Scientific Resources

C-Type lectin receptor 5A (CLEC5A) is a spleen tyrosine kinase- (Syk-) coupled pattern recognition receptor expressed on myeloid cells and involved in the innate immune response to viral and bacterial infections. Activation of the CLEC5A receptor with pathogen-derived antigens leads to a secretion of proinflammatory mediators such as TNF-$\alpha$ and IL-6 that may provoke a systemic cytokine storm,and CLEC5A gene polymorphisms are associated with the severity of DV infection. In addition,the CLEC5A receptor was mentioned in the context of noninfectious disorders like chronic obstructive pulmonary disease (COPD) or arthritis. Altogether,CLEC5A may be considered as an innate immune checkpoint capable to amplify proinflammatory signals,and this way contributes to infection or to aseptic inflammation. In this study,we determined CLEC5A receptor expression on different macrophage subsets (in vitro and ex vivo) and the functional consequences of its activation in aseptic conditions. The CLEC5A surface expression appeared the highest on proinflammatory M1 macrophages while intermediate on tumor-associated phenotypes (M2c or TAM). In contrast,the CLEC5A expression on ex vivo-derived alveolar macrophages from healthy donors or macrophages from ovarian cancer patients was hardly detectable. Targeting CLEC5A on noninflammatory macrophages with an agonistic $\alpha$-CLEC5A antibody triggered a release of proinflammatory cytokines,resembling a response to dengue virus,and led to phenotypic changes in myeloid cells that may suggest their reprogramming towards a proinflammatory phenotype,e.g.,upregulation of CD80 and downregulation of CD163. Interestingly,the CLEC5A agonist upregulated immune-regulatory molecules like CD206,PD-L1,and cytokines like IL-10,macrophage-derived chemokine (MDC/CCL22),and thymus and activation chemokine (TARC/CCL17) which are associated with an anti-inflammatory or a protumorigenic macrophage phenotype. In the absence of concomitant pathogenic or endogenous danger signals,the CLEC5A receptor activation did not amplify an autologous T cell response,which may represent a protective innate mechanism to avoid an undesirable autoimmune adaptive response. View Publication

Allergic airway inflammation is a universal airway disease that is driven by hyperresponsiveness to inhaled allergens. Group 2 innate lymphoid cells (ILC2s) produce copious amounts of type 2 cytokines,which lead to allergic airway inflammation. Here,we discovered that both peripheral blood of human and mouse lung ILC2s express the endothelin-A receptor (ETAR),and the expression level of ETAR was dramatically induced upon interleukin-33 (IL-33) treatment. Subsequently,both preventive and therapeutic effects of BQ123,an ETAR antagonist,on allergic airway inflammation were observed,which were associated with decreased proliferation and type 2 cytokine productions by ILC2s. Furthermore,ILC2s from BQ123 treatment were found to be functionally impaired in response to an interleukin IL-33 challenged. And BQ123 treatment also affected the phosphorylation level of the extracellular signal-regulated kinase (ERK),as well as the level of GATA binding protein 3 (GATA3) in activated ILC2s. Interestingly,after BQ123 treatment,both mouse and human ILC2s in vitro exhibited decreased function and downregulation of ERK signaling and GATA3 stability. These observations imply that ETAR is an important regulator of ILC2 function and may be involved in ILC2-driven pulmonary inflammation. Therefore,blocking ETAR may be a promising therapeutic strategy for allergic airway inflammation. View Publication

