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\u27The Cambridge Companion to Dante’s Commedia. \u27 Zygmunt G. Barański and Simon Gilson, eds. Cambridge: Cambridge University Press, 2019.
Get PDFMary Alexandra Watt. \u27Dante’s Golden Legend. Auto-hagiography in the Divine Comedy.\u27 Macon, Georgia: Mercer University Press, 2021.
Get PDFPenn Library\u27s LJS 455 - Fawāʼid al-ḥabīb. Zinjār al-ḥukamāʼ (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1196/thumbnail.jp
The MHCII-Restricted Presentation of HIV-1 Antigens by CD4+ T Cells
No full textHIV-1-specific CD4+ T cells (TCD4+) play a critical role in controlling HIV-1 infection. Robust HIV-1-specific TCD4+ responses are associated with decreased viral load and increased antibody neutralization breadth, and thus understanding the processes that lead to successful HIV-1-specific TCD4+ activation is crucial. According to convention, TCD4+ activation is mediated by professional antigen-presenting cells (APCs), such as dendritic cells (DCs), macrophages, and B cells that: 1) take up extracellular antigen, such as whole virions, 2) proteolyze internalized virions into smaller peptides within the endocytic compartment, 3) load resulting peptides onto major histocompatibility complex class II (MHCII) molecules within the late endosome, and 4) transport the peptide: MHCII complexes to the plasma membrane, where they can provide activating signal to antigen-specific TCD4+. However, several alternative processing modes have been described. Endogenous processing, one of these alternatives, occurs when the APC becomes productively infected and nascent viral proteins are used as processing substrates for presentation on MHCII. However, the relative contributions of these pathways to the HIV-1-specific TCD4+ response are unknown. In addition, the cell types capable of MHCII-restricted presentation may be more complex than originally appreciated. Notably, TCD4+, which express MHCII upon activation and are HIV-1 host cells, might act as APCs during an HIV-1 infection. In this study, I used a lentiviral transduction system to achieve HIV-1-specificity in primary human TCD4+. I then assessed the ability of primary monocyte-derived DCs and activated TCD4+ to present HIV-1-derived antigen. I show that activated TCD4+ are highly effective at MHCII-restricted presentation of an immunodominant HIV-1-derived epitope due to the tropism of HIV-1 for TCD4+ and the efficiency of endogenous processing. Additionally, and unexpectedly, I found that MHCII-restricted TCD4+-to-TCD4+ presentation facilitates transfer of virus to HIV-1-specific TCD4+, providing both a potential explanation for the rapid spread of the virus to HIV-1-specific TCD4+ in vivo and a novel mechanism for compromising the host response
Coregulation of Gene Expression by mRNA and tRNA Modifications
No full textRNA modifications are concurrently found on nearly all RNA species and can dramatically alter the properties and expression of RNA. Modifications on different RNA species can affect gene expression through several mechanisms such as localization, stability, and translation efficiency. There has been a great effort by the field to understand the functional impact of individual modifications in isolated RNAs, but the interplay of both mRNA and tRNA modifications and their respective enzymes is currently understudied. Here, we investigate how the N6-methyladenosine (m6A) mRNA modification can regulate gene expression through two distinct mechanisms: (1) a direct interaction with mcm5s2U34-tRNA to modulate translation and (2) modulation of mRNA stability and translation via the interaction between the m6A demethylase FTO and the tRNA methyltransferase TRMT10A. To investigate the direct interaction, we analyzed publicly available datasets and classified a pool of genes whose coding regions are enriched in both m6A as well as codons specifically dependent on mcm5s2U34-modified tRNAs. Further analysis of ribosome profiling data indicates that this group of genes exhibit basally low association with ribosomes. Using specially designed reporters, we show that loss of modifications to both the mRNA codon and tRNA anticodon has the greatest negative effect on translation. Towards our investigation of enzymatic m6A modulation, we observe that loss of TRMT10A induces a reduction in m1G-tRNA, but surprisingly also induces increased m6A-mRNA. Following this, we show that the physical interaction of these two distinct enzymes is critical in maintaining proper transcriptomic m6A-mRNA, suggesting a new non-enzymatic secondary role of TRMT10A as a partner protein to facilitate FTO’s demethylation activity. Analysis of ribosome profiling and m6A-RIP-seq data reveals that most the activity of FTO-TRMT10A generally supports translation. Altogether, these results demonstrate two distinct mechanisms by which m6A-mRNA and tRNA-modifying enzymes can be controlled and leveraged by cells to regulate and coordinate post-transcriptional events
Neurobehavioral Mechanisms of Motivation and Its Impairment
No full textMotivation, the drive to perform goal-directed actions, is necessary for healthy human functioning. Impaired motivation is a prominent symptom of neuropsychiatric disorders including schizophrenia (SZ) and depression and is not improved by currently-available therapeutics. Motivation relies on a conserved neural circuit comprised primarily of the ventral striatum (VS), ventromedial prefrontal cortex, and dorsal anterior cingulate cortex. VS hypofunction has also been linked to negative symptoms of SZ. Thus, it is essential to study motivation in order to translate knowledge of its neurobehavioral mechanisms to therapeutic advances. The overarching goals of this dissertation were to characterize neural activation patterns and behavioral decision-making processes related to motivation across different contexts and to investigate how individual variation in motivation impairment and clinical symptomatology relates to these neurobehavioral processes. First, we investigated effort discounting in healthy individuals and patients with SZ. We found that VS activated to reward and de-activated to effort costs, integrating to encode subjective value. VS activation during task decisions related negatively to dimensional clinical amotivation across patients and controls. Next, we investigated the role of VS in encoding self-generated correctness responses during intrinsically and extrinsically