Coronavirus disease 2019 (COVID-19) is frequently associated with neurological deficits, but how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces these effects remains unclear. ...Here, we show that astrocytes are readily infected by SARS-CoV-2, but surprisingly, neuropilin-1, not angiotensin-converting enzyme 2 (ACE2), serves as the principal receptor mediating cell entry. Infection is further positively modulated by the two-pore segment channel 2 (TPC2) protein that regulates membrane trafficking and endocytosis. Astrocyte infection produces a pathological response closely resembling reactive astrogliosis characterized by elevated type I interferon (IFN) production, increased inflammation, and the decreased expression of transporters of water, ions, choline, and neurotransmitters. These combined events initiated within astrocytes produce a hostile microenvironment that promotes the dysfunction and death of uninfected bystander neurons.
SARS-CoV-2 infection primarily targets the lung but may also damage other organs, including the brain, heart, kidney, and intestine. Central nervous system (CNS) pathologies include loss of smell and taste, headache, delirium, acute psychosis, seizures, and stroke. Pathological loss of gray matter occurs in SARS-CoV-2 infection, but it is unclear whether this is due to direct viral infection, indirect effects associated with systemic inflammation, or both. Here, we used induced pluripotent stem cell (iPSC)-derived brain organoids and primary human astrocytes from the cerebral cortex to study direct SARS-CoV-2 infection. Our findings support a model where SARS-CoV-2 infection of astrocytes produces a panoply of changes in the expression of genes regulating innate immune signaling and inflammatory responses. The deregulation of these genes in astrocytes produces a microenvironment within the CNS that ultimately disrupts normal neuron function, promoting neuronal cell death and CNS deficits.
The progressive depletion of quiescent "bystander" CD4 T cells, which are nonpermissive to HIV infection, is a principal driver of the acquired immunodeficiency syndrome (AIDS). These cells undergo ...abortive infection characterized by the cytosolic accumulation of incomplete HIV reverse transcripts. These viral DNAs are sensed by an unidentified host sensor that triggers an innate immune response, leading to caspase-1 activation and pyroptosis. Using unbiased proteomic and targeted biochemical approaches, as well as two independent methods of lentiviral short hairpin RNA–mediated gene knockdown in primary CD4 T cells, we identify interferon-γ–inducible protein 16 (IFI16) as a host DNA sensor required for CD4 T cell death due to abortive HIV infection. These findings provide insights into a key host pathway that plays a central role in CD4 T cell depletion during disease progression to AIDS.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The pathway causing CD4 T-cell death in HIV-infected hosts remains poorly understood although apoptosis has been proposed as a key mechanism. We now show that caspase-3-mediated apoptosis accounts ...for the death of only a small fraction of CD4 T cells corresponding to those that are both activated and productively infected. The remaining over 95% of quiescent lymphoid CD4 T cells die by caspase-1-mediated pyroptosis triggered by abortive viral infection. Pyroptosis corresponds to an intensely inflammatory form of programmed cell death in which cytoplasmic contents and pro-inflammatory cytokines, including IL-1β, are released. This death pathway thus links the two signature events in HIV infection-CD4 T-cell depletion and chronic inflammation-and creates a pathogenic vicious cycle in which dying CD4 T cells release inflammatory signals that attract more cells to die. This cycle can be broken by caspase 1 inhibitors shown to be safe in humans, raising the possibility of a new class of 'anti-AIDS' therapeutics targeting the host rather than the virus.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Human immunodeficiency virus (HIV) infection is currently incurable, due to the persistence of latently infected cells. The 'shock and kill' approach to a cure proposes to eliminate this reservoir ...via transcriptional activation of latent proviruses, enabling direct or indirect killing of infected cells. Currently available latency-reversing agents (LRAs) have however proven ineffective. To understand why, we used a novel HIV reporter strain in primary CD4
T cells and determined which latently infected cells are reactivatable by current candidate LRAs. Remarkably, none of these agents reactivated more than 5% of cells carrying a latent provirus. Sequencing analysis of reactivatable vs. non-reactivatable populations revealed that the integration sites were distinguishable in terms of chromatin functional states. Our findings challenge the feasibility of 'shock and kill', and suggest the need to explore other strategies to control the latent HIV reservoir.
