PDF file - 198K, Figure 1. Characterization of the anti-OX40 mAb (9B12). Figure 2. Total peripheral lymphocyte counts. Figure 3. Pharmacokinetics of CD134 (anti-OX40) mAb in patients. Figure 4. Direct ex vivo detection of the murine anti-OX40 mAb bound to T cells in treated patients. Figure 5. Regression of a pulmonary metastasis in a patient with renal carcinoma enrolled in cohort 1. Figure 6. Changes in Ki-67 expression within CD4+ and CD8+ T cell subsets examined over time after anti-OX40 from patients in cohorts 1 and 2. Figure 7. Increased proliferation of CD4+ Foxp3- T cells and CD8+ T cells correlates with a decrease or stabilization of tumor burden. Figure 8. Ki-67 expression by monkey CD4+ and CD8+ memory T cells after the administration of anti-OX40 , mouse Immunoglobulin or monkey OX40L:Ig. Figure 9. Determination of the Endpoint Titer for anti-KLH Ab.

PDF file - 68K, Details clinical trial, flow cytometry and monkey experiments referred to in the manuscript.

Supplementary Data from Phenotype and Functional Characterization of Long-term gp100-Specific Memory CD8+ T Cells in Disease-Free Melanoma Patients Before and After Boosting Immunization

The pleiotropic cytokine, transforming growth factor (TGF)-β, and CD4+CD25+Foxp3+ regulatory T cells (Tregs) play a critical role in actively suppressing antitumor immune responses. Evidence shows that TGF-β produced by tumor cells promotes tolerance via expansion of Tregs. Our group previously demonstrated that blockade of TGF-β signaling with a small molecule TGF-β receptor I antagonist (SM16) inhibited primary and metastatic tumor growth in a T cell dependent fashion. In the current study, we evaluated the effect of SM16 on Treg generation and function. Using BALB/c, FoxP3eGFP and Rag−/− mice, we performed FACS analysis to determine if SM16 blocked de novo TGF-β-induced Treg generation in vitro and in vivo. CD4+ T cells from lymph node and spleen were isolated from control mice or mice maintained on SM16 diet, and flow cytometry analysis was used to detect the frequency of CD4+CD25−FoxP3+ and CD4+CD25+FoxP3+ T cells. In vitro suppression assays were used to determine the ability to suppress naive T cell proliferation in vitro of both CD4+CD25+FoxP3+ and CD4+CD25−FoxP3+ T cell sub-populations. We then examined whether SM16 diet exerted an inhibitory effect on primary tumor growth and correlated with changes in FoxP3+expression. ELISA analysis was used to measure IFN-γ levels after 72 h co-culture of CD4+CD25+ T cells from tumor-bearing mice on control or SM16 diet with CD4+CD25− T cells from naive donors. SM16 abrogates TGF-β-induced Treg generation in vitro but does not prevent global homeostatic expansion of CD4+ T cell sub-populations in vivo. Instead, SM16 treatment causes expansion of a population of CD4+CD25−Foxp3+ Treg-like cells without significantly altering the overall frequency of Treg in lymphoreplete naive and tumor-bearing mice. Importantly, both the CD4+CD25−Foxp3+ T cells and the CD4+CD25+Foxp3+ Tregs in mice receiving SM16 diet exhibited diminished ability to suppress naive T cell proliferation in vitro compared to Treg from mice on control diet. These findings suggest that blockade of TGF-β signaling is a potentially useful strategy for blunting Treg function to enhance the anti-tumor response. Our data further suggest that the overall dampening of Treg function may involve the expansion of a quiescent Treg precursor population, which is CD4+CD25−Foxp3+.

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 (R), 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.

