SERT II 1980 extended flight thruster experiments

The flight results obtained from mid 1979 through December 1980 are presented. Near continuous solar power in 1979 and 1980 has enabled long periods of thruster endurance testing. Three of four propellant tanks were exhausted with no significant change in thruster system operation before being empty. A new plasma mode thrust was characterized and direct thrust measurements obtained. Other tests, including beam neutralization by various neutralizer sources, give insight to electron conduction across plasmas in space and provide a basis to model neutralization of thruster arrays

Impact of standard test protocols on sporicidal efficacy

Background There has been an increase in the availability of commercial sporicidal formulations. Any comparison of sporicidal data from the literature is hampered by the number of different standard tests available and the use of diverse test conditions including bacterial strains and endospore preparation. Aim To evaluate the effect of sporicidal standard tests on the apparent activity of eight biocides against Clostridium difficile and Bacillus subtilis. Methods The activity of eight biocidal formulations including two oxidizing agents, two aldehydes, three didecyldimethylammonium chloride (DDAC) and amine formulations, and sodium hypochlorite were evaluated using four standard sporicidal tests (BS EN 14347, BS EN13704, ASTM E2197-11, and AOAC MB-15-03) against B. subtilis (ACTC 19659) and C. difficile (NCTC 11209) spores. Findings C. difficile spores were more susceptible to the sporicides than were B. subtilis spores, regardless of the method used. There were differences in sporicidal activity between methods at 5 min but not at 60 min exposure. DDAC and amine-based products were not sporicidal when neutralized appropriately. Neutralization validation was confirmed for these biocides using the reporting format described in the BS EN standard tests, although the raw data appear to indicate that neutralization failed. Conclusion The different methods, whether based on suspension or carrier tests, produced similar sporicidal inactivation data. This study suggests that detailed neutralization validation data should be reported to ensure that neutralization of active spores is effective. Failure to do so may lead to erroneous sporicidal claims

Gold Sterile Ore Acid Generation Evaluation, San Juan Argentina

One of the problems that mining represents in relation to the natural watercourses is the possible formation of what we call acid mine drainage, which consists in the emission or formation of water effluents of great acidity, usually rich in sulfate and with variable contents in heavy metals. The drainage mentioned is developed from the metal sulfide and sulfate leaching. Researches about the creation of acid drainage suggest that the formation of these depends directly on various factors: primary mineralogy (neutralizer sulfides and minerals), water presence (whether), oxygen diffusion, grain size, microbiological interaction (bacterium), among others. To study these variables and to relate them with geological factors, static (Acid-Base Accounting) and dynamic (Humidity Cell) tests have been developed, among others. The mentioned tests are applied to a case of a gold deposit situated in the Province of San Juan, which is currently very argued because of its mining activity due to its leaching process. In the sterile mineral obtained from the process, kinetics tests were carried out in humidity cells to simulate the natural oxidation of the primary mineral samples. In the obtained leaching, pH values closer to neutrality and a limited solution metal presence were detected, indicating the neutralization ability due to the carbonates ores presence.Fil: Bazan Brizuela, Vanesa Lucia. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Investigaciones Mineras; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sarquis, Pedro Edgardo. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Investigaciones Mineras; ArgentinaFil: Brandaleze, Elena. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; Argentin

Studies of bacteriophages induced from Streptococcus cremoris strain R1 : is R1 a double Lysogen? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University, New Zealand

