Matching Items (171)
Description
The concept of vaccination dates back further than Edward Jenner's first vaccine using cowpox pustules to confer immunity against smallpox in 1796. Nevertheless, it was Jenner's success that gave vaccines their name and made vaccinia virus (VACV) of particular interest. More than 200 years later there is still the need to understand vaccination from vaccine design to prediction of vaccine efficacy using mathematical models. Post-exposure vaccination with VACV has been suggested to be effective if administered within four days of smallpox exposure although this has not been definitively studied in humans. The first and second chapters analyze post-exposure prophylaxis of VACV in an animal model using v50ΔB13RMγ, a recombinant VACV expressing murine interferon gamma (IFN-γ) also known as type II IFN. While untreated animals infected with wild type VACV die by 10 days post-infection (dpi), animals treated with v50ΔB13RMγ 1 dpi had decreased morbidity and 100% survival. Despite these differences, the viral load was similar in both groups suggesting that v50ΔB13RMγ acts as an immunoregulator rather than as an antiviral. One of the main characteristics of VACV is its resistance to type I IFN, an effect primarily mediated by the E3L protein, which has a Z-DNA binding domain and a double-stranded RNA (dsRNA) binding domain. In the third chapter a VACV that independently expresses both domains of E3L was engineered and compared to wild type in cells in culture. The dual expression virus was unable to replicate in the JC murine cell line where both domains are needed together for replication. Moreover, phosphorylation of the dsRNA dependent protein kinase (PKR) was observed at late times post-infection which indicates that both domains need to be linked together in order to block the IFN response. Because smallpox has already been eradicated, the utility of mathematical modeling as a tool for predicting disease spread and vaccine efficacy was explored in the last chapter using dengue as a disease model. Current modeling approaches were reviewed and the 2000-2001 dengue outbreak in a Peruvian region was analyzed. This last section highlights the importance of interdisciplinary collaboration and how it benefits research on infectious diseases.
ContributorsHolechek, Susan A (Author) / Jacobs, Bertram L (Thesis advisor) / Castillo-Chavez, Carlos (Committee member) / Frasch, Wayne (Committee member) / Hogue, Brenda (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2011
Description
HIV/AIDS is the sixth leading cause of death worldwide and the leading cause of death among women of reproductive age living in low-income countries. Clinicians in industrialized nations monitor the efficacy of antiretroviral drugs and HIV disease progression with the HIV-1 viral load assay, which measures the copy number of HIV-1 RNA in blood. However, viral load assays are not widely available in sub-Saharan Africa and cost between 50-$139 USD per test on average where available. To address this problem, a mixed-methods approach was undertaken to design a novel and inexpensive viral load diagnostic for HIV-1 and to evaluate barriers to its adoption in a developing country. The assay was produced based on loop-mediated isothermal amplification (LAMP). Blood samples from twenty-one individuals were spiked with varying concentrations of HIV-1 RNA to evaluate the sensitivity and specificity of LAMP. Under isothermal conditions, LAMP was performed with an initial reverse-transcription step (RT-LAMP) and primers designed for HIV-1 subtype C. Each reaction generated up to a few billion copies of target DNA within an hour. Presence of target was detected through naked-eye observation of a fluorescent indicator and verified by DNA gel electrophoresis and real-time fluorescence. The assay successfully detected the presence of HIV in samples with a broad range of HIV RNA concentration, from over 120,000 copies/reaction to 120 copies/reaction. In order to better understand barriers to adoption of LAMP in developing countries, a feasibility study was undertaken in Tanzania, a low-income country facing significant problems in healthcare. Medical professionals in Northern Tanzania were surveyed for feedback regarding perspectives of current HIV assays, patient treatment strategies, availability of treatment, treatment priorities, HIV transmission, and barriers to adoption of the HIV-1 LAMP assay. The majority of medical providers surveyed indicated that the proposed LAMP assay is too expensive for their patient populations. Significant gender differences were observed in response to some survey questions. Female medical providers were more likely to cite stigma as a source problem of the HIV epidemic than male medical providers while males were more likely to cite lack of education as a source problem than female medical providers.