Immunophenotyping of peripheral blood by flow cytometry determines changes in the frequency and activation status of peripheral leukocytes during disease and treatment. It has the potential to predict therapeutic efficacy and identify novel therapeutic targets. Whole blood staining utilizes unmanipulated blood, which minimizes artifacts that can occur during sample preparation. However, whole blood staining must also be done on freshly collected blood to ensure the integrity of the sample. Additionally, it is best to prepare antibody cocktails on the same day to avoid potential instability of tandem-dyes and prevent reagent interaction between brilliant violet dyes. Therefore, whole blood staining requires careful standardization to control for intra and inter-experimental variability. Here, we report deployment of an automated liquid handler equipped with a two-dimensional (2D) barcode reader into a standard process of making antibody cocktails for flow cytometry. Antibodies were transferred into 2D barcoded tubes arranged in a 96 well format and their contents compiled in a database. The liquid handler could then locate the source antibody vials by referencing antibody names within the database. Our method eliminated tedious coordination for positioning of source antibody tubes. It provided versatility allowing the user to easily change any number of details in the antibody dispensing process such as specific antibody to use, volume, and destination by modifying the database without rewriting the scripting in the software method for each assay. A proof of concept experiment achieved outstanding inter and intra- assay precision, demonstrated by replicate preparation of an 11-color, 17-antibody flow cytometry assay. These methodologies increased overall throughput for flow cytometry assays and facilitated daily preparation of the complex antibody cocktails required for the detailed phenotypic characterization of freshly collected anticoagulated peripheral blood.

We are interested in various structural aspects of human Carbonic Anhydrase II (hCAII) and the Pyrococcus horikoshii PolII intein (Pho PolII). A combination of analyses including x‐ray crystallography and biochemical assays will be used to study each of the two proteins. We will compare the activity and structure of hCAII to hCAII where the active‐site zinc ions have been replaced with rhenium. Additionally, we will assay both zinc and rhenium hCAII for enzymatic functionality using a p‐NPA hydrolysis assay. Thus far, we have optimized expression in E. coli and purification of hCAII and have assayed for functionality. Our goal with the PolII intein is to obtain structures for the unspliced precursor and the excised intein in order to do structural comparisons. Our lab has recently crystallized the precursor and my focus is on the intein. The PolII precursor, which comes from a sea‐dwelling, thermophillic archaea, was mutated so that a stop codon preceded the poly‐His tag at the C‐terminal end of the intein before expression and purification were optimized. In order to isolate the intein from its remaining N‐extein, we used DTT to facilitate N‐terminal cleavage and will use size exclusion chromatography to separate the products.Grant Funding Source: Supported by the National Science Foundation under grant MCB‐1244089 and by the Dreyfus Foundation.

Meeting abstracts Since it is the site of initial immune activation and priming of antigen-specific T cells, as well as the first location to which tumor cells metastasize, our research focuses on understanding the immune status and tumor-induced suppression within breast cancer (BrCa)-draining

Background We examined the phenotype and function of lymphocytes collected from the peripheral blood (PBL) and tumor (TIL) of patients with two different solid malignancies: colorectal cancer liver metastases (CRLM) and ovarian cancer (OVC). Methods Tumor and corresponding peripheral blood were collected from 16 CRLM and 22 OVC patients; immediately following resection they were processed and analyzed using a multi-color flow cytometry panel. Cytokine mRNA from purified PBL and TIL CD4+ T cells were also analyzed by qPCR. Results Overall, we found similar changes in the phenotypic and cytokine profiles when the TIL were compared to PBL from patients with two different malignancies. The percentage of Treg (CD4+/CD25+/FoxP3+) in PBL and TIL was similar: 8.1% versus 10.2%, respectively in CRLM patients. However, the frequency of Treg in primary OVC TIL was higher than PBL: 19.2% versus 4.5% (p <0.0001). A subpopulation of Treg expressing HLA-DR was markedly increased in TIL compared to PBL in both tumor types, CRLM: 69.0% versus 31.7% (p = 0.0002) and OVC 74.6% versus 37.0% (p <0.0001), which suggested preferential Treg activation within the tumor. The cytokine mRNA profile showed that IL-6, a cytokine known for its immunosuppressive properties through STAT3 upregulation, was increased in TIL samples in patients with OVC and CRLM. Both TIL populations also contained a significantly higher proportion of activated CD8+ T cells (HLA-DR+/CD38+) compared to PBL (CRLM: 30.2% vs 7.7%, (p = 0.0012), OVC: 57.1% vs 12.0%, (p <0.0001)). Conclusion This study demonstrates that multi-color flow cytometry of freshly digested tumor samples reveals phenotypic differences in TIL vs PBL T cell sub-populations. The TIL composition in primary and metastatic tumors from two distinct histologies were remarkably similar, showing a greater proportion of activated/suppressive Treg (HLA-DR+, CD39+, CTLA-4+ and Helios+) and activated cytotoxic T cells (CD8+/HLA-DR+/CD38+) when compared to PBL and an increase in IL-6 mRNA from CD4 TIL.

