State Of CD8 Research Articles

Single cell transcriptomics resolves activation dynamics and cellular states of human blood and tissue T cells

Abstract T cells persist as heterogeneous subsets throughout the body and are essential in mounting protective immune responses. In healthy humans, most of our knowledge of T cell activation derives from sampling the peripheral blood and therefore the transcriptional states of tissue T cells, their functional responses to stimulation, and how they relate to T cells in blood have been poorly defined. Here, we profile the activation dynamics of T cells isolated from human lungs (LG), lymph nodes (LN), bone marrow (BM) and blood following TCR-stimulation by single cell RNA-sequencing (scRNA-seq). Analysis of >50,000 individual resting and activated T cells using clustering and new factorization methods reveals lineage-specific gene expression signatures and discrete activation trajectories in all tissues. Between sites, T cells from LG and LN are most distinct, while blood T cells are most similar to those in BM but persist in a more activated basal state. We identify a common transcriptional profile of tissue T cells and detect trace numbers of these cells in the blood. We also define cellular states for resting and activated T cells across tissues, including an interferon-induced state in CD4+ T cells and distinct effector states specific to CD8+ T cells, and uncover new markers of T cell activation that may be central to T cell function. Importantly, we demonstrate that the T cell activation states resolved here serve as a new baseline for defining T cell dysfunction in disease, revealing novel insights into T cell states among tumor-infiltrating lymphocytes from previous studies. Our investigation couples scRNA-seq with new analysis methods to define the activation dynamics of human T cells from disparate anatomical sites on a single cell level.

Abstract IA35: Determinants of effective tumor immunity

Abstract Treatment of solid tumors has been revolutionized by immune checkpoint blockade therapies; yet even for melanoma, for which high response rates are observed, the majority of tumors continue to grow after therapy. To identify immune cell states associated with success or failure of immunotherapy, we profiled the single-cell transcriptomes of immune cells from tumor samples obtained from melanoma patients treated with checkpoint inhibitors. We defined specific activation states of CD8+ T cells that associate with tumor growth post-therapy, delineated their epigenetic landscape and clonality, and demonstrated enhanced immunity by targeting a novel combination of T cell factors. We also found that expression of a single T cell gene was predictive of tumor regression in response to therapy. Our study thus reveals immune cell states and molecules that help explain effective immunotherapy in humans. Citation Format: Nir Hacohen. Determinants of effective tumor immunity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr IA35.

HDAC3 restrains CD8-lineage genes to maintain a bi-potential state in CD4+CD8+ thymocytes for CD4-lineage commitment.

CD4 and CD8 T cells are vital components of the immune system. We found that histone deacetylase 3 (HDAC3) is critical for the development of CD4 T cells, as HDAC3-deficient DP thymocytes generate only CD8SP thymocytes in mice. In the absence of HDAC3, MHC Class II-restricted OT-II thymocytes are redirected to the CD8 cytotoxic lineage, which occurs with accelerated kinetics. Analysis of histone acetylation and RNA-seq reveals that HDAC3-deficient DP thymocytes are biased towards the CD8 lineage prior to positive selection. Commitment to the CD4 or CD8 lineage is determined by whether persistent TCR signaling or cytokine signaling predominates, respectively. Despite elevated IL-21R/γc/STAT5 signaling in HDAC3-deficient DP thymocytes, blocking IL-21R does not restore CD4 lineage commitment. Instead, HDAC3 binds directly to CD8-lineage promoting genes. Thus, HDAC3 is required to restrain CD8-lineage genes in DP thymocytes for the generation of CD4 T cells.

A correlative and quantitative imaging approach enabling characterization of primary cell-cell communication: Case of human CD4+ T cell-macrophage immunological synapses

Cell-to-cell communication engages signaling and spatiotemporal reorganization events driven by highly context-dependent and dynamic intercellular interactions, which are difficult to capture within heterogeneous primary cell cultures. Here, we present a straightforward correlative imaging approach utilizing commonly available instrumentation to sample large numbers of cell-cell interaction events, allowing qualitative and quantitative characterization of rare functioning cell-conjugates based on calcium signals. We applied this approach to examine a previously uncharacterized immunological synapse, investigating autologous human blood CD4+ T cells and monocyte-derived macrophages (MDMs) forming functional conjugates in vitro. Populations of signaling conjugates were visualized, tracked and analyzed by combining live imaging, calcium recording and multivariate statistical analysis. Correlative immunofluorescence was added to quantify endogenous molecular recruitments at the cell-cell junction. By analyzing a large number of rare conjugates, we were able to define calcium signatures associated with different states of CD4+ T cell-MDM interactions. Quantitative image analysis of immunostained conjugates detected the propensity of endogenous T cell surface markers and intracellular organelles to polarize towards cell-cell junctions with high and sustained calcium signaling profiles, hence defining immunological synapses. Overall, we developed a broadly applicable approach enabling detailed single cell- and population-based investigations of rare cell-cell communication events with primary cells.

