Nuclear morphology is shaped by loop-extrusion programs

It is well established that neutrophils adopt malleable polymorphonuclear shapes to migrate through narrow interstitial tissue spaces1-3. However, how polymorphonuclear structures are assembled remains unknown4. Here we show that in neutrophil progenitors, halting loop extrusion-a motor-powered process that generates DNA loops by pulling in chromatin5-leads to the assembly of polymorphonuclear genomes. Specifically, we found that in mononuclear neutrophil progenitors, acute depletion of the loop-extrusion loading factor nipped-B-like protein (NIPBL) induced the assembly of horseshoe, banded, ringed and hypersegmented nuclear structures and led to a reduction in nuclear volume, mirroring what is observed during the differentiation of neutrophils. Depletion of NIPBL also induced cell-cycle arrest, activated a neutrophil-specific gene program and conditioned a loss of interactions across topologically associating domains to generate a chromatin architecture that resembled that of differentiated neutrophils. Removing NIPBL resulted in enrichment for mega-loops and interchromosomal hubs that contain genes associated with neutrophil-specific enhancer repertoires and an inflammatory gene program. On the basis of these observations, we propose that in neutrophil progenitors, loop-extrusion programs produce lineage-specific chromatin architectures that permit the packing of chromosomes into geometrically confined lobular structures. Our data also provide a blueprint for the assembly of polymorphonuclear structures, and point to the possibility of engineering de novo nuclear shapes to facilitate the migration of effector cells in densely populated tumorigenic environments.

Human coronavirus OC43-elicited CD4+ T cells protect against SARS-CoV-2 in HLA transgenic mice

SARS-CoV-2-reactive T cells are detected in some healthy unexposed individuals. Human studies indicate these T cells could be elicited by the common cold coronavirus OC43. To directly test this assumption and define the role of OC43-elicited T cells that are cross-reactive with SARS-CoV-2, we develop a model of sequential infections with OC43 followed by SARS-CoV-2 in HLA-B*0702 and HLA-DRB1*0101 Ifnar1-/- transgenic mice. We find that OC43 infection can elicit polyfunctional CD8+ and CD4+ effector T cells that cross-react with SARS-CoV-2 peptides. Furthermore, pre-exposure to OC43 reduces subsequent SARS-CoV-2 infection and disease in the lung for a short-term in HLA-DRB1*0101 Ifnar1-/- transgenic mice, and a longer-term in HLA-B*0702 Ifnar1-/- transgenic mice. Depletion of CD4+ T cells in HLA-DRB1*0101 Ifnar1-/- transgenic mice with prior OC43 exposure results in increased viral burden in the lung but no change in virus-induced lung damage following infection with SARS-CoV-2 (versus CD4+ T cell-sufficient mice), demonstrating that the OC43-elicited SARS-CoV-2 cross-reactive T cell-mediated cross-protection against SARS-CoV-2 is partially dependent on CD4+ T cells. These findings contribute to our understanding of the origin of pre-existing SARS-CoV-2-reactive T cells and their effects on SARS-CoV-2 clinical outcomes, and also carry implications for development of broadly protective betacoronavirus vaccines.

YAP-Driven Malignant Reprogramming of Epithelial Stem Cells at Single Cell Resolution

Tumor initiation represents the first step in tumorigenesis during which normal progenitor cells undergo cell fate transition to cancer. Capturing this process as it occurs in vivo, however, remains elusive. Here we employ cell tracing approaches with spatiotemporally controlled oncogene activation and tumor suppressor inhibition to unveil the processes underlying oral epithelial progenitor cell reprogramming into cancer stem cells (CSCs) at single cell resolution. This revealed the rapid emergence of a distinct stem-like cell state, defined by aberrant proliferative, hypoxic, squamous differentiation, and partial epithelial to mesenchymal (pEMT) invasive gene programs. Interestingly, CSCs harbor limited cell autonomous invasive capacity, but instead recruit myeloid cells to remodel the basement membrane and ultimately initiate tumor invasion. CSC transcriptional programs are conserved in human carcinomas and associated with poor patient survival. These findings illuminate the process of cancer initiation at single cell resolution, thus identifying candidate targets for early cancer detection and prevention.

Hepatic pIgR-mediated secretion of IgA limits bacterial translocation and prevents ethanol-induced liver disease in mice

OBJECTIVE

Alcohol-associated liver disease is accompanied by microbial dysbiosis, increased intestinal permeability and hepatic exposure to translocated microbial products that contribute to disease progression. A key strategy to generate immune protection against invading pathogens is the secretion of IgA in the gut. Intestinal IgA levels depend on the polymeric immunoglobulin receptor (pIgR), which transports IgA across the epithelial barrier into the intestinal lumen and hepatic canaliculi. Here, we aimed to address the function of pIgR during ethanol-induced liver disease.

DESIGN

pIgR and IgA were assessed in livers from patients with alcohol-associated hepatitis and controls. Wild-type and pIgR-deficient (pIgR-/- ) littermates were subjected to the chronic-binge (NIAAA model) and Lieber-DeCarli feeding model for 8 weeks. Hepatic pIgR re-expression was established in pIgR-/- mice using adeno-associated virus serotype 8 (AAV8)-mediated pIgR expression in hepatocytes.

RESULTS

Livers of patients with alcohol-associated hepatitis demonstrated an increased colocalisation of pIgR and IgA within canaliculi and apical poles of hepatocytes. pIgR-deficient mice developed increased liver injury, steatosis and inflammation after ethanol feeding compared with wild-type littermates. Furthermore, mice lacking pIgR demonstrated increased plasma lipopolysaccharide levels and more hepatic bacteria, indicating elevated bacterial translocation. Treatment with non-absorbable antibiotics prevented ethanol-induced liver disease in pIgR-/- mice. Injection of AAV8 expressing pIgR into pIgR-/- mice prior to ethanol feeding increased intestinal IgA levels and ameliorated ethanol-induced steatohepatitis compared with pIgR-/- mice injected with control-AAV8 by reducing bacterial translocation.

CONCLUSION

Our results highlight that dysfunctional hepatic pIgR enhances alcohol-associated liver disease due to impaired antimicrobial defence by IgA in the gut.

Direct reprogramming of oral epithelial progenitor cells to cancer stem cells at single cell resolution in vivo

Tumor initiation represents the initial step in tumorigenesis during which normal progenitor cells undergo cell fate transition to cancer. Most studies investigating cancer-driving mechanisms in solid tumors rely on analyses of established malignant lesions, and thus cannot directly capture processes underlying the reprogramming of normal progenitor cells into cancer cells. Here, using spatiotemporally controlled oncogene expression in a genetically engineered system we demonstrate that concomitant YAP activation and HPV E6-E7 -mediated inhibition of tumor suppressive pathways is sufficient to rapidly reprogram oral epithelial progenitor cells (OEPCs) into cancer stem cells (CSCs). Single cell analyses of these nascent CSCs revealed hallmark transcriptional programs driving tumor initiation. Importantly, these CSC-enriched expression signatures distinguish normal tissue from malignant head and neck tumors and are associated with poor patient survival. Elucidating mechanisms underlying OEPC to CSC reprogramming may offer new insights to halt the conversion of premalignant cells into invasive carcinoma.

HIGHLIGHTS

YAP and HPV E6-E7 reprogram oral epithelial progenitor cells into cancer stem cells. Single cell analyses reveal the transcriptional architecture of tumor initiation.CSC transcriptional programs distinguish normal tissue from carcinoma.CSC signatures are associated with poor head and neck cancer survival.

Abstract Figure

Intravital Imaging of Intestinal Intraepithelial Lymphocytes

Intestinal intraepithelial lymphocytes (IEL) are a numerous population of T cells located within the epithelium of the small and large intestines, being more numerous in the small intestine (SI). They surveil this tissue by interacting with epithelial cells. Intravital microscopy is an important tool for visualizing the patrolling activity of IEL in the SI of live mice. Most IEL express CD8α; therefore, here we describe an established protocol of intravital imaging that tracks lymphocytes labeled with a CD8α-specific monoclonal antibody in the SI epithelium of live mice. We also describe data acquisition and quantification of the movement metrics, including mean speed, track length, displacement length, and paths for each CD8α+ IEL using the available software. The intravital imaging technique for measuring IEL movement will provide a better understanding of the role of IEL in homeostasis and protection from injury or infection in vivo.

