Matching Items (2)
Filtering by
- All Subjects: immunotherapy
- Creators: Mor, Tsafrir
- Member of: ASU Electronic Theses and Dissertations
Description
The growing field of immunotherapy has generated numerous promising diseasetreatment platforms in recent years. By utilizing the innate capabilities of the immune system, these treatments have provided a unique, simplistic approach to targeting and eliminating cancer. Among these, the bispecific T cell engager (BiTEÒ) model has demonstrated potential as a treatment capable of bringing immune cells into contact with cancer cells of interest and initiating perforin/granzyme-mediated cell death of the tumor. While standard BiTE platforms rely on targeting a tumor-specific receptor via its complementary antibody, no such universal receptor has been reported for glioblastoma (GBM), the most common and aggressive primary brain tumor which boasts a median survival of only 15 months. In addition to its dismal prognosis, GBM deploys several immune-evasion tactics that further complicate treatment and make targeted therapy difficult. However, it has been reported that chlorotoxin, a 36-amino acid peptide found in the venom of Leiurus quinquestriatus, binds specifically to glioma cells while not binding healthy tissue in humans. This specificity positions chlorotoxin as a prime candidate to act as a GBM-targeting moiety as one half of an immunotherapeutic treatment platform resembling the BiTE design which I describe here. Named ACDClx∆15, this fusion protein tethers a truncated chlorotoxin molecule to the variable region of a monoclonal antibody targeted to CD3ε on both CD8+ and CD4+ T cells and is theorized to bring T cells into contact with GBM in order to stimulate an artificial immune response against the tumor. Here I describe the design and production of ACDClx∆15 and test its ability to bind and activate T lymphocytes against murine GBM in vitro. ACDClx∆15 was shown to bind both GBM and T cells without binding healthy cells in vitro but did not demonstrate the ability to activate T cells in the presence of GBM.
ContributorsSchaefer, Braeden Scott (Author) / Mor, Tsafrir (Thesis advisor) / Mason, Hugh (Committee member) / Blattman, Joseph (Committee member) / Arizona State University (Publisher)
Created2021
Description
Glioblastoma (GBM) is a highly invasive and deadly late stage tumor that develops from abnormal astrocytes in the brain. With few improvements in treatment over many decades, median patient survival is only 15 months and the 5-year survival rate hovers at 6%. Numerous challenges are encountered in the development of treatments for GBM. The blood-brain barrier (BBB) serves as a primary obstacle due to its innate ability to prevent unwanted molecules, such as most chemotherapeutics, from entering the brain tissue and reaching malignant cells. The GBM cells themselves serve as a second obstacle, having a high level of genetic and phenotypic heterogeneity. This characteristic improves the probability of a population of cells to have resistance to treatment, which ensures the survival of the tumor. Here, the development and testing of two different modes of therapy for treating GBM is described. These therapeutics were enhanced by pathogenic peptides known to improve entry into brain tissue or to bind GBM cells to overcome the BBB and/or tumor cell heterogeneity. The first therapeutic utilizes a small peptide, RVG-29, derived from the rabies virus glycoprotein to improve brain-specific delivery of nanoparticles encapsulated with a small molecule payload. RVG-29-targeted nanoparticles were observed to reach the brain of healthy mice in higher concentrations 2 hours following intravenous injection compared to control particles. However, targeted camptothecin-loaded nanoparticles were not capable of producing significant treatment benefits compared to non-targeted particles in an orthotopic mouse model of GBM. Peptide degradation following injection was shown to be a likely cause for reduced treatment benefit. The second therapeutic utilizes chlorotoxin, a non-toxic 36-amino acid peptide found in the venom of the deathstalker scorpion, expressed as a fusion to antibody fragments to enhance T cell recognition and killing of GBM. This candidate biologic, known as anti-CD3/chlorotoxin (ACDClx) is expressed as an insoluble protein in Nicotiana benthamiana and Escherichia coli and must be purified in denaturing and reducing conditions prior to being refolded. ACDClx was shown to selectively activate T cells only in the presence of GBM cells, providing evidence that further preclinical development of ACDClx as a GBM immunotherapy is warranted.
ContributorsCook, Rebecca Leanne (Author) / Blattman, Joseph N (Thesis advisor) / Sirianni, Rachael W. (Thesis advisor) / Mor, Tsafrir (Committee member) / Anderson, Karen (Committee member) / Arizona State University (Publisher)
Created2019