Shigella Infection of Henle Intestinal Epithelial Cells: Role of the Host Cell

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Abstract
The process of Henle 407 embryonic intestinal epithelial cell infection by Shigella flexneri 2a M42-43 was studied in an in vitro model system. The role of the Henle cell was assessed. It was established that entry of S. flexneri into cells was suppressed by reagents which inhibit uptake of particles by phagocytic cells. The compounds tested included cytochalasin B, dibutyryl-cyclic adenosine monophosphate, choleragen ( Vibrio cholera enterotoxin), iodoacetate, and dinitrophenol. Cytochalasin B inhibited infection at concentrations of 1.0 μg/ml or greater. Dibutyryl-cyclic adenosine monophosphate at concentrations of 1 mM and choleragen at 0.1 μg/ml caused significant suppression of infection. Iodoacetate or dinitrophenol, at 0.1 mM concentrations, inhibited internalization of virulent shigellae, and a combination of these compounds inhibited infection at 0.01 mM concentrations. Preincubation of Henle cell monolayers with the combination of iodoacetate and dinitrophenol (0.05 mM) also inhibited infection markedly. The data suggest that infection of epithelial cells by S. flexneri in vitro is accomplished by an endocytic process induced by virulent bacteria. The process appears to be similar to uptake of particles by phagocytic cells. Ultrastructural analysis by transmission electron microscopy provided corroborative evidence of phagocytosis of shigellae by Henle cells in that intracellular bacteria were often observed within membrane-limiting vacuoles resembling phagosomes.