Microglia Require CD4 T Cells to Complete the Fetal-to-Adult Transition.

The brain is a site of relative immune privilege. Although CD4 T cells have been reported in the central nervous system, their presence in the healthy brain remains controversial, and their function remains largely unknown. We used a combination of imaging, single cell, and surgical approaches to identify a CD69+ CD4 T cell population in both the mouse and human brain, distinct from circulating CD4 T cells. The brain-resident population was derived through in situ differentiation from activated circulatory cells and was shaped by self-antigen and the peripheral microbiome. Single-cell sequencing revealed that in the absence of murine CD4 T cells, resident microglia remained suspended between the fetal and adult states. This maturation defect resulted in excess immature neuronal synapses and behavioral abnormalities. These results illuminate a role for CD4 T cells in brain development and a potential interconnected dynamic between the evolution of the immunological and neurological systems. VIDEO ABSTRACT.

Astrocyte-targeted gene delivery of interleukin 2 specifically increases brain-resident regulatory T cell numbers and protects against pathological neuroinflammation.

The ability of immune-modulating biologics to prevent and reverse pathology has transformed recent clinical practice. Full utility in the neuroinflammation space, however, requires identification of both effective targets for local immune modulation and a delivery system capable of crossing the blood-brain barrier. The recent identification and characterization of a small population of regulatory T (Treg) cells resident in the brain presents one such potential therapeutic target. Here, we identified brain interleukin 2 (IL-2) levels as a limiting factor for brain-resident Treg cells. We developed a gene-delivery approach for astrocytes, with a small-molecule on-switch to allow temporal control, and enhanced production in reactive astrocytes to spatially direct delivery to inflammatory sites. Mice with brain-specific IL-2 delivery were protected in traumatic brain injury, stroke and multiple sclerosis models, without impacting the peripheral immune system. These results validate brain-specific IL-2 gene delivery as effective protection against neuroinflammation, and provide a versatile platform for delivery of diverse biologics to neuroinflammatory patients.

The tissue-resident regulatory T cell pool is shaped by transient multi-tissue migration and a conserved residency program.

The tissues are the site of many important immunological reactions, yet how the immune system is controlled at these sites remains opaque. Recent studies have identified Foxp3+ regulatory T (Treg) cells in non-lymphoid tissues with unique characteristics compared with lymphoid Treg cells. However, tissue Treg cells have not been considered holistically across tissues. Here, we performed a systematic analysis of the Treg cell population residing in non-lymphoid organs throughout the body, revealing shared phenotypes, transient residency, and common molecular dependencies. Tissue Treg cells from different non-lymphoid organs shared T cell receptor (TCR) sequences, with functional capacity to drive multi-tissue Treg cell entry and were tissue-agnostic on tissue homing. Together, these results demonstrate that the tissue-resident Treg cell pool in most non-lymphoid organs, other than the gut, is largely constituted by broadly self-reactive Treg cells, characterized by transient multi-tissue migration. This work suggests common regulatory mechanisms may allow pan-tissue Treg cells to safeguard homeostasis across the body.

Regulatory T Cell-Derived TGF-ß1 Controls Multiple Checkpoints Governing Allergy and Autoimmunity.

The mechanisms by which regulatory T (Treg) cells differentially control allergic and autoimmune responses remain unclear. We show that Treg cells in food allergy (FA) had decreased expression of transforming growth factor beta 1 (TGF-ß1) because of interleukin-4 (IL-4)- and signal transducer and activator of transciription-6 (STAT6)-dependent inhibition of Tgfb1 transcription. These changes were modeled by Treg cell-specific Tgfb1 monoallelic inactivation, which induced allergic dysregulation by impairing microbiota-dependent retinoic acid receptor-related orphan receptor gamma t (ROR-γt)+ Treg cell differentiation. This dysregulation was rescued by treatment with Clostridiales species, which upregulated Tgfb1 expression in Treg cells. Biallelic deficiency precipitated fatal autoimmunity with intense autoantibody production and dysregulated T follicular helper and B cell responses. These results identify a privileged role of Treg cell-derived TGF-ß1 in regulating allergy and autoimmunity at distinct checkpoints in a Tgfb1 gene dose- and microbiota-dependent manner.

