In chronic diseases, such as HIV infection, plasmacytoid dendritic cells (pDCs) are rendered dysfunctional, as measured by their decreased capacity to produce IFN-α. In this study, we identified ...elevated levels of T cell Ig and mucin-domain containing molecule-3 (Tim-3)-expressing pDCs in the blood of HIV-infected donors. The frequency of Tim-3-expressing pDCs correlated inversely with CD4 T cell counts and positively with HIV viral loads. A lower frequency of pDCs expressing Tim-3 produced IFN-α or TNF-α in response to the TLR7 agonists imiquimod and Sendai virus and to the TLR9 agonist CpG. Thus, Tim-3 may serve as a biomarker of pDC dysfunction in HIV infection. The source and function of Tim-3 was investigated on enriched pDC populations from donors not infected with HIV. Tim-3 induction was achieved in response to viral and artificial stimuli, as well as exogenous IFN-α, and was PI3K dependent. Potent pDC-activating stimuli, such as CpG, imiquimod, and Sendai virus, induced the most Tim-3 expression and subsequent dysfunction. Small interfering RNA knockdown of Tim-3 increased IFN-α secretion in response to activation. Intracellular Tim-3, as measured by confocal microscopy, was dispersed throughout the cytoplasm prior to activation. Postactivation, Tim-3 accumulated at the plasma membrane and associated with disrupted TLR9 at the submembrane. Tim-3-expressing pDCs had reduced IRF7 levels. Furthermore, intracellular Tim-3 colocalized with p85 and IRF7 within LAMP1
lysosomes, suggestive of a role in degradation. We conclude that Tim-3 is a biomarker of dysfunctional pDCs and may negatively regulate IFN-α, possibly through interference with TLR signaling and recruitment of IRF7 and p85 into lysosomes, enhancing their degradation.
Cytotoxic CD8(+) T cells (CTLs) contain virus infections through the release of granules containing both perforin and granzymes. T cell 'exhaustion' is a hallmark of chronic persistent viral ...infections including HIV. The inhibitory regulatory molecule, T cell Immunoglobulin and Mucin domain containing 3 (Tim-3) is induced on HIV-specific T cells in chronic progressive infection. These Tim-3 expressing T cells are dysfunctional in terms of their capacities to proliferate or to produce cytokines. In this study, we evaluated the effect of Tim-3 expression on the cytotoxic capabilities of CD8(+) T cells in the context of HIV infection. We investigated the cytotoxic capacity of Tim-3 expressing T cells by examining 1) the ability of Tim-3(+) CD8(+) T cells to make perforin and 2) the direct ability of Tim-3(+) CD8(+) T cells to kill autologous HIV infected CD4(+) target cells. Surprisingly, Tim-3(+) CD8(+) T cells maintain higher levels of perforin, which was mainly in a granule-associated (stored) conformation, as well as express high levels of T-bet. However, these cells were also defective in their ability to degranulate. Blocking the Tim-3 signalling pathway enhanced the cytotoxic capabilities of HIV specific CD8(+) T cells from chronic progressors by increasing; a) their degranulation capacity, b) their ability to release perforin, c) their ability to target activated granzyme B to HIV antigen expressing CD4(+) T cells and d) their ability to suppress HIV infection of CD4(+) T cells. In this latter effect, blocking the Tim-3 pathway enhances the cytotoxcity of CD8(+) T cells from chronic progressors to the level very close to that of T cells from viral controllers. Thus, the Tim-3 receptor, in addition to acting as a terminator for cytokine producing and proliferative functions of CTLs, can also down-regulate the CD8(+) T cell cytotoxic function through inhibition of degranulation and perforin and granzyme secretion.
IL-7 therapy has been evaluated in patients who do not regain normal CD4 T cell counts after virologically successful antiretroviral therapy. IL-7 increases total circulating CD4 and CD8 T cell ...counts; however, its effect on HIV-specific CD8 T cells has not been fully examined. TRAF1, a prosurvival signaling adaptor required for 4-1BB-mediated costimulation, is lost from chronically stimulated virus-specific CD8 T cells with progression of HIV infection in humans and during chronic lymphocytic choriomeningitis infection in mice. Previous results showed that IL-7 can restore TRAF1 expression in virus-specific CD8 T cells in mice, rendering them sensitive to anti-4-1BB agonist therapy. In this article, we show that IL-7 therapy in humans increases the number of circulating HIV-specific CD8 T cells. For a subset of patients, we also observed an increased frequency of TRAF1
HIV-specific CD8 T cells 10 wk after completion of IL-7 treatment. IL-7 treatment increased levels of phospho-ribosomal protein S6 in HIV-specific CD8 T cells, suggesting increased activation of the metabolic checkpoint kinase mTORC1. Thus, IL-7 therapy in antiretroviral therapy-treated patients induces sustained changes in the number and phenotype of HIV-specific T cells.
