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Blocking pyrimidine de novo synthesis by inhibiting dihydroorotate dehydrogenase is used to treat autoimmunity and prevent expansion of rapidly dividing cell populations including activated T cells. Here we show memory T cell precursors are resistant to pyrimidine starvation. Although the treatment effectively blocked effector T cells, the number, function and transcriptional profile of memory T cells and their precursors were unaffected. This effect occurred in a narrow time window in the early T cell expansion phase when developing effector, but not memory precursor, T cells are vulnerable to pyrimidine starvation. This vulnerability stems from a higher proliferative rate of early effector T cells as well as lower pyrimidine synthesis capacity when compared with memory precursors. This differential sensitivity is a drug-targetable checkpoint that efficiently diminishes effector T cells without affecting the memory compartment. This cell fate checkpoint might therefore lead to new methods to safely manipulate effector T cell responses.

The landscape and function of the immune infiltrate of intrahepatic cholangiocarcinoma (iCCA), a rare, yet aggressive tumor of the biliary tract, remains poorly characterized, limiting development of successful immunotherapies. Herein, we aimed to define the molecular characteristics of tumor-infiltrating leukocytes with a special focus on CD4+ regulatory T cells (Tregs).We used high-dimensional single-cell technologies to characterize the T-cell and myeloid compartments of iCCA tissues, comparing these with their tumor-free peritumoral and circulating counterparts. We further used genomics and cellular assays to define the iCCA-specific role of a novel transcription factor, mesenchyme homeobox 1 (MEOX1), in Treg biology.We found poor infiltration of putative tumor-specific CD39+ CD8+ T cells accompanied by abundant infiltration of hyperactivated CD4+ Tregs. Single-cell RNA-sequencing identified an altered network of transcription factors in iCCA-infiltrating compared to peritumoral T cells, suggesting reduced effector functions by tumor-infiltrating CD8+ T cells and enhanced immunosuppression by CD4+ Tregs. Specifically, we found that expression of MEOX1 was highly enriched in tumor-infiltrating Tregs, and demonstrated that MEOX1 overexpression is sufficient to reprogram circulating Tregs to acquire the transcriptional and epigenetic landscape of tumor-infiltrating Tregs. Accordingly, enrichment of the MEOX1-dependent gene program in Tregs was strongly associated with poor prognosis in a large cohort of patients with iCCA.We observed abundant infiltration of hyperactivated CD4+ Tregs in iCCA tumors along with reduced CD8+ T-cell effector functions. Interfering with hyperactivated Tregs should be explored as an approach to enhance antitumor immunity in iCCA.Immune cells have the potential to slow or halt the progression of tumors. However, some tumors, such as intrahepatic cholangiocarcinoma, are associated with very limited immune responses (and infiltration of cancer-targeting immune cells). Herein, we show that a specific population of regulatory T cells (a type of immune cell that actually suppresses the immune response) are hyperactivated in intrahepatic cholangiocarcinoma. Targeting these cells could enable cancer-targeting immune cells to act more effectively and should be looked at as a potential therapeutic approach to this aggressive cancer type.

