Life Sciences Commons^™

Modified Vaccine Vectors To Understand Adjuvant Functions Of Listeria During Chronic Schistosomiasis, Stephanie K. Norwood

Biological Sciences Theses & Dissertations

Vaccination is one of the most effective strategies employed to prevent infectious diseases. Successful vaccination is dependent upon the induction of a specific, robust, and prolonged immune response. One of the major challenges faced by vaccine development is vaccine failure due to host-related factors that can modulate the immune system, which leads to non-responsiveness to vaccinations. The generation of new vaccine strategies is imperative to combat these effects. Live bacterial vectors are one approach used as they can elicit humoral immunity, cellular immunity, or both. Listeria monocytogenes is a Gram positive, intracellular pathogen that is an effective bacterial vaccine vector …

Mycobacteriosis Of Striped Bass (Morone Saxatilis) In Virginia Tributaries Of The Chesapeake Bay, Joshua S. Mcgilly

Biological Sciences Theses & Dissertations

Mycobacteriosis was first documented in Chesapeake Bay striped bass (Morone saxatilis) in 1997 after fish exhibited emaciation and skin lesions. Since it was first identified, studies of mycobacteriosis in the mainstem of the Chesapeake Bay (2003-2007) and the Rappahannock River (2005-2012) have shown high disease prevalence and disease-associated mortality. Until this study, no current prevalence data existed from the Rappahannock River, and no published prevalence data existed for the James River, leaving a gap in our understanding of this disease in major Chesapeake Bay tributaries. We began gathering mycobacteriosis prevalence data from an existing survey collecting striped bass …

Ixodes Scapularis Src Kinase Is Required For Rickettsial Pathogen Survival In Ticks, Jeremy W. Turck

Biological Sciences Theses & Dissertations

Anaplasma phagocytophilum is an obligate intracellular bacterium that causes disease in humans and animals. It is the causative agent for human anaplasmosis. A. phagocytophilum uses certain strategies to infect both vertebrates and invertebrates. It uses Ixodes scapularis ticks as a vector for spreading infection to other mammal species. This bacterium has a specific path for infection through the salivary glands of its vector host. It also suppresses certain functions such as the inhibition of apoptosis and ROS production in order to increase its survival in ticks. Src kinase, a non-receptor protein-tyrosine kinase, is a major player in cell signaling. Src …

Role Of Ixodes Scapularis Sphingomyelinase-Like Protein (Issmase) In Tick Pathogen Interactions, Pravesh Regmi

Biological Sciences Theses & Dissertations

Arthropod-borne diseases are one of the major concerns throughout the world. Ixodes scapularis (hard tick) is one of the major vectors that is involved in arthropod-borne disease transmission. Langat virus (LGTV) is a model pathogen that is very similar to other medically important flaviviruses such as Tick-Borne Encephalitis virus (TBEV) and Powassan virus (POWV). Sphingomyelinase-like protein (IsSMase, a Sphingomyelinase D or SMase D, a venomous protein ortholog of spiders) is an enzyme present in ticks that helps to catalyze the hydrolysis of the sphingomyelin (cell membrane lipid) into phosphocholine and ceramide. The objective of our study is to delineate the …

Zika Modulates Arthropod Histone Methylation In Mosquito Cells, Telvin Lee Harrell

Biological Sciences Theses & Dissertations

Epigenetics is the heritable series of covalent modifications that affect chromatin structure, gene expression, and protein function. Methylation is one such epigenetic modification that involves the addition of chemical modifying entities, such as methyl groups, on nucleic acids or proteins. Recent studies have reported that Zika virus (ZIKV) modulates methylation of human and viral RNA important for its replication in vertebrate cells. However, little is known whether ZIKV exerts methylation in arthropod vectors. In this study, I show that ZIKV modulates S-adenosyl methionine (SAMe) synthase, an enzyme involved in the production of SAMe, and histone methylation for its survival in …

