The secreted kinase ROP17 promotes Toxoplasma gondii dissemination by hijacking monocyte tissue migration


The protozoan parasite Toxoplasma gondii is thought to exploit monocyte trafficking to facilitate dissemination across endothelial barriers such as the blood–brain barrier. Here, we analysed the migration of parasitized monocytes in model endothelial and interstitial environments. We report that infection enhanced monocyte locomotion on the surface of endothelial cells, but profoundly inhibited monocyte transmigration across endothelial barriers. By contrast, infection robustly increased monocyte and macrophage migration through collagen-rich tissues in a Rho–ROCK-dependent manner consistent with integrin-independent interstitial migration. We further demonstrated that the secreted T.gondii protein kinase ROP17 was required for enhanced tissue migration. In vivo, ROP17-deficient parasites failed to upregulate monocyte tissue migration and exhibited an early dissemination delay, leading to prolonged mouse survival. Our findings indicate that the parasite-induced changes in monocyte motility primarily facilitate the transport of T.gondii through tissues and promote systemic dissemination, rather than shuttle parasites across the blood–brain barrier via extravasation.

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Fig. 1: TEM and adherence of infected THP-1 and primary monocytes.
Fig. 2: Locomotion of infected THP-1 monocytes on the hCMEC/D3 model of the BBB.
Fig. 3: Migration of infected cells through 3D collagen matrices and skin tissue.
Fig. 4: Enhanced tissue migration may involve Rho–ROCK and requires parasite ROP17.
Fig. 5: Role of ROP17 during in vivo infection.
Fig. 6: In vivo and ex vivo motility of splenic CX3CR1GFP/+ cells infected with WT and Δrop17 parasites.

Data availability

All data generated and analysed during this study are included within the paper and the associated Supplementary Information.


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We thank J. A. Cooper for constructive comments; R. Klein and T. Doering for sharing the hCMEC/D3 cells; T. Fehniger for facilitating the acquisition of primary human monocytes; F. Santiago and H. Salimi for advice regarding the BBB model; S. Kim, L. Yang and the Washington University School of Medicine In vivo Imaging Core for technical support and fluorescent reporter mice for the intravital imaging experiments; and G. Randolph for generously sharing the CX3CR1GFP/+ mice. Work was supported in part by grants from the National Science Foundation to L.L.D. (DGE-1143954), and from the National Institutes of Health to M.J.M. (R01AI077600) and L.D.S. (AI034036).

Author information

L.L.D. and L.D.S. designed the experiments and wrote the manuscript. N.G.J. generated the T.gondii strains used for time-lapse microscopy. Q.W. collaborated on the design and execution of animal studies. M.D.O. collaborated on the design and interpretation of the Rho GTPase inhibitor studies. L.L.D. and M.J.M. designed and performed the two-photon imaging experiments. L.L.D. performed all other experiments and analysed the data. L.D.S. supervised the study. All authors critically reviewed and approved the manuscript.

Correspondence to L. David Sibley.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–6, Supplementary Video legends, Supplementary Tables 1–3 and Supplementary References.

Reporting Summary

Supplementary Video 1

Uninfected THP-1 monocyte motility on hCMEC/D3 (shown in Fig. 2).

Supplementary Video 2

Infected THP-1 monocyte motility on hCMEC/D3 (shown in Fig. 2).

Supplementary Video 3

Infected THP-1 monocyte motility on hCMEC/D3 (shown in Fig. 2).

Supplementary Video 4

Uninfected CX3CR1GFP/+ cell migrating in spleen (shown in Fig. 6).

Supplementary Video 5

Infected CX3CR1GFP/+ cell migrating in spleen (shown in Fig. 6).

Supplementary Video 6

Infected CX3CR1GFP/+ cell migrating in spleen (shown in Fig. 6).

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Drewry, L.L., Jones, N.G., Wang, Q. et al. The secreted kinase ROP17 promotes Toxoplasma gondii dissemination by hijacking monocyte tissue migration. Nat Microbiol 4, 1951–1963 (2019).

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