MONOMERIC ALLERGOID FROM HOUSE DUST MITE DERMATOPHAGOIDES PTERONYSSINUS: IMMUNOLOGICAL PROPERTIES
Background. The purpose of this study was to characterize the immunologic properties of the monomeric allergoid obtained from house dust mite Dermatophagoides pteronyssinus (D. pteronyssinus) extract. Methods. To obtain monomeric allergoid the extract from D. pteronyssinus (D1) was chemically modified by succinilation and then the degree of modification and total protein content were determined. Analysis of proteins in native D1 or modified sD1 was performed by SDS-PAGE. Determination of the major allergen Der p 1 in the native extract D1 was done by mass-spectrometry method. For measurement of tertiary structure alterations of protein molecules in D1 or recombinant Der p 1 (rDer p 1) after their modification by succinilation the circular dichroism (CD) method was applied. Allergenicity of sD1 was estimated by inhibition of specific IgE binding in ELISA and chemiluminescent analysis using Phadia ImmunoCAP as well as by detection of histamine released from leukocytes of whole blood of Der p sensitized patients after its incubation with D1 or sD1. To evaluate immunogenicity of D1 and sD1 BALB/c mice were i.p. immunized 4 times in 3 week interval with D1 or sD1 with or without adjuvant Al(OH),. The levels of anti-Der p IgE, IgG1 and IgG2a in pulled mice sera were determined by ELISA. Results. Succinilation of D1 extract led to «unfolding» of allergen molecules in modified sD1. The degree ofmodification was 98,9%. Results of SDS-PAGE demonstrated that native D1 and succinilated sD1 extract showed bands at the same molecular mass confirming that succinilation does not influence the size of modified molecule which thus maintains the monomeric nature of the sD1. Mass-spectrometry analysis revealed the presence of major allergen Der p 1 in the native D1 extract. CD method demonstrated the alteration of tertiary structure of succinilated recombinant rDer p 1 that may be extrapolated on the other allergenic proteins in the sD1 extract. Allergenicity of sD1 was significantly reduced in compare to D1 that was confirmed by inhibition of IgE-binding and histamine release from leukocytes of whole blood, Immunization of BALB/c mice with sD1 (with or without Al(OH)<sub>3</sub>) induced anti-Der p IgE-response which was substantially lower than that of D1 induced. At the same time anti-Der p IgG1 and IgG2a responses after immunization with sD1 (with or without Al(OH)<sub>3</sub>) were significantly higher than that ofD1 induced. Conclusion. Modification of the extract from house dust mite D. pteronyssinus by succinilation leads to formation of monomeric allergoid possesses low allergenicity and preserved (or even increased) immunogenicity that may a new approach for creation of allergy vaccines for safe and effective allergen-specific immunotherapy.