Enteropathogenic Escherichia coli (EPEC) are subdivided into typical EPEC (tEPEC) and atypical EPEC (aEPEC) according to the presence of the EAF (EPEC adherence factor) plasmid in tEPEC and its absence in aEPEC. Although tEPECs have been the major agent of infantile diarrhea in Brazil, their frequency is decreasing while the aEPECs have been identified as agents of diarrhea in various geographic regions and different age groups. tEPEC and aEPEC share the ability to produce attaching-effacing (A/E) lesions in enterocytes that depends on the expression of several genes contained in the locus of enterocyte effacement (LEE). This locus encodes the formation of a type three secretion system (T3SS), an outer membrane adhesive protein (Intimin) and its translocated receptor Tir, and several effector proteins. However, tEPEC and aEPEC differ in several aspects and new potential virulence mechanisms have been found among aEPEC strains. Recently, we found that aEPEC strains, carriers of different intimin subtypes, invaded HeLa cells and T84 intestinal cells at frequencies significantly higher than that of a of tEPEC prototype strain. Regarding tEPEC, although this pathotype shows very limited ability to invade eukaryotic cells in vitro, it has been demonstrated that intimate adherence of tEPEC strains depends on lipid rafts. There are no information in the literature about the interaction of aEPEC strains and cholesterol-rich domains in membranes of intestinal cells and whether this interaction could target bacterial internalization. In this project, we intend to study the early stages of invasion of a selected aEPEC strain (1551-2), particularly in relation to bacterial interaction with cholesterol-rich structures in the host cell membrane.
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