Tunnelling Nanotube Projections May Interfere with Toxoplasma gondii Interaction with Host Cells

Toxoplasma gondii, the causative agent of toxoplasmosis, a disease widely distributed, is an intracellular parasite that invades host cells of different tissues using specialized endocytic activity. Recent studies suggest that tunneling nanotubes (TNTs), thin cell-surface projections, may participate in the parasite-host cell interaction. Here we report results that suggest the involvement of host-cell TNTs in the adhesion of T. gondii tachyzoites to epithelial LLC-MK² cells. Microscopy analysis showed that incubating cells in a medium containing 0.45 M sucrose induces reversible assembly of TNTs without affecting cell viability. The presence of extended TNTs correlated with increased parasite adhesion and reduced parasite entry, thus suggesting a structural or signaling role in mediating adhesion. TNTs assembled following sucrose incubation contain both actin and tubulin components as determined by immunofluorescence microscopy. These results highlight a possible functional relevance of TNTs in T. gondii host cell interaction, especially in parasite adhesion, opening new perspectives for understanding T. gondii-host cell interaction.