HIV-1 co-infection does not reduce exposure to rifampicin, isoniazid, and pyrazinamide in South African tuberculosis outpatients

There are contrasting data in the literature about antituberculosis plasma drug concentrations in HIV-1-coinfected patients. We report the pharmacokinetics of rifampin, isoniazid, and pyrazinamide in a cohort of patients being treated for active tuberculosis, the majority of whom were coinfected with HIV-1 and had commenced antiretroviral therapy within 2 months of starting antituberculosis treatment. We also examined the association between antituberculosis drug concentrations and reported drug side effects at the 2-month clinical review. One hundred patients with pulmonary tuberculosis (65% coinfected with HIV-1) were intensively sampled to determine rifampin, isoniazid, and pyrazinamide plasma concentrations after 7 to 8 weeks of a daily quadruple-therapy regimen dosed according to World Health Organization (WHO) weight bands. Pharmacokinetic parameters were determined for each patient by using nonlinear mixed-effects models. HIV-1-coinfected patients had lower clearance rates for rifampin (21% decrease) and isoniazid (23% decrease) than HIV-1-uninfected patients, with resulting higher areas under the concentration-time curve from 0 to 24 h (AUC0–24) and maximum concentrations of drug in serum (Cmax). Antiretroviral therapy (ART) that included double-standard-dose lopinavir/ritonavir further lowered rifampin clearance, by 46%, and increased the AUC0–24. The current uniform dosing (per kilogram of body weight) across WHO weight bands was associated with a trend of decreased pharmacokinetic exposures for the lowest weight band. Use of fat-free mass as opposed to total body weight for allometric scaling of clearance significantly improved the model. Ambulant HIV-1-coinfected patients, the majority of whom were coprescribed ART, did not have reduced antituberculosis drug concentrations compared to HIV-1-uninfected patients

Functional Diversity and Structural Disorder in the Human Ubiquitination Pathway

The ubiquitin-proteasome system plays a central role in cellular regulation and protein quality control (PQC). The system is built as a pyramid of increasing complexity, with two E1 (ubiquitin activating), few dozen E2 (ubiquitin conjugating) and several hundred E3 (ubiquitin ligase) enzymes. By collecting and analyzing E3 sequences from the KEGG BRITE database and literature, we assembled a coherent dataset of 563 human E3s and analyzed their various physical features. We found an increase in structural disorder of the system with multiple disorder predictors (IUPred - E1: 5.97%, E2: 17.74%, E3: 20.03%). E3s that can bind E2 and substrate simultaneously (single subunit E3, ssE3) have significantly higher disorder (22.98%) than E3s in which E2 binding (multi RING-finger, mRF, 0.62%), scaffolding (6.01%) and substrate binding (adaptor/substrate recognition subunits, 17.33%) functions are separated. In ssE3s, the disorder was localized in the substrate/adaptor binding domains, whereas the E2-binding RING/HECT-domains were structured. To demonstrate the involvement of disorder in E3 function, we applied normal modes and molecular dynamics analyses to show how a disordered and highly flexible linker in human CBL (an E3 that acts as a regulator of several tyrosine kinase-mediated signalling pathways) facilitates long-range conformational changes bringing substrate and E2-binding domains towards each other and thus assisting in ubiquitin transfer. E3s with multiple interaction partners (as evidenced by data in STRING) also possess elevated levels of disorder (hubs, 22.90% vs. non-hubs, 18.36%). Furthermore, a search in PDB uncovered 21 distinct human E3 interactions, in 7 of which the disordered region of E3s undergoes induced folding (or mutual induced folding) in the presence of the partner. In conclusion, our data highlights the primary role of structural disorder in the functions of E3 ligases that manifests itself in the substrate/adaptor binding functions as well as the mechanism of ubiquitin transfer by long-range conformational transitions. © 2013 Bhowmick et al

Splitting or lumping? A conservation dilemma exemplified by the critically endangered Dama Gazelle (Nanger dama)

Managers of threatened species often face the dilemma of whether to keep populations separate to conserve local adaptations and minimize the risk of outbreeding, or whether to manage populations jointly to reduce loss of genetic diversity and minimise inbreeding. In this study we examine genetic relatedness and diversity in three of the five last remaining wild populations of dama gazelle and a number of captive populations, using mtDNA control region and cytochrome b data. Despite the sampled populations belonging to the three putative subspecies, which are delineated according to phenotypes and geographical location, we find limited evidence for phylogeographical structure within the data and no genetic support for the putative subspecies. In the light of these data we discuss the relevance of inbreeding depression, outbreeding depression, adaptive variation, genetic drift, and phenotypic variation to the conservation of the dama gazelle and make some recommendations for its future conservation management. The genetic data suggest that the best conservation approach is to view the dama gazelle as a single species without subspecific divisions

