SARS-CoV-2 infection triggers profibrotic macrophage responses and lung fibrosis.

COVID-19-induced "acute respiratory distress syndrome" (ARDS) is associated with prolonged respiratory failure and high mortality, but the mechanistic basis of lung injury remains incompletely understood. Here, we analyze pulmonary immune responses and lung pathology in two cohorts of patients with COVID-19 ARDS using functional single-cell genomics, immunohistology, and electron microscopy. We describe an accumulation of CD163-expressing monocyte-derived macrophages that acquired a profibrotic transcriptional phenotype during COVID-19 ARDS. Gene set enrichment and computational data integration revealed a significant similarity between COVID-19-associated macrophages and profibrotic macrophage populations identified in idiopathic pulmonary fibrosis. COVID-19 ARDS was associated with clinical, radiographic, histopathological, and ultrastructural hallmarks of pulmonary fibrosis. Exposure of human monocytes to SARS-CoV-2, but not influenza A virus or viral RNA analogs, was sufficient to induce a similar profibrotic phenotype in vitro. In conclusion, we demonstrate that SARS-CoV-2 triggers profibrotic macrophage responses and pronounced fibroproliferative ARDS.

Untimely TGFß responses in COVID-19 limit antiviral functions of NK cells.

SARS-CoV-2 is a single-stranded RNA virus that causes COVID-19. Given its acute and often self-limiting course, it is likely that components of the innate immune system play a central part in controlling virus replication and determining clinical outcome. Natural killer (NK) cells are innate lymphocytes with notable activity against a broad range of viruses, including RNA viruses1,2. NK cell function may be altered during COVID-19 despite increased representation of NK cells with an activated and adaptive phenotype3,4. Here we show that a decline in viral load in COVID-19 correlates with NK cell status and that NK cells can control SARS-CoV-2 replication by recognizing infected target cells. In severe COVID-19, NK cells show defects in virus control, cytokine production and cell-mediated cytotoxicity despite high expression of cytotoxic effector molecules. Single-cell RNA sequencing of NK cells over the time course of the COVID-19 disease spectrum reveals a distinct gene expression signature. Transcriptional networks of interferon-driven NK cell activation are superimposed by a dominant transforming growth factor-ß (TGFß) response signature, with reduced expression of genes related to cell-cell adhesion, granule exocytosis and cell-mediated cytotoxicity. In severe COVID-19, serum levels of TGFß peak during the first two weeks of infection, and serum obtained from these patients severely inhibits NK cell function in a TGFß-dependent manner. Our data reveal that an untimely production of TGFß is a hallmark of severe COVID-19 and may inhibit NK cell function and early control of the virus.

MET receptor serves as a promising target in melanoma brain metastases.

The development of brain metastases hallmarks disease progression in 20-40% of melanoma patients and is a serious obstacle to therapy. Understanding the processes involved in the development and maintenance of melanoma brain metastases (MBM) is critical for the discovery of novel therapeutic strategies. Here, we generated transcriptome and methylome profiles of MBM showing high or low abundance of infiltrated Iba1high tumor-associated microglia and macrophages (TAMs). Our survey identified potential prognostic markers of favorable disease course and response to immune checkpoint inhibitor (ICi) therapy, among them APBB1IP and the interferon-responsive gene ITGB7. In MBM with high ITGB7/APBB1IP levels, the accumulation of TAMs correlated significantly with the immune score. Signature-based deconvolution of MBM via single sample GSEA revealed enrichment of interferon-response and immune signatures and revealed inflammation, stress and MET receptor signaling. MET receptor phosphorylation/activation maybe elicited by inflammatory processes in brain metastatic melanoma cells via stroma cell-released HGF. We found phospho-METY1234/1235 in a subset of MBM and observed a marked response of brain metastasis-derived cell lines (BMCs) that lacked druggable BRAF mutations or developed resistance to BRAF inhibitors (BRAFi) in vivo to MET inhibitors PHA-665752 and ARQ197 (tivantinib). In summary, the activation of MET receptor in brain colonizing melanoma cells by stromal cell-released HGF may promote tumor self-maintenance and expansion and might counteract ICi therapy. Therefore, therapeutic targeting of MET possibly serves as a promising strategy to control intracranial progressive disease and improve patient survival.

