Probes for CD8

Aims: the knowledge of the pathogenic mechanisms of severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) is certainly a priority for the scientific community. Two main elements are involved in the biology of the most severe forms of Coronavirus disease 2019 (COVID-19): the direct cytopathic effect of the virus against the host tissues, and a dysfunction of the immune system, characterized by the exhaustion of T lymphocytes. The exhaustion of T cells in COVID-19 is poorly understand, but some data could suggest a possible role of PD-1/PD-L1 axis. The aim of this study was to evaluate the possible role of PD-L1 expression in the pulmonary tissue in subjects affected by COVID-19. Methods and results: the presence of SARS-CoV-2 in the pulmonary tissue, and its exact location, was indagated by in-situ hybridization; the expression of PD-L1 and CD8 in the same tissue was indagated by immunohistochemistry. Overall, PD-L1 resulted diffusely expressed in 70% of the cases, and an intense expression was observed in 43.5% of cases. Diffuse and intense presence of SARS-CoV-2 by in situ hybridization (ISH) significantly correlated with an intense PD-L1 expression, and with expression of PD-L1 by pneumocytes. Conclusions: PD-L1 is overexpressed in the pulmonary tissue of subjects died for COVID-19, and mainly in subjects with a high viral load. These data suggest a possible role of PD-L1 in the immune system exhaustion at the basis of the severe forms of the disease.

Epstein-Barr virus (EBV) infection is associated with a better response to anti-PD1 immunotherapy. We hypothesised that genetic alterations induced by EBV infection are responsible for the activation of key immune responses and hence are predictive of anti-PD1 efficacy.With transcriptome data of gastric cancer (GC), we explored differentially expressed genes (DEGs) specific for EBV infection and performed coexpression network analysis using the DEGs to identify the consistent coexpression genes (CCGs) between EBV-positive and EBV-negative GC tissues. We selected the tag genes of the CCGs and validated them using RNA sequencing and immunohistochemistry. We established murine models and collected tissues from clinical patients to test the value of SLAMF8 in predicting anti-PD1 treatment. The location and expression of SLAMF8 were characterised by multiplex immunofluorescence and quantitative PCR. Moreover, exogenous overexpression and RNA-sequencing analysis were used to test the potential function of SLAMF8.We identified 290 CCGs and validated the tag gene SLAMF8 in transcriptome data of gastrointestinal cancer (GI). We observed that the T-cell activation pathway was significantly enriched in high-expression SLAMF8 GI cancers. Higher SLAMF8 expression was positively associated with CD8 expression and a better response to anti-PD1 treatment. We further observed dynamically increased expression of SLAMF8 in murine models relatively sensitive to anti-PD1 treatment. SLAMF8 was mainly expressed on the surface of macrophages. Exogenous overexpression of SLAMF8 in macrophages resulted in enrichment of positive regulation of multiple immune-related pathways.Higher SLAMF8 expression may predict better anti-PD1 immunotherapy efficacy in GI cancer.

CD4 T cells are key mediators of adaptive immune responses during infection and vaccination. Within secondary lymphoid organs, helper CD4 T cells, particularly those residing in germinal centers known as follicular helper T cells (Tfh), provide critical help to B-cells to promote their survival, isotype switching and selection of high affinity memory B-cells. On the other hand, the important role of Tfh cells for the maintenance of HIV reservoir is well documented. Thus, interrogating and better understanding the tissue specific micro-environment and immune subsets that contribute to optimal Tfh cell differentiation and function is important for designing successful prevention and cure strategies. Here, we describe the development and optimization of eight multispectral confocal microscopy immunofluorescence panels designed for in depth characterization and immune-profiling of relevant immune cells in formalin-fixed paraffin-embedded human lymphoid tissue samples. We provide a comprehensive library of antibodies to use for the characterization of CD4+ T-cells -including Tfh and regulatory T-cells- as well as CD8 T-cells, B-cells, macrophages and dendritic cells and discuss how the resulting multispectral confocal datasets can be quantitatively dissected using the HistoCytometry pipeline to collect information about relative frequencies and immune cell spatial distributions. Cells harboring actively transcribed virus are analyzed using an in-situ hybridization assay for the characterization of HIV mRNA positive cells in combination with additional protein markers (multispectral RNAscope). The application of this methodology to lymphoid tissues offers a means to interrogate multiple relevant immune cell targets simultaneously at increased resolution in a reproducible manner to guide CD4 T-cell studies in infection and vaccination.

