Evaluation of a potential correlation between invasiveness of intestinal cells cultivated in vitro, intimin subtypes, and expression of effector protein EspT in atypical Enteropathogenic Escherichia coli

Abstract

Enteropathogenic Escherichia coli (EPEC) are composed of two subgroups: typical EPEC (tEPEC) and atypical EPEC (aEPEC), and this classification is based on the occurrence of the EAF plasmid (EPEC adherence factor) in tEPEC and its absence in aEPEC. For several decades, tEPEC were the main agents of childhood diarrhea in Brazil, but their frequency has decreased while aEPEC have been found in different regions in a wide age range. tEPEC and aEPEC share the ability to produce attaching-effacing lesion (A/E) in eukaryotic cells. This lesion depends on the expression of various genes within the locus of enterocyte effacement, which encodes the formation of a type 3 secretion system (T3SS), an outer membrane adhesive protein (intimin) and its translocated receptor Tir, and several effector proteins. Some chromosomal genes located outside the LEE region encode protein effectors (non-LEE effectors), which use the T3SS to achieve different targets within host cells. One of these effectors, EspT activates the mammalian GTPases Rac1 and Cdc42, resulting in the formation of membrane ruffles and lamelipódios in non-intestinal cells cultured in vitro, leading to an invasion of the target cell. Recently, we found that some aEPEC strains carrying newly described intimin subtypes invade HeLa cells and T84 intestinal cells in varying frequencies, which are significantly higher than that of a prototype tEPEC strain. We further note that, in one of these strains, the process of invasion was dependent on the interaction of intimin subtype omicron and its receptor, Tir. This study aimed to evaluate and compare the efficiency of the ability to invade intestinal cells cultivated in vitro by aEPEC strains carriers of intimin subtypes most commonly found in the pathotype and monitor the participation of the effector EspT in the process of invasion of selected strains.