Bacterial ghosts as drug carrier and targeting vehicles

A novel system for the packaging of drugs as well as vaccines is presented. Bacterial ghosts are intact, non-denatured bacterial envelopes that are cr eated by lysis of bacteria through the: expression of cloned phage PhiX174 gene E. Inhibition of induced E-mediated lysis by MgSO4, harvesting of cell s by centrifugation, and resuspension in low-ionic-strength buffers leads t o rapid, violent lysis and results in empty bacterial envelopes with large (approximately 1 mu m in diameter) openings. The construction of plasmid pA V1, which encodes a streptavidin fusion protein with an N-terminal membrane anchor sequence, allows the loading of the inner side of the cytoplasmic m embrane with streptavidin. The functionality and efficacy of binding of eve n large biotinylated compounds in such streptavidin ghosts (SA-ghosts) was assessed using the enzyme alkaline phosphatase. The successful binding of b iotinylated fluorescent dextran, as well as fluorescent DNA complexed with biotinylated polylysine, was demonstrated microscopically. The display by b acterial ghosts of morphological and antigenic surface structures of their living counterparts permits their attachment to target tissues such as the mucosal surfaces of the gastrointestinal and respiratory tract, and their u ptake by phagocytes and M cells. In consequence, SA-ghosts are proposed as drug carriers for site-specific drug delivery. (C) 1999 Elsevier Science B. V. All rights reserved.