bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purified Lipopolysaccharide fromFrancisella tularensisLive Vaccine Strain (LVS) Induces Protective Immunity against LVS Infection That Requires B Cells and Gamma Interferon
Authors: Dreisbach Valley C. , Cowley Siobhan , Elkins Karen L. 
Published: July 2002

ABSTRACTPrevious results have demonstrated that nonspecific protective immunity against lethalFrancisella tularensislive vaccine strain (LVS) orListeria monocytogenesinfection can be stimulated either by sublethal infection with bacteria or by treatment with bacterial DNA given 3 days before lethal challenge. Here we characterize the ability of purified lipopolysaccharide (LPS) fromF. tularensisLVS to stimulate similar early protective immunity. Treatment of mice with surprisingly small amounts of LVS LPS resulted in very strong and long-lived protection against lethal LVS challenge within 2 to 3 days. Despite this strong protective response, LPS purified fromF. tularensisLVS did not activate murine B cells for proliferation or polyclonal immunoglobulin secretion, nor did it activate murine splenocytes for secretion of interleukin-4 (IL-4), IL-6, IL-12, or gamma interferon (IFN-γ). Immunization of mice with purified LVS LPS induced a weak specific anti-LPS immunoglobulin M (IgM) response and very little IgG; however, infection of mice with LVS bacteria resulted in vigorous IgM and IgG, particularly IgG2a, anti-LPS antibody responses. Studies using various immunodeficient mouse strains, including LPS-hyporesponsive C3H/HeJ mice, μMT−(B-cell-deficient) knockout mice, and IFN-γ-deficient mice, demonstrated that the mechanism of protection does not involve recognition through theLpsngene product; nonetheless, protection was dependent on B cells as well as IFN-γ.
Antioxidant Enzyme Expression in Clinical Isolates of
Pseudomonas aeruginosa
: Identification of an Atypical Form of Manganese Superoxide Dismutase
Authors: Britigan Bradley E. , Miller Rachel A. , Hassett Daniel J. , Pfaller Michael A. , McCormick Michael L. , Rasmussen George T. 
Published: July 2002

ABSTRACT

Expression of superoxide dismutases (FeSOD and MnSOD) and catalases by laboratory strains of
Pseudomonas aeruginosa
is modulated by exogenous factors. Whether clinical isolates behave similarly and whether antioxidant enzyme expression influences
P. aeruginosa
virulence remain unclear. Fifty-seven
P. aeruginosa
blood culture isolates, plus seven pairs of blood and local-site isolates, were examined for FeSOD, MnSOD, and catalase production in vitro. Under iron-replete growth conditions FeSOD and catalase activities were maximized. MnSOD was not detected. FeSOD and catalase activity decreased under iron-limited growth conditions, whereas MnSOD activity appeared. SOD and catalase activity did not change with site of isolation or by patient. MnSOD could not be expressed by one isolate due to a missense mutation in
sodA
that produced a premature stop codon. Eleven percent of the isolates expressed a novel, rapidly migrating MnSOD that was associated with missense mutations in the normal stop codon of
sodA
. We conclude that clinical
P. aeruginosa
isolates vary little in FeSOD and catalase expression. Some strains produce a newly described MnSOD variant, whereas one is deficient in MnSOD production. The absence of MnSOD expression in a
P. aeruginosa
strain causing invasive human disease indicates that MnSOD is probably not essential for
P. aeruginosa
virulence.
Discovery, Purification, and Characterization of a Temperate Transducing Bacteriophage for
Bordetella avium
Authors: Shelton Celia B. , Crosslin David R. , Casey Jennifer L. , Ng S. , Temple Louise M. , Orndorff Paul E. 
Published: July 2002

