Gabor Nagy

Anti-bacterial monoclonal antibodies: Back to the future?

Todays medicine has to deal with the emergence of multi-drug resistant bacteria, and is beginning to be confronted with pan-resistant microbes. This worsening inadequacy of the antibiotics concept, which has ruled infectious medicine in the last six decades creates an increasing unmet medical need that can be addressed by passive immunization. While past experience from the pre-antibiotic era with serum therapy was in many cases encouraging, antibacterial monoclonal antibodies have so far suffered high attrition rates in the clinic, generally from lack of efficacy. Yet, we believe that recent developments in a number of areas such as infectious disease pathogenesis research, translational medicine, mAb engineering, mAb manufacturing and rapid bedside diagnostics are converging to make the medium-term future permissive for antibacterial mAb development. Here, we review antibacterial mAb-based approaches that are or were in clinical development, and may potentially act as paradigms with regards to molecular targets, antibody formats and mode-of-action, pre-clinical validation and selection of most relevant patient populations, in order to increase the likelihood of successful product development in this field.

In situ electrochemical impedance spectroscopy of Zr-1%Nb under VVER primary circuit conditions

Oxide layers were grown on tubular samples of Zr–1%Nb under conditions simulating those in VVER-type pressurised water reactors, viz. in near-neutral borate solutions in an autoclave at 290 °C. These samples were investigated using electrochemical impedance spectroscopy which was found to be suitable to follow in situ the corrosion process. A –CPEox∥Rox– element was used to characterise the oxide layer on Zr–1%Nb. Both the CPEox coefficient, σox, and the parallel resistance, Rox, were found to be thickness dependent. The layer thickness, however, can only be calculated after a calibration procedure. The temperature dependence of the CPEox element was also found to be anomalous while the temperature dependence of Rox indicates that the oxide layer has semiconductor properties. The relaxation time – defined as (Roxσox)1/α – was found to be quasi-independent of oxidation time and temperature; thus it is characteristic to the oxide layer on Zr–1%Nb.

Continuous-time random-walk theory of interfering diffusion and chemical reaction with an application to electrochemical impedance spectra of oxidized Zr–1%Nb

A microscopic theory is developed for the interplay of diffusion and chemical reaction and the results are compared with electrode impedance measurements on an oxide electrode. The theory is based on the ideas of continuous-time random walk and accounts for the interference of diffusion and recombination of the charge carriers in the oxide. The treatment results in a dispersive diffusivity with two time constants, one of them corresponding to the random walk, the other to the reaction. Combining this diffusivity with the Warburg electrode admittance expression, which refers to cases where the rate-limiting step is diffusion in a semi-infinite medium bounded by a plane, an admittance function is obtained. The phase angle is found to be higher than 45 degrees distinguishing it from the Gerischer impedance which was developed for a related problem. The oxides were produced by hydrothermal oxidation of Zr-l%Nb alloy, a metal used as cladding material for nuclear fuel elements. The electrode impedance spectra of Zr/Zr-oxide electrodes in aqueous SO(3) (2-) solutions were taken at various anodic voltages between 1 Hz and 100 kHz and temperatures between 278 and 333 K. The theoretical admittance functions could be successfully compared with the observed spectra. Both the functional forms and the fitted parameter values support our theory which is also in keeping with Macdonalds point-defect model.

Oxide layers of Zr–1% Nb under PWR primary circuit conditions

Abstract Oxide layers were grown on Zr–1% Nb under conditions simulating those in VVER-type pressurised water reactors (PWRs), viz. in borate solutions in an autoclave at 290°C. The layers were characterised by various methods: their respective thickness values were determined by weight gain measurements, Rutherford backscattering (RBS), nuclear reaction analysis (NRA) and scanning electron microscopy (SEM); the electrical properties were tested by electrochemical impedance spectroscopy. The results show that the oxide layer on Zr–1% Nb is homogeneous and somewhat thicker than that on Zircaloy-4.

Dispersive charge carrier mobility in a surface oxide layer

The electrode impedance spectrum of the oxide produced on a Zr–1%Nb surface in an aqueous solution at 290 °C is analysed as a function of temperature between 20 °C and 290 °C. The portion of the spectrum, relevant to the oxide, is treated in terms of a parallel CPE∥Rox equivalent circuit (CPE denoting constant phase element, Rox ohmic resistor). Considering also the effect of temperature CPE is understood as a dispersive resistance described by the continuous time random walk theory of Scher and Lax. Distinction is made between the kinetics of oxide growth and of non-Faraday charge transport, the time constant of the latter being obtained directly from impedance data.