Molecular Candidates For Blocking The Transmission Of Vector-Borne Diseases, Ashish Naresh Vora

Biological Sciences Theses & Dissertations

Vector-borne diseases (VBDs) require urgent attention as they have a high mortality rate, with 700,000 people dying in a year as of 2017. So far, extremely few reliable vaccination strategies and solutions have emerged. Transmission blocking vaccines are one among many solutions available to manage the control of VBDs. These require identification of both vector and pathogen molecules that play important roles in the transmission, dissemination and establishment of VBDs. Our strategy is to characterize these candidates that play important roles in vector-host-pathogen interactions. This manuscript presents two such studies identifying the participation of two arthropod molecules in vector-host-pathogen interactions. …

Determining The Prevalence And Distribution Of Tick-Borne Pathogens In Southeastern Virginia And Exploring The Transmission Dynamics Of Rickettsia Parkeri In Amblyomma Maculatum, Chelsea L. Wright Thompson

Biological Sciences Theses & Dissertations

Tick-borne pathogens are an increasing threat to human and animal health worldwide. In the United States, cases of Lyme disease, spotted fever rickettsioses, ehrlichiosis and anaplasmosis are on the rise. Factors related to emergence include appearance of a new pathogen, recognition of an existing pathogen and environmental changes that result in new exposure events. Despite the rise in tick-borne disease incidence within many states, including Virginia, there is a paucity of data related to the prevalence and distribution of ticks and tick-borne pathogens.

The first aim of this dissertation research was to determine the tick-borne pathogen composition within tick populations …

Regulation Of Hyaluronate Lyase (Hyla) Expression By Regr A Transcriptional Repressor In Streptococcus Pyogenes, Alexis A. Kordis

Biological Sciences Theses & Dissertations

Streptococcus pyogenes, group A streptococci (GAS), causes diseases ranging from asymptomatic to life threatening. Some strains of S. pyogenes produce extracellular hyaluronate lyase (HylA), a potential virulence factor. HylA is an enzyme that degrades hyaluronic acid, which is found in the extracellular matrix of human tissues. The breakdown of the host tissue contributes to the spread of infection. The hylA gene is not constitutively expressed in vitro, which implies regulation.

A proposed regulator of hyaluronate lyase expression is RegR, a LacI/GalR like protein. A vector containing disrupted regR was electro-transformed into S. pyogenes M-type 22 strain 10403. Growth characteristics …

In Vitro Selection Of Chloroquine Tolerant Plasmodium Falciparum Parasites, Daniel A. Daley

Biological Sciences Theses & Dissertations

Malaria is among the most devastating human diseases, and a majority of lethal cases are caused by the protozoan parasite, Plasmodiumfalciparum. The emergence of multi-drug resistant P.falciparum is a major obstacle to malaria control and is highlighted by the abandonment of chloroquine (CQ) as a first-line treatment of P.falciparum infections worldwide. Chloroquine resistance (CQR) is associated primarily with mutations in the transmembrane digestive vacuole protein, PfCRT. However, CQR P.falciparum parasites harboring the same mutant pfcrt allele vary in their CQ response, suggesting the CQ response is multigenic in nature. No gene outside of pfcrt is completely associated with CQR. Thus, …

Effects Of The Parasitic Dinoflagellate Hematodinium Sp. On Blue Crab (Callinectes Sapidus) Activity Predation And Habitat Selection, John M. Tiggelaar Ii

Biological Sciences Theses & Dissertations

The blue crab Callinectes sapidus occurs along the Atlantic and Gulf coasts of the United States, and in high salinity regions, they are subject to lethal infection by the parasitic dinoflagellate Hematodinium. In Virginia's seaside estuaries, the prevalence of Hematodinium infection of C. sapidus can sometimes exceed 50%, threatening the commercial fishery for this species. Indeed, other commercially important crustacean fisheries have approached collapse due to Hematodinium infections. Most studies of this host-parasite interaction have focused on epidemiology, host-pathogen dynamics, and pathogen transmission, and little is known about the impact of the parasite on host behavior and population dynamics. …

