Allergological characterisation of the storage mite Acarus gracilis (Acari: Acaridae)

Storage mites of the genus Acarus can be responsible for allergic sensitisation in domestic environments. Acarus gracilis is a frequent species in some geographical regions of the Iberian Peninsula. Since the allergenicity of this mite has not been described before, the objectives of this study were to characterise it immunologically, and to compare it with the closely related and more extensively studied species Acarus siro.

Extracts from A. gracilis and A. siro cultures were characterised by Lowry, 1D and 2D-SDS and IEF. Zymogram, and determination of different enzymatic activities were performed. Skin prick solution of A. gracilis was tested in consecutive patients attending the Hospital of Mérida (Extremadura, Spain). Serum samples from eight individuals with positive skin prick test were collected. IgE determination, immunoblot and immunoblot-inhibition studies were performed.

Extracts of both species showed a very similar protein and allergenic profile. Allergens at 14 and 17 kDa were clearly recognised in both extracts by serum samples. Immunoblot-inhibition studies demonstrated that both extracts were totally inhibited by the opposite one. Enzymatic activity was similar in both cases with the most important differences being in kallikrein, serine protease and collagenase activities.

The storage mite A. gracilis has a similar protein and allergen profile to A. siro and can induce allergic sensitisation. Due to the higher prevalence of this species respect to A. siro in some regions, more studies are needed to determine the clinical significance of sensitisation to this storage mite species.