Abstract
It has been known for many years that Trichinella spiralis initiates infection by penetrating the columnar epithelium of the small intestine; however, the mechanisms used by the parasite in the establishment of its intramulticellular niche in the intestine are unknown. Although the previous observations indicated that invasion also occurs in vitro when the infective larvae are inoculated onto cultures of intestinal epithelial cells (e.g., human colonic carcinoma cell line Caco-2, HCT-8), a normal readily manipulated in vitro model has not been established because of difficulties in the culture of primary intestinal epithelial cells (IECs). In this study, we described a normal intestinal epithelial model in which T. spiralis infective larvae were shown to invade the monolayers of normal mouse IECs in vitro. The IECs derived from intestinal crypts of fetal mouse small intestine had the ability to proliferate continuously and express specific cytokeratins as well as intestinal functional cell markers. Furthermore, they were susceptible to invasion by T. spiralis. When inoculated onto the IEC monolayer, infective larvae penetrated cells and migrated through them, leaving trails of damaged cells heavily loaded with T. spiralis larval excretory-secretory (ES) antigens which were recognized by rabbit immune sera on immunofluorescence test. The normal intestinal epithelial model of invasion mimicking the natural environment in vivo will help us to further investigate the process as well as the mechanisms by which T. spiralis establishes its intestinal niche.
Highlights
Trichinella spiralis is a parasitic nematode that infects their vertebrate host after consumption of meat containing infective larvae
It is well known that the invasion of host intestinal epithelium by the infective larvae is the first step during T. spiralis infections
Previous attempts have showed that when T. spiralis infective larvae are suspended in semisolid medium and inoculated onto monolayers of tumor epithelial cells grown in vitro, they invade cells, penetrate adjacent cells, and reside in the cytoplasm of the syncytia that they create [7,8,9]
Summary
Trichinella spiralis is a parasitic nematode that infects their vertebrate host after consumption of meat containing infective larvae. Until now the mechanisms by which T. spiralis infective larvae recognize, invade, migrate within the intestinal epithelium and establish its intramulticellular niche have not ever been elucidated. The reason why those studies have been hindered lies in the lack of a manipulated in vitro model. Previous investigations, using the IEC line derived from rat intestinal crypt epithelium (IEC-6) as an invasion model, have demonstrated that T. spiralis infective larvae did not invade IEC-6 cells [10]. Up till a normal intestinal epithelial model which can reproduce the invasion of small intestinal epithelium by T. spiralis in vitro has not been reported
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