While mRNA vaccines are proving highly efficacious against SARS-CoV-2, it is important to determine how booster doses and prior infection influence the immune defense they elicit, and whether they ...protect against variants. Focusing on the T cell response, we conducted a longitudinal study of infection-naïve and COVID-19 convalescent donors before vaccination and after their first and second vaccine doses, using a high-parameter CyTOF analysis to phenotype their SARS-CoV-2-specific T cells. Vaccine-elicited spike-specific T cells responded similarly to stimulation by spike epitopes from the ancestral, B.1.1.7 and B.1.351 variant strains, both in terms of cell numbers and phenotypes. In infection-naïve individuals, the second dose boosted the quantity and altered the phenotypic properties of SARS-CoV-2-specific T cells, while in convalescents the second dose changed neither. Spike-specific T cells from convalescent vaccinees differed strikingly from those of infection-naïve vaccinees, with phenotypic features suggesting superior long-term persistence and ability to home to the respiratory tract including the nasopharynx. These results provide reassurance that vaccine-elicited T cells respond robustly to emerging viral variants, confirm that convalescents may not need a second vaccine dose, and suggest that vaccinated convalescents may have more persistent nasopharynx-homing SARS-CoV-2-specific T cells compared to their infection-naïve counterparts.
The persistence of latent HIV proviruses in long-lived CD4(+) T cells despite antiretroviral therapy (ART) is a major obstacle to viral eradication. Because current candidate latency-reversing agents ...(LRAs) induce HIV transcription, but fail to clear these cellular reservoirs, new approaches for killing these reactivated latent HIV reservoir cells are urgently needed. HIV latency depends upon the transcriptional quiescence of the integrated provirus and the circumvention of immune defense mechanisms. These defenses include cell-intrinsic innate responses that use pattern-recognition receptors (PRRs) to detect viral pathogens, and that subsequently induce apoptosis of the infected cell. Retinoic acid (RA)-inducible gene I (RIG-I, encoded by DDX58) forms one class of PRRs that mediates apoptosis and the elimination of infected cells after recognition of viral RNA. Here we show that acitretin, an RA derivative approved by the US Food and Drug Administration (FDA), enhances RIG-I signaling ex vivo, increases HIV transcription, and induces preferential apoptosis of HIV-infected cells. These effects are abrogated by DDX58 knockdown. Acitretin also decreases proviral DNA levels in CD4(+) T cells from HIV-positive subjects on suppressive ART, an effect that is amplified when combined with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor. Pharmacological enhancement of an innate cellular-defense network could provide a means by which to eliminate reactivated cells in the latent HIV reservoir.
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IJS, NUK, SBMB, UL, UM, UPUK
Convalescing coronavirus disease 2019 (COVID-19) patients mount robust T cell responses against SARS-CoV-2, suggesting an important role of T cells in viral clearance. To date, the phenotypes of ...SARS-CoV-2-specific T cells remain poorly defined. Using 38-parameter CyTOF, we phenotyped longitudinal specimens of SARS-CoV-2-specific CD4+ and CD8+ T cells from nine individuals who recovered from mild COVID-19. SARS-CoV-2-specific CD4+ T cells were exclusively Th1 cells and predominantly Tcm cells with phenotypic features of robust helper function. SARS-CoV-2-specific CD8+ T cells were predominantly Temra cells in a state of less terminal differentiation than most Temra cells. Subsets of SARS-CoV-2-specific T cells express CD127, can proliferate homeostatically, and can persist for over 2 months. Our results suggest that long-lived and robust T cell immunity is generated following natural SARS-CoV-2 infection and support an important role of SARS-CoV-2-specific T cells in host control of COVID-19.
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SARS-CoV-2-specific T cells are diverse, express CD127, and can proliferateSARS-CoV-2-specific CD4+ T cells are IFNγ-producing, lymphoid-homing Tfh cellsSARS-CoV-2-specific CD8+ T cells are predominantly less-differentiated Temra cellsHoming features of SARS-CoV-2-specific CD4+ and CD8+ T cells differ
Combining CyTOF with single-cell detection of antigen-specific cells, Neidleman et al. provide an in-depth view of the phenotypic features of CD4+ and CD8+ T cells recognizing SARS-CoV-2 epitopes. These cells are different from T cells recognizing CMV, harbor diverse homing properties and effector functions, and include CD127-expressing cells.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Host repressors mediate HIV latency, but how they interactively silence the virus remains unclear. Here, we develop “reiterative enrichment and authentication of CRISPRi targets for synergies ...(REACTS)” to probe the genome for synergies between HIV transcription repressors. Using eight known host repressors as queries, we identify 32 synergies involving eleven repressors, including BCL7C, KANSL2, and SIRT2. Overexpression of these three proteins reduces HIV reactivation in Jurkat T cells and in CD4 T cells from people living with HIV on antiretroviral therapy (ART). We show that the BCL7C-containing BAF complex and the KANSL2-containing NSL complex form a “supercomplex” that increases inhibitory histone acetylation of the HIV long-terminal repeat (LTR) and its occupancy by the short variant of the acetyl-lysine reader Brd4. Collectively, we provide a validated platform for defining gene synergies genome wide, and the BAF-NSL “supercomplex” represents a potential target for overcoming HIV rebound after ART cessation.
