Malarone treatment failure and in vitro confirmation of resistance of Plasmodium falciparum isolate from Lagos, Nigeria

We report the first in vitro and genetic confirmation of Malarone(®) (GlaxoSmithKline; atovaquone and proguanil hydrochloride) resistance in Plasmodium falciparum acquired in Africa. On presenting with malaria two weeks after returning from a 4-week visit to Lagos, Nigeria without prophylaxis, a male patient was given a standard 3-day treatment course of Malarone(®). Twenty-eight days later the parasitaemia recrudesced. Parasites were cultured from the blood and the isolate (NGATV01) was shown to be resistant to atovaquone and the antifolate pyrimethamine. The cytochrome b gene of isolate NGATV01 showed a single mutation, Tyr268Asn which has not been seen previously

Two Different, Highly Exposed, Bulged Structures for an Unusually Long Peptide Bound to Rat MHC Class I RT1-Aa

AbstractThe rat MHC class Ia molecule RT1-Aa has the unusual capacity to bind long peptides ending in arginine, such as MTF-E, a thirteen-residue, maternally transmitted minor histocompatibility antigen. The antigenic structure of MTF-E was unpredictable due to its extraordinary length and two arginines that could serve as potential anchor residues. The crystal structure of RT1-Aa-MTF-E at 2.55 Å shows that both peptide termini are anchored, as in other class I molecules, but the central residues in two independent pMHC complexes adopt completely different bulged conformations based on local environment. The MTF-E epitope is fully exposed within the putative T cell receptor (TCR) footprint. The flexibility demonstrated by the MTF-E structures illustrates how different TCRs may be raised against chemically identical, but structurally dissimilar, pMHC complexes

Glucose modifies the effect of endovascular thrombectomy in patients with acute stroke: a pooled-data meta-analysis

Background and Purpose: Hyperglycemia is a negative prognostic factor following acute ischemic stroke but is not known whether glucose is associated with the effects of endovascular thrombectomy in patients with large vessel stroke. In a pooled-data meta-analysis, we analyzed whether serum glucose is a treatment modifier of the efficacy of endovascular thrombectomy in acute stroke. Methods: Seven randomized trials compared endovascular thrombectomy with standard care between 2010 and 2017 (HERMES Collaboration). 1764 patients with large vessel stroke were allocated to endovascular thrombectomy (n=871) or standard care (n=893). Measurements included blood glucose on admission and functional outcome [modified Rankin Scale (mRS) range: 0-6; lower scores indicating less disability] at 3 months. The primary analysis evaluated whether glucose modified the effect of EVT over standard care on functional outcome, using ordinal logistic regression to test the interaction between treatment and glucose level. Results: Median (IQR) serum glucose on admission was 120 (104-140) mg/dl [6.6mmol/l (5.7-7.7) mmol/l]. Endovascular thrombectomy (EVT) was better than standard care in the overall pooled-data analysis [common odds ratio (acOR), 2.00 (95% CI 1.69–2.38); however, lower glucose levels were associated with greater effects of EVT over standard care. The interaction was nonlinear such that significant interactions were found in subgroups of patients split at glucose < or > 90mg/dl (5.0mmol/l) [(p=0.019 for interaction, acOR 3.81 (95% CI 1.73–8.41) for patients < 90 mg/dl vs 1.83 (95% CI 1.53–2.19) for patients > 90 mg/dl], and glucose < or > 100mg/dl (5.5mmol/l) [(p=0.004 for interaction, acOR 3.17 (95% CI 2.04–4.93) vs acOR 1.72 (95% CI 1.42–2.08)], but not between subgroups above these levels of glucose. Conclusions: Endovascular thrombectomy improved stroke outcomes compared to standard treatment regardless of glucose levels but the treatment effects were larger at lower glucose levels, with significant interaction effects persisting up to 90 to 100mg/dl (5.0-5.5mmol/l). Whether tight control of glucose improves the efficacy of endovascular thrombectomy following large vessel stroke warrants appropriate testing

