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

Introduction: Autophagy has been recognized as a bona fide immunological process. Evidence has shown that this process in IFN-γ stimulated cells controls proliferation or eliminates its infection. However, little is known about the effect of infection on the host cell autophagy in the absence of IFN-γ.

Methods: Multiple autophagy detection methods and CRISPR/CAS9 technology were used to study -induced autophagy in HeLa and several other mammalian cell lines.

Results: Here, we report increased LC3 II, autophagosome-like membrane structures, enhanced autophagic flux, and decreased lysosomes in a range of mammalian cell lines without IFN-γ treatment after infection. Specifically, disruption of host (a necessary gene for autophagy) in HeLa cells promoted the intracellular replication of , with the transcript level of increased, compared with that in wild-type cells. Further, after infection, the abundance of Rab11A remained stable in wild-type HeLa cells but decreased in mutant. Disruption of in the HeLa cells compromised the proliferation of , and increased the transcription of in the parasite. Compared to the wild-type RH∆ strain, the ∆ mutant induces enhanced host autophagy in HeLa cells, and results in slower replication of the parasite.

Discussion: Collectively, these results indicate that host cell autophagy can limit proliferation in an IFN-γ independent manner, possibly by affecting the hijack of host Rab11A-positive vesicles by the parasite which involved TgGRA2. The findings provide novel insights into infection in host cells and toxoplasmosis research.