CD80 expression by APC provides signal 2, a critical element in priming T cell immune responses to antigen. As limited CD80 expression on APC can result in reduced immune responses, strategies that increase CD80 may have benefit. We report here that the autophagosome-enriched vaccine named DRibbles (DRiPs and SLiPs in Blebs), derived from human tumor cells transfected with a plasmid encoding huCD80, are highly efficient at transferring membrane proteins onto human PBMCs. When PBMCs were incubated with a DRibble vaccine derived from a CD80 expressing breast-tumor cell line, a significant increase in surface expression of CD80 was observed on PBMCs within 5 minutes (p<0.001). This effect was time and concentration-dependent and repeatable across multiple donors (N=5) in multiple experiments (N≥16). DRibble vaccine could transfer CD80 onto as high as 60-86.4% of monocytes and 41-86.1% of CD4+ T cells. Transfer of CD80 to CD8 T cells was substantially less effective. Transfer of membrane-associated proteins between leukocyte populations is a well-documented phenomenon, however, this is the first report of transfer of membrane-associated proteins from cell-free autophagosomes. Current efforts are investigating the functional properties associated with increased expression of CD80. Given the critical role of CD80 in augmenting immune responses this provides a novel strategy to further augment the response to DRibble vaccines, which are being explored in clinical trials.

AbstractOX40 is a potent costimulatory receptor that can potentiate T-cell receptor signaling on the surface of T lymphocytes, leading to their activation by a specifically recognized antigen. In particular, OX40 engagement by ligands present on dendritic cells dramatically increases the proliferation, effector function, and survival of T cells. Preclinical studies have shown that OX40 agonists increase antitumor immunity and improve tumor-free survival. In this study, we performed a phase I clinical trial using a mouse monoclonal antibody (mAb) that agonizes human OX40 signaling in patients with advanced cancer. Patients treated with one course of the anti-OX40 mAb showed an acceptable toxicity profile and regression of at least one metastatic lesion in 12 of 30 patients. Mechanistically, this treatment increased T and B cell responses to reporter antigen immunizations, led to preferential upregulation of OX40 on CD4+ FoxP3+ regulatory T cells in tumor-infiltrating lymphocytes, and increased the antitumor reactivity of T and B cells in patients with melanoma. Our findings clinically validate OX40 as a potent immune-stimulating target for treatment in patients with cancer, providing a generalizable tool to favorably influence the antitumor properties of circulating T cells, B cells, and intratumoral regulatory T cells. Cancer Res; 73(24); 7189–98. ©2013 AACR.

Abstract Human blood dendritic cells (DCs) expressing BDCA3 (CD141) have been characterized and described by several groups to represent the human counterpart of the mouse cross-presenting CD8α+ DC. Fully functional cross-presenting DCs are of utmost importance for the induction of tumor-antigen specific CD8 T-cell responses. In the current study, we set out to interrogate BDCA3+ DC within human tumor-draining lymph nodes (LNs) from melanoma and breast cancer patients. For this purpose a 12-color polychromatic flow panel for human DC was developed. CD11c+BDCA3+ cells were found to be of immature phenotype (low in CD80, CD86 and CD83) upon isolation. When comparing a group of 9 tumor-negative LNs with 4 tumor-positive LNs of BrCa patients, the percentage of CD11c+BDCA3+ cells was significantly higher (p<0.03) in the specimen containing tumor metastasis. Moreover, when comparing the activation status of BDCA3+ cells in LNs from advanced melanoma patients that did or did not grossly display evidence of metastatic disease, we observed lower expression of the DC maturation marker CD83 in the grossly positive LNs, suggesting that this population of DC might be affected by active tumor-induced suppression. In ongoing studies we are sorting these BDCA3+ DC to determine their cross-presenting abilities and to determine whether a (tumor-induced) immature phenotype is also reflected in the functional capabilities of these cells.

