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The effect of Giardia duodenalis filtrates on disaccharidases of the Caco-2 cell line

University of British Columbia

Although Giardia duodenalis is one of the most common intestinal protozoan parasites world-wide, the pathogenesis of giardiasis is not understood. An attempt to correlate parasite excretory-secretory products with changes in the intestinal mucosa using an in vitro cell model was carried out to better understand this aspect of the pathogenesis. Maltase activity and protein concentration obtained from a confluent monolayer of Caco-2 cells after co-incubation with parasite filtrates were examined and compared. Appropriate controls were also assayed. Using this Caco-2 in vitro model, a significant reduction in both maltase activity and protein concentration (P<0.05) of Caco-2 cells was observed following co-incubation with the WB Giardia isolate filtrate. This effect was observed in three experiments carried out in triplicate. Reduction in maltase activity and protein concentration was as a result of co-incubating Caco-2 cells with WB parasite filtrate (absence of trophozoites) and was apparent within 48 hours of co-incubation of Caco-2 cells. Following Caco-2 monolayer co-incubation experiments with filtrates from four other Giardia parasite isolates (obtained originally from symptomatic and asymptomatic patients) a significant reduction (P<0.05) in protein concentration of Caco-2 cells was observed for one of the three (WH, symptomatic) isolates tested. No change in Caco-2 maltase was noted in this experiment. Growth curve analysis of various Giardia isolates was also carried out. Results showed that the isolates fell into two growth curve patterns (slow and fast growers). Differences in in vitro growth dynamics were found between the isolates. Growth curve patterns, however, did not predict either type of host source (symptomatic vs asymptomatic) or patterns in reduction of Caco-2 protein. Results of co-incubation of Caco-2 cells with WB filtrates are consistent with the hypothesis that the disaccharidase deficiency observed in human and animals with giardiasis may be associated with a direct effect produced by parasite excretory-secretory products on the intestinal brush border membrane. Caco-2 cells are a useful in vitro model for the further study of the pathogenesis of giardiasis.

Thesis/Dissertation

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2009-03-21

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http://hdl.handle.net/2429/6332

Pathology

University of British Columbia

UBCV

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