Early studies on Streptococcus cremoris strain R₁ suggested that it was polylysogenic. Later, it was reported that its induced lysates contained bacteriophages (phages) of two types which were believed to differ in their morphology, buoyant densities, immune specificities and in their responses to heterologous antiphage sera. Further work on the strain did not reproduce the above observations, but did often give results which were consistent with it being a double lysogen. This project was an in-depth investigation of phages induced from R₁, in an attempt to establish the single or double lysogenic nature of the strain. Mid-log phase R₁ cells were harvested, washed with homologous antiphage serum and induced to lyse with ultraviolet light (UVL). The resulting phage lysates were analysed on caesium chloride (CsCl) density gradients. Though the OD₂₅₄ (optical density at 254 nm) scans of the gradients detected the presence of only one phage band, p.f.u. (plaque forming unit) profiles of the gradient fractions on indicator strains R₁C and 368 revealed, in addition to the main phage peak, several minor p.f.u. peaks (termed satellite and shoulder peaks) as possible manifestations of different phage types in the R₁ lysates. Further CsCl density gradient analyses of phage stocks and pooled phage fractions of these minor p.f.u. peaks showed that the latter phages were identical with those of the main phage peaks of mean buoyant density of 1.485 g/ml. Further characterization of the phages recovered from the CsCl gradients by neutralization tests with homologous antiphage serum confirmed the existence of only one serological phage type in the R₁ lysates. Final verification of the unity in phage type in R₁ lysates came from SDS-gel electrophoreses of the phages recovered from the different p.f.u. peaks and from lysates, which showed the largely identical gel patterns of their protein components. Host-specificity tests of the phages provided the last piece of evidence for the conclusion that R₁ is a single lysogen, harbouring only one prophage in its genome. Review of past electron-microscopic studies of R₁ lysates substantially support this conclusion. In fact, reconstruction of R₁ by lysogenization of a cured strain (R₁C) yielded a strain (R₁r) which closely resembled the original in lysogenic properties. From the data collected in the course of this work, it was inferred that 368 lysates possibly contained defective phages. An attempt was made to cure 368 of its supposedly defective prophage in the hope of providing a 'cleaner' strain for studying the host-induced variation observed in the R₁C-368 system. Though possible cured derivatives were obtained, they did not prove to be an improvement over the parental strain 368 with respect to their efficiency of plating for R₁ phages. Finally, phage mutant isolation and recombination experiments were attempted in the hope of gaining an insight into the lysogenic system operating in the R₁ cells. Using UVL and nitrous acid (HNO₂) mutagenesis on the temperate ϕr₁/R₁C induced from R₁, about 75 independently arising clear plaque-forming mutants were isolated for mapping experiments. Pairwise crosses between the UVL and HNO₂- induced mutants were performed by coinfecting R₁C cells. Though far from conclusive, the preliminary results obtained indicated a general low occurrence of turbid-plaqued (wild type) phage recombinants, and hence a low frequency of recombination

Ability of vaccine strain induced antibodies to neutralize field isolates of caliciviruses from Swedish cats

Background: Feline calicivirus (FCV) is a common cause of upper respiratory tract disease in cats worldwide. Its characteristically high mutation rate leads to escape from the humoral immune response induced by natural infection and/or vaccination and consequently vaccines are not always effective against field isolates. Thus, there is a need to continuously investigate the ability of FCV vaccine strain-induced antibodies to neutralize field isolates. Methods: Seventy-eight field isolates of FCV isolated during the years 2008–2012 from Swedish cats displaying clinical signs of upper respiratory tract disease were examined in this study. The field isolates were tested for cross-neutralization using a panel of eight anti-sera raised in four pairs of cats following infection with four vaccine strains (F9, 255, G1 and 431). Results: The anti-sera raised against F9 and 255 neutralised 20.5 and 11.5 %, and 47.4 and 64.1 % of field isolates tested, respectively. The anti-sera against the more recently introduced vaccine strains G1 and 431 neutralized 33.3 and 70.5 % and 69.2 and 89.7 %, respectively. Dual vaccine strains displayed a higher cross-neutralization. Conclusions: This study confirms previous observations that more recently introduced vaccine strains induce antibodies with a higher neutralizing capacity compared to vaccine strains that have been used extensively over a long period of time. This study also suggests that dual FCV vaccine strains might neutralize more field isolates compared to single vaccine strains. Vaccine strains should ideally be selected based on updated knowledge on the antigenic properties of field isolates in the local setting, and there is thus a need for continuously studying the evolution of FCV together with the neutralizing capacity of vaccine strain induced antibodies against field isolates at a national and/or regional level

Investigating antibody neutralization of lyssaviruses using lentiviral pseudotypes: a cross-species comparison

Cross-neutralization between rabies virus (RABV) and two European bat lyssaviruses (EBLV-1 and -2) was analysed using lentiviral pseudotypes as antigen vectors. Glycoprotein (G-protein) cDNA from RABV challenge virus standard-11 (CVS-11) and EBLV-1 and -2 were cloned and co-expressed with human immunodeficiency virus (HIV) or murine leukemia virus (MLV) gag–pol and packageable green fluorescent protein (GFP) or luciferase reporter genes in human cells. The harvested lentiviral (HIV) vector infected over 40 % of baby hamster kidney (BHK) target cells, providing high-titre pseudotype stocks. Tests on blinded antibody-positive (n=15) and -negative (n=45) sera, predetermined by the fluorescent antibody virus neutralization (FAVN) test approved by the World Health Organization (WHO) and Office International des Epizooties (OIE), revealed that the CVS-11 pseudotype assay had 100 % concordance with FAVN and strongly correlated with neutralization titres (r2=0.89). Cross-neutralization tests using sera from RABV-vaccinated humans and animals on pseudotypes with CVS-11, EBLV-1 and EBLV-2 envelopes showed that the relative neutralization titres correlated broadly with the degree of G-protein diversity. Pseudotypes have three major advantages over live-virus neutralization tests: (i) they can be handled in low-biohazard-level laboratories; (ii) the use of reporter genes such as GFP or β-galactosidase will allow the assay to be undertaken at low cost in laboratories worldwide; (iii) each assay requires <10 μl serum. This robust microassay will improve our understanding of the protective humoral immunity that current rabies vaccines confer against emerging lyssaviruses, and will be applicable to surveillance studies, thus helping to control the spread of rabies

Variation in dengue virus plaque reduction neutralization testing: systematic review and pooled analysis.

