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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Detección de anticuerpos neutralizantes contra los virus Rocío, Ilheus y Oeste del Nilo en una población humana de Iquitos entre los años 2003-2007

Juárez Espinoza, Diana Stephanie January 2009 (has links)
Los flavivirus se encuentran distribuidos en las principales zonas tropicales del mundo, nuestra Amazonía es endémica para virus como el dengue; sin embargo, alberga también otros virus que aún no han sido estudiados. El objetivo fue determinar la presencia de anticuerpos neutralizantes contra los virus Rocío, Ilheus y Oeste del Nilo; utilizando la técnica del ELISA como tamizaje para la detección de muestras positivas y la microneutralización como prueba confirmatoria. Se analizaron un total de 400 sueros por ELISA IgG de personas en fase convaleciente de la localidad de Iquitos entre los años 2003 y 2007. 152 sueros fueron negativos y 248 dieron positivo por ELISA IgG, de las cuales se confirmó mediante microneutralización 23 sueros positivos para el virus Ilheus y 7 sueros positivos para el virus Rocío. El valor de reacción cruzada para la prueba de ELISA fue de 87%. Los resultados indican la existencia de anticuerpos neutralizantes contra el virus Ilheus en un 5.75% de los sueros analizados y también la presencia de anticuerpos neutralizantes contra el virus Rocío en un 1.75% de los sueros, afortunadamente las infecciones por estos virus en la localidad de Iquitos no es significativa con respecto a la observada para el virus dengue (34.7%). / The flavivirus are distributed in major tropical areas around the world, our Amazonia is endemic to viruses such as dengue, but also houses many others which have not yet been studied. The aim was to evaluate the presence of neutralizing antibodies against Rocio, Ilheus and West Niles viruses using the technique of ELISA as screening for the detection of positive samples and the microneutralization as confirmatory test. Were analyzed a total of 400 sera by Elisa IgG from people in convalescent phase of the city of Iquitos during the years 2003 - 2007. 152 were negative and 248 were positive by Elisa IgG, of which was confirmed by microneutralization 23 sera positive for the virus Ilheus and 7 sera positive for the virus Rocio. The value of cross-reactivity for the ELISA was 87%. The results indicate the existence of neutralizing antibodies against the Ilheus virus in 5.75% of the sera analyzed and the presence of neutralizing antibodies against the Rocio virus in 1.75% of the sera. Fortunately the presence of these viruses in the city of Iquitos is not significant compared to that observed for the dengue virus (34.7%). / Tesis
32

Luminex Microsphere Immunoassay Offers an Improved Method in Testing for Antibodies to Eastern Equine Encephalitis Virus in Sentinel Chicken Sera

Fitzpatrick, Kelly Ann 18 July 2008 (has links)
Eastern Equine Encephalitis virus has a human mortality rate of 30% of those cases diagnosed, while 30% of those surviving infection remain with neurological sequelae for life (CDC.gov, 2007). The use of sentinel chickens for surveillance of arboviruses that are known to use birds as a reservoir host, such as St. Louis Encephalitis (SLE), West Nile (WN) virus, Eastern Equine Encephalitis (EEE) and Highlands J (HJ) virus, in Florida began with the Sentinel Chicken Arboviral Surveillance Network in 1978 (Day and Stark, 1996). This network enables the activation of an early warning system for citizens, as well as, county epidemiologists and those in mosquito control, allowing for a coordinated effort of disease prevention. Methods currently used at the Florida Department of Health, Tampa Branch Laboratory include screening of submitted sera for antibodies to these arboviruses of epidemiologic importance by way of the hemagglutination inhibition test (HAI), and confirmation by the IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA) and Plaque Reduction Neutralization test if the MAC-ELISA proves to be negative. While these tests combined are providing the results needed, the time to result can be a week or greater depending on the initial screening result in the HAI tests. The Microsphere Assay Technology provides an accurate, more rapid (a day or two instead of a week or more) detection method including both a screening and confirmation protocol specifically designed to test for antibody to EEE in sentinel chicken sera. Two sera out of the thousands tested that were tested by HAI shown to be negative in standard testing, resulted as positive by the MIA method and therefore indicated a missed positive. The sensitivity and specificity, positive and negative predictive values of this new protocol as compared with MAC-ELISA as a reference standard indicated that both tests were remarkably similar; Providing sensitivity near 80%, specificity and PPV at 99%, and negative predictive values at 90% for MAC-ELISA and 94% for the MIA. Finally it was determined that Highlands J virus will not have any impact on the testing protocol and results of this test.
33

Impact of West Nile Virus on the Natural History of St. Louis Encephalitis Virus in Florida