The Role Of Human Endogenous Retroviruses In Renal Cell Carcinoma, Michele D. Tisdale

Biological Sciences Theses & Dissertations

Human endogenous retroviruses make up approximately 8-9% of the human genome. A number of expressed HERVs, those that are actively transcribing, have been associated with various cancers. Suppression mechanisms that control HERV expression often fail or become more permissive in tissues where expression should be restricted. Previous studies have identified HERV expression in breast cancer tissues, whereas normal tissue HERV expression remained suppressed. In addition, studies of DNA hypermethylation have correlated with the ability to contribute to cancer development. Hypermethylation of several tumor suppressor genes occurs frequently in cancers and alterations in promoter regions could contribute to the development of …

Inhibition Of Yeast Hexokinase By The Antimalarial Drug Artemisinin: Probing Mechanism Of Action With A Model Enzyme, Jennifer S. Spence

Biological Sciences Theses & Dissertations

A leading infectious cause of death, malaria threatens approximately half of the world's population, and drug-resistant strains of Plasmodium falciparum have created immense difficulty in chemotherapy of the disease. The artemisinin (ART) class of antimalarials may represent a powerful solution. In addition to their safety, effectiveness, and moderate cost, they are the only drugs in use for which there has been no widespread evidence of clinical resistance. The exact parasiticidal mechanism of ART is highly contested, but evidence suggests that protein alkylation may play a role in cytotoxicity. in vitro essays were performed using yeast hexokinase (HK) to demonstrate a …

Antimicrobial Activity Screening Of Recombinant And Synthetic Varasin A Defensin From The Hard Tick Dermacentor Variabilis Against Various Bacteria, Julia A. Sharp

Biological Sciences Theses & Dissertations

Hematophagous arthropods, such as ticks and mosquitoes, rely on their innate immune system for defense against pathogens ingested in a blood meal as well as those acquired through injury. In response to pathogen recognition, the production of antimicrobial peptides, such as defensin, is typically upregulated. Varisin, a defensin, is thought to be a key component in the immunocompetence of the hard tick D. variabilis against Borrelia burgdorferi, the causative agent of Lyme disease. To study the antimicrobial effects of varisin, recombinant varisin was expressed by both insect cells and E coli. Purification of the protein followed by enterokinase treatment yielded …

The Plasmodium Falciparum Chloroquine Resistance Transporter, Pfcrt, Mediates The Activity Of Chloroquine-Resistance Reversal Agents In The Malaria Parasite, Kristin Lane

Biological Sciences Theses & Dissertations

Chloroquine (CQ) resistant Plasmodium falciparum is a serious problem affecting 3.2 billion people in over 100 countries today. Most endemic malarious countries are among the poorest in the world and lack the resources to replace the inexpensive and highly effective CQ. CQ resistance (CQR) reversal agents are a potentially inexpensive solution to restoring CQ efficacy. CQR reversal agents are drugs that have little to no antimalarial activity alone, but in combination with CQ, they increase dmg accumulation in the parasite and enhance the sensitivity to CQ in CQR parasites. PfCRT is a putative transporter located on the parasite digestive vacuole …

Defensin Transcript Distribution In Tissues And Life Stages Of The Ixodid Ticks Amblyomma Americanum And Ixodes Scapularis, Stephanie M. Todd

Biological Sciences Theses & Dissertations

A number of bacterial, viral, and protozoan diseases are transmitted to humans via arthropods. Arthropods possess an innate immune system to destroy invading microorganisms. However, arthropods unable to rid their systems of pathogens function as disease vectors. The American dog tick, Dermacentor variabilis, destroys invading Borrelia burgdorferi spirochetes, preventing transmission. In contrast, the black-legged tick, Ixodes scapularis, which is unable to destroy acquired B. burgdorferi, successfully vectors the pathogen. The Lone Star tick, Amblyomma americanum, vectors a similar pathogen called Borrelia lonestari. The distribution of defensin, an antimicrobial peptide of the innate immune system, was examined in A. americanum and/. …