An HIF-1α/VEGF-A Axis in Cytotoxic T Cells Regulates Tumor Progression

SummaryCytotoxic T cells infiltrating tumors are thought to utilize HIF transcription factors during adaptation to the hypoxic tumor microenvironment. Deletion analyses of the two key HIF isoforms found that HIF-1α, but not HIF-2α, was essential for the effector state in CD8+ T cells. Furthermore, loss of HIF-1α in CD8+ T cells reduced tumor infiltration and tumor cell killing, and altered tumor vascularization. Deletion of VEGF-A, an HIF target gene, in CD8+ T cells accelerated tumorigenesis while also altering vascularization. Analyses of human breast cancer showed inverse correlations between VEGF-A expression and CD8+ T cell infiltration, and a link between T cell infiltration and vascularization. These data demonstrate that the HIF-1α/VEGF-A axis is an essential aspect of tumor immunity.

Abstract 1668: Comprehensive 10 color flow cytometry analysis of the neuroblastoma intratumoral immune response using the murine syngeneic neuro-2a tumor model

Abstract Neuroblastoma is the most prevalent solid tumor in childhood and the most common tumor in infants less than 1 year of age. In spite of aggressive multi-modal therapeutic approaches, the 5-year survival rate in patients with high-risk neuroblastoma remains poor at <50%. Recent advances have focused on harnessing the immune system to combat neuroblastoma. Antibodies that abrogate the immune checkpoint signaling pathway such as anti-CTLA-4 and anti-PD-L1 suppress neuroblastoma growth in certain mouse models of disease. Furthermore, the dinutuximab antibody that targets ganglioside GD2 expressing cells has been demonstrated to trigger neuroblastoma regression using a mechanism that involves several immune subsets. Although evidence suggest the host immune response can be exploited to fight neuroblastoma, the key immune subsets, their relative contribution, and mechanism of action to suppress neuroblastoma growth have yet to be fully characterized. To this end, we used flow cytometry to immunophenotype the intratumoral immune response in the neuro-2a model of neuroblastoma. This was accomplished by developing two 10-color panels to quantify the proportions of various myeloid and T cell subsets respectively. Using the myeloid panel, our results showed that total neuro-2a tumor immune cells were predominantly myeloid lineage-derived (CD11b+). A combination of Ly-6G and Ly-6C antibodies demonstrated that myeloid-derived suppressor cells (MDSCs) comprised the bulk of the myeloid cells and were more heavily skewed towards the granulocytic phenotype versus monocytic. An MDSC exclusion gate and a combination of F4/80, MHC class II, and CD206 antibodies enabled the analysis of tumor-associated macrophage subsets. Our results revealed that neuro-2a tumors contained relatively few activated M1 macrophages, which are typically associated with anti-tumor responses, and instead were dominated with a pro-tumor M2 macrophage response. The T cell antibody panel revealed that CD4+ T cells outnumbered CD8+ T cells by 2-fold. Regulatory T cells (Tregs) in the CD4+ T cell fraction were identified by a combination of FoxP3 and CD25 antibodies. The frequency of Tregs varied but represented <50% of total CD4+ T cells. Finally, the activation state of CD8+ T cells was examined using Ki-67, CTLA-4, and PD-1 antibodies. Analysis demonstrated that the majority of CD8+ T cells in neuro-2a tumors were actively proliferating based on the expression of Ki-67. However, most of the proliferating CD8+ T cells also co-expressed PD-1 suggesting a loss of anti-tumor functionality and an exhausted phenotype. This study provides a comprehensive immune profile of neuro-2a tumors and supports a platform with which to test new single agent and combination therapies designed to treat neuroblastoma. Citation Format: David D. Draper, Matt Thayer, Alden Wong, Dan Saims, Scott C. Wise. Comprehensive 10 color flow cytometry analysis of the neuroblastoma intratumoral immune response using the murine syngeneic neuro-2a tumor model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1668. doi:10.1158/1538-7445.AM2017-1668

