EFFICIENT EXTRACELLULAR PRODUCTION OF HYBRID ESCHERICHIA-COLI HEAT-LABILE ENTEROTOXIN-B SUBUNITS IN A MARINE VIBRIO

Escherichia coil heat-labile enterotoxin B subunit (EtxB) has been pro posed as a potential protein carrier for the delivery of heterologous peptides to target cells, particularly for the oral delivery of epitop es to the mucosal immune system. In this study, two extensions to the C-terminus of EtxB were genetically engineered that correspond to a we ll-characterized neutralising epitope of glycoprotein D from herpes si mplex virus (EtxB-gD) and to the C-terminal nine amino acids from the 38 kDa subunit of HSV-encoded ribonucleotide reductase (EtxB-R2). Here we describe the extracellular secretion of the two hybrid EtxBs from a marine Vibrio harbouring a broad-host range inducible expression vec tor containing the hybrid genes. Large amounts of intact fusion protei ns (15-20 mg per liter of culture) were secreted into the medium upon induction. These hybrid proteins maintained the receptor-binding activ ity of the native toxin as well as being cross-reactive with anti-EtxB and anti-heterologous peptide monoclonal antibodies.