TDCare hematopoietic cells that combine dendritic cell (DC) and conventional T cell markers and functional properties. They were identified in secondary lymphoid organs (SLOs) of naïve mice as cells expressing CD11c, major histocompatibility molecule (MHC)-II, and the T cell receptor (TCR) β chain. Despite thorough characterization as to their potential functional properties, a physiological role for TDCremains to be determined. Unfortunately, using CD11c as a marker for TDChas the caveat of its upregulation on different cells, including T cells, upon activation. Therefore, a more specific marker is needed to further investigate TDCfunctions in peripheral organs in different pathological settings. Here we took advantage of Zbtb46-GFP reporter mice to explore the frequency and localization of TDCin peripheral tissues at steady state and upon viral infection. RNA sequencing analysis confirmed that TDCidentified with this reporter model have a gene signature that is distinct from conventional T cells and DC. In addition, frequency and total numbers of TDCin the SLOs recapitulated those found using CD11c as a marker. This reporter model allowed for identification of TDCin situ not only in SLOs but also in the liver and lung of naïve mice. Interestingly, we found that TDCnumbers in the SLOs increased upon viral infection, suggesting that TDCmight play a role during viral infections. In conclusion, we propose a visualization strategy that might shed light on the physiological role of TDCin several pathological contexts, including infection and cancer.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the RNA virus responsible for the coronavirus disease 2019 (COVID-19) pandemic. Although SARS-CoV-2 was reported to alter several cellular pathways, its impact on DNA integrity and the mechanisms involved remain unknown. Here we show that SARS-CoV-2 causes DNA damage and elicits an altered DNA damage response. Mechanistically, SARS-CoV-2 proteins ORF6 and NSP13 cause degradation of the DNA damage response kinase CHK1 through proteasome and autophagy, respectively. CHK1 loss leads to deoxynucleoside triphosphate (dNTP) shortage, causing impaired S-phase progression, DNA damage, pro-inflammatory pathways activation and cellular senescence. Supplementation of deoxynucleosides reduces that. Furthermore, SARS-CoV-2 N-protein impairs 53BP1 focal recruitment by interfering with damage-induced long non-coding RNAs, thus reducing DNA repair. Key observations are recapitulated in SARS-CoV-2-infected mice and patients with COVID-19. We propose that SARS-CoV-2, by boosting ribonucleoside triphosphate levels to promote its replication at the expense of dNTPs and by hijacking damage-induced long non-coding RNAs’ biology, threatens genome integrity and causes altered DNA damage response activation, induction of inflammation and cellular senescence.

Mucosal vaccination is regarded as a promising alternative to classical, intramuscular vaccine delivery. However, only a limited number of vaccines have been licensed for mucosal administration in humans. Here we propose Leishmania tarentolae, a protozoan parasite, as a potential antigen vehicle for mucosal vaccination, for administration via the rectal or oral routes. To test this hypothesis, we exploited L. tarentolae for the production and delivery of SARS-CoV-2 antigens. Two antigens were assayed in BALB/c mice: Lt-spike, a L. tarentolae clone engineered for the surface expression of the SARS-CoV-2 spike protein; RBD-SD1, a purified portion of the spike protein, produced by another engineered clone of the protozoon. Immune response parameters were then determined at different time points. Both antigens, administered either separately or in combination (Lt-spike + RBD-SD1, hereafter LeCoVax-2), determined significant IgG seroconversion and production of neutralizing antibodies after subcutaneous administration, but only in the presence of adjuvants. After rectal administration, the purified RBD-SD1 antigen did not induce any detectable immune response, in comparison with the intense response observed after administration of LeCoVax-2 or Lt-spike alone. In rectal administration, LeCoVax-2 was also effective when administered without adjuvant. Our results show that L. tarentolae is an efficient and safe scaffold for production and delivery of viral antigens, to be used as vaccines. In addition, rectal vaccination experiments prove that L. tarentolae is suitable as a vaccine vehicle and adjuvant for enteral vaccination. Finally, the combined preparation LeCoVax-2 can be considered as a promising candidate vaccine against SARS-CoV-2, worthy of further investigation.

Alongside vaccines, antiviral drugs are becoming an integral part of our response to the SARS-CoV-2 pandemic. Nirmatrelvir – an orally available inhibitor of the 3-chymotrypsin-like cysteine protease – has been shown to reduce the risk of progression to severe COVID-19. However, the impact of nirmatrelvir treatment on the development of SARS-CoV-2-specific adaptive immune responses is unknown. Here, by using a mouse model of SARS-CoV-2 infection, we show that nirmatrelvir administration early after infection blunts the development of SARS-CoV-2-specific antibody and T cell responses. Accordingly, upon secondary challenge, nirmatrelvir-treated mice recruited significantly fewer memory T and B cells to the infected lungs and to mediastinal lymph nodes, respectively. Together, the data highlight a potential negative impact of nirmatrelvir treatment with important implications for clinical management and might help explain the virological and/or symptomatic relapse after treatment completion reported in some individuals.

