The complete eradication of cholera is an unachievable goal because it is now firmly established that there are environmental reservoirs for Vibrio cholerae. Although there are effective treatments for this disease, they are expensive and impractical in times of epidemic. All these points lead to the fact that the development of a safe, cheap, and efficient vaccine is probably the best solution to the problem. A new generation of vaccine, termed DNA vaccine, would probably be a better alternative to the traditional vaccines. In this study, the focus is on the ctxB, the gene encoding the B subunit cholera toxin as a potential candidate for the DNA vaccine against cholera. The ctxB gene is required for the binding of the Cholera Toxin (CT) to the eukaryotic cell and facilitates the entry of the active toxin (CTXA) into the host cell which causes the profuse diarrheal symptom. The ctxB gene was cloned in pVax 1 (Invitrogen), and proven to be in the correct orientation. Subsequently, expression of the B subunit toxin in vitro was successfully carried out using 10 and 20 ml of Effectene (Qiagen) reagent with 0.4 mg pVax/ctxB, 90 hours post transfection in COS-7 cells. The results showed that the pentamer size of the ctxB (58 kDa) was expressed instead of its single monomer of 11.6 kDa. This means that the mechanism of the eukaryotic expression system in vitro was able to produce this end-product by successfully processing the binding of five single peptides of the ctxB. Further investigations involving this potential DNA vaccine against cholera is currently underway, including the production of antibody in animal models.
