Renal failure and leukocytosis are predictors of a complicated course of clostridium difficile infection if measured on day of diagnosis

Nonsevere Clostridium difficile infection (CDI) and severe CDI, which carries a higher risk than nonsevere CDI for treatment failure and CDI recurrence, are difficult to distinguish at the time of diagnosis. To investigate the prognostic value of 3 markers of severe CDI suggested by recent guidelines (fever, leukocytosis, and renal failure), we used the database of 2 randomized controlled trials, which contained information for 1105 patients with CDI. Leukocytosis (risk ratio [RR], 2.29; 95% confidence interval [CI], 1.63–3.21) and renal failure (RR, 2.52; 95% CI, 1.82–3.50) were associated with treatment failure. Fever, although associated with treatment failure (RR, 2.45; 95% CI, 1.07–5.61), was rare. Renal failure was the only significant predictor of recurrence (RR, 1.45; 95% CI, 1.05–2.02). Different timing of measurements of leukocyte count and serum creatinine level around the CDI diagnosis led to a different severity classification in many cases. In conclusion, both leukocytosis and renal failure are useful predictors, although timing of measurement is important

HLA-DM Mediates Epitope Selection by a “Compare-Exchange” Mechanism when a Potential Peptide Pool Is Available

BACKGROUND: HLA-DM (DM) mediates exchange of peptides bound to MHC class II (MHCII) during the epitope selection process. Although DM has been shown to have two activities, peptide release and MHC class II refolding, a clear characterization of the mechanism by which DM facilitates peptide exchange has remained elusive. METHODOLOGY/PRINCIPAL FINDINGS: We have previously demonstrated that peptide binding to and dissociation from MHCII in the absence of DM are cooperative processes, likely related to conformational changes in the peptide-MHCII complex. Here we show that DM promotes peptide release by a non-cooperative process, whereas it enhances cooperative folding of the exchange peptide. Through electron paramagnetic resonance (EPR) and fluorescence polarization (FP) we show that DM releases prebound peptide very poorly in the absence of a candidate peptide for the exchange process. The affinity and concentration of the candidate peptide are also important for the release of the prebound peptide. Increased fluorescence energy transfer between the prebound and exchange peptides in the presence of DM is evidence for a tetramolecular complex which resolves in favor of the peptide that has superior folding properties. CONCLUSION/SIGNIFICANCE: This study shows that both the peptide releasing activity on loaded MHCII and the facilitating of MHCII binding by a candidate exchange peptide are integral to DM mediated epitope selection. The exchange process is initiated only in the presence of candidate peptides, avoiding possible release of a prebound peptide and loss of a potential epitope. In a tetramolecular transitional complex, the candidate peptides are checked for their ability to replace the pre-bound peptide with a geometry that allows the rebinding of the original peptide. Thus, DM promotes a "compare-exchange" sorting algorithm on an available peptide pool. Such a "third party"-mediated mechanism may be generally applicable for diverse ligand recognition in other biological systems

Molecular modeling of temperature dependence of solubility parameters for amorphous polymers

A molecular modeling strategy is proposed to describe the temperature (T) dependence of solubility parameter (δ) for the amorphous polymers which exhibit glass-rubber transition behavior. The commercial forcefield “COMPASS” is used to support the atomistic simulations of the polymer. The temperature dependence behavior of δ for the polymer is modeled by running molecular dynamics (MD) simulation at temperatures ranging from 250 up to 650 K. Comparing the MD predicted δ value at 298 K and the glass transition temperature (Tg) of the polymer determined from δ–T curve with the experimental value confirm the accuracy of our method. The MD modeled relationship between δ and T agrees well with the previous theoretical works. We also observe the specific volume (v), cohesive energy (Ucoh), cohesive energy density (ECED) and δ shows a similar temperature dependence characteristics and a drastic change around the Tg. Meanwhile, the applications of δ and its temperature dependence property are addressed and discussed

Model for the Peptide-Free Conformation of Class II MHC Proteins

Background: Major histocompatibility complex proteins are believed to undergo significant conformational changes concomitant with peptide binding, but structural characterization of these changes has remained elusive. Methodology/Principal Findings: Here we use molecular dynamics simulations and experimental probes of protein conformation to investigate the peptide-free state of class II MHC proteins. Upon computational removal of the bound peptide from HLA-DR1-peptide complex, the a50-59 region folded into the P1-P4 region of the peptide binding site, adopting the same conformation as a bound peptide. Strikingly, the structure of the hydrophobic P1 pocket is maintained by engagement of the side chain of Phe a54. In addition, conserved hydrogen bonds observed in crystal structures between the peptide backbone and numerous MHC side chains are maintained between the a51-55 region and the rest of the molecule. The model for the peptide-free conformation was evaluated using conformationally-sensitive antibody and superantigen probes predicted to show no change, moderate change, or dramatic changes in their interaction with peptide-free DR1 and peptide-loaded DR1. The binding observed for these probes is in agreement with the movements predicted by the model. Conclusion/Significance: This work presents a molecular model for peptide-free class II MHC proteins that can help to interpret the conformational changes known to occur within the protein during peptide binding and release, and ca

Evaluation of Aloe vera juice as a substrate for Enterococcus faecium

Fermented plant material beverages stand out from fermented food in general, since their consumption presents no risk of intolerance and allergies associated with dairy food. Aloe vera has been used to varied medical purposes due to their bioactive compounds. Lactic acid bacteria, generally used in fermented beverages, are known also for their potential health and nutritional benefits. This study aimed to evaluate Aloe vera juice grown in Mexico as a substrate for Enterococus faecium isolated from breastmilk. To obtain the juice, Aloe vera gel was treated enzymatically with cellulase. The juice was inoculated with E. faecuim at 37ºC and initial pH 4.7 ± 0.2. Biomass growth and pH were evaluated along the fermentation. Fermentation was also run with Aloe vera juice supplemented with 20 g/L of glucose. Glucose consumption and organic acids produced were analyzed by HPLC, and Total phenols were determined by Folin- Ciocalteu colorimetric method. Results obtained with E. faecium were compared with fermentations run with a commercial Lactococus Lactis strain. Glucose from the Aloe vera juice was consumed in 24 h by the E. faecium, with a production of 2.25 g/L of lactic acid. In the juice supplemented with glucose, E. faecium did not consumed all the glucose up to 60 h fermentation, and produced 7.3 g/L of lactic acid. The pH droped to 3 units in both treatments. There was a significant difference between the total phenols determined for both fermentations. A total of 192.50±0.04 mg GAE/L was found for the fermentation run with the Aloe vera juice and 196.53±0.06 mg GAE/L for fermentation with addition of glucose to the juice. For fermentations run with the commercial strain of L. Lactis, a higher amount of total phenols was determined, 222.30±0.05mg GAE/L and 226.90±0.02 mg GAE/L for treatment without and with supplementation of glucose. The carbon source did not influence the production of total phenols, but it did influence the production of lactic acid. Other acids of interest were also produced by both bacteria such as succinate, format, acetate, propionate, and iso- butyrate. Aloe vera showed to be suitable for the growth of the probiotic E. faecium bacteria, boosting bioactive metabolites in the obtained juice, which after process optimization may result in a new functional beverage.info:eu-repo/semantics/publishedVersio

Production of a new functional Aloe vera juice with Enterococcus faecium

info:eu-repo/semantics/publishedVersio