Bioluminescent Imaging of Trypanosoma brucei Shows Preferential Testis Dissemination Which May Hamper Drug Efficacy in Sleeping Sickness

Monitoring Trypanosoma spread using real-time imaging in vivo provides a fast method to evaluate parasite distribution especially in immunoprivileged locations. Here, we generated monomorphic and pleomorphic recombinant Trypanosoma brucei expressing the Renilla luciferase. In vitro luciferase activity measurements confirmed the uptake of the coelenterazine substrate by live parasites and light emission. We further validated the use of Renilla luciferase-tagged trypanosomes for real-time bioluminescent in vivo analysis. Interestingly, a preferential testis tropism was observed with both the monomorphic and pleomorphic recombinants. This is of importance when considering trypanocidal drug development, since parasites might be protected from many drugs by the blood-testis barrier. This hypothesis was supported by our final study of the efficacy of treatment with trypanocidal drugs in T. brucei-infected mice. We showed that parasites located in the testis, as compared to those located in the abdominal cavity, were not readily cleared by the drugs

A Novel Substrate-Based HIV-1 Protease Inhibitor Drug Resistance Mechanism

BACKGROUND: HIV protease inhibitor (PI) therapy results in the rapid selection of drug resistant viral variants harbouring one or two substitutions in the viral protease. To combat PI resistance development, two approaches have been developed. The first is to increase the level of PI in the plasma of the patient, and the second is to develop novel PI with high potency against the known PI-resistant HIV protease variants. Both approaches share the requirement for a considerable increase in the number of protease mutations to lead to clinical resistance, thereby increasing the genetic barrier. We investigated whether HIV could yet again find a way to become less susceptible to these novel inhibitors. METHODS AND FINDINGS: We have performed in vitro selection experiments using a novel PI with an increased genetic barrier (RO033-4649) and demonstrated selection of three viruses 4- to 8-fold resistant to all PI compared to wild type. These PI-resistant viruses did not have a single substitution in the viral protease. Full genomic sequencing revealed the presence of NC/p1 cleavage site substitutions in the viral Gag polyprotein (K436E and/or I437T/V) in all three resistant viruses. These changes, when introduced in a reference strain, conferred PI resistance. The mechanism leading to PI resistance is enhancement of the processing efficiency of the altered substrate by wild-type protease. Analysis of genotypic and phenotypic resistance profiles of 28,000 clinical isolates demonstrated the presence of these NC/p1 cleavage site mutations in some clinical samples (codon 431 substitutions in 13%, codon 436 substitutions in 8%, and codon 437 substitutions in 10%). Moreover, these cleavage site substitutions were highly significantly associated with reduced susceptibility to PI in clinical isolates lacking primary protease mutations. Furthermore, we used data from a clinical trial (NARVAL, ANRS 088) to demonstrate that these NC/p1 cleavage site changes are associated with virological failure during PI therapy. CONCLUSIONS: HIV can use an alternative mechanism to become resistant to PI by changing the substrate instead of the protease. Further studies are required to determine to what extent cleavage site mutations may explain virological failure during PI therapy

Giving ecological meaning to satellite-derived fire severity metrics across North American forests

Satellite-derived spectral indices such as the relativized burn ratio (RBR) allow fire severity maps to be produced in a relatively straightforward manner across multiple fires and broad spatial extents. These indices often have strong relationships with field-based measurements of fire severity, thereby justifying their widespread use in management and science. However, satellite-derived spectral indices have been criticized because their non-standardized units render them difficult to interpret relative to on-the-ground fire effects. In this study, we built a Random Forest model describing a field-based measure of fire severity, the composite burn index (CBI), as a function of multiple spectral indices, a variable representing spatial variability in climate, and latitude. CBI data primarily representing forested vegetation from 263 fires (8075 plots) across the United States and Canada were used to build the model. Overall, the model performed well, with a cross-validated R2 of 0.72, though there was spatial variability in model performance. The model we produced allows for the direct mapping of CBI, which is more interpretable compared to spectral indices. Moreover, because the model and all spectral explanatory variables were produced in Google Earth Engine, predicting and mapping of CBI can realistically be undertaken on hundreds to thousands of fires. We provide all necessary code to execute the model and produce maps of CBI in Earth Engine. This study and its products will be extremely useful to managers and scientists in North America who wish to map fire effects over large landscapes or regions