The Defensin Gene In Dermacentor Variabilis And Ixodes Scapularis, Katherine Corbett Seguin

Biological Sciences Theses & Dissertations

In response to microbial challenge, invertebrates rely on their innate immune response to recognize and destroy harmful pathogens. One of the primary proteins produced by the response and that has been observed in many invertebrates, including insects, mussels, and ticks, is defensin. These proteins are responsible for forming pores in the membranes of invading microbes thereby destroying them. This study examined the gene coding region for defensin in two important tick disease vectors, Dermacentor variabilis and Ixodes scapularis. PCR amplification of the genes from tick chromosomal DNA resulted in the amplification of a 225 base pair amplicon. Sequencing of …

Characterization Of Spy1600 A Putative Hyaluronidase Gene In Group A Streptococci, Karin M. Berling

Biological Sciences Theses & Dissertations

Group A Streptococci (GAS), also known as Streptococcus pyogenes, can cause a variety of human diseases ranging from asymptomatic to life threatening. Exactly how a single type of organism is able to inflict such a multitude of diseases remains to be fully understood. One possibility includes the large number of secreted virulence factors expressed by the organism. The recent sequencing of three streptococcal genomes has indicated the existence of several previously unknown genes, some of which may encode possible virulence factors. Among these is Spy1600, which based on its sequence similarities has been proposed to encode a hyaluronidase, a …

Development Of An Electrotransformation Technique For Streptococcus Iniae And Preliminary Characterization Of The Hemolysin Associated With This Bacterium, Kimberly Ann Hahn

Biological Sciences Theses & Dissertations

Streptococcus iniae is a gram-positive organism responsible for causing disease in both freshwater as well as saltwater fish. Every year fisheries lose fish by the tons due to diseases caused by this organism. In 1991, the first reported human case of disease associated with this organism was described. Since this initial case, there have been numerous other reported cases of S. iniae infections. This organism is a catalase negative, facultatively anaerobic organism that produces a capsule and when plated onto blood agar demonstrates β-hemolytic activity.

In this study, the relationship between the hemolysin produced by S. iniae and the lactate …

Investigations Into The Innate Resistance Of The Tick, Dermacentor Variabilis, When Challenged With The Bacterium, Escherichia Coli, Shane Michael Ceraul

Biological Sciences Theses & Dissertations

In addition to the soluble response, many invertebrates control bacterial infections by means of phagocytosis or melanotic encapsulation. In some insects, Escherichia coli growth is reported to be inhibited by aggregation/encapsulation. Soluble and phagocytic responses to bacterial challenge have been reported in ticks, but evidence of an aggregation/encapsulation response was reported only for inanimate (araldite) implants. This study was done to determine how ticks control infection by E. coli. Ticks were challenged by direct inoculation of bacteria into the hemocoel cavity. Using plate counts, no viable E. coli were detected I hour post-inoculation. A direct fluorescence assay (DF A) …

Effect Of Magnesium On The Production Of Scna And Scnr By Streptococcus Pyogenes, Strain Ff22, Laura E. Quinn

Biological Sciences Theses & Dissertations

The lantibiotic SA-FF22, produced by Streptococcus pyogenes strain FF22, was the first described antimicrobial peptide produced by a Streptococcus species. S. pyogenes is a group A Streptococcus responsible for such human illness as strep-throat, rheumatic fever, necrotizing fasciitis, endocarditis, and meningitis. Previous studies of SA-FF22 have shown that antimicrobial activity is lost in the presence of lmM magnesium. We hypothesize that the lack of SA-FF22 activity in the presence of magnesium is due to an absence of transcription of scnA, the gene encoding SA-FF22. The lack of transcriptional activation of scnA may be due to an absence of ScnR, a …

