Sandra Aung

Uncoupling of Proliferative Potential and Gain of Effector Function by CD8+ T Cells Responding to Self-Antigens

Professional antigen-presenting cells (APCs) are capable of transporting self-antigens from peripheral tissues to secondary lymphoid organs where they are presented to potentially autoreactive CD8+ T cells. In the absence of an inflammatory response, this results in immune tolerance. The presence of activated, antigen-specific CD4+ T cells converts this tolerogenic encounter into an immunogenic one by promoting extensive proliferation of CD8+ T cells and their development into effectors. Surprisingly, activation of APCs with an agonistic antibody specific for CD40 could not substitute for CD4+ help in this task. Anti-CD40 induced recruitment of dendritic cells expressing high levels of B7 costimulatory molecules into the lymph nodes, which in turn, greatly enhanced activation and expansion of CD8+ T cells. However, these activated CD8+ cells did not demonstrate effector function. We conclude that proliferative potential and gain of effector function are separable events in the differentiation program of CD8+ T cells.

Memory CD8+ T Cells Undergo Peripheral Tolerance

Memory T cells differ from naive T cells in that they respond more rapidly and in greater numbers. In addition, memory T cells are generally believed to be less susceptible to tolerance induction than naive T cells. In this study, we show that this is not the case. Using two different methods of tolerance induction, peptide-induced tolerance and crosstolerance, we present evidence that memory CD8(+) T cells are as susceptible to tolerance as naive cells. These results have a direct impact on manipulating T cell responses to self-antigens in order to improve immunotherapy of cancer and autoimmune diseases.

Alternative Mechanisms of Respiratory Syncytial Virus Clearance in Perforin Knockout Mice Lead to Enhanced Disease

ABSTRACT Virus-specific cytotoxic T lymphocytes are key effectors for the clearance of virus-infected cells and are required for the normal clearance of respiratory syncytial virus (RSV) in mice. Although perforin/granzyme-mediated lysis of infected cells is thought to be the major molecular mechanism used by CD8+ cytotoxic T lymphocytes for elimination of virus, its role in RSV has not been reported. Here, we show that viral clearance in perforin knockout (PKO) mice is slightly delayed but that both PKO and wild-type mice clear virus by day 10, suggesting an alternative mechanism of RSV clearance. Effector T cells from the lungs of both groups of mice were shown to lyse Fas (CD95)-overexpressing target cells in greater numbers than target cells expressing low levels of Fas, suggesting that Fas ligand (CD95L)-mediated target cell lysis was occurring in vivo. This cell lysis was associated with a delay in RSV-induced disease in PKO mice compared to the time of disease onset for wild-type controls, which correlated with increased and prolonged production of gamma interferon and tumor necrosis factor alpha levels in PKO mice. We conclude that while perforin is not necessary for the clearance of primary RSV infection, the use of alternative CTL target cell killing mechanisms is less efficient and can lead to enhanced disease.

IL-4 Diminishes Perforin-Mediated and Increases Fas Ligand-Mediated Cytotoxicity In Vivo

CTL have evolved two major mechanisms for target cell killing: one mediated by perforin/granzyme secretion and the other by Fas/Fas ligand (L) interaction. Although cytokines are integral to the development of naive CTL into cytolytic effectors, the role of cytokines on mechanisms of CTL killing is just emerging. In this study, we evaluate the effects of IL-4 in Fas(CD95)/FasL(CD95L)-mediated killing of Fas-overexpressing target cells. Recombinant vaccinia viruses (vv) were constructed to express respiratory syncytial virus M2 Ag alone (vvM2) or coexpress M2 and IL-4 (vvM2/IL-4). MHC-matched Fas-overexpressing target cells (L1210Fas+) were used to measure both perforin- and FasL-mediated killing pathways. In contrast to Fas-deficient (L1210Fas−) target cells, effectors from vvM2/IL-4-immunized mice were able to lyse L1210Fas+ target cells with similar magnitude as vvM2-infected mice. Addition of EGTA/Mg2+ revealed that effectors from vvM2/IL-4-infected mice primarily lyse targets by a Ca2+-independent Fas/FasL pathway. Analysis of FasL expression by flow cytometry showed that IL-4 increased cell surface FasL expression on CD4+ and CD8+ splenocytes, with peak expression on day 4 after infection. These data demonstrate that IL-4 increases FasL expression on T cells, resulting in a shift of the mechanism of CTL killing from a dominant perforin-mediated cytolytic pathway to a dominant FasL-mediated cytolytic pathway.

