Fold stability during endolysosomal acidification is a key factor for allergenicity and immunogenicity of the major birch pollen allergen

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• 作者：Yoan Machado ; MSc^a ; Regina Freier ; MSc^a ; Sandra Scheiblhofer ; PhD^a ; Theresa Thalhamer ; PhD^a ; Melissa Mayr ; BSc^a ; Peter Briza ; PhD^a ; Sarina Grutsch ; PhD^b ; Linda Ahammer ; MSc^b ; Julian E. Fuchs ; PhD^c ; Hannes G. Wallnoefer ; PhD^c ; Almedina Isakovic ; MSc^a ; Vera Kohlbauer ; MSc^a ; Arthur Hinterholzer ; BSc^a ; Markus Steiner ; MSc^a ; Martin Danzer ; MSc^d ; Jutta Horejs-Hoeck ; PhD^a ; Fatima Ferreira ; PhD^a ; Klaus R. Liedl ; PhD^c ; Martin Tollinger ; PhD^b ; Peter Lackner ; PhD^a ; Christopher M. Johnson ; PhD^e ; Hans Brandstetter ; PhD^a ; Josef Thalhamer ; PhD^a ; Richard Weiss ; PhD^a ; ^{Richard.Weiss@sbg.ac.at" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Allergic sensitization ; Bet v 1 ; structural stability ; endolysosomal degradation ; antigen processing and presentation ; molecular allergology
• 刊名：Journal of Allergy and Clinical Immunology
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：137
• 期：5
• 页码：1525-1534
• 全文大小：2660 K

文摘

The search for intrinsic factors, which account for a protein's capability to act as an allergen, is ongoing. Fold stability has been identified as a molecular feature that affects processing and presentation, thereby influencing an antigen's immunologic properties.

Objective

We assessed how changes in fold stability modulate the immunogenicity and sensitization capacity of the major birch pollen allergen Bet v 1.

Methods

By exploiting an exhaustive virtual mutation screening, we generated mutants of the prototype allergen Bet v 1 with enhanced thermal and chemical stability and rigidity. Structural changes were analyzed by means of x-ray crystallography, nuclear magnetic resonance, and molecular dynamics simulations. Stability was monitored by using differential scanning calorimetry, circular dichroism, and Fourier transform infrared spectroscopy. Endolysosomal degradation was simulated in vitro by using the microsomal fraction of JAWS II cells, followed by liquid chromatography coupled to mass spectrometry. Immunologic properties were characterized in vitro by using a human T-cell line specific for the immunodominant epitope of Bet v 1 and in vivo in an adjuvant-free BALB/c mouse model.

Results

Fold stabilization of Bet v 1 was pH dependent and resulted in resistance to endosomal degradation at a pH of 5 or greater, affecting presentation of the immunodominant T-cell epitope in vitro. These properties translated in vivo into a strong allergy-promoting T_H2-type immune response. Efficient T_H2 cell activation required both an increased stability at the pH of the early endosome and efficient degradation at lower pH in the late endosomal/lysosomal compartment.

Conclusions

Our data indicate that differential pH-dependent fold stability along endosomal maturation is an essential protein-inherent determinant of allergenicity.