The Ebola virus VP40 matrix layer undergoes endosomal disassembly essential for membrane fusion.

Ebola viruses (EBOVs) assemble into filamentous virions, whose shape and stability are determined by the matrix viral protein 40 (VP40). Virus entry into host cells occurs via membrane fusion in late endosomes; however, the mechanism of how the remarkably long virions undergo uncoating, including virion disassembly and nucleocapsid release into the cytosol, remains unknown. Here, we investigate the structural architecture of EBOVs entering host cells and discover that the VP40 matrix disassembles prior to membrane fusion. We reveal that VP40 disassembly is caused by the weakening of VP40-lipid interactions driven by low endosomal pH that equilibrates passively across the viral envelope without a dedicated ion channel. We further show that viral membrane fusion depends on VP40 matrix integrity, and its disassembly reduces the energy barrier for fusion stalk formation. Thus, pH-driven structural remodeling of the VP40 matrix acts as a molecular switch coupling viral matrix uncoating to membrane fusion during EBOV entry.

ProDOL: a general method to determine the degree of labeling for staining optimization and molecular counting.

Determining the label to target ratio, also known as the degree of labeling (DOL), is crucial for quantitative fluorescence microscopy and a high DOL with minimal unspecific labeling is beneficial for fluorescence microscopy in general. Yet robust, versatile and easy-to-use tools for measuring cell-specific labeling efficiencies are not available. Here we present a DOL determination technique named protein-tag DOL (ProDOL), which enables fast quantification and optimization of protein-tag labeling. With ProDOL various factors affecting labeling efficiency, including substrate type, incubation time and concentration, as well as sample fixation and cell type can be easily assessed. We applied ProDOL to investigate how human immunodeficiency virus-1 pathogenesis factor Nef modulates CD4 T cell activation measuring total and activated copy numbers of the adapter protein SLP-76 in signaling microclusters. ProDOL proved to be a versatile and robust tool for labeling calibration, enabling determination of labeling efficiencies, optimization of strategies and quantification of protein stoichiometry.

Exploring in-plane interactions beside an adsorbed molecule with lateral force microscopy.

Atomic force microscopy with a CO-functionalized tip can be used to directly image the internal structure of a planar molecule and to characterize chemical bonds. However, hydrogen atoms usually cannot be directly observed due to their small size. At the same time, these atoms are highly important, since they can direct on-surface chemical reactions. Measuring in-plane interactions at the sides of PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) molecules with lateral force microscopy allowed us to directly identify hydrogen atoms via their repulsive signature, which we confirmed with a model incorporating radially symmetric atomic interactions. Additional features were observed in the force data and could not be explained by H-bonding of the CO tip with the PTCDA sides. Instead, they are caused by electrostatic interaction of the large dipole of the metal apex, which we verified with density functional theory. This calculation allowed us to estimate the strength of the dipole at the metal tip apex. To further confirm that this dipole generally affects measurements on weakly polarized systems, we investigated the archetypical surface adsorbate of a single CO molecule. We determined the radially symmetric atomic interaction to be valid over a large solid angle of 5.4 sr, corresponding to 82°. We therefore find that in both the PTCDA and CO systems, the underlying interaction preventing direct observations of H-bonding and causing a collapse of the radially symmetric model is the dipole at the metal apex, which plays a significant role when approaching closer than standard imaging heights.

Direct and indirect effects of CYTOR lncRNA regulate HIV gene expression.

