Molecular Microbiology and Immunology electronic theses and dissertations (MU)
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The items in this collection are the theses and dissertations written by students of the Department of Molecular Microbiology and Immunology. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
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Item Manipulating T-cells and tumor antigens to improve endogenous and immunotherapy response against cancer.(University of Missouri--Columbia, 2025) Okpasuo, Onyekachi Juliet; Gil Pages, Diana[EMBARGOED UNTIL 12/01/2026] Despite many recent advancements in the development of treatments, cancer has remained the second leading cause of death globally for the past 75 years, accounting for over 9.7 million deaths annually. The inherent complexity and multifaceted nature of cancer pose significant challenges to advancing cancer treatment strategies. Cancer cells exploit various mechanisms to create a heterogeneous and immunosuppressive tumor microenvironment (TME) that evades immune surveillance, including the downregulation of tumor antigens and the production and recruitment of immunosuppressive immune cells, which further compromises the effectiveness of immunotherapeutic strategies. Cancer treatment strategies that boost both endogenous immune surveillance and empower the immune system to fight and target cancer cells are of significant need. This dissertation examines the potential of manipulating T-cell functionality and antigenic strength of tumor antigens to enhance the effectiveness of endogenous immune surveillance and therapy-mediated tumor immunity. We hypothesized that empowering immune cell functioning by controlled alteration of the T cell activation and tumor immunogenicity threshold would improve immune response against cancer cells. To this end, we tested anti-mouse and anti-human CD3ε Fab fragments strictly controlled for monovalence (Mono-Fabs) previously shown to co-potentiate T cell activation and effector function in response to T cell receptor (TCR)/antigen stimulation. We found that anti-CD3ε Fabs delivered anti-tumor effects in mice subcutaneously injected with the Yale University Mouse Melanoma (YUMM) tumor model. Using YUMM sub-lines, we dissected the impact of inherent tumor immunogenicity on the therapeutic effects of anti-CD3ε Mono-Fabs. We found anti-CD3ε Mono-Fabs enhanced anti-tumor effects of clinically proven anti-CTLA-4 and anti-PD-1 mAbs that function by immune checkpoint inhibition (ICI) in a manner dependent on tumor immunogenicity. Interestingly, anti-CD3ε Mono-Fabs displayed this beneficial effect without enhancing immunotoxicity associated with the use of ICI mAbs. Clinical translation of the novel anti-CD3ε Mono-Fabs may address the current therapeutic needs of various cancer patients who are considered ineligible to receive ICI-based therapies due to concerns about their immunotoxicity. While empowering immune cells with ICI mAbs has yielded improved clinical outcomes in a subset of patients, suboptimal responses prevail in most patients, primarily attributed to inadequate tumor immunogenicity and limited immune cell infiltration within the TME of certain cancer types, including “cold” tumors. We propose an immune-evoking strategy aimed at augmenting the immunogenicity of "cold" tumors to enhance both intra-tumoral immunogenicity and the efficacy of immune-targeted therapies. Comparing immunologically cold or hot variants of the melanoma model, YUMM showed enhanced endogenous tumor immunity with significant tumor rejection capability of hotter over colder melanoma variants. We observed that endogenous anti-tumor responses were above those achieved with combined T cell-based immunotherapies upon experimental comparison. In addition, we obtained empirical evidence that endogenous anti-tumor responses against more immunogenic tumor variants result in the generation of long-lasting memory T cells that can protect against less immunogenic but related variants. Although unexplored here, it is conceivable that extracting less immunogenic tumors and expanding their immunogenicity can be used as an immunizing agent to generate potent and long-lasting anti-tumor immune responses against original tumors that are less immunogenItem Functional characterization of human and chicken TLR3(University of Missouri--Columbia, 2025) Bartlett, Makenzie; Lange, MargaretToll-like receptor 3 (TLR3) is a critical component of the innate immune system, responsible for detecting viral double-stranded RNA (dsRNA) and initiating downstream signaling pathways, including activation of the transcription factor NF-κB. While TLR3 function has been extensively characterized in humans and other mammals, little is known about its activity in avian species such as chickens, which are highly susceptible to RNA viruses like avian influenza. Chickens rely heavily on innate immune responses due to their limited adaptive immunity, making TLR3 an important mediator of early antiviral defense. Notably, naturally occurring polymorphisms in chicken TLR3 (chTLR3) have been identified, but their functional significance remains unexplored. This thesis sets the foundation for investigating the impact of chTLR3 polymorphisms on receptor activity and downstream signaling. Using an NF-κB-driven GFP reporter cell line that lacks endogenous TLR3, we performed "addback" experiments in which wild-type or mutant chTLR3 was reintroduced. Cells were then stimulated with the synthetic dsRNA analog polyinosinic:polycytidylic acid (poly I:C) to assess NF-κB signaling. These experiments allow us to evaluate how individual chTLR3 variants influence dsRNA sensing and signaling capacity. Understanding species-specific differences in TLR3 signaling not only provides insight into fundamental immune mechanisms but also has implications for improving