Emerging RNA viruses that target the central nervous system (CNS) lead to cognitive sequelae in survivors. Studies in humans and mice infected with West Nile virus (WNV), a re-emerging RNA virus associated with learning and memory deficits, revealed microglial-mediated synapse elimination within the hippocampus. Moreover, CNS-resident memory T (TRM) cells activate microglia, limiting synapse recovery and inducing spatial learning defects in WNV-recovered mice. The signals involved in T cell-microglia interactions are unknown.Here, we examined immune cells within the murine WNV-recovered forebrain using single-cell RNA sequencing to identify putative ligand-receptor pairs involved in intercellular communication between T cells and microglia. Clustering and differential gene analyses were followed by protein validation and genetic and antibody-based approaches utilizing an established murine model of WNV recovery in which microglia and complement promote ongoing hippocampal synaptic loss.Profiling of host transcriptome immune cells at 25 days post-infection in mice revealed a shift in forebrain homeostatic microglia to activated subpopulations with transcriptional signatures that have previously been observed in studies of neurodegenerative diseases. Importantly, CXCL16/CXCR6, a chemokine signaling pathway involved in TRM cell biology, was identified as critically regulating CXCR6 expressing CD8+ TRM cell numbers within the WNV-recovered forebrain. We demonstrate that CXCL16 is highly expressed by all myeloid cells, and its unique receptor, CXCR6, is highly expressed on all CD8+ T cells. Using genetic and pharmacological approaches, we demonstrate that CXCL16/CXCR6 not only is required for the maintenance of WNV-specific CD8 TRM cells in the post-infectious CNS, but also contributes to their expression of TRM cell markers. Moreover, CXCR6+CD8+ T cells are required for glial activation and ongoing synapse elimination.We provide a comprehensive assessment of the role of CXCL16/CXCR6 as an interaction link between microglia and CD8+ T cells that maintains forebrain TRM cells, microglial and astrocyte activation, and ongoing synapse elimination in virally recovered animals. We also show that therapeutic targeting of CXCL16 in mice during recovery may reduce CNS CD8+ TRM cells.

BackgroundThe tumor microenvironment (TME) is highly complex, comprised of tumor cells, immune cells, stromal cells, and extracellular matrix. Understanding spatial interactions between various cell types and their activation states in the TME is crucial for implementing successful immunotherapy strategies against various types of cancer. This study demonstrates a highly sensitive and specific multiplexed technique, the RNAscope HiPlex v2 in situ hybridization (ISH) assay for spatial and transcriptomic profiling of target genes to assess immune regulation in human lung, breast, cervical and ovarian FFPE tumor tissues.MethodsWe have expanded our current RNAscope HiPlex assay capability of iteratively multiplexing up to 12 targets in fixed and fresh frozen samples to include formalin fixed paraffin embedded (FFPE) tissues. The novel FFPE reagent effectively reduces background autofluorescence, improving the signal to noise ratio. We have leveraged this technology to investigate spatial expression of 12 oncology and immuno-oncology target genes, including tumor markers, immune checkpoint markers, immunosuppression markers, immune cell markers and secreted chemokine RNA expression profile within the TME. The targets were simultaneously registered using HiPlex image registration software v2 that enables background subtraction.ResultsWe visualized T cell infiltration and identified T cell subsets within tumors using CD3and CD8 expression and activated T cells by IFNG expression. We further identified subsets of pro- and anti-inflammatory macrophages by CD68 and CD163 expression as well effector cells which secrete chemokines and cytokine. We also detected the hypoxia markers HIF1A and VEGF to elucidate the immunosuppressive state of tumor cells. Preliminary analysis and quantification of the HIF1A expression using HALO image analysis software showed higher copy numbers in the lung tumor as compared to the other tumors, demonstrating the sensitivity of the assay through differential expression. We additionally showed the differential expression of immune checkpoint markers PDCD1, and CD274 within the TME.ConclusionsUsing a highly sensitive multiplexed RNAscope HiPlex v2 ISH assay, we have demonstrated the capability of this technique to spatially resolve 12 targets in four different tumor types. The FFPE reagent efficiently quenched background autofluorescence in the tissues and identified immune cell signatures within the TME. Quantification of immunosuppressive markers further depicted a differential expression among various tumors. This technology is highly beneficial for investigating complex and spatial tumor-stroma interactions in basic science and translational research. The assay can also provide valuable understanding of the biological crosstalk among various cell types in complex and heterogeneous tissues.

