AIM:To detect and evaluate the antibodies against Helicobacter pylori(H pylori) neutrophil-activating protein(HP-NAP) in patients with gastric cancer and other gastroduodenal diseases.METHODS:Recombinant HP-NAP was prepared from a prokaryotic expression system in Escherichia coli.Serum positivity and level of HP-NAP-specific antibodies in sera from 43 patients with gastric cancer,28 with chronic gastritis,28 with peptic ulcer,and 89 healthy controls were measured by rHP-NAP-based ELISA.rHP-NAP-stimulated production of interleukin-8(IL-8) and growth-related oncogene(GROα) cytokines in the culture supernatant of SGC7901 gastric epithelial cells was also detected.RESULTS:The serum positivity and mean absorbance value of HP-NAP-specific antibodies in the gastric cancer group(97.7% and 1.01 ± 0.24) were signifi cantly higher than those in the chronic gastritis group(85.7% and 0.89 ± 0.14,P < 0.005) and healthy control group(27.7% and 0.65 ± 0.18,P < 0.001) .The sensitivity and specifi city of ELISA for the detection of HP-NAP-specific antibodies were 95.5% and 91.5%,respectively.HP-NAP could slightly upregulate IL-8 production in gastric epithelial cell lines but had no effect on GROα production.CONCLUSION:Infection with virulent H pylori strains secreting HP-NAP is associated with severe gastroduodenal diseases,and HP-NAP may play a role in the development of gastric carcinoma.rHP-NAPbased ELISA can be used as a new method to detect H pylori infection.The direct effect of HP-NAP on gastric epithelial cells may be limited,but HP-NAP may contribute to inflammatory response or carcinogenesis by activating neutrophils. AIM: To detect and evaluate the antibodies against Helicobacter pylori (H pylori) neutrophil-activating protein (HP-NAP) in patients with gastric cancer and other gastroduodenal diseases. METHODS: Recombinant HP-NAP was prepared from a prokaryotic expression system in Escherichia coli . Serum positivity and level of HP-NAP-specific antibodies in sera from 43 patients with gastric cancer, 28 with chronic gastritis, 28 with peptic ulcer, and 89 healthy controls were measured by rHP-NAP-based ELISA. RHP-NAP-stimulated production of interleukin-8 (IL-8) and growth-related oncogene (GROα) cytokines in the culture supernatant of SGC7901 gastric epithelial cells was also detected .RESULTS: The serum positivity and mean absorbance value of HP-NAP-specific antibodies in the gastric cancer group (97.7% and 1.01 ± 0.24) were signifi cantly higher than those in the chronic gastritis group (85.7% and 0.89 ± 0.14, P <0.005) and healthy control group (27.7% and 0.65 ± 0.18, The sensitivity and specifi c ity of ELISA for the detection of HP-NAP-specific antibodies were 95.5% and 91.5%, respectively. HP-NAP could slightly upregulate IL-8 production in gastric epithelial cell lines but had no effect on GROα production. CONCLUSION: Infection with virulent H pylori secreting HP-NAP is associated with severe gastroduodenal diseases, and HP-NAP may play a role in the development of gastric carcinoma. RHP-NAPbased ELISA can be used as a new method to detect H pylori infection. The direct effect of HP-NAP on gastric epithelial cells may be limited, but HP-NAP may contribute to inflammatory response or carcinogenesis by activating neutrophils.