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IgA MAb blocks SARS-CoV-2 Spike-ACE2 interaction providing mucosal immunity [preprint]COVID-19 caused by SARS-CoV-2 has become a global pandemic requiring the development of interventions for the prevention or treatment to curtail mortality and morbidity. No vaccine to boost mucosal immunity or as a therapeutic has yet been developed to SARS-CoV-2. In this study we discover and characterize a cross-reactive human IgA monoclonal antibody, MAb362. MAb362 binds to both SARS-CoV and SARS-CoV-2 spike proteins and competitively blocks hACE2 receptor binding, by completely overlapping the hACE2 structural binding epitope. Furthermore, MAb362 IgA neutralizes both pseudotyped SARS-CoV and SARS-CoV-2 in human epithelial cells expressing hACE2. SARS-CoV-2 specific IgA antibodies, such as MAb362, may provide effective immunity against SARS-CoV-2 by inducing mucosal immunity within the respiratory system, a potentially critical feature of an effective vaccine.
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MYC and E1A Oncogenes Alter the Response of PC12 Cells to Nerve Growth Factor and Block Differentiation: A ThesisPC12 rat pheochromocytoma cells respond to nerve growth factor (NGF) by neuronal differentiation and partial growth arrest. Mouse c-myc and adenovirus E1A genes were introduced into PC12 cells to study the influence of these nuclear oncogenes on neuronal differentiation. Expression of myc and E1A blocked morphological differentiation and caused NGF to stimulate rather than inhibit cell proliferation. NGF binding to cell surface receptors, activation of ribosomal S6 kinase, and ornithine decarboxylase induction were similar in myc and E1A expressing clones compared with wild-type PC12 cells, suggesting that changes in the cellular response to NGF were at a post-receptor level. The ability of myc and E1A expression to block the transcription-dependent induction of microtubule associated proteins by NGF further suggested that these genes may inhibit differentiation by interfering with NGP's ability to regulate transcription. These results illustrate that NGF can promote either growth or differentiation of PC12 cells, and that myc or E1A alter the phenotypic responses to growth factors.
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Clinically Relevant Doses of Chemotherapy Drugs Selectively and Reversibly Block Glioblastoma Neurosphere Proliferation in vitro: A DissertationMy thesis research began with a project in which we were trying to determine the function of embryonic stem cell (ESC)-specific miRNAs. Using luciferase constructs containing miRNA binding sites, luciferase expression was inhibited by endogenous miRNAs in ESCs, and by exogenous miRNAs in HeLa cells. Inhibition of luciferase expression by miRNAs was inhibited in HeLa cells using 2’O-methyl-oligonucleotides. In ESCs, 2’O-methyl-oligonucleotides were only effective in partially inhibiting miR290 function. Partial inhibition of miR290 did not result in any obvious phenotypic changes in mESCs. Later studies using 2’O-methyl-oligonucleotides in ESCs were also unsuccessful. The function of ESC-specific miRNAs has since been studied by re-introducing miRNAs into Dicer -/- cells which cannot make miRNAs. These studies have shown that ESC-specific miRNAs are involved in de novo DNA methylation, self-renewal, and cell-cycle regulation. Newly diagnosed glioblastoma (GBM) patients rarely survive more than two years even after surgery, radiotherapy, and chemotherapy using temozolomide (TMZ) or 1,3-bis(2-chloroethy)-1-nitrosourea (BCNU). Eventual regrowth of the tumor indicates that some tumor cells are resistant to therapy. GBM neurosphere-initiating cells (NICs) are thought to be similar to tumor-initiating cells in vivo, and will form invasive tumors in mice, making neurosphere cultures a good model system for studying GBMs. To test whether GBM NICs were resistant to chemotherapy, we used a neurosphere formation assay to measure the number of proliferating NICs in the presence of TMZ or BCNU. The concentrations of chemotherapy drugs required to inhibit neurosphere formation were much less than those required to inhibit bulk cell proliferation or to induce cell death in our neurosphere cultures. For some cultures, there was a robust recovery of neurosphere formation after chemotherapy treatment which appeared to be DNA damage independent. Some of the cultures that showed significant recovery of neurosphere formation underwent reversible cell cycle arrest, possibly reducing chemotoxicity in these cultures. Collectively, these results indicate that GBM neurosphere cultures can regrow after being treated with clinically relevant doses of chemotherapy drugs. Chemotherapy-treated neurosphere cultures remained viable, and formed tumors when injected into mice. Our experiments show that these in vitro assays may be useful in predicting in vivo responses to chemotherapeutic agents.