The implementation of antiretroviral therapy (ART) has effectively restricted the transmission of Human Immunodeficiency Virus (HIV) and improved overall clinical outcomes. However, a complete cure for HIV remains out of reach, as the virus persists in a stable pool of infected cell reservoir that is resistant to therapy and thus a main barrier towards complete elimination of viral infection. While the mechanisms by which host proteins govern viral gene expression and latency are well-studied, the emerging regulatory functions of non-coding RNAs (ncRNA) in the context of T cell activation, HIV gene expression and viral latency have not yet been thoroughly explored. Here, we report the identification of the Cytoskeleton Regulator (CYTOR) long non-coding RNA (lncRNA) as an activator of HIV gene expression that is upregulated following T cell stimulation. Functional studies show that CYTOR suppresses viral latency by directly binding to the HIV promoter and associating with the cellular positive transcription elongation factor (P-TEFb) to activate viral gene expression. CYTOR also plays a global role in regulating cellular gene expression, including those involved in controlling actin dynamics. Depletion of CYTOR expression reduces cytoplasmic actin polymerization in response to T cell activation. In addition, treating HIV-infected cells with pharmacological inhibitors of actin polymerization reduces HIV gene expression. We conclude that both direct and indirect effects of CYTOR regulate HIV gene expression.

Bacterial RNA sensing by TLR8 requires RNase 6 processing and is inhibited by RNA 2'O-methylation.

TLR8 senses single-stranded RNA (ssRNA) fragments, processed via cleavage by ribonuclease (RNase) T2 and RNase A family members. Processing by these RNases releases uridines and purine-terminated residues resulting in TLR8 activation. Monocytes show high expression of RNase 6, yet this RNase has not been analyzed for its physiological contribution to the recognition of bacterial RNA by TLR8. Here, we show a role for RNase 6 in TLR8 activation. BLaER1 cells, transdifferentiated into monocyte-like cells, as well as primary monocytes deficient for RNASE6 show a dampened TLR8-dependent response upon stimulation with isolated bacterial RNA (bRNA) and also upon infection with live bacteria. Pretreatment of bacterial RNA with recombinant RNase 6 generates fragments that induce TLR8 stimulation in RNase 6 knockout cells. 2'O-RNA methyl modification, when introduced at the first uridine in the UA dinucleotide, impairs processing by RNase 6 and dampens TLR8 stimulation. In summary, our data show that RNase 6 processes bacterial RNA and generates uridine-terminated breakdown products that activate TLR8.

Rapid, efficient and activation-neutral gene editing of polyclonal primary human resting CD4+ T cells allows complex functional analyses.

CD4+ T cells are central mediators of adaptive and innate immune responses and constitute a major reservoir for human immunodeficiency virus (HIV) in vivo. Detailed investigations of resting human CD4+ T cells have been precluded by the absence of efficient approaches for genetic manipulation limiting our understanding of HIV replication and restricting efforts to find a cure. Here we report a method for rapid, efficient, activation-neutral gene editing of resting, polyclonal human CD4+ T cells using optimized cell cultivation and nucleofection conditions of Cas9-guide RNA ribonucleoprotein complexes. Up to six genes, including HIV dependency and restriction factors, were knocked out individually or simultaneously and functionally characterized. Moreover, we demonstrate the knock in of double-stranded DNA donor templates into different endogenous loci, enabling the study of the physiological interplay of cellular and viral components at single-cell resolution. Together, this technique allows improved molecular and functional characterizations of HIV biology and general immune functions in resting CD4+ T cells.

Targeted multicolor in vivo imaging over 1,000 nm enabled by nonamethine cyanines.

Recent progress has shown that using wavelengths between 1,000 and 2,000 nm, referred to as the shortwave-infrared or near-infrared (NIR)-II range, can enable high-resolution in vivo imaging at depths not possible with conventional optical wavelengths. However, few bioconjugatable probes of the type that have proven invaluable for multiplexed imaging in the visible and NIR range are available for imaging these wavelengths. Using rational design, we have generated persulfonated indocyanine dyes with absorbance maxima at 872 and 1,072 nm through catechol-ring and aryl-ring fusion, respectively, onto the nonamethine scaffold. Multiplexed two-color and three-color in vivo imaging using monoclonal antibody and dextran conjugates in several tumor models illustrate the benefits of concurrent labeling of the tumor and healthy surrounding tissue and lymphatics. These efforts are enabled by complementary advances in a custom-built NIR/shortwave-infrared imaging setup and software package for multicolor real-time imaging.

Tissue-like environments shape functional interactions of HIV-1 with immature dendritic cells.