Protection from viral infections depends on immunoglobulin isotype switching, which endows antibodies with effector functions. Here, we found that the protein kinase DYRK1A is essential for B cell-mediated protection from viral infection and effective vaccination through regulation of class switch recombination (CSR). Dyrk1a-deficient B cells were impaired in CSR activity in vivo and in vitro. Phosphoproteomic screens and kinase-activity assays identified MSH6, a DNA mismatch repair protein, as a direct substrate for DYRK1A, and deletion of a single phosphorylation site impaired CSR. After CSR and germinal center seeding, DYRK1A was required for proper clonal expansion of antigen-specific B cells through attenuation of proliferation. These findings reveal DYRK1A-mediated biological mechanisms of B cell immune responses that may be used for manipulation in antibody-mediated autoimmunity.

Hepatitis B virus (HBV) is a non-cytopathic, hepatotropic virus with the potential to cause a persistent infection, ultimately leading to cirrhosis and hepatocellular carcinoma. Over the past four decades, the basic principles of HBV gene expression and replication as well as the viral and host determinants governing infection outcome have been largely uncovered. Whereas HBV appears to induce little or no innate immune activation, the adaptive immune response mediates both viral clearance as well as liver disease. Here, we review our current knowledge on the immunobiology and pathogenesis of HBV infection, focusing in particular on the role of CD8+ T cells and on several recent breakthroughs that challenge current dogmas. For example, we now trust that HBV integration into the host genome often serves as a relevant source of hepatitis B surface antigen (HBsAg) expression during chronic infection, possibly triggering dysfunctional T cell responses and favouring detrimental immunopathology. Further, the unique haemodynamics and anatomy of the liver — and the changes they frequently endure during disease progression to liver fibrosis and cirrhosis — profoundly influence T cell priming, differentiation and function. We also discuss why therapeutic approaches that limit the intrahepatic inflammatory processes triggered by HBV-specific T cells might be surprisingly beneficial for patients with chronic infection.

T follicular helper (Tfh) cells are essential for the development of germinal center B cells and high-affinity antibody producing B-cells in human and mice. Here, we identify the guanine nucleotide exchange factor (GEF) Rin-like (Rinl) as a negative regulator of Tfh generation. Loss of Rinl leads to an increase of Tfh in aging, uponin vivoimmunization and acute LCMV Armstrong infection in mice, and in human CD4+T cellin vitrocultures. Further, adoptive transfer experiments using WT and Rinl-KO naïve CD4+T cells unraveled T cell-intrinsic functions of Rinl. Mechanistically, Rinl regulates CD28 internalization and signaling, thereby shaping CD4+T cell activation and differentiation. Thus, our results identify the GEF Rinl as a negative regulator of global Tfh differentiation in an immunological context and species-independent manner, and furthermore connect Rinl with CD28 internalization and signaling pathways in CD4+T cells, demonstrating for the first-time the importance of endocytic processes for Tfh differentiation.HighlightsRinl-KO CD4+T cells show increased Tfh differentiation in a context independent mannerThe regulation of Tfh differentiation is T cell-intrinsicRinl controls CD28 endocytosis and shapes Tfh-specific CD28 signal transductionHuman Tfh differentiation is regulated by Rinl

The gastrointestinal (GI) tract constitutes an essential barrier against ingested microbes, including potential pathogens. Although immune reactions are well studied in the lower GI tract, it remains unclear how adaptive immune responses are initiated during microbial challenge of the oral mucosa (OM), the primary site of microbial encounter in the upper GI tract. Here, we identify mandibular lymph nodes (mandLNs) as sentinel lymphoid organs that intercept ingestedListeria monocytogenes(Lm). Oral Lm uptake led to local activation and release of antigen-specific CD8+T cells that constituted most of the early circulating effector T cell (TEFF) pool. MandLN-primed TEFFdisseminated to lymphoid organs, lung, and OM and contributed substantially to rapid elimination of target cells. In contrast to CD8+TEFFgenerated in mesenteric LN (MLN) during intragastric infection, mandLN-primed TEFFlacked a gut-seeking phenotype, which correlated with low expression of enzymes required for gut-homing imprinting by mandLN stromal and dendritic cells. Accordingly, mandLN-primed TEFFdecreased Lm burden in spleen but not MLN after intestinal infection. Our findings extend the concept of regional specialization of immune responses along the length of the GI tract, with CD8+TEFFgenerated in the upper GI tract displaying homing profiles that differ from those imprinted by lymphoid tissue of the lower GI tract.

