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Lyme disease is the most prevalent arthropod-borne infectious disease in the United States, with more than 30,000 new cases reported each year to the CDC. Borrelia burgdorferi, the causative agent of Lyme disease, is transmitted to humans following the bite of infected ticks. B. burgdorferi is a host-adapted pathogen and undergoes rapid metabolic and virulence adaptation while transitioning from the tick vector to a vertebrate host. Recently, our lab described the role of a regulator called Borrelia host adaptation regulator (BadR) in modulating adaptive gene expression specific to the tick vector or the vertebrate host. Deletion of badR in an infectious strain of B. burgdorferi resulted in several genes that were upregulated or downregulated. One such ORF is BB0019, which is downregulated in the badR mutant suggesting that it could play a role in the survival of the pathogen in ticks. We hypothesize that BB0019 is essential for colonization and transmission of B. burgdorferi from infected ticks. To test this hypothesis, we will purify recombinant BB0019 and generate antisera specific to this protein. We will delete this gene from an infectious strain of B. burgdorferi and analyze BB0019-deficient strain’s ability to infect ticks and mouse models of Lyme disease.
We anticipate that absence of BB0019 will result in a strain incapable of survival or transmission from ticks. These observations will help to identify molecular targets that can be used to block the transmission of B. burgdorferi from ticks and thereby develop strategies to reduce the incidence of Lyme disease in humans.
IDENTIFICATION OF YERSINIA GENES THAT INFLUENCE ACTIVATION OF HOST NFKB TRIGGERED BY THE
TYPE III SECRETION SYSTEMNatalia Herrera, Hector Ramirez, Laura Kwuan, Victoria Auerbuch.
University of California, Santa Cruz, Santa Cruz, CA.
Yersinia pseudotuberculosis is a human pathogen that uses a type III secretion system (T3SS) to deliver 6 effector proteins inside target host cells, disarming host innate immune defenses. The Y. pseudotuberculosis T3SS lacking the 6 known T3SS effector proteins retains the ability to activate the proinflammatory transcription factor NFkB in mammalian cells. We hypothesize that detection of unknown bacterial cargo injected by the T3SS activates NFkB in host cells. Since NFkB is a major regulator of the innate immune response during infection, this may be important for the ability of Yersinia to cause disease. To identify Yersinia genes required for T3SS-dependent NFkB activation, we constructed a library of 4,400 Y. pseudotuberculosis transposon mutants lacking the 6 known T3SS effector proteins.
We infect HEK293T NFkB-luciferase reporter cells with Y. pseudotuberculosis mutants and measure bioluminescence corresponding to NFkB activity. We have screened approximately 2,350 mutants and identified 18 mutants triggering aberrant levels of host NFkB. One of the genes found in our genetic screen, SufI, may affect expression or delivery of unknown NFkB-activating T3SS cargo. SufI is thought to localize to the septal ring and is known to be a twin arginine translocation (TAT) system substrate. An additonal gene identified through our genetic screen is TatB, an integral component of the TAT secretion system. The Y. pseudotuberculosis TAT secretion system was previously shown to be important for virulence, yet has not been linked to the T3SS. We are currently investigating a possible relationship between Tat secretion of SufI and T3SS-induced host NFkB activation.
Medicine, Charlottesville, VA.
The human immunodeficiency virus type 1 (HIV-1) is the most common type of the lentivirus. This infectious agent is the leading cause of the development of AIDS, an incurable disease that targets cells within the human immune system. As a result, HIV-1 is actively studied in hopes of deriving viable treatments and vaccines against the AIDS epidemic. The structure of HIV-1 generally consists of two copies of viral RNA enclosed in a capsid surrounded by a lipid membrane, where the HIV envelope glycoprotein anchors. HIV-1 envelope glycoprotein is composed of exterior and transmembrane glycoproteins gp120 and gp41 respectively. They are present on the viral surface and mediate virus infection. In addition, as the sole viral component on the virion surface, the glycoproteins serve as potential targets for HIV-1-neutralizing antibodies. In this experiment, we are studying glycosylation of gp120 and its relation to the neutralization efficiency of VRC01 antibody, a broad HIV-1-neutralizing antibody. The methodologies used in this experiment include cell culture of JC53 cell lines, preparation of pseudovirus containing luciferase and envelope glycoproteins from the prevalent HIV-1 ADA strain (SRLV), TCID50 assay, and antibody neutralization assay with fixed amounts of infectious SRLV and VRC01 antibodies. We expect that the glycosylation switch on HIV-1 ADA gp120 will affect VRC01 antibody neutralization efficiency. Although there have been studies analyzing neutralization of HIV-1 by different antibodies, this project is the first to observe the difference in VRC01 neutralization efficiency related to the glycosylation switch on gp120.