SARS-CoV-2 Omicron (B.1.1.529) shows minimal neurotropism in a double-humanized mouse model

Although severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) initially infects the respiratory tract, it also directly or indirectly affects other organs, including the brain. However, little is known about the relative neurotropism of SARS-CoV-2 variants of concern (VOCs), including Omicron (B.1.1.529), which emerged in November 2021 and has remained the dominant pathogenic lineage since then. To address this gap, we examined the relative ability of Omicron, Beta (B.1.351), and Delta (B.1.617.2) to infect the brain in the context of a functional human immune system by using human angiotensin-converting enzyme 2 (hACE2) knock-in triple-immunodeficient NGC mice with or without reconstitution with human CD34+ stem cells. Intranasal inoculation of huCD34+-hACE2-NCG mice with Beta and Delta resulted in productive infection of the nasal cavity, lungs, and brain on day 3 post-infection, but Omicron was surprisingly unique in its failure to infect either the nasal tissue or brain. Moreover, the same infection pattern was observed in hACE2-NCG mice, indicating that antiviral immunity was not responsible for the lack of Omicron neurotropism. In independent experiments, we demonstrate that nasal inoculation with Beta or with D614G, an ancestral SARS-CoV-2 with undetectable replication in huCD34+-hACE2-NCG mice, resulted in a robust response by human innate immune cells, T cells, and B cells, confirming that exposure to SARS-CoV-2, even without detectable infection, is sufficient to induce an antiviral immune response. Collectively, these results suggest that modeling of the neurologic and immunologic sequelae of SARS-CoV-2 infection requires careful selection of the appropriate SARS-CoV-2 strain in the context of a specific mouse model.

Treatment of pancreatic cancer with irreversible electroporation and intratumoral CD40 antibody stimulates systemic immune responses that inhibit liver metastasis in an orthotopic model

BACKGROUND

Pancreatic cancer (PC) has a poor prognosis, and most patients present with either locally advanced or distant metastatic disease. Irreversible electroporation (IRE) is a non-thermal method of ablation used clinically in locally advanced PC, but most patients eventually develop distant recurrence. We have previously shown that IRE alone is capable of generating protective, neoantigen-specific immunity. Here, we aim to generate meaningful therapeutic immune effects by combining IRE with local (intratumoral) delivery of a CD40 agonistic antibody (CD40Ab).

METHODS

KPC46 organoids were generated from a tumor-bearing male KrasLSL-G12D-p53LSL-R172H-Pdx-1-Cre (KPC) mouse. Orthotopic tumors were established in the pancreatic tail of B6/129 F1J mice via laparotomy. Mice were randomized to treatment with either sham laparotomy, IRE alone, CD40Ab alone, or IRE followed immediately by CD40Ab injection. Metastatic disease and immune infiltration in the liver were analyzed 14 days postprocedure using flow cytometry and multiplex immunofluorescence imaging with spatial analysis. Candidate neoantigens were identified by mutanome profiling of tumor tissue for ex vivo functional analyses.

RESULTS

The combination of IRE+CD40 Ab improved median survival to greater than 35 days, significantly longer than IRE (21 days) or CD40Ab (24 days) alone (p<0.01). CD40Ab decreased metastatic disease burden, with less disease in the combination group than in the sham group or IRE alone. Immunohistochemistry of liver metastases revealed a more than twofold higher infiltration of CD8+T cells in the IRE+CD40 Ab group than in any other group (p<0.01). Multiplex immunofluorescence imaging revealed a 4-6 fold increase in the density of CD80+CD11c+ activated dendritic cells (p<0.05), which were spatially distributed throughout the tumor unlike the sham group, where they were restricted to the periphery. In contrast, CD4+FoxP3+ T-regulatory cells (p<0.05) and Ly6G+myeloid derived cells (p<0.01) were reduced and restricted to the tumor periphery in the IRE+CD40 Ab group. T-cells from the IRE+CD40 Ab group recognized significantly more peptides representing candidate neoantigens than did T-cells from the IRE or untreated control groups.

CONCLUSIONS

IRE can induce local tumor regression and neoantigen-specific immune responses. Addition of CD40Ab to IRE improved dendritic cell activation and neoantigen recognition, while generating a strong systemic antitumor T-cell response that inhibited metastatic disease progression.

Effect of IL4 and IL10 on a human in vitro type 1 diabetes model

We defined the effect of the anti-inflammatory cytokines IL4 and IL10 on an in vitro model of human T1D. After preincubation with IL4 or IL10, human islet microtissues were co-cultured with PBMC and proinflammatory cytokines for a few hours or for multiple days to assess acute and chronic effects. This resulted in an immune attack with infiltration of T cells into the islet, a loss of beta cell endocrine function, and an upregulation of HLA-I on the beta cells. HLA-I upregulation was associated with infiltration of T cells and both HLA-I expression and infiltration were associated with impaired insulin secretion. Preincubation with IL4 or IL10 did not preserve beta cell function but decreased infiltration of T cells. Our data support the hypothesis that a loss of beta cell endocrine function mediates an increase in beta cell specific antigen presentation. IL4 and IL10 failed to preserve beta cell endocrine function.

Epithelial HVEM maintains intraepithelial T cell survival and contributes to host protection

Intraepithelial T cells (IETs) are in close contact with intestinal epithelial cells and the underlying basement membrane, and they detect invasive pathogens. How intestinal epithelial cells and basement membrane influence IET survival and function, at steady state or after infection, is unclear. The herpes virus entry mediator (HVEM), a member of the TNF receptor superfamily, is constitutively expressed by intestinal epithelial cells and is important for protection from pathogenic bacteria. Here, we showed that at steady-state LIGHT, an HVEM ligand, binding to epithelial HVEM promoted the survival of small intestine IETs. RNA-seq and addition of HVEM ligands to epithelial organoids indicated that HVEM increased epithelial synthesis of basement membrane proteins, including collagen IV, which bound to β₁ integrins expressed by IETs. Therefore, we proposed that IET survival depended on β₁ integrin binding to collagen IV and showed that β₁ integrin-collagen IV interactions supported IET survival in vitro. Moreover, the absence of β₁ integrin expression by T lymphocytes decreased TCR αβ⁺ IETs in vivo. Intravital microscopy showed that the patrolling movement of IETs was reduced without epithelial HVEM. As likely consequences of decreased number and movement, protective responses to Salmonella enterica were reduced in mice lacking either epithelial HVEM, HVEM ligands, or β₁ integrins. Therefore, IETs, at steady state and after infection, depended on HVEM expressed by epithelial cells for the synthesis of collagen IV by epithelial cells. Collagen IV engaged β₁ integrins on IETs that were important for their maintenance and for their protective function in mucosal immunity.

A humanized β2 integrin knockin mouse reveals localized intra- and extravascular neutrophil integrin activation in vivo

β₂ integrins are leukocyte-specific adhesion molecules that are essential for leukocyte recruitment. The lack of tools for reporting β₂ integrin activation in mice hindered the study of β₂ integrin-related immune responses in vivo. Here, we generated a humanized β₂ integrin knockin mouse strain by targeting the human β₂ integrin coding sequence into the mouse Itgb2 locus to enable imaging of β₂ integrin activation using the KIM127 (extension) and mAb24 (high-affinity) reporter antibodies. Using a CXCL1-induced acute inflammation model, we show the local dynamics of β₂ integrin activation in arresting neutrophils in vivo in venules of the mouse cremaster muscle. Activated integrins are highly concentrated in a small area at the rear of arresting neutrophils in vivo. In a high-dose lipopolysaccharide model, we find that β₂ integrins are activated in association with elevated neutrophil adhesion in lung and liver. Thus, these mice enable studies of β₂ integrin activation in vivo.

A new β2 integrin activation reporter mouse reveals localized intra- and extra-vascular neutrophil integrin activation in vivo

β2 integrins (LFA-1, Mac-1, CD11c-CD18, and CD11d-CD18) are leukocyte-specific adhesion receptors that play critical roles in leukocyte recruitment, as well as other immunological processes such as phagocytosis and immunological synapse formation. Adhesion of leukocytes to other cells such as endothelial cells are regulated by integrin affinity changes for their ligands (“activation”). Human β2 integrin activation can be detected by reporter antibodies including mAb24 and KIM127. No such activation epitopes are known in mouse β2 integrins. Because of the lack of mouse β2 integrin activation reporter antibodies, nothing is known about β2 integrin activation in vivo. Here, we generated a humanized β2 integrin knockin mouse by targeting the human β2 integrin coding sequence into the mouse Itgb2 locus. We show that this enables imaging of β2 integrin activation using the KIM127 (extension conformation) and mAb24 (high affinity) reporter antibodies. Human β2 pairs with the mouse integrin α chains, yielding normal expression of the β2 integrins LFA-1, Mac-1 and CD11c-CD18 in all major leukocyte populations. Using a CXCL1-induced acute inflammation model, we uncovered the dynamics and subcellular localization of β2 integrin activation in arresting neutrophils in vivo in venules of the mouse cremaster muscle. Activated integrins in arresting neutrophils in vivo are concentrated at the interface of neutrophils and the endothelium at the rear side of neutrophils facing against the blood flow. In a high-dose lipopolysaccharide (LPS) model, we found that β2 integrins are activated in association with elevated neutrophil adhesion in lung and liver. Thus, these mice, for the first time, enable studies into β2 integrin activation in vivo.

