bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Affinity, Human Antibody-Like Antibody Fragment (Single-Chain Variable Fragment) Neutralizing the Lethal Factor (LF) of
Bacillus anthracis
by Inhibiting Protective Antigen-LF Complex Formation
Authors: Pelat Thibaut , Hust Michael , Laffly Emmanuelle , Condemine Florence , Bottex Chantal , Vidal Dominique , Lefranc Marie-Paule , Dübel Stefan , Thullier Philippe 
Published: May 2007

ABSTRACT

The anthrax lethal toxin (LT) consists of two subunits, the protective antigen (PA) and the lethal factor (LF), and is essential for anthrax pathogenesis. Several recombinant antibodies directed against PA and intended for medical use have been obtained, but none against LF, despite the recommendations of anthrax experts. Here we describe an anti-LF single-chain variable fragment (scFv) that originated from an immunized macaque (
Macaca fascicularis
) and was obtained by phage display. Panning of the library of 1.8 × 10
8
clones allowed the isolation of 2LF, a high-affinity (equilibrium dissociation constant, 1.02 nM) scFv, which is highly neutralizing in the standardized in vitro assay (50% inhibitory concentration, 1.20 ± 0.06 nM) and in an in vivo assay. The scFv neutralizes anthrax LT by inhibiting the formation of the LF-PA complex. The genes encoding 2LF are very similar to those of human immunoglobulin germ line genes, sharing substantial (84.2%) identity with their most similar, germinally encoded counterparts; this feature favors medical applications. These results, and others formerly published, demonstrate that our approach can generate antibody fragments suitable for prophylaxis and therapeutics.
In Vitro Activities of 15 Antimicrobial Agents against 110 Toxigenic
Clostridium difficile
Clinical Isolates Collected from 1983 to 2004
Authors: Hecht David W. , Galang Minerva A. , Sambol Susan P. , Osmolski James R. , Johnson Stuart , Gerding Dale N. 
Published: May 2007

ABSTRACT

The incidence and severity of
Clostridium difficile
-associated disease (CDAD) is increasing, and standard treatment is not always effective. Therefore, more-effective antimicrobial agents and treatment strategies are needed. We used the agar dilution method to determine the in vitro susceptibility of the following antimicrobials against 110 toxigenic clinical isolates of
C. difficile
from 1983 to 2004, primarily from the United States: doripenem, meropenem, gatifloxacin, levofloxacin, moxifloxacin, OPT-80, ramoplanin, rifalazil, rifaximin, nitazoxanide, tizoxanide, tigecycline, vancomycin, tinidazole, and metronidazole. Included among the isolates tested were six strains of the toxinotype III, NAP1/BI/027 group implicated in recent U.S., Canadian, and European outbreaks. The most active agents in vitro were rifaximin, rifalazil, tizoxanide, nitazoxanide, and OPT-80 with MICs at which 50% of the isolates are inhibited (MIC
50
) and MIC
90
values of 0.0075 and 0.015 μg/ml, 0.0075 and 0.03 μg/ml, 0.06 and 0.125 μg/ml, 0.06 and 0.125 μg/ml, 0.125 and 0.125 μg/ml, respectively. However, for three isolates the rifalazil and rifaximin MICs were very high (MIC of >256 μg/ml). Ramoplanin, vancomycin, doripenem, and meropenem were also very active in vitro with narrow MIC
50
and MIC
90
ranges. None of the isolates were resistant to metronidazole, the only agent for which there are breakpoints, with tinidazole showing nearly identical results. These in vitro susceptibility results are encouraging and support continued evaluation of selected antimicrobials in clinical trials of treatment for CDAD.
The
Pseudomonas aeruginosa
LasB Metalloproteinase Regulates the Human Urokinase-Type Plasminogen Activator Receptor through Domain-Specific Endoproteolysis
Authors: Leduc Dominique , Beaufort Nathalie , de Bentzmann Sophie , Rousselle Jean-Claude , Namane Abdelkader , Chignard Michel , Pidard Dominique 
Published: May 2007

