Blood-Derived CD4 T Cells Naturally Resist Pyroptosis during Abortive HIV-1 Infection

Significance Statement

Blood-Derived CD4 T cells are Resistant to Pyroptosis During HIV-1 Infection

The progressive loss of CD4 T cells lies at the heart of HIV/AIDS. HIV infects and kills activated CD4 T cells by apoptosis, but these permissive cells are too few in number to explain the massive CD4 T cell losses observed in untreated, HIV-infected people.  We recently reported that most CD4 T cells residing in lymphoid tissues correspond to bystander cells that die by abortive HIV infection involving pyroptosis, a highly inflammatory form of programmed cell death. For pyroptosis to occur, the virus must be transmitted to quiescent CD4 T cells through virological synapses (cell-to-cell transmission is required)(Galloway et al., 2015), but in these resting cells, the viral life cycle is arrested during the elongation step of reverse transcription.  Consequently, incomplete HIV DNA transcripts accumulate in the cytosol.  These viral DNAs are detected by the IFI16 DNA sensor (Monroe et al., 2014), which can recognize both single and double stranded DNA targets. Detection of these transcripts triggers an innate immune response involving the assembly of the IFI16 inflammasome, induction of type I interferon and pyroptosis involving caspase-1 activation.

Pyroptosis of spleen, tonsil, and gut-associated-lymphoid tissue-derived CD4 T cells infected with CXCR4 or CCR5 tropic HIV has been shown (Doitsh et al., 2010; Doitsh et al., 2014; Steele et al., 2014) but the susceptibility of blood-derived CD4 T cells to this mechanism of depletion was unknown. We now report that CD4 T cells are resistant to this death pathway while circulating in the blood stream. This resistance is, at least in part, due to a deeper resting state for these cells resulting in the accumulation of less HIV DNA transcripts and lower expression of the DNA sensor, IFI16. Surprisingly, co-culture allowing direct contact with lymphoid tissue-derived CD4 T, CD8 T, or B cells renders blood-derived CD4 T cells sensitive to HIV mediated pyroptosis. Reverse transcription improves and IFI16 levels rise. Continuous interaction between the tissue and blood cells are required to maintain the sensitivity to pyroptosis. The natural resistance of blood cells to HIV-elicited pyroptosis extends beyond virally infected cells––exposure of these cells to nigericin, an activator of the NLRP3 inflammasome also does not result in pyroptosis(Munoz-Arias et al., 2015)

Our work highlights how the tissue micro-environment shapes the response of CD4 T cells to HIV infection. Indeed, if we had begun our studies with blood instead of lymphoid tissue-derived CD4 T cells, we would have not detected the pyroptotic death pathway, which appears to account for depletion of a significant fraction of CD4 T cells during HIV infection. Further studies are now underway to identify the lymphoid tissue factor(s) involved in sensitizing CD4 T cells to HIV-mediated pyroptosis. Inhibition of the interplay of these factors could lead to host directed therapy that would prevent CD4 T cell death but it will be important to exclude detrimental effects of this treatment on the normal immune response.



Doitsh, G., Cavrois, M., Lassen, K.G., Zepeda, O., Yang, Z., Santiago, M.L., Hebbeler, A.M., and Greene, W.C. (2010). Abortive HIV infection mediates CD4 T cell depletion and inflammation in human lymphoid tissue. Cell 143, 789-801.

Doitsh, G., Galloway, N., Geng, X., Yang, Z., Monroe, K., Zepeda, O., Hunt, P.W., Hatano, H., Sowinski, S., Munoz-Arias, I., et al. (2014). Cell death by pyroptosis drives CD4 T-cell depletion in HIV-1 infection. Nature 505, 509-514.

Galloway, N.L., Doitsh, G., Monroe, K.M., Yang, Z., Munoz-Arias, I., Levy, D.N., and Greene, W.C. (2015). Cell-to-Cell Transmission of HIV-1 Is Required to Trigger Pyroptotic Death of Lymphoid-Tissue-Derived CD4 T Cells. Cell reports 12, 1555-1563.

Monroe, K.M., Yang, Z., J.R., J., Geng, X., Doitsh, G., Krogan, N.J., and Greene, W.C. (2014). IFI16 DNA Sensor is Required for Death of Lymphoid CD4 T cells Abortively Infected with HIV. Science (New York, NY) 343, 428-432.

Munoz-Arias, I., Doitsh, G., Yang, Z., Sowinski, S., Ruelas, D., and Greene, W.C. (2015). Blood-Derived CD4 T Cells Naturally Resist Pyroptosis during Abortive HIV-1 Infection. Cell host & microbe 18, 463-470.

Steele, A.K., Lee, E.J., Manuzak, J.A., Dillon, S.M., Beckham, J.D., McCarter, M.D., Santiago, M.L., and Wilson, C.C. (2014). Microbial exposure alters HIV-1-induced mucosal CD4+ T cell death pathways ex vivo. Retrovirology 11, 14.

Blood-Derived CD4 T Cells Naturally Resist Pyroptosis during Abortive HIV-1 Infection. Global Medical Discovery

Journal Reference

Cell Host Microbe. 2015;18(4):463-70.

Isa Muñoz-Arias,1,2 Gilad Doitsh,2 Zhiyuan Yang,2 Stefanie Sowinski,2 Debbie Ruelas2 and Warner C. Greene2,3,

[expand title=”Show Affiliations”]
  1. School of Public Health, Division of Infectious Diseases and Virology, University of California, Berkeley, Berkeley, California 94720 USA.
  2. Gladstone Institute of Virology and Immunology, 1650 Owens Street, San Francisco, California 94158 USA.
  3. Departments of Medicine and 4Microbiology and Immunology, University of California, San Francisco, San Francisco, California 94158 USA. Correspondence: [email protected]


Progression to AIDS is driven by CD4 T cell depletion, mostly involving pyroptosis elicited by abortive HIV infection of CD4 T cells in lymphoid tissues. Inefficient reverse transcription in these cells leads to cytoplasmic accumulation of viral DNAs that are detected by the DNA sensor IFI16, resulting in inflammasome assembly, caspase-1 activation, and pyroptosis. Unexpectedly, we found that peripheral blood-derived CD4 T cells naturally resist pyroptosis. This resistance is partly due to their deeper resting state, resulting in fewer HIV-1 reverse transcripts and lower IFI16 expression. However, when co-cultured with lymphoid-derived cells, blood-derived CD4 T cells become sensitized to pyroptosis, likely recapitulating interactions occurring within lymphoid tissues. Sensitization correlates with higher levels of activated NF-κB, IFI16 expression, and reverse transcription. Blood-derived lymphocytes purified from co-cultures lose sensitivity to pyroptosis. These differences highlight how the lymphoid tissue microenvironment encountered by trafficking CD4 T lymphocytes dynamically shapes their biological response to HIV.

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