This work was supported by grants from the National Institutes of Health, USA (HL078784 to K.L.) and a Postdoctoral Fellowship (19POST34450228 to L.W.) from the American Heart Association, USA.

Tumor FAK orchestrates immunosuppression in ovarian cancer via the CD155/TIGIT axis

High-grade serous ovarian cancer (HGSOC) is a lethal malignancy characterized by an immunosuppressive tumor microenvironment containing few tumor infiltrating lymphocytes (TILs) and an insensitivity to checkpoint inhibitor immunotherapies. Gains in the PTK2 gene encoding focal adhesion kinase (FAK) at Chr8 q24.3 occur in ∼70% of HGSOC tumors, and elevated FAK messenger RNA (mRNA) levels are associated with poor patient survival. Herein, we show that active FAK, phosphorylated at tyrosine-576 within catalytic domain, is significantly increased in late-stage HGSOC tumors. Active FAK costained with CD155, a checkpoint receptor ligand for TIGIT (T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains), in HGSOC tumors and a selective association between FAK and TIGIT checkpoint ligands were supported by patient transcriptomic database analysis. HGSOC tumors with high FAK expression were associated with low CD3 mRNA levels. Accordingly, late-stage tumors showed elevated active FAK staining and significantly lower levels of CD3+ TILs. Using the KMF (Kras, Myc, FAK) syngeneic ovarian tumor model containing spontaneous PTK2 (FAK) gene gains, the effects of tumor intrinsic genetic or oral small molecule FAK inhibitior (FAKi; VS-4718) were evaluated in vivo. Blocking FAK activity decreased tumor burden, suppressed ascites KMF-associated CD155 levels, and increased peritoneal TILs. The combination of FAKi with blocking TIGIT antibody (1B4) maintained elevated TIL levels and reduced TIGIT+ T regulatory cell levels, prolonged host survival, increased CXCL13 levels, and led to the formation of omental tertiary lymphoid structures. Collectively, our studies support FAK and TIGIT targeting as a rationale immunotherapy combination for HGSOC.

Oxidative stress promotes fibrosis in systemic sclerosis through stabilization of a kinase-phosphatase complex

Systemic sclerosis (SSc) is a fibrotic autoimmune disease characterized by pathogenic activation of fibroblasts enhanced by local oxidative stress. The tyrosine phosphatase PTP4A1 was identified as a critical promoter of TGF-β signaling in SSc. Oxidative stress is known to functionally inactivate tyrosine phosphatases. Here, we assessed whether oxidation of PTP4A1 modulates its profibrotic action and found that PTP4A1 forms a complex with the kinase SRC in scleroderma fibroblasts, but surprisingly, oxidative stress enhanced rather than reduced PTP4A1’s association with SRC and its profibrotic action. Through structural assessment of the oxo-PTP4A1-SRC complex, we unraveled an unexpected mechanism whereby oxidation of a tyrosine phosphatase promotes its function through modification of its protein complex. Considering the importance of oxidative stress in the pathogenesis of SSc and fibrosis, our findings suggest routes for leveraging PTP4A1 oxidation as a potential strategy for developing antifibrotic agents.

Microneedle-mediated Intratumoral Delivery of Anti-CTLA-4 Promotes cDC1-dependent Eradication of Oral Squamous Cell Carcinoma with Limited irAEs

Head and neck squamous cell carcinoma (HNSCC) ranks sixth in cancer incidence worldwide and has a 5-year survival rate of only 63%. Immunotherapies-principally immune checkpoint inhibitors (ICI), such as anti-PD-1 and anti-CTLA-4 antibodies that restore endogenous antitumor T-cell immunity-offer the greatest promise for HNSCC treatment. Anti-PD-1 has been recently approved for first-line treatment of recurrent and metastatic HNSCC; however, less than 20% of patients show clinical benefit and durable responses. In addition, the clinical application of ICI has been limited by immune-related adverse events (irAE) consequent to compromised peripheral immune tolerance. Although irAEs are often reversible, they can become severe, prompting premature therapy termination or becoming life threatening. To address the irAEs inherent to systemic ICI therapy, we developed a novel, local delivery strategy based upon an array of soluble microneedles (MN). Using our recently reported syngeneic, tobacco-signature murine HNSCC model, we found that both systemic and local-MN anti-CTLA-4 therapy lead to >90% tumor response, which is dependent on CD8 T cells and conventional dendritic cell type 1 (cDC1). However, local-MN delivery limited the distribution of anti-CTLA-4 antibody from areas distal to draining lymphatic basins. Employing Foxp3-GFPDTR transgenic mice to interrogate irAEs in vivo, we found that local-MN delivery of anti-CTLA-4 protects animals from irAEs observed with systemic therapy. Taken together, our findings support the exploration of MN-intratumoral ICI delivery as a viable strategy for HNSCC treatment with reduced irAEs, and the opportunity to target cDC1s as part of multimodal treatment options to boost ICI therapy.

Upregulation of HLA class II in pancreatic beta cells from organ donors with type 1 diabetes

AIMS/HYPOTHESIS

We aimed to characterise and quantify the expression of HLA class II (HLA-II) in human pancreatic tissue sections and to analyse its induction in human islets.

METHODS

We immunostained human pancreatic tissue sections from non-diabetic (n = 5), autoantibody positive (Aab+; n = 5), and type 1 diabetic (n = 5) donors, obtained from the Network of Pancreatic Organ Donors (nPOD), with HLA-II, CD68 and insulin. Each tissue section was acquired with a widefield slide scanner and then analysed with QuPath software. In total, we analysed 7415 islets that contained 338,480 cells. Widefield microscopy was further complemented by high resolution imaging of 301 randomly selected islets, acquired using a Zeiss laser scanning confocal (LSM880) to confirm our findings. Selected beta cells were acquired in enhanced resolution using LSM880 with an Airyscan detector. Further, we cultured healthy isolated human islets and reaggregated human islet microtissues with varying concentrations of proinflammatory cytokines (IFN-γ, TNF-α and IL-1β). After proinflammatory cytokine culture, islet function was measured by glucose-stimulated insulin secretion, and HLA-I and HLA-II expression was subsequently evaluated with immunostaining or RNA sequencing.

RESULTS

Insulin-containing islets (ICIs) of donors with type 1 diabetes had a higher percentage of HLA-II positive area (24.31%) compared with type 1 diabetic insulin-deficient islets (IDIs, 0.67%), non-diabetic (3.80%), and Aab+ (2.31%) donors. In ICIs of type 1 diabetic donors, 45.89% of the total insulin signal co-localised with HLA-II, and 27.65% of the islet beta cells expressed both HLA-II and insulin, while in non-diabetic and Aab+ donors 0.96% and 0.59% of the islet beta cells, respectively, expressed both markers. In the beta cells of donors with type 1 diabetes, HLA-II was mostly present in the cell cytoplasm, co-localising with insulin. In the experiments with human isolated islets and reaggregated human islets, we observed changes in insulin secretion upon stimulation with proinflammatory cytokines, as well as higher expression of HLA-II and HLA-I when compared with controls cultured with media, and an upregulation of HLA-I and HLA-II RNA transcripts.

CONCLUSIONS/INTERPRETATION

After a long-standing controversy, we provide definitive evidence that HLA-II can be expressed by pancreatic beta cells from patients with type 1 diabetes. Furthermore, this upregulation can be induced in vitro in healthy isolated human islets or reaggregated human islets by treatment with proinflammatory cytokines. Our findings support a role for HLA-II in type 1 diabetes pathogenesis since HLA-II expressing beta cells can potentially become a direct target of autoreactive CD4+ lymphocytes.

