http://www.abbs.info E-mail: [email protected]

ISSN 1672-9145 Acta Biochim Biophys Sin 2005, 37(2): 126–132 CN 31-1940/Q

---

LT(K63/R72), a New Mutant of Escherichia coli Heat-labile Enterotoxin, Exhibits Characteristics More Similar to LT(K63) than LT(R72)

Qiang FENG^1,2, Jun YANG¹, Ping LUO¹, Wei-Jun ZHANG¹, and Quan-Ming ZOU¹*

¹Department of Clinical Microbiology and Immunology, Third Military Medical University, Chongqing 400038, China;

²Department of Life Sciences and Chemistry, Chongqing Education College, Chongqing 400067, China

Abstract LT(K63), a non-toxic mutant and LT(R72), a low toxic mutant of E. coli heat-labile enterotoxin are frequently used mucosal adjuvants. In many cases, the adjuvanticity of LT(K63) is lower than that of LT(R72), but LT(K63), which induces a mixed Th1/Th2 response, exhibits a higher level of protection than LT(R72) which induces a polarized Th2-type response. To utilize the advantages of both adjuvants, a double-mutation LT(K63/R72) was generated and purified. The characterization results showed that there was no significant difference in production rate and immunogenicity between wild type LT and LT mutants. The results also showed that the toxicity and the trypsin sensitivity of LT(K63/R72) are between that of LT(K63) and LT(R72). Using HPLC, when samples in an OHpak SB-800 column were eluted by denatural buffer (TEAN containing 10 mg/ml SDS), we found the stability of LT(K63/R72) was higher than that of LT(R72) and lower than that of LT(K63). Through further analyzes, we found that LT(K63/R72) exhibits characteristics more closely related to LT(K63) than LT(R72).

Key words Escherichia coli heat-labile enterotoxin; mutants; LT(K63); LT(R72); LT(K63/R72)

-----------------

Received: November 1, 2004 Accepted: December 30, 2004

This work was supported by a grant from the National High Technology Research and Development Program of China (No. 2001AA215161)

*Corresponding author: Tel/Fax, 86-23-68752316; E-mail, [email protected]