Chronic hepatitis B (CHB) is a major worldwide public health problem and novel anti-HBV therapies preventing liver disease progression to cirrhosis and hepatocellular carcinoma are urgently needed. Over the last several years, capsid assembly modulators (CAM) have emerged as clinically effective anti-HBV agents which can inhibit HBV replication in CHB patients. As part of a drug discovery program aimed at obtaining novel CAM endowed with high in vitro and in vivo antiviral activity, we identified a novel series of sulfamoylbenzamide (SBA) derivatives. Compound 10, one of the most in vitro potent SBA-derived CAM discovered to date, showed excellent pharmacokinetics in mice suitable for oral dosing. When studied in a transgenic mouse model of hepatic HBV replication, it was considerably more potent than NVR 3-778, the first sulfamoylbenzamide (SBA) CAM that entered clinical trials for CHB, at reducing viral replication in a dose-dependent fashion. We present herein the discovery process, the SAR analysis and the pre-clinical profile of this novel SBA CAM.

Platelet homeostasis is essential for vascular integrity and immune defense. While the process of platelet formation by fragmenting megakaryocytes (thrombopoiesis) has been extensively studied, the cellular and molecular mechanisms required to constantly replenish the pool of megakaryocytes by their progenitor cells (megakaryopoiesis) remains unclear. Here we use intravital 2 photon microscopy to track individual megakaryopoiesis over days. We identify plasmacytoid dendritic cells (pDCs) as crucial bone marrow niche cells that regulate megakaryopoiesis. pDCs monitor the bone marrow for platelet-producing megakaryocytes and deliver IFN-α to the megakaryocytic niche to trigger local on-demand proliferation of megakaryocyte progenitors. This fine-tuned coordination between thrombopoiesis and megakaryopoiesis is crucial for megakaryocyte and platelet homeostasis in steady state and stress. However, uncontrolled pDC function within the megakaryocytic niche is detrimental. Accordingly, we show that pDCs activated by SARS-CoV2 drive inappropriate megakaryopoiesis associated with thrombotic complications. Together, we uncover a hitherto unknown megakaryocytic bone marrow niche maintained by the constitutive delivery of pDC-derived IFN-α.

Comment in: DePICting T cell-APC crosstalk in cancer. Zhang T, Dong C. Nat Cancer. 2022 Mar;3(3):265-267. doi: 10.1038/s43018-022-00345-6. PMID: 35352059 No abstract available.; International audience; Despite their key regulatory role and therapeutic potency, the molecular signatures of interactions between T cells and antigen-presenting myeloid cells within the tumor microenvironment remain poorly characterized. Here, we systematically characterize these interactions using RNA sequencing of physically interacting cells (PIC-seq) and find that CD4+PD-1+CXCL13+ T cells are a major interacting hub with antigen-presenting cells in the tumor microenvironment of human non-small cell lung carcinoma. We define this clonally expanded, tumor-specific and conserved T-cell subset as T-helper tumor (Tht) cells. Reconstitution of Tht cells in vitro and in an ovalbumin-specific αβ TCR CD4+ T-cell mouse model, shows that the Tht program is primed in tumor-draining lymph nodes by dendritic cells presenting tumor antigens, and that their function is important for harnessing the antitumor response of anti-PD-1 treatment. Our molecular and functional findings support the modulation of Tht-dendritic cell interaction checkpoints as a major interventional strategy in immunotherapy.

