3. Results
3.1. Detection Limit and Specificity of the Immunochromatographic
Test Strip. To develop the high sensitive immunochromatographic
test (IC), polyclonal antibodies were developed
by using purified recombinant whole CT protein as an
antigen. And, to increase the specificity, CT-specific IgG was
isolated fromantiserumby using purified recombinant whole
CT conjugated column, and the obtainedCT-specific IgG was
used for construction of IC.We examined the lower detection
limit of established CT-IC with 10-fold serial dilutions of
purified CT (Figure 1(a)), and it was reveled that the CT-IC
can detect as low as 10 ng/mL of purified CT within 15 min.
Heat-labile toxin (LT) produced in enterotoxigenic E. coli
(ETEC) was used for specificity verification because it shares
around 80% amino acid homology with CT; therefore, it is
known that LT is antigenically similar to CT. Examination
with serial dilution of purified LT revealed that detection
limit for LT was about 100 times higher than that for CT
(Figure 1(b)), indicating that established test strip has high
specificity.
3.2. Detection of CT from V. cholerae Culture. The optimal
condition for CT production had been persistently investigated
because the amount of CT produced in V. cholerae