Treatment with Anti-LFA-1 Delays the CD8+ Cytotoxic-T-Lymphocyte Response and Viral Clearance in Mice with Primary Respiratory Syncytial Virus Infection

ABSTRACT Cytotoxic T lymphocytes (CTLs) play an important role in the immune response against respiratory syncytial virus (RSV) infection. The cell surface molecule lymphocyte function-associated antigen 1 (LFA-1) is an important contributor to CTL activation, CTL-mediated direct cell lysis, and lymphocyte migration. In an attempt to determine the role of LFA-1 during RSV infection, we treated BALB/c mice with monoclonal antibodies to LFA-1 at days −1, +1, and +4 relative to primary RSV infection. Anti-LFA-1 treatment during primary RSV infection led to reduced illness and delayed clearance of virus-infected cells. CTLs from RSV-infected mice that were treated with anti-LFA-1 exhibited diminished cytolytic activity and reduced gamma interferon production. In addition, studies with BrdU (5-bromo-2′-deoxyuridine)- and CFSE [5-(and 6)-carboxyfluorescein diacetate succinimidyl ester]-labeled lymphocytes showed that anti-LFA-1 treatment led to delayed proliferation during RSV infection. These results indicate that LFA-1 plays a critical role in the initiation of the immune response to RSV infection by facilitating CTL activation. These results may prove useful in the development of new therapies to combat RSV infection or other inflammatory diseases.

Preliminary analysis of immune responses in patients enrolled in a Phase II trial of Cyclophosphamide with Allogenic DRibble Vaccine Alone (DPV-001) or with GM-CSF or Imiquimod for adjuvant treatment of Stage IIIA or IIIB NSCLC

Preliminary analysis of immune responses in patients enrolled in a Phase II trial of cyclophosphamide with allogenic dribble vaccine alone (DPV-001) or with GM-CSF or imiquimod for adjuvant treatment of stage IIIa or IIIb NSCLC Rachel Sanborn, Brian Boulmay, Rui Li, Bradley Spieler, Kyle Happel, Christopher Paustian, Tarsem Mougdil, Zipei Feng, Christopher Dubay, Brenda Fisher, Yoshinobu Koguchi, Sandra Aung, Eileen Mederos, Carlo Bifulco, Michael McNamara, Keith S Bahjat, William Redmond, Augusto C Ochoa, Hong Ming Hu, Bernard Fox, Walter Urba, Traci Hilton

Autophagosome-based strategy to monitor apparent tumor-specific CD8 T cells in patients with prostate cancer

ABSTRACT The immune system plays an essential role in eradicating cancer in concert with various treatment modalities. In the absence of autologous tumor material, no standardized method exists to assess T cell responses against the many antigens that may serve as cancer rejection antigens. Thus, development of methods to screen for therapy-induced anti-tumor responses is a high priority that could help tailor therapy. Here we tested whether a tumor-derived antigen source called DRibbles®, which contain a pool of defective ribosomal products (DRiPs), long-lived and short-lived proteins (SLiPs) and danger-associated molecular patterns (DAMPs), can be used to identify tumor-associated antigen (TAA)-specific responses in patients before or after immunotherapy treatment. Protein content, gene expression and non-synonymous – single nucleotide variants (ns-SNVs) present in UbiLT3 DRibbles were compared with prostate adenocarcinomas and the prostate GVAX vaccine cell lines (PC3/LNCaP). UbiLT3 DRibbles were found to share proteins, as well as match tumor sequences for ns-SNVs with prostate adenocarcinomas and with the cell lines PC3 and LNCaP. UbiLT3 DRibbles were used to monitor anti-tumor responses in patients vaccinated with allogeneic prostate GVAX. UbiLT3-DRibble-reactive CD8+ T-cell responses were detected in post-vaccine PBMC of 6/12 patients (range 0.85–22% of CD8+ cells) after 1 week in vitro stimulation (p = 0.007 vs. pre-vaccine). In conclusion, a cancer-derived autophagosome-enriched preparation, packaging over 100 proteins over-expressed in prostate cancer into microvesicles containing DAMPs, could be used to identify CD8+ T cells in peripheral blood from patients after prostate GVAX vaccination and may represent a general method to monitor anti-cancer T cell responses following immunotherapy.

Efficacy and safety of high-dose interleukin-2 treatment in patients with a history of brain metastases from renal cell carcinoma

Meeting abstracts The efficacy and safety of high dose IL-2 therapy in patients with brain metastases due to renal cell carcinoma is not well characterized. Data were prospectively collected in a registry of 371 patients with RCC receiving high-dose IL-2, including 18 patients with a history of

Open-label, randomized, multi-center study comparing the sequence of high dose Aldesleukin (Proleukin® (HD IL-2) and Ipilimumab Yervoy® ) in patients with metastatic melanoma (proclivity 02)

Meeting abstracts To investigate whether the sequence of HD IL-2 and a checkpoint inhibitor, Ipilimumab, will have additive or synergistic efficacy or toxicity when used in rapid sequence. Adult patients with Stage IV or unresectable Stage III metastatic melanoma who are eligible to receive HD IL-