Advancing global & regional reanalyses

This report outlines the structure of and summarizes the recommendations made at the 5th International Conference on Reanalysis (ICR5), attended by 259 participants from 37 countries, in Rome (Italy), on 13-17 November 2017. It first summarizes the conference structure. Then, the key recommendations of ICR5 are given for the five main conference topics: production; observations (data rescue and preparation); data assimilation methods; quality assurance of reanalysis; and applications in science, services, and policymaking. Lastly, five high-level recommendations are proposed to managing agencies on how best to advance the field of reanalyses, which serves tens of thousands of users, via enhanced research, development, and operations

Protein Phosphatase-1α Interacts with and Dephosphorylates Polycystin-1

Polycystin signaling is likely to be regulated by phosphorylation. While a number of potential protein kinases and their target phosphorylation sites on polycystin-1 have been identified, the corresponding phosphatases have not been extensively studied. We have now determined that polycystin-1 is a regulatory subunit for protein phosphatase-1α (PP1α). Sequence analysis has revealed the presence of a highly conserved PP1-interaction motif in the cytosolic, C-terminal tail of polycystin-1; and we have shown that transfected PP1α specifically co-immunoprecipitates with a polycystin-1 C-tail construct. To determine whether PP1α dephosphorylates polycystin-1, a PKA-phosphorylated GST-polycystin-1 fusion protein was shown to be dephosphorylated by PP1α but not by PP2B (calcineurin). Mutations within the PP1-binding motif of polycystin-1, including an autosomal dominant polycystic kidney disease (ADPKD)-associated mutation, significantly reduced PP1α-mediated dephosphorylation of polycystin-1. The results suggest that polycystin-1 forms a holoenzyme complex with PP1α via a conserved PP1-binding motif within the polycystin-1 C-tail, and that PKA-phosphorylated polycystin-1 serves as a substrate for the holoenzyme

Visual Acuity Outcomes in Patients Receiving Frequent Treatment of Neovascular Age-Related Macular Degeneration in Clinical Practice

Purpose: This work evaluates dosing frequency with intravitreal antivascular endothelial growth factor (anti-VEGF) agents over 2 years and visual acuity (VA) outcomes in neovascular age-related macular degeneration (nAMD). Methods: This retrospective analysis assesses electronic medical record data (Vestrum Health treatment and outcomes database) of newly diagnosed nAMD in patients who were initiated on intravitreal anti-VEGF treatment at US clinical sites. Eyes were divided into 2 injection frequency subcohorts (≤ 6 or > 6 injections/y); treatment frequency and change in mean VA (Early Treatment Diabetic Retinopathy Study letters) were evaluated. Results: Overall, 8127 of 213 824 eyes met inclusion criteria in year 1 and 4968 in year 2. During year 1, 77% of the eyes received more than 6 injections (n = 6287), the majority of which received injections at the same frequency during year 2. Mean VA gain from baseline at year 1 was lower in the ≤ 6 than > 6 injections/y subcohort (2.2 vs 6.5, P < .001). Decrease in mean VA from the end of year 1 to year 2 was significantly greater for eyes administered 6 or fewer injections in year 2 than those that received more frequent injections, irrespective of the frequency of injections in the first year. Conclusions: In routine clinical practice, most eyes with nAMD that completed at least 1 year of follow-up were treated with more than 6 injections of anti-VEGF agents during the first year of treatment, resulting in better VA gains than eyes treated less frequently during the same period

Evaluation of Patients Receiving Intravitreal Antivascular Endothelial Growth Factor for Diabetic Macular Edema in Clinical Practice in the United States

Purpose: We assessed the effect of treatment frequency with intravitreal antivascular endothelial growth factor (anti-VEGF) agents on visual acuity (VA) in diabetic macular edema (DME). Methods: This retrospective analysis assessed electronic medical records of eyes newly diagnosed with DME and treated with an anti-VEGF agent at US clinics using the Vestrum Health (Naperville, Illinois) treatment and outcomes database. Eyes were divided into 2 injection frequency subcohorts (≤ 6 vs > 6 injections/y); treatment frequency and change in mean VA (Early Treatment Diabetic Retinopathy Study letters) were evaluated. Results: Among 155 240 eyes assessed, 3028 met inclusion criteria for analysis in year 1 and 1292 in year 2. During year 1 of treatment, 57% (n = 1725) received > 6 injections; most continued to receive the same injection frequency during year 2. Mean VA gain from baseline at year 1 was lower in the ≤ 6 than in the > 6 injections/year subcohort (3.7 vs 8.0 letters, respectively; P 6 injections in year 1, mean VA loss was significantly greater for eyes receiving less-frequent dosing in year 2 than in those maintained on > 6 injections. Conclusions: More than 50% of eyes with DME in routine clinical practice that completed at least 1 year of follow-up received > 6 injections of an anti-VEGF agent during the first year, resulting in better VA gains than eyes treated less frequently