bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fullerene Derivatives Strongly Inhibit HIV-1 Replication by Affecting Virus Maturation without Impairing Protease Activity
Authors: Martinez Zachary S. , Castro Edison , Seong Chang-Soo , Cerón Maira R. , Echegoyen Luis , Llano Manuel 
Published: July 2016

ABSTRACT

Three compounds (1, 2, and 3) previously reported to inhibit HIV-1 replication and/or
in vitro
activity of reverse transcriptase were studied, but only fullerene derivatives 1 and 2 showed strong antiviral activity on the replication of HIV-1 in human CD4
+
T cells. However, these compounds did not inhibit infection by single-round infection vesicular stomatitis virus glycoprotein G (VSV-G)-pseudotyped viruses, indicating no effect on the early steps of the viral life cycle. In contrast, analysis of single-round infection VSV-G-pseudotyped HIV-1 produced in the presence of compound 1 or 2 showed a complete lack of infectivity in human CD4
+
T cells, suggesting that the late stages of the HIV-1 life cycle were affected. Quantification of virion-associated viral RNA and p24 indicates that RNA packaging and viral production were unremarkable in these viruses. However, Gag and Gag-Pol processing was affected, as evidenced by immunoblot analysis with an anti-p24 antibody and the measurement of virion-associated reverse transcriptase activity, ratifying the effect of the fullerene derivatives on virion maturation of the HIV-1 life cycle. Surprisingly, fullerenes 1 and 2 did not inhibit HIV-1 protease in an
in vitro
assay at the doses that potently blocked viral infectivity, suggesting a protease-independent mechanism of action. Highlighting the potential therapeutic relevance of fullerene derivatives, these compounds block infection by HIV-1 resistant to protease and maturation inhibitors.
Evaluation of Vancomycin Exposures Associated with Elevations in Novel Urinary Biomarkers of Acute Kidney Injury in Vancomycin-Treated Rats
Authors: Rhodes Nathaniel J. , Prozialeck Walter C. , Lodise Thomas P. , Venkatesan Natarajan , O'Donnell J. Nicholas , Pais Gwendolyn , Cluff Cameron , Lamar Peter C. , Neely Michael N. , Gulati Anil , Scheetz Marc H. 
Published: July 2016

ABSTRACTVancomycin has been associated with acute kidney injury (AKI). However, the pharmacokinetic/toxicodynamic relationship for AKI is not well defined. Allometrically scaled vancomycin exposures were used to assess the relationship between vancomycin exposure and AKI. Male Sprague-Dawley rats received clinical-grade vancomycin in normal saline (NS) as intraperitoneal (i.p.) injections for 24- to 72-h durations with doses ranging 0 to 200 mg/kg of body weight divided once or twice daily. Urine was collected over the protocol's final 24 h. Renal histopathology was qualitatively scored. Urinary biomarkers (e.g., cystatin C, clusterin, kidney injury molecule 1 [KIM-1], osteopontin, lipocalin 2/neutrophil gelatinase-associated lipocalin 2) were assayed using a Luminex xMAP system. Plasma vancomycin concentrations were assayed by high-performance liquid chromatography with UV detection. A three-compartment vancomycin pharmacokinetic model was fit to the data with the Pmetrics package for R. The exposure-response in the first 24 h was evaluated using Spearman's nonparametric correlation coefficient (rs) values for the area under the concentration-time curve during the first 24 h (AUC0–24), the maximum concentration in plasma during the first 24 h (Cmax0–24), and the lowest (minimum) concentration in plasma after the dose closest to 24 h (Cmin0–24). A total of 52 rats received vancomycin (n= 42) or NS (n= 10). The strongest exposure-response correlations were observed between AUC0–24and Cmax0–24and urinary AKI biomarkers. Exposure-response correlations (rsvalues) for AUC0–24, Cmax0–24, and Cmin0–24were 0.37, 0.39, and 0.22, respectively, for clusterin; 0.42, 0.45, and 0.26, respectively, for KIM-1; and 0.52, 0.55, and 0.42, respectively, for osteopontin. However, no differences in histopathological scores were observed. Optimal sampling times after administration of the i.p. dose were 0.25, 0.75, 2.75, and 8 h for the once-daily dosing schemes and 0.25, 1.25, 14.5, and 17.25 h for the twice-daily dosing schemes. Our observations suggest that AUC0–24or Cmax0–24correlates with increases in urinary AKI biomarkers.
Population Pharmacokinetic Modeling of Tribendimidine Metabolites in Opisthorchis viverrini-Infected Adults
Authors: Vanobberghen Fiona , Penny Melissa A. , Duthaler Urs , Odermatt Peter , Sayasone Somphou , Keiser Jennifer , Tarning Joel 
Published: July 2016