Abstract B043: Systems pharmacology modeling of anti-CD20/CD3 T-cell dependent bispecific antibody and its application to clinical trial design

Abstract Objectives: To develop and apply a quantitative systems pharmacology (QSP) model to support clinical trial design for anti-CD20/CD3 T-cell dependent bispecific antibody in non-Hodgkin lymphoma (NHL). Methods: We developed a mechanistic model to describe the dynamics of B- and T-lymphocytes and their interactions in multiple physiological compartments (peripheral blood, tumor, and lymphoid tissues including the spleen, lymph nodes, and bone marrow) in the presence of an anti-CD20/CD3 T-cell dependent bispecific antibody (CD20-TDB) and the CD19-targeting bispecifc T-cell engager blinatumomab (a molecule with a similar mechanism of action, approved for ALL). The model is based on physiological, mechanistic, pharmacokinetic, and pharmacodynamic data and includes: 1) multiple activation states of CD8+ T-cells; 2) CD19+CD20- (pro-B), and CD19+CD20+ (pre- to mature-B) B-lymphocytes; and 3) the pharmacokinetics of CD20-TDB and blinatumomab and their mechanistic effects (activation of CD8+ T-lymphocytes and consequent killing of CD20+ and CD19+ B-lymphocytes, respectively). Results: The model was calibrated using in vitro potency data and circulating cell measurements in cynomolgous monkeys treated with CD20-TDB [1]. Preclinical and translational validation was performed using additional CD20-TDB preclinical data and blinatumomab clinical data [2, 3]. The model replicated the effects of CD20-TDB on cell dynamics in circulation, and predicted CD20-TDB preclinical data at lower doses and in tissues, and blinatumomab clinical data in patients with ALL and NHL. The model will be used to evaluate and propose dosing strategies for CD20-TDB in patients with NHL and to inform other clinical development considerations. Conclusions: The mechanism-based systems model accurately captures and predicts the pharmacodynamics of CD20-TDB in cynomolgous monkeys and in patients with ALL and NHL. The model provides a novel approach for evaluation of clinical dosing strategies for CD20-TDB and can be extended to related molecules and/or other B cell malignancies.

HTLV-1 induces a Th1-like state in CD4+ CCR4+ T cells that produces an inflammatory positive feedback loop via astrocytes in HAM/TSP

The main feature of Human T-lymphotropic virus type I (HTLV-1) -associated myelopathy/tropical spastic paraparesis (HAM/TSP) pathogenesis is a virus-induced hyperactive immune response that produces chronic inflammation in the central nervous system (CNS), but the mechanism by which HTLV-1 deregulates the immune response is unknown. We recently reported a high frequency of HTLV-1-infected CCR4+ cells, including regulatory T cells. We showed that HTLV-1 induces a Th1-like state in these CCR4+ cells via T-bet expression. We have also found that CXCL10 plays an important role in a positive feedback loop that maintains inflammation in the CNS. Astrocytes, which were found to be the main producers of CXCL10 in the CNS, are another key player in the loop. In short, we postulate that infected CCR4+ Th1-like T cells produce interferon-γ, which stimulates astrocytes to produce CXCL10. We now have a much better understanding of the molecular mechanisms at play in HAM/TSP pathogenesis.

Defining CD8+ T cells that provide the proliferative burst after PD-1 therapy.

Chronic viral infections are characterized by a state of CD8+ T-cell dysfunction that is associated with expression of the programmed cell death 1 (PD-1) inhibitory receptor. A better understanding of the mechanisms that regulate CD8+ T-cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8+ T cells. Here we identify a population of virus-specific CD8+ T cells that proliferate after blockade of the PD-1 inhibitory pathway in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These LCMV-specific CD8+ T cells expressed the PD-1 inhibitory receptor, but also expressed several costimulatory molecules such as ICOS and CD28. This CD8+ T-cell subset was characterized by a unique gene signature that was related to that of CD4+ T follicular helper (TFH) cells, CD8+ T cell memory precursors and haematopoietic stem cell progenitors, but that was distinct from that of CD4+ TH1 cells and CD8+ terminal effectors. This CD8+ T-cell population was found only in lymphoid tissues and resided predominantly in the T-cell zones along with naive CD8+ T cells. These PD-1+CD8+ T cells resembled stem cells during chronic LCMV infection, undergoing self-renewal and also differentiating into the terminally exhausted CD8+ T cells that were present in both lymphoid and non-lymphoid tissues. The proliferative burst after PD-1 blockade came almost exclusively from this CD8+ T-cell subset. Notably, the transcription factor TCF1 had a cell-intrinsic and essential role in the generation of this CD8+ T-cell subset. These findings provide a better understanding of T-cell exhaustion and have implications in the optimization of PD-1-directed immunotherapy in chronic infections and cancer.