Immunological non-responders (InRs) are HIV-infected individuals in whom the administration of combination antiretroviral therapy (cART),although successful in suppressing viral replication,cannot properly reconstitute patient circulating CD4+ T-cell number to immunocompetent levels. The causes for this immunological failure remain elusive,and no therapeutic strategy is available to restore a proper CD4+ T-cell immune response in these individuals. We have recently demonstrated that platelets harboring infectious HIV are a hallmark of InR,and we now report on a causal connection between HIV-containing platelets and T-cell dysfunctions. We show here that in vivo,platelet-T-cell conjugates are more frequent among CD4+ T cells in InRs displaying HIV-containing platelets (<350 CD4+ T cells/$\mu$l blood for >1 year) as compared with healthy donors or immunological responders (IRs; >350 CD4+ T cells/$\mu$l). This contact between platelet containing HIV and T cell in the conjugates is not infectious for CD4+ T cells,as coculture of platelets from InRs containing HIV with healthy donor CD4+ T cells fails to propagate infection to CD4+ T cells. In contrast,when macrophages are the target of platelets containing HIV from InRs,macrophages become infected. Differential transcriptomic analyses comparing InR and IR CD4+ T cells reveal an upregulation of genes involved in both aerobic and anaerobic glycolysis in CD4+ T cells from InR vs. IR individuals. Accordingly,InR platelets containing HIV induce a dysfunctional increase in glycolysis-mediated energy production in CD4+ T cells as compared with T cells cocultured with IR platelets devoid of virus. In contrast,macrophage metabolism is not affected by platelet contact. Altogether,this brief report demonstrates a direct causal link between presence of HIV in platelets and T-cell dysfunctions typical of InR,contributing to devise a platelet-targeted therapy for improving immune reconstitution in these individuals. View Publication

BACKGROUND With the rapid development of immune checkpoint inhibitors and neoantigen (NeoV)-based personalized tumor vaccines,tumor immunotherapy has shown promising therapeutic results. However,the limited efficacy of available tumor vaccines impedes the development of personalized tumor immunotherapy. In this study,we developed a novel tumor vaccine system and proposed combined therapeutic strategies for improving treatment effects. METHODS We developed a novel tumor vaccine system comprising a newly synthesized peptidic microarchitecture (PMA) with high assembly efficacy. The PMA-trapped neoantigen vaccine was developed to codeliver tumor neoantigen and the Toll-like receptor 9 agonist CpG (NeoV),abbreviated as PMA-NeoV. A microfluidic chip was used to produce PMA particles in a uniform and precise manner. Vaccine effectiveness was investigated both in vitro and in vivo. The combined immunotherapeutic effect of PMA-NeoV with anti-programmed cell death ligand 1 antibody (aPD-L1) or with the phosphatidylinositol 3?‘kinase $\gamma$ (PI3K$\gamma$) inhibitor IPI-549 was further tested in MC38 mouse tumor model. RESULTS PMA-NeoV not only promoted codelivery of the tumor vaccine but also potentiated vaccine immunogenicity. Moreover,compared with free NeoV,PMA-NeoV significantly increased the number of tumor-infiltrating lymphocytes,promoted the neoantigen-specific systemic immune response,and suppressed murine colon MC38 tumor growth. Furthermore,PMA-NeoV increased the expression of programmed cell death receptor-1 on T lymphocytes,and in combination with aPD-L1 eradicated seven of eight MC38 tumors by rescuing exhausted T lymphocytes. Moreover,we combined the PMA-NeoV with the IPI-549,a molecular switch that controls immune suppression,and found that this combination significantly suppressed tumor growth and eradicated five of eight inoculated tumors,by switching suppressive macrophages to their active state and activating T cells to prime a robust tumor immune microenvironment. CONCLUSIONS We developed a tumor vaccine delivery system and presented a promising personalized tumor vaccine-based therapeutic regimen in which a tumor vaccine delivery system is combined with an aPD-L1 or PI3K$\gamma$ inhibitor to improve tumor immunotherapy outcomes. View Publication

