%). Forty percent to 50% of this population-based cohort experienced symptoms of an allergic disease in the first 4 years of their life.

CONCLUSIONS

Although the prevalence of food allergy decreased between age 1 year and age 4 years in this population-based cohort, the prevalence of any allergic disease among 4-year-old children in Melbourne, Australia, is remarkably high.

Food-allergic infants have impaired regulatory T-cell responses following in vivo allergen exposure

BACKGROUND

Regulatory T cells (Tregs) are critical for development of oral tolerance, and studies suggest that dysfunction of Tregs may lead to food allergy. However, to date, no study has investigated Treg responses following in vivo exposure to peanut or egg allergens in humans.

OBJECTIVES

To examine changes in peripheral blood CD4(+) CD25(+) Foxp3(+) Treg populations (total, activated and naive) in food-allergic, food-sensitized but tolerant, and healthy (non-sensitized non-allergic) patients over time following in vivo allergen exposure.

METHODS

A subset of infants from the HealthNuts study with egg or peanut allergy (n = 37), egg or peanut sensitization (n = 35), or who were non-sensitized non-allergic (n = 15) were studied. All subjects underwent oral food challenge (OFC) to egg or peanut. PBMCs were obtained within 1 h of OFC (in vivo allergen exposure), and Treg populations enumerated ex vivo on day 0, and after 2 and 6 days rest in vitro.

RESULTS

Non-allergic infants showed stable total Treg frequencies over time; food-sensitized infants had a transient fall in Treg percentage with recovery to baseline by day 6 (6.87% day 0, 5.27% day 2, 6.5% day 6); and food-allergic infants showed persistent reduction in Treg (6.85% day 0, 5.4% day 2, 6.2% day 6) following in vivo allergen exposure. Furthermore, food-allergic infants had a significantly lower ratio of activated Treg:activated T cells (10.5 ± 0.77) at day 0 compared to food-sensitized (14.6 ± 1.24) and non-allergic subjects (16.2 ± 1.23).

CONCLUSION

Our data suggest that the state of allergen sensitization is associated with depletion of Treg following allergen exposure. Impaired capacity to regenerate the Treg pool following allergen exposure may be an important factor that determines clinical allergy vs. sensitization without allergic reaction.

Characterization of plasma cytokines in an infant population cohort of challenge-proven food allergy

BACKGROUND

Sensitization to food allergens indicates the production of food-specific IgE; however, sensitization is not a definite indicator of allergic reaction upon ingestion (N Engl J Med, 344, 2001, 30: J Allergy Clin Immunol, 120, 2007, 491). Currently, food challenge is the best approach to identify the presence or absence of allergy. While 95% positive predictive values (PPVs) thresholds for sIgE can assist with identifying increased likelihood of allergy among those who are sensitized, there are no specific biological markers that differentiate between allergic and sensitized individuals.

OBJECTIVES

To determine whether plasma serum cytokine profiles predict (i) sensitization to peanut and egg and (ii) food allergy among sensitized infants.

METHODS

Peanut-sensitized (PT) and egg-sensitized 14-month-old infants and nonsensitized controls enrolled in HealthNuts, a population-based study of food allergy, underwent an oral food challenge (OFC). Blood was collected within 1 h after OFC. Serum levels of Th1, Th2 and regulatory cytokines were determined in allergic (n = 79), sensitized (n = 40) and nonsensitized, nonallergic (n = 37) infants by multiplex assay.

RESULTS

Food-sensitized infants had significantly higher plasma IL-4, IL-13, IL-12p70 and lower IL-10 levels compared to nonsensitized infants. IL-10 and IL-6 levels were significantly higher in sensitized compared with allergic infants. Egg-allergic infants had significantly higher IL-13 and IL-12p70 levels compared to peanut-allergic (PA) infants.

CONCLUSION

Levels of Th2-related cytokines in plasma are higher in food-sensitized infants, irrespective of clinical food allergy status. In contrast, IL-10 levels appear to predict food allergy among sensitized infants. Differences in IL-13 and IL-12p70 between egg- and peanut-allergic infants could help explain the different resolution rates of the allergies.