MIF DEFICIENCY ENHANCES THE EFFICACY OF GLUCOCORTICOID TREATMENT IN EXPERIMENTAL
AUTOIMMUNE MYOCARDITIS AND AMELIORATES THE PROGRESSION TO DILATED CARDIOMYOPATHYBraxton Jamison II, Rebecca A. Sosa, Thomas G. Forsthuber.
University of Texas at San Antonio, San Antonio, TX.
Myocarditis, an inflammatory disease of the myocardium, is a major cause of sudden death and dilated cardiomyopathy (DCM). Persistent damage to the myocardium is mediated by autoreactive T lymphocytes and proinflammatory cytokines. Acute inflammation can be suppressed by glucocorticoids (GCs) in patients with autoimmune inflammatory processes; however, treatment cannot stop progression to DCM. Macrophage migration inhibitory factor (MIF) is a unique regulatory mediator that is induced by GCs and can, in turn, counterregulate their immunosuppressive effects. MIF also triggers arrest and chemotaxis of T cells through CXCR4. In this study, dexamethasone (Dex) treatment was investigated in early and late stage experimental autoimmune myocarditis (EAM) in MIF knockout (MIF-/-) Balb/c and wild-type (Wt) mice. EAM and DCM severity were determined histopathologically using hematoxylin and eosin and Masson’s trichrome staining. The nature of cardiac infiltration and CXCR4 expression were analyzed using immunofluorescence (IF) staining. We found for the first time that Wt Dextreated mice recover from EAM after peak of disease but progress to DCM with chronic fibrosis, whereas MIF-/- Dextreated mice are highly resistant to both EAM and DCM. IF staining demonstrated the absence of local inflammatory lesions and CXCR4 expression in MIF-/- Dex-treated mice, showing that CXCR4-mediated T cell recruitment to the heart is inhibited in these mice. Our results indicate that MIF antagonizes the efficacy of GCs in EAM and DCM and implicates MIF inhibition in combination with GC treatment as a potential therapeutic strategy for myocarditis as well as the prevention of progression to DCM.
INVESTIGATING THE MICROBES OF SUBSURFACE MINERAL ENVIRONMENTSMatthew Medina1, Diana E. Northup1, Michael N. Spilde2.
University of New Mexico, Albuquerque, NM, 2Institute of Meteoritics, University of New Mexico, Albuquerque, NM.
1 The discovery of lava caves on Mars and lunar terrains has prompted the study of analogous environments on Earth to enhance our ability to detect life on extraterrestrial bodies. Such environments are the lava caves that contain secondary mineral deposits that appear nonbiological but reveal diverse microbial communities on examination. We hypothesize that secondary mineral deposits in lava caves contain a considerable number of microbial communities that can be investigated for multiple biosignatures. Our biosignature investigations of these geological phenomena involve scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The mineral deposits investigated for this study are obtained from lava caves that occur in New Mexico, Mauna Loa, Hawai’i,
113 UNDERGRADUATE POSTER ABSTRACTS
and the Azores. Preliminary SEM analysis revealed several iron-rich and carbonate deposits that contain putative microorganisms: filamentous, coccoid, and bacillus morphologies present in biofilms that produce an EDX signal indicating high carbon content. One Hawaiian sample from Arsia Cave suggests possible biodegradation of an ironoxide substrate, where putative rod-shaped cells appear in biofilm and appear to be associated with a degraded surface of the substrate. Future investigations include culture-independent studies of the microbial communities observed in these mineral-biological deposits and sequence-based studies along with further investigation of secondary mineral deposits with SEM/EDX. Investigating these microbes that masquerade as minerals and the biosignatures associated with them can help in life-detection efforts on extraterrestrial bodies and expand our knowledge of the microbial communities of oligotrophic caves on Earth.
ANALYSIS OF ANTI-CLOSTRIDIUM DIFFICILE ACTIVITY OF PAIRED ANTIBIOTIC COMBINATIONSEmmanuel Fordjour, Kieu Doan, Julian Hurdle.
