Host autophagy limits Toxoplasma gondii proliferation in the absence of IFN-γ by affecting the hijack of Rab11A-positive vesicles

IntroductionAutophagy has been recognized as a bona fide immunological process. Evidence has shown that this process in IFN-gamma stimulated cells controls Toxoplasma gondii proliferation or eliminates its infection. However, little is known about the effect of T. gondii infection on the host cell autophagy in the absence of IFN-gamma. MethodsMultiple autophagy detection methods and CRISPR/CAS9 technology were used to study T. gondii-induced autophagy in HeLa and several other mammalian cell lines. ResultsHere, we report increased LC3 II, autophagosome-like membrane structures, enhanced autophagic flux, and decreased lysosomes in a range of mammalian cell lines without IFN-gamma treatment after T. gondii infection. Specifically, disruption of host atg5 (a necessary gene for autophagy) in HeLa cells promoted the intracellular replication of T. gondii, with the transcript level of rab11a increased, compared with that in wild-type cells. Further, after T. gondii infection, the abundance of Rab11A remained stable in wild-type HeLa cells but decreased in atg5(-/-) mutant. Disruption of rab11a in the HeLa cells compromised the proliferation of T. gondii, and increased the transcription of gra2 in the parasite. Compared to the T. gondii wild-type RH increment ku80 strain, the increment gra2 mutant induces enhanced host autophagy in HeLa cells, and results in slower replication of the parasite. DiscussionCollectively, these results indicate that host cell autophagy can limit T. gondii proliferation in an IFN-gamma independent manner, possibly by affecting the hijack of host Rab11A-positive vesicles by the parasite which involved TgGRA2. The findings provide novel insights into T. gondii infection in host cells and toxoplasmosis research.

Automated summary

This study found that Toxoplasma gondii infection can increase the levels of the autophagy-related protein LC3 II, form autophagosome-like membrane structures, enhance autophagic flux, and decrease lysosomes in host cells in the absence of IFN-gamma. Further research revealed that disruption of the host autophagy gene atg5 promotes T. gondii replication, while disruption of the parasite's Rab11A gene suppresses its proliferation. The findings suggest that host cell autophagy can limit T. gondii replication in an IFN-gamma independent manner.