Immunoreactivity of allergen (Bet v 1) conjugated to crystalline bacterial cell surface layers (S-layers)

Background: Crystalline cell surface layers (S-layers) from Gram-positive eubacteria had been demonstrated as carrier/adjuvants for chemically synthesized tumor-associated oligosaccharide haptens and capsular polysaccharide antigens of Streptococcus pneumoniae strains. Objectives: The applicability of S-layers as vaccine carrier for treatment of Type I allergy was investigated. Study design: Native or cross-linked S-layer self-assembly products and cell wall preparations from Bacillus sphaericus CCM 2177 and Thermoanaerobacter thermohydrosulfuricus L111-69 and L110-69 were used for immobilization of recombinant major birch pollen allergen Bet v 1. Results and conclusions: Depending on the carrier used, amounts of approximately 20-40 mu g allergen per mg conjugate could be immobilized. By application of L-glutamic acid dimethyl ester as a spacer, this value could be increased approximately 10-fold. The functionality of the rBet v 1-conjugates was assessed in immunological systems. (i) The presence of intact B-cell epitopes was demonstrated in inhibition experiments using human Bet v 1-specific IgE. (ii) The rBet v 1-S-layer conjugates were immunogenic in mice. (iii) The proliferation of rBet v I-specific T-cell clones suggested that the peptides created by processing of immobilized Bet v 1 were similar to those derived from natural allergen. (iv) Stimulation of human allergen-specific T(H)2 lymphocytes with S-layer-conjugated Bet v 1 led to a modulation of the cytokine production pattern from T(H)2 to T(H)0/T(H)1. This study indicates that S-layers may be suitable carriers for new immunotherapeutical vaccines for Type 1 hypersensitivity.