Immunological Niche Research Articles

Dynamic responses of human lung innate and adaptive immune cells highlight the roles of genes at asthma risk loci.

The lung is a unique immunological niche with diverse immune cell types. The effects of stimulation through innate and adaptive immune receptors on human lung immune cells has largely been extrapolated from studies of blood immune cells. While multiple immune cell types and many genes have been implicated as contributing to asthma, the dynamics of these in human lung immune cells following activation will yield insights into asthma pathogenesis and lung immunity more broadly. Human lung immune cells from 6 donors were isolated. Mixed leukocytes were treated separately with lipopolysaccharide (LPS), F(ab)2-anti-human-IgM/IgG + IL4 and anti-CD3/CD28 for 4 and 18 hours and underwent single cell RNA sequencing (scRNAseq). Lung immune cell types were annotated, and gene expression compared across conditions. Genes at prior asthma-associated genetic loci were characterized across cell types, treatments and timepoints. Expression of non-classical class II genes associated with asthma, HLA-DQA2 and HLA-DQB2, and their protein products was characterized with immunohistochemistry. We characterized gene expression in 116,697 lung immune cells. Cell-, treatment-, and timepoint-specific effects on gene expression were detected in all lung immune cell populations. Correlation of gene expression between lung and blood lymphocyte populations decreased following stimulation. Among the genes that were differentially expressed, 97 receptor:ligand pairs had changes with treatments. 96.0% of genes at asthma risk loci demonstrated differential expression in at least one cell type and at least one treatment. B cells were the cell type with the highest expression of HLA-DQA2 and HLA-DQB2 which increased with anti-IgM/IgG treatment and the HLA-DQB2 protein was identified in lung B cells from a donor with asthma. Human lung immune activation elicits a broad range of cellular responses that deviate from those of blood immune cells and are relevant to asthma. Lung B cells expressing HLA-DQA2 and HLA-DQB2 appear to be involved in a novel antigen presentation pathway that contributes to asthma risk.

Polymer scaffolds delineate healthy from diseased states at sites distal from the pancreas in two models of type 1 diabetes.

Type 1 diabetes (T1D) prevention is currently limited by the lack of diagnostic tools able to identify disease before autoimmune destruction of the pancreatic β cells. Autoantibody tests are used to predict risk and, in combination with glucose dysregulation indicative of β cell loss, to determine administration of immunotherapies. Our objective was to remotely identify immune changes associated with the disease, and we have employed a subcutaneously implanted microporous poly(e-caprolactone) (PCL) scaffold to function as an immunological niche (IN) in two models of T1D. Biopsy and analysis of the IN enables disease monitoring using transcriptomic changes at a distal site from autoimmune destruction of the pancreas, thereby gaining cellular level information about disease without the need for a biopsy of the native organ. Using this approach, we identified gene signatures that stratify healthy and diseased mice in both an adoptive transfer model and a spontaneous onset model of T1D. The gene signatures identified herein demonstrate the ability of the IN to identify immune activation associated with diabetes across models.

Generation of an inflammatory niche in an injectable hydrogel depot through recruitment of key immune cells improves efficacy of mRNA vaccines.

Messenger RNA (mRNA) delivered in lipid nanoparticles (LNPs) rose to the forefront of vaccine candidates during the COVID-19 pandemic due in part to scalability, adaptability, and potency. Yet there remain critical areas for improvements of these vaccines in durability and breadth of humoral responses. In this work, we explore a modular strategy to target mRNA/LNPs to antigen presenting cells with an injectable polymer-nanoparticle (PNP) hydrogel depot technology which recruits key immune cells and forms an immunological niche in vivo. We characterize this niche on a single cell level and find it is highly tunable through incorporation of adjuvants like MPLAs and 3M-052. Delivering commercially available SARS-CoV-2 mRNA vaccines in PNP hydrogels improves the durability and quality of germinal center reactions, and the magnitude, breadth, and durability of humoral responses. The tunable immune niche formed within PNP hydrogels effectively skews immune responses based on encapsulated adjuvants, creating opportunities to precisely modulate mRNA/LNP vaccines for various indications from infectious diseases to cancers.