Human lungs show limited permissiveness for SARS-CoV-2 due to scarce ACE2 levels but virus-induced expansion of inflammatory macrophages.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilises the angiotensin-converting enzyme 2 (ACE2) transmembrane peptidase as cellular entry receptor. However, whether SARS-CoV-2 in the alveolar compartment is strictly ACE2-dependent and to what extent virus-induced tissue damage and/or direct immune activation determines early pathogenesis is still elusive. METHODS: Spectral microscopy, single-cell/-nucleus RNA sequencing or ACE2 "gain-of-function" experiments were applied to infected human lung explants and adult stem cell derived human lung organoids to correlate ACE2 and related host factors with SARS-CoV-2 tropism, propagation, virulence and immune activation compared to SARS-CoV, influenza and Middle East respiratory syndrome coronavirus (MERS-CoV). Coronavirus disease 2019 (COVID-19) autopsy material was used to validate ex vivo results. RESULTS: We provide evidence that alveolar ACE2 expression must be considered scarce, thereby limiting SARS-CoV-2 propagation and virus-induced tissue damage in the human alveolus. Instead, ex vivo infected human lungs and COVID-19 autopsy samples showed that alveolar macrophages were frequently positive for SARS-CoV-2. Single-cell/-nucleus transcriptomics further revealed nonproductive virus uptake and a related inflammatory and anti-viral activation, especially in "inflammatory alveolar macrophages", comparable to those induced by SARS-CoV and MERS-CoV, but different from NL63 or influenza virus infection. CONCLUSIONS: Collectively, our findings indicate that severe lung injury in COVID-19 probably results from a macrophage-triggered immune activation rather than direct viral damage of the alveolar compartment.

Successful plasmapheresis and immunoglobulin treatment for severe lipid storage myopathy: Doing the right thing for the wrong reason.

Three consecutive skeletal muscle biopsies during a several months time-frame, showing different degrees of neutral lipid storage. This is highlighted by Oil-red-O stains (D, E, F) and electron microscopy (G, H, I). Note the impact on mitochondrial morphology with so called 'parking lots (K, L). Zooming 'in and out' into the ultrastructure, using the nanotomy platform provides interesting detailled information (http://nanotomy.org). ​.

Microglia/macrophages express alternative proangiogenic factors depending on granulocyte content in human glioblastoma.

Myeloid cells are an inherent part of the microenvironment of glioblastoma multiforme (GBM). There is growing evidence for their participation in mechanisms of tumor escape, especially in the development of resistance following initially promising anti-VEGF/VEGFR treatment. Thus, we sought to define the capability of myeloid cells to contribute to the expression of proangiogenic molecules in human GBM. We investigated GBM specimens in comparison with anaplastic astrocytoma (WHO grade III) and epilepsy patient samples freshly obtained from surgery. Flow cytometric analyses revealed two distinct CD11b+ CD45+ cell populations in GBM tissues, which were identified as microglia/macrophages and granulocytes. Due to varied granulocyte influx, GBM samples were subdivided into groups with low (GBM-lPMNL) and high (GBM-hPMNL) numbers of granulocytes (polymorphonuclear leukocytes; PMNL), which were related to activation of the microglia/macrophage population. Microglia/macrophages of the GBM-lPMNL group were similar to those of astrocytoma specimens, but those of GBM-hPMNL tissues revealed an altered phenotype by expressing high levels of CD163, TIE2, HIF1α, VEGF, CXCL2 and CD13. Although microglia/macrophages represented the main source of alternative proangiogenic factors, additionally granulocytes participated by production of IL8 and CD13. Moreover, microglia/macrophages of the GBM-hPMNL specimens were highly associated with tumor blood vessels, accompanied by remodeling of the vascular structure. Our data emphasize that tumor-infiltrating myeloid cells might play a crucial role for limited efficacy of anti-angiogenic therapy bypassing VEGF-mediated pathways through expression of alternative proangiogenic factors. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Apelin Controls Angiogenesis-Dependent Glioblastoma Growth.

Glioblastoma (GBM) present with an abundant and aberrant tumor neo-vasculature. While rapid growth of solid tumors depends on the initiation of tumor angiogenesis, GBM also progress by infiltrative growth and vascular co-option. The angiogenic factor apelin (APLN) and its receptor (APLNR) are upregulated in GBM patient samples as compared to normal brain tissue. Here, we studied the role of apelin/APLNR signaling in GBM angiogenesis and growth. By functional analysis of apelin in orthotopic GBM mouse models, we found that apelin/APLNR signaling is required for in vivo tumor angiogenesis. Knockdown of tumor cell-derived APLN massively reduced the tumor vasculature. Additional loss of the apelin signal in endothelial tip cells using the APLN-knockout (KO) mouse led to a further reduction of GBM angiogenesis. Direct infusion of the bioactive peptide apelin-13 rescued the vascular loss-of-function phenotype specifically. In addition, APLN depletion massively reduced angiogenesis-dependent tumor growth. Consequently, survival of GBM-bearing mice was significantly increased when APLN expression was missing in the brain tumor microenvironment. Thus, we suggest that targeting vascular apelin may serve as an alternative strategy for anti-angiogenesis in GBM.

