Comparison of immunological properties of recombinant and natural turbot (Scophthalmus maximus) parvalbumin

Fish parvalbumin is a major allergen known to cause allergy and has been a serious concern of food safety all over the world. Recombinant allergen has been broadly applied in allergy diagnosis and immunotherapy in recent years, but different immune activities of several recombinant allergens compared with their natural forms were found. To further characterize and explain the difference between natural and recombinant allergens, in this study, the difference of structure, Ca2+ binding, IgE/IgG binding activity, degranulation ability and digestion stability between natural and recombinant turbot parvalbumins were compared. Both recombinant and natural parvalbumins bind to specific immunoglobulin E from fish allergic patients and rabbit IgG antibody, whereas recombinant parvalbumin showed lower IgG binding activity in inhibition assays. Moreover, recombinant parvalbumin showed comparable ability with natural parvalbumin in Ku812 cells degranulation assay. Besides, intestinal digestion stability of recombinant parvalbumin was similar with natural form while gastric digestion stability was reduced. In addition, similar secondary structure change as well as different tertiary structure change between recombinant and natural parvalbumins due to heating, Ca2+ depletion and heating after Ca2+ depletion was characterized by spectra analysis. Different Ca2+ binding of two forms of parvalbumins was also found according to their different structural changes after Ca2+ depletion. These results revealed that recombinant turbot parvalbumin preserved fundamental immunological properties of its natural form while improper folding of tertiary led to its different Ca2+ binding, lower IgG binding activity and digestion stability.