poultry health and controlling viral outbreaks. These findings serve as a basis for future studies aimed at defining how TLR3 variation contributes to disease susceptibility and innate immune regulation in birds.Item It's really quite POSH : the essential role of POSH in signal coordination and lymphocyte differentiation(University of Missouri--Columbia, 2025) Guldenpfennig, Caitlyn Elizabeth; Daniels, MarkUpon infection with a pathogen, lymphocytes must recognize antigen at the cellular membrane and induce cellular signaling pathways to produce an effective cellular response to that pathogen. Three integral signaling pathways activated upon antigen recognition are the c-JUN N-terminal kinase (JNK), the NF-κB, and the phosphoinositide 3-kinase (PI3K)/Akt pathways. While the impact of these pathways on cellular responses has been well established, the coordination of these pathways remains poorly understood. Plenty of SH3 Domains (POSH) functions as a scaffold protein for the JNK signaling pathway and has influence on both the NF-κB and PI3K/Akt pathways. Therefore, we hypothesized that POSH coordinates signals through these pathways to regulate cellular responses in lymphocytes. The work presented here is the first to establish the essential role of POSH in coordinating PI3K/Akt signaling in T cell differentiation and NF-κB signaling in B cell differentiation. Additionally, this work further establishes POSH as a therapeutic candidate for cancer therapy and demonstrates that aptamers could serve as an in vivo delivery system for small molecule drugs, such as a POSH inhibitor. Together, this work advances our understanding of signal coordination in lymphocytes and establishes a system for safer clinical applications.Item Francisella tularensis uses human neutrophils as trojan horses for infection and repolarization of macrophages(University of Missouri--Columbia, 2025) Escobar, Sydney Mae; Allen, Lee-Ann H.Francisella tularensis (Ft), the causative agent of tularemia, is a Gram-negative bacterium that infects neutrophils (polymorphonuclear leukocytes, PMNs) and macrophages. Previous studies by our group and others demonstrate that Ft inhibits the respiratory burst, escapes the phagosome, replicates in the cytosol, and significantly prolongs human neutrophil lifespan. Ft promotes the development of a unique metabolic landscape characterized by increased glucose uptake, glycogen storage, and glycolysis and requires P38 MAPK and PI3Kα to do so. We work to understand which p38 and PI3Kα pathways Ft utilizes to change PMN metabolism and apoptosis. Additionally, the fate of infected neutrophils with extended lifespans and their bacterial cargo are unknown. We demonstrate that Ft-infected neutrophils (iPMNs) interact more efficiently with primary human monocyte-derived macrophages (MDMs) than aged, control PMNs despite their viability and paucity of surface phosphatidylserine and identify an important role for serum and C1q in this process. Uptake by this mechanism supports bacterial growth in MDMs, indicating that iPMNs can act as Trojan horses to spread infection. iPMN uptake by MDMs elicits an atypical phenotype notable for downregulation of both pro- and anti-inflammatory polarization markers.Item Modular oligonucleotide technologies to target, sensitize, and treat mutant EGFR positive lung adenocarcinoma(University of Missouri--Columbia, 2025) Thomas, Brian Jacob; Burke, Donald[EMBARGOED UNTIL 05/01/2026] Despite various public health initiatives, lung cancer remains a leading cause of death worldwide and is expected to account for ~20% of all cancer related deaths in the United States in 2025. Contributing significantly to these statistics is lung adenocarcinoma (LUAD), one of the most prevalent forms of Non-Small Cell Lung Cancer (NSCLC). Unlike other forms of lung cancer, LUAD is not typically associated with exposure to carcinogens, but is instead often caused by acquired somatic mutations or amplifications in oncogenes and/or tumor suppressors. One such oncogene is the receptor tyrosine kinase, Epidermal Growth Factor Receptor (EGFR), for which gene amplifications or mutations in the tyrosine kinase domain induce survival mechanisms and/or sustained proliferative signaling. Fortunately, EGFR targeted therapies such as tyrosine kinase inhibitors (TKIs) have revolutionized outcomes for patients with mutant EGFR positive LUAD; however, therapeutic resistance and progressive disease are inevitable and typically occur 12-18 months after beginning these treatments. Because second- and third-line therapeutics are often ineffective or toxic, there is an unmet need for alternative or adjuvant methods to treat such cancers. The work described in this dissertation focuses on the application of oligonucleotide technologies to address this unmet need, with a major emphasis on aptamer technology. We take advantage of the modular properties of oligonucleotides to develop multivalent, aptamer-based, cell surface targeting reagents and explore how reagent structure impacts its biodistribution and its ability to target the tumor. Using fluorescent based imaging techniques and a newly developed multiplex screening method, termed Barcoded Aptamer Technology (BApT), we show that bispecific reagents do not always outperform monospecific reagents, and we highlight the poor predictability of in vitro binding assays. In addition, we show how both aptamer and siRNA technologies can be utilized to sensitize or treat a subset of mutant EGFR positive LUADs, either directly or indirectly by modulating immune effector cells. This includes targeting DUSP11, a newly identified innate immune checkpoint (iIC) in LUAD. As aptamers have had limited success translating into the clinic, the discussions prioritize addressing pharmacokinetic (PK) and delivery method barriers for the development of clinically useful reagents.