ABSTRACT

There is a pressing need for alternative treatments against the liver fluke
Opisthorchis viverrini
. Oral tribendimidine is a promising candidate, but its population pharmacokinetic properties are unknown. Two phase IIa trials were conducted in Laos in
O. viverrini
-infected adults receiving single oral doses of 25 to 600 mg tribendimidine administered as different formulations in each study (study 1 used 200-mg tablets, and study 2 used 50-mg tablets). Venous whole blood, plasma, and capillary dried blood spots were sampled frequently from 68 adults, and concentrations of the tribendimidine metabolites dADT (deacetylated amidantel) and adADT (acetylated dADT) were measured. Population pharmacokinetics were assessed by using nonlinear mixed-effects modeling. The relationship between drug exposure and cure (assessed at 21 days posttreatment) was evaluated by using univariable logistic regression. A six-transit compartment absorption model with a one-disposition compartment for each metabolite described the data well. Compared to the 50-mg formulation (study 2), the 200-mg formulation (study 1) had a 40.1% higher mean transit absorption time, a 113% higher dADT volume of distribution, and a 364% higher adADT volume of distribution. Each 10-year increase in age was associated with a 12.7% lower dADT clearance and a 21.2% lower adADT clearance. The highest cure rates (≥55%) were observed with doses of ≥100 mg. Higher dADT, but not adADT, peak concentrations and exposures were associated with cure (
P
= 0.004 and 0.003, respectively). For the first time, population pharmacokinetics of tribendimidine have been described. Known differences in the 200-mg versus 50-mg formulations were captured by covariate modeling. Further studies are needed to validate the structural model and confirm covariate relationships. (This study has been registered with the ISRCTN Registry under no. ISRCTN96948551.)
Targeting Multiple Aminoacyl-tRNA Synthetases Overcomes the Resistance Liabilities Associated with Antibacterial Inhibitors Acting on a Single Such Enzyme
Authors: Randall Christopher P. , Rasina Dace , Jirgensons Aigars , O'Neill Alex J. 
Published: July 2016

ABSTRACT
Bacterial aminoacyl-tRNA synthetases (aaRSs) represent promising antibacterial drug targets. Unfortunately, the aaRS inhibitors that have to date reached clinical trials are subject to rapid resistance development through mutation, a phenomenon that limits their potential clinical utility. Here, we confirm the intuitively correct idea that simultaneous targeting of two different aaRS enzymes prevents the emergence of spontaneous bacterial resistance at high frequency, a finding that supports the development of multitargeted anti-aaRS therapies.
Emergence and Plasmid Analysis of Klebsiella pneumoniae KP01 Carrying
bla
GES-5
from Guangzhou, China
Authors: Chen Ding-Qiang , Wu Ai-Wu , Yang Ling , Su Dan-Hong , Lin Yong-ping , Hu Yan-Wei , Zheng Lei , Wang Qian 
Published: July 2016

ABSTRACT

Klebsiella pneumoniae
strain KP01 carrying
bla
GES-5
was identified from a patient in Guangzhou, China. High-throughput sequencing assigned
bla
GES-5
to a 28.5-kb nonconjugative plasmid, pGES-GZ. A 13-kb plasmid backbone sequence on pGES-GZ was found to share high sequence identities with plasmids from Gram-negative nonfermenters. A novel class 1 integron carrying a gene cassette array of
orf28-orf28-bla
GES-5
was identified on pGES-GZ, within which
orf28
encoded a hypothetical protein possibly correlated to fosfomycin resistance.
De Novo
Characterization of Genes That Contribute to High-Level Ciprofloxacin Resistance in Escherichia coli
Authors: Tran Thu , Ran Qinghong , Ostrer Lev , Khodursky Arkady 
Published: July 2016

ABSTRACT

Sensitization of resistant bacteria to existing antibiotics depends on the identification of candidate targets whose activities contribute to resistance. Using a transposon insertion library in an
Escherichia coli
mutant that was 2,000 times less susceptible to ciprofloxacin than its parent and the relative fitness scores, we identified 19 genes that contributed to the acquired ciprofloxacin resistance and mapped the shortest genetic path that increased the antibiotic susceptibility of the resistant bacteria back to a near wild-type level.
Efficacy Projection of Obiltoxaximab for Treatment of Inhalational Anthrax across a Range of Disease Severity
Authors: Yamamoto Brent J. , Shadiack Annette M. , Carpenter Sarah , Sanford Daniel , Henning Lisa N. , O'Connor Edward , Gonzales Nestor , Mondick John , French Jonathan , Stark Gregory V. , Fisher Alan C. , Casey Leslie S. , Serbina Natalya V. 
Published: July 2016

