# Sensitization to salmon among occupationally exposed Norwegian salmon processing workers: identification of IgE-reactive proteins

## TL;DR

This study found that 7.3% of Norwegian salmon processing workers are sensitized to salmon allergens, with reactions to proteins beyond the major fish allergen parvalbumin.

## Contribution

The study identifies novel IgE-reactive proteins in salmon beyond parvalbumin, relevant to occupational sensitization.

## Key findings

- 7.3% of workers showed allergic sensitization to salmon, with most reactions to raw muscle and mucus extracts.
- Mass spectrometry identified known and potentially novel allergens in salmon proteins.
- Work-related symptoms were reported by 43 sensitized workers, though few had food-related salmon allergies.

## Abstract

Salmon processing workers are exposed to bioaerosols and are at risk of developing respiratory diseases and other hypersensitivity reactions. The aim of this study was to investigate the prevalence of allergic sensitization to salmon in a study population of Norwegian salmon processing workers and to investigate salmon proteins involved in IgE-binding.

A total of 977 salmon processing workers were tested with skin prick test (SPT) using both in-house salmon extracts, commercial extracts from cod and salmon, and specific IgE (sIgE) to Atlantic salmon (Salmo salar). They were also invited to answer a general questionnaire, including questions on asthma, work-related symptoms, and food-allergy to salmon. Serum from 71 sensitized workers with either a positive SPT and/or elevated sIgE to salmon, were further analyzed by immunoblot, with in-house and commercial protein extracts. Salmon proteins which were most frequently involved in IgE-binding were identified using mass spectrometric analyses of SDS-PAGE protein bands.

We determined a prevalence of allergic sensitization to salmon of 7.3% (n = 71) in the present study population. Fifty-six workers had at least one positive SPT, with most having a reaction to the in-house raw muscle extract (61%), followed by in-house mucus (42%), in-house cooked muscle (17%), commercial cod (11%), commercial salmon (8%), and in-house skin (3%). All sensitized workers had IgE-binding to proteins in at least one of the protein extracts, with immunoblot protocols: mucus (100%), raw muscle (79%), cooked muscle (20%), skin (6%), and commercial cod (24%). Most frequent IgE-binding was seen in the 60–70 and >131 kDa area for mucus, and 60–70 kDa for raw muscle. Work-related symptoms were reported by 43 workers. Only three workers had self-reported allergy to salmon related to food intake, whereas 10 workers had self-reported doctor-diagnosed asthma. With mass spectrometry, known allergens were identified, as well as potentially novel allergens with possible clinical relevance.

Norwegian salmon processing workers are exposed to various salmon tissues at work, containing proteins which might cause allergic sensitization. Allergens other than the major fish allergen parvalbumin, including allergens not previously identified as salmon allergens, seem to play an important role in the occupational setting.