Identification of allergenic component Tyr p 8 from Tyrophagus putrescentiae and cross-reactivity with Der p 8.

Group 8 mite allergens exhibit sequence homology to glutathione S-transferases (GSTs), such as that from Dermatophagoides pteronyssinus (Der p 8). GSTs have been identified as important allergens in studies of allergens from house dust mites, cockroaches, and fungi. Our objective was to purify the native group 8 allergen from Tyrophagus putrescentiae (nTyr p 8) and generate recombinant Tyr p 8 (rTyr p 8) for immunological characterization. The allergenicity was determined by antibody recognition, IgE inhibition, and triggering of the basophil-sensitized release of histamine, using T. putrescentiae hypersensitivity sera. The results showed that the mRNA transcript of nTyr p 8 is 657 bp long, contains 218 amino acids with a molecular mass of 26 kDa, and exhibits 83% sequence homology to Der p 8. Serum samples from the allergic patients with an IgE-positive response to T. putrescentiae were analyzed to determine their IgE response to rTyr p 8. The results showed that the sera of 48 subjects (45.3%) had specific IgE against rTyr p 8. However, sera of only 19 subjects (17.9%) had specific IgE against rTyr p 8 after D. pteronyssinus absorption. Histamine release was observed from T. putrescentiae-allergic subjects in the presence of rTyr p 8. Both the nTyr p 8 and T. putrescentiae crude extract had been demonstrated to possess GST enzymatic activity. Although the specific binding of serum IgE to rTyr p 8 was only 17.9%, which indicates that rTyr p 8 was not a major allergen, the positive response to rTyr p 8 was due to the cross-reactivity with Der p 8. The group 8 mite allergen might be of use in the design of a suitable allergen for diagnosis and for the development of novel immunotherapies.