A new tool for the chemical genetic investigation of the Plasmodium falciparum Pfnek-2 NIMA-related kinase

Background: Examining essential biochemical pathways in Plasmodium falciparum presents serious challenges, as standard molecular techniques such as siRNA cannot be employed in this organism, and generating gene knock-outs of essential proteins requires specialized conditional approaches. In the study of protein kinases, pharmacological inhibition presents a feasible alternative option. However, as in mammalian systems, inhibitors often lack the desired selectivity. Described here is a chemical genetic approach to selectively inhibit Pfnek-2 in P. falciparum, a member of the NIMA-related kinase family that is essential for completion of the sexual development of the parasite. Results: Introduction of a valine to cysteine mutation at position 24 in the glycine rich loop of Pfnek-2 does not affect kinase activity but confers sensitivity to the protein kinase inhibitor 4-(6-ethynyl-9H-purin-2-ylamino) benzene sulfonamide (NCL-00016066). Using a combination of in vitro kinase assays and mass spectrometry, (including phosphoproteomics) the study shows that this compound acts as an irreversible inhibitor to the mutant Pfnek2 likely through a covalent link with the introduced cysteine residue. In particular, this was shown by analysis of total protein mass using mass spectrometry which showed a shift in molecular weight of the mutant kinase in the presence of the inhibitor to be precisely equivalent to the molecular weight of NCL-00016066. A similar molecular weight shift was not observed in the wild type kinase. Importantly, this inhibitor has little activity towards the wild type Pfnek-2 and, therefore, has all the properties of an effective chemical genetic tool that could be employed to determine the cellular targets for Pfnek-2. Conclusions: Allelic replacement of wild-type Pfnek-2 with the mutated kinase will allow for targeted inhibition of Pfnek-2 with NCL-00016066 and hence pave the way for comparative studies aimed at understanding the biological role and transmission-blocking potential of Pfnek-2. © 2016 The Author(s)

Probing the photoreactivity of aryl chlorides with oxygen

Molecular oxygen was used to probe the mechanism of the phototransformation of chlorobenzene and 4-chloroanisole in organic solvents. Laser flash photolysis, electron paramagnetic resonance and product distribution studies clarified the reaction mechanisms of these compounds under a wide range of conditions. The main primary photochemical reaction step is the homolytic cleavage of the C-Cl bond to produce a triplet radical pair in the solvent cage. In non-polar solvents hydrogen abstraction, after radical diffusion, leads to reduction. In polar solvents, in addition to H-abstraction, electron transfer within the caged radical pair occurs and leads to an ion pair (phenyl cation and Cl-). In the presence of oxygen, phenyl radicals can form phenylperoxyl radicals which have a bathochromically shifted absorption, thus making the homolytic cleavage visible by flash photolysis. The peroxyl radicals can couple, leading to more polar compounds, or undergo back reaction to the phenyl radical. For concentrations of the aryl chlorides of higher than 10-3 M, dimerization becomes an important transformation process and occurs after reaction of the transients with ground state molecules. In addition, excimer formation is postulated to be involved in the dimerization process

Sequence-Based Hepatitis B Virus Antiviral Resistance Testing in Switzerland

BACKGROUND: A growing number of patients with chronic hepatitis B is being treated for extended periods with nucleoside and/or nucleotide analogs. In this context, antiviral resistance represents an increasingly common and complex issue. METHODS: Mutations in the hepatitis B virus (HBV) reverse transcriptase (rt) gene and viral genotypes were determined by direct sequencing of PCR products and alignment with reference sequences deposited in GenBank. RESULTS: Plasma samples from 60 patients with chronic hepatitis B were analyzed since March 2009. The predominant mutation pattern identified in patients with virological breakthrough was rtM204V/I ± different compensatory mutations, conferring resistance to L-nucleosides (lamivudine, telbivudine, emtricitabine) and predisposing to entecavir resistance (n = 18). Complex mutation patterns with a potential for multidrug resistance were identified in 2 patients. Selection of a fully entecavir resistant strain was observed in a patient exposed to lamivudine alone. Novel mutations were identified in 1 patient. Wild-type HBV was identified in 9 patients with suspected virological breakthrough, raising concerns about treatment adherence. No preexisting resistance mutations were identified in treatment-naïve patients (n = 13). Viral genome amplification and sequencing failed in 16 patients, of which only 2 had a documented HBV DNA > 1000 IU/ml. HBV genotypes were D in 28, A in 6, B in 4, C in 3 and E in 3 patients. Results will be updated in August 2010 and therapeutic implications discussed. CONCLUSIONS: With expanding treatment options and a growing number of patients exposed to nucleoside and/or nucleotide analogs, sequence-based HBV antiviral resistance testing is expected to become a cornerstone in the management of chronic hepatitis B