ABSTRACT

We discovered and characterized a temperate transducing bacteriophage (Ba1) for the avian respiratory pathogen
Bordetella avium
. Ba1 was initially identified along with one other phage (Ba2) following screening of four strains of
B. avium
for lysogeny. Of the two phage, only Ba1 showed the ability to transduce via an allelic replacement mechanism and was studied further. With regard to host range, Ba1 grew on six of nine clinical isolates of
B. avium
but failed to grow on any tested strains of
Bordetella bronchiseptica
,
Bordetella hinzii
,
Bordetella pertussis
, or
Bordetella parapertussis
. Ba1 was purified by CsCl gradient centrifugation and was found to have an icosahedral head that contained a linear genome of approximately 46.5 kb (contour length) of double-stranded DNA and a contractile, sheathed tail. Ba1 readily lysogenized our laboratory
B. avium
strain (197N), and the prophage state was stable for at least 25 generations in the absence of external infection. DNA hybridization studies indicated the prophage was integrated at a preferred site on both the host and phage replicons. Ba1 transduced five distinctly different insertion mutations, suggesting that transduction was generalized. Transduction frequencies ranged from approximately 2 × 10
−7
to 1 × 10
−8
transductants/PFU depending upon the marker being transduced. UV irradiation of transducing lysates markedly improved transduction frequency and reduced the number of transductants that were lysogenized during the transduction process. Ba1 may prove to be a useful genetic tool for studying
B. avium
virulence factors.
Effects of Specific Amino Acid Substitutions on Activities of Dinitrogenase Reductase-Activating Glycohydrolase from
Rhodospirillum rubrum
Authors: Antharavally Babu S. , Poyner Russell R. , Zhang Yaoping , Roberts Gary P. , Ludden Paul W. 
Published: July 2002

ABSTRACT

Site-directed mutagenesis of the
draG
gene was used to generate altered forms of dinitrogenase reductase-activating glycohydrolase (DRAG) with D123A, H142L, H158N, D243G, and E279R substitutions. The amino acid residues H142 and E279 are not required either for the coordination to the metal center or for catalysis since the variants H142L and E279R retained both catalytic and electron paramagnetic resonance spectral properties similar to those of the wild-type enzyme. Since DRAG-H158N and DRAG-D243G variants lost their ability to bind Mn(II) and to catalyze the hydrolysis of the substrate, H158 and D243 residues could be involved in the coordination of the binuclear Mn(II) center in DRAG.
Effect of P
II
and Its Homolog GlnK on Reversible ADP-Ribosylation of Dinitrogenase Reductase by Heterologous Expression of the
Rhodospirillum rubrum
Dinitrogenase Reductase ADP-Ribosyl Transferase–Dinitrogenase Reductase-Activating Glycohydrolase Regulatory System in
Klebsiella pneumoniae
Authors: Zhang Yaoping , Pohlmann Edward L. , Halbleib Cale M. , Ludden Paul W. , Roberts Gary P. 
Published: July 2002

ABSTRACT

Reversible ADP-ribosylation of dinitrogenase reductase, catalyzed by the dinitrogenase reductase ADP-ribosyl transferase–dinitrogenase reductase-activating glycohydrolase (DRAT-DRAG) regulatory system, has been characterized in
Rhodospirillum rubrum
and other nitrogen-fixing bacteria. To investigate the mechanisms for the regulation of DRAT and DRAG activities, we studied the heterologous expression of
R. rubrum draTG
in
Klebsiella pneumoniae glnB
and
glnK
mutants. In
K. pneumoniae
wild type, the regulation of both DRAT and DRAG activity appears to be comparable to that seen in
R. rubrum
. However, the regulation of both DRAT and DRAG activities is altered in a
glnB
background. Some DRAT escapes regulation and becomes active under N-limiting conditions. The regulation of DRAG activity is also altered in a
glnB
mutant, with DRAG being inactivated more slowly in response to NH
4
+
treatment than is seen in wild type, resulting in a high residual nitrogenase activity. In a
glnK
background, the regulation of DRAT activity is similar to that seen in wild type. However, the regulation of DRAG activity is completely abolished in the
glnK
mutant; DRAG remains active even after NH
4
+
addition, so there is no loss of nitrogenase activity. The results with this heterologous expression system have implications for DRAT-DRAG regulation in
R. rubrum
.
Two “Wild-Type” Variants of
Escherichia coli
σ
70
: Context-Dependent Effects of the Identity of Amino Acid 149
Authors: Baldwin Nicole E. , McCracken Andrea , Dombroski Alicia J. 
Published: July 2002

