A key component of colonization, biofilm formation, and protection of the opportunistic human pathogen Pseudomonas aeruginosa is the biosynthesis of the exopolysaccharide Psl. Composed of a ...pentameric repeating unit of mannose, glucose, and rhamnose, the biosynthesis of Psl is proposed to occur via a Wzx/Wzy-dependent mechanism. Previous genetic studies have shown that the putative glycoside hydrolase PslG is essential for Psl biosynthesis. To understand the function of this protein, the apo-structure of the periplasmic domain of PslG (PslG(31–442)) and its complex with mannose were determined to 2.0 and 1.9 Å resolution, respectively. Despite a domain architecture and positioning of catalytic residues similar to those of other family 39 glycoside hydrolases, PslG(31–442) exhibits a unique 32-Å-long active site groove that is distinct from other structurally characterized family members. PslG formed a complex with two mannose monosaccharides in this groove, consistent with binding data obtained from intrinsic tryptophan fluorescence. PslG was able to catalyze the hydrolysis of surface-associated Psl, and this activity was abolished in a E165Q/E276Q double catalytic variant. Surprisingly, P. aeruginosa variants with these chromosomal mutations as well as a pslG deletion mutant were still capable of forming Psl biofilms. However, overexpression of PslG in a pslG deletion background impaired biofilm formation and resulted in less surface-associated Psl, suggesting that regulation of this enzyme is important during polysaccharide biosynthesis.
Background: PslG has been implicated in Psl biosynthesis.
Results: The structure of PslG was determined. PslG was shown to hydrolyze Psl, and in vitro and in vivo functional studies were performed.
Conclusion: PslG has a distinct endo-acting-like active site groove. Deletion of pslG did not impact Psl synthesis or biofilm formation.
Significance: Regulation of PslG is important for Psl biosynthesis and biofilm formation.
We evaluated the efficacy and cardiovascular safety of roxadustat versus placebo by analyzing data pooled from three phase 3 studies of roxadustat in patients with non-dialysis-dependent CKD and ...CKD-related anemia.
In the three phase 3, double-blind studies of roxadustat versus placebo evaluating the treatment of CKD-related anemia in patients not requiring dialysis, the primary efficacy end point was mean change from baseline in hemoglobin averaged over weeks 28-52, regardless of rescue therapy. The primary cardiovascular safety end point was a composite measure of major adverse cardiovascular events (MACE; all-cause mortality, myocardial infarction, stroke). MACE plus (MACE+; MACE plus unstable angina and heart failure requiring hospitalization) and all-cause mortality were key secondary safety end points. These safety end points were adjudicated.
A total of 4277 patients with non-dialysis-dependent CKD were randomized (roxadustat,
=2391; placebo,
=1886). Baseline characteristics were comparable between groups; the mean (SD) hemoglobin was 9.1 (0.7) g/dl and mean eGFR was 20 (12) ml/min per 1.73 m
. Patients treated with roxadustat versus those treated with placebo showed a mean change from baseline in hemoglobin averaged over weeks 28-52, regardless of rescue therapy, of 1.9 versus 0.2 g/dl, a treatment difference of 1.7 (95% confidence interval 95% CI, 1.7 to 1.8). Roxadustat reduced the need for red blood cell transfusion in the first 52 weeks versus placebo (6.1 versus 20.4 per 100 patient-exposure years, respectively; hazard ratio HR, 0.26; 95% CI, 0.21 to 0.32). There were no increased risks of MACE (HR, 1.10; 95% CI, 0.96 to 1.27), MACE+ (HR, 1.07; 95% CI, 0.94 to 1.21), all-cause mortality (HR, 1.08; 95% CI, 0.93 to 1.26), or individual MACE+ components in patients treated with roxadustat versus those treated with placebo.
Roxadustat was more effective than placebo at increasing hemoglobin in patients with non-dialysis-dependent CKD and anemia, while decreasing transfusion rate and being noninferior to placebo with respect to risk of MACE.
A Study of FG-4592 for the Treatment of Anemia in Chronic Kidney Disease Patients Not Receiving Dialysis, NCT01750190; Roxadustat in the Treatment of Anemia in Chronic Kidney Disease Patients Not Requiring Dialysis (ALPS), NCT01887600; Safety and Efficacy Study of Roxadustat to Treat Anemia in Patients With Chronic Kidney Disease (CKD), Not on Dialysis, NCT02174627.