Neonicotinoids target distinct nicotinic acetylcholine receptors and neurons, leading to differential risks to bumblebees

This research was funded jointly by BBSRC, DEFRA, NERC, the Scottish Government and The Wellcome Trust, under the Insect Pollinators Initiative (UK) grant BB/1000313/1(CNC).There is growing concern over the risk to bee populations from neonicotinoid insecticides and the long-term consequences of reduced numbers of insect pollinators to essential ecosystem services and food security. Our knowledge of the risk of neonicotinoids to bees is based on studies of imidacloprid and thiamethoxam and these findings are extrapolated to clothianidin based on its higher potency at nicotinic acetylcholine receptors. This study addresses the specificity and consequences of all three neonicotinoids to determine their relative risk to bumblebees at field-relevant levels (2.5 ppb). We find compound-specific effects at all levels (individual cells, bees and whole colonies in semi-field conditions). Imidacloprid and clothianidin display distinct, overlapping, abilities to stimulate Kenyon cells, indicating the potential to differentially influence bumblebee behavior. Bee immobility was induced only by imidacloprid, and an increased vulnerability to clothianidin toxicity only occurred following chronic exposure to clothianidin or thiamethoxam. At the whole colony level, only thiamethoxam altered the sex ratio (more males present) and only clothianidin increased queen production. Finally, both imidacloprid and thiamethoxam caused deficits in colony strength, while no detrimental effects of clothianidin were observed. Given these findings, neonicotinoid risk needs to be considered independently for each compound and target species.Publisher PDFPeer reviewe

Linezolid population pharmacokinetic model in plasma and cerebrospinal fluid among patients with tuberculosis meningitis

BACKGROUND: Linezolid is evaluated in novel treatment regimens for tuberculous meningitis (TBM). Linezolid pharmacokinetics have not been characterized in this population, particularly in cerebrospinal fluid (CSF) where exposures may be affected by changes in protein concentration. Linezolid co-administration with high-dose rifampicin, has also not been studied. We aimed to characterize linezolid plasma and CSF pharmacokinetics in adults with TBM. METHODS: In LASER-TBM pharmacokinetic-substudy, the intervention groups received high-dose rifampicin (35mg/kg) plus linezolid 1200mg/day for 28days, then reduced to 600mg/day. Plasma sampling was done on day 3 (intensive) and on day 28 (sparse). A lumbar CSF sample was obtained on both visits. RESULTS: 30-participants, median(min-max) age and weight of 40(27-56)years and 58(30-96)kg, contributed 247 plasma and 28 CSF observations. Plasma pharmacokinetics was described by one-compartment model with first-order absorption and saturable elimination. Maximal clearance was 7.25L/h, and Km was 27.2mg/L. Rifampicin co-treatment duration did not affect linezolid pharmacokinetics. CSF-Plasma partitioning correlated with CSF total-protein upto 1.2g/L where the partition-coefficient reached maximal value of 37%. Plasma-CSF equilibration half-life was ∼3.5hours. CONCLUSION: Linezolid was readily detected in CSF despite high-dose rifampicin co-administration. These findings support continued clinical evaluation of linezolid plus high-dose rifampicin for the treatment of TBM in adults

Genotypic Diversity Is Associated with Clinical Outcome and Phenotype in Cryptococcal Meningitis across Southern Africa.

Cryptococcal meningitis is a major cause of mortality throughout the developing world, yet little is known about the genetic markers underlying Cryptococcal virulence and patient outcome. We studied a cohort of 230 Cryptococcus neoformans (Cn) isolates from HIV-positive South African clinical trial patients with detailed clinical follow-up using multi-locus sequence typing and in vitro phenotypic virulence assays, correlating these data with clinical and fungal markers of disease in the patient. South African Cn displayed high levels of genetic diversity and locus variability compared to globally distributed types, and we identified 50 sequence types grouped within the main molecular types VNI, VNII and VNB, with 72% of isolates typed into one of seven 'high frequency' sequence types. Spatial analysis of patients' cryptococcal genotype was not shown to be clustered geographically, which might argue against recent local acquisition and in favour of reactivation of latent infection. Through comparison of MLST genotyping data with clinical parameters, we found a relationship between genetic lineage and clinical outcome, with patients infected with the VNB lineage having significantly worse survival (n=8, HR 3.35, CI 1.51-7.20, p=0.003), and this was maintained even after adjustment for known prognostic indicators and treatment regimen. Comparison of fungal genotype with in vitro phenotype (phagocytosis, laccase activity and CSF survival) performed on a subset of 89 isolates revealed evidence of lineage-associated virulence phenotype, with the VNII lineage displaying increased laccase activity (p=0.001) and ex vivo CSF survival (p=0.0001). These findings show that Cryptococcus neoformans is a phenotypically heterogeneous pathogen, and that lineage plays an important role in cryptococcal virulence during human infection. Furthermore, a detailed understanding of the genetic diversity in Southern Africa will support further investigation into how genetic diversity is structured across African environments, allowing assessment of the risks different ecotypes pose to infection

