Objective:To explore the change in virulence of Campylobacter jejuni (CJ) mutant after galE gene knock-out.Methods: Using Hep-2 cells

adherence and invasion assays were performed in the galE mutant and the parent strain

meanwhile

serum sensitivity assay and motility test were made in them. Results:The galE mutant showed a reduction in its ability to adhere to and invade Hep-2 cells. The ability of the galE mutant and parent strain to adhere to Hep-2 cells were 1.2 % and 8.3% respectively

and adherence ability of the former only was 14.5% of that of the latter. The difference was significant ( P <0.01). The ability of the galE mutant and parent strain to invade Hep-2 cells were 0.3% and 5.6% respectively

and invasion ability of the former only was 5.4% of that of the latter. The difference was also significant ( P <0.01).Furthermore

the sensitivity of both to sera were compared by incubated parental strain and galE mutant in 10% normal serum pools at 37℃. Bacterial counts were determined at 30 and 60 min after incubation. After 30mm

60 min of incubation

the survival of parental strain and galE mutant were 77.6%

67.0% and 33.6%

8.4% respectively. The survival of the galE mutant was significantly reduced compared to that of the parental strain ( P <0.05). The mobility test showed no difference between mutants and parental strains.Conclusion:These results indicate that the galE mutants with a significant reduction in virulence may have a future role as a live attenuated vaccine candidate.