Solution Structure of the Immunodominant Domain of Protective Antigen GNA1870 of Neisseria meningitidis

GNA1870, a 28-kDa surface-exposed lipoprotein of Neisseria meningitidis recently discovered by reverse vaccinology, is one of the most potent antigens of Meningococcus and a promising candidate for a universal vaccine against a devastating disease. Previous studies of epitope mapping and genetic characterization identified residues critical for bactericidal response within the C-terminal domain of the molecule. To elucidate the conformation of protective epitopes, we used NMR spectroscopy to obtain the solution structure of the immunodominant 18-kDa C-terminal portion of GNA1870. The structure consists of an eight-stranded antiparallel beta-barrel overlaid by a short alpha-helix with an unstructured N-terminal end. Residues previously shown to be important for antibody recognition were mapped on loops facing the same ridge of the molecule. The sequence similarity of GNA1870 with members of the bacterial transferrin receptor family allows one to predict the folding of this class of well known bacterial antigens, providing the basis for the rational engineering of high affinity B cell epitopes

Molecular engineering of Ghfp, the gonococcal orthologue of neisseria meningitidis factor H binding protein

Knowledge of the sequences and structures of proteins produced by microbial pathogens is continuously increasing. Besides offering the possibility of unraveling the mechanisms of pathogenesis at the molecular level, structural information provides new tools for vaccine development, such as the opportunity to improve viral and bacterial vaccine candidates by rational design. Structure-based rational design of antigens can optimize the epitope repertoire in terms of accessibility, stability, and variability. In the present study, we used epitope mapping information on the well-characterized antigen of Neisseria meningitidis factor H binding protein (fHbp) to engineer its gonococcal homologue, Ghfp. Meningococcal fHbp is typically classified in three distinct antigenic variants. We introduced epitopes of fHbp variant 1 onto the surface of Ghfp, which is naturally able to protect against meningococcal strains expressing fHbp of variants 2 and 3. Heterologous epitopes were successfully transplanted, as engineered Ghfp induced functional antibodies against all three fHbp variants. These results confirm that structural vaccinology represents a successful strategy for modulating immune responses, and it is a powerful tool for investigating the extension and localization of immunodominant epitopes

An integrated electronic meniscus sensor for measurement of evaporative flow

This paper presents an electronic sensor for evaporative flow measurements in open microfluidics Lab-on-Chips. The flow counteracts the gravitational fall of cells in the culture media. Particular attention has been paid in the design to allow the integration of the sensor in biochips composed of large arrays of microfluidic channels for parallel bioassays. Simple Aluminium electrodes produced with a biocompatible technology are used for impedance measurements of the meniscus height h at the outlet of a microchannel. The correlation between the electrical measurement and h is demonstrated with a resolution of 10μm. A second correlation between h and the evaporation rate ER is investigated through optical inspection at different temperatures. Experiments show that the flow rates produced and measured in the device range from 0.16 to 0.32 ul/h at room temperature and 35% relative humidity

A Simple Focused Crawler

A focused crawler may be described as a crawler which returns relevant web pages on a given topic in traversing the web. There are a number of issues related to existing focused crawlers, in particular the ability to ``tunnel'' through lowly ranked pages in the search path to highly ranked pages related to a topic which might re-occur further down the search path. We will introduce a simple focused crawler, which is described by two parameters, viz., degree of relatedness, and depth. Both provide an opportunity for the crawler to ``tunnel'' through lowly ranked pages. Results from initial experiments are promising and motivate for further research

Epidemiologic Survey on Toxoplasma gondii and Trichinella pseudospiralis Infection in Corvids from Central Italy

