28 research outputs found
Comparison of Convective Overshooting Models and Their Impact on Abundances from Integrated Light Spectroscopy of Young ( 3 Gyr) Star Clusters
As part of an ongoing program to measure detailed chemical abundances in
nearby galaxies, we use a sample of young to intermediate age clusters in the
Large Magellanic Cloud with ages of 10 Myr to 2 Gyr to evaluate the effect of
isochrone parameters, specifically core convective overshooting, on Fe
abundance results from high resolution, integrated light spectroscopy. In this
work we also obtain fiducial Fe abundances from high resolution spectroscopy of
the cluster individual member stars. We compare the Fe abundance results for
the individual stars to the results from isochrones and integrated light
spectroscopy to determine whether isochrones with convective overshooting
should be used in our integrated light analysis of young to intermediate age
(10 Myr -3 Gyr) star clusters. We find that when using the isochrones from the
Teramo group, we obtain more accurate results for young and intermediate age
clusters over the entire age range when using isochrones without convective
overshooting. While convective overshooting is not the only uncertain aspect of
stellar evolution, it is one of the most readily parametrized ingredients in
stellar evolution models, and thus important to evaluate for the specific
models used in our integrated light analysis. This work demonstrates that our
method for integrated light spectroscopy of star clusters can provide unique
tests for future constraints on stellar evolution models of young and
intermediate age clusters.Comment: 16 pages, accepted for publication in Ap
Gastrointestinal Tract As Entry Route for Hantavirus Infection
Background: Hantaviruses are zoonotic agents that cause hemorrhagic fevers and
are thought to be transmitted to humans by exposure to aerosolized excreta of
infected rodents. Puumala virus (PUUV) is the predominant endemic hantavirus
in Europe. A large proportion of PUUV-infected patients suffer from
gastrointestinal symptoms of unclear origin. In this study we demonstrate that
PUUV infection can occur via the alimentary tract. Methods: We investigated
susceptibility of the human small intestinal epithelium for PUUV infection and
analyzed the resistance of virions to gastric juice. As model for intestinal
virus translocation we performed infection experiments with human intestinal
Caco-2 monolayers. In animal experiments we infected Syrian hamsters with PUUV
via the intragastric route and tested seroconversion and protective immunity
against subsequent Andes virus challenge. Results: PUUV retained infectivity
in gastric juice at pH >3. The virus invaded Caco-2 monolayers in association
with endosomal antigen EEA1, followed by virus replication and loss of
epithelial barrier function with basolateral virus occurrence. Cellular
disturbance and depletion of the tight junction protein ZO-1 appeared after
prolonged infection, leading to paracellular leakage (leak flux diarrhea).
Moreover, animal experiments led to dose-dependent seroconversion and
protection against lethal Andes virus challenge. Conclusions: We provide
evidence that hantavirus can infect the organism via the alimentary tract and
suggest a novel aspect of hantavirus infection and pathogenesis. Significance:
Hantaviruses are zoonotic pathogens causing severe hemorrhagic fevers
worldwide. They are transmitted to humans by small mammals. To date, these
viruses were thought to infect exclusively through the airborne route by
inhalation of aerosols from infectious animal droppings or by rodent bites. In
our work we could show that the alimentary tract is an alternative path of
infection for hantaviruses, meaning a new association of virus and disease.
These findings have impact on current textbook knowledge and bring many
implications for hantavirus epidemiology and outbreak prevention measures
Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. III. The Large Magellanic Cloud: Fe and Ages
In this paper we refine our method for the abundance analysis of high
resolution spectroscopy of the integrated light of unresolved globular clusters
(GCs). This method was previously demonstrated for the analysis of old (10
Gyr) Milky Way GCs. Here we extend the technique to young clusters using a
training set of 9 GCs in the Large Magellanic Cloud (LMC). Depending on the
signal-to-noise ratio of the data, we use 20-100 Fe lines per cluster to
successfully constrain the ages of old clusters to within a 5 Gyr range,
the ages of 2 Gyr clusters to a 1-2 Gyr range, and the ages of the
youngest clusters (0.05-1 Gyr) to a 200 Myr range. We also demonstrate
that we can measure [Fe/H] in clusters with any age less than 12 Gyrs with
similar or only slightly larger uncertainties (0.1-0.25 dex) than those
obtained for old Milky Way GCs (0.1 dex); the slightly larger uncertainties are
due to the rapid evolution in stellar populations at these ages. In this paper,
we present only Fe abundances and ages. In the next paper in this series, we
present our complete analysis of the elements for which we are able
to measure abundances. For several of the clusters in this sample, there are no
high resolution abundances in the literature from individual member stars; our
results are the first detailed chemical abundances available. The spectra used
in this paper were obtained at Las Campanas with the echelle on the du Pont
Telescope and with the MIKE spectrograph on the Magellan Clay Telescope.Comment: 34 pages, accepted for publication in Ap
Pichinde virus induces microvascular endothelial cell permeability through the production of nitric oxide