BackgroundThe plaque reduction neutralization test (PRNT) remains the gold standard for the detection of serologic immune responses to dengue virus (DENV). While the basic concept of the PRNT remains constant, this test has evolved in multiple laboratories, introducing variation in materials and methods. Despite the importance of laboratory-to-laboratory comparability in DENV vaccine development, the effects of differing PRNT techniques on assay results, particularly the use of different dengue strains within a serotype, have not been fully characterized.MethodsWe conducted a systematic review and pooled analysis of published literature reporting individual-level PRNT titers to identify factors associated with heterogeneity in PRNT results and compared variation between strains within DENV serotypes and between articles using hierarchical models.ResultsThe literature search and selection criteria identified 8 vaccine trials and 25 natural exposure studies reporting 4,411 titers from 605 individuals using 4 different neutralization percentages, 3 cell lines, 12 virus concentrations and 51 strains. Of 1,057 titers from primary DENV exposure, titers to the exposure serotype were consistently higher than titers to non-exposure serotypes. In contrast, titers from secondary DENV exposures (n = 628) demonstrated high titers to exposure and non-exposure serotypes. Additionally, PRNT titers from different strains within a serotype varied substantially. A pooled analysis of 1,689 titers demonstrated strain choice accounted for 8.04% (90% credible interval [CrI]: 3.05%, 15.7%) of between-titer variation after adjusting for secondary exposure, time since DENV exposure, vaccination and neutralization percentage. Differences between articles (a proxy for inter-laboratory differences) accounted for 50.7% (90% CrI: 30.8%, 71.6%) of between-titer variance.ConclusionsAs promising vaccine candidates arise, the lack of standardized assays among diagnostic and research laboratories make unbiased inferences about vaccine-induced protection difficult. Clearly defined, widely accessible reference reagents, proficiency testing or algorithms to adjust for protocol differences would be a useful first step in improving dengue PRNT comparability and quality assurance

The use of equine influenza pseudotypes for serological screening

Standard assays used for influenza serology present certain practical issues, such as inter-laboratory variability, complex protocols and the necessity for handling certain virus strains in high biological containment facilities. In an attempt to address this, avian and human influenza HA pseudotyped retroviruses have been successfully employed in antibody neutralization assays. In this study we generated an equine influenza pseudotyped lentivirus for serological screening. This was achieved by co-transfection of HEK293T cells with plasmids expressing the haemagglutinin (HA) protein of an H3N8 subtype equine influenza virus strain, HIV gag-pol and firefly luciferase reporter genes and harvesting virus from supernatant. In order to produce infective pseudotype particles it was necessary to additionally co-transfect a plasmid encoding the TMPRSS2 endoprotease to cleave the HA. High titre pseudotype virus (PV) was then used in PV antibody neutralization assays (PVNAs) to successfully distinguish between vaccinated and non-vaccinated equines. The sera were also screened by single radial haemolysis (SRH) assay. There was a 65% correlation between the results of the two assays, with the PVNA assay appearing slightly more sensitive. Future work will extend the testing of the PVNA with a larger number of serum samples to assess sensitivity/specificity, inter/intra-laboratory variability and to define a protective titre

A single mutation in the envelope protein modulates flavivirus antigenicity, stability, and pathogenesis

The structural flexibility or 'breathing' of the envelope (E) protein of flaviviruses allows virions to sample an ensemble of conformations at equilibrium. The molecular basis and functional consequences of virus conformational dynamics are poorly understood. Here, we identified a single mutation at residue 198 (T198F) of the West Nile virus (WNV) E protein domain I-II hinge that regulates virus breathing. The T198F mutation resulted in a ~70-fold increase in sensitivity to neutralization by a monoclonal antibody targeting a cryptic epitope in the fusion loop. Increased exposure of this otherwise poorly accessible fusion loop epitope was accompanied by reduced virus stability in solution at physiological temperatures. Introduction of a mutation at the analogous residue of dengue virus (DENV), but not Zika virus (ZIKV), E protein also increased accessibility of the cryptic fusion loop epitope and decreased virus stability in solution, suggesting that this residue modulates the structural ensembles sampled by distinct flaviviruses at equilibrium in a context dependent manner. Although the T198F mutation did not substantially impair WNV growth kinetics in vitro, studies in mice revealed attenuation of WNV T198F infection. Overall, our study provides insight into the molecular basis and the in vitro and in vivo consequences of flavivirus breathing