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CARD8 inflammasome activation during HIV-1 cell-to-cell transmission
Jessie Kulsuptrakul1,2, Michael Emerman2, Patrick S Mitchell3,4
1Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98195, USA.
Insights
CARD8 detects HIV-1 protease activity during cell-to-cell transmission, activating the inflammasome. Variations in HIV protease impact this innate immune sensing and inflammation.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- CARD8 (Caspase-recruitment domain family member 8) recognizes HIV-1 protease activity.
- HIV-1 protease cleaves CARD8's N-terminal mimic motif, triggering inflammasome activation.
- Understanding CARD8's role in HIV-1 cell-to-cell transmission is crucial for innate immunity research.
Purpose of the Study:
- To investigate CARD8 inflammasome activation during HIV-1 cell-to-cell transmission via a viral synapse.
- To determine the role of HIV protease activity and variation in CARD8 sensing.
- To assess the contribution of NLRP3 inflammasome in this context.
Main Methods:
- Studied CARD8 inflammasome activation in primary human monocyte-derived macrophages during HIV-1 cell-to-cell transfer.
- Utilized HIV-1 protease inhibitor resistant clones to analyze viral determinants of CARD8 sensing.
- Assessed CARD8 activation in response to wildtype and mutant HIV-1 proteases.
Main Results:
- HIV-1 cell-to-cell transmission robustly induces CARD8 inflammasome activation.
- This activation is dependent on HIV protease activity but largely independent of NLRP3 inflammasome.
- Mutant HIV-1 proteases exhibit differential cleavage and activation of CARD8 compared to wildtype.
Conclusions:
- CARD8 senses HIV-1 protease activity during cell-to-cell transmission.
- HIV-1 protease variation influences both viral polyprotein processing and innate immune sensing.
- These findings highlight the impact of viral protease evolution on host inflammatory responses.
Abstract:
Our previous work demonstrated that CARD8 detects HIV-1 infection by sensing the enzymatic activity of the HIV protease, resulting in CARD8-dependent inflammasome activation (Kulsuptrakul et al., 2023). CARD8 harbors a motif in its N-terminus that functions as a HIV protease substrate mimic, permitting innate immune recognition of HIV-1 protease activity, which when cleaved by HIV protease triggers CARD8 inflammasome activation. Here, we sought to understand CARD8 responses in the context of HIV-1 cell-to-cell transmission via a viral synapse. We observed that cell-to-cell transmission of HIV-1 between infected T cells and primary human monocyte-derived macrophages induces CARD8 inflammasome activation in a manner that is dependent on viral protease activity and largely independent of the NLRP3 inflammasome. Additionally, to further evaluate the viral determinants of CARD8 sensing, we tested a panel of HIV protease inhibitor resistant clones to establish how variation in HIV protease affects CARD8 activation. We identified mutant HIV-1 proteases that differentially cleave and activate CARD8 compared to wildtype HIV-1, thus indicating that natural variation in HIV protease affects not only the cleavage of the viral Gag-Pol polyprotein but also likely impacts innate sensing and inflammation.
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