Engineered Immunologic Niche Monitors Checkpoint Blockade Response and Probes Mechanisms of Resistance.

Antibodies to programmed cell death protein1 (anti-PD-1) have become a promising immunotherapy for triple negative breast cancer (TNBC), blocking PD-L1 signaling from pro-tumor cells through T cell PD-1 receptor binding. Nevertheless, only 10-20% of PD-L1+ metastatic TNBC patients who meet criteria benefit from ICB, and biomarkers to predict patient response have been elusive. We have previously developed an immunological niche, consisting of a microporous implant in the subcutaneous space, that supports tissue formation whose immune composition is consistent with that within vital organs. Herein, we investigated dynamic gene expression within this immunological niche to provide biomarkers of response to anti-PD-1. In a 4T1 model of metastatic TNBC, we observed sensitivity and resistance to anti-PD-1 based on primary tumor growth and survival. The niche was biopsied before, during, and after anti-PD-1 therapy, and analyzed for cell types and gene expression indicative of treatment refractivity. Myeloid cell-to-lymphocyte ratios were altered between ICB-sensitivity and resistance. Longitudinal analysis of gene expression implicated dynamic myeloid cell function that stratified sensitivity from resistance. A niche-derived gene signature predicted sensitivity or resistance prior to therapy. Analysis of the niche to monitor immunotherapy response presents a new opportunity to personalize care and investigate mechanisms underlying treatment resistance.

Biomarkers from subcutaneous engineered tissues predict acute rejection of organ allografts.

Invasive graft biopsies assess the efficacy of immunosuppression through lagging indicators of transplant rejection. We report on a microporous scaffold implant as a minimally invasive immunological niche to assay rejection before graft injury. Adoptive transfer of T cells into Rag2-/- mice with mismatched allografts induced acute cellular allograft rejection (ACAR), with subsequent validation in wild-type animals. Following murine heart or skin transplantation, scaffold implants accumulate predominantly innate immune cells. The scaffold enables frequent biopsy, and gene expression analyses identified biomarkers of ACAR before clinical signs of graft injury. This gene signature distinguishes ACAR and immunodeficient respiratory infection before injury onset, indicating the specificity of the biomarkers to differentiate ACAR from other inflammatory insult. Overall, this implantable scaffold enables remote evaluation of the early risk of rejection, which could potentially be used to reduce the frequency of routine graft biopsy, reduce toxicities by personalizing immunosuppression, and prolong transplant life.

An Outbreak of the Monkeypox Virus: An Alert to Mankind

A zoonotic condition known as monkeypox (MPX) is brought on by the monkeypox virus (MPXV), a species of the orthopoxvirus family. It was found in 1958 following an epidemic at a Copenhagen, Denmark, livestock facility. MPX has a clinical appearance that is comparable to smallpox (SPX). Laterit’sfinding, MPXV has shown a tendency to infect and cause disease in a significant number of mammalian animals from all over the world. Traveller’s MPX was exported from African countries (Nigeria) to other regions of the world in 2018 and 2019, respectively, raising concerns that MPXV may have emerged to occupy the ecological and immunological niche left by the smallpox virus (SPXV). MPXV first appeared again in 2017 in Bayelsa state after 39 years with no reported cases in Nigeria. This review's goal is to locate all documented cases of human MPXepidemics and pertinent epidemiological data. We made an effort to gather and discuss in this review all articles that have been written about MPXV infections that have been found experimentally or naturally. We also go through the comparative illness courses and the state of our understanding of the biology of infection, epidemiology, diagnosis, spread, and prevention of MPXV globally, particularly concerning humans. The MPXV is regarded as a high-danger pathogen that roots a disease that is significant for public health. To plan effective preventative, preparedness, and response actions, it is vital to concentrate on developing surveillance capacities that will yield meaningful information.

Meningeal lymphatic vessel crosstalk with central nervous system immune cells in aging and neurodegenerative diseases.

