Scientific Resources

The persistence of latent HIV proviruses in long-lived CD4(+) T cells despite antiretroviral therapy (ART) is a major obstacle to viral eradication. Because current candidate latency-reversing agents (LRAs) induce HIV transcription,but fail to clear these cellular reservoirs,new approaches for killing these reactivated latent HIV reservoir cells are urgently needed. HIV latency depends upon the transcriptional quiescence of the integrated provirus and the circumvention of immune defense mechanisms. These defenses include cell-intrinsic innate responses that use pattern-recognition receptors (PRRs) to detect viral pathogens,and that subsequently induce apoptosis of the infected cell. Retinoic acid (RA)-inducible gene I (RIG-I,encoded by DDX58) forms one class of PRRs that mediates apoptosis and the elimination of infected cells after recognition of viral RNA. Here we show that acitretin,an RA derivative approved by the US Food and Drug Administration (FDA),enhances RIG-I signaling ex vivo,increases HIV transcription,and induces preferential apoptosis of HIV-infected cells. These effects are abrogated by DDX58 knockdown. Acitretin also decreases proviral DNA levels in CD4(+) T cells from HIV-positive subjects on suppressive ART,an effect that is amplified when combined with suberoylanilide hydroxamic acid (SAHA),a histone deacetylase inhibitor. Pharmacological enhancement of an innate cellular-defense network could provide a means by which to eliminate reactivated cells in the latent HIV reservoir. View Publication

Class I HLA molecules mark infected cells for immune targeting by presenting pathogen-encoded peptides on the cell surface. Characterization of viral peptides unique to infected cells is important for understanding CD8(+) T cell responses and for the development of T cell-based immunotherapies. Having previously reported a series of West Nile virus (WNV) epitopes that are naturally presented by HLA-A*02:01,in this study we generated TCR mimic (TCRm) mAbs to three of these peptide/HLA complexes-the immunodominant SVG9 (E protein),the subdominant SLF9 (NS4B protein),and the immunorecessive YTM9 (NS3 protein)-and used these TCRm mAbs to stain WNV-infected cell lines and primary APCs. TCRm staining of WNV-infected cells demonstrated that the immunorecessive YTM9 appeared several hours earlier and at 5- to 10-fold greater density than the more immunogenic SLF9 and SVG9 ligands,respectively. Moreover,staining following inhibition of the TAP demonstrated that all three viral ligands were presented in a TAP-dependent manner despite originating from different cellular compartments. To our knowledge,this study represents the first use of TCRm mAbs to define the kinetics and magnitude of HLA presentation for a series of epitopes encoded by one virus,and the results depict a pattern whereby individual epitopes differ considerably in abundance and availability. The observations that immunodominant ligands can be found at lower levels and at later time points after infection suggest that a reevaluation of the factors that combine to shape T cell reactivity may be warranted. View Publication

Many pathogens evade cytotoxic T lymphocytes (CTLs) by downregulating HLA molecules on infected cells,but the loss of HLA can trigger NK cell-mediated lysis. HIV-1 is thought to subvert CTLs while preserving NK cell inhibition by Nef-mediated downregulation of HLA-A and -B but not HLA-C molecules. We find that HLA-C is downregulated by most primary HIV-1 clones,including transmitted founder viruses,in contrast to the laboratory-adapted NL4-3 virus. HLA-C reduction is mediated by viral Vpu and reduces the ability of HLA-C restricted CTLs to suppress viral replication in CD4+ cells in vitro. HLA-A/B are unaffected by Vpu,and primary HIV-1 clones vary in their ability to downregulate HLA-C,possibly in response to whether CTLs or NK cells dominate immune pressure through HLA-C. HIV-2 also suppresses HLA-C expression through distinct mechanisms,underscoring the immune pressure HLA-C exerts on HIV. This viral immune evasion casts new light on the roles of CTLs and NK cells in immune responses against HIV. View Publication

CD4 and CD8 T lymphocyte activation requires the generation of sufficient energy to support new biosynthetic demands. Following T cell receptor (TCR) engagement,these requirements are met by an increased glycolysis,due,at least in part,to induction of the Glut1 glucose transporter. As Glut1 is upregulated on tumor cells in response to hypoxia,we assessed whether surface Glut1 levels regulate the antigen responsiveness of human T lymphocytes in both hypoxic and atmospheric oxygen conditions. Notably,Glut1 upregulation in response to TCR stimulation was significantly higher in T lymphocytes activated under hypoxic as compared to atmospheric oxygen conditions. Furthermore,TCR-stimulated human T lymphocytes sorted on the basis of Glut1-Lo and Glut1-Hi profiles maintained distinct characteristics,irrespective of the oxygen tension. While T cells activated in hypoxia divided less than those activated in atmospheric oxygen,Glut1-Hi lymphocytes exhibited increased effector phenotype acquisition,augmented proliferation,and an inverted CD4/CD8 ratio in both oxygen conditions. Moreover,Glut1-Hi T lymphocytes exhibited a significantly enhanced ability to produce IFN-γ and this secretion potential was completely dependent on continued glycolysis. Thus,Glut1 surface levels identify human T lymphocytes with distinct effector functions in both hypoxic and atmospheric oxygen tensions. View Publication

