Development of an vaccine commonly effective against different serotypes in fish pathogenic bacterium Edwardsiella tarda

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As there are many serotypes in fish pathogenic bacterium Edwardsiella tarda it has been considered difficult to produce effective vaccine against this disease. Present research project is intended to develop an.vaccine based on a commonly protective antigen among the different serotypes of E.tarda and obtained following results.A 37kDa outer membrane protein(OMP) was found as a common antigen among different serotypes of E.tarda. This protein was detected as separated one band by general SDS-PAGE and Western blotting. Two-dimensional electrophoresis and Western blotting showed the 37kDa OMP was detected as separate several dots with different PIs. However, these proteins showed similar antigenicity and same amino acid sequences, which indicate small difference in the molecular structure due to phosphonium or glycosyl modifications. N-terminal amino acid sequence of the protein and complete nucleotide sequence of the gene demonstrated that the 37kDa OMP is a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) found in a variety of bacteria. The recombinant GAPDH (rGAPDH) of E. tarda over expressed by using a Escherichia coli expression system was immunized to Japanese flounder and evaluated its vaccine efficacy. The results showed that the immunization with rGAPDH effectively protected Japanese flounder against infection with the different serotypic strains of E.tarda. The immune serum of these fish demonstrated increase in the antibody titer against those strains. The results show that the use of the rGAPDH will enable to develop a commonly effective vaccine against any serotypes of E.tarda.