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Giardia lamblia: in vitro cytopathic effect of human isolates
B Chávez1, L González-Mariscal, R Cedillo-Rivera
1Department of Experimental Pathology, Centro de Investigación y de Estudios Avanzados, Mexico City, Mexico.
Abstract:
The variable clinical course of human giardiasis may be due in part to differences in the virulence of various strains of Giardia lamblia. To address this issue, the in vitro cytopathic effect of isolates obtained from human symptomatic or asymptomatic infections was assessed by ultrastructural and electrophysiological methods. Axenic trophozoites of 10 strains of G. lamblia isolated from children with infections in Mexico City were cultured for 12 to 24 hr on live MDCK epithelial cells. No decrease in transepithelial resistance of MDCK monolayers mounted in Ussing chambers was detected with any of the isolates analyzed. On the contrary, trophozoites or media in which the isolates grew produced up to a twofold increase in transepithelial resistance. Transmission and scanning electron microscopy revealed that all isolates of G. lamblia, irrespective of their origin, gave rise to focal regions of microvilli depletion. These modifications were induced by the close attachment of the ventrolateral flange of the parasite adhesive disk to the apical surface of MDCK cells. The circular imprints evolved progressively to larger areas devoid of microvilli. In conclusion, under in vitro conditions, isolates of G. lamblia trophozoites derived from symptomatic or asymptomatic human infections damage epithelial cultured cells mainly by depleting their microvilli. None of the isolates showed evidence of an invasive effect.
Insights
This study investigated Giardia lamblia strains from human infections. In vitro, all strains damaged epithelial cells by depleting microvilli, regardless of infection symptoms, showing no invasive effects.
Area of Science:
- Parasitology
- Cell Biology
- Infectious Diseases
Background:
- Human giardiasis presents a variable clinical course, potentially influenced by Giardia lamblia strain virulence.
- Understanding the in vitro cytopathic effects of different G. lamblia isolates is crucial for elucidating disease pathogenesis.
Purpose of the Study:
- To assess the in vitro cytopathic effect of Giardia lamblia isolates from symptomatic and asymptomatic human infections.
- To investigate potential differences in virulence among G. lamblia strains using ultrastructural and electrophysiological methods.
Main Methods:
- Axenic trophozoites of 10 G. lamblia strains from infected children were cultured on Madin-Darby Canine Kidney (MDCK) epithelial cells.
- Electrophysiological measurements using Ussing chambers assessed transepithelial resistance.
- Transmission and scanning electron microscopy examined cellular ultrastructure and parasite-host interactions.
Main Results:
- No decrease in transepithelial resistance was observed; instead, a twofold increase was noted with some isolates.
- All G. lamblia isolates induced focal microvilli depletion on MDCK cells.
- Parasite attachment via the adhesive disk's ventrolateral flange caused progressive microvilli loss.
Conclusions:
- In vitro, G. lamblia trophozoites from human infections damage cultured epithelial cells primarily by depleting microvilli.
- No significant differences in cytopathic effect were observed between isolates from symptomatic and asymptomatic infections.
- Under these in vitro conditions, no invasive potential was detected for any G. lamblia isolate.