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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, United States.
Insights
CARD8 detects HIV-1 infection by sensing protease activity. This innate immune response is triggered during cell-to-cell HIV-1 transmission and is influenced by variations in HIV protease.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- The CARD8 inflammasome is activated by sensing HIV-1 protease activity.
- CARD8 possesses an N-terminal motif mimicking HIV protease substrates, enabling innate immune recognition.
- HIV-1 protease cleavage of this motif triggers CARD8 inflammasome activation.
Purpose of the Study:
- To investigate CARD8 inflammasome activation during HIV-1 cell-to-cell transmission.
- To determine the role of viral protease activity and NLRP3 inflammasome in this process.
- To evaluate how HIV protease variations impact CARD8 sensing.
Main Methods:
- Studied CARD8 inflammasome activation in primary human monocyte-derived macrophages during HIV-1 cell-to-cell transmission.
- Assessed the dependence on viral protease activity and the NLRP3 inflammasome.
- Utilized HIV-1 protease inhibitor-resistant clones to analyze variations in HIV protease function.
Main Results:
- HIV-1 cell-to-cell transmission induces CARD8 inflammasome activation.
- This activation is dependent on viral protease activity and largely independent of NLRP3.
- Mutant HIV-1 proteases differentially cleave and activate CARD8 compared to wildtype.
Conclusions:
- CARD8 activation is a key innate immune response during HIV-1 cell-to-cell spread.
- HIV protease activity is essential for CARD8 sensing in this context.
- Natural variations in HIV protease can modulate innate immune sensing and inflammation.
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.
