# IgE-Crosslinking-Induced Luciferase Expression Test as a Sensitive Indicator of Anisakis Allergy

## TL;DR

This study shows that the EXiLE test is a sensitive and useful method for diagnosing Anisakis allergy and tracking changes in IgE levels over time.

## Contribution

The study demonstrates the EXiLE test's effectiveness in diagnosing Anisakis allergy and monitoring IgE dynamics.

## Key findings

- EXiLE test results correlated strongly with Anisakis-specific IgE levels measured by CAP-FEIA.
- The EXiLE test detected IgE binding to proteins ≥40,000 Da in Anisakis worm protein.
- EXiLE levels changed over time in patients, reflecting shifts in specific IgE antibody levels.

## Abstract

Background: Anisakis allergy has been increasing, and the diagnosis of it is based on specific serum IgE detection. Recently, the IgE-crosslinking-induced luciferase expression (EXiLE) test has been proposed as convenient tool for detecting functionally specific IgE antibodies. Here, we investigated if the EXiLE test is a useful tool in the diagnosis of Anisakis allergy. Methods: HuRa-40 cells were sensitized using six serum types from three patients with Anisakis allergy at the time of the initial test and after 6–12 months. Thereafter, various concentrations of Anisakis worm protein (AWP) were reacted to measure the degree of EXiLE. The degree of EXiLE was compared with Anisakis-specific IgE antibody levels measured by the CAP-FEIA method, and the IgE-antibody-binding protein profile was examined using IgE immunoblotting. Results: The results showed a good correlation between the CAP-FEIA values and EXiLE obtained with 5 μg/mL of AWP (R = 0.91, p < 0.01), a strong response on IgE immunoblotting in the region containing proteins weighing ≥40,000 Da. In addition, after the onset of Anisakis allergy, the degree of serum EXiLE decreased in two patients whose Anisakis-specific IgE antibody levels decreased over time but increased in one patient whose specific IgE antibodies increased after repeated antigen sensitization. Conclusions: Based on these data, the AWP-induced EXiLE test seemed to be useful and convenient for the diagnosis of Anisakis allergy, supplementing specific IgE determinants. After allergy onset, the use of this method to observe changes in specific IgE levels over time may be important for predicting the risk of recurrence.