Tolerance of Tumor-Specific T cells in Melanoma Metastases.

Tolerance of Tumor-Specific T cells in Melanoma Metastases.

HTLV-1 induces a Th1-like state in CD4+CCR4+ T cells.

Human T-lymphotropic virus type 1 (HTLV-1) is linked to multiple diseases, including the neuroinflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T cell leukemia/lymphoma. Evidence suggests that HTLV-1, via the viral protein Tax, exploits CD4+ T cell plasticity and induces transcriptional changes in infected T cells that cause suppressive CD4+CD25+CCR4+ Tregs to lose expression of the transcription factor FOXP3 and produce IFN-γ, thus promoting inflammation. We hypothesized that transformation of HTLV-1-infected CCR4+ T cells into Th1-like cells plays a key role in the pathogenesis of HAM/TSP. Here, using patient cells and cell lines, we demonstrated that Tax, in cooperation with specificity protein 1 (Sp1), boosts expression of the Th1 master regulator T box transcription factor (T-bet) and consequently promotes production of IFN-γ. Evaluation of CSF and spinal cord lesions of HAM/TSP patients revealed the presence of abundant CD4+CCR4+ T cells that coexpressed the Th1 marker CXCR3 and produced T-bet and IFN-γ. Finally, treatment of isolated PBMCs and CNS cells from HAM/TSP patients with an antibody that targets CCR4+ T cells and induces cytotoxicity in these cells reduced both viral load and IFN-γ production, which suggests that targeting CCR4+ T cells may be a viable treatment option for HAM/TSP.

GMP protocol to gene-engineer and process human T-cells revisited: medium critically determines yield, function and differentiation state of CD8+ T-cells

GMP protocol to gene-engineer and process human T-cells revisited: medium critically determines yield, function and differentiation state of CD8+ T-cells

Antigen Targeting to Plasmacytoid Dendritic Cells via Siglec-H Inhibits Th Cell-Dependent Autoimmunity

Plasmacytoid dendritic cells (PDCs) have been shown to present Ags and to contribute to peripheral immune tolerance and to Ag-specific adaptive immunity. However, modulation of adaptive immune responses by selective Ag targeting to PDCs with the aim of preventing autoimmunity has not been investigated. In the current study, we demonstrate that in vivo Ag delivery to murine PDCs via the specifically expressed surface molecule sialic acid binding Ig-like lectin H (Siglec-H) inhibits Th cell and Ab responses in the presence of strong immune stimulation in an Ag-specific manner. Correlating with sustained low-level MHC class II-restricted Ag presentation on PDCs, Siglec-H-mediated Ag delivery induced a hyporesponsive state in CD4(+) T cells leading to reduced expansion and Th1/Th17 cell polarization without conversion to Foxp3(+) regulatory T cells or deviation to Th2 or Tr1 cells. Siglec-H-mediated delivery of a T cell epitope derived from the autoantigen myelin oligodendrocyte glycoprotein to PDCs effectively delayed onset and reduced disease severity in myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis by interfering with the priming phase without promoting the generation or expansion of myelin oligodendrocyte glycoprotein-specific Foxp3(+) regulatory T cells. We conclude that Ag delivery to PDCs can be harnessed to inhibit Ag-specific immune responses and prevent Th cell-dependent autoimmunity.