Meningeal lymphatic vessels form a relationship between the nervous system and periphery, which is relevant in both health and disease. Meningeal lymphatic vessels not only play a key role in the drainage of brain metabolites but also contribute to antigen delivery and immune cell activation. The advent of novel genomic technologies has enabled rapid progress in the characterization of myeloid and lymphoid cells and their interactions with meningeal lymphatic vessels within the central nervous system. In this review, we provide an overview of the multifaceted roles of meningeal lymphatic vessels within the context of the central nervous system immune network, highlighting recent discoveries on the immunological niche provided by meningeal lymphatic vessels. Furthermore, we delve into the mechanisms of crosstalk between meningeal lymphatic vessels and immune cells in the central nervous system under both homeostatic conditions and neurodegenerative diseases, discussing how these interactions shape the pathological outcomes. Regulation of meningeal lymphatic vessel function and structure can influence lymphatic drainage, cerebrospinal fluid-borne immune modulators, and immune cell populations in aging and neurodegenerative disorders, thereby playing a key role in shaping meningeal and brain parenchyma immunity.

Role of Microenvironment in Influencing the Activity of CD19 CAR T Cells in B-Cell Precursor Acute Lymphoblastic Leukemia (B-ALL)

Background: As a therapy based on immune cells, CAR T cells treatment elicits an acute response involving both innate and adaptive immunity which is followed by a process of resolution. A major interest is to identify, within the tumor microenvironment (TME), factors that influence the activity and potency of anti-CD19 CAR T cells. The B-ALL TME provides factors that protect leukemia and, conversely, suppress effector T cells. However, studies on the interaction between the bone marrow (BM) TME and CAR T cells are still limited. We hypothesized that the immunological niche of the BM reacts to CAR T-cell-mediated inflammation by modulating the immune response through the activation of inhibitory pathways and molecules. Methods: We conducted an academic phase I/II study (NCT03389035) with donor-derived anti-CD19 CAR T cells generated with Sleeping Beauty transposon (CARCIK-CD19) in B-ALL patients relapsed after alloHSCT. Hematology laboratory data, CAR T,and CD3+ cell kinetics were analyzed in 43 pediatric and adult B-ALL patients who underwent commercial and investigational anti-CD19 CAR T cell treatment. The scRNA-seq libraries of BM samples were generated using Chromium Single Cell 5′ Reagent Kit of the 10x Genomics (v3.1). Validation was performed in 20 pre-/post- CAR-T matched BM samples by a 30-color flow cytometry panel. Results: Following the peak of expansion, CAR T-cell counts decreased in the third and four-week post-infusion. A similar dynamic of expansion and contraction was observed in CD3+ T cells, total white blood cells (WBC), and monocytes, indicating that a widespread resolution of CAR T-driven inflammation occurs during the first month after infusion. Interestingly, the intensity of the response seems to differ depending on the cell product used. To elucidate the mediators involved in the resolution of CAR T-cell-mediated inflammation, the single-cell transcriptome of patients' BM cells at early time points post-CAR T-cell infusion (1-2 months) was compared to pre-treatment samples at the moment of disease relapse and the infusion products. Eighteen sequencing libraries were analyzed, 6 libraries per patient, for a total of 71407 high-quality cells at an average of 65000 reads per cell. Unbiased clustering of BM cells and infusion products was performed by UMAP embedding. Notably, extensive integration of the dataset coming from the individual patients was observed.The more representative clusters were classified into infusion product, CD4 and CD8 endogenous population, B cells, myeloid cells, pDC, NK, and NK-T cells. We observed profound changes in the composition of BM after CAR T cells infusion compared to pre-treatment samples. Complete disappearance of the B cells associated cluster was observed after treatment. CAR T-cell treatment generated a remodeling of the BM microenvironment, with an increase in the myeloid cells (specifically monocytes), NK, NK-T, and exhausted CD8+ T cell populations. After CAR T-cell infusion, myeloid cells displayed a higher resemblance to myeloid-derived suppressor cells (MDSCs). GeneSet Enrichment Analysis (GSEA) showed significant enrichment in pathways associated with immunosuppression both in the myeloid compartment and in endogenous T cells and in CAR T cells. Of note, the genes involved are also strictly correlated to the generation of terminally exhausted T cells and the emergence of MDSCs. Spectral flow cytometry-based experiments validated our observation of an increase of monocytes, MDSC-like cells, NK, NK-T, and CD8 terminal cells. Modeling intercellular communication using NicheNet suggested the induction of immunosuppressive genes in myeloid cells by both CAR T cells and endogenous T cells. Using the same tool with all niches as the sender and T cells as the receiver, we observed that myeloid cells induced significant signaling in both CAR T cells and endogenous T cells. Conclusions: Through sc-RNAseq and spectral flow cytometry, we have characterized changes in the BM TME after CAR T cell therapy. Specifically, CAR T cells-mediated myeloid activation is associated with pathways of immune dysregulation that may dampen CAR T cell expansion and antagonize the effects of the therapy. Furthermore, these data support the hypothesis that transcriptomic interrogation can infer pathways relevant to the communication between CAR T cells and the TME.