The cancer-testis antigen NY-ESO-1 is a potential target antigen for immune therapy expressed in a subset of patients with multiple myeloma. We generated chimeric antigen receptors (CARs) recognizing the immunodominant NY-ESO-1 peptide 157–165 in the context of HLA-A*02:01 to re-direct autologous CD8+ T cells towards NY-ESO-1+ myeloma cells. These re-directed T cells specifically lysed NY-ESO-1157–165/HLA-A*02:01-positive cells and secreted IFNγ. A total of 40% of CCR7− re-directed T cells had an effector memory phenotype and 5% a central memory phenotype. Based on CCR7 cell sorting, effector and memory CAR-positive T cells were separated and CCR7+ memory cells demonstrated after antigen-specific re-stimulation downregulation of CCR7 as sign of differentiation towards effector cells accompanied by an increased secretion of memory signature cytokines such as IL-2. To evaluate NY-ESO-1 as potential target antigen, we screened 78 bone marrow biopsies of multiple myeloma patients where NY-ESO-1 protein was found to be expressed by immunohistochemistry in 9.7% of samples. Adoptively transferred NY-ESO-1-specific re-directed T cells protected mice against challenge with endogenously NY-ESO-1-positive myeloma cells in a xenograft model. In conclusion, re-directed effector- and central memory T cells specifically recognized NY-ESO-1157–165/ HLA-A*02:01-positive cells resulting in antigen-specific functionality in vitro and in vivo.

AbstractPurpose: We previously reported that autophagy in tumor cells plays a critical role in cross-presentation of tumor antigens and that autophagosomes are efficient antigen carriers for cross-priming of tumor-reactive CD8+ T cells. Here, we sought to characterize further the autophagosome-enriched vaccine named DRibble (DRiPs-containing blebs), which is derived from tumor cells after inhibition of protein degradation, and to provide insights into the mechanisms responsible for their efficacy as a novel cancer immunotherapy.Experimental Design: DRibbles were characterized by Western blot and light or transmission electron microscopy. The efficiency of cross-presentation mediated by DRibbles was first compared with that of whole-tumor cells and pure proteins. The mechanisms of antigen cross-presentation by DRibbles were analyzed, and the antitumor efficacy of the DRibble vaccine was tested in 3LL Lewis lung tumors and B16F10 melanoma.Results: The DRibbles sequester both long-lived and short-lived proteins, including defective ribosomal products (DRiP), and damage-associated molecular pattern molecules exemplified by HSP90, HSP94, calreticulin, and HMGB1. DRibbles express ligands for CLEC9A, a newly described C-type lectin receptor expressed by a subset of conventional and plasmacytoid dendritic cells (DC), and cross-presentation was partially CLEC9A dependent. Furthermore, this autophagy-assisted antigen cross-presentation pathway involved both caveolae- and clathrin-mediated endocytosis and endoplasmic reticulum–associated degradation machinery. It depends on proteasome and TAP1, but not lysosome functions of antigen-presenting cells. Importantly, DCs loaded with autophagosome-enriched DRibbles can eradicate 3LL Lewis lung tumors and significantly delay the growth of B16F10 melanoma.Conclusions: These data documented the unique characteristics and potent antitumor efficacy of the autophagosome-based DRibble vaccine. The efficacy of DRibble cancer vaccine will be further tested in clinical trials. Clin Cancer Res; 17(22); 7047–57. ©2011 AACR.