ContributorsSalamone, Damien Thomas (Author) / Jacobs, Bertram L (Thesis advisor) / Marsiglia, Flavio (Committee member) / Stout, Valerie (Committee member) / Johnson, Crista (Committee member) / Arizona State University (Publisher)
Created2011
Description
Rhodoferax antarcticus strain ANT.BR, a purple nonsulfur bacterium isolated from a microbial mat in Ross Island, Antarctica, is the first described anoxygenic phototrophic bacterium that is adapted to cold habitats and is the first beta-proteobacterium to undergo complete genome sequencing. R. antarcticus has unique absorption spectra and there are no obvious intracytoplasmic membranes in cells grown phototrophically, even under low light intensity. Analysis of the finished genome sequence reveals a single chromosome (3,809,266 bp) and a large plasmid (198,615 bp) that together harbor 4,262 putative genes. The genome contains two types of Rubiscos, Form IAq and Form II, which are known to exhibit quite different kinetic properties in other bacteria. The presence of multiple Rubisco forms could give R. antarcticus high metabolic flexibility in diverse environments. Annotation of the complete genome sequence along with previous experimental results predict the presence of structural genes for three types of light-harvesting (LH) complexes, LH I (B875), LH II (B800/850), and LH III (B800/820). There is evidence that expression of genes for the LH II complex might be inhibited when R. antarcticus is under low temperature and/or low light intensity. These interesting condition-dependent light-harvesting apparatuses and the control of their expression are very valuable for the further understanding of photosynthesis in cold environments. Finally, R. antarcticus exhibits a highly motile lifestyle. The genome content and organization of all putative polar flagella genes are characterized and discussed.
ContributorsZhao, Tingting, M.S (Author) / Touchman, Jeffrey (Thesis advisor) / Rosenberg, Michael (Committee member) / Redding, Kevin (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2011
Description
The oceans play an essential role in global biogeochemical cycles and in regulating climate. The biological carbon pump, the photosynthetic fixation of carbon dioxide by phytoplankton and subsequent sequestration of organic carbon into deep water, combined with the physical carbon pump, make the oceans the only long-term net sink for anthropogenic carbon dioxide. A full understanding of the workings of the biological carbon pump requires a knowledge of the role of different taxonomic groups of phytoplankton (protists and cyanobacteria) to organic carbon export. However, this has been difficult due to the degraded nature of particles sinking into particle traps, the main tools employed by oceanographers to collect sinking particulate matter in the ocean. In this study DNA-based molecular methods, including denaturing gradient gel electrophoresis, cloning and sequencing, and taxon-specific quantitative PCR, allowed for the first time for the identification of which protists and cyanobacteria contributed to the material collected by the traps in relation to their presence in the euphotic zone. I conducted this study at two time-series stations in the subtropical North Atlantic Ocean, one north of the Canary Islands, and one located south of Bermuda. The Bermuda study allowed me to investigate seasonal and interannual changes in the contribution of the plankton community to particle flux. I could also show that small unarmored taxa, including representatives of prasinophytes and cyanobacteria, constituted a significant fraction of sequences recovered from sediment trap material. Prasinophyte sequences alone could account for up to 13% of the clone library sequences of trap material during bloom periods. These observations contradict a long-standing paradigm in biological oceanography that only large taxa with mineral shells are capable of sinking while smaller, unarmored cells are recycled in the euphotic zone through the microbial loop. Climate change and a subsequent warming of the surface ocean may lead to a shift in the protist community toward smaller cell size in the future, but in light of these findings these changes may not necessarily lead to a reduction in the strength of the biological carbon pump.
ContributorsAmacher, Jessica (Author) / Neuer, Susanne (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Lomas, Michael (Committee member) / Wojciechowski, Martin (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2011
Description
Functional magnetic resonance imaging (fMRI) has been widely used to measure the retinotopic organization of early visual cortex in the human brain. Previous studies have identified multiple visual field maps (VFMs) based on statistical analysis of fMRI signals, but the resulting geometry has not been fully characterized with mathematical models. This thesis explores using concepts from computational conformal geometry to create a custom software framework for examining and generating quantitative mathematical models for characterizing the geometry of early visual areas in the human brain. The software framework includes a graphical user interface built on top of a selected core conformal flattening algorithm and various software tools compiled specifically for processing and examining retinotopic data. Three conformal flattening algorithms were implemented and evaluated for speed and how well they preserve the conformal metric. All three algorithms performed well in preserving the conformal metric but the speed and stability of the algorithms varied. The software framework performed correctly on actual retinotopic data collected using the standard travelling-wave experiment. Preliminary analysis of the Beltrami coefficient for the early data set shows that selected regions of V1 that contain reasonably smooth eccentricity and polar angle gradients do show significant local conformality, warranting further investigation of this approach for analysis of early and higher visual cortex.
