Monday, 8 December 2014: 14:30 - 14:50
Exhibition Hall-Poster Area (Sul America)
Franziska Roth-Walter, PhD
,
Comparative Medicine, Messerli Research Institute, University of Veterinary Medicine Vienna, Vienna, Austria
Cristina Gomez-Casado, PhD
,
Biotechnology Department, Center for Plant Biotechnology and Genomics,, Technical University of Madrid, Madrid, Spain
Luis F Pacios, PhD, Prof.
,
Departamento De Sistemas y Recursos Naturales E.T.S.I. Montes, Universidad Politecnica De Madrid, Madrid, Spain
Nadine Mothes-Luksch, MD
,
Allergycare, Vienna, Austria
Georg a Roth, MD
,
Department of Anesthesiology, General Intensive Care and Pain Medicine, Medical University of Vienna, Vienna, Austria
Josef Singer, MD PhD
,
Comparative Immunology and Oncology, Department of Pathophysiology and Allergy Research, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
Jelena Gotovina, MSc
,
Comparative Medicine, Messerli Research Institute, University of Veterinary Medicine Vienna, Vienna, Austria
Araceli Diaz-Perales, PhD, Prof.
,
Biotechnology Department, Center for Plant Biotechnology and Genomics,, Technical University of Madrid, Madrid, Spain
Erika Jensen-Jarolim, MD, Prof.
,
Comparative Medicine, Messerli Research Institute, Vienna, Austria
Background: It is hypothesized that allergens are at the borderline of self and non-self and, through as yet elusive circumstances, mount a Th2-response for allergic sensitization. Interestingly, the majority of animal-derived respiratory allergens belong to the lipocalin family. On the other hand, also our human body harbors a great number of lipocalin proteins, with the human lipocalin-2, LCN2, having immune-regulatory function. LCN2 is highly expressed in the lung and that its immune-regulatory properties depend whether it carries iron via siderophores or not. In this respect, we investigated the major allergen Bet v 1, which is considered the prototype for the PR-10 protein family, for its structural and biological resemblance with LCN2.
Methods: Structural analysis of Bet v 1 was performed using FATCATflex, Combinatorial extention algorithm and Template Modeling. Docking calculations of ligands were performed with AutoDock Vina. Iron-staining was performed on dotted apo- and holo-Betv1 as well as controls. PBMCs of 10 human subjects were activated and stimulated for 18h with apo- or holo-Bet v1 or controls. Subsequently, cells and supernatants were analysed by flow cytometry and their cytokine-content.
Results: We give structural evidence that Bet v 1 is a lipocalin-like protein with a striking resemblance to human lipocalin 2 in silico. We demonstrate that similar to lipocalin 2, Bet v 1 is capable of binding iron via catechol-based siderophores. Thereby, calculated Kd-values of 20nM outpassed affinities to known ligands more than twentyfold. Moreover, we give functional evidence of the immune-modulatory capacity of Bet v 1 being dependent on its iron-loaded state. When incubated to human immune cells, only the apo-form of Bet v 1, but not the holo-form, was able to promote Th2 cells secreting IL13.
Conclusions: Bet v 1 is a lipocalin-like protein, which is capable of binding iron via siderophores. Moreover, we give for the first time evidence that the form of application (apo- or holo-) is decisive for the subsequent immune response. The apo-form promotes Th2 cells, whereas the holo-form appears immunosuppressive. These results provide for the first time a functional understanding on the allergenicity of Bet v 1 and a basis for future allergen immunotherapies counteracting Th2 immune responses on a molecular basis.
