Julian Swatler

Bio: Julian Swatler is an academic researcher from Nencki Institute of Experimental Biology. The author has contributed to research in topics: Medicine & Immune system. The author has an hindex of 5, co-authored 12 publications receiving 83 citations.

Single-cell RNA sequencing reveals functional heterogeneity of glioma-associated brain macrophages.

Abstract: Microglia are resident myeloid cells in the central nervous system (CNS) that control homeostasis and protect CNS from damage and infections. Microglia and peripheral myeloid cells accumulate and adapt tumor supporting roles in human glioblastomas that show prevalence in men. Cell heterogeneity and functional phenotypes of myeloid subpopulations in gliomas remain elusive. Here we show single-cell RNA sequencing (scRNA-seq) of CD11b+ myeloid cells in naive and GL261 glioma-bearing mice that reveal distinct profiles of microglia, infiltrating monocytes/macrophages and CNS border-associated macrophages. We demonstrate an unforeseen molecular heterogeneity among myeloid cells in naive and glioma-bearing brains, validate selected marker proteins and show distinct spatial distribution of identified subsets in experimental gliomas. We find higher expression of MHCII encoding genes in glioma-activated male microglia, which was corroborated in bulk and scRNA-seq data from human diffuse gliomas. Our data suggest that sex-specific gene expression in glioma-activated microglia may be relevant to the incidence and outcomes of glioma patients.

Remodeling of T Cell Dynamics During Long COVID Is Dependent on Severity of SARS-CoV-2 Infection

Abstract: Several COVID-19 convalescents suffer from the post-acute COVID-syndrome (PACS)/long COVID, with symptoms that include fatigue, dyspnea, pulmonary fibrosis, cognitive dysfunctions or even stroke. Given the scale of the worldwide infections, the long-term recovery and the integrative health-care in the nearest future, it is critical to understand the cellular and molecular mechanisms as well as possible predictors of the longitudinal post-COVID-19 responses in convalescent individuals. The immune system and T cell alterations are proposed as drivers of post-acute COVID syndrome. However, despite the number of studies on COVID-19, many of them addressed only the severe convalescents or the short-term responses. Here, we performed longitudinal studies of mild, moderate and severe COVID-19-convalescent patients, at two time points (3 and 6 months from the infection), to assess the dynamics of T cells immune landscape, integrated with patients-reported symptoms. We show that alterations among T cell subsets exhibit different, severity- and time-dependent dynamics, that in severe convalescents result in a polarization towards an exhausted/senescent state of CD4+ and CD8+ T cells and perturbances in CD4+ Tregs. In particular, CD8+ T cells exhibit a high proportion of CD57+ terminal effector cells, together with significant decrease of naïve cell population, augmented granzyme B and IFN-γ production and unresolved inflammation 6 months after infection. Mild convalescents showed increased naïve, and decreased central memory and effector memory CD4+ Treg subsets. Patients from all severity groups can be predisposed to the long COVID symptoms, and fatigue and cognitive dysfunctions are not necessarily related to exhausted/senescent state and T cell dysfunctions, as well as unresolved inflammation that was found only in severe convalescents. In conclusion, the post-COVID-19 functional remodeling of T cells could be seen as a two-step process, leading to distinct convalescent immune states at 6 months after infection. Our data imply that attenuation of the functional polarization together with blocking granzyme B and IFN-γ in CD8+ cells might influence post-COVID alterations in severe convalescents. However, either the search for long COVID predictors or any treatment to prevent PACS and further complications is mandatory in all patients with SARS-CoV-2 infection, and not only in those suffering from severe COVID-19.

[Immune checkpoint‑targeted cancer immunotherapies].

Abstract: Tumor cells may express on their surface various characteristic antigens that can induce antitumor immunity. However, cancer in human body may induce an immunosuppressive microenvironment that limits immune response to its antigens. For many years scientists have tried to develop an immunotherapy which would induce a potent antitumor immune response and lead to an elimination of the disease. One of the most promising immunotherapies is blockade of immune checkpoints, i.e. a group of costimulatory molecules negatively regulating the immune system. Their blockade would overcome immune tolerance in the tumor microenvironment and amplify antitumor immunity. What's more, immune checkpoint blockade may turn out even more profitable, as some of immune checkpoints and their ligands are expressed on tumor surface and on tumor infiltrating lymphocytes, contributing to the immunosuppressive cancer microenvironment. Phase III clinical trials have confirmed efficacy of an anti‑CTLA‑4 antibody ipilimumab, thereby leading to its acceptance for the treatment of advanced melanoma. Thanks to promising results of the phase I clinical trials, a breakthrough therapy designation and an early approval for the treatment have been granted to anti‑PD‑1 antibodies ‑ nivolumab (for the treatment of advanced melanoma and advanced non‑small cell lung cancer) and pembrolizumab (for the treatment of advanced melanoma) and, in the treatment of advanced bladder cancer, an anti‑PD‑L1 antibody ‑ MPDL3280A as well. Other immune checkpoints, such as LAG‑3, TIM‑3, BTLA, B7‑H3 and B7‑H4, are also under early evaluation.

Immunosuppressive Cell Subsets and Factors in Myeloid Leukemias.