ContributorsTa, Duyan (Author) / Wang, Yalin (Thesis advisor) / Maciejewski, Ross (Committee member) / Wonka, Peter (Committee member) / Arizona State University (Publisher)
Created2013
Description
Pathogenic Gram-negative bacteria employ a variety of molecular mechanisms to combat host defenses. Two-component regulatory systems (TCR systems) are the most ubiquitous signal transduction systems which regulate many genes required for virulence and survival of bacteria. In this study, I analyzed different TCR systems in two clinically-relevant Gram-negative bacteria, i.e., oral pathogen Porphyromonas gingivalis and enterobacterial Escherichia coli. P. gingivalis is a major causative agent of periodontal disease as well as systemic illnesses, like cardiovascular disease. A microarray study found that the putative PorY-PorX TCR system controls the secretion and maturation of virulence factors, as well as loci involved in the PorSS secretion system, which secretes proteinases, i.e., gingipains, responsible for periodontal disease. Proteomic analysis (SILAC) was used to improve the microarray data, reverse-transcription PCR to verify the proteomic data, and primer extension assay to determine the promoter regions of specific PorX regulated loci. I was able to characterize multiple genetic loci regulated by this TCR system, many of which play an essential role in hemagglutination and host-cell adhesion, and likely contribute to virulence in this bacterium. Enteric Gram-negative bacteria must withstand many host defenses such as digestive enzymes, low pH, and antimicrobial peptides (AMPs). The CpxR-CpxA TCR system of E. coli has been extensively characterized and shown to be required for protection against AMPs. Most recently, this TCR system has been shown to up-regulate the rfe-rff operon which encodes genes involved in the production of enterobacterial common antigen (ECA), and confers protection against a variety of AMPs. In this study, I utilized primer extension and DNase I footprinting to determine how CpxR regulates the ECA operon. My findings suggest that CpxR modulates transcription by directly binding to the rfe promoter. Multiple genetic and biochemical approaches were used to demonstrate that specific TCR systems contribute to regulation of virulence factors and resistance to host defenses in P. gingivalis and E. coli, respectively. Understanding these genetic circuits provides insight into strategies for pathogenesis and resistance to host defenses in Gram negative bacterial pathogens. Finally, these data provide compelling potential molecular targets for therapeutics to treat P. gingivalis and E. coli infections.
ContributorsLeonetti, Cori (Author) / Shi, Yixin (Thesis advisor) / Stout, Valerie (Committee member) / Nickerson, Cheryl (Committee member) / Sandrin, Todd (Committee member) / Arizona State University (Publisher)
Created2013
Description
In blindness research, the corpus callosum (CC) is the most frequently studied sub-cortical structure, due to its important involvement in visual processing. While most callosal analyses from brain structural magnetic resonance images (MRI) are limited to the 2D mid-sagittal slice, we propose a novel framework to capture a complete set of 3D morphological differences in the corpus callosum between two groups of subjects. The CCs are segmented from whole brain T1-weighted MRI and modeled as 3D tetrahedral meshes. The callosal surface is divided into superior and inferior patches on which we compute a volumetric harmonic field by solving the Laplace's equation with Dirichlet boundary conditions. We adopt a refined tetrahedral mesh to compute the Laplacian operator, so our computation can achieve sub-voxel accuracy. Thickness is estimated by tracing the streamlines in the harmonic field. We combine areal changes found using surface tensor-based morphometry and thickness information into a vector at each vertex to be used as a metric for the statistical analysis. Group differences are assessed on this combined measure through Hotelling's T2 test. The method is applied to statistically compare three groups consisting of: congenitally blind (CB), late blind (LB; onset > 8 years old) and sighted (SC) subjects. Our results reveal significant differences in several regions of the CC between both blind groups and the sighted groups; and to a lesser extent between the LB and CB groups. These results demonstrate the crucial role of visual deprivation during the developmental period in reshaping the structural architecture of the CC.
ContributorsXu, Liang (Author) / Wang, Yalin (Thesis advisor) / Maciejewski, Ross (Committee member) / Ye, Jieping (Committee member) / Arizona State University (Publisher)
Created2013
Description
Sparsity has become an important modeling tool in areas such as genetics, signal and audio processing, medical image processing, etc. Via the penalization of l-1 norm based regularization, the structured sparse learning algorithms can produce highly accurate models while imposing various predefined structures on the data, such as feature groups or graphs. In this thesis, I first propose to solve a sparse learning model with a general group structure, where the predefined groups may overlap with each other. Then, I present three real world applications which can benefit from the group structured sparse learning technique. In the first application, I study the Alzheimer's Disease diagnosis problem using multi-modality neuroimaging data. In this dataset, not every subject has all data sources available, exhibiting an unique and challenging block-wise missing pattern. In the second application, I study the automatic annotation and retrieval of fruit-fly gene expression pattern images. Combined with the spatial information, sparse learning techniques can be used to construct effective representation of the expression images. In the third application, I present a new computational approach to annotate developmental stage for Drosophila embryos in the gene expression images. In addition, it provides a stage score that enables one to more finely annotate each embryo so that they are divided into early and late periods of development within standard stage demarcations. Stage scores help us to illuminate global gene activities and changes much better, and more refined stage annotations improve our ability to better interpret results when expression pattern matches are discovered between genes.