Tissue Engineering Scaffolds Remotely Surveil Presymptomatic Allograft Rejection

Abstract As there is no assay to predict the risk of acute cellular allograft rejection (ACAR), clinicians rely on graft biopsy and aggressive, one-size-fits-all immunosuppression. Endomyocardial biopsy (EMB) is a flawed standard for heart transplant surveillance and diagnosing ACAR, as histological evidence of rejection inherently lags behind molecular biomarkers and suffers from variability. Noninvasive alternatives to EMB in ACAR surveillance, including gene profiling and donor-derived cell-free DNA, also measure lagging indicators of ACAR. A minimally invasive surveillance method is urgently needed to quantify early risk of rejection for minimizing biopsy and personalizing immunosuppression. We have developed porous biomaterial “scaffolds” for minimally-invasive sampling. These scaffolds amass immune cells producing biomarkers as an immunological niche. We identified predictive biomarkers of ACAR conserved in both in murine heterotopic heart transplant and skin transplant through the remote scaffold. We identified 43 highly differentially-expressed genes as organ-agnostic biomarkers of T cell-mediated rejection. These novel biomarkers differentiate between pre-symptomatic ACAR and recipients with healthy allografts, without invasive biopsy. Scaffold cell capture technology provides a leading indicator of ACAR by monitoring tissue-specific immune responses associated with allograft rejection. This implantable scaffold enables minimally invasive histological evaluation and molecular calculation of the early risk of rejection to reduce the frequency of routine EMB and personalize immune suppression that could prolong transplant life while minimizing risk. Supported by the Falk Medical Research Trust Catalyst Award and Transformational Award

Age-dependent Pdgfrβ signaling drives adipocyte progenitor dysfunction to alter the beige adipogenic niche in male mice

Perivascular adipocyte progenitor cells (APCs) can generate cold temperature-induced thermogenic beige adipocytes within white adipose tissue (WAT), an effect that could counteract excess fat mass and metabolic pathologies. Yet, the ability to generate beige adipocytes declines with age, creating a key challenge for their therapeutic potential. Here we show that ageing beige APCs overexpress platelet derived growth factor receptor beta (Pdgfrβ) to prevent beige adipogenesis. We show that genetically deleting Pdgfrβ, in adult male mice, restores beige adipocyte generation whereas activating Pdgfrβ in juvenile mice blocks beige fat formation. Mechanistically, we find that Stat1 phosphorylation mediates Pdgfrβ beige APC signaling to suppress IL-33 induction, which dampens immunological genes such as IL-13 and IL-5. Moreover, pharmacologically targeting Pdgfrβ signaling restores beige adipocyte development by rejuvenating the immunological niche. Thus, targeting Pdgfrβ signaling could be a strategy to restore WAT immune cell function to stimulate beige fat in adult mammals.

Labour promotes systemic mobilisation of monocytes, T cell activation and local secretion of chemotactic factors in the intervillous space of the placenta.