Surgical and medical androgen deprivation therapy (ADT) is a cornerstone for prostate cancer treatment,but relapse usually occurs. We herein show that orchiectomy synergizes with immunotherapy,whereas the more widely used treatment of medical ADT involving androgen receptor (AR) antagonists suppresses immunotherapy. Furthermore,we observed that the use of medical ADT could unexpectedly impair the adaptive immune responses through interference with initial T cell priming rather than in the reactivation or expansion phases. Mechanistically,we have revealed that inadvertent immunosuppression might be potentially mediated by a receptor shared with γ-aminobutyric acid. Our data demonstrate that the timing and dosing of antiandrogens are critical to maximizing the antitumor effects of combination therapy. This study highlights an underappreciated mechanism of AR antagonist-mediated immunosuppression and provides a new strategy to enhance immune response and prevent the relapse of advanced prostate cancer. View Publication

BACKGROUND AND OBJECTIVES Our post-thaw cell recovery rates differed substantially in interlaboratory comparisons of identical samples,potentially due to different temperatures during cell staining. MATERIALS AND METHODS Viable CD34(+) cells and leucocyte (WBC) subtypes were quantified by multiparameter single-platform flow cytometry in leucapheresis products collected from 30 adult lymphoma and myeloma patients,and from 10 paediatric patients. After thawing,cells were prepared for analysis within 30 min between thawing and acquisition,at either 4°C or at room temperature. RESULTS For cell products cryopreserved in conventional freezing medium (10% final DMSO),viable cell recovery was clearly lower after staining at 4°C than at RT. Of all WBC subtypes analysed,CD4(+) T cells showed the lowest median recovery of 4% (4°C) vs. 25% (RT),followed by CD3,CD34 and CD8 cells. The recovery was highest for CD3γδ cells with 44% (4°C) vs. 71% (RT). In the 10 samples cryopreserved in synthetic freezing medium (5% final DMSO),median recovery rates were 89% for viable CD34 (both at 4°C and RT) and 79% (4°C) vs 68% (RT) for WBC. CONCLUSIONS The post-thaw environment and,potentially,the cryoprotectant impact the outcome of cell enumeration,and results from the analysis tube may not be representative of the cells infused into a patient. View Publication

Immune recognition by T cells relies on the presentation of pathogen-derived peptides by infected cells,but the persistence of chronic infections calls for new approaches to modulate immune recognition. Ag cross-presentation,the process by which pathogen Ags are internalized,degraded,and presented by MHC class I,is crucial to prime CD8 T cell responses. The original degradation of Ags is performed by pH-dependent endolysosomal cathepsins. In this article,we show that HIV protease inhibitors (PIs) prescribed to HIV-infected persons variably modulate cathepsin activities in human APCs,dendritic cells and macrophages,and CD4 T cells,three cell subsets infected by HIV. Two HIV PIs acted in two complementary ways on cathepsin hydrolytic activities: directly on cathepsins and indirectly on their regulators by inhibiting Akt kinase activities,reducing NADPH oxidase 2 activation,and lowering phagolysosomal reactive oxygen species production and pH,which led to enhanced cathepsin activities. HIV PIs modified endolysosomal degradation and epitope production of proteins from HIV and other pathogens in a sequence-dependent manner. They altered cross-presentation of Ags by dendritic cells to epitope-specific T cells and T cell-mediated killing. HIV PI-induced modulation of Ag processing partly changed the MHC self-peptidome displayed by primary human cells. This first identification,to our knowledge,of prescription drugs modifying the regulation of cathepsin activities and the MHC-peptidome may provide an alternate therapeutic approach to modulate immune recognition in immune disease beyond HIV. View Publication

HIV-infected slow progressors (SP) represent a heterogeneous group of subjects who spontaneously control HIV infection without treatment for several years while showing moderate signs of disease progression. Under conditions that remain poorly understood,a subgroup of these subjects experience failure of spontaneous immunological and virological control. Here we determined the frequency of SP subjects who showed loss of HIV control within our Canadian Cohort of HIV(+) Slow Progressors and identified the proinflammatory cytokine IL-32 as a robust biomarker for control failure. Plasmatic levels of the proinflammatory isoforms of IL-32 (mainly β and γ) at earlier clinic visits positively correlated with the decline of CD4 T-cell counts,increased viral load,lower CD4/CD8 ratio and levels of inflammatory markers (sCD14 and IL-6) at later clinic visits. We present here a proof-of-concept for the use of IL-32 as a predictive biomarker for disease progression in SP subjects and identify IL-32 as a potential therapeutic target. View Publication

