The morphological analysis of autophagy in primary skeletal muscle cells infected with Toxoplasma gondii.

Toxoplasma gondii is an obligate intracellular protozoan parasite, the causative agent of toxoplasmosis, one of the most widespread zoonoses in the world. During the host immune response, tissue cysts are formed, allowing the maintenance of the parasite within the host cell. Autophagy, a degradation process of cellular components, is critical for cellular homeostasis. Recently, it has been proposed that autophagy participates in host-pathogen interactions. Autophagic inducers (rapamycin or glucose plus serum deprivation) inhibited infection and parasite proliferation in a clinically relevant model of primary skeletal muscle cells (SkMC). The ultrastructural analysis showed in SkMC submitted to autophagic stimuli the presence of structures suggestive of autophagosomes close to the parasitophorous vacuole containing degraded parasites. Fluorescence microscopy results pointed out the increase in LC3 puncta in these cells after incubation with autophagic inducers. In the present study, SkMC autophagy controlled the proliferation of tachyzoites inside the cell, data reinforced by ultrastructural evidences and increased LC3 expression.