Immature dendritic cells (iDCs) migrate in microenvironments with distinct cell and extracellular matrix densities in vivo and contribute to HIV-1 dissemination and mounting of antiviral immune responses. Here, we find that, compared to standard 2D suspension cultures, 3D collagen as tissue-like environment alters iDC properties and their response to HIV-1 infection. iDCs adopt an elongated morphology with increased deformability in 3D collagen at unaltered activation, differentiation, cytokine secretion, or responsiveness to LPS. While 3D collagen reduces HIV-1 particle uptake by iDCs, fusion efficiency is increased to elevate productive infection rates due to elevated cell surface exposure of the HIV-1-binding receptor DC-SIGN. In contrast, 3D collagen reduces HIV transfer to CD4 T cells from iDCs. iDC adaptations to 3D collagen include increased pro-inflammatory cytokine production and reduced antiviral gene expression in response to HIV-1 infection. Adhesion to a 2D collagen matrix is sufficient to increase iDC deformability, DC-SIGN exposure, and permissivity to HIV-1 infection. Thus, mechano-physical cues of 2D and 3D tissue-like collagen environments regulate iDC function and shape divergent roles during HIV-1 infection.

Landscape-scale concordance between local ecological knowledge for tropical wild species and remote sensing of land cover.

Monitoring the status of species is crucial for biodiversity conservation and sustainable resource management in tropical forests, but conventional in situ monitoring methods are impractical over large scales. Scientists have resorted to two potentially complementary approaches: local ecological knowledge (LEK) and remote sensing. To gauge the potential of combining LEK and remote sensing for assessing species status at landscape scales, a large-scale assessment of the reliability of both measures is critical but hampered by the lack of ground-level data. We conducted a landscape-scale assessment of LEK and remote sensing, using a survey of over 900 communities (a near census in our study area) and nearly 4,000 households in 235 randomly selected communities in the Peruvian Amazon-the largest LEK survey as yet undertaken in tropical forests. The survey collected LEK data on the presence of 20 indicator species from both community leaders/elders and randomly sampled households. We assessed LEK and remotely sensed land cover-forest cover and nonmain channel open water-as proxies for species habitat, across species (game, fish, and timber), over time (current and historical), and by indigeneity (Indigenous peoples and mestizos). Overall, LEK and remotely sensed land cover corroborate each other well. Concordance is highest for the current status of game species reported by sampled households, as is the concordance of historical LEK from Indigenous community leaders/elders. The results point to the promise of combining LEK and remote sensing in monitoring the status of species in data-poor tropical forests.

Magnitude of Type I Interferon Responses by Plasmacytoid Dendritic Cells After TLR7 Stimulation Is Associated With Human Immunodeficiency Virus Type 1 (HIV-1) Reservoir Sizes in Cisgender Women With HIV-1 on Antiretroviral Therapy.

Human immunodeficiency virus type 1 (HIV-1) disease manifestations differ between cisgender women and men, including better control of viral replication during primary infection and less frequent residual HIV-1 replication on antiretroviral therapy (ART) in cisgender women with HIV-1 (WWH). Investigating plasmacytoid dendritic cell (pDC) functions and HIV-1 reservoir sizes in 20 WWH on stable ART, we observed inverse correlations between interferon-α and tumor necrosis factor responses of pDCs to Toll-like receptor 7/8 stimulation and intact/total proviral HIV-1 DNA levels. Additionally, ISG15 mRNA levels in peripheral blood mononuclear cells correlated with cytokine responses of pDCs. These findings demonstrate an association between higher type I interferon responses and lower HIV-1 reservoir sizes in WWH on ART, warranting studies to identify the underlying mechanisms.

CARD8 inflammasome activation triggers pyroptosis in human T cells.

