Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 5 2 2013 06 15 142 146 EN Davoud Esmaeilli Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran AND Department of Bacteriology, Faculty of Medical Sciences, Baqiyatallah University of Medical Sciences, Tehran, Iran. Ashraf Mohabati-Mobarez Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Ali Hatef-Salmanian National Institutes for Genetic Engineering and Biotechnology, Tehran, Iran. Ahmad Zavaran-Hosseini Dept. of Immunology, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran. 2015 10 16 Background and Objectives: Helicobacter pylori is the causative agent of peptic ulcer disease and a co-factor in development of gastric malignancies. LPS are among toxic substances produced by H. pylori exhibiting low endotoxic activity compared to typical bacterial LPS. The aim of this study was to investigate bioactivity of LPS produced by different serotypes of Helicobacter pylori compared to Escherichia coli and Brucella abortus LPS. Materials and Methods: Bacterial LPS was extracted by the hot phenol-water method. Biological activities of LPS were determined via the limulus lysate assay, pyrogenic assay, and blood pressure and PBMC induction test in rabbits. Results: Biological activity of O serotype LPS of H. pylori was less than the biological activity of other H. pylori serotypes. Conclusion: Our data supported the hypothesis that the unique bacterial LPS of the O formulation of a multivalent H. pylori vaccine. https://ijm.tums.ac.ir/index.php/ijm/article/view/616 https://ijm.tums.ac.ir/index.php/ijm/article/download/616/389