CELL-INVASIVE ACTIVITY OF EPITOPE-TAGGED ADENYLATE-CYCLASE OF BORDETELLA-PERTUSSIS ALLOWS IN-VITRO PRESENTATION OF A FOREIGN EPITOPE TO CD8(-CELLS() CYTOTOXIC T)

The adenylate cyclase (AC) toxin (CyaA) of Bordetella pertussis has an invasive catalytic domain (AC domain) which penetrates the cytoplasmi c membrane of a variety of eukaryotic cells and intoxicates them by un regulated synthesis of cyclic AMP. Previous work led to identification of five permissive sites in the AC domain at which heterologous pepti des are accommodated without affecting its enzymatic properties. We ha ve constructed a set of CyaA toxins tagged at these permissive sites b y insertion of a CD8(+) T-cell epitope, RPQAS-GVYMGNLTAQ, from the nuc leoprotein of lymphocytic choriomeningitis virus. Introduction of the epitope at any of the five sites did not affect the capacity of the to xin to deliver its AC domain into target cells. Moreover, the toxin wi th the inserted epitope was shown to sensitize target cells for lysis by epitope-specific CD8(+) cytotoxic T lymphocytes in vitro, showing t hat the tagged AC was processed for presentation of the lymphocytic ch oriomeningitis virus epitope in association with the major histocompat ibility complex class I molecules. This finding indicates that by virt ue of delivery of foreign epitopes into the antigen-presenting cells, purpose-designed recombinant CyaAs may be useful for induction of spec ific major histocompatibility complex class I-restricted cell-mediated immunity also-in vivo.