Induction of Immune Response Against Metastatic Tumors via Vaccination of Mannan-BAM, TLR Ligands and Anti-CD40 Antibody (MBTA)

Emerging evidence is demonstrating the extent of T-cell infiltration within the tumor microenvironment has favorable prognostic and therapeutic implications. Hence, immunotherapeutic strategies that augment the T-cell signature of tumors hold promising therapeutic potential. Recently, immunotherapy based on intratumoral injection of mannan-BAM, toll-like receptor ligands and anti-CD40 antibody (MBTA) demonstrated promising potential to modulate the immune phenotype of injected tumors. The strategy promotes the phagocytosis of tumor cells to facilitate the recognition of tumor antigens and induce a tumor-specific adaptive immune response. Using a syngeneic colon carcinoma model, we demonstrate MBTA's potential to augment CD8⁺ T-cell tumor infiltrate when administered intratumorally or subcutaneously as part of a whole tumor cell vaccine. Both immunotherapeutic strategies proved effective at controlling tumor growth, prolonged survival and induced immunological memory against the parental cell line. Collectively, our investigation demonstrates MBTA's potential to trigger a potent anti-tumor immune response.

Overexpression of CD6 and PD-1 Identifies Dysfunctional CD8+ T-Cells During Chronic SIV Infection of Rhesus Macaques

Effective CD8⁺ T-cell responses play an important role in determining the course of SIV/HIV viral infection. Here we identified a unique population of dysfunctional CD8⁺ T-cells in lymphoid tissues and bronchoalveolar lavage (BAL) of rhesus macaques with chronic SIV infection characterized by co-expression of CD6 and PD-1. The frequency of CD6 and PD-1 co-expressing CD8⁺ T-cells was significantly increased in lymphoid tissues and BAL during chronic SIV infection compared to pre-infection levels. These CD6⁺PD-1⁺CD8⁺ T-cells displayed impaired proliferation, cytokine secretion and cytotoxicity compared to their CD6^-PD-1⁺CD8⁺ T cell counterparts. The frequency of CD8⁺PD-1⁺ and CD8⁺CD6^-PD-1⁺ T-cells in the lymph node and bone marrow did not correlate with SIV viral load, whereas the frequency of CD8⁺CD6⁺PD-1⁺ T-cells positively correlated with SIV viral load in these tissues highlighting the contribution of CD6 to disease progression. CD6⁺PD-1⁺CD8⁺ T-cells expressed elevated levels of SHP2 phosphatase compared to CD6^-PD-1⁺CD8⁺ T-cells providing a potential mechanism by which CD6 may induce T-cell dysfunction during chronic SIV infection. Combined targeting of CD6 and PD-1 effectively revived the CD8⁺ T-cell proliferative response in vitro suggesting a strategy for potential therapeutic benefit.

TMOD-32. GL261 LUCIFERASE-EXPRESSING CELLS ELICIT AN ANTI-TUMOR IMMUNE RESPONSE: AN EVALUATION OF MURINE GLIOMA MODELS

Preclinical models that reliably recapitulate the immunosuppressive properties of human gliomas are essential to assess immune-based therapies. Intracranially injected GL261 cells are widely used as an immunocompetent animal model of glioma, but it is common practice to transfect these with luciferase to facilitate tumor monitoring during treatment. Our group has previously shown that the luciferase-expressing GL261 Red-FLuc cells create an inflammatory response when implanted intracranially. Now, we additionally explore the inflammatory response of GL261-Luc2 cells and demonstrate a similar host immune response occurs with this model as well. In our in vivo evaluation, C57BL/6 mice underwent stereotaxic, intracranial implantation with GL261, GL261 Red-FLuc or GL261-Luc2 cells at doses of 5x104cells/5mL or 3x105cells/5uL.MRIs were performed to monitor relative tumor growth. To assess intrinsic differences between cell lines, in vitro cytokine profiles were evaluated by proteome microarray. Kaplan-Meier survival analyses demonstrated median survival for mice implanted with GL261 cells at 5x104cells was 18 to 21 days. The GL261-Red FLuc implanted mice cells did not reach median survival at either tumor dose with greater than 60% of mice termed long-term survivors. Finally, mice injected with GL261-Luc2 cells at 3x105cells reached median survival at 23 days, but median survival was significantly prolonged for mice implanted with GL261-Luc2 at a dose of 5x104cells (37 days, with 40% becoming long-term survivors) compared to GL261 implanted mice. MRIs reveal differences in tumor growth that correspond with the differences in median survival between groups. In addition, proteomic analyses revealed significantly elevated inflammatory cytokines such as IFN-gamma, IL-7 and TNF-alpha in the supernatants of the GL261 Red-FLuc cells and GL261-Luc2 cells. Further immune characterization is ongoing. Our data suggests that GL261 Red-FLuc and GL261-Luc2 murine models elicit an anti-tumor immune response by increasing pro-inflammatory modulators which stimulate the tumoricidal function of immune cells in the tumor microenvironment.