University of Texas at Arlington, Arlington, TX.
Clostridium difficile is an anaerobic intestinal bacterium that causes severe, and at times fatal, diarrhea especially among elderly patients. The annual death toll for Clostridium difficile infection (CDI) in the United States alone is over 14,000. The emergence of the hyper-virulent NAP1 strain of C. difficile causing multiple relapses of C. difficileassociated diarrhea has prompted research for alternative treatment options. This project investigates whether combinations of different anti-difficile antibiotics such as novobiocin, vancomycin, berberine chloride, metronidazole, and daptomycin could have synergistic or antagonistic effects against C. difficile. We have assessed the minimum inhibitory concentrations (MICs) of 11 antimicrobials singly and in paired combinations against 10 C. difficile clinical isolates. Based on these MICs, we have determined fractional inhibitory concentrations (FICs) and consequently, the synergistic or antagonistic properties of these antimicrobial combinations. Preliminary studies have identified novobiocin-daptomycin and metronidazole-daptomycin combinations as partially synergistic (0.5 ≤ FIC ≤ 0.75) and vancomycin-daptomycin and vancomycin-berberine chloride combinations as antagonistic (FIC 2.0). Of fundamental interest in this study are the molecular pathways that could be simultaneously altered to kill C. difficile. This work will provide further insight into mutualistic biochemical interactions of anti-difficile combinations. Once such synergistic combinations are identified, future research will examine their effects on sporulation and toxin production to reduce disease recurrence and severity respectively.
HIGH-THROUGHPUT COMPOUND SCREENING TO IDENTIFY NOVEL INHIBITORS OF H5N1 INFLUENZA-AENTRY Mairead O’Connor-Maleney, Emily Rumschlag-Booms, Velid Seferovic.
Northeastern Illinois University, Chicago, IL.
Influenza-A viruses have RNA-based genomes that incur high rates of mutation due to a lack of a proof reading mechanism in its RNA polymerase. Due to these high mutation rates, the influenza virus can quickly acquire resistance to currently available vaccines and prophylactic therapeutics. As a result, it is imperative to develop novel inhibitors against drug resistant and newly emerging strains of influenza. Our research project is to screen a small library of drug-like compounds against H5N1 influenza using a high-throughput screening platform. To screen the compounds, A549 human lung epithelial cells were infected with H5N1 pseudovirus carrying a luciferase reporter gene together with each purified compound. Luciferase activity was measured 48 hours postinfection as an indirect measure of viral entry. Compounds that decreased luciferase activity and were not cytotoxic to target cells were chosen as lead entry inhibitors. We predict that the compounds will target either the influenza hemagglutinin (HA) glycoprotein on the surface of the virus or its receptor, sialic acid, which is found on the host cell surface. If the compounds target HA, then the inhibitors will have a direct neutralizing effect on influenza viral entry. However, if the compounds target host cell surface molecules, then these inhibitors may be useful as a universal entry inhibitor, targeting several subtypes of influenza.
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Biological Sciences SAT-571
ANTIBACTERIAL PROPERTIES OF SYMPHORICARPOS ALBUSJashwin Sagoo, Myriah Stitt, Christine Case.
Skyline College, San Bruno, CA.
Worldwide, microbial infectious diseases continue to be one of the leading causes of disease and death, which is exacerbated by widespread antibiotic resistance. Plants have been used for centuries by traditional healers.
These plants are logical places to search for new antimicrobials because of their proven ability to treat infections.
Symphoricarpos albus is one such plant, having been used to treat skin wounds in Native American, traditional medicine. The purpose of our work is to determine whether extracts of Symphoricarpos albus inhibit bacterial growth.
Aqueous, ethanolic, methanolic, and acetonic extracts (0.40 g/mL) were made from the plant’s root, stem, leaf, and berry. Extracts were evaluated using a disk-diffusion assay against Gram-positive bacteria, Gram-negative bacteria, and Candida albicans fungus. Disks impregnated with extracting solvents were used as controls. All extracts were effective against Gram-positive bacteria (zones of inhibition = 11.9 mm ± 1.9). Extracts were not effective against Gram-negative bacteria or fungi. We are testing the extracts against methicillin-resistant Staphylococcus aureus and determining the minimal inhibitory concentration and method of action. Our results validate the traditional medicinal use of this plant and provide a potential new antibiotic to combat antibiotic-resistant bacteria.