Bone Marrow Transplantation Rescues Monocyte Recruitment Defect and Improves Cystic Fibrosis in Mice

Cystic fibrosis (CF) is an inherited life-threatening disease accompanied by repeated lung infections and multiorgan inflammation that affects tens of thousands of people worldwide. The causative gene, cystic fibrosis transmembrane conductance regulator (CFTR), is mutated in CF patients. CFTR functions in epithelial cells have traditionally been thought to cause the disease symptoms. Recent work has shown an additional defect: monocytes from CF patients show a deficiency in integrin activation and adhesion. Because monocytes play critical roles in controlling infections, defective monocyte function may contribute to CF progression. In this study, we demonstrate that monocytes from CFTR^ΔF508 mice (CF mice) show defective adhesion under flow. Transplanting CF mice with wild-type (WT) bone marrow after sublethal irradiation replaced most (60-80%) CF monocytes with WT monocytes, significantly improved survival, and reduced inflammation. WT/CF mixed bone marrow chimeras directly demonstrated defective CF monocyte recruitment to the bronchoalveolar lavage and the intestinal lamina propria in vivo. WT mice reconstituted with CF bone marrow also show lethality, suggesting that the CF defect in monocytes is not only necessary but also sufficient to cause disease. We also show that monocyte-specific knockout of CFTR retards weight gains and exacerbates dextran sulfate sodium-induced colitis. Our findings show that providing WT monocytes by bone marrow transfer rescues mortality in CF mice, suggesting that similar approaches may mitigate disease in CF patients.

Olfactory receptor 2 in vascular macrophages drives atherosclerosis by NLRP3-dependent IL-1 production

Atherosclerosis is an inflammatory disease of the artery walls and involves immune cells such as macrophages. Olfactory receptors (OLFRs) are G protein–coupled chemoreceptors that have a central role in detecting odorants and the sense of smell. We found that mouse vascular macrophages express the olfactory receptor Olfr2 and all associated trafficking and signaling molecules. Olfr2 detects the compound octanal, which activates the NLR family pyrin domain containing 3 (NLRP3) inflammasome and induces interleukin-1β secretion in human and mouse macrophages. We found that human and mouse blood plasma contains octanal, a product of lipid peroxidation, at concentrations sufficient to activate Olfr2 and the human ortholog olfactory receptor 6A2 (OR6A2). Boosting octanal levels exacerbated atherosclerosis, whereas genetic targeting of Olfr2 in mice significantly reduced atherosclerotic plaques. Our findings suggest that inhibiting OR6A2 may provide a promising strategy to prevent and treat atherosclerosis.

Stimulation of a subset of natural killer T cells by CD103+ DC is required for GM-CSF and protection from pneumococcal infection

Innate-like T cells, including invariant natural killer T cells, mucosal-associated invariant T cells, and γδ T cells, are present in various barrier tissues, including the lung, where they carry out protective responses during infections. Here, we investigate their roles during pulmonary pneumococcal infection. Following infection, innate-like T cells rapidly increase in lung tissue, in part through recruitment, but T cell antigen receptor activation and cytokine production occur mostly in interleukin-17-producing NKT17 and γδ T cells. NKT17 cells are preferentially located within lung tissue prior to infection, as are CD103⁺ dendritic cells, which are important both for antigen presentation to NKT17 cells and γδ T cell activation. Whereas interleukin-17-producing γδ T cells are numerous, granulocyte-macrophage colony-stimulating factor is exclusive to NKT17 cells and is required for optimal protection. These studies demonstrate how particular cellular interactions and responses of functional subsets of innate-like T cells contribute to protection from pathogenic lung infection.

Protein Kinase A in Human Retina: Differential Localization of Cβ, Cα, RIIα, and RIIβ in Photoreceptors Highlights Non-redundancy of Protein Kinase A Subunits

Protein kinase A (PKA) signaling is essential for numerous processes but the subcellular localization of specific PKA regulatory (R) and catalytic (C) subunits has yet to be explored comprehensively. Additionally, the localization of the Cβ subunit has never been spatially mapped in any tissue even though ∼50% of PKA signaling in neuronal tissues is thought to be mediated by Cβ. Here we used human retina with its highly specialized neurons as a window into PKA signaling in the brain and characterized localization of PKA Cα, Cβ, RIIα, and RIIβ subunits. We found that each subunit presented a distinct localization pattern. Cα and Cβ were localized in all cell layers (photoreceptors, interneurons, retinal ganglion cells), while RIIα and RIIβ were selectively enriched in photoreceptor cells where both showed distinct patterns of co-localization with Cα but not Cβ. Only Cα was observed in photoreceptor outer segments and at the base of the connecting cilium. Cβ in turn, was highly enriched in mitochondria and was especially prominent in the ellipsoid of cone cells. Further investigation of Cβ using RNA BaseScope technology showed that two Cβ splice variants (Cβ4 and Cβ4ab) likely code for the mitochondrial Cβ proteins. Overall, our data indicates that PKA Cα, Cβ, RIIα, and RIIβ subunits are differentially localized and are likely functionally non-redundant in the human retina. Furthermore, Cβ is potentially important for mitochondrial-associated neurodegenerative diseases previously linked to PKA dysfunction.

Abstract 1610: Local delivery of anti CTLA4 mediates cDC1 dependent eradication of HNSCC with limited IRAEs in a preclinical model of oral squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) ranks 6th in cancer incidence worldwide and has a five-year survival rate of only 63%. Despite advances in curative-intent therapies over the past three decades, rates of recurrence exceed 50% and long-term toxicities remain unacceptably morbid. Immunotherapies - principally immune checkpoint inhibitors (ICI) such as αPD-1 and αCTLA-41 antibodies which restore endogenous antitumor T cell immunity - offer the greatest promise for achieving durable response in HNSCC. However, the clinical application of ICI has been limited by immune-related adverse events (irAEs), which is a consequence of compromised peripheral immune tolerance after ICI therapy. Although irAEs are often reversible they can become severe, at best prompting premature termination of therapy or at worst becoming life-threatening. To address the off-target irAEs inherent to systemic ICI therapy, we developed a novel, local delivery strategy based upon an array of soluble microneedles (MN). Leveraging our recently reported syngeneic, tobacco-signature murine HNSCC model, we characterized the αCTLA-41 anti-tumor response as both CD8 T cell- and conventional dendritic cell type 1-dependent. When comparing αCTLA-4 therapy delivered in the traditional systemic format or with our local-MN delivery system, we found that while both routes of delivery led to &gt;90% tumor responses, local-MN delivery achieved responses with lower total dosing while also limiting distribution of αCTLA-41 antibody from areas distal to draining lymphatic basins. Employing the previously described Foxp3-GFP-DTR GEMM developed for interrogation of murine irAEs, we found that local-MN protected animals from irAEs observed with systemic therapy. Taken together, our findings support the exploration of the microneedle array as a viable delivery strategy for ICI treatment in HNSCC.

Citation Format: Mara Gilardi, Zhiyong Wang, Victoria H. Wu, Miguel Angel Lopez-Ramirez, Fernando Soto-Alvarez, Robert Saddawi-Konefka, Dana Steffen, Marco Proietto, Zbigniew Mikulski, Haruka Miki, Jayanth Shankara Narayanan, Alfredo Molinolo, Joseph Wang, J. Silvio Gutkind. Local delivery of anti CTLA4 mediates cDC1 dependent eradication of HNSCC with limited IRAEs in a preclinical model of oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1610.

The Role of IgM Antibodies in T Cell Lymphoma Protection in a Novel Model Resembling Anaplastic Large Cell Lymphoma

MRL/lpr mice typically succumb to immune complex-mediated nephritis within the first year of life. However, MRL/lpr mice that only secrete IgM Abs because of activation-induced deaminase deficiency (AID^-/-MRL/lpr mice) experienced a dramatic increase in survival. Further crossing of these mice to those incapable of making secretory IgM (μS mice) generated mice lacking any secreted Abs but with normal B cell receptors. Both strains revealed no kidney pathology, yet Ab-deficient mice still experienced high mortality. In this article, we report Ab-deficient MRL/lpr mice progressed to high-grade T cell lymphoma that can be reversed with injection of autoreactive IgM Abs or following adoptive transfer of IgM-secreting MRL/lpr B cells. Anti-nuclear Abs, particularly anti-dsDNA IgM Abs, exhibited tumor-killing activities against a murine T cell lymphoma cell line. Passive transfers of autoreactive IgM Abs into p53-deficient mice increased survival by delaying onset of T cell lymphoma. The lymphoma originated from a double-negative aberrant T cell population seen in MRL/lpr mice and most closely resembled human anaplastic large cell lymphoma. Combined, these results strongly implicate autoreactive IgM Abs in protection against T cell lymphoma.