Abstract CN08-04: Testing cancer vaccines in the setting of premalignant disease: State of immunity and determinants of response

Abstract The overarching hypothesis we are testing is that the best therapeutic approach to cancer is to prevent it either by preventing development of precursor lesions in high-risk individuals or arresting their progression from early lesions to invasive cancer. In the history of medicine, the most effective disease prevention has been achieved through vaccination. There is now solid evidence that tumors are recognized by the immune system and their development can be stopped or controlled long term through a process known as immunosurveillance. Immune recognition and tumor elimination are mediated by the adaptive immune system and directed against specific tumor antigens. We have explored the potential of one such antigen, MUC1, to be a good immunogen as well as a good target of anti-tumor immunity. The experiments have involved in vitro trials, animal models and Phase I and II clinical trials. All MUC1 vaccines tested by us and others have been “therapeutic,” administered to patients with late stage cancer and often after failing standard toxic therapies. In that setting there was very low immunogenicity and limited therapeutic efficacy. It is now clear that the immune system of a cancer patient is under the influence of multiple stress pathways, both tumor induced and host induced, which have a profound immunosuppressive effect, especially on the adaptive immune cells responsible for eliminating tumor cells. We took advantage of the fact that MUC1 that is abnormally expressed on tumor cells is also abnormally expressed on precursor lesions that can progress to cancer. For example, MUC1 is a tumor antigen on colon tumors but also abnormally expressed on all different types of colonic polyps, precursors to colon cancer. We conducted a clinical trial testing a MUC1 vaccine in individuals diagnosed with villous colonic adenomas, the immediate precursor lesions for colon cancer. Our hypothesis was that the immune system of these individuals would not have experienced the stress pathways associated with the cancer microenvironment and thus would generate a good immune response to the vaccine, which could prevent adenoma recurrence or their progression to colon cancer. We vaccinated 40 individuals with a 100aa-long MUC1 peptide combined with the TLR3 agonist adjuvant Poly-ICLC (HiltonolÒ). The vaccine was given at Day 0, week 2, week 10 and week 52 (1-year booster). 47% of individuals responded vigorously to the vaccine as measured by anti-MUC1 IgG. All responders had a vigorous memory response at 1 year. There was no toxicity of any kind. We also focused our attention on the 53% who were non-responders. There was no correlation between response to the vaccine and age or race and only a slight correlation with gender. The surprise came when we examined the immunocompetence of these individuals by evaluating the state of CD4 and CD8 T cells and the presence or absence of Treg and MDSCs. Treg and MDSC have been found in increased numbers at the tumor site and in circulation of advanced cancer patients. They have not been reported in people with premalignant lesions. We found a highly statistically significant correlation between high percentages of MDSCs in the blood and non-responsiveness to the vaccine. We also found that, unlike in cancer, there was no increase in Treg in premalignancy. Furthermore, again unlike in cancer patients, once MDSCs are removed, the T cells function normally and have a normal effector phenotype rather than the phenotype of exhausted T cells. We draw three important conclusions from this trial: 1) the MUC1 plus Poly-ICLC adjuvant is an immunogenic vaccine; 2) progressive premalignant disease can also create a “stressful” environment that can interfere with effective immunosurveillance. Cancer vaccines should be administered before MDSC expand or in combination with treatments that would control or eliminate MDSC function. Citation Information: Cancer Prev Res 2011;4(10 Suppl):CN08-04.

Distinct microRNA signatures in human lymphocyte subsets and enforcement of the naive state in CD4+ T cells by the microRNA miR-125b

MicroRNAs are small noncoding RNAs that regulate gene expression post-transcriptionally. Here we applied microRNA profiling to 17 human lymphocyte subsets to identify microRNA signatures that were distinct among various subsets and different from those of mouse lymphocytes. One of the signature microRNAs of naive CD4+ T cells, miR-125b, regulated the expression of genes encoding molecules involved in T cell differentiation, including IFNG, IL2RB, IL10RA and PRDM1. The expression of synthetic miR-125b and lentiviral vectors encoding the precursor to miR-125b in naive lymphocytes inhibited differentiation to effector cells. Our data provide an 'atlas' of microRNA expression in human lymphocytes, define subset-specific signatures and their target genes and indicate that the naive state of T cells is enforced by microRNA.

