Immunogenicity of cholera toxin B epitope inserted in Salmonella flagellin expressed on bacteria and administered as DNA vaccine.

Salmonella vaccine strains have been previously reported to evoke immune response against heterologous antigen cloned in the flagellin gene. A non-toxic cholera toxin subunit B epitope was selected by using computer-based program and genetically fused in single and double copy in Salmonella typhimurium flagellin gene. The chimeric flagellin functioned normally as demonstrated by motility assay. Cholera toxin B epitope cloned in flagellin was expressed at the flagellar surface. The expression was verified by Western blotting. Mice administered orally and subcutaneously with aroA flagellin-negative strain of S. dublin expressing the chimeric flagellin gene resulted in generation of antibody against cholera toxin. Mice administered intramuscularly and subcutaneously with naked mammalian expression vector containing the same cholera toxin epitope could also evoke the antibody response though it was less than the chimeric flagellin. (Mol Cell Biochem 276: 1-6, 2005).