Kinetic Characterization Of Tetracycline Binding And Release By Demineralized Bone - Dfdba, Orner Kabil

Biological Sciences Theses & Dissertations

The microbial etiology of periodontal diseases has led to widespread research in the development of methods and local delivery systems to increase the efficacy of antibiotic therapy. Several drug delivery systems employing biodegradable and nonbiodegradable carriers have been shown to release antibiotics directly into periodontal pockets. The purpose of this study was to determine the binding and release kinetics of tetracycline by demineralized bone. Further aspects of the study include in vitro evaluation of DFDBA (demineralized freeze-dried bone allografts) as a tetracycline carrier system for periodontal therapy. Experiments were performed which employed different tetracycline concentrations with constant amounts of bone …

An Extracellular Protein Produced By Staphylococcus Hominis Strain Αm With Antimicrobial Activity Against Mycobacterium Spp, Sandra May Jacobsen

Biological Sciences Theses & Dissertations

The inhibitory activity exhibited by Staphylococcus hominis strain αM toward Mycobacterium species was examined. These studies included determining the conditions that maximized inhibitory agent production, analyzing characteristics of the agent, determining the time of agent production, ascertaining plasmid possession and the role of plasmids in the production of this inhibitory agent, and ascertaining the antimicrobial activity of other strains of S. hominis. On solid and in liquid media, S. hominis strain αM exhibits a unique inhibitory activity toward Mycobacterium species that is not demonstrated by Staphylococcus epidermidis or other S. hominis strains. Maximum agent production and recovery was …

Characterization Of An Antiviral Agent Based On Nonionic Surfactants And It's Effects On Human Dermal Fibroblasts, Ji Young Li

Biological Sciences Theses & Dissertations

The AIDS ·pandemic has directed various research endeavors towards finding an appropriate method for eliminating all potentially infectious material within bone allografts before implantation into a recipient. To that effect, Panavirocide was conceived by Medicine and Applied Science·s, Inc. This compound, in which three nonionic surfactants serve as the active agents, has been shown to inactivate HIV-1 particles within blood and blood products. Because Panavirocide has never been used with allografts, the purpose of the present research was to characterize the nonionic surfactants for the putative alteration of the formulation by determining the critical micelle concentration values and to determine …

The Distribution And Occurrence Of Aerobic Heterotrophic Antimicrobic-Producing Bacteria Isolated From The Lower Chesapeake Bay, Linda Lea Gilmer

Biological Sciences Theses & Dissertations

Three different estuarine microenvironments in the lower Chesapeake Bay were investigated for the occurrence and geographical distribution of antimicrobic-producing bacteria. Samples were taken from the water column, fish skin, and algal surfaces. A total of 1472 bacterial isolates were assayed for antimicrobial activity against fungal, Gram-negative and Gram-positive bacterial test organisms. Of the total bacterial isolates assayed, 5. 2% were active antimicrobic producers. Algal surf aces were shown to have a higher incidence of antimicrobic-producing bacteria than the water column or fish skin. No antimicrobic activity was demonstrated by bacteria isolated from the flounder fish skin. The majority of the …

Electrostatic Effects On Airborne Asbestos Monitoring, Roxanne Francis

Biological Sciences Theses & Dissertations

The affects of electrostatic forces on the Membrane Filter Method (MFM) used for air-borne asbestos monitoring have been investigated for many years. Several studies have indicated that these forces interfere with the collection of asbestos fibers on the membrane filter, which results in an underestimated analysis of the airborne concentration. By varying the electroconductivity of the extension cowls on the filter cassettes, it was speculated that the significance of the electrostatic forces could be statistically analyzed. Four sets of filter cassettes with grounded conductive (GC) extension cowls, ungrounded conductive (UC) extension cowls, grounded nonconductive (GN) extension cowls, and ungrounded nonconductive …