During pregnancy, maternal blood circulates through the intervillous space of the placenta and the reciprocal interactions between foetal tissues and maternal immune cells makes the intervillous space a unique immunological niche. Labour is characterised by a proinflammatory response in the myometrium, but the relationship between local and systemic changes during the onset of labour remains elusive. We here aimed to investigate how the systemic and intervillous circulatory systems are affected during labour from an immunological point of view. We report that the proportion of monocytes is dramatically higher in peripheral (PB), intervillous blood (IVB) and decidua in labouring (n = 14) compared to non-labouring women (n = 15), suggesting that labour leads to both a systemic and local mobilisation of monocytes. Labour was associated with a relative increase of effector memory T cells in the intervillous space compared to the periphery, and MAIT cells and T cells showed an elevated expression of activation markers both in PB and IVB. Intervillous monocytes consisted to a higher degree of CD14+CD16+ intermediate monocytes compared to peripheral monocytes, independently of mode of delivery, and displayed an altered phenotypic expression pattern. A proximity extension assay analysis of 168 proteins revealed that several proteins associated to myeloid cell migration and function, including CCL2 and M-CSF, were upregulated in IVB plasma in labouring women. Thus, the intervillous space could be a bridging site for the communication between the placenta and the periphery, which contribute to monocyte mobilisation and generation of inflammatory reactions during spontaneous labour.

Muscle and Muscle-like Autoantigen Expression in Myasthenia Gravis Thymus: Possible Molecular Hint for Autosensitization

The thymus is widely recognized as an immunological niche where autoimmunity against the acetylcholine receptor (AChR) develops in myasthenia gravis (MG) patients, who mostly present thymic hyperplasia and thymoma. Thymoma-associated MG is frequently characterized by autoantibodies to the muscular ryanodine receptor 1 (RYR1) and titin (TTN), along with anti-AChR antibodies. By real-time PCR, we analyzed muscle-CHRNA1, RYR1, and TTN-and muscle-like-NEFM, RYR3 and HSP60-autoantigen gene expression in MG thymuses with hyperplasia and thymoma, normal thymuses and non-MG thymomas, to check for molecular changes potentially leading to an altered antigen presentation and autoreactivity. We found that CHRNA1 (AChR-α subunit) and AIRE (autoimmune regulator) genes were expressed at lower levels in hyperplastic and thymoma MG compared to the control thymuses, and that the RYR1 and TTN levels were decreased in MG versus the non-MG thymomas. Genes encoding autoantigens that share epitopes with AChR-α (NEFM and HSP60), RYR1 (neuronal RYR3), and TTN (NEFM) were up-regulated in thymomas versus hyperplastic and control thymuses, with distinct molecular patterns across the thymoma histotypes that could be relevant for autoimmunity development. Our findings support the idea that altered muscle autoantigen expression, related with hyperplastic and neoplastic changes, may favor autosensitization in the MG thymus, and that molecular mimicry involving tumor-related muscle-like proteins may be a mechanism that makes thymoma prone to developing MG.

Increasing serum antibodies against type B influenza virus in 2017–2018 winter in Beijing, China

Influenza B virus circulates yearly with lower activity than that of influenza A virus in China. During winter 2017 to 2018, a sharp surge of influenza activity dominated by type B/Yamagata lineage virus caused unprecedented medical burden in Beijing. This research aimed to understand the underlying mechanism for this circulation and prepare for epidemics in the future. Sera samples collected from the patients in 2016–2017 and 2017–2018 flu seasons were tested for profiling hemagglutinin inhibition (HI) antibodies against both prevailing Victoria and Yamagata lineages of type B influenza viruses. It showed that the seroprevalence against both lineages of the virus in 2017–2018 winter was higher than that in 2016–2017, while no difference of the seroprevalence was observed between the two viruses. Meanwhile, significant elevated geometric mean titer (GMT) against both lineages of influenza B viruses was found in the specimens collected during 2017–2018 flu season than that from 2016 to 2017, suggesting the viruses might undergo antigenic changes. These results also suggested that lower GMT against both type B variants in 2016–2017 might serve as an immunological niche for the dominating of B/Yamagata virus in China during 2017–2018 winter season. Our findings have implication that there was a significantly elevation of HI antibodies to influenza viruses B in 2017–2018 than in 2016–2017. On the other hand, the low level of HI antibodies to both B/Y and B/V in 2016–2017 could contribute to the severe B/Y epidemic in 2017–2018 to some extent.

Spatial modeling and ecological suitability of monkeypox disease in Southern Nigeria.