ABSTRACT

The identity of amino acid 149 of
Escherichia coli
σ
70
has been reported variably as either arginine or aspartic acid. We show that the behavior of both a region 1.2 deletion and a single-amino-acid substitution at position 122 are greatly affected by the identity of amino acid 149.
Characteristics of
Helicobacter pylori
Infection in Jamaican Adults with Gastrointestinal Symptoms
Authors: Hisada Michie , Lee Michael G. , Hanchard Barrie , Owens Marilyn , Song Qunsheng , van Doorn Leen-Jan , Cutler Alan F. , Gold Benjamin D. 
Published: July 2002

ABSTRACT

Helicobacter pylori
infection is common in Jamaica. Describing its epidemiology in a population-based study depends largely on serology, but serologic assays have not been validated in this population. To address this issue, we examined the presence of
H. pylori
infection in 30 sequential adult patients with gastroduodenal symptoms by three biopsy-based methods (rapid urease test, histology, and culture) as well as by one research and two commercial enzyme-linked immunosorbent assays (ELISAs). A patient was considered
H. pylori
positive if the organism was detected by at least one biopsy-based method. Eighteen (60%) of the 30 patients were
H. pylori
positive by these criteria, whereas 21 (70%) were seropositive for
H. pylori
immunoglobulin G by our research ELISA. The presence of
H. pylori
infection in patients with gastric cancer and those with chronic gastritis was missed by biopsy-based methods but was detected by serologic assays. This observation indicates that serologic assays may be better suited for the detection of this infection in a population in which
H. pylori
-associated pathology is prevalent. The performance of our research ELISA in detecting biopsy-based
H. pylori
-positive cases was excellent, with a sensitivity and specificity of 100% and 75%, respectively. Molecular genotyping of the isolates revealed that the predominant
H. pylori
genotypes in this cohort of Jamaicans were

cagA
+
vacA

slb-m1, and
iceA2
. The validated serologic assay enables us to interpret epidemiologic data from population-based studies in Jamaica by comparison to those from other populations.
Comparative Quantitation of Cytomegalovirus (CMV) DNA in Solid Organ Transplant Recipients with CMV Infection by Using Two High-Throughput Automated Systems
Authors: Razonable Raymund R. , Brown Robert A. , Espy Mark J. , Rivero Antonio , Kremers Walter , Wilson Jennie , Groettum Cynthia , Smith Thomas F. , Paya Carlos V. 
Published: July 2002

ABSTRACT

Cytomegalovirus (CMV) DNA quantitation in clinical specimens is progressively becoming a cornerstone in the diagnosis and management of CMV infection in the immunocompromised host. We evaluated two automated and reproducible PCR tests, the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and the COBAS AMPLICOR CMV Monitor (Roche Diagnostics, Pleasanton, Calif.), for the detection of CMV DNA in blood samples from transplant recipients with CMV infection as determined by shell vial culture. Following a log transformation analysis, the mean CMV DNA in plasma (PL), whole blood (WB), peripheral blood leukocytes (PBL), and peripheral blood mononuclear cells (PBMC) using the LightCycler was 6.79 copies per ml, 7.23 copies per ml, 6.38 copies per 2 × 10
6
cells, and 6.27 copies per 2 × 10
6
cells, respectively. This compares to 7.86 copies per ml, 8.37 copies per ml, 7.59 copies per 2 × 10
6
cells, and 7.44 copies per 2 × 10
6
cells, respectively, using COBAS AMPLICOR CMV Monitor. While higher CMV DNA levels were observed for the various blood compartments analyzed using COBAS AMPLICOR CMV Monitor, a high degree of correlation was evident between the two automated systems (jackknife correlation
r
= PL 0.77 [95% confidence interval (CI); 0.64, 0.90], WB 0.77 [95% CI; 0.62, 0.92], PBL 0.77 [95% CI; 0.67, 0.88], and PBMC 0.81 [95% CI; 0.72, 0.89], all
P
< 0.001). Therefore, we conclude that either automated diagnostic system is accurate for CMV DNA quantitation.
Molecular Variability of the Adhesin-Encoding Gene
pvpA
among
Mycoplasma gallisepticum
Strains and Its Application in Diagnosis
Authors: Liu T. , Garcı́a M. , Levisohn S. , Yogev D. , Kleven S. H. 
Published: July 2002

