Identification of crab proteins that elicit IgE reactivity in snow crab–processing workers

Background The expanding snow crab–processing industry has resulted in increased numbers of workers at risk of occupational allergy. Objective Our study is to identify relevant allergenic proteins in cooked snow crab meat (CM) and crab water (CW) used for cooking for improved remediation, diagnosis, and treatment. Methods Extracts were prepared from CM extracts, CW extracts, and an air-filter collection near the crab cooker. Of the 207 workers, 24 with the highest IgE antibody reactivity to CM and CW extracts, as determined by using RASTs, were tested for reactivity to nitrocellulose membranes containing CM and CW proteins separated with SDS-PAGE. A 3-serum pool was similarly incubated against nitrocellulose-bound proteins from air samples collected near the crab cooker. Results Of the 207 sera tested, 27 and 39 sera exhibited positive IgE antibody reactivity (≥2%) to CM and CW extracts, respectively. Twenty-two of 24 sera with the highest RAST activity (≥3.5% binding) demonstrated IgE binding to multiple proteins (13.6-50 kd). A majority of the sera reacted to 4 proteins: 79% and 71% to a 34.0-kd protein, 79% and 42% to a 25-kd protein, 67% and 71% to an 18.5-kd protein, and 75% to a 14.4-kd protein in both CM and CW extracts, respectively. The pool of IgE-positive sera blotted against the air-filter extract reacted to 14.4-, 18.5-, 34.0-, 43.2-, and 50-kd proteins present in both crab extracts. Conclusion Four major IgE-reactive proteins were identified in CM extracts, CW extracts, and air-filter eluate. Analysis of any potential association of protein reactivity with disease suggested crab proteins at 34.0 and 14.4 kd might be more relevant.