The reemergence of monkeypoxvirus (MPXV) in 2017 after about 39 years of no reported cases in Nigeria, and the recent incidence in countries such as the United States of America, United Kingdom, Singapore, and Israel which have been reportedly linked with travelers from Africa, have heightened concern that MPXV may have emerged to occupy the vacant ecological and immunological niche created by the extinct smallpox virus. This study was carried out to identify environmental conditions and areas that are environmentally suitable (risky areas) for MPXV in southern Nigeria. One hundred and sixteen (116) spatially unique MPXV occurrence data from 2017–2021 and corresponding environmental variables were spatially modeled by a maximum entropy algorithm to evaluate the contribution of the variables to the distribution of the viral disease. A variance inflation analysis was adopted to limit the number of environmental variables and minimize multicollinearity. The five variables that contributed to the suitability model for MPXV disease are precipitation of driest quarter (47%), elevation (26%), human population density (17%), minimum temperature in December (7%), and maximum temperature in March (3%). For validation, our model had a high AUC value of 0.92 and standard deviation of 0.009 indicating that it had excellent ability to predict the suitable areas for monkeypox disease. Categorized risk classes across southern states was also identified. A total of eight states were predicted to be at high risk of monkeypox outbreak occurrence. These findings can guide policymakers in resources allocation and distribution to effectively implement targeted control measures for MPXV outbreaks in southern Nigeria.

3D structures inferred from cDNA clones identify the CD1D-Restricted γδ T cell receptor in dromedaries.

The Camelidae species occupy an important immunological niche within the humoral as well as cell mediated immune response. Although recent studies have highlighted that the somatic hypermutation (SHM) shapes the T cell receptor gamma (TRG) and delta (TRD) repertoire in Camelus dromedarius, it is still unclear how γδ T cells use the TRG/TRD receptors and their respective variable V-GAMMA and V-DELTA domains to recognize antigen in an antibody-like fashion. Here we report about 3D structural analyses of the human and dromedary γδ T cell receptor. First, we have estimated the interaction energies at the interface within the human crystallized paired TRG/TRD chains and quantified interaction energies within the same human TRG/TRD chains in complex with the CD1D, an RPI-MH1-LIKE antigen presenting glycoprotein. Then, we used the human TRG/TRD-CD1D complex as template for the 3D structure of the dromedary TRG/TRD-CD1D complex and for guiding the 3D human/dromedary comparative analysis. The choice of mutated TRG alternatively combined with mutated TRD cDNA clones originating from the spleen of one single dromedary was crucial to quantify the strength of the interactions at the protein-protein interface between the paired C. dromedarius TRG and TRD V-domains and between the C. dromedarius TRG/TRD V-domains and CD1D G-domains. Interacting amino acids located in the V-domain Complementarity Determining Regions (CDR) and Framework Regions (FR) according to the IMGT unique numbering for V-domains were identified. The resulting 3D dromedary TRG V-GAMMA combined with TRD V-DELTA protein complexes allowed to deduce the most stable gamma/delta chains pairings and to propose a candidate CD1D-restricted γδ T cell receptor complex.

The type 1 diabetes immune niche: Immunomodulatory biomaterial design considerations for beta cell transplant therapies

Islet transplantation is a promising therapy for a subset of people with Type 1 diabetes (T1D). However, beta cell transplant clinical trials have largely failed to maintain long-term normal glycemia in transplant recipients. This is broadly due to immune rejection of the transplanted islets themselves or the devices in which these cells are encapsulated. As an autoimmune condition, the T1D host presents a uniquely challenging immunological niche for the transplant of additional beta cells. An understanding of the autoimmune environment is crucial for the development of successful beta cell transplant therapies. Here, we provide an overview of the immune cell pathways leading to autoimmune T1D, and the resulting immune niche. Next, we examine biomaterial platforms that can be used for cell transplantation, and describe those that seek to modulate the immune environment to mitigate immune rejection. These approaches include delivery of localized immune cues, co-transplantation with immunomodulatory cells, strategies to engineer islets ex-vivo, and antigen-specific immunomodulation to generate operational tolerance. Finally, we describe therapies which seek to prevent T1D progression which could be repurposed to support beta cell transplantation and future immunoengineering design considerations for successful islet transplantation therapies.