This report is the first to demonstrate infection of human endothelial cells by Pichinde virus (PIC). PIC infection induces an upregulation of the inducible nitric oxide synthase gene; as well as an increase in detectable nitric oxide (NO). PIC induces an increase in permeability in endothelial cell monolayers which can be abrogated at all measured timepoints with the addition of a nitric oxide synthase inhibitor, indicating a role for NO in the alteration of endothelial barrier function. Because NO has shown antiviral activity against some viruses, viral titer was measured after addition of the NO synthase inhibitor and found to have no effect in altering virus load in infected EC. The NO synthase inhibition also has no effect on levels of activated caspases induced by PIC infection. Taken together, these data indicate NO production induced by Pichinde virus infection has a pathogenic effect on endothelial cell monolayer permeability
DNA Vaccine-Generated Duck Polyclonal Antibodies as a Postexposure Prophylactic to Prevent Hantavirus Pulmonary Syndrome (HPS)
Andes virus (ANDV) is the predominant cause of hantavirus pulmonary syndrome (HPS) in South America and the only hantavirus known to be transmitted person-to-person. There are no vaccines, prophylactics, or therapeutics to prevent or treat this highly pathogenic disease (case-fatality 35–40%). Infection of Syrian hamsters with ANDV results in a disease that closely mimics human HPS in incubation time, symptoms of respiratory distress, and disease pathology. Here, we evaluated the feasibility of two postexposure prophylaxis strategies in the ANDV/hamster lethal disease model. First, we evaluated a natural product, human polyclonal antibody, obtained as fresh frozen plasma (FFP) from a HPS survivor. Second, we used DNA vaccine technology to manufacture a polyclonal immunoglobulin-based product that could be purified from the eggs of vaccinated ducks (Anas platyrhynchos). The natural “despeciation" of the duck IgY (i.e., Fc removed) results in an immunoglobulin predicted to be minimally reactogenic in humans. Administration of ≥5,000 neutralizing antibody units (NAU)/kg of FFP-protected hamsters from lethal disease when given up to 8 days after intranasal ANDV challenge. IgY/IgYΔFc antibodies purified from the eggs of DNA-vaccinated ducks effectively neutralized ANDV in vitro as measured by plaque reduction neutralization tests (PRNT). Administration of 12,000 NAU/kg of duck egg-derived IgY/IgYΔFc protected hamsters when administered up to 8 days after intranasal challenge and 5 days after intramuscular challenge. These experiments demonstrate that convalescent FFP shows promise as a postexposure HPS prophylactic. Moreover, these data demonstrate the feasibility of using DNA vaccine technology coupled with the duck/egg system to manufacture a product that could supplement or replace FFP. The DNA vaccine-duck/egg system can be scaled as needed and obviates the necessity of using limited blood products obtained from a small number of HPS survivors. This is the first report demonstrating the in vivo efficacy of any antiviral product produced using DNA vaccine-duck/egg system
Progress on the Prevention and Treatment of Hantavirus Disease
Hantaviruses, members of the order Bunyavirales, family Hantaviridae, have a world-wide distribution and are responsible for greater than 150,000 cases of disease per year. The spectrum of disease associated with hantavirus infection include hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) also known as hantavirus cardiopulmonary syndrome (HCPS). There are currently no FDA-approved vaccines or treatments for these hantavirus diseases. This review provides a summary of the status of vaccine and antiviral treatment efforts including those tested in animal models or human clinical trials
Animal Models for the Study of Rodent-Borne Hemorrhagic Fever Viruses: Arenaviruses and Hantaviruses
Human pathogenic hantaviruses and arenaviruses are maintained in nature by persistent infection of rodent carrier populations. Several members of these virus groups can cause significant disease in humans that is generically termed viral hemorrhagic fever (HF) and is characterized as a febrile illness with an increased propensity to cause acute inflammation. Human interaction with rodent carrier populations leads to infection. Arenaviruses are also viewed as potential biological weapons threat agents. There is an increased interest in studying these viruses in animal models to gain a deeper understating not only of viral pathogenesis, but also for the evaluation of medical countermeasures (MCM) to mitigate disease threats. In this review, we examine current knowledge regarding animal models employed in the study of these viruses. We include analysis of infection models in natural reservoirs and also discuss the impact of strain heterogeneity on the susceptibility of animals to infection. This information should provide a comprehensive reference for those interested in the study of arenaviruses and hantaviruses not only for MCM development but also in the study of viral pathogenesis and the biology of these viruses in their natural reservoirs
12,000 NAU/kg of anti-ANDV duck IgY/IgYΔFc protects hamsters from lethal HPS disease.
<p>A) Survival curve of hamsters that were challenged with 200 PFU i.m. of ANDV on day 0 and passively transferred with α-ANDV FFP (8 hamsters per group) or α-ANDV duck IgY/IgYΔFc (16 hamsters per group) on day 5 postinfection. * indicates statistical significance when compared to normal IgY/IgYΔFc treatment. B) α-N ELISA endpoint titers (log<sub>10</sub>) were conducted with sera from surviving hamsters challenged with ANDV in A). GMT for each group are shown.</p
α-ANDV FFP passively transferred on days 5 and 8 protects hamsters from lethal disease and infection.
<p>A) Survival curve of hamsters challenged with 4,000 PFU i.n. of ANDV on day 0, then passively transferred with α-ANDV FFP (30,720 NAU/kg) on days 5, 8, 12 or 15 postinfection. Rabbit sera (administered at 1,920 NAU/kg) were collected 102 days post DNA vaccination <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035996#pone.0035996-Hooper2" target="_blank">[16]</a>. P-values were determined based on comparison to normal serum on matching day. B) α-N ELISA endpoint titers (log<sub>10</sub>) were conducted with sera from surviving hamsters challenged with ANDV in A). GMT for each group are shown. * indicates results are statistically significant when compared to rabbit sera positive control.</p