Human Rotavirus Diarrhea Is Associated with Altered Trafficking and Expression of Apical Membrane Transport Proteins

ABSTRACT BackgroundRotavirus (RV) is the 5th leading cause of death in children <5 years old but the leading cause of diarrhea related deaths in this age group. The mechanism of RV diarrhea involves decreased activity of Na+-dependent solute transporters with increased luminal secretion of Cl- in the absence of significant histologic damage. While our understanding of RV diarrhea has come from studies in animal models and cancer cell lines, the mechanism of the diarrhea and the transport proteins affected in human RV disease remains only partially understood. This understanding is likely to impact drug development therapy for RV diarrhea. MethodsFormalin-fixed paraffin-embedded small intestinal specimens from patients diagnosed with RV diarrhea (confirmed by anti-RV antibodies) were analyzed by immunofluorescence for changes in apical/basolateral ion/nutrient transporters/channels as well as tight junctional and cytoskeletal proteins. Proximal small intestinal enteroids generated from biopsies obtained from healthy human subjects were grown as monolayers, differentiated to resemble villus epithelial cells, and infected with human RV. ResultsRV diarrhea was associated with reduced expression and intracellular localization of transport proteins normally found in the brush border membranes, including SGLT1, NHE3, NHE2, the Na+-dependent amino acid transporter SLC6A19, and CFTR. In contrast, basolateral proteins, including Na+/K+-ATPase, NKCC1, and β-catenin, the brush border marker ezrin, as well as the tight junction protein, ZO-1, were expressed and localized normally. RV-induced mislocalization of NHE3, SGLT1, SLC6A19 and CFTR was also seen when human small intestinal enteroids were infected with RV. ConclusionsThese data demonstrate a new pathophysiologic mechanism of acute diarrhea in which expression of multiple apical transport proteins are reduced. This acute diarrhea is likely to be caused by an effect on a common apical trafficking pathway, as exemplified by RV diarrhea, and its contribution to other enteric pathogen-induced diarrheal diseases should be determined.