ABSTRACT

Pseudomonas aeruginosa
is an opportunistic pathogen in human lungs, where its secretable LasB metalloproteinase can be a virulence factor. The urokinase-type plasminogen activator receptor (uPAR) participates in pericellular proteolysis and the adherence/migration of epithelial cells and leukocytes recruited during infection and shows functional regulation by various proteinases via limited endoproteolysis occurring within its three domains (D1 to D3). We thus examined the proteolytic activity of LasB on uPAR by using recombinant uPAR as well as uPAR-expressing, human monocytic, and bronchial epithelial cell lines. Protein immunoblotting and flow immunocytometry using a panel of domain-specific anti-uPAR antibodies showed that LasB is able to cleave uPAR both within the sequence linking D1 to D2 and at the carboxy terminus of D3. Comparison of LasB-producing and LasB-deficient bacterial strains indicated that LasB is entirely responsible for the uPAR cleavage ability of
P. aeruginosa
. Based on amino-terminal protein microsequencing and mass spectrometry analysis of the cleavage of peptides mimicking the uPAR sequences targeted by LasB, cleavage sites were determined to be Ala
84
-Val
85
and Thr
86
-Tyr
87
(D1-D2) and Gln
279
-Tyr
280
(D3). Such a dual cleavage of uPAR led to the removal of amino-terminal D1, the generation of a truncated D2D3 species, and the shedding of D2D3 from cells. This proteolytic processing of uPAR was found to (i) drastically reduce the capacity of cells to bind urokinase and (ii) abrogate the interaction between uPAR and the matrix adhesive protein vitronectin. The LasB proteinase is thus endowed with a high potential for the alteration of uPAR expression and functioning on inflammatory cells during infections by
P. aeruginosa
.
Human Lung Innate Immune Response toBacillus anthracisSpore Infection
Authors: Chakrabarty Kaushik , Wu Wenxin , Booth J. Leland , Duggan Elizabeth S. , Nagle Nancy N. , Coggeshall K. Mark , Metcalf Jordan P. 
Published: May 2007

ABSTRACTBacillus anthracis, the causative agent of inhalational anthrax, enters a host through the pulmonary system before dissemination. We have previously shown that human alveolar macrophages participate in the initial innate immune response toB. anthracisspores through cell signal-mediated cytokine release. We proposed that the lung epithelia also participate in the innate immune response to this pathogen, and we have developed a human lung slice model to study this process. Exposure of our model toB. anthracis(Sterne) spores rapidly activated the mitogen-activated protein kinase signaling pathways ERK, p38, and JNK. In addition, an RNase protection assay showed induction of mRNA of several cytokines and chemokines. This finding was reflected at the translational level by protein peak increases of 3-, 25-, 9-, 34-, and 5-fold for interleukin-6 (IL-6), tumor necrosis factor alpha, IL-8, macrophage inflammatory protein 1α/β, and monocyte chemoattractant protein 1, respectively, as determined by an enzyme-linked immunosorbent assay. Inhibition of individual pathways by UO126, SP600125, and SB0203580 decreased induction of chemokines and cytokines by spores, but this depended on the pathways inhibited and the cytokines and chemokines induced. Combining all three inhibitors reduced induction of all cytokines and chemokines tested to background levels. An immunohistochemistry analysis of IL-6 and IL-8 revealed that alveolar epithelial cells and macrophages and a few interstitial cells are the source of the cytokines and chemokines. Taken together, these data showed the activation of the pulmonary epithelium in response toB. anthracisspore exposure. Thus, the lung epithelia actively participate in the innate immune response toB. anthracisinfection through cell signal-mediated elaboration of cytokines and chemokines.
Helicobacter pyloriChemotaxis Modulates Inflammation and Bacterium-Gastric Epithelium Interactions in Infected Mice
Authors: Williams Susan M. , Chen Yu-Ting , Andermann Tessa M. , Carter J. Elliot , McGee David J. , Ottemann Karen M. 
Published: May 2007