Ottendorfer, Christy L 07 April 2008 (has links)
The emergence of West Nile virus (WNV) has raised important questions about the capacity of the public health infrastructure to implement surveillance and control programs for WNV and other emerging or re-emerging arboviruses in the United States. Florida's mild climate supports year round enzootic transmission of WNV, St. Louis encephalitis virus (SLEV), and Eastern Equine Encephalitis virus (EEEV). It is unknown what effect the establishment of WNV (in 2001) will have on SLEV transmission in Florida, where these closely related flaviviruses share amplifying hosts, habitats, and vectors. An Arbovirus Isolation Network was formed to obtain and characterize arbovirus strains collected from a large population of naturally exposed birds, including sentinel chickens and wild birds admitted to rehabilitation centers in Florida. Weekly sentinel seroconversion data was used to target sampling of chicken flocks at 37 active sites (17 WNV, 7 EEEV, and 13 SLEV) in eight counties from 224 birds during 2005-2006. Sampling of wild birds occurred following admittance at rehabilitation centers in 2006, based on symptoms and known amplifying host species (n=64), but virus was not detected. We report the isolation of St. Louis encephalitis virus, West Nile virus and detection of Eastern Equine Encephalitis viral RNA from cloacal swabs of naturally exposed adult sentinel chickens. We also report the first known dual infection and isolation of St. Louis encephalitis and West Nile viruses from one chicken. In addition, a novel flavivirus strain was detected in two chickens. Early season transmission of WNV appears to limit subsequent infection and amplification of SLEV late in the year. Phylogenetic analysis revealed that the introduction (and re-introduction) of South American (Brazil) SLEV occurred in 1972 and 2006 in Florida. These strains represent the first reported isolation of South American strains of SLEV in the United States, with placement in Lineage VA and VB, as proposed by Kramer and Chandler (2001). Arbovirus isolation remains an effective tool for surveillance programs and a targeted strategy is most cost-effective to capture arboviruses in their natural settings for molecular epidemiology analysis that can elucidate genetic variations impacting virulence, mosquito infectivity, and disease potential of these pathogens.
34

Development and Characterization of Reporter-Expressing Zika Viruses

Woolley, Michael E. 01 August 2018 (has links)
In recent years, Zika virus (ZIKV) has garnered worldwide attention due to its epidemic spread throughout the Americas and due to the newly recognized link between ZIKV infection and neurological diseases, including microcephaly and Guillain-Barré syndrome. ZIKV is a mosquito-borne member of the genus Flavivirus, which includes the other prominent human pathogens Japanese encephalitis virus, West Nile virus, dengue virus, and yellow fever virus. Many questions about the biology of ZIKV and how it causes disease remain unanswered. Furthermore, there currently are no vaccines or licensed antiviral drugs available to treat ZIKV infection. The goal of this study was to create new tools to aid in ZIKV research and in the creation of new therapies for ZIKV infection. To accomplish this, we created two recombinant ZIKVs–one expressing a green fluorescent protein reporter gene and the other expressing a luciferase reporter gene. These additional genes will allow us to easily visualize infected cells and to precisely track levels of viral replication over time, thereby facilitating new experimental approaches and providing a means to gain insights about ZIKV. We believe that these two new versions of ZIKV will prove to be useful tools in the urgent task of better understanding how ZIKV causes disease and its links to other complications, as well as in the process of developing and testing new treatments to combat ZIKV infection.
35

Development and Application of a Reverse Genetics System for Zika Virus

Frank, Jordan C. 01 December 2018 (has links)
Zika virus (ZIKV) has emerged in many regions of the world, with infection outcomes spanning from no apparent illness to crippling nervous system disease. ZIKV and its close relatives, West Nile virus, Japanese encephalitis virus, dengue virus, and yellow fever virus are primarily transmitted by mosquitoes. Three ZIKVs were selected: MR-766 (Uganda, 1947), P6-740 (Malaysia, 1966), and PRVABC-59 (Puerto Rico, 2015), whose place of origin and time of isolation differ substantially. Stable, complementary DNA (cDNA) copies of the three ZIKV RNA genomes were cloned to examine the significance of viral and host genetic variations in directing ZIKV infection outcomes. Using a new toolbox for ZIKV genome engineering and protein analysis, combined with various cell culture and mouse infection model systems, the following were determined: (1) Genome-wide landscape of viral gene products and their related species, with several immuno-reactive gene products identified in the case of all three cloned ZIKVs. (2) Viral replicability in cultured cells, varied significantly depending on the virus strain and host cell type, with one cow cell line being resistant to ZIKV infection. (3) Virus induced neurological disease in mice, differed dramatically depending on the virus dose and strain, mouse age and strain, route of infection, and presence or absence of immune system components. Overall, the findings demonstrate the impact of the viral and host genetic backgrounds on the ability of ZIKV to replicate and cause disease. The ZIKV strain-specific characterizations and molecular instruments described will provide multiple avenues for developing and testing medical countermeasures.
36