Bacillus subtilis is intensively studied as a model organism for the development of bacterial biofilms or pellicles. A key component is currently undefined exopolysaccharides produced from proteins ...encoded by genes within the eps locus. Within this locus are four genes, epsHIJK, known to be essential for pellicle formation. We show they encode proteins synthesizing the broadly expressed microbial carbohydrate poly-N-acetylglucosamine (PNAG). PNAG was present in both pellicle and planktonic wild-type B. subtilis cells and in strains with deletions in the epsA–G and -L–O genes but not in strains deleted for epsH–K. Cloning of the B. subtilis epsH–K genes into Escherichia coli with in-frame deletions in the PNAG biosynthetic genes pgaA–D, respectively, restored PNAG production in E. coli. Cloning the entire B. subtilis epsHIJK locus into pga-deleted E. coli, Klebsiella pneumoniae, or alginate-negative Pseudomonas aeruginosa restored or conferred PNAG production. Bioinformatic and structural predictions of the EpsHIJK proteins suggest EpsH and EpsJ are glycosyltransferases (GT) with a GT-A fold; EpsI is a GT with a GT-B fold, and EpsK is an α-helical membrane transporter. B. subtilis, E. coli, and pga-deleted E. coli carrying the epsHIJK genes on a plasmid were all susceptible to opsonic killing by antibodies to PNAG. The immunochemical and genetic data identify the genes and proteins used by B. subtilis to produce PNAG as a significant carbohydrate factor essential for pellicle formation.
Bacillus subtilis is a model organism for analyzing bacterial biofilms, but the carbohydrate components are undescribed.
Genes in the epsHIJK locus needed for biofilm formation encode proteins synthesizing the conserved bacterial polysaccharide poly-N-acetylglucosamine (PNAG).
PNAG is a major carbohydrate component of B. subtilis biofilms.
PNAG production is essential for formation of B. subtilis biofilms.
Clinical trials in nephrology often use composite end points comprising clinical events, such as onset of ESKD and initiation of kidney function replacement therapy, along with a sustained large ( ...e.g. , ≥50%) decrease in GFR. Such events typically occur late in the disease course, resulting in large trials in which most participants do not contribute clinical events. In addition, components of the end point are considered of equal importance; however, their clinical significance varies. For example, kidney function replacement therapy initiation is likely to be clinically more meaningful than GFR decline of ≥50%. By contrast, hierarchical composite end points (HCEs) combine multiple outcomes and prioritize each patient's most clinically relevant outcome for inclusion in analysis. In this review, we consider the use of HCEs in clinical trials of CKD progression, emphasizing the potential to combine dichotomous clinical events such as those typically used in CKD progression trials, with the continuous variable of GFR over time, while ranking all components according to clinical significance. We consider maraca plots to visualize overall treatment effects and the contributions of individual components, discuss the application of win odds in kidney HCE trials, and review general design considerations for clinical trials for CKD progression with kidney HCE as an efficacy end point.
Neutralizing antibodies (nAbs) produced from infection or vaccination play an important role in acquired immunity. Determining virus-specific nAb titers is a useful tool for measuring aquired ...immunity in an individual. The standard methods to do so rely on titrating serum samples against live virus and monitoring viral infection in cultured cells which requires high biosafety level containment. The surrogate virus neutralization test (sVNT) reduces the biohazards and it is suitable for designing rapid test device in a lateral flow assay (LFA) format. Here, we introduce the fabrication and development of a unique paper-based LFA device for determining the level of SARS-CoV-2 nAb in a sample with a semiquantitative direct colorimetric readout. A LFA-based gradient assay design was used to facilitate the sVNT, where the spike glycoprotein receptor binding domain (RBD) and angiotensin-converting enzyme 2 (ACE2) stand in as proxies for viruses and cells, respectively. The gradient assay employed multiple test dots of ACE2 spotted in increasing concentration along the sample flow path and gold nanoparticle-conjugated RBD for readout. In this way, the number of developed spots is inversely proportional to the concentration of nAbs present in the sample. The assay was tested with both standard solutions of nAb as well as human serum samples. We have demonstrated that the device can effectively provide semiquantitative test results of nAbs by direct instrument-free colorimetric detection.
Quinine can cause diverse and severe immune-mediated adverse reactions, including thrombotic microangiopathy (TMA). Our objective was to describe the presenting features and long-term outcomes of ...patients with quinine-induced TMA.
A case series of 19 patients with quinine-induced TMA treated with plasma exchange.
Patients with quinine-induced TMA initially suspected of having thrombotic thrombocytopenic purpura (TTP) were identified among patients enrolled in the Oklahoma TTP−Hemolytic Uremic Syndrome Registry.
The clinical course of the initial episode and morbidity and mortality following recovery.
The diagnosis of quinine-induced TMA was confirmed by documentation of quinine-dependent antibodies reactive with platelets or neutrophils and/or by previous quinine-associated systemic symptoms. Clinical data from the initial episode and long-term follow-up were described, focusing on kidney function.
19 of the 509 patients enrolled in the registry in 1989 to 2015 had quinine-induced TMA. 18 patients had quinine-dependent antibodies reactive with platelets and/or neutrophils (1 patient died before testing); 8 patients had a history of quinine-associated systemic symptoms. All patients were white; 18 were women. Quinine exposure was in pill form for 18 patients and as tonic water for 1. All patients had microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. All were initially misdiagnosed as having TTP or hemolytic uremic syndrome, and adverse reactions to quinine were not initially suspected. 1 patient died before treatment began; 17 of the 18 surviving patients required dialysis. 14 patients developed chronic kidney disease, 3 of whom developed end-stage renal disease. 8 patients died.