Penumbral imaging and functional outcome in patients with anterior circulation ischaemic stroke treated with endovascular thrombectomy versus medical therapy: a meta-analysis of individual patient-level data

Background: CT perfusion (CTP) and diffusion or perfusion MRI might assist patient selection for endovascular thrombectomy. We aimed to establish whether imaging assessments of irreversibly injured ischaemic core and potentially salvageable penumbra volumes were associated with functional outcome and whether they interacted with the treatment effect of endovascular thrombectomy on functional outcome. Methods: In this systematic review and meta-analysis, the HERMES collaboration pooled patient-level data from all randomised controlled trials that compared endovascular thrombectomy (predominantly using stent retrievers) with standard medical therapy in patients with anterior circulation ischaemic stroke, published in PubMed from Jan 1, 2010, to May 31, 2017. The primary endpoint was functional outcome, assessed by the modified Rankin Scale (mRS) at 90 days after stroke. Ischaemic core was estimated, before treatment with either endovascular thrombectomy or standard medical therapy, by CTP as relative cerebral blood flow less than 30% of normal brain blood flow or by MRI as an apparent diffusion coefficient less than 620 μm2/s. Critically hypoperfused tissue was estimated as the volume of tissue with a CTP time to maximum longer than 6 s. Mismatch volume (ie, the estimated penumbral volume) was calculated as critically hypoperfused tissue volume minus ischaemic core volume. The association of ischaemic core and penumbral volumes with 90-day mRS score was analysed with multivariable logistic regression (functional independence, defined as mRS score 0–2) and ordinal logistic regression (functional improvement by at least one mRS category) in all patients and in a subset of those with more than 50% endovascular reperfusion, adjusted for baseline prognostic variables. The meta-analysis was prospectively designed by the HERMES executive committee, but not registered. Findings: We identified seven studies with 1764 patients, all of which were included in the meta-analysis. CTP was available and assessable for 591 (34%) patients and diffusion MRI for 309 (18%) patients. Functional independence was worse in patients who had CTP versus those who had diffusion MRI, after adjustment for ischaemic core volume (odds ratio [OR] 0·47 [95% CI 0·30–0·72], p=0·0007), so the imaging modalities were not pooled. Increasing ischaemic core volume was associated with reduced likelihood of functional independence (CTP OR 0·77 [0·69–0·86] per 10 mL, pinteraction=0·29; diffusion MRI OR 0·87 [0·81–0·94] per 10 mL, pinteraction=0·94). Mismatch volume, examined only in the CTP group because of the small numbers of patients who had perfusion MRI, was not associated with either functional independence or functional improvement. In patients with CTP with more than 50% endovascular reperfusion (n=186), age, ischaemic core volume, and imaging-to-reperfusion time were independently associated with functional improvement. Risk of bias between studies was generally low. Interpretation: Estimated ischaemic core volume was independently associated with functional independence and functional improvement but did not modify the treatment benefit of endovascular thrombectomy over standard medical therapy for improved functional outcome. Combining ischaemic core volume with age and expected imaging-to-reperfusion time will improve assessment of prognosis and might inform endovascular thrombectomy treatment decisions. Funding: Medtronic

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Addition of artesunate to chloroquine for treatment of Plasmodium falciparum malaria in Gambian children causes a significant but short-lived reduction in infectiousness for mosquitoes.

