Helicobacter pylori induce neutrophil transendothelial migration: Role of the bacterial HP-NAP Mikael Brisslert a,b, * , Karin Enarsson a , Samuel Lundin a , Anna Karlsson b , Johannes G. Kusters c , Ann-Mari Svennerholm a , Steffen Backert d , Marianne Quiding-Ja ¨rbrink a a Department of Medical Microbiology and Immunology, Go ¨ teborg University, Sweden b Department of Rheumatology and Inflammation Research, The Sahlgrenska Academy, Go ¨ teborg University, Guldhedsgatan 10A, 413 45 Go ¨ teborg, Sweden c Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Rotterdam, The Netherlands d Department of Medical Microbiology, Otto von Guericke University, Magdeburg, Germany Received 12 April 2005; received in revised form 2 June 2005; accepted 2 June 2005 First published online 22 June 2005 Edited by A.H.M. van Vliet Abstract Continuous recruitment of neutrophils into the inflamed gastric mucosal tissue is a hallmark of Helicobacter pylori infection in humans. In this study, we examined the ability of H. pylori to induce transendothelial migration of neutrophils using a transwell system consisting of a cultured monolayer of human endothelial cells as barrier between two chambers. We showed for the first time that live H. pylori, but not formalin-killed bacteria, induced a significantly increased transendothelial migration of neutrophils. H. pylori con- ditioned culture medium also induced significantly increased transendothelial migration, whereas heat-inactivated culture filtrates had no effect, suggesting that the chemotactic factor was proteinaceous. Depletion of H. pylori-neutrophil activating protein (HP-NAP) from the culture filtrates resulted in significant reduction of the transmigration. Culture filtrates from isogenic HP-NAP deficient mutant bacteria also induced significantly less neutrophil migration than culture filtrates obtained from wild-type bacteria. HP-NAP did not induce endothelial cell activation, suggesting that HP-NAP acts directly on the neutrophils. In conclusion, our results demonstrate that secreted HP-NAP is one of the factors resulting in H. pylori induced neutrophil transendothelial migration. We pro- pose that HP-NAP contributes to the continuous recruitment of neutrophils to the gastric mucosa of H. pylori infected individuals. Ó 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. Keywords: HP-NAP; Helicobacter pylori; Transmigration; Endothelial cells; Inflammation 1. Introduction Infection with Helicobacter pylori gives rise to active chronic gastritis in virtually all infected subject. In some individuals, the infection eventually leads to the devel- opment of ulcer disease or gastric adenocarcinoma. Sev- eral bacterial and host factors seem to play important roles in determining the severity of the inflammation and the outcome of the infection [1,2]. Continuous recruitment of neutrophils into the inflamed gastric mucosal tissue is a hallmark in human H. pylori infections. A strong correlation exists between gastric neutrophil infiltration, mucosal damage, and develop- ment of duodenal ulcer (DU) disease in H. pylori 0378-1097/$22.00 Ó 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.femsle.2005.06.008 * Corresponding author. Tel.: +46 0 31 3424021; fax: +46 0 31 823925. E-mail address: mikael.brisslert@rheuma.gu.se (M. Brisslert). www.fems-microbiology.org FEMS Microbiology Letters 249 (2005) 95–103