Plasmacytoid dendritic cells (pDC) are the major producers of type I interferons (IFNs) in humans and rapidly produce IFN-α in response to virus exposure. Although HIV infection is associated with ...pDC activation, it is unclear why the innate immune response is unable to effectively control viral replication. We systematically compared the effect of HIV, Influenza, Sendai, and HSV-2 at similar target cell multiplicity of infection (M.O.I.) on human pDC function. We found that Influenza, Sendai, HSV-2 and imiquimod are able to rapidly induce IFN-α production within 4 hours to maximal levels, whereas HIV had a delayed induction that was maximal only after 24 hours. In addition, maximal IFN-α induction by HIV was at least 10 fold less than that of the other viruses in the panel. HIV also induced less TNF-α and MIP-1β but similar levels of IP-10 compared to other viruses, which was also mirrored by delayed upregulation of pDC activation markers CD83 and CD86. BDCA-2 has been identified as an inhibitory receptor on pDC, signaling through a pathway that involves SYK phosphorylation. We find that compared to Influenza, HIV induces the activation of the SYK pathway. Thus, HIV delays pDC IFN-α production and pDC activation via SYK phosphorylation, allowing establishment of viral populations.
Abstract
Monitoring the immune response in the setting of infectious disease and cancer is critical to assess disease status and targets of immune therapy. CyTOF® mass cytometry enables multiplex ...cellular phenotyping with more than 50 markers, making it ideal for comprehensive immune profiling. CyTOF technology utilizes antibodies tagged with unique monoisotopic metals, resulting in distinct signals that provide a high-resolution multiparametric landscape of a single cell. The Maxpar® Direct™ Immune Profiling Assay™ is a pre-titrated, dried-down, 30-marker antibody cocktail for immune profiling of human whole blood and PBMC by CyTOF. Paired with Maxpar Pathsetter™ software, stained samples are automatically resolved into 37 immune populations including major lineages and their subsets. In this study, we expanded the 30-marker assay to a 44-marker panel including exhaustion markers such as PD-1 and CTLA-4, co-stimulation markers 4-1BB and ICOS, and intracellular cytoplasmic markers IFN-γ, TNF-α, IL-2, perforin and granzyme B to assess cellular function in PMA/ionomycin-stimulated whole blood cultures. We modified the existing Maxpar Pathsetter model to automate the analysis of the expanded panel and report on additional functional parameters such as T cell exhaustion and cytokine production. Next, we applied this panel to whole blood stimulated with CMV peptides to investigate antigen-specific immune responses in a viral infection model in concert with in-depth phenotypic assessment. Collectively, we demonstrate the flexibility of the Maxpar Direct Immune Profiling Assay to incorporate additional surface and intracellular markers to study antigen-specific immunity in the context of whole blood immune profiling.
For RUO.
Abstract
Mass cytometry, which utilizes CyTOF® technology, is a single-cell analysis platform that uses metal-tagged antibodies. CyTOF can resolve more than 50 parameters in a single panel without ...the need for compensation, making it an ideal solution for routine enumeration of immune cells. The Maxpar® Direct™ Immune Profiling System is a sample-to-answer solution for human immune profiling using mass cytometry. The Maxpar®Direct™ Immune Profiling Assay™ is an optimized 30-marker panel contained in a dry single-tube format for human whole blood or PBMC staining, and samples are acquired on the Helios™ system. Maxpar Pathsetter™ is an automated software that reports cell counts, percentage calculations, and staining intensity. It also produces graphical elements such as dot plots and a Cen-se′™ graph for 37 immune cell populations. The panel can be tailored by adding markers to open channels, the Maxpar Pathsetter model can then be customized to measure expression markers on existing classified populations or identify additional immune cell subsets.
We present data where the Maxpar Direct Immune Profiling Assay is used as a core immunophenotyping panel and additional markers are added to create a nearly 50 marker panel. Added markers are used to identify MDSCs, further classify existing cell populations, and measure immuno-oncology related markers including OX40, TIM-3, Fas, PD-1, PD-L1, ICOS, and TIGIT. We demonstrate how the Maxpar Pathsetter model is modified to incorporate the added markers.
The ability to customize the Maxpar Pathsetter model and expand the Maxpar Direct Immune Profiling Assay allows for flexibility of the system. It allows researchers to have a streamlined solution for broad immune profiling using mass cytometry.
CD8(+) CTLs are adept at killing virally infected cells and cancer cells and releasing cytokines (e.g., IFN-γ) to aid this response. However, during cancer and chronic viral infections, such as with ...HIV, this CTL response is progressively impaired due to a process called T cell exhaustion. Previous work has shown that the glycoprotein T cell Ig and mucin domain-containing protein 3 (Tim-3) plays a functional role in establishing T cell exhaustion. Tim-3 is highly upregulated on virus and tumor Ag-specific CD8(+) T cells, and antagonizing Tim-3 helps restore function of CD8(+) T cells. However, very little is known of how Tim-3 signals in CTLs. In this study, we assessed the role of Tim-3 at the immunological synapse as well as its interaction with proximal TCR signaling molecules in primary human CD8(+) T cells. Tim-3 was found within CD8(+) T cell lipid rafts at the immunological synapse. Blocking Tim-3 resulted in a significantly greater number of stable synapses being formed between Tim-3(hi)CD8(+) T cells and target cells, suggesting that Tim-3 plays a functional role in synapse formation. Further, we confirmed that Tim-3 interacts with Lck, but not the phospho-active form of Lck. Finally, Tim-3 colocalizes with receptor phosphatases CD45 and CD148, an interaction that is enhanced in the presence of the Tim-3 ligand, galectin-9. Thus, Tim-3 interacts with multiple signaling molecules at the immunological synapse, and characterizing these interactions could aid in the development of therapeutics to restore Tim-3-mediated immune dysfunction.
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