Elongated neutrophil-derived structures are blood-borne microparticles formed by rolling neutrophils during sepsis

Rolling neutrophils form tethers with submicron diameters. Here, we report that these tethers detach, forming elongated neutrophil-derived structures (ENDS) in the vessel lumen. We studied ENDS formation in mice and humans in vitro and in vivo. ENDS do not contain mitochondria, endoplasmic reticulum, or DNA, but are enriched for S100A8, S100A9, and 57 other proteins. Within hours of formation, ENDS round up, and some of them begin to present phosphatidylserine on their surface (detected by annexin-5 binding) and release S100A8-S100A9 complex, a damage-associated molecular pattern protein that is a known biomarker of neutrophilic inflammation. ENDS appear in blood plasma of mice upon induction of septic shock. Compared with healthy donors, ENDS are 10-100-fold elevated in blood plasma of septic patients. Unlike neutrophil-derived extracellular vesicles, most ENDS are negative for the tetraspanins CD9, CD63, and CD81. We conclude that ENDS are a new class of bloodborne submicron particles with a formation mechanism linked to neutrophil rolling on the vessel wall.

Tipifarnib as a Precision Therapy for HRAS-Mutant Head and Neck Squamous Cell Carcinomas

Tipifarnib is a potent and highly selective inhibitor of farnesyltransferase (FTase). FTase catalyzes the posttranslational attachment of farnesyl groups to signaling proteins that are required for localization to cell membranes. Although all RAS isoforms are FTase substrates, only HRAS is exclusively dependent upon farnesylation, raising the possibility that HRAS-mutant tumors might be susceptible to tipifarnib-mediated inhibition of FTase. Here, we report the characterization of tipifarnib activity in a wide panel of HRAS-mutant and wild-type head and neck squamous cell carcinoma (HNSCC) xenograft models. Tipifarnib treatment displaced both mutant and wild-type HRAS from membranes but only inhibited proliferation, survival, and spheroid formation of HRAS-mutant cells. In vivo, tipifarnib treatment induced tumor stasis or regression in all six HRAS-mutant xenografts tested but displayed no activity in six HRAS wild-type patient-derived xenograft (PDX) models. Mechanistically, drug treatment resulted in the reduction of MAPK pathway signaling, inhibition of proliferation, induction of apoptosis, and robust abrogation of neovascularization, apparently via effects on both tumor cells and endothelial cells. Bioinformatics and quantitative image analysis further revealed that FTase inhibition induces progressive squamous cell differentiation in tipifarnib-treated HNSCC PDXs. These preclinical findings support that HRAS represents a druggable oncogene in HNSCC through FTase inhibition by tipifarnib, thereby identifying a precision therapeutic option for HNSCCs harboring HRAS mutations.

Pathogenic Autoimmunity in Atherosclerosis Evolves From Initially Protective Apolipoprotein B100-Reactive CD4+ T-Regulatory Cells

BACKGROUND

Throughout the inflammatory response that accompanies atherosclerosis, autoreactive CD4⁺ T-helper cells accumulate in the atherosclerotic plaque. Apolipoprotein B₁₀₀ (apoB), the core protein of low-density lipoprotein, is an autoantigen that drives the generation of pathogenic T-helper type 1 (T_H1) cells with proinflammatory cytokine secretion. Clinical data suggest the existence of apoB-specific CD4⁺ T cells with an atheroprotective, regulatory T cell (T_reg) phenotype in healthy individuals. Yet, the function of apoB-reactive T_regs and their relationship with pathogenic T_H1 cells remain unknown.

METHODS

To interrogate the function of autoreactive CD4⁺ T cells in atherosclerosis, we used a novel tetramer of major histocompatibility complex II to track T cells reactive to the mouse self-peptide apo B_978-993 (apoB⁺) at the single-cell level.

RESULTS

We found that apoB⁺ T cells build an oligoclonal population in lymph nodes of healthy mice that exhibit a T_reg-like transcriptome, although only 21% of all apoB⁺ T cells expressed the T_reg transcription factor FoxP3 (Forkhead Box P3) protein as detected by flow cytometry. In single-cell RNA sequencing, apoB⁺ T cells formed several clusters with mixed T_H signatures that suggested overlapping multilineage phenotypes with pro- and anti-inflammatory transcripts of T_H1, T helper cell type 2 (T_H2), and T helper cell type 17 (T_H17), and of follicular-helper T cells. ApoB⁺ T cells were increased in mice and humans with atherosclerosis and progressively converted into pathogenic T_H1/T_H17-like cells with proinflammatory properties and only a residual T_reg transcriptome. Plaque T cells that expanded during progression of atherosclerosis consistently showed a mixed T_H1/T_H17 phenotype in single-cell RNA sequencing. In addition, we observed a loss of FoxP3 in a fraction of apoB⁺ T_regs in lineage tracing of hyperlipidemic Apoe^-/- mice. In adoptive transfer experiments, converting apoB⁺ T_regs failed to protect from atherosclerosis.

CONCLUSIONS

Our results demonstrate an unexpected mixed phenotype of apoB-reactive autoimmune T cells in atherosclerosis and suggest an initially protective autoimmune response against apoB with a progressive derangement in clinical disease. These findings identify apoB autoreactive T_regs as a novel cellular target in atherosclerosis.

Olfactory receptor 2 (Olfr2) and its human ortholog OR6A2 expressed in macrophages drive NLRP3 inflammasome activation and exacerbate atherosclerosis in mice

Atherosclerosis is an inflammatory disease of the arterial wall driven by macrophages and other immune cells. Olfactory receptors (Olfrs) are G-protein coupled receptors expressed in olfactory epithelium and are responsible for the sense of smell. We found that macrophages in the wall of atherosclerotic mouse aortas express some olfactory receptors including Olfr2, a specific receptor for an 8 carbon fatty-aldehyde called octanal. Octanal is detectable in food, mouse and human blood plasma, elevated by western diet, and partially derived from gut microbiota. Ligation of Olfr2 or its human orthologue OR6A2, expressed in human atherosclerotic plaque and in human monocyte-derived macrophages, is strongly pro-inflammatory, activates the NLRP3 inflammasome and, in synergy with LPS, induces secretion of IL-1β. Knockdown of Olfr2/OR6A2 in macrophages significantly reduced inflammatory cytokine secretion. To test the role of Olfr2 in atherosclerosis, we treated Apoe−/− mice with octanal or the Olfr2 antagonist citral. Octanal significantly exacerbated while citral significantly inhibited atherosclerosis. We generated Olfr2−/− mice by Crispr-Cas9. Ldlr−/− mice reconstituted with Olfr2−/− bone marrow developed ~50% smaller lesions on high cholesterol diet than littermate controls reconstituted with Olfr2+/+ bone marrow. Our findings suggest that small molecule inhibitors of Olfrs like OR6A2 are promising targets for drug development to prevent and treat atherosclerosis-based cardiovascular diseases.

Imaging of the immune system - towards a subcellular and molecular understanding

Immune responses involve many types of leukocytes that traffic to the site of injury, recognize the insult and respond appropriately. Imaging of the immune system involves a set of methods and analytical tools that are used to visualize immune responses at the cellular and molecular level as they occur in real time. We will review recent and emerging technological advances in optical imaging, and their application to understanding the molecular and cellular responses of neutrophils, macrophages and lymphocytes. Optical live-cell imaging provides deep mechanistic insights at the molecular, cellular, tissue and organism levels. Live-cell imaging can capture quantitative information in real time at subcellular resolution with minimal phototoxicity and repeatedly in the same living cells or in accessible tissues of the living organism. Advanced FRET probes allow tracking signaling events in live cells. Light-sheet microscopy allows for deeper tissue penetration in optically clear samples, enriching our understanding of the higher-level organization of the immune response. Super-resolution microscopy offers insights into compartmentalized signaling at a resolution beyond the diffraction limit, approaching single-molecule resolution. This Review provides a current perspective on live-cell imaging in vitro and in vivo with a focus on the assessment of the immune system.

Identification of an Early Unipotent Neutrophil Progenitor with Pro-tumoral Activity in Mouse and Human Bone Marrow

Neutrophils are short-lived cells that play important roles in both health and disease. Neutrophils and monocytes originate from the granulocyte monocyte progenitor (GMP) in bone marrow; however, unipotent neutrophil progenitors are not well defined. Here, we use cytometry by time of flight (CyTOF) and single-cell RNA sequencing (scRNA-seq) methodologies to identify a committed unipotent early-stage neutrophil progenitor (NeP) in adult mouse bone marrow. Importantly, we found a similar unipotent NeP (hNeP) in human bone marrow. Both NeP and hNeP generate only neutrophils. NeP and hNeP both significantly increase tumor growth when transferred into murine cancer models, including a humanized mouse model. hNeP are present in the blood of treatment-naive melanoma patients but not of healthy subjects. hNeP can be readily identified by flow cytometry and could be used as a biomarker for early cancer discovery. Understanding the biology of hNeP should allow the development of new therapeutic targets for neutrophil-related diseases, including cancer.