TMIC-28. LONG NON-CODING RNA EXPRESSION DIFFERS BETWEEN GLIOBLASTOMA PATIENT IMMUNE CELLS AND HEALTHY VOLUNTEERS

To improve glioblastoma treatment, improved characterization of the tumor’s immune microenvironment is critical. Aberrant long non-coding RNA (LncRNA) expression has been implicated in the pathogenesis of many cancers, including glioblastoma. Other studies have discovered long non-coding RNAs which regulate immunity. However, lncRNA expression has not been systematically investigated glioblastoma patient immune cells. We aimed to investigate the differential expression of LncRNA and mRNs in the T lymphocytes and monocytes of glioblastoma patients when compared to healthy controls in an unbiased fashion. CD3 and CD14 cells were sorted from PBMC samples from 3 newly diagnosed glioblastoma patients and 3 normal donors, and RNA was extracted from them. These RNA samples were run on the Arraystar Human LncRNA microarray. We found 309 LncRNAs differentially expressed in glioblastoma patient T cells, and 316 in patient monocytes (fold change >2 or £0.5, P£0.05). A preliminary review of this data has revealed upregulation of lncRNAs that have previously been reported to play a role in tumorigenesis, such as MIF12-AS1, VIM-AS1, and WEE2-AS1. Additionally, lncRNAs such as CCDC26 and Hoxa10 that have been implicated in immune cell differentiation and hyperactivity also show differential expression between the two groups. We also found differential expression of 203 mRNA in T cells and 467 in monocytes (fold change ³2 or £0.5, P£0.05). An analysis based on the Kyoto Encyclopedia of Genes and Genomes identified 42 biological pathways that have enrichment of these differentially expressed mRNAs (P£0.05), including the RIG-I-like receptor pathway and toll-like receptor pathway, both implicated in innate immunity in T-cells. This array data will form the template for future single-cell RNA sequencing of tumor-infiltrating immune cells; peripheral immune cells from glioblastoma patients; and immune cells from non-tumorous brain (epilepsy tissue) and blood samples to investigate these differences in greater detail.

A Pathogenic Role for Splenic B1 Cells in SIV Disease Progression in Rhesus Macaques

B1 cells spontaneously produce protective natural antibodies which provide the first line of defense against a variety of pathogens. Although these natural antibodies share similar autoreactive features with several HIV-1 broadly neutralizing antibodies, the role of B1 cells in HIV/SIV disease progression is unknown. We report the presence of human-like B1 cells in rhesus macaques. During chronic SIV infection, we found that the frequency of splenic CD11b⁺ B1 cells positively correlated with plasma SIV viral load and exhausted T cells. Mechanistically, we discovered that splenic CD11b⁺ B1 cells express PD-L2 and IL-10, and were able to induce PD-1 upregulation on CD4⁺ T cells in vitro. These findings suggest that splenic CD11b⁺ B1 cells may contribute to the regulation of SIV plasma viral load by enhancing T cell exhaustion. Therefore, understanding the mechanisms that govern their function in rhesus macaques may lead to novel therapeutic strategies for impeding HIV/SIV disease progression.

Current Options and Future Directions in Immune Therapy for Glioblastoma

Glioblastoma is in need of innovative treatment approaches. Immune therapy for cancer refers to the use of the body's immune system to target malignant cells in the body. Such immune therapeutics have recently been very successful in treating a diverse group of cancerous lesions. As a result, many new immune therapies have gained Food and Drug Administration approval for the treatment of cancer, and there has been an explosion in the study of immune therapeutics for cancer treatment over the past few years. However, the immune suppression of glioblastoma and the unique immune microenvironment of the brain make immune therapeutics more challenging to apply to the brain than to other systemic cancers. Here, we discuss the existing barriers to successful immune therapy for glioblastoma and the ongoing development of immune therapeutics. We will discuss the discovery and classification of immune suppressive factors in the glioblastoma microenvironment; the development of vaccine-based therapies; the use of convection-enhanced delivery to introduce tumoricidal viruses into the tumor microenvironment, leading to secondary immune responses; the emerging use of adoptive cell therapy in the treatment of glioblastoma; and future frontiers, such as the use of cerebral microdialysis for immune monitoring and the use of sequencing to develop patient-specific therapeutics. Armed with a better understanding of the challenges inherent in immune therapy for glioblastoma, we may soon see more successes in immune-based clinical trials for this deadly disease.