Broadly Protective Shigella Vaccine Based on Type III Secretion Apparatus Proteins

Shigella spp. are food- and waterborne pathogens that cause severe diarrheal and dysenteric disease associated with high morbidity and mortality. Individuals most often affected are children under 5 years of age in the developing world. The existence of multiple Shigella serotypes and the heterogenic distribution of pathogenic strains, as well as emerging antibiotic resistance, require the development of a broadly protective vaccine. All Shigella spp. utilize a type III secretion system (TTSS) to initiate infection. The type III secretion apparatus (TTSA) is the molecular needle and syringe that form the energized conduit between the bacterial cytoplasm and the host cell to transport effector proteins that manipulate cellular processes to benefit the pathogen. IpaB and IpaD form a tip complex atop the TTSA needle and are required for pathogenesis. Because they are common to all virulent Shigella spp., they are ideal candidate antigens for a subunit-based, broad-spectrum vaccine. We examined the immunogenicity and protective efficacy of IpaB and IpaD, alone or combined, coadministered with a double mutant heat-labile toxin (dmLT) from Escherichia coli, used as a mucosal adjuvant, in a mouse model of intranasal immunization and pulmonary challenge. Robust systemic and mucosal antibody- and T cell-mediated immunities were induced against both proteins, particularly IpaB. Mice immunized in the presence of dmLT with IpaB alone or IpaB combined with IpaD were fully protected against lethal pulmonary infection with Shigella flexneri and Shigella sonnei. We provide the first demonstration that the Shigella TTSAs IpaB and IpaD are promising antigens for the development of a cross-protective Shigella vaccine

Impact of Detergent on the Biophysical Properties and Immune Response of the IpaDB Fusion Protein, a Candidate Subunit Vaccine against Shigella spp.

Shigella spp. are causative agents of bacillary dysentery, a human illness with high global morbidity levels, particularly among elderly and infant populations. Shigella infects via the fecal-oral route, and its virulence is dependent upon a type III secretion system (T3SS). Two components of the exposed needle tip complex of the Shigella T3SS, invasion plasmid antigen D (IpaD) and IpaB, have been identified as broadly protective antigens in the mouse lethal pneumonia model. A recombinant fusion protein (DB fusion) was created by joining the coding sequences of IpaD and IpaB. The DB fusion is coexpressed with IpaB\u27s cognate chaperone, IpgC, for proper recombinant expression. The chaperone can then be removed by using the mild detergents octyl oligooxyethelene (OPOE) or N,N-dimethyldodecylamine N-oxide (LDAO). The DB fusion in OPOE or LDAO was used for biophysical characterization and subsequent construction of an empirical phase diagram (EPD). The EPD showed that the DB fusion in OPOE is most stable at neutral pH below 55°C. In contrast, the DB fusion in LDAO exhibited remarkable thermal plasticity, since this detergent prevents the loss of secondary and tertiary structures after thermal unfolding at 90°C, as well as preventing thermally induced aggregation. Moreover, the DB fusion in LDAO induced higher interleukin-17 secretion and provided a higher protective efficacy in a mouse challenge model than did the DB fusion in OPOE. These data indicate that LDAO might introduce plasticity to the protein, promoting thermal resilience and enhanced protective efficacy, which may be important in its use as a subunit vaccine

Removal of nutrients and pesticides from agricultural runoff using microalgae and cyanobacteria

The use of pesticides in agriculture has ensured the production of different crops. However, pesticides have become an emerging public health problem for Latin American countries due to their excessive use, inadequate application, toxic characteristics, and minimal residue control. The current project evaluates the ability of two strains of algae (Chlorella and Scenedesmus sp.) and one cyanobacteria (Hapalosyphon sp.) to remove excess pesticides and other nutrients present in runoff water from rice production. Different concentrations of wastewater and carbon sources (Na2CO3 and NaHCO3 ) were evaluated. According to the results, all three strains can be grown in wastewater without dilution (100%), with a biomass concentration comparable to a synthetic medium. All three strains significantly reduced the concentration of NO3 and PO4 (95 and 85%, respectively), with no difference between Na2CO3 or NaHCO3 . Finally, Chlorella sp. obtained the highest removal efficiency of the pesticide (Chlorpyrifos), followed by Scenedesmus and Hapalosyphon sp. (100, 75, and 50%, respectively). This work shows that it is possible to use this type of waste as an alternative source of nutrients to obtain biomass and metabolites of interest, such as lipids and carbohydrates, to produce biofuels