Comprehensive Analysis of Disease Pathology in Immunocompetent and Immunocompromised Hosts following Pulmonary SARS-CoV-2 Infection.

The Coronavirus disease 2019 (COVID-19) pandemic disproportionately affects immunocompetent and immunocompromised individuals, with the latter group being more vulnerable to severe disease and death. However, the differential pathogenesis of SARS-CoV-2 in the context of a specific immunological niche remains unknown. Similarly, systematic analysis of disease pathology in various extrapulmonary organs in immunocompetent and immunocompromised hosts during SARS-CoV-2 infection is not fully understood. We used a hamster model of SARS-CoV-2 infection, which recapitulates the pathophysiology of patients with mild-to-moderate COVID-19, to determine the dynamics of SARS-CoV-2 replication and histopathology at organ-level niches and map how COVID-19 symptoms vary in different immune contexts. Hamsters were intranasally infected with low (LD) or high (HD) inoculums of SARS-CoV-2, and the kinetics of disease pathology and viral load in multiple organs, antibody response, inflammatory cytokine expression, and genome-wide lung transcriptome by RNAseq analysis were determined and compared against corresponding responses from chemically induced immunocompromised hamsters. We observed transient body weight loss proportional to the SARS-CoV-2 infectious dose in immunocompetent hamsters. The kinetics of viral replication and peak viral loads were similar between LD and HD groups, although the latter developed more severe disease pathology in organs. Both groups generated a robust serum antibody response. In contrast, infected immunocompromised animals showed more prolonged body weight loss and mounted an inadequate SARS-CoV-2-neutralizing antibody response. The live virus was detected in the pulmonary and extrapulmonary organs for extended periods. These hamsters also had persistent inflammation with severe bronchiolar-alveolar hyperplasia/metaplasia. Consistent with the differential disease presentation, distinct changes in inflammation and immune cell response pathways and network gene expression were seen in the lungs of SARS-CoV-2-infected immunocompetent and immunocompromised animals.

The Crosstalk between Gut Microbiota, Intestinal Immunological Niche and Visceral Adipose Tissue as a New Model for the Pathogenesis of Metabolic and Inflammatory Diseases: The Paradigm of Type 2 Diabetes Mellitus.

Gut microbiota (GM) comprises more than one thousand microorganisms between bacterial species, viruses, fungi, and protozoa and represents the main actor of a wide net of molecular interactions, involving, among others, the endocrine system, immune responses, and metabolism. GM influences many endocrine functions, such as adrenal steroidogenesis, thyroid function, sexual hormones, IGF-1 pathway and peptides, produced in the gastrointestinal system. It is fundamental in glycaemic control and obesity, while also exerting an important function in modulating the immune system and associated inflammatory disease. The result of this crosstalk in gut mucosa is the formation of the intestinal immunological niche. Visceral adipose tissue (VAT) produces about 600 different peptides and it is involved in lipid and glucose metabolism, and some immune reactions, through several adipokines. GM and VAT interact in a bidirectional fashion: while gut dysbiosis can modify VAT adipokines and hormone secretion, VAT hyperplasia modifies GM composition. Acquired or genetic factors leading to gut dysbiosis or increasing VAT (i.e., Western diet) induce a pro-inflammatory condition, which plays a pivotal role in the development of dysmetabolic and immunologic conditions, such as diabetes mellitus. Diabetes is associated with specific patterns of GM alterations, an abundance or reduction of GM species involved in controlling mucosal barrier status, glycaemic levels and exerting a pro- or anti-inflammatory activity. All these factors could explain the higher incidence of several inflammatory conditions in Western countries; furthermore, besides the specific alterations observed in diabetes, this paradigm could represent a common pathway acting in many metabolic conditions and could pave the way to new, interesting therapeutic approaches.