Development of a plasmid free CRISPR-Cas9 system for the genetic modification of Mucor circinelloides

Mucor circinelloides and other members of Mucorales are filamentous fungi, widely used as model organisms in basic and applied studies. Although genetic manipulation methods have been described for some Mucoral fungi, construction of stable integrative transformants by homologous recombination has remained a great challenge in these organisms. In the present study, a plasmid free CRISPR-Cas9 system was firstly developed for the genetic modification of a Mucoral fungus. The described method offers a rapid but robust tool to obtain mitotically stable mutants of M. circinelloides via targeted integration of the desired DNA. It does not require plasmid construction and its expression in the recipient organism. Instead, it involves the direct introduction of the guide RNA and the Cas9 enzyme and, in case of homology directed repair (HDR), the template DNA into the recipient strain. Efficiency of the method for non-homologous end joining (NHEJ) and HDR was tested by disrupting two different genes, i.e. carB encoding phytoene dehydrogenase and hmgR2 encoding 3-hydroxy-3-methylglutaryl-CoA reductase, of M. circinelloides. Both NHEJ and HDR resulted in stable gene disruption mutants. While NHEJ caused extensive deletions upstream from the protospacer adjacent motif, HDR assured the integration of the deletion cassette at the targeted site.

Study of corrosion of nuclear fuel cladding by photoelectrochemical response

Abstract The photoelectrochemical response of Zr oxide, produced by high-temperature hydrothermal oxidation, was studied. The aim was to characterise the kinetics of oxidation and to propose a simple method for the determination of oxide thickness. Photocurrents, measured with the oxide biased anodically in neutral Na sulphite solutions, under illumination with visible light, showed a more than two orders of magnitude variation with oxidation time. Sulphite ions react with the photoinjected holes easily. The observations could be described in terms of recombination of photoproduced charge carriers in the course of their diffusion across the oxide layer. The proportionality between oxide thickness, Lox, and the cube root of oxidation time, t ox L ox α t ox 1/3 , was demonstrated, and a way for the estimation of oxide thickness was given.

Kinetic and statistical analysis of primary circuit water chemistry data in a VVER power plant

Abstract The results of chemical and radiochemical analyses of the primary circuit coolant liquid, obtained between 1995 and 1999 at the four VVER-type blocks of the Paks (Hungary) nuclear power station, are assessed. A model has been developed regarding the pressure vessel with its auxiliary parts plus the fuel elements as the zone, with the six steam generators as one single unit. The stream from the steam generator is split, with its larger part returning to the zone through the main circulating pump and the smaller one passing through the purifier column. Based on this flowchart, the formation kinetics of corrosion products and of radioactive substances are evaluated. Correlation analysis is applied to reveal any eventual interdependence of the processes, whereas the range-per-scatter (R/S) method is used to characterize the random or deterministic nature of a process. The evaluation of the t → ∞ limits of the kinetic equations enables one to conclude that (a) the total amount of corrosion products per element during one cycle is almost always <15 kg and (b) the zone acts as a highly efficient filter with an efficiency of ~1. The R/S results show that the fluctuations in the concentrations of the corrosion products are persistent; this finding indicates that random effects play here little if any role and that the processes in the coolant are under control. Correlation analyses show that the variations of the concentrations are practically uncorrelated and that the processes are independent of each other.

Photoelectrochemical Production of Atomic Hydrogen at Tungsten Bronze/Aqueous Solution Interface

The cathodic photoeffect on hydrogenated sodium tungsten bronzes was studied in acid solutions under potentiostatic conditions. Solute effect proved the accompanying chemical reactions in the liquid phase to be brought about by hydrogen atoms. Kinetic analysis of the photocurrent showed that photoproduction and second-order recombination of the charge carriers in the solid are followed by reversible reduction of H/sup +/ at the interface. Finally H-atoms react with solutes like O/sub 2/, NO/sub 3//sup -/, Fe/sup 3+/, Fe(CN)/sub 6//sup 3-/, or tetranitromethane. The kinetics of charge carrier formation and of chemical reactions seem to be only weakly coupled, and the entire process can be described in terms of homogeneous kinetics showing diffusion and migration to be kinetically unimportant.

Interaction of THP-1 monocytes with conidia and hyphae of different Curvularia strains

Interaction of the human monocytic cell line, THP-1 with clinical isolates of three Curvularia species were examined. Members of this filamentous fungal genus can cause deep mycoses emerging in both immunocompromised and immunocompetent patients. It was found that monocytes reacted only to the hyphal form of Curvularia lunata. Cells attached to the germ tubes and hyphae and production of elevated levels of interleukin (IL)-8 and IL-10 and a low level of TNF-α were measured. At the same time, monocytes failed to produce IL-6. This monocytic response, especially with the induction of the anti-inflammatory IL-10, correlates well to the observation that C. lunata frequently cause chronic infections even in immunocompetent persons. Despite the attachment to the hyphae, monocytes could not reduce the viability of the fungus and the significant decrease in the relative transcript level of HLA-DRA assumes the lack of antigen presentation of the fungus by this cell type. C. spicifera and C. hawaiiensis failed to induce the gathering of the cells or the production of any analyzed cytokines. Monocytes did not recognize conidia of Curvularia species, even when melanin was lacking in their cell wall.