ContributorsYuan, Lei (Author) / Ye, Jieping (Thesis advisor) / Wang, Yalin (Committee member) / Xue, Guoliang (Committee member) / Kumar, Sudhir (Committee member) / Arizona State University (Publisher)
Created2013
Description
The study of bacterial resistance to antimicrobial peptides (AMPs) is a significant area of interest as these peptides have the potential to be developed into alternative drug therapies to combat microbial pathogens. AMPs represent a class of host-mediated factors that function to prevent microbial infection of their host and serve as a first line of defense. To date, over 1,000 AMPs of various natures have been predicted or experimentally characterized. Their potent bactericidal activities and broad-based target repertoire make them a promising next-generation pharmaceutical therapy to combat bacterial pathogens. It is important to understand the molecular mechanisms, both genetic and physiological, that bacteria employ to circumvent the bactericidal activities of AMPs. These understandings will allow researchers to overcome challenges posed with the development of new drug therapies; as well as identify, at a fundamental level, how bacteria are able to adapt and survive within varied host environments. Here, results are presented from the first reported large scale, systematic screen in which the Keio collection of ~4,000 Escherichia coli deletion mutants were challenged against physiologically significant AMPs to identify genes required for resistance. Less than 3% of the total number of genes on the E. coli chromosome was determined to contribute to bacterial resistance to at least one AMP analyzed in the screen. Further, the screen implicated a single cellular component (enterobacterial common antigen, ECA) and a single transporter system (twin-arginine transporter, Tat) as being required for resistance to each AMP class. Using antimicrobial resistance as a tool to identify novel genetic mechanisms, subsequent analyses were able to identify a two-component system, CpxR/CpxA, as a global regulator in bacterial resistance to AMPs. Multiple previously characterized CpxR/A members, as well as members found in this study, were identified in the screen. Notably, CpxR/A was found to transcriptionally regulate the gene cluster responsible for the biosynthesis of the ECA. Thus, a novel genetic mechanism was uncovered that directly correlates with a physiologically significant cellular component that appears to globally contribute to bacterial resistance to AMPs.
ContributorsWeatherspoon-Griffin, Natasha (Author) / Shi, Yixin (Thesis advisor) / Clark-Curtiss, Josephine (Committee member) / Misra, Rajeev (Committee member) / Nickerson, Cheryl (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2013
Description
Microbial electrochemical cells (MXCs) are promising platforms for bioenergy production from renewable resources. In these systems, specialized anode-respiring bacteria (ARB) deliver electrons from oxidation of organic substrates to the anode of an MXC. While much progress has been made in understanding the microbiology, physiology, and electrochemistry of well-studied model ARB such as Geobacter and Shewanella, tremendous potential exists for MXCs as microbiological platforms for exploring novel ARB. This dissertation introduces approaches for selective enrichment and characterization of phototrophic, halophilic, and alkaliphilic ARB. An enrichment scheme based on manipulation of poised anode potential, light, and nutrient availability led to current generation that responded negatively to light. Analysis of phototrophically enriched communities suggested essential roles for green sulfur bacteria and halophilic ARB in electricity generation. Reconstruction of light-responsive current generation could be successfully achieved using cocultures of anode-respiring Geobacter and phototrophic Chlorobium isolated from the MXC enrichments. Experiments lacking exogenously supplied organic electron donors indicated that Geobacter could produce a measurable current from stored photosynthate in the dark. Community analysis of phototrophic enrichments also identified members of the novel genus Geoalkalibacter as potential ARB. Electrochemical characterization of two haloalkaliphilic, non-phototrophic Geoalkalibacter spp. showed that these bacteria were in fact capable of producing high current densities (4-8 A/m2) and using higher organic substrates under saline or alkaline conditions. The success of these selective enrichment approaches and community analyses in identifying and understanding novel ARB capabilities invites further use of MXCs as robust platforms for fundamental microbiological investigations.
ContributorsBadalamenti, Jonathan P (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Rittmann, Bruce E. (Committee member) / Torres, César I (Committee member) / Vermaas, Willem (Committee member) / Arizona State University (Publisher)
Created2013