Patent ID: 8088394

Claim:
An isolated nucleic acid comprising a first nucleotide sequence encoding a mutated E. coli heat-labile enterotoxin subunit A and a second nucleotide sequence encoding E. coli heat-labile enterotoxin subunit B, the mutated subunit A having K at the position corresponding to position 61 of SEQ ID NO:5, wherein an E. coli containing the nucleic acid expresses detoxified E. coli heat-labile enterotoxin proteins in the AB 5 format and the B 5 format, the AB 5 /AB 5 +B 5 ratio being 1.3 fold greater than the AB 5 /AB 5 +B 5 ratio of detoxified E. coli heat-labile enterotoxin proteins expressed in an E. coli containing a nucleic acid encoding E. coli heat-labile enterotoxin subunit B and a mutated E. coli heat-labile enterotoxin subunit A having F at the position corresponding to position 61 of SEQ ID NO:5.