Role of the CFTR in pathogenesis of Giardia duodenalis infections

Abstract text

Introduction

As a widespread protozoal parasite, Giardia duodenalis is a common cause for abdominal pain, malabsorption and diarrhea. Intestinal epithelial barrier defects are frequently observed in patients affected by the multifactorial disease giardiasis, which is characterized by "leaky" barriers due to the disturbance of the tight junction complex. While the exact mechanisms remain unknown, recent findings suggest a novel chain of events amounting in epithelial barrier breakdown, which starts with a disturbed ion homeostasis during the early infection phase. Amongst these intestinal ion transporters, the anion channel CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) has been shown to be severly affected upon infection regarding its gene expression as well as its function.

Objectives

We aim to shed light on the putative role of the CFTR channel in G. duodenalis infections by investigating its impact on pathogenesis at different infection stages and processes such as the early altered ion homeostasis, disruption of the tight junctional complex and cellular differentiation (goblet cell hyperplasia) during the late infection phase.

Materials & Methods

Using the CRISPR/Cas9-technology, healthy intestinal organoids were converted into functionally impaired CFTR-mutants through insertion of the most common mutation (F508del) found in cystic fibrosis (CF) patients, a disease caused by mutations in the CFTR gene. For comparison of CFTR-impaired vs CFTR-functional organoids, mutant and wildtype were cultured in a compartmentalized transwell system and monitored regarding epithelial integrity throughout the infection period via transepithelial electrical resistance (TEER) measurements.

Results

Data from prior experiments show a robust transcriptional and functional downregulation of the CFTR ion transporter. Preliminary infection experiments with healthy and CF-patient derived intestinal organoids hint towards an increased prevalence of Clca1-positive (goblet) cells during the late infection phase in CF-derived cultures as compared to wildtype organoids.

Conclusion

Due to the significant downregulation of the CFTR channel during G. duodenalis infections and its pathogenic role in a variety of different diseases, we hypothesized that non-functionality of this important ion channel may benefit the parasite during infection. Experiments using CFTR-impaired organoids are still ongoing and will be discussed during the conference.