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Cell invasion and intracellular fate of Encephalitozoon cuniculi (Microsporidia)

Published online by Cambridge University Press:  18 November 2004

C. FRANZEN
Affiliation:
Department of Internal Medicine I, University of Regensburg, Franz-Josef Strauß Allee 11, 93042 Regensburg, Germany
A. MÜLLER
Affiliation:
Department of Pediatrics, University of Bonn, Adenauerallee 119, 53113 Bonn, Germany
P. HARTMANN
Affiliation:
Department of Internal Medicine I, University of Regensburg, Franz-Josef Strauß Allee 11, 93042 Regensburg, Germany
B. SALZBERGER
Affiliation:
Department of Internal Medicine I, University of Regensburg, Franz-Josef Strauß Allee 11, 93042 Regensburg, Germany

Abstract

Microsporidia are obligate intracellular parasites that utilize a unique mechanism to infect host cells, which is one of the most sophisticated infection mechanisms in biology. Microsporidian spores contain a long coiled polar tube that extrudes from the spores and penetrates the membranes of new host cells. We have initiated a study to investigate the invasive process and intracellular fate of the microsporidium Encephalitozoon cuniculi. Here we show that relatively few cells were infected through the traditional penetration of the polar tube from outside. Rather, phagocytosis of spores occurred at least 10 times more frequently than injection of sporoplasms. Some spores extruded their polar tube inside the cells following phagocytosis. Membranes of the vacuoles surrounding the internalized spores were positive for late endosomal and lysosomal markers. Spores that remained inside these compartments disappeared within 3 days. Thus, our studies demonstrate that in addition to the unique way in which microsporidia infect host cells, E. cuniculi spores can also gain access to host cells by phagocytosis. The presence of intracellular spores that have extruded their polar tube shows that some spores germinate after phagocytosis, thus escaping from the phagosomes that mature into lysosomes.

Type
Research Article
Copyright
2005 Cambridge University Press

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