Autophagy activated by Toxoplasma gondii infection in turn facilitates Toxoplasma gondii proliferation

Autophagy was found to play an antimicrobial or antiparasitic role in the activation of host cells to defend against intracellular pathogens, at the same time, pathogens could compete with host cell and take advantage of autophagy to provide access for its proliferation, but there are few articles for studying the outcome of this competition between host cell and pathogens. Therefore, the aim of our study was to investigate the relationship between autophagy activated by Toxoplasma gondii (T. gondii) and proliferation of T. gondii affected by autophagy in vitro. Firstly, human embryonic fibroblasts (HEF) cells were infected with T. gondii for different times. The monodansylcadaverine (MDC) staining, acridine orange (AO) staining, punctuate GFP-LC3 distribution, and transmission electron microscopy (TEM) assays were conducted, and the results were consistent in showing that gondii infection could induce autophagy. Secondly, HEF cells were infected with T. gondii and treated with autophagy inhibitor bafilomycin A1 or inducer lithium chloride for different times. Giemsa staining was conducted, and the results exhibited that T. gondii infection-induced autophagy could in turn promote T. gondii proliferation. Simultaneously, the results of Giemsa staining also revealed that autophagy inhibitor could reduce the number of each cell infected with T. gondii and inhibit T. gondii proliferation. In contrast, autophagy inducer could increase the number of each cell infected with T. gondii and encourage T. gondii proliferation. Therefore, our study suggests that T. gondii infection could activate autophagy, and this autophagy could in turn facilitate T. gondii proliferation in HEF cells for limiting nutrients.