ABSTRACT

Mycoplasma gallisepticum
is an important pathogen of chickens and turkeys that causes considerable economic losses to the poultry industry worldwide. The reemergence of
M. gallisepticum
outbreaks among poultry, the increased use of live
M. gallisepticum
vaccines, and the detection of
M. gallisepticum
in game and free-flying song birds has strengthened the need for molecular diagnostic and strain differentiation tests. Molecular techniques, including restriction fragment length polymorphism of genomic DNA (RFLP) and PCR-based random amplification of polymorphic DNA (RAPD), have already been utilized as powerful tools to detect intraspecies variation. However, certain intrinsic drawbacks constrain the application of these methods. The main goal of this study was to determine the feasibility of using an
M.
gallisepticum
-specific gene encoding a phase-variable putative adhesin protein (PvpA) as the target for molecular typing. This was accomplished using a
pvpA
PCR-RFLP assay. Size variations among PCR products and nucleotide divergence of the C-terminus-encoding region of the
pvpA
gene were the basis for strain differentiation. This method can be used for rapid differentiation of vaccine strains from field isolates by amplification directly from clinical samples without the need for isolation by culture. Moreover, molecular epidemiology of
M. gallisepticum
outbreaks can be performed using RFLP and/or sequence analysis of the
pvpA
gene.
Antimicrobial Surveillance of
Haemophilus influenzae
in the United States during 2000-2001 Leads to Detection of Clonal Dissemination of a β-Lactamase-Negative and Ampicillin-Resistant Strain
Authors: Karlowsky James A. , Critchley Ian A. , Blosser-Middleton Renée S. , Karginova Elena A. , Jones Mark E. , Thornsberry Clyde , Sahm Daniel F. 
Published: July 2002

ABSTRACT

A 2000-2001 U.S.
Haemophilus influenzae
surveillance study (
n
= 1,434) detected nine (0.6%) β-lactamase-negative and ampicillin-resistant (BLNAR) isolates collected from two different hospitals. The MICs of ampicillin for all nine isolates were 4 μg/ml, with results being reproducible; and all nine isolates were susceptible to amoxicillin-clavulanate, cefuroxime, cefprozil, macrolides, and fluoroquinolones. Pulsed-field gel electrophoresis of genomic DNA following
Sma
I digestion demonstrated identical patterns for each of the nine isolates, suggesting intra- and interhospital dissemination of a BLNAR clone.
Simian Immunodeficiency Virus (SIV)gagDNA-Vaccinated Rhesus Monkeys Develop Secondary Cytotoxic T-Lymphocyte Responses and Control Viral Replication after Pathogenic SIV Infection
Authors: Egan Michael A. , Charini William A. , Kuroda Marcelo J. , Schmitz Jörn E. , Racz Paul , Tenner-Racz Klara , Manson Kelledy , Wyand Michael , Lifton Michelle A. , Nickerson Christie E. , Fu Tongming , Shiver John W. , Letvin Norman L. 
Published: July 2002