Skeletal muscle provides the immunological micro-milieu for specific plasma cells in anti-synthetase syndrome-associated myositis

Anti-synthetase syndrome (ASyS)-associated myositis is a major subgroup of the idiopathic inflammatory myopathies (IIM) and is characterized by disease chronicity with musculoskeletal, dermatological and pulmonary manifestations. One of eight autoantibodies against the aminoacyl-transferase RNA synthetases (ARS) is detectable in the serum of affected patients. However, disease-specific therapeutic approaches have not yet been established.To obtain a deeper understanding of the underlying pathogenesis and to identify putative therapeutic targets, we comparatively investigated the most common forms of ASyS associated with anti-PL-7, anti-PL-12 and anti-Jo-1. Our cohort consisted of 80 ASyS patients as well as healthy controls (n = 40), diseased controls (n = 40) and non-diseased controls (n = 20). We detected a reduced extent of necrosis and regeneration in muscle biopsies from PL-12+ patients compared to Jo-1+ patients, while PL-7+ patients had higher capillary dropout in biopsies of skeletal muscle. Aside from these subtle alterations, no significant differences between ASyS subgroups were observed. Interestingly, a tissue-specific subpopulation of CD138+ plasma cells and CXCL12+/CXCL13+CD20+ B cells common to ASyS myositis were identified. These cells were localized in the endomysium associated with alkaline phosphatase+ activated mesenchymal fibroblasts and CD68+MHC-II+CD169+ macrophages. An MHC-I+ and MHC-II+ MxA negative type II interferon-driven milieu of myofiber activation, topographically restricted to the perifascicular area and the adjacent perimysium, as well as perimysial clusters of T follicular helper cells defined an extra-medullary immunological niche for plasma cells and activated B cells. Consistent with this, proteomic analyses of muscle tissues from ASyS patients demonstrated alterations in antigen processing and presentation. In-depth immunological analyses of peripheral blood supported a B-cell/plasma-cell-driven pathology with a shift towards immature B cells, an increase of B-cell-related cytokines and chemokines, and activation of the complement system. We hypothesize that a B-cell-driven pathology with the presence and persistence of a specific subtype of plasma cells in the skeletal muscle is crucially involved in the self-perpetuating chronicity of ASyS myositis. This work provides the conceptual framework for the application of plasma-cell-targeting therapies in ASyS myositis.

SiRNA against CD40 delivered via a fungal recognition receptor ameliorates murine acute graft-versus-host disease.

Acute graft‐versus‐host disease (aGvHD) remains a major threat to a successful outcome after allogeneic hematopoietic stem cell transplantation (HSCT). Although antibody‐based targeting of the CD40/CD40 ligand costimulatory pathway can prevent aGvHD, side effects hampered their clinical application, prompting a need for other ways to interfere with this important dendritic T‐cell costimulatory pathway. Here, we used small interfering RNA (siRNA) complexed with β‐glucan allowing the binding and uptake of the siRNA/β‐glucan complex (siCD40/schizophyllan [SPG]; chemical modifications called NJA‐312, NJA‐302, and NJA‐515) into Dectin1+ cells, which recognize this pathogen‐associated molecular pattern receptor. aGvHD was induced by the transplantation of splenocytes and bone marrow cells from C57BL/6J into CBF1 mice. Splenic dendritic cells retained Dectin1 expression after HSCT but showed lower expression after irradiation. The administration of siCD40/SPG, NJA‐312, and NJA‐302 ameliorated aGvHD‐mediated lethality and tissue damage of spleen and liver, but not skin. Multiple NJA‐312high injections prevented aGvHD but resulted in early weight loss in allogeneic HSCT mice. In addition, NJA‐312 treatment caused delayed initial donor T and B‐cell recovery but resulted in stable chimerism in surviving mice. Mechanistically, NJA‐312 reduced organ damage by suppressing CCR2+, F4/80+, and IL17A‐expressing cell accumulation in spleen, liver, and thymus but not the skin of mice with aGvHD. Our work demonstrates that siRNA targeting of CD40 delivered via the PAMP‐recognizing lectin Dectin1 changes the immunological niche, suppresses organ‐specific murine aGvHD, and induces immune tolerance after organ transplantation. Our work charts future directions for therapeutic interventions to modulate tissue‐specific immune reactions using Pathogen‐associated molecular pattern (PAMP) molecules like 1,3‐β‐glucan for cell delivery of siRNA.