Immunosuppressive factors in the tumor microenvironment (TME) impair T cell function and limit the antitumor immune response. T cell surface receptors and surface proteins that influence interactions and function in the TME are proven targets for cancer immunotherapy. However,how the entire surface proteome remodels in primary human T cells in response to specific suppressive factors in the TME remains to be broadly and systematically characterized. Here,using a reductionist cell culture approach with primary human T cells and stable isotopic labeling with amino acids in cell culture-based quantitative cell surface capture glycoproteomics,we examined how two immunosuppressive TME factors,regulatory T cells (Tregs) and hypoxia,globally affect the activated CD8+ surface proteome (surfaceome). Surprisingly,coculturing primary CD8+ T cells with Tregs only modestly affected the CD8+ surfaceome but did partially reverse activation-induced surfaceomic changes. In contrast,hypoxia drastically altered the CD8+ surfaceome in a manner consistent with both metabolic reprogramming and induction of an immunosuppressed state. The CD4+ T cell surfaceome similarly responded to hypoxia,revealing a common hypoxia-induced surface receptor program. Our surfaceomics findings suggest that hypoxic environments create a challenge for T cell activation. These studies provide global insight into how Tregs and hypoxia remodel the T cell surfaceome and we believe represent a valuable resource to inform future therapeutic efforts to enhance T cell function. View Publication

Intrasynovial flexor tendon lacerations of the hand are clinically problematic,typically requiring operative repair and extensive rehabilitation. The small-molecule connective tissue growth factor (CTGF) mimics,oxotremorine M (Oxo-M) and 4-PPBP maleate (4-PPBP),have been shown to improve tendon healing in small animal models by stimulating the expansion and differentiation of perivascular CD146+ cells. To enhance intrasynovial flexor tendon healing,small-molecule CTGF mimics were delivered to repaired canine flexor tendons via porous sutures. In vitro studies demonstrated that Oxo-M and 4-PPBP retained their bioactivity and could be released from porous sutures in a sustained manner. However,in vivo delivery of the CTGF mimics did not improve intrasynovial tendon healing. Histologic analyses and expression of tenogenic,extracellular matrix,inflammation,and remodeling genes showed similar outcomes in treated and untreated repairs across two time points. Although in vitro experiments revealed that CTGF mimics stimulated robust responses in extrasynovial tendon cells,there was no response in intrasynovial tendon cells,explaining the lack of in vivo effects. The results of the current study indicate that therapeutic strategies for tendon repair must carefully consider the environment and cellular makeup of the particular tendon for improving the healing response. View Publication

BACKGROUND B1a and B1b lymphocytes produce IgM that inactivates oxidation-specific epitopes (IgMOSE) on LDL (low-density lipoprotein) and protects against atherosclerosis. Loss of ID3 (inhibitor of differentiation 3) in B cells selectively promotes B1b but not B1a cell numbers,leading to higher IgMOSE production and reduction in atherosclerotic plaque formation. Yet,the mechanism underlying this regulation remains unexplored. METHODS Bulk RNA sequencing was utilized to identify differentially expressed genes in B1a and B1b cells from Id3KO and Id3WT mice. CRISPR/Cas9 and lentiviral genome editing coupled with adoptive transfer were used to identify key Id3-dependent signaling pathways regulating B1b cell proliferation and the impact on atherosclerosis. Biospecimens from humans with advanced coronary artery disease imaging were analyzed to translate murine findings to human subjects with coronary artery disease. RESULTS Through RNA sequencing,P62 was found to be enriched in Id3KO B1b cells. Further in vitro characterization reveals a novel role for P62 in mediating BAFF (B-cell activating factor)-induced B1b cell proliferation through interacting with TRAF6 (tumor necrosis factor receptor 6) and activating NF-$\kappa$B (nuclear factor kappa B),leading to subsequent C-MYC (C-myelocytomatosis) upregulation. Promoter-reporter assays reveal that Id3 inhibits the E2A protein from activating the P62 promoter. Mice adoptively transferred with B1 cells overexpressing P62 exhibited an increase in B1b cell number and IgMOSE levels and were protected against atherosclerosis. Consistent with murine mechanistic findings,P62 expression in human B1 cells was significantly higher in subjects harboring a function-impairing single nucleotide polymorphism (SNP) at rs11574 position in the ID3 gene and directly correlated with plasma IgMOSE levels. CONCLUSIONS This study unveils a novel role for P62 in driving BAFF-induced B1b cell proliferation and IgMOSE production to attenuate diet-induced atherosclerosis. Results identify a direct role for Id3 in antagonizing E2A from activating the p62 promoter. Moreover,analysis of putative human B1 cells also implicates these pathways in coronary artery disease subjects,suggesting P62 as a new immunomodulatory target for treating atherosclerosis. View Publication