motivated performance of a memory task in healthy adolescents and those at risk for psychosis. We found that VS encoded parametric subjective confidence during memory task choices and parametric prediction error during performance feedback, providing evidence for VS engagement related to intrinsic expected value. VS activation during choice related positively to dimensional self-reported trait intrinsic motivation across both study groups. Third, we employed a novel effort discounting behavioral task to compare motivated decision-making in social and non-social contexts. We found that motivated behavior in social contexts related to both global and social-specific motivation and related to approach and avoidance motivation tendencies. Together, this dissertation work sheds light on how expected value is computed under different motivational contexts—monetary, intrinsic, and social—and how each of these processes relies on global vs specific neurobehavioral mechanisms. Our findings on the effects of individual differences in these motivation processes will enhance future abilities to detect novel treatment targets for impaired motivation
A Genetic Strategy to Improve VSV Vectored Vaccines against Emerging Bandaviruses
No full textSevere fever with thrombocytopenia syndrome virus (SFTSV) is an emerging bandavirus (order Bunyavirales) that causes high case fatality ratios in humans and cats. Since its discovery in 2009 in China, annual case counts have steadily risen across its endemic range. In addition, one prominent SFTSV tick vector, Haemaphysalis longicornis, has become an invasive species throughout the world. Though SFTSV infections have thus far been limited to Southeast Asia, the genetically similar heartland bandavirus (HRTV) was discovered in the United States in 2011. Despite the significant public health threat posed by these viruses, no vaccines currently exist. To address this need, we evaluated the safety and efficacy of a recombinant vesicular stomatitis virus (rVSV) vaccine encoding the SFTSV glycoproteins (rVSV-SFTSV) in an interferon-incompetent mouse model of lethal SFTSV infection. A single dose rVSV-SFTSV was well-tolerated and cross-protected mice from lethal SFTSV and mouse-adapted HRTV challenge. However, rVSV-SFTSV was highly attenuated in cell culture, likely due to a mismatch between the intracellular retention of SFTSV glycoproteins GN/GC and the cell surface assembly sites of VSV. Sequence homology identified a putative coatomer complex I (COPI) binding motif in the cytosolic tail of GC. Genetic disruption of this motif redistributed chimeric fluorescent reporter proteins and full-length GN/GC to the cell surface and correlated with more rapid recovery of infectious VSV pseudotypes. The same change in HRTV GN/GC similarly increased yields of infectious VSV pseudotypes. This work demonstrates rVSV-SFTSV is a safe vaccine candidate whose immunogenicity may be enhanced by genetic alteration of retention signals encoded within the SFTSV glycoproteins. Future rVSVs encoding bandavirus glycoproteins may also be improved by genetic ablation of the putative COPI binding site in the GC
The Biology of CD8 T Cell Exhaustion: Lessons from in vitro Models
No full textIdentifying novel molecular mechanisms of exhausted CD8 T cells (Tex) is a key goal of improving immunotherapy of cancer and other diseases. However, high-throughput interrogation of in vivo Tex can be costly and inefficient. In vitro models of Tex are easily customizable and quickly generate high cellular yield, offering an opportunity to perform CRISPR screening and other high-throughput assays. We established an in vitro model of chronic stimulation and benchmarked key phenotypic, functional, transcriptional, and epigenetic features against bona fide in vivo Tex. We leveraged this model of in vitro chronic stimulation in combination with pooled CRISPR screening to uncover transcriptional regulators of T cell exhaustion. This approach identified several transcription factors, including Bhlhe40. In vitro and in vivo validation defined a role for Bhlhe40 in regulating a central differentiation checkpoint between progenitor and intermediate subsets of Tex. By developing and benchmarking an in vitro model of Tex, we demonstrate the utility of mechanistically annotated in vitro models of Tex, in combination with high-throughput approaches, as a discovery pipeline to uncover novel Tex biology
Depletion-Induced “Magnetic” Phenomena in Quasi-Two-Dimensional Colloidal Suspensions
No full textThis thesis investigates the influence of depletion-driven attractive interactions in quasi-two-dimensional buckled colloidal monolayers on a triangular lattice. Without depletion, such that the interparticle interactions are hard-sphere-like, this experimental system is known to exhibit behaviors akin to a geometrically frustrated Ising antiferromagnet. The present research explores the effects that arise when a short-range attractive interaction (depletion attraction) between particles is introduced. We demonstrate that the added depletion attraction can influence both the magnitude and the sign of the Ising spin coupling constant. As a result, the nearest neighbor Ising spin interactions can be characterized as antiferromagnetic, paramagnetic, or ferromagnetic. We compute the effective Ising nearest-neighbor coupling (J/kBT) using a simple theoretical model; the model shows that a competition between entropic effects can modify the sign of the coupling constant from negative to positive and passing through zero. In experiments, the depletion interactions are induced by surfactant micelles comprised of hexaethylene glycol monododecyl ether (C12E6); these rod-like micelles change length with increasing temperature and offer means to tune the depletion attraction in-situ by utilizing temperature-tunable shape anisotropy. The experiments demonstrate the crossover behavior from Ising antiferromagnetic to paramagnetic in the buckled colloidal suspension as a function of depletion attraction. Additionally, spin-flip temporal autocorrelation functions are measured. The correlation functions exhibit both exponential and glassy dynamics. The glassy dynamics are driven by different underlying mechanisms and are observed in the negative and positive coupling-constant regimes. In total, this thesis introduces novel colloidal matter with complex dynamics and magnetic features that are rarely observed in traditional atomic systems