ABSTRACTThe potential contribution of a plasmid DNA construct to vaccine-elicited protective immunity was explored in the simian immunodeficiency virus (SIV)/macaque model of AIDS. Making use of soluble major histocompatibility class I/peptide tetramers and peptide-specific killing assays to monitor CD8+T-lymphocyte responses to a dominant SIV Gag epitope in genetically selected rhesus monkeys, a codon-optimized SIVgagDNA vaccine construct was shown to elicit a high-frequency SIV-specific cytotoxic T-lymphocyte (CTL) response. This CTL response was demonstrable in both peripheral blood and lymph node lymphocytes. Following an intravenous challenge with the highly pathogenic viral isolate SIVsm E660, these vaccinated monkeys developed a secondary CTL response that arose with more rapid kinetics and reached a higher frequency than did the postchallenge CTL response in control plasmid-vaccinated monkeys. While peak plasma SIV RNA levels were comparable in the experimentally and control-vaccinated monkeys during the period of primary infection, thegagplasmid DNA-vaccinated monkeys demonstrated better containment of viral replication by 50 days following SIV challenge. These findings indicate that a plasmid DNA vaccine can elicit SIV-specific CTL responses in rhesus monkeys, and this vaccine-elicited immunity can facilitate the generation of secondary CTL responses and control of viral replication following a pathogenic SIV challenge. These observations suggest that plasmid DNA may prove a useful component of a human immunodeficiency virus type 1 vaccine.
Functional Characterization of the Human Immunodeficiency Virus Type 1 Genome by Genetic Footprinting
Authors: Laurent Louise Chang , Olsen Mari N. , Crowley Rachel Adams , Savilahti Harri , Brown Patrick O. 
Published: July 2002

ABSTRACT

We present a detailed and quantitative analysis of the functional characteristics of the 1,000-nucleotide segment at the 5′ end of the human immunodeficiency virus type 1 (HIV-1) RNA genome. This segment of the viral genome contains several important
cis
-acting sequences, including the TAR, polyadenylation, viral
att
site, minus-strand primer-binding site, and 5′ splice donor sequences, as well as coding sequences for the matrix protein and the N-terminal half of the capsid protein. The genetic footprinting technique was used to determine quantitatively the abilities of 134 independent insertion mutations to (i) make stable viral RNA, (ii) assemble and release viral RNA-containing viral particles, and (iii) enter host cells, complete reverse transcription, enter the nuclei of host cells, and generate proviruses in the host genome by integration. All of the mutants were constructed and analyzed en masse, greatly decreasing the labor typically involved in mutagenesis studies. The results confirmed the presence of several previously known functional features in this region of the HIV genome and provided evidence for several novel features, including newly identified
cis
-acting sequences that appeared to contribute to (i) the formation of stable viral transcripts, (ii) viral RNA packaging, and (iii) an early step in viral replication. The results also pointed to an unanticipated
trans
-acting role for the N-terminal portion of matrix in the formation of stable viral RNA transcripts. Finally, in contrast to previous reports, the results of this study suggested that detrimental mutations in the matrix and capsid proteins principally interfered with viral assembly.
Tyrosine Phosphorylation of Bovine Herpesvirus 1 Tegument Protein VP22 Correlates with the Incorporation of VP22 into Virions
Authors: Ren Xiaodi , Harms Jerome S. , Splitter Gary A. 
Published: July 2002

