Tropomyosin in mugwort cross-reacts to house dust mite, eliciting non-Th2 response in allergic rhinitis patients sensitized to house dust mite

Background Mugwort and house dust mite (HDM) are two of the most common inhalant allergens in Asia, however, whether mugwort affects polysensitized HDM+ allergic rhinitis (AR) patients has not been elucidated. Methods Overall, 15,884 AR outpatients were assessed for clinical status. Amino acid sequences of mugwort were determined by mass spectrometry. Afterward, cross-reactivity between mugwort tropomyosin and Dermatophagoides pteronyssinus 10 (Der p10) was analysed by ELISA inhibition and basophil activation experiments. To compare immunologic responses eliciting by two different tropomyosins, peripheral blood mononuclear cells (PBMCs) of HDM-monosensitized patients were stimulated by mugwort, HDM, Der p10 and synthetic peptides representing mugwort tropomyosin respectively. Results Polysensitized HDM+AR patients were mainly sensitized to cat and mugwort, and the positive rate of monosensitized HDM+AR out-clinic patients was increased during the mugwort pollen season. Tropomyosin protein was able to find in mugwort. Synthetic tropomyosin peptide of mugwort activated basophils which were primed by HDM-specific IgE; ELISA inhibition experiment showed synthetic tropomyosin peptide of mugwort inhibited IgE binding to HDM tropomyosin, Der p10. Unlike HDM and Derp 10, mugwort and mugwort tropomyosin mainly induced IFN-γ and IL-17 release in PBMCs of monosensitized HDM+AR patients, but not IL-5. Conclusions Pan-allergen tropomyosin accounts for the cross-reactivity between mugwort and HDM, which reminds HDM+ patients to reduce mugwort exposure in mugwort pollen season in virtue of the tropomyosin induced mild inflammation.