Production, purification and structural characterisation of recombinant BanLec-Bet v 1

Abstract

The sublingual route of allergens administration in allergen-specific immunotherapy (ASIT) is proven to be a successful way to treat patients with respiratory allergy. The trend of replacing natural extracts with purified recombinant allergens is growing. Although the purified allergens themselves are not good immunogens, the combined vector systems and adjuvans can improve their immunogenicity 1. Cell surfaces are decorated by different glycan structures, so the lectins specific for these glycans can be used to deliver particular therapeutic to target specific tissue 2. Banana lectin (BanLec) is mannose-specific protein which belongs to the subfamily of Jacalin related lectins 3. Apart from its characteristic to bind glycans, BanLec also modulates immune cells in vitro 4. On the other hand, Bet v 1 (Betula verrucosa) is the major birch pollen allergen. T-cell epitops are distributed over almost entire protein structure 5. In the study the recombinant BanLec-Bet v 1 construct is designed, produced by the recombinant DNA technology, purified and characterized by classical biochemical methods for the application in the ASIT of birch pollen allergy. The expression of newly designed BanLec-Bet v 1 was performed in E. coli BL21 (DE3). After expression the protein was found in the inclusion bodies from which it was extracted with 4 M urea solution. After renaturation, affinity chromatography (Sephadex G-75 superfine) was used for protein purification. Biochemical characterization of the chimera was performed by: SDS PAGE electrophoreses, CD spectroscopy and mass spectrometry. Biological activity of the construct was confirmed by binding of BanLecBet v 1 to a horseradish peroxidase glycoprotein in ELISA. Purified BanLec-Bet v 1 showed molecular mass of 32 kDa. CD spectra of the recombinant construct revealed well defined secondary structures with predominant beta sheets (41.2%). By mass spectrometry 51.8% of the BanLec-Bet v 1 primary structure was confirmed. Biologicaly active recombinant BanLec-Bet v 1 was produced by the recombinant DNA technology. Further in vitro and in vivo studies will evaluate immunomodulatory potential of BanLec-Bet v 1 for application in ASIT.