ABSTRACTThe ulcer-causing pathogenHelicobacter pyloriuses directed motility, or chemotaxis, to both colonize the stomach and promote disease development. Previous work showed that mutants lacking the TlpB chemoreceptor, one of the receptors predicted to drive chemotaxis, led to less inflammation in the gerbil stomach than did the wild type. Here we expanded these findings and examined the effects on inflammation of completely nonchemotactic mutants and mutants lacking each chemoreceptor. Of note, all mutants colonized mice to the same levels as did wild-typeH. pylori. Infection by completely nonchemotactic mutants (cheWorcheY) resulted in significantly less inflammation after both 3 and 6 months of infection. Mutants lacking either the TlpA or TlpBH. pylorichemotaxis receptors also had alterations in inflammation severity, while mutants lacking either of the other two chemoreceptors (TlpC and HylB) behaved like the wild type. Fully nonchemotactic and chemoreceptor mutants adhered to cultured gastric epithelial cells and caused cellular release of the chemokine interleukin-8 in vitro similar to the release caused by the wild type. The situation appeared to be different in the stomach. Using silver-stained histological sections, we found that nonchemotacticcheYorcheWmutants were less likely than the wild type to be intimately associated with the cells of the gastric mucosa, although there was not a strict correlation between intimate association and inflammation. Because others have shown that in vivo adherence promotes inflammation, we propose a model in whichH. pyloriuses chemotaxis to guide it to a productive interaction with the stomach epithelium.
Pasteurella multocida
Expresses Two Lipopolysaccharide Glycoforms Simultaneously, but Only a Single Form Is Required for Virulence: Identification of Two Acceptor-Specific Heptosyl I Transferases
Authors: Harper Marina , Boyce John D. , Cox Andrew D. , St. Michael Frank , Wilkie Ian W. , Blackall P. J. , Adler Ben 
Published: May 2007

ABSTRACT

Lipopolysaccharide (LPS) is a critical virulence determinant in
Pasteurella multocida
and a major antigen responsible for host protective immunity. In other mucosal pathogens, variation in LPS or lipooligosaccharide structure typically occurs in the outer core oligosaccharide regions due to phase variation.
P. multocida
elaborates a conserved oligosaccharide extension attached to two different, simultaneously expressed inner core structures, one containing a single phosphorylated 3-deoxy-
d
-manno-octulosonic acid (Kdo) residue and the other containing two Kdo residues. We demonstrate that two heptosyltransferases, HptA and HptB, add the first heptose molecule to the Kdo
1
residue and that each exclusively recognizes different acceptor molecules. HptA is specific for the glycoform containing a single, phosphorylated Kdo residue (glycoform A), while HptB is specific for the glycoform containing two Kdo residues (glycoform B). In addition, KdkA was identified as a Kdo kinase, required for phosphorylation of the first Kdo molecule. Importantly, virulence data obtained from infected chickens showed that while wild-type
P. multocida
expresses both LPS glycoforms in vivo, bacterial mutants that produced only glycoform B were fully virulent, demonstrating for the first time that expression of a single LPS form is sufficient for
P. multocida
survival in vivo. We conclude that the ability of
P. multocida
to elaborate alternative inner core LPS structures is due to the simultaneous expression of two different heptosyltransferases that add the first heptose residue to the nascent LPS molecule and to the expression of both a bifunctional Kdo transferase and a Kdo kinase, which results in the initial assembly of two inner core structures.
Biofilms Protect
Mycoplasma pulmonis
Cells from Lytic Effects of Complement and Gramicidin
Authors: Simmons Warren L. , Dybvig Kevin 
Published: May 2007

ABSTRACT

The length of the tandem repeat region of the Vsa protein of
Mycoplasma pulmonis
has previously been shown to modulate the susceptibility of mycoplasmas to killing by complement: cells that produce a short form of the Vsa protein are highly sensitive, and cells producing the long Vsa protein are resistant. In contrast to their differing susceptibilities to complement, the mycoplasmas were highly sensitive to gramicidin irrespective of the length of the Vsa protein produced. We show here that when encased within a biofilm, cells of
M. pulmonis
producing a short form of the Vsa protein were more resistant to complement and gramicidin than mycoplasmas that were dispersed. The resistance appeared to be localized to those mycoplasmas within tower structures of the biofilms. Biofilm formation may be a mechanism that protects mycoplasmas from host immunity.
Cytokines, Signaling Pathways, and Effector Molecules Required for the Control ofLeishmania(Viannia)braziliensisin Mice
Authors: Rocha F. Janaina Soares , Schleicher Ulrike , Mattner Jochen , Alber Gottfried , Bogdan Christian 
Published: May 2007

