Molecular organization of heat-labile enterotoxin genes originating in Escherichia coli of human origin and construction of heat-labile toxoid-producing strains.

Recombinant deoxyribonucleic acid technology was employed to construct heat-labile enterotoxin (LT) toxoids. A recombinant plasmid carrying both an LT promoter region and LT subunit A (LTA) gene, lacking as much as 0.25 kilobases of the region up to the C terminus, produced a peptide possessing immunological properties of LTA but lacking the ability to construct LT activity (designated as LTA*). A cloned LT subunit B (LTB) gene produced LTB when a promoter on a vector was available for the gene. Escherichia coli producing LTA* and LTB (LT toxoids) could be useful as a vaccine.