Patients for whom plasma exchange was not requested were not identified.
Quinine-induced TMA causes severe acute kidney injury that commonly results in chronic kidney disease.
Further understanding of adverse clinical event rates in patients with chronic kidney disease (CKD) is required for improved quality of care. This study described baseline characteristics, adverse ...clinical event rates, and mortality risk in patients with CKD, accounting for CKD stage and dialysis status.
This retrospective, noninterventional cohort study included data from adults (aged ≥ 18 years) with two consecutive estimated glomerular filtration rates of < 60 ml/min/1.73 m
, recorded ≥ 3 months apart, from the UK Clinical Practice Research Datalink of electronic health records obtained between January 1, 2004, and December 31, 2017. Select adverse clinical events, associated with CKD and difficult to quantify in randomized trials, were assessed; defined by Read codes and International Classification of Diseases, Tenth Revision codes. Clinical event rates were assessed by dialysis status (dialysis-dependent DD, incident dialysis-dependent IDD, or non-dialysis-dependent NDD), dialysis modality (hemodialysis HD or peritoneal dialysis PD), baseline NDD-CKD stage (3a-5), and observation period.
Overall, 310,953 patients with CKD were included. Comorbidities were more common in patients receiving dialysis than in NDD-CKD, and increased with advancing CKD stage. Rates of adverse clinical events, particularly hyperkalemia and infection/sepsis, also increased with advancing CKD stage and were higher in patients on HD versus PD. Mortality risk during follow-up (1-5-year range) was lowest in patients with stage 3a NDD-CKD (2.0-18.5%) and highest in patients with IDD-CKD (26.3-58.4%).
These findings highlight the need to monitor patients with CKD for comorbidities and complications, as well as signs or symptoms of clinical adverse events.
The O-acetylation of polysaccharides is a common modification used by pathogenic organisms to protect against external forces. Pseudomonas aeruginosa secretes the anionic, O-acetylated ...exopolysaccharide alginate during chronic infection in the lungs of cystic fibrosis patients to form the major constituent of a protective biofilm matrix. Four proteins have been implicated in the O-acetylation of alginate, AlgIJF and AlgX. To probe the biological function of AlgJ, we determined its structure to 1.83 Å resolution. AlgJ is a SGNH hydrolase-like protein, which while structurally similar to the N-terminal domain of AlgX exhibits a distinctly different electrostatic surface potential. Consistent with other SGNH hydrolases, we identified a conserved catalytic triad composed of D190, H192 and S288 and demonstrated that AlgJ exhibits acetylesterase activity in vitro. Residues in the AlgJ signature motifs were found to form an extensive network of interactions that are critical for O-acetylation of alginate in vivo. Using two different electrospray ionization mass spectrometry (ESI-MS) assays we compared the abilities of AlgJ and AlgX to bind and acetylate alginate. Binding studies using defined length polymannuronic acid revealed that AlgJ exhibits either weak or no detectable polymer binding while AlgX binds polymannuronic acid specifically in a length-dependent manner. Additionally, AlgX was capable of utilizing the surrogate acetyl-donor 4-nitrophenyl acetate to catalyze the O-acetylation of polymannuronic acid. Our results, combined with previously published in vivo data, suggest that the annotated O-acetyltransferases AlgJ and AlgX have separate and distinct roles in O-acetylation. Our refined model for alginate acetylation places AlgX as the terminal acetlytransferase and provides a rationale for the variability in the number of proteins required for polysaccharide O-acetylation.
The NleGs are the largest family of type 3 secreted effectors in attaching and effacing (A/E) pathogens, such as enterohemorrhagic Escherichia coli (EHEC), enteropathogenic E. coli, and Citrobacter ...rodentium. NleG effectors contain a conserved C-terminal U-box domain acting as a ubiquitin protein ligase and target host proteins via a variable N-terminal portion. The specific roles of these effectors during infection remain uncertain. Here, we demonstrate that the three NleG effectors-NleG1
, NleG7
, and NleG8
-encoded by C. rodentium DBS100 play distinct roles during infection in mice. Using individual
knockout strains, we show that NleG7
contributes to bacterial survival during enteric infection while NleG1
promotes the expression of diarrheal symptoms and NleG8
contributes to accelerated lethality in susceptible mice. Furthermore, the NleG8
effector contains a C-terminal PDZ domain binding motif that enables interaction with the host protein GOPC. Both the PDZ domain binding motif and the ability to engage with host ubiquitination machinery via the intact U-box domain proved to be necessary for NleG8
function, contributing to the observed phenotype during infection. We also establish that the PTZ binding motif in the EHEC NleG8 (NleG8
) effector, which shares 60% identity with NleG8
, is engaged in interactions with human GOPC. The crystal structure of the NleG8
C-terminal peptide in complex with the GOPC PDZ domain, determined to 1.85 Å, revealed a conserved interaction mode similar to that observed between GOPC and eukaryotic PDZ domain binding motifs. Despite these common features,
does not complement the Δ
phenotype during infection, revealing functional diversification between these NleG effectors.
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