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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Quantum encryption with certified deletion

Given a ciphertext, is it possible to prove the deletion of the underlying plaintext? Since classical ciphertexts can be copied, clearly such a feat is impossible using classical information alone. In stark contrast to this, we show that quantum encodings enable certified deletion. More precisely, we show that it is possible to encrypt classical data into a quantum ciphertext such that the recipient of the ciphertext can produce a classical string which proves to the originator that the recipient has relinquished any chance of recovering the plaintext should the decryption key be revealed. Our scheme is feasible with current quantum technology: the honest parties only require quantum devices for single-qubit preparation and measurements; the scheme is also robust against noise in these devices. Furthermore, we provide an analysis that is suitable in the finite-key regime.Comment: 28 pages, 1 figure. Some technical details modifie

Population Pharmacokinetics of Rifampicin in Plasma and Cerebrospinal Fluid in Adults With Tuberculosis Meningitis

Background Several ongoing clinical trials are evaluating high-dose rifampicin (up to 35 mg/kg) for tuberculous meningitis (TBM). However, rifampicin pharmacokinetics at higher doses is not fully characterized, particularly in cerebrospinal fluid (CSF), the site of TBM disease. Methods In a randomized controlled trial, adults with HIV-associated TBM were assigned to experimental arms of high-dose rifampicin (oral, 35 mg/kg; intravenous, 20 mg/kg) plus linezolid, with or without aspirin, or a control arm that received the standard of care with 10 mg/kg of oral rifampicin. Rifampicin concentrations, including the unbound fraction, were measured on plasma samples, and CSF was collected on days 3 and 28 of study enrollment. Data were analyzed by nonlinear mixed effects modeling. Results In total, 400 plasma and 44 CSF rifampicin concentrations from 48 participants were used for model development. The median (range) age and weight were 39 years (25–78) and 60 kg (30–107). Rifampicin pharmacokinetics was best described by a 2-compartment disposition model with first-order transit oral absorption and elimination via saturable hepatic extraction. Typical clearance values for the standard dose for days 3 and 28 were 33.1 and 41.4 L/h, respectively; high-dose values were 46.1 and 70.2 L/h. The CSF-plasma ratio was approximately 6% and the equilibration half-life was 3.2 hours. Simulated standard-dose rifampicin did not reach CSF concentrations above the critical concentration for Mycobacterium tuberculosis. Conclusions CSF penetration with standard-dose rifampicin is low. Our findings support continued evaluation of high-dose rifampicin for TBM treatment

Population pharmacokinetics of pyrazinamide and isoniazid in plasma and cerebrospinal fluid from South African adults with tuberculous meningitis

Pyrazinamide and isoniazid are first-line drugs for tuberculous meningitis (TBM), but limited information is available on their plasma pharmacokinetics, and particularly cerebrospinal fluid (CSF) penetration, in patients with TBM. Any potential effect of co-administration with high-dose rifampicin, also being evaluated in trials for TBM, is unknown. Understanding this is important for dose optimisation. We characterized pyrazinamide and isoniazid plasma and CSF pharmacokinetics among adults enrolled in a phase 2 clinical trial of intensified antibiotic therapy for HIV-associated TBM. Participants were randomized to receive either standard TBM treatment (including rifampicin 10 mg/kg) or high-dose rifampicin (35 mg/kg) plus linezolid, with or without aspirin. Plasma and lumbar CSF samples were collected on days 3 and 28 after study enrollment, and drug concentrations were measured using liquid chromatography-tandem mass spectrometry. Data were analysed using nonlinear mixed-effects modeling. Forty-nine participants provided 414 plasma and 44 CSF concentrations. Pyrazinamide CSF concentrations equilibrated with plasma with a half-life of 0.66 h and a pseudo-partition coefficient of 1.05. Isoniazid concentrations equilibrated with a half-life of 3.87 h and a pseudo-partition coefficient of 1.04. Pyrazinamide clearance increased by 30% from day 3 to day 28. NAT2 phenotype determined multi-modal isoniazid clearance. High-dose rifampicin did not affect pyrazinamide or isoniazid plasma pharmacokinetics or CSF penetration. Both drugs achieved exposure in CSF similar to plasma, supporting their crucial role in TBM treatment. Plasma pharmacokinetics of pyrazinamide and isoniazid in TBM were consistent with previously reported values in pulmonary tuberculosis, even when co-administered with high-dose rifampicin