LARGE-SCALE PRODUCTION OF VIBRIO-CHOLERAE TOXIN-B SUBUNIT FOR USE IN ORAL VACCINES

By systematically manipulating promoter and ribosome binding structures, plasmid copy number and the structure of the cholera toxin B (CTB) subunit gene, we were able to develop a plasmid expression system that, when used in conjunction with an optimized growth medium, provided yields of CTB approaching one gram per liter. The CTB protein which was secreted to > 95%, could readily be purified from the growth medium of a V cholerae production strain 'and was shown to be immunologically indistinguishable from previously used vaccine preparations of native or recombinant CTB.