Determination of the 50% human infectious dose for Norwalk virus.

Background:  Noroviruses are the most common cause of gastroenteritis in the United States. An understanding of the infectious dose of these viruses is important for risk assessment studies.

Methods:  Healthy adults were enrolled in a randomized, double-blind, placebo-controlled evaluation of different dosages of Norwalk virus.

Magnitude, decadal changes, and impact of regional background ozone transported into the greater Houston, Texas, area.

Two independent analyses of the daily maximum 8 h average ozone concentrations measured during the high ozone season (May through October) at Continuous Ambient Monitoring Stations are used to quantify the regional background ozone transported into the Houston-Galveston-Brazoria (HGB) area. The dependence on wind direction is examined, and long-term trends are determined using measurements made between 1998 and 2012. Both analyses show that the regional background ozone has declined during periods of continental outflow: i.

Synthesis, Activity and Structure-Activity Relationship of Noroviral Protease Inhibitors.

The protease of norovirus, an important human pathogen, is essential for the viral replication and, therefore, represents a potential drug target. A series of tripeptide-based inhibitors of the protease were designed, synthesized and tested, among which several potent inhibitors were identified with K values as low as 75 nM. The structure-activity relationships of these inhibitors are discussed.

Epidemiology of human noroviruses and updates on vaccine development.

Purpose Of Review: Noroviruses (NoVs) are the most common cause of epidemic and sporadic cases of acute gastroenteritis worldwide. This review summarizes recent NoV disease burden estimates, epidemiology findings and provides an update on virus-like particle (VLP) vaccine studies.

Recent Findings: NoVs are the leading cause of food-borne gastroenteritis and are replacing rotavirus as the predominant gastrointestinal pathogen in pediatric populations.

A novel form of rotavirus NSP2 and phosphorylation-dependent NSP2-NSP5 interactions are associated with viroplasm assembly.

Rotavirus (RV) replication occurs in cytoplasmic inclusions called viroplasms whose formation requires the interactions of RV proteins NSP2 and NSP5; however, the specific role(s) of NSP2 in viroplasm assembly remains largely unknown. To study viroplasm formation in the context of infection, we characterized two new monoclonal antibodies (MAbs) specific for NSP2. These MAbs show high-affinity binding to NSP2 and differentially recognize distinct pools of NSP2 in RV-infected cells; a previously unrecognized cytoplasmically dispersed NSP2 (dNSP2) is detected by an N-terminal binding MAb, and previously known viroplasmic NSP2 (vNSP2) is detected by a C-terminal binding MAb.

Activation of the endoplasmic reticulum calcium sensor STIM1 and store-operated calcium entry by rotavirus requires NSP4 viroporin activity.

Rotavirus nonstructural protein 4 (NSP4) induces dramatic changes in cellular calcium homeostasis. These include increased endoplasmic reticulum (ER) permeability, resulting in decreased ER calcium stores and activation of plasma membrane (PM) calcium influx channels, ultimately causing a 2- to 4-fold elevation in cytoplasmic calcium. Elevated cytoplasmic calcium is absolutely required for virus replication, but the underlying mechanisms responsible for calcium influx remain poorly understood.

Fine particulate matter and incident cognitive impairment in the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort.

Studies of the effect of air pollution on cognitive health are often limited to populations living near cities that have air monitoring stations. Little is known about whether the estimates from such studies can be generalized to the U.S.

MHCI requires MEF2 transcription factors to negatively regulate synapse density during development and in disease.

Major histocompatibility complex class I (MHCI) molecules negatively regulate cortical connections and are implicated in neurodevelopmental disorders, including autism spectrum disorders and schizophrenia. However, the mechanisms that mediate these effects are unknown. Here, we report a novel MHCI signaling pathway that requires the myocyte enhancer factor 2 (MEF2) transcription factors.

Prevention of cholestasis in the murine rotavirus-induced biliary atresia model using passive immunization and nonreplicating virus-like particles.

Biliary atresia (BA) is a neonatal cholangiopathy of unknown etiology that results in obliteration of bile ducts and is the primary indication for liver transplant in children. A murine model of BA, which involves infecting newborn mice with rhesus rotavirus (RRV) and leads to development of an obstructive cholangiopathy, has provided a model to assess measures to prevent and treat BA. We used this mouse model of RRV-induced BA to determine if passive immunization of pups using maternal immunization [injection of dams with non-replicating rotavirus (RV) virus-like particles (VLPs) or live RRV] or injection of pups with RV immune serum would protect these RRV-infected neonates from developing BA (measured using cholestasis).

Noroviruses: The Most Common Pediatric Viral Enteric Pathogen at a Large University Hospital After Introduction of Rotavirus Vaccination.

We conducted an 8.5-year study examining enteric viruses at Texas Children's Hospital (TCH) before and after rotavirus vaccine introduction. Norovirus prevalence was 10.

A tuneable array of unique steady-state microfluidic gradients.

We report an on-chip gradient generator that has been designed, modelled, fabricated, and characterized to facilitate temporal tuning of several unique gradients in parallel for multiple applications. This design allows for steady state programming of the intensities across multiple orders of magnitude while producing exponential, linear, and logarithmic gradient profiles. The magnitude of the gradients is controlled through regulating the ratio of the two on-chip flow inlets without the need for valves or other active mixers.