Abstract: Both chronic myeloid leukemia and acute myeloid leukemia evade the immune response during their development and disease progression. As myeloid leukemia cells modify their bone marrow microenvironment, they lead to dysfunction of cytotoxic cells, such as CD8+ T cells or NK cells, simultaneously promoting development of immunosuppressive regulatory T cells and suppressive myeloid cells. This facilitates disease progression, spreading of leukemic blasts outside the bone marrow niche and therapy resistance. The following review focuses on main immunosuppressive features of myeloid leukemias. Firstly, factors derived directly from leukemic cells - inhibitory receptors, soluble factors and extracellular vesicles, are described. Further, we outline function, properties and origin of main immunosuppressive cells - regulatory T cells, myeloid derived suppressor cells and macrophages. Finally, we analyze interplay between recovery of effector immunity and therapeutic modalities, such as tyrosine kinase inhibitors and chemotherapy.

Single-cell RNA sequencing reveals functional heterogeneity and sex differences of glioma-associated brain macrophages

Abstract: Brain resident and infiltrating innate immune cells adapt a tumor-supportive phenotype in the glioma microenvironment. Flow cytometry analysis supported by a single-cell RNA sequencing study of human gliomas indicate considerable cell type heterogeneity. It remains disputable whether microglia and infiltrating macrophages have the same or distinct roles in supporting glioma progression. Here, we performed single-cell transcriptomics analyses of CD11b+ cells sorted from murine syngeneic gliomas, indicating distinct activity of microglia, infiltrating monocytes/macrophages and CNS border-associated macrophages. Our results demonstrate a previously immeasurable scale of molecular heterogeneity in the innate immune response in gliomas. We identified genes differentially expressed in activated microglia from glioma-bearing mice of different sex, and profound overexpression of the MHCII genes by male microglial cells, which we also observed in bulk human glioma samples. Sex-specific gene expression in microglia in the glioma microenvironment may be relevant to sex differences in incidence and outcomes of glioblastoma patients.

Dissecting the multicellular ecosystem of metastatic melanoma by single-cell RNA-seq

Abstract: Single-cell expression profiles of melanoma Tumors harbor multiple cell types that are thought to play a role in the development of resistance to drug treatments. Tirosh et al. used single-cell sequencing to investigate the distribution of these differing genetic profiles within melanomas. Many cells harbored heterogeneous genetic programs that reflected two different states of genetic expression, one of which was linked to resistance development. Following drug treatment, the resistance-linked expression state was found at a much higher level. Furthermore, the environment of the melanoma cells affected their gene expression programs. Science, this issue p. 189 Melanoma cells show transcriptional heterogeneity. To explore the distinct genotypic and phenotypic states of melanoma tumors, we applied single-cell RNA sequencing (RNA-seq) to 4645 single cells isolated from 19 patients, profiling malignant, immune, stromal, and endothelial cells. Malignant cells within the same tumor displayed transcriptional heterogeneity associated with the cell cycle, spatial context, and a drug-resistance program. In particular, all tumors harbored malignant cells from two distinct transcriptional cell states, such that tumors characterized by high levels of the MITF transcription factor also contained cells with low MITF and elevated levels of the AXL kinase. Single-cell analyses suggested distinct tumor microenvironmental patterns, including cell-to-cell interactions. Analysis of tumor-infiltrating T cells revealed exhaustion programs, their connection to T cell activation and clonal expansion, and their variability across patients. Overall, we begin to unravel the cellular ecosystem of tumors and how single-cell genomics offers insights with implications for both targeted and immune therapies.

Lung Cancer Biomarkers.

Abstract: The molecular characterization of lung cancer has changed the classification and treatment of these tumors, becoming an essential component of pathologic diagnosis and oncologic therapy decisions. Through the recognition of novel biomarkers, such as epidermal growth factor receptor mutations and anaplastic lymphoma kinase translocations, it is possible to identify subsets of patients who benefit from targeted molecular therapies. The success of targeted anticancer therapies and new immunotherapy approaches has created a new paradigm of personalized therapy and has led to accelerated development of new drugs for lung cancer treatment. This article focuses on clinically relevant cancer biomarkers as targets for therapy and potential new targets for drug development.

Lipid and Lipoprotein Metabolism in Microglia.

Abstract: Microglia, once viewed as static bystanders with limited homeostatic functions, are now considered key players in the development of neuroinflammatory and neurodegenerative diseases. Microglial activation is a salient feature of neuroinflammation involving a dynamic process that generates multitudinous microglial phenotypes that can respond to a variety of situational cues in the central nervous system. Recently, a flurry of single cell RNA-sequencing studies have defined microglial phenotypes in unprecedented detail, and have highlighted robust changes in the expression of genes involved in lipid and lipoprotein metabolism. Increased expression of genes such as Apolipoprotein E (ApoE), Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) and Lipoprotein Lipase (LPL) in microglia during development, damage, and disease, suggest that increased lipid metabolism is needed to fuel protective cellular functions such as phagocytosis. This review describes our current understanding of lipid and lipoprotein metabolism in microglia, and highlights microglial lipid metabolism as a modifiable target for the treatment of neurodegenerative diseases such as Alzheimer’s disease and multiple sclerosis.