Free-ranging corvids—678 magpies (Pica pica) and 120 hooded crows (Corvus cornix) from nine protected areas of the Pisa province (central Italy)—were examined for Toxoplasma gondii and Trichinella pseudospiralis. The intracardiac blood clots from 651 magpies and 120 hooded crows were serologically examined for T. gondii. The DNA extracted from the hearts of seropositive birds was then used to perform a nested PCR for the amplification of the T. gondii B1 gene and for genotyping for SAG genetic markers. Breast muscle samples from 678 magpies and 91 hooded crows were tested by an artificial digestion method for Trichinella. Data were statistically analyzed. Forty-five (5.8%—41 magpies and four hooded crows) out of the 771 examined animals scored seropositive for T. gondii, with titers ranging from 1:25 to 1:100. T. gondii DNA was detected in 15 of the 45 positive birds and T. gondii genotypes II and III were identified. No positivity for T. pseudospiralis was found. No significant differences between the two species of corvids and among the different areas of origin were observed for seropositivity to T. gondii. This is the first extensive study on both T. gondii and T. pseudospiralis in magpies and hooded crows, as well as the first detection of T. gondii SAG genotypes in magpies

EVALUATION OF TRICHINELLA PSEUDOSPIRALIS AND TOXOPLASMA GONDII INFECTION IN FREE RANGING CORVIDS FROM THE PROVINCE OF PISA

Magpies (Pica pica) and hooded crows (Corvus corone cornix) are scavenger birds feeding on carcasses, arthropods, vegetables, small preys and food waste. In Italy, they tend to remain in the same territory and establish large populations both in urban and rural environments. For these reasons, these birds have a potential role as sentinels for the spread of Toxoplasma gondii in a given area. Trichinella pseudospiralis has been previously reported in corvids. In the present study, 798 free ranging corvids, including 678 magpies and 120 hooded crows deceased following a program of population size reduction of the province of Pisa, were examined for T. pseudospiralis and T. gondii infections. More specifically, sera from 651 magpies and 120 hooded crows were examined by IFAT for antibodies specific to T. gondii. In seropositive birds, the heart was homogenized and DNA was extracted to perform a nested polymerase chain reaction (nPCR) detection method for B1 gene of T. gondii and genotyping for SAG. In the case of Trichinella, breast muscle samples (50 g each) from 678 magpies and 91 hooded crows were tested by an artificial digestion method. After digestion, eventually recovered larvae were processed for molecular typing. Data were statistically analysed (p <0.05). Forty-five, 41 magpies and 4 hooded crows, out of the 771 examined animals (5.8%) scored positive for T. gondii with antibody titers ranging from 1: 25 to 1:100. Seropositivity to T. gondii was not statistically different between magpies and hooded crows. T. gondii DNA was detected in 15 out of 45 heart samples and the occurrence of genotypes II and III of T. gondii was evidenced. No Trichinella larvae were detected in muscle samples. This is the first report of T. gondii infection in corvids in Italy

Characterisation of submarine depression trails driven by upslope migrating cyclic steps: insights from the Ceará Basin (Brazil)

Circular to elliptical topographic depressions, isolated or organized in trails, have been observed on the modern seabed in different contexts and water depths. Such features have been alternatively interpreted as pockmarks generated by fluid flow, as sediment waves generated by turbidity currents, or as a combination of both processes. In the latter case, the dip of the slope has been hypothesized to control the formation of trails of downslope migrating pockmarks. In this study, we use high-quality 3D seismic data from the offshore Ceará Basin (Equatorial Brazil) to examine vertically stacked and upslope-migrating trails of depressions visible at the seabed and in the subsurface. Seismic reflection terminations and stratal architecture indicate that these features are formed by cyclic steps generated by turbidity currents, while internal amplitude anomalies point to the presence of fluid migration. Amplitude Versus Offset analysis (AVO) performed on partial stacks shows that the investigated anomalies do not represent hydrocarbon indicators. Previous studies have suggested that the accumulation of permeable and porous sediments in the troughs of vertically stacked cyclic steps may create vertical pathways for fluid migration, and we propose that this may have facilitated the upward migration of saline pore water due to fluid buoyancy. The results of this study highlight the importance of gravity-driven processes in shaping the morphology of the Ceará Basin slope and show how non-hydrocarbon fluids may interact with vertically stacked cyclic step

Structure of the C-terminal Domain of Neisseria Heparin Binding Antigen (NHBA), One of the Main Antigens of a Novel Vaccine against Neisseria meningitidis*

Background: NHBA, a surface-exposed lipoprotein from Neisseria meningitidis, is part of a multicomponent vaccine against serogroup B meningitis