ABSTRACT

Inhalational anthrax has high mortality even with antibiotic treatment, and antitoxins are now recommended as an adjunct to standard antimicrobial regimens. The efficacy of obiltoxaximab, a monoclonal antibody against anthrax protective antigen (PA), was examined in multiple studies conducted in two animal models of inhalational anthrax. A single intravenous bolus of 1 to 32 mg/kg of body weight obiltoxaximab or placebo was administered to New Zealand White rabbits (two studies) and cynomolgus macaques (4 studies) at disease onset (significant body temperature increase or detection of serum PA) following lethal challenge with aerosolized
Bacillus anthracis
spores. The primary endpoint was survival. The relationship between efficacy and disease severity, defined by pretreatment bacteremia and toxemia levels, was explored. In rabbits, single doses of 1 to 16 mg/kg obiltoxaximab led to 17 to 93% survival. In two studies, survival following 16 mg/kg obiltoxaximab was 93% and 62% compared to 0% and 0% for placebo (
P
= 0.0010 and
P
= 0.0013, respectively). Across four macaque studies, survival was 6.3% to 78.6% following 4 to 32 mg/kg obiltoxaximab. In two macaque studies, 16 mg/kg obiltoxaximab reduced toxemia and led to survival rates of 31%, 35%, and 47% versus 0%, 0%, and 6.3% with placebo (
P
= 0.0085,
P
= 0.0053,
P
= 0.0068). Pretreatment bacteremia and toxemia levels inversely correlated with survival. Overall, obiltoxaximab monotherapy neutralized PA and increased survival across the range of disease severity, indicating clinical benefit of toxin neutralization with obiltoxaximab in both early and late stages of inhalational anthrax.
The HMW1 and HMW2 Adhesins Enhance the Ability of Nontypeable Haemophilus influenzae To Colonize the Upper Respiratory Tract of Rhesus Macaques
Authors: Rempe Katherine A. , Porsch Eric A. , Wilson Jolaine M. , St. Geme Joseph W. 
Published: July 2016

ABSTRACTNontypeableHaemophilus influenzae(NTHi) initiates infection by colonizing the upper respiratory tract and is a common cause of localized respiratory tract disease. Previous work has established that the NTHi HMW1 and HMW2 proteins are potent adhesins that mediate efficientin vitroadherence to cultured human respiratory epithelial cells. In this study, we used a rhesus macaque model to assess the contributions of HMW1 and HMW2 toin vivocolonization. In experiments involving inoculation of individual isogenic derivatives of NTHi strain 12, the parent strain expressing both HMW1 and HMW2 and the mutant strains expressing either HMW1 or HMW2 were able to colonize more frequently than the double mutant strain lacking HMW1 and HMW2. In competition experiments, the parent strain efficiently outcompeted the double mutant lacking HMW1 and HMW2. Colonization with strains expressing HMW2 resulted in development of antibody against HMW2 in a number of the animals, demonstrating that colonization can stimulate an antibody response. In conclusion, we have established that the HMW1 and HMW2 adhesins play a major role in facilitating colonization of the upper respiratory tract of rhesus macaques, in some cases associated with stimulation of an immune response.
Cooperation of PD-1 and LAG-3 Contributes to T-Cell Exhaustion in Anaplasma marginale-Infected Cattle
Authors: Okagawa Tomohiro , Konnai Satoru , Deringer James R. , Ueti Massaro W. , Scoles Glen A. , Murata Shiro , Ohashi Kazuhiko , Brown Wendy C. 
Published: July 2016