Inflammasomes execute a unique type of cell death known as pyroptosis. Mostly characterized in myeloid cells, caspase-1 activation downstream of an inflammasome sensor results in the cleavage and activation of gasdermin D (GSDMD), which then forms a lytic pore in the plasma membrane. Recently, CARD8 was identified as a novel inflammasome sensor that triggers pyroptosis in myeloid leukemia cells upon inhibition of dipeptidyl-peptidases (DPP). Here, we show that blocking DPPs using Val-boroPro triggers a lytic form of cell death in primary human CD4 and CD8 T cells, while other prototypical inflammasome stimuli were not active. This cell death displays morphological and biochemical hallmarks of pyroptosis. By genetically dissecting candidate components in primary T cells, we identify this response to be dependent on the CARD8-caspase-1-GSDMD axis. Moreover, DPP9 constitutes the relevant DPP restraining CARD8 activation. Interestingly, this CARD8-induced pyroptosis pathway can only be engaged in resting, but not in activated T cells. Altogether, these results broaden the relevance of inflammasome signaling and associated pyroptotic cell death to T cells, central players of the adaptive immune system.

HIV-1 infection of CD4 T cells impairs antigen-specific B cell function.

Failures to produce neutralizing antibodies upon HIV-1 infection result in part from B-cell dysfunction due to unspecific B-cell activation. How HIV-1 affects antigen-specific B-cell functions remains elusive. Using an adoptive transfer mouse model and ex vivo HIV infection of human tonsil tissue, we found that expression of the HIV-1 pathogenesis factor NEF in CD4 T cells undermines their helper function and impairs cognate B-cell functions including mounting of efficient specific IgG responses. NEF interfered with T cell help via a specific protein interaction motif that prevents polarized cytokine secretion at the T-cell-B-cell immune synapse. This interference reduced B-cell activation and proliferation and thus disrupted germinal center formation and affinity maturation. These results identify NEF as a key component for HIV-mediated dysfunction of antigen-specific B cells. Therapeutic targeting of the identified molecular surface in NEF will facilitate host control of HIV infection.

Beet curly top virus affects vector biology: the first transcriptome analysis of the beet leafhopper.

Curly top disease, caused by beet curly top virus (BCTV), is among the most serious viral diseases affecting sugar beets in western USA. The virus is exclusively transmitted by the beet leafhopper (BLH, Circulifer tenellus) in a circulative and non-propagative manner. Despite the growing knowledge on virus-vector interactions, our understanding of the molecular interactions between BCTV and BLH is hampered by limited information regarding the virus impact on the vector and the lack of genomic and transcriptomic resources for BLH. This study unveils the significant impact of BCTV on both the performance and transcriptome response of BLHs. Viruliferous BLHs had higher fecundity than non-viruliferous counterparts, which was evident by upregulation of differentially expressed transcripts (DETs) associated with development, viability and fertility of germline and embryos in viruliferous insects. Conversely, most DETs associated with muscle movement and locomotor activities were downregulated in viruliferous insects, implying potential behavioural modifications by BCTV. Additionally, a great proportion of DETs related to innate immunity and detoxification were upregulated in viruliferous insects. Viral infection also induced notable alterations in primary metabolisms, including energy metabolism, namely glucosidases, lipid digestion and transport, and protein degradation, along with other cellular functions, particularly in chromatin remodelling and DNA repair. This study represents the first comprehensive transcriptome analysis for BLH. The presented findings provide new insights into the multifaceted effects of viral infection on various biological processes in BLH, offering a foundation for future investigations into the complex virus-vector relationship and potential management strategies for curly top disease.

Zfp362 potentiates murine colonic inflammation by constraining Treg cell function rather than promoting Th17 cell differentiation.

Mucosal barrier integrity and pathogen clearance is a complex process influenced by both Th17 and Treg cells. Previously, we had described the DNA methylation profile of Th17 cells and identified Zinc finger protein (Zfp)362 to be uniquely demethylated. Here, we generated Zfp362-/- mice to unravel the role of Zfp362 for Th17 cell biology. Zfp362-/- mice appeared clinically normal, showed no phenotypic alterations in the T-cell compartment, and upon colonization with segmented filamentous bacteria, no effect of Zfp362 deficiency on Th17 cell differentiation was observed. By contrast, Zfp362 deletion resulted in increased frequencies of colonic Foxp3+ Treg cells and IL-10+ and RORγt+ Treg cell subsets in mesenteric lymph nodes. Adoptive transfer of naïve CD4+ T cells from Zfp362-/- mice into Rag2-/- mice resulted in a significantly lower weight loss when compared with controls receiving cells from Zfp362+/+ littermates. However, this attenuated weight loss did not correlate with alterations of Th17 cells but instead was associated with an increase of effector Treg cells in mesenteric lymph nodes. Together, these results suggest that Zfp362 plays an important role in promoting colonic inflammation; however, this function is derived from constraining the effector function of Treg cells rather than directly promoting Th17 cell differentiation.

