Creation of a Humanized Model for Respiratory Allergy Using a Human Mugwort-Specific T-Cell Receptor and HLA-DR1

Background: Currently, T cell receptor (TCR) transgenic (tg) mice with a murine TCR specific for chicken ovalbumin in the context of a murine restriction element  (I-A^d) are frequently used in allergy research to investigate T helper cell differentiation and allergy treatment in vivo. 

Methods: We here aimed to generate double tg mice expressing a human TCR specific for the immuno-dominant epitope of the major mugwort (Artemisia vulgaris) pollen allergen Art v 1 in the context of the human restriction element HLA-DR1 to provide a valid model for studying allergy development and treatment in vivo. To obtain high expression levels the allergen-specific human TCR variable sequences were chimerized with murine TCR constant sequences. Resulting transgenes were cloned into the pT_cass vector system and thus put under the transcriptional control of the natural TCR alpha and beta promotor/enhancer elements. Allergen-specific TCR tg founder mice were cross-bread with HLA-DR1⁺ B10.M-DR1^dlAb1-Ea mice. 

Results: Immunophenotyping of double tg TCR/HLA-DR1 mice revealed clear-cut expression of the Art v 1-specific TRBV18 chain on peripheral blood CD3⁺ T lymphocytes and HLA-DR1 expression on CD14⁺ monocytes and B220⁺ B lymphocytes. In vitro, splenocytes from TCR/HLA-DR1 double tg mice but not of HLA-DR1 single tg mice or wt mice specifically proliferated upon incubation with the human-relevant immuno-dominant Art v 1_25-36 peptide or whole Art v 1 protein. No proliferation was observed upon incubation with control peptides or proteins. Allergen-specific cellular proliferation is accompanied by the production of a balanced cytokine milieu including IFN-gamma, IL-2, IL-4, IL-6, IL-13 and IL-17 (> 50pg/ml per 2x10⁵ splenocytes). No cytokine secretion was evident upon incubation of splenocytes with a control peptide or medium alone. Importantly, double tg mice are proficient to mount both IgG2a and IgG1, IgE responses when i.p. immunized with antigen plus alum.

Conclusions:

A fully humanized allergy model, in which all components of the allergen-specific synapse are well-defined enables to analyze the relevant T-cell dependent  (and independent) pathways by which allergic diseases can be influenced in vivo and will provide important insights into the pathophysiology of allergic diseases and their possible cure in the future.