Parasitizing behavior of <em>Ixodes uriae</em> ticks on Chilean Magellanic penguin (<em>Spheniscus magellanicus</em>) and their importance as pathogen vectors

Stedt, Johan January 2009 (has links)
<p>Ticks are vectors for a larger number of viruses and bacteria than all other arthropod taxa, including mosquitoes. In Europe is it foremost Borrelia spirochetes and the Flavivirus Tick-borne Encephalitis virus that cause disease in humans. In this study, the tick species <em>Ixodes uriae</em> has been studied. <em>I.</em><em> uriae</em> have a circumpolar distribution in both hemisphere and can be found both in Arctic and Antarctica. I collected ticks from Magellanic penguins in south Chile and analyzed them to see if they carry <em>Borrelia</em> spirochetes or Flavivirus. Totally were 218 ticks collected from 165 controlled penguins. All ticks were collected from adult penguins and the parasitizing ticks were all found in the auditory meatus which is a new phenomena compared to earlier studies. Both <em>Borrelia</em> spirochetes and Flavivirus were found in the collected ticks using PCR techniques. This is an interesting result since not much research has been performed in this geographical area before. Until date there is only one species of <em>Borrelia</em> (<em>Borrelia</em> <em>garinii</em>) found in <em>I.</em><em> uriae</em> on the southern hemisphere and new Flavivirus is regularly found around the world.  Unfortunately we have not been able to determine species of the <em>Borrelia </em>spirochetes or Flavivirus so far but this work will be continued. <strong></strong></p>
37

Functional Analysis of the Murine Oligoadenylate Synthetase 1b (Oas1b)

Elbahesh, Husni 12 January 2006 (has links)
The flavivirus resistance gene, Flv, in mice has been identified as 2'-5' oligoadenylate synthetase 1b (Oas1b). Susceptible mice produce a protein that is truncated (Oas1btr) at the C-terminus due to a premature stop codon encoded by a C820T transition. Mice produce 8 Oas1 proteins, Oas1a-Oas1h. In the present study, Oas1a, Oas1b and Oas1btr were expressed as MBP-fusion proteins in bacteria and purified. 2-5A synthetase activity was demonstrated using MBP-Oas1a, while neither MBP-Oas1b nor MBP-Oas1btr were functionally active. The 2-5A synthetase activity of MBP-Oas1a was inhibited in a dose-dependent manner by the addition of MBP-Oas1b but not MBPOas1btr. Finally, three RNA probes were synthesized from the 3' end of the WNV Eg101 genome and used to test the ability of the expressed Oas1 proteins to bind to viral RNA. Results of the RNA binding activity assays suggest Oas1 proteins may specifically interact with regions of WNV RNA.
38

Functional Analysis of Host Cell Proteins and Stress Responses that Inhibit West Nile Virus Infection

Courtney, Sean C 14 December 2011 (has links)
Resistance to flavivirus-induced disease is conferred by a single gene that encodes oligoadenylate synthetase (Oas) 1b (Oas1b). Oas1b is not a functional synthetase suggesting its anti-flavivirus mechanism is RNase L-independent and that it may be mediated by interactions with other host cell protein(s). A yeast two-hybrid screen was used to identify host cell binding partners of Oas1b. Candidate partners were confirmed by yeast co-transformation and co-immunoprecipitation analyses. Oxysterol binding protein-related 1L (ORP1L) and ATP binding cassette subfamily F 3 (ABCF3) were found to interact with Oas1b. RNAi knockdown studies suggested that ORP1L and ABCF3 form a tripartite complex with Oas1b that is critical for the flavivirus-induced disease resistance mechanism. Stresses including oxidation, nutrient starvation, and viral infections often induce the formation of stress granules (SGs) in eukaryotic cells. In response to stress, eIF2α kinases phosphorylate eIF2α leading to stalled 48S pre-initiation complexes and SG formation. West Nile virus (WNV) Eg101 infections were previously shown not to induce the formation of SGs. Infections with viruses of other natural WNV strains, as well as a WNV lineage 1/2-based infectious clone (W956IC) were analyzed and only W956IC infections were found to induce SGs. eIF2α kinase knockout MEFs were used to show that the W956IC-induced SGs were PKR-dependent. WNV chimeras were made by inserting Eg101 genes into the W956IC backbone. Chimeras replacing NS5 or NS1 and NS5 or NS1 and NS3 and NS4a reduced SG formation as well as early viral RNA synthesis similar to Eg101 infections. W956IC infections but not Eg101 infections were shown to produce exposed viral dsRNA at early times after infection. The data suggest that natural WNV infections evade the cell SG response by suppressing the amplification of viral RNA until cytoplasmic membranes have been remodeled to protect replication complexes from detection. It was previously reported that WNV Eg101 infections inhibited the formation of arsenite-induced SGs. The ability of other natural WNV strain infections to inhibit SG formation by arsenite (HRI), DTT (PERK), W956IC co-infection (PKR), and heat shock treatments was assessed. WNV infections only inhibited arsenite-induced SG formation suggesting that WNV infections specifically suppress the response to oxidative intermediates.
39