Clinical and molecular epidemiology of enterovirus infections in cerebrospinal fluid samples, 2019-2023.

We performed a comparative, retrospective analysis (March 2019-April 2023) of children diagnosed with non-polio enterovirus (NPEV) central nervous system (CNS) infections (n = 47 vs. 129 contemporaneous controls without NPEV, all <18 years old), requiring cerebrospinal fluid (CSF) testing upon presentation to hospital. We found that showed that admissions decreased during pandemic restrictions (13% vs. controls 33%, p = 0.003). The median age of children with NPEV was 41 days (IQR: 18-72), most were male (n = 76, 59%) and were less likely to present with symptoms of irritability (11% vs. controls 26%, p = 0.04), but more likely to be febrile (93% vs. controls 73%, p = 0.007), have higher respiratory rates (mean 44 bpm, SD 11, vs. controls 36 bpm, SD 14, p = 0.001), higher heart rates (mean 171 bpm, SD 27 vs. controls 141 bpm, SD 36, p < 0.001), higher CSF protein (median 0.66 g/L, interquartile range [IQR] 0.46-1.01, vs. controls 0.53 mg/mL, IQR 0.28-0.89, p = 0.04), higher CSF white cell count (WCC) (median WCC 9.5×106/L, IQR 1-16 vs. controls 3.15×106/L, IQR 2.7-3.6, p < 0.001), but lower CSF glucose (median 2.8 mmol/L, IQR 2.4-3.1 vs. controls 3.1 mmol/L, IQR 2.7-3.6, p < 0.001). Phylogenetic analysis showed that these NPEVs originated from Europe (EV A71, CV B4, E21, E6, CV B3, CV B5, E7, E11, E18), North America (CV B4, E18), South America (E6), Middle East (CV B5), Africa (CV B5, E18), South Asia (E15), East/Southeast Asia (E25, CV A9, E7, E11, E18), and Australia (CV B5).

Prior exposure to a sensorimotor game in virtual reality does not enhance stress reactivity toward the OpenTSST VR.

Compared to the in-person Trier Social Stress Test (TSST), virtual reality (VR) variants reduce resource-intensity and improve standardization but induce stress with smaller effect sizes. However, higher cortisol reactivity is given for more immersive TSST-VRs. Immersivity depends on the VR-system, but perceived immersion may be targeted by exposure to, or interaction with the VR. We investigated whether stress reactivity towards the openly accessible OpenTSST VR can be enhanced by prior exposure to a sensorimotor game completed in VR as mediated by increased immersion. Therefore, N = 58 healthy participants underwent the OpenTSST VR or its inbuilt control condition (placebo TSST-VR, pTSST-VR). Beforehand, participants completed a sensorimotor game either in VR or in real life. Stress was measured by means of self-reports, salivary cortisol concentrations, and salivary alpha-amylase (sAA) activity. Perceived immersion was assessed with the Igroup Presence Questionnaire (IPQ). The TSST-VR-group showed higher subjective stress than the pTSST-VR-group. Even though area under the curve measures indicated significant differences in cortisol levels between TSST-VR and pTSST-VR, this effect was not replicated in omnibus-analyses. Likewise, sAA was not responsive to stress. Our data suggests the OpenTSST VR does not reliably trigger physiological stress reactivity. Likewise, participants playing the VR-game before exposure to the TSST-VR did not show enhanced stress reactivity. Importantly, playing the VR-game did not lead to increased immersion (indicated by the IPQ), either. The key question resulting from our study is which manipulation may be fruitful to obtain a comparable stress response toward the TSST-VR compared to the in-person TSST.