Characterization and cross-reactivity assessment of group-29 allergens originating from Dermatophagoides pteronyssinus, Dermatophagoides farinae, and Tyrophagus putrescentiae

Objective:To characterize the group-29 allergens from Dermatophagoides (D.) pteronyssinus and investigate their ability to cross-react with other group-29 allergens from D. pteronyssinus as well as those from D. farinae and Tyrophagus putrescentiae.Methods:Der p 29, Der f 29, and Tyr p 29 cDNA sequences were amplified from total RNA isolated from D. pteronyssinus, D. farinae and Tyrophagus putrescentiae, respectively. Then they were cloned into the pET28a vector, expressed in Rosetta2(DE3)plysS, and purified using anion exchange chromatography. The IgE-binding rates of rDer p 29 were assessed by IgE Western blotting. The four epitopes of rDer p 29 were predicted, synthesized, and detected by IgE-ELISA. The cross-reactivity among the recombinant proteins rDer p 29, rDer f 29, and rTyr p 29 was investigated using dot blot and IgE-ELISA inhibition experiments. The allergens' physiochemical properties, amino acid sequences, and tertiary structures were also compared.Results:Der p 29 was successfully expressed in Rosetta2(DE3)plysS as a single, 393-bp open reading frame. Western blotting showed that the purified rDer p 29 protein exhibited an high IgE-binding rate when tested on patient sera. The following four Der p 29 epitopes were predicted and synthesized: 37-45 (EP1), 57-69 (EP2), 75-80 (EP3), and 104-117 (EP4). IgE-ELISA tests on 20 D. pteronyssinus- positive sera yielded IgE-binding rates of 85% (rDer p 29), 80% (EP1), 55% (EP2), 40% (EP3), and 55% (EP4), respectively. The dot blot experiments further confirmed cross-reactivity among the three group-29 proteins. When used as an inhibitor, rDer p 29 demonstrated an average cross-reactive inhibition rate of 49.7% against rDer f 29 and 54.4% against rTyr p 29. When rTyr p 29 was used as an inhibitor, it showed an average cross-reactive inhibition rate of 56.3% against rDer f 29.Conclusions:A recombinant protein, rDer p 29 with strong allergenicity was produced. Moreover, it was found that rDer p 29 cross-reacted with rDer f 29 and rTyr p 29, due to their highly homologous sequences and structures. These findings highlight the importance of considering cross-reactivity when diagnosing and treating allergic diseases.