ABSTRACT

The CD4
+
T-cell response is central for the control of
Anaplasma marginale
infection in cattle. However, the infection induces a functional exhaustion of antigen-specific CD4
+
T cells in cattle immunized with
A. marginale
outer membrane proteins or purified outer membranes (OMs), which presumably facilitates the persistence of this rickettsia. In the present study, we hypothesize that T-cell exhaustion following infection is induced by the upregulation of immunoinhibitory receptors on T cells, such as programmed death 1 (PD-1) and lymphocyte activation gene 3 (LAG-3). OM-specific T-cell responses and the kinetics of PD-1-positive (PD-1
+
) LAG-3
+
exhausted T cells were monitored in
A. marginale
-challenged cattle previously immunized with OMs. Consistent with data from previous studies, OM-specific proliferation of peripheral blood mononuclear cells (PBMCs) and interferon gamma (IFN-γ) production were significantly suppressed in challenged animals by 5 weeks postinfection (wpi). In addition, bacteremia and anemia also peaked in these animals at 5 wpi. Flow cytometric analysis revealed that the percentage of PD-1
+
LAG-3
+
T cells in the CD4
+
, CD8
+
, and γδ T-cell populations gradually increased and also peaked at 5 wpi. A large increase in the percentage of LAG-3
+
γδ T cells was also observed. Importantly,
in vitro
, the combined blockade of the PD-1 and LAG-3 pathways partially restored OM-specific PBMC proliferation and IFN-γ production at 5 wpi. Taken together, these results indicate that coexpression of PD-1 and LAG-3 on T cells contributes to the rapid exhaustion of
A. marginale
-specific T cells following infection and that these immunoinhibitory receptors regulate T-cell responses during bovine anaplasmosis.
Disease and Carrier Isolates of Neisseria meningitidis Cause G
1
Cell Cycle Arrest in Human Epithelial Cells
Authors: von Papen Michael , Oosthuysen Wilhelm F. , Becam Jérôme , Claus Heike , Schubert-Unkmeir Alexandra 
Published: July 2016

ABSTRACT

Microbial pathogens have developed several mechanisms to modulate and interfere with host cell cycle progression. In this study, we analyzed the effect of the human pathogen
Neisseria meningitidis
on the cell cycle of epithelial cells. Two pathogenic isolates, as well as two carrier isolates, were tested for their ability to adhere to and invade into the epithelial cell lines Detroit 562 and NP69 and to modulate the cell cycle. We found that all isolates adhered equally well to both Detroit 562 and NP69 cells, whereas the carrier isolates were significantly less invasive. Using propidium iodide staining and 5-ethynyl-2′-deoxyuridine pulse-labeling, we provide evidence that meningococcal infection arrested cells in the G
1
phase of the cell cycle at 24 h postinfection. In parallel, a significant decrease of cells in the S phase was observed. Interestingly, G
1
-phase arrest was only induced after infection with live bacteria but not with heat-killed bacteria. By Western blotting we demonstrate that bacterial infection resulted in a decreased protein level of the cell cycle regulator cyclin D1, whereas cyclin E expression levels were increased. Furthermore,
N. meningitidis
infection induced an accumulation of the cyclin-dependent kinase inhibitor (CKI) p21
WAF1/CIP1
that was accompanied by a redistribution of this CKI to the cell nucleus, as shown by immunofluorescence analysis. Moreover, the p27
CIP1
CKI was redistributed and showed punctate foci in infected cells. In summary, we present data that
N. meningitidis
can interfere with the processes of host cell cycle regulation.
Beyond Tryptophan Synthase: Identification of Genes That Contribute to Chlamydia trachomatis Survival during Gamma Interferon-Induced Persistence and Reactivation
Authors: Muramatsu Matthew K. , Brothwell Julie A. , Stein Barry D. , Putman Timothy E. , Rockey Daniel D. , Nelson David E. 
Published: July 2016

ABSTRACT

Chlamydia trachomatis
can enter a viable but nonculturable state
in vitro
termed persistence. A common feature of
C. trachomatis
persistence models is that reticulate bodies fail to divide and make few infectious progeny until the persistence-inducing stressor is removed. One model of persistence that has relevance to human disease involves tryptophan limitation mediated by the host enzyme indoleamine 2,3-dioxygenase, which converts
l
-tryptophan to
N
-formylkynurenine. Genital
C. trachomatis
strains can counter tryptophan limitation because they encode a tryptophan-synthesizing enzyme. Tryptophan synthase is the only enzyme that has been confirmed to play a role in interferon gamma (IFN-γ)-induced persistence, although profound changes in chlamydial physiology and gene expression occur in the presence of persistence-inducing stressors. Thus, we screened a population of mutagenized
C. trachomatis
strains for mutants that failed to reactivate from IFN-γ-induced persistence. Six mutants were identified, and the mutations linked to the persistence phenotype in three of these were successfully mapped. One mutant had a missense mutation in tryptophan synthase; however, this mutant behaved differently from previously described synthase null mutants. Two hypothetical genes of unknown function,
ctl0225
and
ctl0694
, were also identified and may be involved in amino acid transport and DNA damage repair, respectively. Our results indicate that
C. trachomatis
utilizes functionally diverse genes to mediate survival during and reactivation from persistence in HeLa cells.
Electron Acceptors Induce Secretion of Enterotoxigenic Escherichia coli Heat-Labile Enterotoxin under Anaerobic Conditions through Promotion of GspD Assembly
Authors: Lu Xi , Fu Enqing , Xie Yonghong , Jin Faguang 
Published: July 2016

