Natural self-assembly of allergen-S-layer fusion proteins is no prerequisite for reduced allergenicity and T cell stimulatory capacity.
BACKGROUND
Recombinant allergen-S-layer fusion proteins display a strongly reduced IgE-binding activity and promote the induction of allergen-specific Th0/1 cells and regulatory T cells. Such fusion proteins show a natural capacity to self-assemble into mono- or double-layer sheets reaching particle-like dimensions of 0.5-2 microm. We were interested in finding out whether self-assembly was crucial for the immunological characteristics of allergen-S-layer fusion proteins.


METHODS
The IgE-binding and mediator-releasing capacities of nonassembled and self-assembled rSbpA-Bet v 1, consisting of the major birch pollen allergen Bet v 1 and the S-layer protein SbpA, were compared in inhibition ELISA and basophil activation assays using sera from patients allergic to birch pollen. T cell stimulation was evaluated using Bet v 1-specific T cell clones reactive to distinct epitopes of Bet v 1. Autologous B lymphocytes, monocytes and monocyte-derived dendritic cells were employed to evaluate potential differences in uptake and processing by different antigen-presenting cells.


RESULTS
Both rSbpA-Bet v 1 variants showed significantly less IgE-binding and mediator-releasing activity than Bet v 1. However, self-assembly further minimized the reduced allergenicity of nonassembled rSbpA-Bet v 1. Both rSbpA-Bet v 1 variants induced comparable proliferation in Bet v 1-specific T cell clones. B cells inappropriately presented either variant of rSbpA-Bet v 1. Self-assembly amplified the T cell stimulatory capacity of monocytes and dendritic cells.


CONCLUSIONS
The promising characteristics of allergen-S-layer fusion proteins regarding their potential use for allergy treatment do not depend on the formation of particle-like structures.
Gerstmayr
Marianne
M
Department of Pathophysiology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, Vienna, Austria.
Ilk
Nicola
N
Jahn-Schmid
Beatrice
B
Sleytr
Uwe B
UB
Bohle
Barbara
B
D000485:Allergens / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D052179:Antigens, Plant / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology*; D029662:Betula / Q000276:immunology; D002460:Cell Line; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology* / Q000378:metabolism; D007073:Immunoglobulin E / Q000097:blood; D008213:Lymphocyte Activation; D009004:Monosaccharide Transport Proteins / Q000276:immunology*; D011058:Pollen / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism
D000485:Allergens; D052179:Antigens, Plant; D001426:Bacterial Proteins; D009004:Monosaccharide Transport Proteins; D011993:Recombinant Fusion Proteins; C120455:SbpA protein, bacteria; D007073:Immunoglobulin E