Background Drosophila melanogaster, otherwise known as the fruit fly is commonly used in laboratory animal research. We have reported (Jones, Blair et al. 2017) that laboratory workers (n=286) exposed to fruit flies have an overall sensitisation prevalence of 6%, based on measuring allergen-specific IgE by radioallergosorbent test to a whole fruit fly extract. Although IgE binding to fruit fly extract was detected, the allergenic proteins responsible for IgE binding have not been identified.

Objective To identify allergenic proteins from a fruit fly extract

Methods Fruit flies were collected from the workplace, extracted overnight in 0.01 mol/L ammonium carbonate at 4°C, dialysed against distilled water and lyophilised. SDS-PAGE was used to separate 150 µg of the extract according to protein molecular weight. Extracted proteins binding to serum specific IgE were detected with Western blotting, using 50 µl of sera from fruit fly sensitised workers (n=3). An alkaline phosphatase conjugated mouse anti-human IgE secondary antibody and NBT/BCIP chromogenic substrate were used in detection. Images were acquired with a ChemiDoc MP and the molecular weight of allergenic proteins determined with a 10–250 kDa prestained protein ladder (ThermoScientific) on ImageLab software (v5.2.1).

Results From the fruit fly extract, six distinct proteins binding to serum specific IgE were observed (figure 1). In three sensitised workers, IgE binding to proteins with molecular weights of ∼107 and 76 kDa was observed. For one individual, IgE binding was present to an additional four proteins from the fruit fly extract, with molecular weights of ∼183, 54, 28 and 12 kDa. In a control blot, we did not observe any non-specific binding to the fruit fly extract.

Conclusions There are at least six distinct proteins from a fruit fly extract with IgE binding properties of an allergen. Currently, these proteins are not characterised as allergens in protein databases. We will carry out further proteomic testing to characterise these unknown allergens.

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Abstract S102 Figure 1

Western blot detection of serum specific lgE binding proteins from l50μg of fruit fly extract. 50 µl of three individual sera, an alkaline phosphatase conjugated mouse anti-human lgE secondary antibody and NBT/BCIP chromogenic substrate were used to detect proteins. Blots were also performed with pooled sera from the three individuals and with no sera (control).