Role of prethymic cells in acquisition of self-tolerance

Conceptual and experimental approaches have made it evident that self-tolerance is not laid down genetically but is instead acquired during development and is then actively maintained throughout adult life. The emergence of T-lymphocyte diversity and the acquisition of self-tolerance are presumed to be processes well-synchronized in ontogeny, in order to avoid reactivity against self. Not only is there a lack of definitive evidence regarding mechanisms leading to selftolerance, but at which stage of lymphocyte differentiation self-tolerance occurs also remains obscure. Self-non-self discrimination by T lymphocytes could be achieved at any of three stages, i.e., prethymic, intrathymic, or postthymic. In the first o'f these stages, i.e., before cells enter the thymus, information about self would be obtained from antigens expressed at that stage by the host, provided that prethymic cells manifest sufficient diversity for recognition of these antigens. In the second stage, information about self would be derived from the H-2 haplotype displayed by the thymus. This proposition stems from views expressed by Burner (1) and Jerne (2). After T-cell emigration fro

External validation of the nomogram for individualized prediction of hepatocellular carcinoma occurrence in patients with hepatitis C virus–related compensated cirrhosis

SCOPUS: le.jinfo:eu-repo/semantics/publishe

Diagnosis accuracy of ALT and waist circumference as a screening test for insulin resistance

ALT and waist circumference are both correlated to insulin resistance (IR). Objective: To determine whether ALT provides information in addition to waist circumference for identifying IR. Methods: IR was defined by HOMA-IR index ≥3. In this Europid population, a waist circumference ≥80 cm in women and ≥94 cm in men was considered excessive. Elevated ALT was defined using either the usual cut-off or updated cut-offs of 19 U/l in women and 30 U/l in men. Results: 288 participants without medication affecting insulin concentration were included. 81 (28%) were insulin resistant, 30 (10%) and 98 (34%) had increased ALT using usual and updated cut-offs, respectively, and 218 (76%) had excessive waist circumference. Among subjects with normal waist circumference, IR was as frequent in participants with normal ALT as in those with increased ALT. Among subjects with excessive waist circumference, IR was less frequent in participants with normal ALT according to the usual cut-off (31% vs. 56%, p=0.01), and tended to be less frequent in participants with normal ALT according to updated cut-offs (29% vs. 41%, p=0.07) than in those with increased ALT. Conclusion: ALT is useful for identifying IR only if waist circumference is excessive. In subjects with excessive waist circumference, IR is present in more than 40% in women with ALT >19 U/l and in men with ALT >30 U/l, and in more than 50% in individuals with ALT >45 U/l.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Characteristics of patients with hepatitis B virus and hepatitis C virus dual infection in a Western European country: Comparison with monoinfected patients

The epidemiology of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections is continuously evolving. Updated data on dual HBV and HCV infection are still needed. AIMS: To assess the main characteristics of patients with HBV and HCV dual infection, to compare these with those of patients infected with either HBV or HCV and, among patients with dual infection, to assess fibrosis according to HCV replication. METHODS: Data of 23 patients with dual infection were compared to data from 92 age and sex-matched HBV or HCV monoinfected patients. RESULTS: Patients with dual infection were more often immigrants from Africa or Asia than HCV or HBV patients (52% vs. 20% and 22%, respectively, P=0.01). Intravenous drug use was the route of transmission in 22% of patients with dual infection, which was less frequent than in HCV patients (41%) but more frequent than in HBV patients (0%). Extensive fibrosis or cirrhosis was as frequent among dual-infected patients as among those with HCV or chronic hepatitis B infection (19% vs. 29% vs. 14%, respectively, P=0.4), even when fibrosis stage was reported considering the duration of infection. In dual-infected patients, the prevalence of extensive fibrosis or cirrhosis was similar in patients with and without detectable HCV RNA (18% vs. 20%). CONCLUSIONS: Patients with HBV and HCV dual infection were more often immigrants from Africa or Asia and had similar fibrosis stages than HCV or HBV monoinfected patients. In patients with dual infection, extensive fibrosis or cirrhosis was not associated with HCV replication.status: publishe

Hepatitis E virus as a cause of acute hepatitis acquired in Switzerland

BACKGROUND: Autochthonous hepatitis E is increasingly recognized as zoonotic infection in western countries. Serological assays have varying sensitivity and specificity. METHODS: We implemented molecular testing to identify and characterize acute hepatitis E acquired in Switzerland. RESULTS: Ninety-three cases of mostly symptomatic acute hepatitis E acquired in Switzerland were documented by PCR between November 2011 and December 2016. Median HEV RNA was 7.5 x 104 IU/mL (range, 5.3 to 4.7 x 107 IU/mL). HEV genotyping was successful in 78 patients, revealing genotype 3 in 75 and genotype 4 in three patients. Phylogenetic analyses revealed a few limited geographical and temporal clusters. Of the 91 patients with available anti-HEV IgM serology, four were negative; three of these were also IgG-negative, likely as a result of immunosuppression, and one was IgG-positive, a constellation compatible with HEV reinfection. Median age of the patients was 58 years (range, 20-80 years); 71 (76.3%) were men and 49 of these (69.0%) were ≥ 50 years old. The clinical course was particularly severe in patients with underlying chronic liver disease, with fatal outcome in two patients. Six patients (6.5%) presented with neuralgic amyotrophy. CONCLUSIONS: Nucleic acid-based diagnosis reveals HEV as a relevant cause of acute hepatitis in Switzerland. Middle-aged and elderly men constitute the majority of symptomatic patients. Testing for HEV should be included early in the diagnostic workup of acute hepatitis and of neuralgic amyotrophy, a typical extrahepatic manifestation of HEV genotype 3 infection