Electrophilic Allergen Screening Assay (EASA)

Binding of a chemical to skin proteins is the first step in the development of allergic contact dermatitis. The EASA is a chemical assay that measures light absorbance or a fluorescent signal in proportion to a chemical’s tendency to bind to proteins.

In 2022, a validation study coordinated by NICEATM completed testing of 20 chemicals using the EASA in 96-well format. Results of this study suggest that the EASA may be a useful non-animal method to identify potential skin sensitizers. The study is summarized in a poster (Reinke et al., Human-Centered Biomedical Research session) presented at the 12th World Congress on Alternatives and Animal Use in the Life Sciences. A peer review of the study was conducted in 2024, and a validation study report is planned for publication in 2025.

Background of the ICCVAM Validation

The EASA was nominated to ICCVAM to evaluate its usefulness in identifying potential skin sensitizers. Initial testing of 10 chemicals showed that the method had sufficiently good reproducibility and accuracy rates to support further evaluation. Scientists with ICCVAM member agencies CPSC and NIST subsequently modified the assay to a 96-well format to increase throughput and accessibility of the assay. Petersen et al. (2022) describes this process, including the incorporation of in-process control measurements to quantify key sources of variability each time the assay is run.

• Nomination cover letter for the EASA from Paul Siegel, PhD, National Institute of Occupational Safety and Health.
• NICEATM Preliminary Evaluation of the EASA.