ABSTRACT

Heat-labile enterotoxin (LT), the major virulence factor of enterotoxigenic
Escherichia coli
(ETEC), can lead to severe diarrhea and promotes ETEC adherence to intestinal epithelial cells. Most previous
in vitro
studies focused on ETEC pathogenesis were conducted under aerobic conditions, which do not reflect the real situation of ETEC infection because the intestine is anoxic. In this study, the expression and secretion of LT under anaerobic or microaerobic conditions were determined; LT was not efficiently secreted into the supernatant under anaerobic or microaerobic conditions unless terminal electron acceptors (trimethylamine
N
-oxide dihydrate [TMAO] or nitrate) were available. Furthermore, we found that the restoration effects of TMAO and nitrate on LT secretion could be inhibited by amytal or Δ
torCAD
and Δ
narG
E. coli
strains, indicating that LT secretion under anaerobic conditions was dependent on the integrity of the respiratory chain. At the same time, electron acceptors increase the ATP level of ETEC, but this increase was not the main reason for LT secretion. Subsequently, the relationship between the integrity of the respiratory chain and the function of the type II secretion system was determined. The GspD protein, the secretin of ETEC, was assembled under anaerobic conditions and was accompanied by LT secretion when TMAO or nitrate was added. Our data also demonstrated that TMAO and nitrate could not induce the GspD assembly and LT secretion in Δ
torCAD
and Δ
narG
strains, respectively. Moreover, GspD assembly under anaerobic conditions was assisted by the pilot protein YghG.
Chimeric Coupling Proteins Mediate Transfer of Heterologous Type IV Effectors through the Escherichia coli pKM101-Encoded Conjugation Machine
Authors: Whitaker Neal , Berry Trista M. , Rosenthal Nathan , Gordon Jay E. , Gonzalez-Rivera Christian , Sheehan Kathy B. , Truchan Hilary K. , VieBrock Lauren , Newton Irene L. G. , Carlyon Jason A. , Christie Peter J. 
Published: July 2016

ABSTRACT

Bacterial type IV secretion systems (T4SSs) are composed of two major subfamilies, conjugation machines dedicated to DNA transfer and effector translocators for protein transfer. We show here that the
Escherichia coli
pKM101-encoded conjugation system, coupled with chimeric substrate receptors, can be repurposed for transfer of heterologous effector proteins. The chimeric receptors were composed of the N-terminal transmembrane domain of pKM101-encoded TraJ fused to soluble domains of VirD4 homologs functioning in
Agrobacterium tumefaciens
,
Anaplasma phagocytophilum
, or
Wolbachia pipientis
. A chimeric receptor assembled from
A. tumefaciens
VirD4 (VirD4
At
) mediated transfer of a MOBQ plasmid (pML122) and
A. tumefaciens
effector proteins (VirE2, VirE3, and VirF) through the pKM101 transfer channel. Equivalent chimeric receptors assembled from the rickettsial VirD4 homologs similarly supported the transfer of known or candidate effectors from rickettsial species. These findings establish a proof of principle for use of the dedicated pKM101 conjugation channel, coupled with chimeric substrate receptors, to screen for translocation competency of protein effectors from recalcitrant species. Many T4SS receptors carry sequence-variable C-terminal domains (CTDs) with unknown function. While VirD4
At
and the TraJ/VirD4
At
chimera with their CTDs deleted supported pML122 transfer at wild-type levels, ΔCTD variants supported transfer of protein substrates at strongly diminished or elevated levels. We were unable to detect binding of VirD4
At
's CTD to the VirE2 effector, although other VirD4
At
domains bound this substrate
in vitro
. We propose that CTDs evolved to govern the dynamics of substrate presentation to the T4SS either through transient substrate contacts or by controlling substrate access to other receptor domains.

IMPORTANCE
Bacterial type IV secretion systems (T4SSs) display striking versatility in their capacity to translocate DNA and protein substrates to prokaryotic and eukaryotic target cells. A hexameric ATPase, the type IV coupling protein (T4CP), functions as a substrate receptor for nearly all T4SSs. Here, we report that chimeric T4CPs mediate transfer of effector proteins through the
Escherichia coli
pKM101-encoded conjugation system. Studies with these repurposed conjugation systems established a role for acidic C-terminal domains of T4CPs in regulating substrate translocation. Our findings advance a mechanistic understanding of T4CP receptor activity and, further, support a model in which T4SS channels function as passive conduits for any DNA or protein substrates that successfully engage with and pass through the T4CP specificity checkpoint.