Children with immediate-type wheat allergy were sensitized to all three fractions of wheat, barley, and rye, with wheat seeming to have the most allergenicity.

Cereals, including those consisting of wheat, are used as a food source worldwide, and cross-reactivity among cereals is a critical issue for the management of wheat allergy, explains Mari Takei, MD. However, few studies have clarified the cross-reactivity among cereals in the immediate-type wheat allergy.

For a study published in Pediatric Allergy and Immunology, Dr. Takei and colleagues sought to clarify the cross-reactivity of the three fractions (albumin/globulin, gliadin, and glutenin fraction) among cereals ingested by children with wheat allergy. “We wanted a better understanding of the cross-reactivity among wheat, barley, and rye in immediate-type wheat allergy,” Dr. Takei says. “To our knowledge, this is the first study to shed light on the in vitro cross-reactivity of each fraction among cereals in immediate-type wheat allergy.”

The study team collected sera from 128 children (median age, 6.3) with immediate-type wheat allergy. The enzyme-linked immunosorbent assay (ELISA) was used to measure specific immunoglobulin E (sIgE) levels against each fraction of wheat, barley, and rye. Inhibition ELISA was conducted to examine cross-reactivities of each fraction among wheat, barley, and rye. An IgE level ≥0.10 kUA/L indicated sensitization to cereals.

Of All Three Fractions, Wheat Had the Strongest Allergenicity

Among all patients, 27% were able to consume barley (barley-tolerant group) and 14% were allergic to barley (barley-allergic group). The remaining 59% had never ingested barley; no one had ever consumed rye.  In the barley-allergic group, the barley sIgE levels were considerably higher in all three fractions. There was no significant difference between the correlation coefficients between wheat sIgE and barley sIgE in the three fractions. Differences in inhibition pattern were observed between barley-allergic and barley-tolerant groups in all the three fractions, based on inhibitor ELISA of barley using wheat as an inhibitor.

Dr. Takei and colleagues observed 100% cross-reactivity of wheat to barley and rye, from the viewpoint of sensitization. “Unlike wheat-dependent, exercise-induced anaphylaxis and baker’s asthma, children with immediate-type wheat allergy were sensitized to all three fractions of wheat, barley, and rye,” Dr. Takei notes. “In addition, wheat sIgE levels in the three fractions were notably higher than those of barley and rye, suggesting that wheat has the strongest allergenicity (Figure).”

In all the fractions, the wheat sIgE levels were considerably higher than those of barley and rye (P≤0.001) and were notably correlated with sIgE levels in each fraction (r=0.887–0.969; P<0.001). Compared with barley and rye, wheat prevented IgE binding to most of the solid phases at lower protein levels in all fractions, based on inhibition ELISA.

Future Studies Needed to Examine Cross-Reactivity to Barley & Rye

In the management of immediate-type wheat allergy, Dr. Takei explains, it is critical to consider sensitization to other cereals caused by in vitro cross-reactivity to wheat, which is a primary source of sensitization.

Dr. Takei adds that future studies are needed to evaluate the clinical cross-reactivity to barley and rye. “In our study, we mainly demonstrated in vitro cross-reactivity among wheat, barley, and rye,” she says. “We could not accurately examine the clinical cross-reactivity. For managing wheat allergies, it’s important to investigating whether patients are at risk for other cereal allergies. Therefore, we would also like to see studies evaluating in vitro cross-reactivity with cereals other than barley and rye, such as those consisting of oats, corn, and rice.”