BACKGROUND Emerging evidence of antibody-independent functions,as well as the clinical efficacy of anti-CD20 depleting therapies,helped to reassess the contribution of B cells during multiple sclerosis (MS) pathogenesis. OBJECTIVE To investigate whether CD19+ B cells may share expression of the serine-protease granzyme-B (GzmB),resembling classical cytotoxic CD8+ T lymphocytes,in the peripheral blood from relapsing-remitting MS (RRMS) patients. METHODS In this study,104 RRMS patients during different treatments and 58 healthy donors were included. CD8,CD19,Runx3,and GzmB expression was assessed by flow cytometry analyses. RESULTS RRMS patients during fingolimod (FTY) and natalizumab (NTZ) treatment showed increased percentage of circulating CD8+GzmB+ T lymphocytes when compared to healthy volunteers. An increase in circulating CD19+GzmB+ B cells was observed in RRMS patients during FTY and NTZ therapies when compared to glatiramer (GA),untreated RRMS patients,and healthy donors but not when compared to interferon-$\beta$ (IFN). Moreover,regarding Runx3,the transcriptional factor classically associated with cytotoxicity in CD8+ T lymphocytes,the expression of GzmB was significantly higher in CD19+Runx3+-expressing B cells when compared to CD19+Runx3- counterparts in RRMS patients. CONCLUSIONS CD19+ B cells may exhibit cytotoxic behavior resembling CD8+ T lymphocytes in MS patients during different treatments. In the future,monitoring cytotoxic" subsets might become an accessible marker for investigating MS pathophysiology and even for the development of new therapeutic interventions." View Publication

CD8+ T cell longevity regulated by metabolic activity plays important roles in cancer immunotherapy. Although in vitro-polarized,transferred IL-9-secreting CD8+ Tc9 (cytotoxic T lymphocyte subset 9) cells exert greater persistence and antitumor efficacy than Tc1 cells,the underlying mechanism remains unclear. Here,we show that tumor-infiltrating Tc9 cells display significantly lower lipid peroxidation than Tc1 cells in several mouse models,which is strongly correlated with their persistence. Using RNA-sequence and functional validation,we found that Tc9 cells exhibited unique lipid metabolic programs. Tc9 cell-derived IL-9 activated STAT3,upregulated fatty acid oxidation and mitochondrial activity,and rendered Tc9 cells with reduced lipid peroxidation and resistance to tumor- or ROS-induced ferroptosis in the tumor microenvironment. IL-9 signaling deficiency,inhibiting STAT3,or fatty acid oxidation increased lipid peroxidation and ferroptosis of Tc9 cells,resulting in impaired longevity and antitumor ability. Similarly,human Tc9 cells also exhibited lower lipid peroxidation than Tc1 cells and tumor-infiltrating CD8+ T cells expressed lower IL9 and higher lipid peroxidation- and ferroptosis-related genes than circulating CD8+ T cells in patients with melanoma. This study indicates that lipid peroxidation regulates Tc9 cell longevity and antitumor effects via the IL-9/STAT3/fatty acid oxidation pathway and regulating T cell lipid peroxidation can be used to enhance T cell-based immunotherapy in human cancer. View Publication

