Bet v 1, the major birch pollen allergen, conjugated to crystalline bacterial cell surface proteins, expands allergen-specific T cells of the Th1/Th0 phenotype in vitro by induction of IL-12

Modulation of allergic immune responses by using adequate adjuvants is a promising concept for future immunotherapy of type I hypersensitivity. In the present study, recombinant Bet v 1 (rBet vl, the major birch pollen allergen) was conjugated to cross-linked crystalline surface layer proteins (SL) derived from Gram-positive eubacteria, T cell lines (TCL) and clones (TCC) were established from peripheral blood of birch pollen-allergic patients, TCL and TCC were induced either using rBet vl alone or rBet v 1/SL conjugates (rBet v 1/SL) as initial antigen stimulus, Cytokine production after re-stimulation with rBet vl was investigated. TCL initiated with rBet v 1/SL showed significantly increased IFN-gamma production as compared to rBet v 1-selected TCL. TCC were established from TCL of five patients, As expected, the majority of CD4(+) TCC induced by rBet v 1 (55%) displayed a T(h)2-like pattern of cytokine production. However, only 21% of Bet v 1-specific TCC isolated from TCL established with the Bet v 1/SL revealed this phenotype. The majority of SL-specific TCC (80%) belonged to the T(h)1 phenotype, In cultures of peripheral blood mononuclear cells, both, SL and Bet v 1/SL (but not rBet v 1) stimulated the production of high levels of IL-12, a pivotal mediator of T(h)1 responses, Moreover, stimulation of rBet v 1-induced TCC with rBet v 1/SL led to an increased IFN-gamma production. This effect could be reversed by neutralizing anti-IL-12 mAb. Together these results indicate an adjuvant effect of SL mediated by IL-12. Our results indicate that bacterial components, such as SL, displaying adjuvant effects may be suitable for immunotherapeutical vaccines for type I allergy.