The antitumor efficacies of immune checkpoint inhibitors (ICIs) and the usefulness of potential predictive markers such as programmed death-ligand 1 (PD-L1) expression, density of tumor-infiltrating lymphocytes (TILs) and microsatellite instability (MSI) in sinonasal squamous cell carcinoma (SNSCC) have not been fully elucidated. We retrospectively analyzed 131 SNSCCs with immunohistochemistry for PD-L1 expression, TIL subpopulations and loss of mismatch repair (MMR) proteins as a surrogate for MSI-high. We also comprehensively evaluated the mutual relationships among these immuno-markers, high-risk human papillomavirus (HPV) infection, epidermal growth factor receptor (EGFR) gene status, and KRAS mutation. PD-L1 expression (tumor proportion score ≥ 1%) was detected in 60 (45.8%) SNSCC cases and was significantly associated with worse overall survival (OS) (p = 0.0240). High density of cluster of differentiation 8 (CD8)-positive TILs was significantly associated with better progression-free survival (PFS) (p = 0.0368), and high density of forkhead box protein P3-positive TILs was significantly associated with better PFS and OS (p = 0.0007 and 0.0143, respectively). With respect to the combination of CD8 + TIL and PD-L1 expression, the high-CD8/PD-L1-negative group showed the most favorable prognosis, whereas the low-CD8/PD-L1-positive group showed the worst prognosis. MMR loss was detected in 3 (2.3%) of the 131 cases. HPV infection (6.1%), EGFR mutation (14.5%), EGFR copy number gain (26%), and MMR loss were essentially mutually exclusive; patients in these molecular groups showed significant differences in prognosis but not in the degree of PD-L1 expression or TILs. Among the nine ICI-treated patients, three (33.3%) were responders, and the EGFR-wild type cases (n = 7) showed better clinical responses to an ICI compared to the EGFR-mutant cases (n = 2). Among the patients with residual/recurrent EGFR-wild type tumors (n = 43), ICI treatment significantly improved OS (p = 0.0281). The results suggest that the evaluation of immuno-markers and molecular subclassification may be helpful for prognostic prediction and selecting an individualized therapeutic strategy for patients with SNSCC.

HIV persistence in tissue sites despite ART is a major barrier to HIV cure. Detailed studies of HIV-infected cells and immune responses in native lymph node tissue environment is critical for gaining insight into immune mechanisms impacting HIV persistence and clearance in tissue sanctuary sites. We compared HIV persistence and HIV-specific T cell responses in lymph node biopsies obtained from 14 individuals who initiated therapy in Fiebig stages I/II, 5 persons treated in Fiebig stages III-V and 17 late treated individuals who initiated ART in Fiebig VI and beyond. Using multicolor immunofluorescence staining and in situ hybridization, we detect HIV RNA and/or protein in 12 of 14 Fiebig I/II treated persons on suppressive therapy for 1 to 55 months, and in late treated persons with persistent antigens. CXCR3+ T follicular helper cells harbor the greatest amounts of gag mRNA transcripts. Notably, HIV-specific CD8+ T cells responses are associated with lower HIV antigen burden, suggesting that these responses may contribute to HIV suppression in lymph nodes during therapy. These results reveal HIV persistence despite the initiation of ART in hyperacute infection and highlight the contribution of virus-specific responses to HIV suppression in tissue sanctuaries during suppressive ART.

To analyze the correlation between the inducing effect of Fusobacterium nucleatum (Fn) on the surface expression of the inhibitory receptor KIR2DL1 on CD8+ T cells in oesophageal squamous cell carcinoma (ESCC) and the clinicopathological features and survival prognosis and to explore its clinical significance.The inducing effect of Fn on CD8+ T cell surface inhibitory receptor KIR2DL1 expression was analyzed in a coculture system of human CD8+ T cells and ESCC cells infected with Fn. Fn infection and the expression of KIR2DL1 on CD8+ T cells were detected by RNAscope and immunohistochemistry in ESCC tissues, and the correlations between the inducing effect of Fn on KIR2DL1 expression on CD8+ T cells and clinicopathological features were analyzed. COX regression was used to analyze the influence of each factor on the prognosis of ESCC. Survival curves were plotted by the Kaplan-Meier method, and the effect of KIR2DL1 induction on survival time was analyzed by the log-rank test.In the coculture system, KIR2DL1 expression on the surface of CD8+ T cells increased with increasing Fn infection time. In ESCC tissues, Fn infection was significantly correlated with high KIR2DL1 expression on CD8+ T cells. The Fn + CD8+KIR2DL1 positive patients were predominantly males who were smokers and alcohol drinkers. Moreover, patients with Fn infection were characterized by poor tumour differentiation, advanced clinical stage, and a short survival time. Meanwhile, Fn + CD8+KIR2DL1 positive group was independent risk factor affecting the prognosis of ESCC patients.Long-term drinking and smoking lead to an extremely unhealthy oral environment in which Fn infection and colonization are more likely to occur, thus inducing high expression of KIR2DL1 on the surface of CD8+ T cells, which can weaken the antitumour immune response and promote the malignant progression of ESCC.HIGHLIGHTSFn induced high expression of KIR2DL1 CD8+ T cells in a time-dependent manner.Fn can reduce the response of tumour cells to CDDP.The inducing effect of Fn on CD8+ T cell surface KIR2DL1 expression was significantly associated with the poor prognosis of ESCC patients.