ABSTRACTCutaneous leishmaniasis is caused by protozoan parasites of the genusLeishmania. The mechanisms of pathogen control have been established primarily in the mouse model ofLeishmania majorinfection, but they might not hold true for otherLeishmaniaspecies associated with cutaneous disease. Here, we analyzed the role of cytokines, signaling components, and effector molecules in the control of New World cutaneous leishmaniasis due toL. braziliensis. UnlikeL. major,L. braziliensiscaused small, nonulcerative, and self-healing skin swelling in C57BL/6 mice, as well as BALB/c mice. In contrast to the results obtained forL. mexicana, mice deficient for interleukin-12 or its key signaling molecule, signal transducer and activator of transcription 4, rapidly succumbed to severe visceral leishmaniasis. Infection of tumor necrosis factor knockout mice withL. braziliensisled to progressive, nonhealing skin lesions with erosions and hemorrhagic ulcerations, but in contrast to the results withL. major, only 20 to 30% of the mice developed fatal visceral disease. As seen withL. major, mice with a deleted inducible nitric oxide synthase gene (iNOS−/−) were unable to containL. braziliensisin the skin, whereas the control of the parasite in the spleen remained unimpaired. Unlike what happens inL. majorinfections, NADPH oxidase had no impact on the course of disease inL. braziliensis-infected mice. These results not only define essential components of a protective immune response toL. braziliensisbut also illustrate that the requirements for the control of cutaneous leishmaniasis vary between different parasite species.
Cytolysin-Dependent Escape of the Bacterium from the Phagosome Is Required but Not Sufficient for Induction of the Th1 Immune Response againstListeria monocytogenesInfection: Distinct Role of Listeriolysin O Determined by Cytolysin Gene Replacement
Authors: Hara Hideki , Kawamura Ikuo , Nomura Takamasa , Tominaga Takanari , Tsuchiya Kohsuke , Mitsuyama Masao 
Published: May 2007

ABSTRACTListeria monocytogenesevades the antimicrobial mechanisms of macrophages by escaping from the phagosome into the cytosolic space via a unique cytolysin that targets the phagosomal membrane, listeriolysin O (LLO), encoded byhly. Gamma interferon (IFN-γ), which is known to play a pivotal role in the induction of Th1-dependent protective immunity in mice, appears to be produced, depending on the bacterial virulence factor. To determine whether the LLO molecule (the major virulence factor ofL. monocytogenes) is indispensable or the escape of bacteria from the phagosome is sufficient to induce IFN-γ production, we first constructed anhly-deleted mutant ofL. monocytogenesand then established isogenicL. monocytogenesmutants expressing LLO or ivanolysin O (ILO), encoded byilofromListeria ivanovii. LLO-expressingL. monocytogeneswas highly capable of inducing IFN-γ production andListeria-specific protective immunity, while thehly-deleted mutant was not. In contrast, the level of IFN-γ induced by ILO-expressingL. monocytogeneswas significantly lower both in vitro and in vivo, despite the ability of this strain to escape the phagosome and the intracellular multiplication at a level equivalent to that of LLO-expressingL. monocytogenes. Only a negligible level of protective immunity was induced in mice against challenge with LLO- and ILO-expressingL. monocytogenes. These results clearly show that escape of the bacterium from the phagosome is a prerequisite but is not sufficient for the IFN-γ-dependent Th1 response againstL. monocytogenes, and some distinct molecular nature of LLO is indispensable for the final induction of IFN-γ that is essentially required to generate a Th1-dependent immune response.
Recovery of cognitive and dynamic motor function following concussion
Authors: Parker Tonya M , Osternig Louis R , van Donkelaar Paul , Chou Li-Shan 
Published: May 2007

