Date of Award

2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Cell & Molecular Biology

First Advisor

Carl H. June

Second Advisor

Avery D. Posey

Abstract

Glioblastoma multiforme (GBM) is the most common and deadliest primary brain tumor. Immunotherapeutic approaches using chimeric antigen receptor (CAR) T cells have shown limited efficacy against GBM due to heterogeneous target antigen expression. We hypothesize that human cytomegalovirus (HCMV) can serve as a therapeutic target for GBM. HCMV can be detected in up to 90% of GBM tumor samples but not the surrounding normal brain tissue. The role of HCMV as a tumor-promoting virus is poorly understood but its presence in the tumor presents a novel approach to developing a therapy for GBM by re-directing T cells to target HCMV. We detected the presence of HCMV in GBM tumor samples via IHC and confirmed expression of HCMV gene UL55/glycoprotein B (gB) in 45% of primary GBM tumors. A CAR was generated and optimized to recognize the HCMV surface antigen gB. In vitro testing of the anti-gB CAR revealed activity against the U87 glioma cell line stably transduced to express gB and CMV-infected human foreskin fibroblasts (HFF) cells. In vivo, gB CARs were able to treat established GBM tumors in a xenograft mouse model. In vitro co-cultures of gB CAR T cells against the human GBM explant, D270, demonstrated tumor recognition and anti-tumor function against primary GBM. gB CAR T cells were able to control D270 tumor growth in vivo despite undetectable levels of antigen expression. Mice displaying stable disease showed improved persistence of engrafted human T cells and tumor infiltration. These results suggest that CAR T cells may be effective in recognizing extremely low abundance antigens, and taken together, the results of this study show the feasibility of using gB CAR T cells as a platform to target HCMV in GBM tumors to treat patients with GBM. Ultimately, the goal of this study is translate these findings into clinical trials.

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