Human immunodeficiency virus type 2 (HIV-2) infection results in a milder course of disease and slower progression to AIDS than does HIV-1. We hypothesized that this difference may be due to ...degradation of the sterile alpha motif and HD domain 1 (SAMHD1) host restriction factor by the HIV-2 Vpx gene product, thereby diminishing abortive infection and pyroptotic cell death within bystander CD4 T cells. We have compared CD4 T cell death in tonsil-derived human lymphoid aggregate cultures (HLACs) infected with wild-type HIV-2, HIV-2 ΔVpx, or HIV-1. In contrast to our hypothesis, HIV-2, HIV-2 ΔVpx, and HIV-1 induced similar levels of bystander CD4 T cell death. In all cases, cell death was blocked by AMD3100, a CXCR4 entry inhibitor, but not by raltegravir, an integrase, indicating that only early life cycle events were required. Cell death was also blocked by a caspase-1 inhibitor, a key enzyme promoting pyroptosis, but not by a caspase-3 inhibitor, an important enzyme in apoptosis. HIV-1-induced abortive infection and pyroptotic cell death were also not reduced by forced encapsidation of HIV-2 Vpx into HIV-1 virions. Together, these findings indicate that HIV-2 and HIV-1 support similar levels of CD4 T cell depletion
despite HIV-2 Vpx-mediated degradation of the SAMHD1 transcription factor. The milder disease course observed with HIV-2 infection likely stems from factors other than abortive infection and caspase-1-dependent pyroptosis in bystander CD4 T cells.
CD4 T cell depletion during HIV-1 infection involves the demise of bystander CD4 T cells due to abortive infection, viral DNA sensing, inflammasome assembly, and death by caspase-1-dependent pyroptosis. HIV-2 infection is associated with milder disease and lower rates of CD4 T cell loss. We hypothesized that HIV-2 infection produces lower levels of pyroptosis due to the action of its Vpx gene product. Vpx degrades the SAMHD1 restriction factor, potentially reducing abortive forms of infection. However, in tonsil cell cultures, HIV-2, HIV-2 ΔVpx, and HIV-1 induced indistinguishable levels of pyroptosis. Forced encapsidation of Vpx into HIV-1 virions also did not reduce pyroptosis. Thus, SAMHD1 does not appear to play a key role in the induction of bystander cell pyroptosis. Additionally, the milder clinical course of HIV-2-induced disease is apparently not explained by a decrease in this inflammatory form of programmed cell death.
Transcription of hepatitis B Virus (HBV), an important risk factor of hepatocellular carcinoma (HCC), is controlled by cellular transcription activators including some of the cellular signaling ...targets. Consequently, HBV transcription rate changes in response to the cellular physiological conditions. In this report we investigated HBV gene expression and the role of physiological levels of the viral X protein (pX) under cisplatin induced genotoxic stress. We show that under these conditions the RNA level of an HBV mutant which does not express pX is sharply reduced. Studies revealed that transcription repression is responsible for the observed reduction in HBV RNA level. Repression of HBV transcription was obtained only in the p53 proficient cells. Furthermore, HBV transcription rate is recovered by the cotransfected p53 dominant negative plasmid, indicating that p53 is directly responsible for HBV transcription repression. Unexpectedly, p73, the recent p53 homologue, does not repress but rather activates HBV transcription. Interestingly, pX produced either by the HBV genome or by a cotransfected plasmid, relieves the p53 mediated repression. Collectively, these results attribute a physiological role to p53-inactivation by pX, and explain how pX may support HCC development.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•TCR activation induces IL1B gene transcription in CD4 T cells.•Unlike monocytes, IL1B in T cells is independent of critical myeloid Spi1 protein.•Spi1 binding site on IL1B promoter ...is blocked by a nucleosome in CD4 T cells.•Distinctly, IL1B gene in CD4 T cells utilizes a bivalent H3K4me3/H3k27me3 promoter.