Diffuse alveolar hemorrhage (DAH),although rare,is a life-threatening complication of systemic lupus erythematosus (SLE). Little is known about the pathophysiology of DAH in humans,although increasingly neutrophils,NETosis and inflammatory monocytes have been shown to play an important role in the pristane-induced model of SLE which develops lung hemorrhage and recapitulates many of the pathologic features of human DAH. Using this experimental model,we asked whether endoplasmic reticulum (ER) stress played a role in driving the pathology of pulmonary hemorrhage and what role infiltrating neutrophils had in this process. Analysis of lung tissue from pristane-treated mice showed genes associated with ER stress and NETosis were increased in a time-dependent manner and reflected the timing of CD11b+Ly6G+ neutrophil accumulation in the lung. Using precision cut lung slices from untreated mice we observed that neutrophils isolated from the peritoneal cavity of pristane-treated mice could directly induce the expression of genes associated with ER stress,namely Chop and Bip. Mice which had myeloid-specific deletion of PAD4 were generated and treated with pristane to assess the involvement of PAD4 and PAD4-dependent NET formation in pristane-induced lung inflammation. Specific deletion of PAD4 in myeloid cells resulted in decreased expression of ER stress genes in the pristane model,with accompanying reduction in IFN-driven genes and pathology. Lastly,coculture experiments of human neutrophils and human lung epithelial cell line (BEAS-2b) showed neutrophils from SLE patients induced significantly more ER stress and interferon-stimulated genes in epithelial cells compared to healthy control neutrophils. These results support a pathogenic role of neutrophils and NETs in lung injury during pristane-induced DAH through the induction of ER stress response and suggest that overactivation of neutrophils in SLE and NETosis may underlie development of DAH. View Publication

Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS-CoV-2 infection is critical for developing treatments for severe COVID-19. Here,we find decreasing number of circulating plasmacytoid dendritic cells (pDCs) in COVID-19 patients early after symptom onset,correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFN? and of systemic inflammatory cytokines CXCL10 and IL-6. Using an in vitro stem cell-based human pDC model,we further demonstrate that pDCs,while not supporting SARS-CoV-2 replication,directly sense the virus and in response produce multiple antiviral (interferons: IFN? and IFN?1) and inflammatory (IL-6,IL-8,CXCL10) cytokines that protect epithelial cells from de novo SARS-CoV-2 infection. Via targeted deletion of virus-recognition innate immune pathways,we identify TLR7-MyD88 signaling as crucial for production of antiviral interferons (IFNs),whereas Toll-like receptor (TLR)2 is responsible for the inflammatory IL-6 response. We further show that SARS-CoV-2 engages the receptor neuropilin-1 on pDCs to selectively mitigate the antiviral interferon response,but not the IL-6 response,suggesting neuropilin-1 as potential therapeutic target for stimulation of TLR7-mediated antiviral protection. View Publication

Germinal centres (GC) are lymphoid structures in which B cells acquire affinity-enhancing somatic hypermutations (SHM),with surviving clones differentiating into memory B cells (MBCs) and long-lived bone marrow plasma cells1-5 (BMPCs). SARS-CoV-2 mRNA vaccination induces a persistent GC response that lasts for at least six months in humans6-8. The fate of responding GC B cells as well as the functional consequences of such persistence remain unknown. Here,we detected SARS-CoV-2 spike protein-specific MBCs in 42 individuals who had received two doses of the SARS-CoV-2 mRNA vaccine BNT162b2 six month earlier. Spike-specific IgG-secreting BMPCs were detected in 9 out of 11 participants. Using a combined approach of sequencing the B cell receptors of responding blood plasmablasts and MBCs,lymph node GC B cells and plasma cells and BMPCs from eight individuals and expression of the corresponding monoclonal antibodies,we tracked the evolution of 1,540 spike-specific B cell clones. On average,early blood spike-specific plasmablasts exhibited the lowest SHM frequencies. By contrast,SHM frequencies of spike-specific GC B cells increased by 3.5-fold within six months after vaccination. Spike-specific MBCs and BMPCs accumulated high levels of SHM,which corresponded with enhanced anti-spike antibody avidity in blood and enhanced affinity as well as neutralization capacity of BMPC-derived monoclonal antibodies. We report how the notable persistence of the GC reaction induced by SARS-CoV-2 mRNA vaccination in humans culminates in affinity-matured long-term antibody responses that potently neutralize the virus. View Publication