Objective:Neuropsychological testing has been advocated as an important tool of proper post-concussion management. Although these measures provide information that can be used in the decision of when to return an individual to previous levels of physical activity, they provide little data on motor performance following injury. The purpose of this investigation was to examine the relationship between measures of dynamic motor performance and neuropsychological function following concussion over the course of 28 days.Methods:Participants completed two experimental protocols: gait stability and neuropsychological testing. The gait stability protocol measured whole-body centre of mass motion as subjects walked under conditions of divided and undivided attention. Neuropsychological testing consisted of a computerised battery of tests designed to assess memory, reaction time, processing speed and concussion symptoms. Correlation coefficients were computed between all neuropsychological and gait variables and comparisons of neuropsychological and gait stability post-concussion recovery curves were assessed.Results:Dynamic motor tasks, such as walking under varying conditions of attention, are complex and demanding undertakings, which require a longer recovery time following a concussion than cognitive measures. Little statistical relationship was found between the neuropsychological and gait variables, and the recovery curves of neuropsychological and gait domains were observed to be independent.Conclusions:In order to fully examine the effects of concussion and determine the optimal time for a safe return to activity, a multi-factorial approach, including both cognitive and motor tasks, should be employed.
Male control of copulation duration in a wolf spider (Araneae, Lycosidae)
Authors: Rypstra Ann , Wilder Shawn 
Published: May 2007

While a great deal of research has examined mate choice, variation in behavior during copulation can also have important consequences for the fitness of males and females. We examined the relationships between male and female characteristics (age, size and condition) and copulation duration in the wolf spider
Hogna helluo
(Araneae, Lycosidae). In addition, we used these relationships to test if males control copulation duration. In this species, males mount the dorsal surface of females and females make no visible attempts to terminate mating. Male age was positively related to the duration of copulation. In addition, male condition was negatively related to the duration of copulation such that poor condition males mated for longer durations. If a group of outlier copulations are removed from the analysis, then male age is no longer a predictor of mating duration but male condition becomes an even stronger predictor of mating duration. Males that engaged in long copulations were more likely to be cannibalized following mating. Our data provide support for the hypothesis that males exert the primary influence on copulation duration in
H. helluo
. Older and poor condition males may engage in longer copulations to increase their paternity with the current female because they may have a lower chance of escaping postcopulatory sexual cannibalism or surviving to find another female.
Scattering of Ice Particles at Microwave Frequencies: A Physically Based Parameterization
Authors: Kim Min-Jeong , Kulie Mark S. , O’Dell Chris , Bennartz Ralf 
Published: May 2007

Abstract
This paper presents a new, purely physical approach to simulate ice-particle scattering at microwave frequencies. Temperature-dependent ice particle size distributions measured by aircraft in midlatitude frontal systems are used to represent the distribution of precipitation-sized frozen hydrometeors above the freezing level through derived radar reflectivity–snow water content (Z–M) relationships. The discrete dipole approximation is employed to calculate optical properties of selected types of idealized nonspherical ice particles (hexagonal columns, four-arm rosettes, and six-arm rosettes). Based on those assumptions, passive microwave optical properties are calculated using radar observations from Gotland Island in the Baltic Sea. These forward-simulated brightness temperatures are compared with observed data from both the Advanced Microwave Scanning Radiometer (AMSR-E) and the Advanced Microwave Sounding Unit-B (AMSU-B). Results show that the new ice scattering/microphysics model is able to generate brightness temperatures that are consistent with AMSR and AMSU-B observations of two light-winter-precipitation cases. The overall differences among the various ice-habit results at 89 GHz are generally not that expansive, whereas the AMSU-B 150-GHz comparisons show increased sensitivity to ice-particle shapes.
Giant and Ultragiant Aerosol Particle Variability over the Eastern Great Lakes Region
Authors: Lasher-Trapp Sonia , Stachnik Justin P. 
Published: May 2007

Abstract
Numerous studies have indicated the potential for giant and ultragiant aerosol particles to expedite the warm-rain process as a result of their extreme sizes. The central question regarding their importance is, Are they present in large enough numbers to influence the microphysics of the clouds significantly? Thus, quantification of these particles and their variability is paramount. New observations collected during the second Alliance Icing Research Study (AIRS II) are presented as evidence of the presence and variability of giant and ultragiant aerosol particles over a continental region—in this case, within the eastern Great Lakes region and parts of the midwestern United States and Canada during one month in winter 2003. Sources and factors contributing to the amount of these particles observed in the lower atmosphere were difficult to identify separately; future studies incorporating high-resolution weather modeling are likely needed.