Interleukin 1β is a pro-inflammatory cytokine important for both normal immune responses and chronic inflammatory diseases. The regulation of the 31 kDa proIL-1β precursor coded by the IL1B gene has been extensively studied in myeloid cells, but not in lymphoid-derived CD4 T cells. Surprisingly, we found that some CD4 T cell subsets express higher levels of proIL-1β than unstimulated monocytes, despite relatively low IL1B mRNA levels. We observed a significant increase in IL1B transcription and translation in CD4 T cells upon ex vivo CD3/CD28 activation, and a similar elevation in the CCR5+ effector memory population compared to CCR5− T cells in vivo. The rapid and vigorous increase in IL1B gene transcription for stimulated monocytes has previously been associated with the presence of Spi-1/PU.1 (Spi1), a myeloid-lineage transcription factor, pre-bound to the promoter. In the case of CD4 T cells, this increase occurred despite the lack of detectable Spi1 at the IL1B promoter. Additionally, we found altered epigenetic regulation of the IL1B locus in CD3/CD28–activated CD4 T cells. Unlike monocytes, activated CD4 T cells possess bivalent H3K4me3+/H3K27me3+ nucleosome marks at the IL1B promoter, reflecting low transcriptional activity. These results support a model in which the IL1B gene in CD4 T cells is transcribed from a low-activity bivalent promoter independent of Spi1. Accumulated cytoplasmic proIL-1β may ultimately be cleaved to mature 17 kDa bioactive IL-1β, regulating T cell polarization and pathogenic chronic inflammation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Resting human CD4 T cells are highly resistant to transfection or infection with lentiviral vectors derived from the human immunodeficiency virus. We now describe a flexible and efficient approach ...involving virus-like particles containing simian immunodeficiency virus lentiviral gene product protein X and pseudotyping with CXCR4-tropic HIV Env. This method permits effective genetic manipulation of these cells while preserving their naturally quiescent state. This technology can also be extended to primary lymphoid cultures where authentic cellular composition and functional relationships are preserved.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Transcription of IL-1β activity has been extensively studied in stimulated myeloid cells, but not in lymphoid-derived CD4 T cells, the primary cellular target for infection by HIV. Most ...CCR5+ CD4 T cells in lymphoid tissues are non-permissive for productive HIV infection and die by Caspase-1-mediated pyroptosis, in which proInterleukin 1β (proIL-1β) precursor is converted to highly active mature IL-1β. It is unclear whether expression of proIL-1β protein in CCR5+ CD4 T cells is derived from active transcription of the IL1B gene, or from previously transcribed mRNA and/or stored protein. Our results reveal that despite very low amounts of IL1B mRNA, CCR5+ CD4 T cells accumulate intracellular proIL-1β protein at levels higher than that of both unstimulated myeloid THP-1 cells and CCR5− CD4 T cells. Further, we observe that the chromatin from CCR5+, but not CCR5− CD4 T cells, contain RNA polymerase II and bivalent H3K4me3 and H3K27me3 nucleosomes at the IL1B promoter, consistent with developmentally regulated constitutive gene expression. This observation contrasts with the rapidly activated and extremely robust H3K4me3 monovalent IL1B gene promoter in TLR4-activated monocytes. This unique phenomenon of CCR5+ CD4 T cells is important to understanding how non-myeloid lineage cells express and release significant levels of IL-1β in the apparent absence of transcription induction.
The progressive depletion of CD4 T cells causes clinical progression to AIDS in untreated HIV-infected subjects. Most dying CD4 T cells correspond to resting nonpermissive cells residing in lymphoid ...tissues. These cells die predominantly because of an innate immune response against the incomplete cytosolic viral DNA intermediates that accumulate in these cells. The DNA is detected by the IFI16 sensor leading to inflammasome assembly, caspase 1 activation, and the induction of pyroptosis, a highly inflammatory form of programmed cell death. We now show that cell-to-cell transmission of HIV is obligately required for activation of this death pathway. Cell-free HIV-1 virions, even when added in large quantities, fail to activate pyroptosis. These findings underscore infected CD4 T cell as the major killing units promoting progression to AIDS and highlight a previously unappreciated role for the virological synapse.
145 Pyroptosis and HIV-Induced CD4 T Cell Death Doitsh, Gilad; Zepeda, Orlando; Galloway, Nicole ...
Journal of acquired immune deficiency syndromes (1999),
04/2012, Volume:
59
Journal Article
Peer reviewed
While progressive depletion of CD4 T cells is a hallmark of untreated HIV infection, the underlying mechanism(s) remains poorly understood. HIV infection can directly kill CD4 T cells but the number ...of productively infected cells in vivo does not account for the massive CD4 T-cell losses observed in infected patients. Many dying cells appear to correspond to bystander CD4 T cells. Using human tonsil and spleen tissue infected with HIVNL4-3, we have observed the following: 1) bystander cell death is associated with abortive infection of bystander CD4 T cells leading to the accumulation incomplete HIV reverse transcripts; 2) CD4 T cells die as a result of an innate immune response elicited by this cytosolic viral DNA involving interferon-beta production and activation of caspase-3 and caspase-1; 3) a major mechanism of bystander cell death includes caspase-1-dependent pyroptosis, an intensely inflammatory form of programmed cell death where cytoplasmic contents and pro-inflammatory cytokines are released into the extracellular space. Pyropotosis likely drives chemokine-dependent recruitment of additional CD4 T cells triggering new rounds of infection and cell death that subverts effectiveness of the innate immune response. These findings provide a new mechanism linking HIV infection with inflammation and raise the possibility that anti-pyroptotic agents might block HIV-induced CD4 T cell depletion. Such agents might have special utility in individuals displaying rapid progression of disease or broad drug resistance. PUBLICATION ABSTRACT
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