ABSTRACT
Tyrosine phosphorylation has been shown to play a role in the replication of several herpesviruses. In this report, we demonstrate that bovine herpesvirus 1 infection triggered tyrosine phosphorylation of proteins with molecular masses similar to those of phosphorylated viral structural proteins. One of the tyrosine-phosphorylated viral structural proteins was the tegument protein VP22. A tyrosine 38-to-phenylalanine mutation totally abolished the phosphorylation of VP22 in transfected cells. However, construction of a VP22 tyrosine 38-to-phenylalanine mutant virus demonstrated that VP22 was still phosphorylated but that the phosphorylation site may change to the C terminus rather than be in the N terminus as in wild-type VP22. In addition, the loss of VP22 tyrosine phosphorylation correlated with reduced incorporation of VP22 compared to that of envelope glycoprotein D in the mutant viruses but not with the amount of VP22 produced during virus infection. Our data suggest that tyrosine phosphorylation of VP22 plays a role in virion assembly.
Mutations within the Putative Membrane-Spanning Domain of the Simian Immunodeficiency Virus Transmembrane Glycoprotein Define the Minimal Requirements for Fusion, Incorporation, and Infectivity
Authors: West John T. , Johnston Patrick B. , Dubay Susan R. , Hunter Eric 
Published: July 2002

ABSTRACTThe membrane-spanning domain (MSD) of a number of retroviral transmembrane (TM) glycoproteins, including those from the human and simian immunodeficiency viruses (HIV and SIV), have been predicted to contain a charged arginine residue. The wild-type SIV TM glycoprotein is 354 amino acids long. The entire putative cytoplasmic domain of SIV (amino acids 193 to 354) is dispensable for virus replication in vitro, and such truncation-containing viruses are capable of reaching wild-type titers after a short delay. We show here that further truncation of eight additional amino acids to TM185 results in a protein that lacks fusogenicity but is, nevertheless, efficiently incorporated into budding virions. By analyzing a series of nonsense mutations between amino acids 193 and 185 in Env expression vectors and in the SIVmac239 proviral clone, a region of the SIV TM that contains the minimum requirement for glycoprotein-mediated cell-to-cell fusion and that for virus replication was identified. Virus entry and infectivity were evident in truncations to a minimum of 189 amino acids, whereas cell-cell fusion was observed for a protein of only 187 amino acids. Glycoprotein was efficiently incorporated into budding virions in truncations up to 185 amino acids, indicating that such proteins are membrane anchored and are transported to the cell surface. However, truncation of the TM to 180 amino acids resulted in a protein that displays a transport defect and may be retained in the endoplasmic reticulum. Based on our analyses of these mutants, an alternative model for the MSD of SIV is proposed. Our model suggests that membrane-imbedded charged residues can be neutralized by side-chain interactions with lipid polar head groups. As a consequence, the membrane-spanning region can be reduced by more than a helical turn. This new model accounts for the ability of truncations within the predicted MSD to remain membrane anchored and maintain biological activity.
Release of Virus from Lymphoid Tissue Affects Human Immunodeficiency Virus Type 1 and Hepatitis C Virus Kinetics in the Blood
Authors: Müller Viktor , Marée Athanasius F. M. , De Boer Rob J. 
Published: July 2002

ABSTRACT

Kinetic parameters of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) infections have been estimated from plasma virus levels following perturbation of the chronically infected (quasi-) steady state. We extend previous models by also considering the large pool of virus localized in the lymphoid tissue (LT) compartment. The results indicate that the fastest time scale of HIV-1 plasma load decay during therapy probably reflects the clearance rate of LT virus and not, as previously supposed, the clearance rate of virus in plasma. This resolves the discrepancy between the clearance rate estimates during therapy and those based on plasma apheresis experiments. In the extended models plasma apheresis measurements are indeed expected to reflect the plasma decay rate. We can reconcile all current HIV-1 estimates with this model when, on average, the clearance rate of virus in plasma is approximately 20 day
−1
, that of LT virus is approximately 3 day
−1
, and the death rate of virus-producing cells is approximately 0.5 day
−1
. The fast clearance in the LT compartment increases current estimates for total daily virus production. Because HCV is produced in the liver, we let virus be produced into the blood compartment of our model. The results suggest that extending current HCV models with an LT compartment is not likely to affect current estimates for kinetic parameters and virus production. Estimates for treatment efficacy might be affected, however.