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bioRxiv · 10.1101/2024.02.02.578698

Caspase-8 activity mediates TNFα production and restricts Coxiella burnetii replication during murine macrophage infection

Osbron, C. A.·Lawson, C.·Hanna, N.·Koehler, H.·Goodman, A. G.
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Abstract

Coxiella burnetii is an obligate intracellular bacteria which causes the global zoonotic disease Q Fever. Treatment options for infection are limited, and development of novel therapeutic strategies requires a greater understanding of how C. burnetii interacts with immune signaling. Cell death responses are known to be manipulated by C. burnetii, but the role of caspase-8, a central regulator of multiple cell death pathways, has not been investigated. In this research, we studied bacterial manipulation of caspase-8 signaling and the significance of caspase-8 to C. burnetii infection, examining bacterial replication, cell death induction, and cytokine signaling. We measured caspase, RIPK, and MLKL activation in C. burnetii-infected TNF/CHX-treated THP-1 macrophage-like cells and TNF/ZVAD-treated L929 cells to assess apoptosis and necroptosis signaling. Additionally, we measured C. burnetii replication, cell death, and TNF induction over 12 days in RIPK1-kinase-dead, RIPK3-kinase-dead, or RIPK3-kinase-dead-caspase-8-/- BMDMs to understand the significance of caspase-8 and RIPK1/3 during infection. We found that caspase-8 is inhibited by C. burnetii, coinciding with inhibition of apoptosis and increased susceptibility to necroptosis. Furthermore, C. burnetii replication was increased in BMDMs lacking caspase-8, but not in those lacking RIPK1/3 kinase activity, corresponding with decreased TNF production and reduced cell death. As TNF is associated with the control of C. burnetii, this lack of a TNF response may allow for the unchecked bacterial growth we saw in caspase-8-/- BMDMs. This research identifies and explores caspase-8 as a key regulator of C. burnetii infection, opening novel therapeutic doors.

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Osbron, C. A., Lawson, C., Hanna, N., Koehler, H., Goodman, A. G.. 2024-02-03. Caspase-8 activity mediates TNFα production and restricts Coxiella burnetii replication during murine macrophage infection. https://doi.org/10.1101/2024.02.02.578698

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