The Sensitivity of HAWC to High-Mass Dark Matter Annihilations

The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC will observe gamma rays and cosmic rays with an array of water Cherenkov detectors. The full HAWC array is scheduled to be operational in Spring 2015. In this paper, we study the HAWC sensitivity to the gamma-ray signatures of high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be sensitive to diverse searches for dark matter annihilation, including annihilation from extended dark matter sources, the diffuse gamma-ray emission from dark matter annihilation, and gamma-ray emission from non-luminous dark matter subhalos. Here we consider the HAWC sensitivity to a subset of these sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the Galactic center. We simulate the HAWC response to gamma rays from these sources in several well-motivated dark matter annihilation channels. If no gamma-ray excess is observed, we show the limits HAWC can place on the dark matter cross-section from these sources. In particular, in the case of dark matter annihilation into gauge bosons, HAWC will be able to detect a narrow range of dark matter masses to cross-sections below thermal. HAWC should also be sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The constraints placed by HAWC on the dark matter cross-section from known sources should be competitive with current limits in the mass range where HAWC has similar sensitivity. HAWC can additionally explore higher dark matter masses than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR

The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula

MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent a series of upgrades, involving the exchange of the MAGIC-I camera and its trigger system, as well as the upgrade of the readout system of both telescopes. We use observations of the Crab Nebula taken at low and medium zenith angles to assess the key performance parameters of the MAGIC stereo system. For low zenith angle observations, the standard trigger threshold of the MAGIC telescopes is ~50GeV. The integral sensitivity for point-like sources with Crab Nebula-like spectrum above 220GeV is (0.66+/-0.03)% of Crab Nebula flux in 50 h of observations. The angular resolution, defined as the sigma of a 2-dimensional Gaussian distribution, at those energies is < 0.07 degree, while the energy resolution is 16%. We also re-evaluate the effect of the systematic uncertainty on the data taken with the MAGIC telescopes after the upgrade. We estimate that the systematic uncertainties can be divided in the following components: < 15% in energy scale, 11-18% in flux normalization and +/-0.15 for the energy spectrum power-law slope.Comment: 21 pages, 25 figures, accepted for publication in Astroparticle Physic

Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008

The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays by MAGIC in spring 2007. Before that the source was little studied in different wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio observatory, Bell and KVA optical telescopes and the Swift and AGILE satellites. MAGIC observations span from March to May, 2008 for a total of 27.9 hours, of which 19.4 hours remained after quality cuts. The light curve showed no significant variability. The differential VHE spectrum could be described with a power-law function. Both results were similar to those obtained during the discovery. Swift XRT observations revealed an X-ray flare, characterized by a harder when brighter trend, as is typical for high synchrotron peak BL Lac objects (HBL). Strong optical variability was found during the campaign, but no conclusion on the connection between the optical and VHE gamma-ray bands could be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike concluded in previous work based on nonsimultaneous data, and is well described by a standard one zone synchrotron self Compton model. We also performed a study on the source classification. While the optical and X-ray data taken during our campaign show typical characteristics of an HBL, we suggest, based on archival data, that 1ES 1011+496 is actually a borderline case between intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA

Probing the very-high-energy gamma-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes

PG 1553+113 is a very-high-energy (VHE, $E>100\,\mathrm{GeV}$) $\gamma$-ray emitter classified as a BL Lac object. Its redshift is constrained by intergalactic absorption lines in the range $0.4<z<0.58$. The MAGIC telescopes have monitored the source's activity since 2005. In early 2012, PG 1553+113 was found in a high-state, and later, in April of the same year, the source reached its highest VHE flux state detected so far. Simultaneous observations carried out in X-rays during 2012 April show similar flaring behaviour. In contrast, the $\gamma$-ray flux at $E<100\,\mathrm{GeV}$ observed by Fermi-LAT is compatible with steady emission. In this paper, a detailed study of the flaring state is presented. The VHE spectrum shows clear curvature, being well fitted either by a power law with an exponential cut-off or by a log-parabola. A simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE $\gamma$-ray spectrum is rejected with a high significance (fit probability P=2.6 $\times 10^{-6}$). The observed curvature is compatible with the extragalactic background light (EBL) imprint predicted by current generation EBL models assuming a redshift $z\sim0.4$. New constraints on the redshift are derived from the VHE spectrum. These constraints are compatible with previous limits and suggest that the source is most likely located around the optical lower limit, $z=0.4$, based on the detection of Ly$\alpha$ absorption. Finally, we find that the synchrotron self-Compton (SSC) model gives a satisfactory description of the observed multi-wavelength spectral energy distribution during the flare.Comment: 13 pages, 7 figures, accepted for publication in MNRA