Parasitizing behavior of Ixodes uriae ticks on Chilean Magellanic penguin (Spheniscus magellanicus) and their importance as pathogen vectors

Stedt, Johan January 2009 (has links)
Ticks are vectors for a larger number of viruses and bacteria than all other arthropod taxa, including mosquitoes. In Europe is it foremost Borrelia spirochetes and the Flavivirus Tick-borne Encephalitis virus that cause disease in humans. In this study, the tick species Ixodes uriae has been studied. I. uriae have a circumpolar distribution in both hemisphere and can be found both in Arctic and Antarctica. I collected ticks from Magellanic penguins in south Chile and analyzed them to see if they carry Borrelia spirochetes or Flavivirus. Totally were 218 ticks collected from 165 controlled penguins. All ticks were collected from adult penguins and the parasitizing ticks were all found in the auditory meatus which is a new phenomena compared to earlier studies. Both Borrelia spirochetes and Flavivirus were found in the collected ticks using PCR techniques. This is an interesting result since not much research has been performed in this geographical area before. Until date there is only one species of Borrelia (Borrelia garinii) found in I. uriae on the southern hemisphere and new Flavivirus is regularly found around the world.  Unfortunately we have not been able to determine species of the Borrelia spirochetes or Flavivirus so far but this work will be continued.
40

Detección de anticuerpos neutralizantes contra los virus Rocío, Ilheus y Oeste del Nilo en una población humana de Iquitos entre los años 2003-2007

Juárez Espinoza, Diana Stephanie January 2009 (has links)
Los flavivirus se encuentran distribuidos en las principales zonas tropicales del mundo, nuestra Amazonía es endémica para virus como el dengue; sin embargo, alberga también otros virus que aún no han sido estudiados. El objetivo fue determinar la presencia de anticuerpos neutralizantes contra los virus Rocío, Ilheus y Oeste del Nilo; utilizando la técnica del ELISA como tamizaje para la detección de muestras positivas y la microneutralización como prueba confirmatoria. Se analizaron un total de 400 sueros por ELISA IgG de personas en fase convaleciente de la localidad de Iquitos entre los años 2003 y 2007. 152 sueros fueron negativos y 248 dieron positivo por ELISA IgG, de las cuales se confirmó mediante microneutralización 23 sueros positivos para el virus Ilheus y 7 sueros positivos para el virus Rocío. El valor de reacción cruzada para la prueba de ELISA fue de 87%. Los resultados indican la existencia de anticuerpos neutralizantes contra el virus Ilheus en un 5.75% de los sueros analizados y también la presencia de anticuerpos neutralizantes contra el virus Rocío en un 1.75% de los sueros, afortunadamente las infecciones por estos virus en la localidad de Iquitos no es significativa con respecto a la observada para el virus dengue (34.7%). / The flavivirus are distributed in major tropical areas around the world, our Amazonia is endemic to viruses such as dengue, but also houses many others which have not yet been studied. The aim was to evaluate the presence of neutralizing antibodies against Rocio, Ilheus and West Niles viruses using the technique of ELISA as screening for the detection of positive samples and the microneutralization as confirmatory test. Were analyzed a total of 400 sera by Elisa IgG from people in convalescent phase of the city of Iquitos during the years 2003 - 2007. 152 were negative and 248 were positive by Elisa IgG, of which was confirmed by microneutralization 23 sera positive for the virus Ilheus and 7 sera positive for the virus Rocio. The value of cross-reactivity for the ELISA was 87%. The results indicate the existence of neutralizing antibodies against the Ilheus virus in 5.75% of the sera analyzed and the presence of neutralizing antibodies against the Rocio virus in 1.75% of the sera. Fortunately the presence of these viruses in the city of Iquitos is not significant compared to that observed for the dengue virus (34.7%).

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