Role of antigen persistence and dose for CD4+ T-cell exhaustion and recovery (159.7)

Abstract It is currently not understood how some chronic infections exhaust antigen-specific T cells over time and how different pathogen components contribute to the exhausted state. Here, we dissected the behavior of primed CD4+ T cells exposed to persistent antigen using an inducible transgenic mouse system that allowed us to control antigen presentation as the only experimental variable independent of persistent inflammation and disease progression. In this system presentation of an MHC-II presented antigen is restricted to dendritic cells so that confounding B, CD8+ T, or innate cell responses are not triggered. When antigen presentation was extended beyond the expansion phase, primed CD4+ T cells survived, but exhibited reduced memory functionality in terms of their proliferative capacity and cytokine expression potential. The effect was antigen dose and time dependent, not associated with increased PD-1 expression or reduced calcium influx, but with impaired Jun phosphorylation in response to TCR engagement. Upon antigen removal, the cells regained the ability to proliferate, but remained unable to produce high levels of IL-2 and TNF-α. These data show that persistent antigen at a high dose rapidly induces a dysfunctional state in CD4+ T cells that is only partially reversible upon antigen removal. At a low dose, however, antigen has to persist longer before T cell impairment becomes detectable.

Role of antigen persistence and dose for CD4+T-cell exhaustion and recovery

It is currently not understood how some chronic infections exhaust antigen-specific T cells over time and which pathogen components contribute to exhaustion. Here, we dissected the behavior of primed CD4(+) T cells exposed to persistent antigen using an inducible transgenic mouse system that allowed us to control antigen presentation as the only experimental variable, independent of the persistent inflammation and disease progression that complicate infectious models. Moreover, this system restricted antigen presentation to dendritic cells (DCs) and avoided confounding B, CD8(+) T, or innate cell responses. When antigen presentation was extended beyond the expansion phase, primed CD4(+) T cells survived, but exhibited reduced memory functionality in terms of their proliferative capacity and cytokine expression potential. The effect was antigen dose and time dependent, not associated with increased PD-1 expression or reduced calcium influx, but impaired Jun phosphorylation in response to TCR engagement. Upon antigen removal, the cells regained the ability to proliferate, but remained unable to produce high levels of IL-2 and TNF-α. These data show that persistent antigen by itself rapidly induces a dysfunctional state in CD4(+) T cells that is only partially reversible upon antigen removal. These findings have implications for vaccine optimization and for the possible reinvigoration of CD4(+) T cells during chronic infection.

Effector T cell plasticity: flexibility in the face of changing circumstances

As more states of CD4 T cell differentiation are uncovered, their flexibility is also beginning to be recognized. Components that control the plasticity of CD4 T cell populations include cellular conditions, clonality, transcriptional circuitry and chromatin modifications. Appearance of cellular flexibility may arise from truly flexible genetic programs or, alternatively, from heterogeneous populations. New tools will be needed to define the rules that allow or prohibit cellular transitions.

Characterization of the Alpha Interferon-Induced Postentry Block to HIV-1 Infection in Primary Human Macrophages and T Cells

Type I interferon (IFN) inhibits virus replication by activating multiple antiviral mechanisms and pathways. It has long been recognized that alpha interferon (IFN-alpha) can potently block both early and late stages of HIV-1 replication. The mechanistic basis for the early block(s) to infection is unknown, as is the identity of the participating antiviral factor(s). Here, we define the effect(s) of IFN-alpha on HIV-1 infection of primary human macrophages and CD4(+) T cells, as well as several monocytic and T-cell lines. We demonstrate that IFN-alpha treatment of macrophages, THP-1 cells, and, to a lesser extent, primary CD4(+) T cells markedly inhibits infection, whereas the effects are minimal in CD4(+) T-cell lines. Virus entry is essentially unaffected by IFN-alpha, but substantial decreases (sometimes >99%) in nascent cDNA accumulation correlate closely with losses in infectivity. Interestingly, proteasome inhibitors rescue viral cDNA accumulation, revealing a link between the ubiquitin-proteasome system and IFN-alpha-induced viral restriction. We also found that diverse primate and nonprimate retroviruses were susceptible to suppression by IFN-alpha. Importantly, all the primary and immortalized cells used here are proficient at responding to IFN-alpha, as judged by the induced expression of numerous IFN-stimulated genes, including PKR and OAS1, indicating that a general deficiency in IFN-alpha responsiveness does not underlie IFN-alpha's inability to elicit an antiviral state in CD4(+) T-cell lines. Rather, we speculate that IFN-alpha fails to induce antiretroviral factors in these cells and that comparative transcriptional profiling with responsive cells, such as macrophages, invokes a strategy for identifying new host-encoded antiviral effectors.

Abstract SY03-02: Wnt signaling generates “stem-like” self-renewing T cells that can eradicate tumors

Abstract SY03-02: Wnt signaling generates “stem-like” self-renewing T cells that can eradicate tumors