Group 1 innate lymphoid cells (ILCs), which comprise both natural killer (NK) cells and ILC1s, are important innate effectors that can also positively and negatively influence adaptive immune responses. The latter function is generally ascribed to the ability of NK cells to recognize and kill activated T cells. Here, we used multiphoton intravital microscopy in mouse models of hepatitis B to study the intrahepatic behavior of group 1 ILCs and their cross-talk with hepatitis B virus (HBV)–specific CD8+T cells. We found that hepatocellular antigen recognition by effector CD8+T cells triggered a prominent increase in the number of hepatic NK cells and ILC1s. Group 1 ILCs colocalized and engaged in prolonged interactions with effector CD8+T cells undergoing hepatocellular antigen recognition; however, they did not induce T cell apoptosis. Rather, group 1 ILCs constrained CD8+T cell proliferation by controlling local interleukin-2 (IL-2) availability. Accordingly, group 1 ILC depletion, or genetic removal of their IL-2 receptor a chain, considerably increased the number of intrahepatic HBV-specific effector CD8+T cells and the attendant immunopathology. Together, these results reveal a role for group 1 ILCs in controlling T cell–mediated liver immunopathology by limiting local IL-2 concentration and have implications for the treatment of chronic HBV infection.

Bleeding correlates with disease severity in viral hemorrhagic fevers. We found that the increase in type I interferon (IFN-I) in mice caused by infection with the Armstrong strain of lymphocytic choriomeningitis virus (LCMV; an arenavirus) reduced the megakaryocytic expression of genes encoding enzymes involved in lipid biosynthesis (cyclooxygenase 1andthromboxane A synthase 1) and a thrombopoietic transcription factor (Nf-e2). The decreased expression of these genes was associated with reduced numbers of circulating platelets and defects in the arachidonic acid synthetic pathway, thereby suppressing serotonin release from δ-granules in platelets. Bleeding resulted when severe thrombocytopenia and altered platelet function reduced the amount of platelet-derived serotonin below a critical threshold. Bleeding was facilitated by the absence of the activity of the kinase Lyn or the administration of aspirin, an inhibitor of arachidonic acid synthesis. Mouse platelets were not directly affected by IFN-I because they lack the receptor for the cytokine (IFNAR1), suggesting that transfusion of normal platelets into LCMV-infected mice could increase the amount of platelet-released serotonin and help to control hemorrhage.

The antiviral immune response to SARS-CoV-2 infection can limit viral spread and prevent development of pneumonic COVID-19. However, the protective immunological response associated with successful viral containment in the upper airways remains unclear. Here, we combine a multi-omics approach with longitudinal sampling to reveal temporally resolved protective immune signatures in non-pneumonic and ambulatory SARS-CoV-2 infected patients and associate specific immune trajectories with upper airway viral containment. We see a distinct systemic rather than local immune state associated with viral containment, characterized by interferon stimulated gene (ISG) upregulation across circulating immune cell subsets in non-pneumonic SARS-CoV2 infection. We report reduced cytotoxic potential of Natural Killer (NK) and T cells, and an immune-modulatory monocyte phenotype associated with protective immunity in COVID-19. Together, we show protective immune trajectories in SARS-CoV2 infection, which have important implications for patient prognosis and the development of immunomodulatory therapies.

International audience; When helper T (TH) cell polarization was initially described three decades ago, the TH cell universe grew dramatically. New subsets were described based on their expression of few specific cytokines. Beyond TH1 and TH2 cells, this led to the coining of various TH17 and regulatory (Treg) cell subsets as well as TH22, TH25, follicular helper (TFH), TH3, TH5 and TH9 cells. High-dimensional single-cell analysis revealed that a categorization of TH cells into a single-cytokine-based nomenclature fails to capture the complexity and diversity of TH cells. Similar to the simple nomenclature used to describe innate lymphoid cells (ILCs), we propose that TH cell polarization should be categorized in terms of the help they provide to phagocytes (type 1), to B cells, eosinophils and mast cells (type 2) and to non-immune tissue cells, including the stroma and epithelium (type 3). Studying TH cells based on their helper function and the cells they help, rather than phenotypic features such as individual analyzed cytokines or transcription factors, better captures TH cell plasticity and conversion as well as the breadth of immune responses in vivo.

