Abstract FR:

In our thesis work, we have used different approaches to study the human infection caused by Helicobacter pylori. The first part of our work concerns a fondamental approach by using in vitro models. We have developped a model allowing to study the transepithelial migration of neutrophils across an epithelial barrier of intestinal cells. We have demonstrated by using gastric epithelial cell line (AGS) and endothelial cells (HUVEC), that cagA had a different comportment in transformed and non transformed cell lines. In a second part of our thesis we have studied in vitro the interaction between the neutrophils and different virulent factors present in supernatants of broth culture filtrates. H. Pylori lipopolysaccharides have a strong anti-apoptotic effect in human neutrophils, maybe playing a crucial role in vivo by increasing the effect of free radical oxygen on epithelial cells. We have then worked with biopsies taken from patients infected by different strains of H. Pylori. We have performed a transcriptomic approach showing that this method was possible with small specimens (molecular biopsy concept). By using tissue microarray we have shown that mast cells presents in the gastric mucosa are numerous when the different strains isolated in parallel are cagA, VacA s1/m1 and BabA triple positive. Finally, the presence of mast cells associated with the surface epithelium are strongly correlated with an increased of epithelial cell apoptosis.