Bone marrow transplantation rescues monocyte recruitment defect and improves cystic fibrosis in mice

Cystic fibrosis (CF) is an inherited life-threatening disease accompanied by repeated lung infections and multi-organ inflammation that affects tens of thousands of people worldwide. The causative gene, cystic fibrosis transmembrane conductance regulator (CFTR), is mutated in CF patients. Monocytes from CF patients show a deficiency in integrin activation and adhesion. Since monocytes play critical roles in controlling infections, defective monocyte function may contribute to CF progression. In this study, we demonstrate that monocytes from CFTRΔF508 mice (CF mice) show defective adhesion under flow. Transplanting CF mice with wild-type bone marrow after sublethal irradiation replaced most (60–80%) CFmonocytes with wild-type monocytes, significantly improved survival, and reduced inflammation. Wild-type/CFmixed bone marrow chimeras directly demonstrated defective CF monocyte recruitment to the bronchoalveolar lavage and the intestinal lamina propria in vivo. Our findings show that providing wild-type monocytes by bone marrow transfer rescues gastrointestinal (GI) mortality in CF mice, suggesting that wild-type bone marrow stem cells might mitigate CF inflammation.

CD160-HVEM signaling in intestinal epithelial cells modulates gut microbial homeostasis

Intestinal epithelial cells (IEC) are a first barrier that segregates host and commensal bacteria to maintain intestinal homeostasis. Intestinal intraepithelial lymphocytes (IEL) are located beneath or between adjacent IEC and directly contact IEC. The herpes virus entry mediator (HVEM), a member of the tumor necrosis factor receptor superfamily (TNFRSF), is highly expressed by IEC. Epithelial HVEM expression was previously reported as a regulator of innate immune defense during acute infections in the intestine (Shui et al., Nature, 2012). Here, we identify that HVEM signaling in IEC is important for the regulation of the gut microbiota at steady state. Mice with an epithelial-specific deletion of the gene encoding HVEM (HvemΔIEC) had significantly increased segmented filamentous bacteria (SFB) which caused an increase in Th17 cells in the ileum. Treatment with the antibiotic vancomycin eliminated SFB and decreased Th17 cells in HvemΔIEC mice. Additionally, mice with a deletion of the gene encoding CD160, which is a ligand for HVEM and is highly expressed by IEL, including intraepithelial innate lymphoid cells (ILC) and intraepithelial T cells, had increased SFB in the ileum. Our findings suggest that the interaction of CD160 expressed by IEL with HVEM expressed by IEC is important at steady state for shaping the microbiota in the intestine.

LIGHT-HVEM Signaling in Innate Lymphoid Cell Subsets Protects Against Enteric Bacterial Infection

Innate lymphoid cells (ILCs) are important regulators of early infection at mucosal barriers. ILCs are divided into three groups based on expression profiles, and are activated by cytokines and neuropeptides. Yet, it remains unknown if ILCs integrate other signals in providing protection. We show that signaling through herpes virus entry mediator (HVEM), a member of the tumor necrosis factor (TNF) receptor superfamily, in ILC3 is important for host defense against oral infection with the bacterial pathogen Yersinia enterocolitica. HVEM stimulates protective interferon-γ (IFN-γ) secretion from ILCs, and mice with HVEM-deficient ILC3 exhibit reduced IFN-γ production, higher bacterial burdens and increased mortality. In addition, IFN-γ production is critical as adoptive transfer of wild-type but not IFN-γ-deficient ILC3 can restore protection to mice lacking ILCs. We identify the TNF superfamily member, LIGHT, as the ligand inducing HVEM signals in ILCs. Thus HVEM signaling mediated by LIGHT plays a critical role in regulating ILC3-derived IFN-γ production for protection following infection. VIDEO ABSTRACT.

LIGHT-HVEM Signaling in Group3 Innate Lymphoid Cells Protects Against Enteric Bacterial Infection

Innate lymphoid cells (ILC) are important regulators of early infection at mucosal barriers. They are known to be activated by cytokines and neuropeptides, but it remains to be determined if they integrate other signals in providing protection. The herpes virus entry mediator (HVEM), a member of the TNF receptor superfamily, is expressed by all intestinal ILC subsets. Here, we show that HVEM signaling of ILC3 is important for host defense against oral infection with the enteric bacterial pathogen Yersinia enterocolitica (Y. enterocolitica). Surprisingly, IFNγ production by CCR6 negative ILC3 was strongly implicated in protection, likely because these cells were more numerous than other innate lymphocytes that produced IFNγ early after infection. We identified the TNF superfamily member LIGHT, as the ligand inducing HVEM signals in ILC. Therefore, our results demonstrate a novel role for LIGHT-HVEM signaling in regulating ILC3 IFNγ production and protection following infection.

Key role for CD103+ DCs in activating lung iNKT cells during Streptococcus pneumoniae infection

Invariant natural killer T cells (iNKT) are profoundly important for protection against Streptococcus pneumoniae. Prior work has shown iNKT cells are rapidly activated in a CD1d-dependent manner, however the critical antigen presenting cells remain unknown. We have begun to uncover a dominant role for a more recently described iNKT cell subset: NKT17 cells. Within 14 hours of infection, approximately 60% of NKT17 cells have received a TCR signal, and 45% produce IL-17A. Notably, only a minor percentage of NKT1 cells are TCR-activated or produce IFN-γ. Here, by generating conditional CD1d knockout mice, our goal was to determine which cell types directly activate NKT17 cells during infection. In mice with a CD11c+ cell-specific deletion, there was a 50% reduction of IL-17A-producing NKT17 cells at 14 hours, and a significant increase in bacteria loads at 48 hours. While these mice lack CD1d on several cell types, we focused on CD103+ DCs. If CD103+ DCs are absent, mice are highly susceptible to S. pneumoniae infection, iNKT cells do not expand, and IL-17A is diminished. Using confocal and two-photon microscopy of live tissue sections and flow cytometry we investigated their role as APCs. CD103+ DCs engulf a GFP-expressing S. pneumoniae strain within 2 hours and are primarily located within the interstitial lung tissue, notably where most NKT17 cells localize. We next generated a mouse with a CD103+ DC-specific deletion of CD1d. These mice also showed a 50% reduction of IL-17A-producing NKT17 cells at 14 hours and an increase in bacteria loads at 48 hours. Continuing studies include microscopy of live lung sections to further investigate the direct interaction between CD103+ DCs and iNKT cells during S. pneumoniae infection.

Lymphotoxin receptor beta expression by neutrophils is a critical regulator of colitis pathogenesis

Inflammatory bowel disease, while multifactorial, is largely characterized by an exacerbated intestinal immune activation. However, the critical mechanisms regulating immune activation remain to be fully defined. We have previously reported that a member of the TNF superfamily, TNFSF14/LIGHT, is required for prevention of severe disease in a mouse model of dextran sodium sulfate (DSS) induced colitis. Additionally, antibody-mediated blocking of lymphotoxin beta receptor (LTβR), which recognizes LIGHT, also led to exacerbated colitis pathogenesis. Thus, we aimed to determine the cell type(s) and mechanism critical to LTβR mediated exacerbation of DSS driven colitis. Employing the use of LTβRflox/flox mice and appropriate Cre strains, we were able to evaluate the role of LTβR signaling during DSS-induced colitis in a variety of immune and intestinal cell types. For all experiments, body weight, colon length and intestinal histopathology were assessed. These studies revealed that neutrophils were the critical LTβR expressing cell type and that specific deletion of neutrophil LTβR expression, via MRP8 Cre, resulted in exacerbated DSS-induced colitis similar to that in LIGHT−/− mice. RNASeq analysis of neutrophils revealed alterations in cellular metabolism and mitochondrial function, further confirmed through ex vivo analysis of LTβR deficient neutrophils, which had increased mitochondria. In sum, our results demonstrate that neutrophil LTβR activation, likely through LIGHT signaling, plays a critical role in the immune activation associated with DSS-induced colitis.

Structure-function characterization of three human antibodies targeting the vaccinia virus adhesion molecule D8

Vaccinia virus (VACV) envelope protein D8 is one of three glycosaminoglycan adhesion molecules and binds to the linear polysaccharide chondroitin sulfate (CS). D8 is also a target for neutralizing antibody responses that are elicited by the smallpox vaccine, which has enabled the first eradication of a human viral pathogen and is a useful model for studying antibody responses. However, to date, VACV epitopes targeted by human antibodies have not been characterized at atomic resolution. Here, we characterized the binding properties of several human anti-D8 antibodies and determined the crystal structures of three VACV-mAb variants, VACV-66, VACV-138, and VACV-304, separately bound to D8. Although all these antibodies bound D8 with high affinity and were moderately neutralizing in the presence of complement, VACV-138 and VACV-304 also fully blocked D8 binding to CS-A, the low affinity ligand for D8. VACV-138 also abrogated D8 binding to the high-affinity ligand CS-E, but we observed residual CS-E binding was observed in the presence of VACV-304. Analysis of the VACV-138- and VACV-304-binding sites along the CS-binding crevice of D8, combined with different efficiencies of blocking D8 adhesion to CS-A and CS-E allowed us to propose that D8 has a high- and low-affinity CS-binding region within its central crevice. The crevice is amenable to protein engineering to further enhance both specificity and affinity of binding to CS-E. Finally, a wild-type D8 tetramer specifically bound to structures within the developing glomeruli of the kidney, which express CS-E. We propose that through structure-based protein engineering, an improved D8 tetramer could be used as a potential diagnostic tool to detect expression of CS-E, which is a possible biomarker for ovarian cancer.

