Myxomycete (slime mold) spores: unrecognized aeroallergens?

Background: Myxomycete spores are present in the outdoor air but have not been studied for allergenicity.

Objective: To determine whether patients with seasonal allergic rhinitis (SAR) symptoms are sensitized to myxomycete spores.

Methods: Myxomycete specimens were collected in the field. Nine species of myxomycetes were collected and identified: Arcyria cinerea, Ceratiomyxa fruticulosa, Fuligo septica, Hemitrichia clavata, Lycogala epidendrum, Metatrichia vesparium, Stemonitis nigrescens, Tubifera ferruginosa, and Trichea favoginea. Allergen extracts were made for each species. Protein content of each extract was measured by bicinchoninic acid assay. Protein electrophoresis was performed. Subjects with a history of SAR symptoms were enrolled, and allergy skin prick testing was performed with each extract.

Results: Protein content of the extracts ranged from 1.05 to 5.8 mg/mL. Protein bands were seen at 10 to 250 kD. Allergy prick testing was performed in 69 subjects; 42% of subjects had positive prick test results for at least 1 myxomycete extract, with 9% to 22% reacting to each extract. Five of the 12 subjects who tested negative for all allergens on the standard aeroallergen panel had positive prick test results for myxomycetes.

Conclusion: Forty-two percent of subjects with SAR were sensitized to myxomycete spores. A significant subset of subjects who had SAR symptoms and otherwise negative skin test results showed sensitization to myxomycetes. These spores are present in the outdoor air during the summer and autumn and might be significant aeroallergens.