CD171- and GD2-specific CAR-T cells potently target retinoblastoma cells in preclinical in vitro testing.

BACKGROUND: Chimeric antigen receptor (CAR)-based T cell therapy is in early clinical trials to target the neuroectodermal tumor, neuroblastoma. No preclinical or clinical efficacy data are available for retinoblastoma to date. Whereas unilateral intraocular retinoblastoma is cured by enucleation of the eye, infiltration of the optic nerve indicates potential diffuse scattering and tumor spread leading to a major therapeutic challenge. CAR-T cell therapy could improve the currently limited therapeutic strategies for metastasized retinoblastoma by simultaneously killing both primary tumor and metastasizing malignant cells and by reducing chemotherapy-related late effects. METHODS: CD171 and GD2 expression was flow cytometrically analyzed in 11 retinoblastoma cell lines. CD171 expression and T cell infiltration (CD3+) was immunohistochemically assessed in retrospectively collected primary retinoblastomas. The efficacy of CAR-T cells targeting the CD171 and GD2 tumor-associated antigens was preclinically tested against three antigen-expressing retinoblastoma cell lines. CAR-T cell activation and exhaustion were assessed by cytokine release assays and flow cytometric detection of cell surface markers, and killing ability was assessed in cytotoxic assays. CAR constructs harboring different extracellular spacer lengths (short/long) and intracellular co-stimulatory domains (CD28/4-1BB) were compared to select the most potent constructs. RESULTS: All retinoblastoma cell lines investigated expressed CD171 and GD2. CD171 was expressed in 15/30 primary retinoblastomas. Retinoblastoma cell encounter strongly activated both CD171-specific and GD2-specific CAR-T cells. Targeting either CD171 or GD2 effectively killed all retinoblastoma cell lines examined. Similar activation and killing ability for either target was achieved by all CAR constructs irrespective of the length of the extracellular spacers and the co-stimulatory domain. Cell lines differentially lost tumor antigen expression upon CAR-T cell encounter, with CD171 being completely lost by all tested cell lines and GD2 further down-regulated in cell lines expressing low GD2 levels before CAR-T cell challenge. Alternating the CAR-T cell target in sequential challenges enhanced retinoblastoma cell killing. CONCLUSION: Both CD171 and GD2 are effective targets on human retinoblastoma cell lines, and CAR-T cell therapy is highly effective against retinoblastoma in vitro. Targeting of two different antigens by sequential CAR-T cell applications enhanced tumor cell killing and preempted tumor antigen loss in preclinical testing.

P2Y12 receptor is expressed on human microglia under physiological conditions throughout development and is sensitive to neuroinflammatory diseases.

Microglia are resident immune cells in the central nervous system (CNS), which are essential for immune defence and critically contribute to neuronal functions during homeostasis. Until now, little is known about microglia biology in humans in part due to the lack of microglia-specific markers. We therefore investigated the expression of the purinergic receptor P2Y12 in human brain tissue. Compared to classical markers used to identify microglia such as Iba1, CD68 or MHCII, we found that P2Y12 is expressed on parenchymal microglia but is absent from perivascular or meningeal macrophages. We further demonstrate that P2Y12 expression is stable throughout human brain development, including fetal phases, and quantification of P2 Y12+ microglia revealed that the density of human microglia is constant throughout lifetime. In contrast, CD68 expression increases during aging in cerebellar but not in cortical microglia, indicating regional heterogeneity. CNS pathologies such as Alzheimer's disease or multiple sclerosis-but not schizophrenia-result in decreased P2Y12 immunoreactivity in plaque- or lesion-associated myeloid cells, whereas Iba1 expression remains detectable. Our results suggest that P2Y12 is a useful marker for the identification of human microglia throughout the lifespan. Moreover, P2Y12 expression might help to discriminate activated microglia and infiltrating myeloid cells from quiescent microglia in the human CNS. GLIA 2017;65:375-387.

Human NCL Neuropathology.