Immune tolerance is executed partly by Foxp3(+)regulatory T (Treg) cells,which suppress autoreactive T cells. In autoimmune type 1 diabetes (T1D) impaired tolerance promotes destruction of insulin-producing β-cells. The development of autoantigen-specific vaccination strategies for Foxp3(+)Treg-induction and prevention of islet autoimmunity in patients is still in its infancy. Here,using human haematopoietic stem cell-engrafted NSG-HLA-DQ8 transgenic mice,we provide direct evidence for human autoantigen-specific Foxp3(+)Treg-induction in vivo. We identify HLA-DQ8-restricted insulin-specific CD4(+)T cells and demonstrate efficient human insulin-specific Foxp3(+)Treg-induction upon subimmunogenic vaccination with strong agonistic insulin mimetopes in vivo. Induced human Tregs are stable,show increased expression of Treg signature genes such as Foxp3,CTLA4,IL-2Rα and TIGIT and can efficiently suppress effector T cells. Such Foxp3(+)Treg-induction does not trigger any effector T cells. These T1D vaccine candidates could therefore represent an expedient improvement in the challenge to induce human Foxp3(+)Tregs and to develop novel precision medicines for prevention of islet autoimmunity in children at risk of T1D. View Publication

Multiple sclerosis (MS) is caused by T cells that are reactive for brain antigens. In experimental autoimmune encephalomyelitis,the animal model for MS,myelin-reactive T cells initiate the autoimmune process when entering the nervous tissue and become reactivated upon local encounter of their cognate CNS antigen. Thereby,the strength of the T-cellular reactivation process within the CNS tissue is crucial for the manifestation and the severity of the clinical disease. Recently,B cells were found to participate in the pathogenesis of CNS autoimmunity,with several diverse underlying mechanisms being under discussion. We here report that B cells play an important role in promoting the initiation process of CNS autoimmunity. Myelin-specific antibodies produced by autoreactive B cells after activation in the periphery diffused into the CNS together with the first invading pathogenic T cells. The antibodies accumulated in resident antigen-presenting phagocytes and significantly enhanced the activation of the incoming effector T cells. The ensuing strong blood-brain barrier disruption and immune cell recruitment resulted in rapid manifestation of clinical disease. Therefore,myelin oligodendrocyte glycoprotein (MOG)-specific autoantibodies can initiate disease bouts by cooperating with the autoreactive T cells in helping them to recognize their autoantigen and become efficiently reactivated within the immune-deprived nervous tissue. View Publication

Human melanoma cells express various tumour antigens that are recognized by CD8(+) cytotoxic T lymphocytes (CTLs) and elicit tumour-specific responses in vivo. However,natural and therapeutically enhanced CTL responses in melanoma patients are of limited efficacy. The mechanisms underlying CTL effector phase failure when facing melanomas are still largely elusive. Here we show that,on conjugation with CTL,human melanoma cells undergo an active late endosome/lysosome trafficking,which is intensified at the lytic synapse and is paralleled by cathepsin-mediated perforin degradation and deficient granzyme B penetration. Abortion of SNAP-23-dependent lysosomal trafficking,pH perturbation or impairment of lysosomal proteolytic activity restores susceptibility to CTL attack. Inside the arsenal of melanoma cell strategies to escape immune surveillance,we identify a self-defence mechanism based on exacerbated lysosome secretion and perforin degradation at the lytic synapse. Interfering with this synaptic self-defence mechanism might be useful in potentiating CTL-mediated therapies in melanoma patients. View Publication

Ab-mediated lymphoablation is commonly used in solid organ and hematopoietic cell transplantation. However,these strategies fail to control pathogenic memory T cells efficiently and to improve long-term transplant outcomes significantly. Understanding the mechanisms of T cell reconstitution is critical for enhancing the efficacy of Ab-mediated depletion in sensitized recipients. Using a murine analog of anti-thymocyte globulin (mATG) in a mouse model of cardiac transplantation,we previously showed that peritransplant lymphocyte depletion induces rapid memory T cell proliferation and only modestly prolongs allograft survival. We now report that T cell repertoire following depletion is dominated by memory CD4 T cells. Additional depletion of these residual CD4 T cells severely impairs the recovery of memory CD8 T cells after mATG treatment. The CD4 T cell help during CD8 T cell recovery depends on the presence of B cells expressing CD40 and intact CD40/CD154 interactions. The requirement for CD4 T cell help is not limited to the use of mATG in heart allograft recipients,and it is observed in nontransplanted mice and after CD8 T cell depletion with mAb instead of mATG. Most importantly,limiting helper signals increases the efficacy of mATG in controlling memory T cell expansion and significantly extends heart allograft survival in sensitized recipients. Our findings uncover the novel role for helper memory CD4 T cells during homeostatic CD8 T cell proliferation and open new avenues for optimizing lymphoablative therapies in allosensitized patients. View Publication