Rolling neutrophils form tethers and slings under physiologic conditions in vivo

Human and mouse neutrophils are known to form tethers when rolling on selectins in vitro. Tethers are ∼0.2 μm thin, ∼5-10 μm-long structures behind rolling cells that can swing around to form slings that serve as self-adhesive substrates. Here, we developed a mouse intravital imaging method, where the neutrophil surface is labeled by injecting fluorescently labeled mAb to Ly-6G. Venules in the cremaster muscle of live mice were imaged at a high frame rate using a confocal microscope equipped with a fast resonant scanner. We observed 270 tethers (median length 3.5 μm) and 31 slings (median length 6.9 µm) on 186 neutrophils of 15 mice. Out of 199 tether break events, 123 were followed by immediate acceleration of the rolling cell, which shows that tethers are load-bearing structures in vivo. In venules with a high wall shear stress (WSS; > 12 dyn/cm² ), median rolling velocity was higher (19 μm/s), and 43% of rolling neutrophils had visible tethers. In venules with WSS < 12 dyn/cm² , only 26% of rolling neutrophils had visible tethers. We conclude that neutrophil tethers are commonly present and stabilize rolling in vivo.

Scavenger Receptor CD36 Directs Nonclassical Monocyte Patrolling Along the Endothelium During Early Atherogenesis

OBJECTIVE

Nonclassical monocytes (NCM) function to maintain vascular homeostasis by crawling or patrolling along the vessel wall. This subset of monocytes responds to viruses, tumor cells, and other pathogens to aid in protection of the host. In this study, we wished to determine how early atherogenesis impacts NCM patrolling in the vasculature.

APPROACH AND RESULTS

To study the role of NCM in early atherogenesis, we quantified the patrolling behaviors of NCM in ApoE^-/- (apolipoprotein E) and C57BL/6J mice fed a Western diet. Using intravital imaging, we found that NCM from Western diet-fed mice display a 4-fold increase in patrolling activity within large peripheral blood vessels. Both human and mouse NCM preferentially engulfed OxLDL (oxidized low-density lipoprotein) in the vasculature, and we observed that OxLDL selectively induced NCM patrolling in vivo. Induction of patrolling during early atherogenesis required scavenger receptor CD36, as CD36^-/- mice revealed a significant reduction in patrolling activity along the femoral vasculature. Mechanistically, we found that CD36-regulated patrolling was mediated by a SFK (src family kinase) through DAP12 (DNAX activating protein of 12KDa) adaptor protein.

CONCLUSIONS

Our studies show a novel pathway for induction of NCM patrolling along the vascular wall during early atherogenesis. Mice fed a Western diet showed increased NCM patrolling activity with a concurrent increase in SFK phosphorylation. This patrolling activity was lost in the absence of either CD36 or DAP12. These data suggest that NCM function in an atheroprotective manner through sensing and responding to oxidized lipoprotein moieties via scavenger receptor engagement during early atherogenesis.

HVEM expression by intestinal epithelial cells modulates the microbiome and epithelial immunity

The herpes virus entry mediator (HVEM), a member of the tumor necrosis factor receptor superfamily (TNFRSF), is highly expressed by intestinal epithelial cells (IEC). Previously, we reported that HVEM expression by epithelial cells was required for innate immune defense from acute infections in the lung and the intestine (Nature 488:222,2012). Here, we demonstrate a novel, constitutive role of HVEM expression by IEC in microbial homeostasis and epithelial immunity. Mice with an epithelial-specific deletion of the gene encoding HVEM (HvemΔIEC) had significantly increased segmented filamentous bacteria (SFB). This caused an increase in Th17 cells and IL-22+ILC3s in the intestine lamina propria. HvemΔIEC mice also exhibited increased goblet cell hypertrophy and hyperplasia, crypt hyperplasia, villous atrophy as they aged, and they showed a severe defect in fucosylation of cell surface proteins, even at younger ages. Treatment with the antibiotic vancomycin eliminated SFB and decreased Th17 cells and ILC3, but did not reverse the defect in fucosylation. Our findings suggest that epithelial cell expression of HVEM is important at steady state both for shaping the intestinal microbiota and for the homeostasis of IEC in the intestine.

HVEM expression by innate lymphoid cells protects against enteric bacterial infection

Yersinia enterocolitica causes food-borne disease and targets the small intestine, in which ILC3 are the predominant ILC subset. Here we show that ILC3 are required for protection of mice from oral Y. enterocolitica, as mice lacking ILC3 were more susceptible and transfer of ILC to recipients was protective. IFNγ is a cytokine required for host defense from this pathogen, and while ILC in the small intestine did not increase in number they greatly increased IFNγ production after infection. The herpes virus entry mediator (HVEM), a member of the TNF receptor superfamily (TNFRSF), is expressed by all intestinal ILC subsets. Mice with a deficiency of HVEM expression in RORγt+ ILC had a reduced steady-state IL-22 production, and in vitro HVEM could signal to ILC3 to stimulate IL-22 secretion. Moreover, following oral infection with Y. enterocolitica, mice with HVEM deficiency mediated by Rorc-cre showed reduced survival and increased bacterial translocation early after infection. Cytokines are known to induce ILC activation, but our results demonstrate a novel role for the cell surface receptor HVEM in regulating ILC3 cytokine production, both at steady state, and as a critical survival factor during acute infection.

NKT cell subsets involved in host defense from pulmonary Streptococcus pneumoniae infection

Invariant natural killer T cells (iNKT) are a population of innate-like T lymphocytes that have crucial roles in protective responses to infectious agents, particularly Streptococcus pneumoniae. Despite their abundance in the lungs, there is limited understanding of how iNKT cells mediate protection there. Prior work from our group has shown that after pulmonary S. pneumoniae infection, iNKT cells are rapidly activated in a CD1d-dependent manner. Further, others have defined iNKT1, 2, and 17 cell subsets, analogous to CD4+ Th1, Th2, and Th17 subsets. In this study we investigated the roles of lung iNKT cell subsets in protection from S. pneumoniae. In naïve C57BL/6 mouse lungs, we found NKT1 and NKT17 cells were the predominant iNKT cell subsets, with most NKT17 cells in the tissue and NKT1 cells in both the tissue and vasculature. We then utilized fluorescent bacteria, flow cytometry, and intravital microscopy to analyze the lungs during pulmonary infection. At 24 hours, the bacteria localized within the tissue, and were taken up primarily by alveolar macrophages and neutrophils. At 14 and 24 hours, a majority of the lung NKT17 cells were producing IL-17, while only a minor percentage of NKT1 cells were producing IFNγ. This correlated with data from Nur77GFP reporter mice that indicate TCR-mediated activation. At 24 hours, approximately 75% of NKT17 but only 30% of NKT1 cells had been TCR-activated; suggesting NKT17 cells may play a dominant role early in infection. Yet, by 24 hours, NKT1 cells expanded to become the major subset in the lungs, proposing they are also relevant for protection. Experiments are underway to determine when and where subsets are first activated, roles of other cytokines, and consequences of removing individual subsets.

Endothelial Protective Monocyte Patrolling in Large Arteries Intensified by Western Diet and Atherosclerosis

Supplemental Digital Content is available in the text.

Rationale:

Nonclassical mouse monocyte (CX3CR1^high, Ly-6C^low) patrolling along the vessels of the microcirculation is critical for endothelial homeostasis and inflammation. Because of technical challenges, it is currently not established how patrolling occurs in large arteries.

Objective:

This study was undertaken to elucidate the molecular, migratory, and functional phenotypes of patrolling monocytes in the high shear and pulsatile environment of large arteries in healthy, hyperlipidemic, and atherosclerotic conditions.