The neuronal ceroid lipofuscinoses (NCL) currently encompass fourteen genetically different forms, CLN1 to CLN14, but are all morphologically marked by loss of nerve cells, particularly in the cerebral and cerebellar cortices, and the cerebral and extracerebral formation of lipopigments. These lipopigments show distinct ultrastructural patterns, i.e., granular, curvilinear/rectilinear and fingerprint profiles. They contain-although to a different degree among the different CLN forms-subunit C of ATP synthase, saposins A and D, and beta-amyloid proteins. Extracerebral pathology, apart from lipopigment formation, which provides diagnostic information, is scant or non-existent. The retina undergoes atrophy in all childhood forms. While many new data and findings have been obtained by immunohistochemistry in mouse and other animal models, similar findings in human NCL are largely missing, thus recommending respective studies of archived brain tissues. The newly described NCL forms, i.e., CLN 10 to CLN 14, also require further studies to provide complete neuropathology. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

The evolution of the anaplastic cerebellar liponeurocytoma: case report and review of the literature.

Cerebellar liponeurocytoma, first recognized as a distinct entity in the revised WHO classification of Tumors of the Central Nervous System in 2000, is a rare tumor with characteristic histological features and predominant location in the cerebellum. The proliferative index is usually low, and previous reports supported a favorable prognosis. We report a case of a second recurrence of a cerebellar liponeurocytoma with increased proliferative and mitotic activity in which extensive immunohistochemical characterization and genetic profiling were performed. The tumor specimen was characterized in terms of genetic changes frequently associated with gliomas and medulloblastomas. Considering the low number of reported cases, the prognosis of cerebellar liponeurocytoma seems difficult to assess. Our case suggests the existence of different histological grades of cerebellar liponeurocytoma and its possible progression towards a dedifferentiated, malignant phenotype, which has not yet been adequately taken into consideration in the current WHO classification.

[Intrasylvian dermoid cysts of the pediatric patient: a case report and review].

OBJECTIVE: Supratentorial dermoid cysts are unusual benign mass lesions in pediatric patients, especially if located in a lateralized position such as in the lateral sulcus. Since these lesions often adhere tightly to circumjacent nerves or vessels, preoperative evaluation is important. Here we report on a pediatric patient with an intrasylvian dermoid cyst who underwent radical microsurgical resection and review the relevant literature. METHODS: An 8-year-old girl with a cystic space-occupying lesion in the right lateral sulcus was referred to our hospital. The lesion appeared similar to CSF on T1/T2 sequences on magnetic resonance imaging(MRI). However, diffusion-weighted imaging(DWI)indicated high diffusion restriction. During the operation, dermal appendage was found within the tumor capsule. Gross total resection was achieved and the patient was discharged without any deficits. Histological findings confirmed the diagnosis of a dermoid cyst. DISCUSSION: Only three cases of pediatric patients with dermoid cysts located in the lateral sulcus have been described. Due to its rarity and highly variable appearance on MRI, obtaining a differential diagnosis is difficult. Gross total resection should be the surgical goal;nevertheless, adjacent structures must be preserved. CONCLUSION: Here we described an additional rare case of intrasylvian dermoid cyst in childhood. The appearance of such cysts on DWI can aid with their preoperative diagnosis.

Deep RNA sequencing of muscle tissue reveals absence of viral signatures in dermatomyositis.

Objective: To explore a possible connection between active viral infections and manifestation of dermatomyositis (DM). Methods: Skeletal muscle biopsies were analyzed from patients diagnosed with juvenile (n=10) and adult (n=12) DM. Adult DM patients harbored autoantibodies against either TIF-1γ (n=7) or MDA5 (n=5). Additionally, we investigated skeletal muscle biopsies from non-diseased controls (NDC, n=5). We used an unbiased high-throughput RNA sequencing (HTS) approach to detect viral sequences. To further increase sequencing depth, a host depletion approach was applied. Results: In this observational study, no relevant viral sequences were detected either by native sequencing or after host depletion. The absence of detectable viral sequences makes an active viral infection of the muscle tissue unlikely to be the cause of DM in our cohorts. Discussion: Type I interferons (IFN) play a major role in the pathogenesis of both juvenile and adult DM. The IFN response is remarkably conserved between DM subtypes classified by specific autoantibodies. Certain acute viral infections are accompanied by a prominent type I IFN response involving similar downstream mechanisms as in DM. Aiming to elucidate the pathogenesis of DM in skeletal muscle tissue, we used deep RNA sequencing and a host depletion approach to detect possible causative viruses.

