102,288 research outputs found
Macrophage NO2- production as a sensitive and rapid assay for the quantitation of murine IFN-gamma
No full textMacrophage production of arginine-derived NO2- provides a simple method for detection and quantitation of interferon-gamma (IFN-gamma) in murine cell culture fluids. When the macrophage cell line RAW 264 is cultured overnight with IFN-gamma in the presence of 10 ng/ml LPS, NO2- release, as determined by a simple colorimetric assay, is proportional to the concentration of IFN-gamma and is inhibited by monoclonal antibody to IFN-gamma. A high degree of correlation was obtained when antigen stimulated T lymphocyte supernatants were tested for IFN-gamma by ELISA and the NO2- production assay
Malaria vaccine: immunization of mice with a synthetic T cell helper epitope alone leads to protective immunity
No full textThe immunogenicity of the non-repetitive sequences of the Plasmodium berghei circumsporozoite (CS) protein was studied using synthetic peptides. Two CS sequences (residues 20-39 and 57-70) exhibiting T cell helper activity were identified. Immunization of BALB/c mice with a branched peptide containing either the 20-39 or the 57-70 sequence and two repeats (B epitope) in a linear sequence induced high titers of anti-repeat and anti-sporozoite antibodies. Mice immunized with the T-B construct (high antibody titers) or with the 57-70 epitope alone (no serum anti-repeat or anti-peptide antibodies) were protected to a similar degree after challenge with infective sporozoites. No protection was obtained in mice immunized with the 20-39 epitope. These results indicate that BALB/c mice can be protected either by effector T cells or by high levels of anti-repeat antibodies. Thus, in the same strain, a double mechanism of protection can be obtained by a synthetic peptide vaccine
Plasmodium falciparum merozoite surface protein 2: epitope mapping and fine specificity of human antibody response against non-polymorphic domains
No full textTwo long synthetic peptides representing the dimorphic and constant C-terminal domains of the two allelic families of Plasmodium falciparum merozoite surface proteins 2 are considered promising malaria vaccine candidates. The aim of the current study is to characterize the immune response (epitope mapping) in naturally exposed individuals and relate immune responses to the risk of clinical malaria.; To optimize their construction, the fine specificity of human serum antibodies from donors of different age, sex and living in four distinct endemic regions was determined in ELISA by using overlapping 20 mer peptides covering the two domains. Immune purified antibodies were used in Western blot and immunofluorescence assay to recognize native parasite derivate proteins.; Immunodominant epitopes were characterized, and their distribution was similar irrespective of geographic origin, age group and gender. Acquisition of a 3D7 family and constant region-specific immune response and antibody avidity maturation occur early in life while a longer period is needed for the corresponding FC27 family response. In addition, the antibody response to individual epitopes within the 3D7 family-specific region contributes to protection from malaria infection with different statistical weight. It is also illustrated that affinity-purified antibodies against the dimorphic or constant regions recognized homologous and heterologous parasites in immunofluorescence and homologous and heterologous MSP2 and other polypeptides in Western blot.; Data from this current study may contribute to a development of MSP2 vaccine candidates based on conserved and dimorphic regions thus bypassing the complexity of vaccine development related to the polymorphism of full-length MSP2
Susceptibility of Integrated circuits to RFI: analysis of PWM current-mode controllers for snips
No full textAsymmetric Digital Dual-Edge Modulator for Dynamic Performance Improvement of Multiloop-Controlled VSI
No full textThis article proposes the architecture and a graphical-based analysis for a digital asymmetric dual edge (ADE) carrier-based pulsewidth modulator. In its digital version, it retains some advantages offered by the analog implementation. Indeed, in single-sampling operation, the phase delay introduced by this modulator is always less than or equal to the one obtained with the trailing-triangle edge (TTE) carrier. Moreover, by combining the advantages given by the ADE carrier and the double sampling of the modulating signal, it is possible to realize a digital modulator with a null phase delay. Since the proposed ADE-carrier-based digital pulsewidth modulator (DPWM) operates at a variable switching frequency, synchronization strategies between the carrier and the sampling instants may be required for some applications. Reliable synchronism correction architectures are, therefore, proposed and discussed. The developed model is validated through simulation and experimentally on a 27.5-kHz 9-kW single-phase voltage-source inverter case study. The experimental tests include a comparison with the DPWM architecture based on the TTE carrier
Study on the immunogenicity of human class-II-restricted T-cell epitopes: Processing constraints, degenerate binding, and promiscuous recognition
No full textPerformance evaluation of a Shottcky SiC power diode in a boost PFC application
No full textThe performance of a 600 V, 4 A silicon carbide (SiC) Schottky diode (Infineon SDP04S60) is experimentally evaluated. A 300 W boost power factor corrector with average current mode control (PFC) is considered as a key application. Measurements of overall efficiency, switch and diode losses and conducted electromagnetic interference (EMI) are performed both with the SiC diode and with two ultra-fast, soft-recovery, silicon power diodes, namely the RURD460 and the recently presented STTH5R06D. The paper compares the results to quantify the impact of the recovery current reduction provided by SiC diode on these key aspects of the converter behavior
Asymmetric Dual-Edge Digital Pulsewidth Modulator With an Intrinsic Derivative Action
No full textControls involving digital pulsewidth modulators (DPWMs) are usually characterized by a non-negligible phase delay due to the analog-to-digital conversion, sampling time, shape of the carrier, and algorithm computation time. Several strategies are proposed in the literature to mitigate this delay. This article features a full DPWM based on the asymmetric dual-edge carrier that successfully overcomes this drawback. Indeed, the proposed structure allows obtaining a derivative action capable of recovering the usual delay associated with the DPWM structures and providing an additional programmable high-frequency phase boost. Besides the operation's description, this article presents an accurate small-signal analysis of the proposed DPWM architecture. The dynamic model is developed using the describing function approach. The proposed architecture and the developed small-signal model are validated in simulations and by experimental tests
Plasmodium berghei subunit vaccine: repeat synthetic peptide of circumsporozoite protein comprising T- and B-cell epitopes fails to confer immunity.
No full textIn the murine malaria model induced by Plasmodium berghei, we studied the immunogenicity of the repeat region of the circumsporozoite (CS) protein, which is the main target of the antibody response in infected animals. We immunized several strains with a synthetic peptide--Y(DPPPPNPN)3--corresponding to one of the two P. berghei repeat sequences in complete Freund's adjuvant. Only C57BL/6 immune sera reacted with the synthetic peptide in ELISA and with the native CS protein on P. berghei sporozoites, as detected by immunofluorescence. From lymph node cells of immunized C57BL/6 we isolated two repeat-specific T-cell lines which proliferated in the presence of the synthetic peptide or the recombinant CS protein. We analysed the protective role of this repeat-specific response by injecting infectious sporozoites into mice immunized with irradiated sporozoites or with the repeat peptide. The percentage of mice developing parasitaemia was 80-90% in the peptide-immunized group and only 10-20% in the group immunized with irradiated sporozoites. Anti-repeat antibody titres were comparable in the two groups. On the basis of these results, we can conclude that the T- and B-cell response to the CS repeat obtained with this synthetic peptide immunization is not sufficient for a protective immunity
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