Adherence and multiplication of Giardia intestinalis on human enterocyte-like differentiated cells in vitro

This report describes a technique for studying the adherence and growth of Giardia intestinalis trophozoites (strains PARIS/86/LCF/1, PARIS/86/LCF/2 and PARIS/88/LCF/8) using the human colon carcinoma cell line Caco2. Giardia trophozoites were cultured with Caco2 cells in a modified HSP3 culture medium. The biochemical differentiation of Caco2 cells was established by an increase in sucrase isomaltase activities to values of 4.51 +/- 0.90 and 10.39 +/- 3.00 milliunits/mg protein for 8- and 12-day-old cultures, respectively. Giardia, adherence to 8- and 12-day-old Caco2 cells reached a value of greater than 75% after 60 and 30 min, respectively. Adherence diminished significantly at 24 degrees C and was almost undetectable at 4 degrees C. Depletion of divalent cations reduced the proportion of adherent trophozoites by up to 46%. Adherence was pH-independent between pH 6.0 and 7.6. Parasite growth increased when Caco2 cell monolayers were used instead of axenic cultures. This in vitro human cell model may contribute to the study of the mechanisms and factors involved in the host-parasite interaction.