Proteomic and transcriptomic profiling of brainstem, cerebellum and olfactory tissues in early- and late-phase COVID-19.

Neurological symptoms, including cognitive impairment and fatigue, can occur in both the acute infection phase of coronavirus disease 2019 (COVID-19) and at later stages, yet the mechanisms that contribute to this remain unclear. Here we profiled single-nucleus transcriptomes and proteomes of brainstem tissue from deceased individuals at various stages of COVID-19. We detected an inflammatory type I interferon response in acute COVID-19 cases, which resolves in the late disease phase. Integrating single-nucleus RNA sequencing and spatial transcriptomics, we could localize two patterns of reaction to severe systemic inflammation, one neuronal with a direct focus on cranial nerve nuclei and a separate diffuse pattern affecting the whole brainstem. The latter reflects a bystander effect of the respiratory infection that spreads throughout the vascular unit and alters the transcriptional state of mainly oligodendrocytes, microglia and astrocytes, while alterations of the brainstem nuclei could reflect the connection of the immune system and the central nervous system via, for example, the vagus nerve. Our results indicate that even without persistence of severe acute respiratory syndrome coronavirus 2 in the central nervous system, local immune reactions are prevailing, potentially causing functional disturbances that contribute to neurological complications of COVID-19.

Distinct tissue niches direct lung immunopathology via CCL18 and CCL21 in severe COVID-19.

Prolonged lung pathology has been associated with COVID-19, yet the cellular and molecular mechanisms behind this chronic inflammatory disease are poorly understood. In this study, we combine advanced imaging and spatial transcriptomics to shed light on the local immune response in severe COVID-19. We show that activated adventitial niches are crucial microenvironments contributing to the orchestration of prolonged lung immunopathology. Up-regulation of the chemokines CCL21 and CCL18 associates to endothelial-to-mesenchymal transition and tissue fibrosis within these niches. CCL21 over-expression additionally links to the local accumulation of T cells expressing the cognate receptor CCR7. These T cells are imprinted with an exhausted phenotype and form lymphoid aggregates that can organize in ectopic lymphoid structures. Our work proposes immune-stromal interaction mechanisms promoting a self-sustained and non-resolving local immune response that extends beyond active viral infection and perpetuates tissue remodeling.

Correlation of Tumor Pathology with Fluorescein Uptake and MRI Contrast-Enhancement in Stereotactic Biopsies.

The utilization of fluorescein-guided biopsies has recently been discussed to improve and expedite operative techniques in the detection of tumor-positive tissue, as well as to avoid making sampling errors. In this study, we aimed to report our experience with fluorescein-guided biopsies and elucidate distribution patterns in different histopathological diagnoses in order to develop strategies to increase the efficiency and accuracy of this technique. We report on 45 fluorescence-guided stereotactic biopsies in 44 patients (15 female, 29 male) at our institution from March 2016 to March 2021, including 25 frame-based stereotactic biopsies and 20 frameless image-guided biopsies using VarioGuide®. A total number of 347 biopsy samples with a median of 8 samples (range: 4-18) per patient were evaluated for intraoperative fluorescein uptake and correlated to definitive histopathology. The median age at surgery was 63 years (range: 18-87). Of the acquired specimens, 63% were fluorescein positive. Final histopathology included glioblastoma (n = 16), B-cell non-Hodgkin lymphoma (n = 10), astrocytoma, IDH-mutant WHO grade III (n = 6), astrocytoma, IDH-mutant WHO grade II (n = 1), oligodendroglioma, IDH-mutant and 1p/19q-codeleted WHO grade II (n = 2), reactive CNS tissue/inflammation (n = 4), post-transplantation lymphoproliferative disorder (PTLD; n = 2), ependymoma (n = 1), infection (toxoplasmosis; n = 1), multiple sclerosis (n = 1), and metastasis (n = 1). The sensitivity for high-grade gliomas was 85%, and the specificity was 70%. For contrast-enhancing lesions, the specificity of fluorescein was 84%. The number needed to sample for contrast-enhancing lesions was three, and the overall number needed to sample for final histopathological diagnosis was five. Interestingly, in the astrocytoma, IDH-mutant WHO grade III group, 22/46 (48%) demonstrated fluorescein uptake despite no evidence for gadolinium uptake, and 73% of these were tumor-positive. In our patient series, fluorescein-guided stereotactic biopsy increases the likelihood of definitive neuropathological diagnosis, and the number needed to sample can be reduced by 50% in contrast-enhancing lesions.