Tissue macrophages are immune cells whose phenotypes and functions are dictated by origin and niches. However, tissues are complex environments, and macrophage heterogeneity within the same organ has been overlooked so far. Here, we used high-dimensional approaches to characterize macrophage populations in the murine liver. We identified two distinct populations among embryonically derived Kupffer cells (KCs) sharing a core signature while differentially expressing numerous genes and proteins: a major CD206loESAM– population (KC1) and a minor CD206hiESAM+ population (KC2). KC2 expressed genes involved in metabolic processes, including fatty acid metabolism both in steady-state and in diet-induced obesity and hepatic steatosis. Functional characterization by depletion of KC2 or targeted silencing of the fatty acid transporter Cd36 highlighted a crucial contribution of KC2 in the liver oxidative stress associated with obesity. In summary, our study reveals that KCs are more heterogeneous than anticipated, notably describing a subpopulation wired with metabolic functions.

The development of a tractable small animal model faithfully reproducing human COVID-19 pathogenesis would arguably meet a pressing need in biomedical research. Thus far, most investigators have used transgenic mice expressing the human ACE2 in epithelial cells (K18-hACE2 transgenic mice) that are intranasally instilled with a liquid SARS-CoV-2 suspension under deep anesthesia. Unfortunately, this experimental approach results in disproportionate high CNS infection leading to fatal encephalitis, which is rarely observed in humans and severely limits this model’s usefulness. Here, we describe the use of an inhalation tower system that allows exposure of unanesthetized mice to aerosolized virus under controlled conditions. Aerosol exposure of K18-hACE2 transgenic mice to SARS-CoV-2 resulted in robust viral replication in the respiratory tract, anosmia, and airway obstruction, but did not lead to fatal viral neuroinvasion. When compared to intranasal inoculation, aerosol infection resulted in a more pronounced lung pathology including increased immune infiltration, fibrin deposition and a transcriptional signature comparable to that observed in SARS-CoV-2- infected patients. This model may prove useful for studies of viral transmission, disease pathogenesis (including long-term consequences of SARS-CoV-2 infection) and therapeutic interventions.

The vaccination campaign against SARS-CoV-2 relies on the world-wide availability of effective vaccines, with a potential need of 20 billion vaccine doses to fully vaccinate the world population. To reach this goal, the manufacturing and logistic processes should be affordable to all countries, irrespectively of economical and climatic conditions.Outer membrane vesicles (OMVs) are bacterial-derived vesicles that can be engineered to incorporate heterologous antigens. Given the inherent adjuvanticity, such modified OMVs can be used as vaccine to induce potent immune responses against the associated protein. Here we show that OMVs engineered to incorporate peptides derived from the receptor binding motif (RBM) of the spike protein from SARS-CoV-2 elicit an effective immune response in immunized mice, resulting in the production of neutralizing antibodies. The immunity induced by the vaccine is sufficient to protect K18-hACE2 transgenic mice from intranasal challenge with SARS-CoV-2, preventing both virus replication in the lungs and the pathology associated with virus infection. Furthermore, we show that OMVs can be effectively decorated with RBM peptides derived from a different genetic variant of SARS-CoV-2, inducing a similarly potent neutralization activity in vaccinated mice. Altogether, given the convenience associated with ease of engineering, production and distribution, our results demonstrate that OMV-based SARS-CoV-2 vaccines can be a crucial addition to the vaccines currently available.

Key Points CXCR3 identifies human naive CD8+ T cells with biased effector potential. Human naive CD8+ T cell subsets are functionally and transcriptionally distinct. Effector potential correlates with the physicochemical attributes of expressed TCRs., In mice, the ability of naive T (TN) cells to mount an effector response correlates with TCR sensitivity for self-derived Ags, which can be quantified indirectly by measuring surface expression levels of CD5. Equivalent findings have not been reported previously in humans. We identified two discrete subsets of human CD8+ TN cells, defined by the absence or presence of the chemokine receptor CXCR3. The more abundant CXCR3+ TN cell subset displayed an effector-like transcriptional profile and expressed TCRs with physicochemical characteristics indicative of enhanced interactions with peptide–HLA class I Ags. Moreover, CXCR3+ TN cells frequently produced IL-2 and TNF in response to nonspecific activation directly ex vivo and differentiated readily into Ag-specific effector cells in vitro. Comparative analyses further revealed that human CXCR3+ TN cells were transcriptionally equivalent to murine CXCR3+ TN cells, which expressed high levels of CD5. These findings provide support for the notion that effector differentiation is shaped by heterogeneity in the preimmune repertoire of human CD8+ T cells.