Interactions Between Aquatic Chromogenic Bacteria And Pathogenic Vibrio Spp., John Louis Harris

Biological Sciences Theses & Dissertations

Interactions between populations inhabiting an ecosys­tem are responsible, in large part, for determining which species coexist in that ecosystem. In this study, interac­tions between selected Vibrio species, V. alginolyticus and V. anguillarum, and marine heterotrophic, chromogenic bac­teria in aquatic microcosms were investigated. The ultimate goal of this project was to evaluate the feasibility of ex­ ploiting competitive interactions as a means to biologically control growth of the pathogenic marine bacteria, V. alginolyticus and V. anguillarum. In the majority of ex­periments (14/16), if chromogenic species were allowed to develop stable populations before a Vibrio spp. was intro­duced into a …

Vertical Distribution Of Phytoplankton Populations Along The Northeastern Continental Shelf Margin Of The United States, Bruce Burwell Wagoner

Biological Sciences Theses & Dissertations

A study of phytoplankton vertical distribution at six stations along the northeast continental shelf of the United States was conducted in April 1984.

A total of 168 taxa were identified from nine phylogenetic groups collected at depths up to 150 m. Highest cell concentrations and cell volumes were in the upper 30 m. Greatest cell concentrations were produced by diatoms and a pico-nanoplankton component, with cell volumes mainly the product of diatoms and dinoflagellates. A high degree of variability was observed between phylogenetic groups within each station, but less variability was noted for phylogenetic categories at different stations.

Little difference …

Seasonal Phytoplankton Assemblages In The Nansemond River, Virginia, Cindy Eleanor Shomers

Biological Sciences Theses & Dissertations

A monthly phytoplankton study was conducted on the Nansemond River from November 1984 to October 1985. Light microscopy was utilized to characterize the resident populations, their cell concentrations and to provide a general comparison to other regional studies of river systems considered more polluted. The results divided the flora into two major categories. The first group was a pico-nanoplankton component composed of Cyanobacteria and Chlorophycean cells 1-10 um in diameter. The second group was a microplankton assemblage of Bacillariophyceae, Dinophyceae, Cryptophyceae, Chlorophyceae, Cyanobacteria and Euglenophyceae. The pico-nanoplankton had a unimodal abundance pattern with peak concentrations occurring in spring. The microplankton …

A Simple Solid-Phase Electrophoretic Procedure For The Separation Of Plasmid Dna, Linda Ann Simurra

Biological Sciences Theses & Dissertations

A method was developed for extraction of plasmid DNA from bacterial cells embedded in agarose blocks. Cell - containing blocks were treated with various lysing reagents and inserted into the wells of an agarose gel. Upon electrophoresis the plasmid DNA migrated out of the embedding block and into the gel leaving intact chromosomal DNA in the well. This method was tested with various organisms and found to be effective for plasmid isolation. In comparison to "traditional" procedures, this new method is less tedious since chemical separation of plasmids is not required prior to electrophoresis. Also, a higher yield of plasmid …

An Annual Study Of Phytoplankton Composition And Associated Environmental Conditions Of Lake Trashmore, Virginia Beach, Virginia, Seba B. Sheavly

Biological Sciences Theses & Dissertations

A 12 month study of Lake Trashmore was conducted on phytoplankton composition, inorganic nutrients and their seasonal associations. The dominant phytoplankton groups observed were diatoms, chlorophyceans and cyanobacteria. Phytoplankton assemblage patterns were coupled with pH, temperature, dissolved oxygen, nitrites and silicates. Diatoms dominated during periods of high nutrient concentrations, cooler temperatures and an unstable water column. Cyanobacteria forms dominated during periods of warmer temperatures, higher pH and decreased nitrogen and dissolved oxygen concentrations. A seasonal community shift occurred from cyanobacterial dominance to chlorophycean dominance when pH levels decreased. The lake is eutrophic based on indices of chlorophyll a concentrations, transparency …