AIM: To testify the immunogenicity of a conservativeB-cell linear epitope of Helicobacter pylori(H pylori)flagellin A.METHODS: Different programs were used to analyze the secondary structure, molecular hydropathy, andsurface accessibility of H pylori flagellin A. Linear B-cell epitopes were estimated based on the structural and physiochemical information. Analysis of residue divergence was proposed to screen a conservative linear epitope.The 29-peptide (Pep29mer) synthesized by chemical method, including the predicted conservative B-cell epitope and a known K2d compatible T-cell epitope, wasused to immunize mice, and then H pylori-specific antibodies were detected by ELISA.RESULTS: Based on the analyses of divergent amino acid residues, structural and physiochemical characteristics, it was strongly suggested that the short fragment NDSDGR was the core of a conservative linear epitope in flagellin A. Animals immunized by Pep29mer acquired efficient immune response. In detail, serum H pylori-specific IgA and IgG1 increased significantly in immunized group, while IgG2a only had an insignificant change. H pylori-specific IgA in gastrointestinal flushing fluid also increased significantly.CONCLUSION: The conservative short fragment NDSDGR is the core of a linear B-cell epitope of fiagellin A.