Summary paragraphVaccines against SARS-CoV-2 are based on a range of novel vaccine platforms, with adenovirus-based approaches (like ChAdOx1 nCov-19) being one of them. Recently a rare and novel complication of SARS-CoV-2 targeted adenovirus vaccines has emerged: thrombosis with thrombocytopenia syndrome (TTS). TTS is characterized by low platelet counts, clot formation at unusual anatomic sites and platelet-activating PF4-polyanion antibodies reminiscent of heparin-induced thrombocytopenia. Here, we employ in vitro and in vivo models to characterize the possible mechanisms of this platelet-targeted autoimmunity. We show that intravenous but not intramuscular injection of ChAdOx1 nCov-19 triggers platelet-adenovirus aggregate formation and platelet activation. After intravenous injection, these aggregates are phagocytosed by macrophages in the spleen and platelet remnants are found in the marginal zone and follicles. This is followed by a pronounced B-cell response with the emergence of circulating antibodies binding to platelets. Our work contributes to the understanding of TTS and highlights accidental intravenous injection as potential mechanism for post-vaccination TTS. Hence, safe intramuscular injection, with aspiration prior to injection, could be a potential preventive measure when administering adenovirus-based vaccines.

The COVID-19 pandemic caused by the β-coronavirus SARS-CoV-2 has made the development of safe and effective vaccines a critical global priority. To date, four vaccines have already been approved by European and American authorities for preventing COVID-19 but the development of additional vaccine platforms with improved supply and logistics profiles remains a pressing need. Here we report the preclinical evaluation of a novel COVID-19 vaccine candidate based on the electroporation of engineered, synthetic cDNA encoding a viral antigen in the skeletal muscle, a technology previously utilized for cancer vaccines. We constructed a set of prototype DNA vaccines expressing various forms of the SARS-CoV-2 Spike (S) protein and assessed their immunogenicity in animal models. Among them, COVID-eVax – a DNA plasmid encoding a secreted monomeric form of SARS-CoV-2 S protein RBD – induced the most potent anti-SARS-CoV-2 neutralizing antibody responses (including against the current most common variants of concern) and a robust T cell response. Upon challenge with SARS-CoV-2, immunized K18-hACE2 transgenic mice showed reduced weight loss, improved pulmonary function and significantly lower viral replication in the lungs and brain. COVID-eVax conferred significant protection to ferrets upon SARS-CoV-2 challenge. In summary, this study identifies COVID-eVax as an ideal COVID-19 vaccine candidate suitable for clinical development. Accordingly, a combined phase I-II trial has recently started in Italy.

When helper T (T

Despite their key regulatory role and therapeutic potency, the molecular signatures of interactions between T cells and antigen-presenting myeloid cells within the tumor microenvironment remain poorly characterized. Here, we systematically characterize these interactions using RNA sequencing of physically interacting cells (PIC-seq) and find that CD4

Summary Here, we provide detailed protocols for the isolation of mouse Kupffer cells – the liver-resident macrophages – for phenotypic (e.g., via flow cytometry, mass cytometry, or RNA-sequencing) analyses or for functional experiments involving cell culture. The procedures presented can be adapted for the isolation of other hepatic cell populations. For complete details on the use and execution of this protocol, please refer to De Simone et al. (2021)., Graphical abstract, Highlights • Protocol for Kupffer cell (KC) isolation • Suitable for the simultaneous isolation of other hepatic cell populations • Isolated KCs are suitable for phenotypic and functional analyses • We provide critical tips for cell processing and FACS-based sorting, Here, we provide detailed protocols for the isolation of mouse Kupffer cells – the liver-resident macrophages – for phenotypic (e.g., via flow cytometry, mass cytometry or RNA-sequencing) analyses or for functional experiments involving cell culture. The procedures presented can be adapted for the isolation of other hepatic cell populations.