D3.184 - Comparative immunogenicity of mixed versus individual extracts from the storage mites Acarus siro and Tyrophagus putrescentiae

Acarus siro and Tyrophagus putrescentiae, frequently found in stored products and indoor environments, are relevant storage mites contributing to respiratory allergic diseases. Allergen extract mixtures from different species are frequently used for therapeutic purposes. However, demonstrating the potential efficacy and immunogenicity of such mixtures compared to individual extracts is essential to support their use in allergy management. This study investigates the immunological response elicited by combined native extracts of A. siro (AS) and T. putrescentiae (TP) mites with respect to single-species preparations.

Native extracts of AS and TP were manufactured under GMP conditions and characterized (LETI Pharma S.L.U.). Individual and mixture preparations of these extracts were subcutaneously administered in New-Zealand rabbits (n=2/group). Serum samples were collected before and after the immunogenicity study and IgG antibodies specific to both species were detected by ELISA and immunoblot. Finally, the ability of rabbit IgG to inhibit human IgE binding to the allergen was assessed by ELISA inhibition assay using a specific pool of sera from patients sensitized to AS or TP.

Three immunizations with individual or mixture native extracts of AS and TP induced high levels of specific IgG, with ELISA optical density values reaching ~2.0 at 1:10,000 dilution in the final sera of the three groups of immunization. No allergen-specific IgG levels were detected in the pre-immune sera against either mite allergen. Moreover, the induced sIgG antibodies effectively inhibited human IgE binding to the allergen. The mean maximum inhibition percentages were 60.9% (TP group), 90.1% (AS group), and 86.8% (against TP) and 86.7% (against AS) for the mixture group, indicating comparable blocking capacity.

Immunization with mixtures of Acarus siro and Tyrophagus putrescentiae native extracts induced robust IgG responses and demonstrated strong IgE-blocking capacity, comparable to individual extracts. These findings support the potential of mixed storage mite extracts for therapeutic applications, offering broader allergen coverage without compromising immunogenicity.