Phage-displayed Bet mim 1, a mimotope of the major birch pollen allergen Bet v 1, induces B cell responses to the natural antigen using bystander T cell help

BACKGROUND AND OBJECTIVE: In previous studies we have generated mimotopes of Bet v 1, the major birch pollen allergen, by biopannings of phage-display random peptide libraries. In the present study, we analysed the humoral and cellular immune response to Bet v 1-mimotopes. METHODS: The mimotope CFPYCYPSESA, designated Bet mim 1, was used for intraperitoneal immunizations of BALB/c mice in phage-displayed form. For examination of the humoral immune response, enzyme-linked immunosorbent assay (ELISA) experiments were applied. Stimulation capacities were investigated in cultured mouse splenocytes and in humoral Bet v 1-specific T cell clones. RESULTS: We demonstrated that the Bet mim 1-induced murine antibody response against Bet v 1 was predominated by the IgG1 isotype. In these mice only the phage-displayed mimotopes, but neither the allergen nor the synthetic Bet mim 1-mimotopes were able to stimulate proliferation of cultured splenocytes. Using Bet v 1-specific T cell clones of allergic patients, phage-displayed and synthetic mimotopes were unable to stimulate T cell proliferation. Moreover, tolerance induction to Bet v 1 in mice by intranasal administration of Bet mim 1-phages or Bet mim 1-peptide failed. CONCLUSION: Taking these results together, our data indicate that Bet mim 1 mimics a Bet v 1-epitope on the B cell but not on the T cell level. We suggest that the phage itself is responsible for the recruitment of T cells providing bystander help in the formation of a mimotope-specific humoral response.