Attachment of Giardia lamblia to rat intestinal epithelial cells.

Abstract

SUMMARY The human enteric protozoan, Giardia lamblia, has surface membrane lectin activity which mediates parasite adherence to erythrocytes. To determine whether an intestinal binding site exists for this lectin we have studied the interaction in vitro between axenically cultured Giardia trophozoites and isolated rat intestinal epithelial cells. Scanning electron microscopy showed that Giardia attached to the apical microvillus membrane and basolateral membrane of rat enterocytes. Any location on the parasite surface could mediate attachment without predeliction for the ventral disc. Trophozoites attached more avidly to jejunal compared with colonic epithelial cells. Attachment was inhibited at 4°C, by sugars and glycoproteins containing D-mannosyl residues and by subagglutinating concentrations of anti-Giardia rabbit serum and two monoclonal antibodies, all with reactivity to parasite surface membrane determinants. Trypsinisation of trophozoites also reduced attachment but the ability to attach was rapidly restored after returning trophozoites to TYI-S culture medium for 4 h at 37°C. Attachment was unaltered by the presence of the microfilament inhibitor cytochalasin B and in the absence of Ca++ and Mg++ ions. These findings support previous work that Giardia possesses a surface membrane mannose binding lectin and indicate that appropriate binding sites are present on rat intestinal epithelial cells. This lectin may play a part in mediating adherence of Giardia to mammalian intestine and could be a target for host immune defence.Adherence of microbial enteropathogens to host intestinal epithelium is considered to be a critical step in the pathogenesis of many intestinal infections.' Giardia is commonly found in close proximity to the small intestinal mucosa and when in the ventral surface down position, it is generally considered that the parasite attaches to intestinal epithelial cells by either a suction force generated beneath the ventral disc by the propulsive efforts of the ventral flagella (hydrodynamic theory),' by mechanical processes related to contractile protein elements of the ventral disc and ventrolateral flange," or by a combination of the two mechanisms.Giardia may be found in other orientations with respect to the gut mucosa such as the dorsal surface down position' as seen in one of our patients (Fig. 1). This suggests that parasite surface membrane determinants may also be involved in the attachment process. We have shown previously using mammalian erythrocytes as a model target for attachment, that Giardia lamblia, like some bacteria and other protozoa, has lectin activity associated with its surface membrane with specificities for D-glucosyl and D-mannosyl residues.7 To discover the possible relevance of this attachment mechanism in the pathogenesis of giardiasis, we have now investigated the interaction between Giardia and isolated mammalian intestinal epithelial cells to determine whether an intestinal receptor exists for this putative lectin in gut epithelium.

Inhibition of Giardia intestinalis by Extracellular Factors from Lactobacilli: an In Vitro Study

“…" Preliminary experiments showed that the preincubation of Caco-2 cells with suspensions of L. johnsonii La1 did not inhibit the complex adhesion of trophozoites to cell monolayers (data not shown). This interaction involves the ventral disk, several contractile elements, and hydrodynamic and mechanical forces, as well as lectin-binding factors (18,21,24,25). The possibility remained that if an antagonistic effect of the bacteria against the parasite existed, it could result from the release of bacterial metabolites or products more than a competitive exclusion or steric hindrance (3).…”

Effect of Chronic Ethanol Administration on Intestinal Microvillus Membrane Glycosylation in Rats Fed Rat Pellet Diet and Protein-Rich Diet.

“…Increasing evidence suggests that viruses [2], bacteria, bacterial toxins [3], and protozoa [4] specifically recognize and bind to cell-surface carbohydrates and that this interaction is necessary to cause an infection or produce a toxic effect. Thus, it is likely that alterations in glycosylation of the microvillus surface may influence the expression of receptors for regulation of cell growth, differentiation, and for colonization of enteric pathogens in the small intestine.…”

Immune Response to Giardia duodenalis

“…Using their flagella and ventral disc, trophozoites released in the upper part of the small intestine move to the microvillus-covered surface of the duodenum and jejunum, where they attach themselves (88,116), and play a role in the onset of the pathology (22,34,124). The suction force created by this mode of attachment may damage the microvilli and interfere with the process of food absorption (88,116). Eventually, the rapid multiplication of the trophozoites by binary fission creates a physical barrier between the intestinal epithelial cells and the lumen of the intestine, interfering with the process of absorption of nutrients.…”