OBJECTIVES: Combination therapy using existing anti-malarials together with artesunate (AS) has been advocated as a method to slow the spread of drug resistance. We assessed the effect on Plasmodium falciparum transmissibility of the addition of AS to chloroquine (CQ) in an area of The Gambia where resistance to CQ is increasing. METHODS: Gambian children with acute uncomplicated P. falciparum malaria were treated with either CQ monotherapy (n=120) or the combination of CQ plus three doses of AS (CQ/AS; n=352). Post-treatment sexual-stage parasitaemia was assessed during a 4-week follow-up period. Experimental infections of Anopheles gambiae s.s. mosquitoes were performed with blood from patients who were carrying gametocytes 7 days after starting treatment (n=69). RESULTS: The addition of AS significantly reduced post-treatment prevalence and mean density of gametocytes in the first 14 days (day 7: 43.7% vs. 12.4%, 62.4/microl vs. 6.2/microl; day 14: 32.9% vs. 3.7%; 21.9/microl vs. 5.2/microl; CQ vs. CQ/AS), although by day 28 the benefits of the combination were substantially less marked (40.5% vs. 21.8%; 23.0/microl vs. 63.1/microl; CQ vs. CQ/AS). The duration of gametocyte carriage over the study period was significantly lower in the CQ/AS group (5.2 days vs. 1.5 days; CQ vs. CQ/AS). The estimated infectious proportion of children at day 7 was also lower in the combination group (19.2% vs. 3.4%; CQ vs. CQ/AS), as were the proportion of mosquitoes infected and mean oocyst density (11.5% vs. 0.9%; 0.3 vs. 0.01; CQ vs. CQ/AS). Treatment failure was associated with threefold and twofold higher gametocyte carriage rates during follow-up in CQ and CQ/AS groups, respectively (P<0.001 in both cases), and 26-fold and 2.3-fold higher intensity of infection at day 7 among CQ- and CQ/AS-treated children, respectively (P=0.002 and 0.30, respectively). CONCLUSION: The benefits of adding AS to CQ monotherapy in lowering gametocyte prevalence and density were transient, suggesting that the addition of AS delayed, but did not prevent, the emergence of gametocytes. This is consistent with our finding that treatment failure, and thus the presence of CQ-resistant parasites, was significantly associated with a higher gametocyte carriage rate in both treatment groups. At day 7, CQ monotherapy significantly favoured transmission of resistant infections, which showed an 11-fold greater intensity of transmission compared with infections that were successfully treated. In contrast, the combination of CQ/AS did not significantly favour resistant infections at day 7. We conclude that significant transmission-reduction is achieved by the combination but is not maintained because of the recrudescence of CQ-resistant parasites

Rapid assessment of perfusion-diffusion mismatch

Background and purpose: For MR perfusion-diffusion (PWI-DWI) mismatch to become routine in thrombolysis patient selection, rapid and reliable assessment tools are required. We examined interrater variability in PWI/DWI volume measurements and developed a rapid assessment tool based on the Alberta Stroke Program Early CT Scores (ASPECTS) system. Methods: DWI and PWI were performed in 35 patients with stroke <6 hours after symptom onset. DWI lesion and PWI (time to peak) volumes were measured with planimetric techniques by 4 raters and the 95% limits of agreement calculated. ASPECT scores were assessed separately by 4 investigators (2 experienced and 2 inexperienced) for DWI (MR DWI scores) and PWI (MR time to peak scores). MR mismatch scores were calculated as MR DWI-MR time to peak scores. Results: Interobserver variability was much greater for PWI (95% limit of agreement=±72.3 mL) than for DWI (95% limit of agreement=±12.6 mL). A semiautomated PWI volume (time to peak+2 s) was therefore used to calculate mismatch volume. MR mismatch scores ≥2 predicted 20% PWI-DWI mismatch by volume with mean 78% sensitivity (range, 72% to 84%) and 88% specificity (range, 83% to 90%). There was excellent agreement on mismatch classification using MR mismatch scores between experienced raters (weighted kappa scores of 0.94) with agreement in 34 of 35 cases. Agreement was less consistent between inexperienced raters (weighted kappa=0.49, 28 of 35 cases). Conclusions: Variability in planimetric mismatch measurements arises primarily from differences in PWI volume assessment. High specificity and interrater reliability may make MR mismatch scores an ideal rapid screening tool for potential thrombolysis patients