A bioinformatics assay on Catalase epitopes of Helicobacter pylori

Niloufar Rashidi , Hajieh Gh. Safaei Department of medical laboratory sciences, Faculty of paraMedicine, Ahvaz jundishapour University of Medical Sciences, Ahvaz, Iran Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran * Presenter & Corresponding author Abstract: Introduction: T cell responses are stimulated by the presence of short peptides bound on the surface of antigen presenting cells. These epitopes are derived from antigens of the pathogen by a series of steps that include the proteolytic processing of antigenic proteins by the antigen presenting cells and binding of the resulting peptides to major histocompatibility complex (MHC) molecules. Protective immune responses may be generated based on a single immunodominant epitope or more epitopes. Immunoinformatics tools permit us to decide on epitopes or sub-sequences of proteins that interface with the T cells of the host and predict the MHC binder. Such tools let the scanning of genome-derived protein sequences for T cell epitopes, the 8-10 mer peptides that bind to MHC and interact with the Tcell receptor, stimulating Tcell response. These epitope prediction tools are proved to be very useful, since they significantly reduce the time and effort implicated in screening probable epitopes, mainly for pathogens which there is no vaccines available now. Prediction of catalase epitopes insilico would be a valuable tool for developing useful immuoprophylatic strategy against H. pylori infection. In addition, it could be helpful for the analysis of other H.pylori antigens and other pathogens and provide a successful progress for the design of epitope-based vaccines against many pathogens. Methods: Specific sequences for H.pylori (26695) catalase in comparison with human catalase using blast identified. We selected epitopes located in regions which have shown a very low degree of sequence similarity with the human enzyme. These regions can be introduced as specific regions for H. pylori protein. Sequence of Helicobacter pylori 26695 catalase has 98% to 100% similarity with catalase of other strains of H.pylori using blast. We used Propred software for prediction promiscuous T-cell epitopes (www.imtech.res.in/raghava). The propred web interface allows users to predict MHC class ІІ binding regions in antigen sequence. Fiftyone MHC class ІІ epitope-mapping matrices were developed at Propred. Results: According to blast with human catalase, our result showed the entirely specific regions and specific regions. In this study we selected seven epitopes from entirely specific and specific regions. The epitopes were chosen from these regions: the first epitope from 1-10, the second epitope from 32-44, the third epitope from 267288, the fourth epitope from 210-233, the fifth epitope from 210-233, the sixth epitope from 420-438 and the seventh epitope from 420-438 regions of H.pylori catalase.