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•A validated platform for identifying synergistic gene activities genome wide•A genetic interaction map of host repressors for HIV reactivation•Three HIV repressors identified: BCL7C, KANSL2, and SIRT2•A BAF-NSL “supercomplex” increases HIV LTR histone acetylation and blocks HIV transcription
Li et al. develop a genome-wide screen, REACTS, to identify genes synergistically repressing HIV. They find 32 synergies involving eleven repressors, including BCL7C, KANSL2, and SIRT2. Overexpressing these proteins reduces HIV reactivation in cells. BCL7C and KANSL2 are part of a BAF-NSL “supercomplex” inhibiting HIV via histone acetylation and Brd4S.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
19.
Shaping the nuclear action of NF-κB Greene, Warner C; Chen, Lin-Feng
Nature reviews. Molecular cell biology,
05/2004, Volume:
5, Issue:
5
Journal Article
Peer reviewed
The NF- Kappa B/REL family of transcription factors pivotally control the inflammatory and immune responses, as well as other genetic programmes that are central to cell growth and survival. The ...cytoplasmic regulation of NF- Kappa B is well characterized and, recently, significant progress has been made in understanding how its nuclear action is regulated. Post-translational modification of the NF- Kappa B subunits as well as histones surrounding the NF- Kappa B target genes has a key role in this regulation. Here, we review the important advances that constitute this new and exciting chapter in NF- Kappa B biology. In Summary: The nuclear factor (NF)- Kappa B/REL family of transcription factors regulate a diverse range of cellular responses, which include proliferation, differentiation, programmed cell death and tumorigenesis, and they are the 'master regulators' of inflammation and immunity. Classical NF- Kappa B activation involves stimulus-coupled phosphorylation of cytoplasmic I Kappa B inhibitors by I Kappa B kinases (IKK). The I Kappa B inhibitors are targeted to the 26S proteasome allowing the p50/RELA NF- Kappa B complexes to enter the nucleus and stimulate target-gene transcription. A parallel non-classical pathway of REL protein activation has been identified that generates nuclear p52/RELB heterodimers. Post-translational modifications, such as phosphorylation and acetylation, have recently been found to regulate NF- Kappa B transcriptional activity and contribute to shaping the strength and duration of the NF- Kappa B response. The RELA subunit of NF- Kappa B is targeted for stimulus-coupled phosphorylation at different sites by different kinases. RELA phosphorylation is generally associated with enhanced transcriptional activity of NF- Kappa B. RELA is modified by acetylation at key lysine residues. Site- specific acetylation controls different biological functions of NF- Kappa B including DNA binding, transcriptional activity and assembly with I Kappa B alpha . Deacetylation of RelA promotes I Kappa B alpha binding and nuclear export of the NF- Kappa B complex, thereby terminating the transcriptional response. Activation of NF- Kappa B-responsive genes also involves multiple modifications of histone proteins surrounding the target genes, so IKK can participate in both the first and second phases of the NF- Kappa B activation response. Analogous to the epigenetic histone code that might regulate gene expression through changes in chromatin structure, a transcription-factor code might exist, in which serial post-translational modifications of the transcription factor can alter its biological function.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The primary reservoir for HIV is within memory CD4+ T cells residing within tissues, yet the features that make some of these cells more susceptible than others to infection by HIV is not well ...understood. Recent studies demonstrated that CCR5-tropic HIV-1 efficiently enters tissue-derived memory CD4+ T cells expressing CD127, the alpha chain of the IL7 receptor, but rarely completes the replication cycle. We now demonstrate that the inability of HIV to replicate in these CD127-expressing cells is not due to post-entry restriction by SAMHD1. Rather, relative to other memory T cell subsets, these cells are highly prone to undergoing latent infection with HIV, as revealed by the high levels of integrated HIV DNA in these cells. Host gene expression profiling revealed that CD127-expressing memory CD4+ T cells are phenotypically distinct from other tissue memory CD4+ T cells, and are defined by a quiescent state with diminished NFκB, NFAT, and Ox40 signaling. However, latently-infected CD127+ cells harbored unspliced HIV transcripts and stimulation of these cells with anti-CD3/CD28 reversed latency. These findings identify a novel subset of memory CD4+ T cells found in tissue and not in blood that are preferentially targeted for latent infection by HIV, and may serve as an important reservoir to target for HIV eradication efforts.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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