cDNA Cloning and Characterization of the House Dust Mite Allergen Sui p 2

Suidasia pontifica (Sp) is a House Dust Mite (HDM) species found in tropical urban residential areas which causes sensitization of up to 75% of allergic patients. Cloning of allergens from Sp is a significant initial step in understanding the clinical significance of this HDM species. The study describes the cloning and in silico characterization of the group 2 allergen gene from Sp (Sui p 2) with significant homology to Myeloid Differentiation 2 (MD-2) lipid-binding (ML domain) protein allergens. Sui p 2 gene was amplified by Reverse Transcription – PCR using gene-specific primers designed from known HDM group 2 allergens. The amplicons were characterized using NCBI BLAST, ExPASy, MEGA7 and Chimera. Sui p 2 cDNA gene exhibits percent identity to Tyrophagus putrescentiae (65.84%), Aleuroglyphus ovatus (65.69%) and Blomia tropicalis (62.98%). Sui p 2 gene contains 405 bp open reading frame with untranslated regions on its 5’ and 3’ end. Furthermore, structure-based percent identity of Sui p 2 to the group 2 allergen of D. farinae and D. pteronyssinus is 47.62% and 46.83%, respectively. Predicted protein structure reveals a putative immunoglobulin fold consisting of preserved cysteine residues, hydrophobic core and two antiparallel β-sheets containing several TLR4, LPS and IgE binding sites. The results suggest that Sui p 2 may play an important role in HDM induced allergy and may be involved in the induction of the innate immune system. Characterization of Sui p 2 is important to evaluate properly its use for allergy component resolved diagnosis and allergen-specific immunotherapy.