Methods and Results:

Applying a new method for stable, long-term 2-photon intravital microscopy of unrestrained large arteries in live CX3CR1-GFP (green fluorescent protein) mice, we show that nonclassical monocytes patrol inside healthy carotid arteries at a velocity of 36 μm/min, 3× faster than in microvessels. The tracks are less straight but lead preferentially downstream. The number of patrolling monocytes is increased 9-fold by feeding wild-type mice a Western diet or by applying topical TLR7/8 (Toll-like receptor) agonists. A similar increase is seen in CX3CR1^+/GFP/apoE^−/− mice on chow diet, with a further 2- to 3-fold increase on Western diet (22-fold over healthy). In plaque conditions, monocytes are readily captured onto the endothelium from free flow. Stable patrolling is unaffected in CX3CR1-deficient mice and involves the contribution of LFA-1 (lymphocyte-associated antigen 1) and α₄ integrins. The endothelial damage in atherosclerotic carotid arteries was assessed by electron microscopy and correlates with the number of intraluminal patrollers. Abolishing patrolling monocytes in Nr4a1^−/− apoE^−/− mice leads to pronounced endothelial apoptosis.

Conclusions:

Arterial patrolling is a prominent new feature of nonclassical monocytes with unique molecular and kinetic properties. It is highly upregulated in hyperlipidemia and atherosclerosis in a CX3CR1-independent fashion and plays a potential role in endothelial protection.

Atheroprotective vaccination with MHC-II-restricted ApoB peptides induces peritoneal IL-10-producing CD4 T cells

Although immunization with major histocompatibility complex (MHC) class II-restricted apolipoprotein B (ApoB) peptides has been shown to be atheroprotective, the mechanism is unclear. Here, we investigated CD4⁺ T cell populations in immunized atherosclerotic mice. Peptides (16-mers) from mouse ApoB, the core protein of low-density lipoprotein (LDL), were screened for binding to I-A^b by computer prediction and confirmed by radiolabeled peptide competition. Three new peptides, P101 (FGKQGFFPDSVNKALY, 5.5 nM IC₅₀), P102 (TLYALSHAVNSYFDVD, 6.8 nM), and P103 (LYYKEDKTSLSASAAS, 95 nM), were tested in an atherosclerosis model (Apoe^-/- mice on Western diet). Immunization with each of the three peptides (1 time in complete Freund's adjuvant subcuntaneously and 4 time in incomplete Freund's adjuvant intraperitoneally) but not with adjuvant alone showed significantly reduced atherosclerotic plaques in the aortic root by serial sections and in the whole aorta by en face staining. There were no differences in body weight, LDL cholesterol, or triglycerides. Peritoneal leukocytes from ApoB peptide-immunized mice, but not control mice, secreted significant amounts of IL-10 (150 pg/ml). Flow cytometry showed that peptide immunization induced IL-10 in 10% of peritoneal CD4⁺ T cells, some of which also expressed chemokine (C-C motif) receptor 5 (CCR5). Vaccination with ApoB peptides expanded peritoneal FoxP3⁺ regulatory CD4⁺ T cells and more than tripled the number of CCR5⁺FoxP3⁺ cells. Similar trends were also seen in the draining mediastinal lymph nodes but not in the nondraining inguinal lymph nodes. We conclude that vaccination with MHC class II-restricted autologous ApoB peptides induces regulatory T cells (Tregs) and IL-10, suggesting a plausible mechanism for atheroprotection.NEW & NOTEWORTHY Vaccination against apolipoprotein B (ApoB), the protein of LDL, attracts attention as a novel approach to prevent atherosclerosis. We discovered major histocompatibility complex class II-restricted ApoB peptides, which reduce atherosclerosis and induce IL-10-producing CD4⁺ T cells and chemokine (C-C motif) receptor 5 expression on regulatory T cells, suggesting that immunization with ApoB peptides inhibits atherosclerosis by inducing anti-inflammatory cytokines.

The transcription factor NR4A3 controls CD103+ dendritic cell migration

The transcription factor NR4A3 (also known as NOR-1) is a member of the Nr4a family of nuclear receptors and is expressed in myeloid and lymphoid cells. Here, we have shown that Nr4a3 is essential for the migration of CD103+ dendritic cells (DCs) to lymph nodes (LNs). Nr4a3-deficient mice had very few CD103+ migratory DCs (mDCs) present in LNs, and mixed-chimera studies revealed that this migratory defect was cell intrinsic. We further found that CD103+ DCs from Nr4a3-deficient mice displayed a marked loss of surface expression of the chemokine CCR7. This defect in CCR7 expression was confined to CD103+ DCs, as CCR7 expression on T lymphocytes was unaffected. Moreover, CCR7 was not induced on CD103+ DCs from Nr4a3-deficient mice in response to either administration of the TLR7 agonist R848 or infection with Citrobacter rodentium in vivo. The transcription factor FOXO1 has been shown to regulate CCR7 expression. We found that FOXO1 protein was reduced in Nr4a3-deficient DCs through an AKT-dependent mechanism. Further, we found a requirement for NR4A3 in the maintenance of homeostatic mitochondrial function in CD103+ DCs, although this is likely independent of the NR4A3/FOXO1/CCR7 axis in the regulation of DC migration. Thus, NR4A3 plays an important role in the regulation of CD103+ mDCs by regulating CCR7-dependent cell migration.

Deleting an Nr4a1 Super-Enhancer Subdomain Ablates Ly6Clow Monocytes while Preserving Macrophage Gene Function

Mononuclear phagocytes are a heterogeneous family that occupy all tissues and assume numerous roles to support tissue function and systemic homeostasis. Our ability to dissect the roles of individual subsets is limited by a lack of technologies that ablate gene function within specific mononuclear phagocyte sub-populations. Using Nr4a1-dependent Ly6C^low monocytes, we present a proof-of-principle approach that addresses these limitations. Combining ChIP-seq and molecular approaches we identified a single, conserved, sub-domain within the Nr4a1 enhancer that was essential for Ly6C^low monocyte development. Mice lacking this enhancer lacked Ly6C^low monocytes but retained Nr4a1 gene expression in macrophages during steady state and in response to LPS. Because Nr4a1 regulates inflammatory gene expression and differentiation of Ly6C^low monocytes, decoupling these processes allows Ly6C^low monocytes to be studied independently.

Calcitonin Peptide Family Members Are Differentially Regulated by LPS and Inhibit Functions of Rat Alveolar NR8383 Macrophages

Members of the calcitonin peptide family—calcitonin gene-related peptide (CGRP), adrenomedullin (AM), and adrenomedullin2/intermedin (IMD)–exert modulatory effects upon monocytes and macrophages of various extrapulmonary origins. Utilizing the rat alveolar macrophage (AMφ) cell line NR8383, we here set out to determine to which extent these three peptides and their receptors are differentially regulated in AMφ and what specific effects they have on AMφ key functions. LPS treatment differentially up-regulated expression of the peptides and receptors. Among the three peptides, IMD mRNA content was lowest both in primary rat AMφ and NR8383 cells, whereas IMD peptide dominated in basal and LPS-stimulated secretion from NR8383 cells. Fcγ receptor-mediated phagocytosis and TNF-α production were inhibited by AM, IMD, and CGRP, whereas pro-IL-1β mRNA was slightly down-regulated exclusively by CGRP. Neither of these peptides affected IL-6 or IL-10 production. None increased intracellular calcium concentration, but AM significantly inhibited store-operated calcium entry. In conclusion, the rat AMφ cell line NR8383 is both a source and a target of the calcitonin peptide family members AM, IMD, and CGRP. Despite sharing proteins of the receptor complexes, AM, IMD, and CGRP each showed a characteristic pattern of effects and regulation, suggesting that these closely related peptides are not just redundant members of one common signaling pathway but act in concert by addressing parallel signaling cascades. Since peptide and receptor expression are up-regulated by LPS, these signaling pathways might act as inhibitory feedback mechanisms in pulmonary bacterial infection.

Neutrophil recruitment limited by high-affinity bent β2 integrin binding ligand in cis

Neutrophils are essential for innate immunity and inflammation and many neutrophil functions are β2 integrin-dependent. Integrins can extend (E(+)) and acquire a high-affinity conformation with an 'open' headpiece (H(+)). The canonical switchblade model of integrin activation proposes that the E(+) conformation precedes H(+), and the two are believed to be structurally linked. Here we show, using high-resolution quantitative dynamic footprinting (qDF) microscopy combined with a homogenous conformation-reporter binding assay in a microfluidic device, that a substantial fraction of β2 integrins on human neutrophils acquire an unexpected E(-)H(+) conformation. E(-)H(+) β2 integrins bind intercellular adhesion molecules (ICAMs) in cis, which inhibits leukocyte adhesion in vitro and in vivo. This endogenous anti-inflammatory mechanism inhibits neutrophil aggregation, accumulation and inflammation.