Lack of norovirus replication and histo-blood group antigen expression in 3-dimensional intestinal epithelial cells.

Noroviruses (NoVs) are a leading cause of gastroenteritis worldwide. An in vitro model for NoV replication remains elusive, making study of the virus difficult. A previous study, which used a 3-dimensional (3-D) intestinal model derived from INT-407 cells reported NoV replication and extensive cytopathic effects (CPE).

The VP8* domain of neonatal rotavirus strain G10P[11] binds to type II precursor glycans.

Naturally occurring bovine-human reassortant rotaviruses with a P[11] VP4 genotype exhibit a tropism for neonates. Interaction of the VP8* domain of the spike protein VP4 with sialic acid was thought to be the key mediator for rotavirus infectivity. However, recent studies have indicated a role for nonsialylated glycoconjugates, including histo-blood group antigens (HBGAs), in the infectivity of human rotaviruses.

Exposure to human and bovine noroviruses in a birth cohort in southern India from 2002 to 2006.

Human and bovine norovirus virus-like particles were used to evaluate antibodies in Indian children at ages 6 and 36 months and their mothers. Antibodies to genogroup II viruses were acquired early and were more prevalent than antibodies to genogroup I. Low levels of IgG antibodies against bovine noroviruses indicate possible zoonotic transmission.

Identification and characterization of a peptide affinity reagent for detection of noroviruses in clinical samples.

Norovirus (NoV) is the most common agent of nonbacterial epidemic gastroenteritis and is estimated to cause 21 million cases of the disease in the United States annually. The antigen enzyme-linked immunosorbent assays (ELISAs) currently available for NoV diagnosis detect only certain strains and are approved for use in the United States only in epidemics where NoV is suspected. There is a clear need for simpler, more rapid, and more reliable diagnostic tools for the detection of NoV.

Viroporin-mediated calcium-activated autophagy.

Autophagy is a cellular response activated by many pathogens, but the mechanism of activation is largely unknown. Recently we showed for the first time that rotavirus initiates the autophagy pathway through a calcium-mediated mechanism. Expression of the rotavirus-encoded NSP4, a pore-forming protein (viroporin), elicits the release of endoplasmic reticulum (ER) lumenal calcium into the cytoplasm of the infected cell.

Norwalk Virus Minor Capsid Protein VP2 Associates within the VP1 Shell Domain.

The major capsid protein of norovirus VP1 assembles to form an icosahedral viral particle. Despite evidence that the Norwalk virus (NV) minor structural protein VP2 is present in infectious virions, the available crystallographic and electron cryomicroscopy structures of NV have not revealed the location of VP2. In this study, we determined that VP1 associates with VP2 at the interior surface of the capsid, specifically with the shell (S) domain of VP1.

Structural basis of substrate specificity and protease inhibition in Norwalk virus.

Norwalk virus (NV), the prototype human calicivirus, is the leading cause of nonbacterial acute gastroenteritis. The NV protease cleaves the polyprotein encoded by open reading frame 1 of the viral genome at five nonhomologous sites, releasing six nonstructural proteins that are essential for viral replication. The structural details of how NV protease recognizes multiple substrates are unclear.

Estimating ground-level PM(2.5) concentrations in the southeastern U.S. using geographically weighted regression.

Most of currently reported models for predicting PM(2.5) concentrations from satellite retrievals of aerosol optical depth are global methods without considering local variations, which might introduce significant biases into prediction results. In this paper, a geographically weighted regression model was developed to examine the relationship among PM(2.

Autophagy hijacked through viroporin-activated calcium/calmodulin-dependent kinase kinase-β signaling is required for rotavirus replication.

Autophagy is a cellular degradation process involving an intracellular membrane trafficking pathway that recycles cellular components or eliminates intracellular microbes in lysosomes. Many pathogens subvert autophagy to enhance their replication, but the mechanisms these pathogens use to initiate the autophagy process have not been elucidated. This study identifies rotavirus as a pathogen that encodes a viroporin, nonstructural protein 4, which releases endoplasmic reticulum calcium into the cytoplasm, thereby activating a calcium/calmodulin-dependent kinase kinase-β and 5' adenosine monophosphate-activated protein kinase-dependent signaling pathway to initiate autophagy.

A time-resolved immunoassay to measure serum antibodies to the rotavirus VP6 capsid protein.

The rotavirus (RV) inner capsid protein VP6 is widely used to evaluate immune response during natural infection and in vaccine studies. Recombinant VP6 from the most prevalent circulating rotavirus strains in each subgroup (SG) identified in a birth cohort of children in southern India [SGII (G1P[8]) and SGI (G10P[11])] were produced. The purified proteins were used to measure VP6-specific antibodies in a Dissociation-Enhanced Lanthanide Fluorometric Immunoassay (DELFIA).

Antibody responses to norovirus genogroup GI.1 and GII.4 proteases in volunteers administered Norwalk virus.

An assay was developed to detect antibodies against two norovirus proteases among participants in a Norwalk virus (GI.1) challenge study. Prechallenge seroprevalence was lower against the protease from the homologous GI.

Optimization of multiplexed PCR on an integrated microfluidic forensic platform for rapid DNA analysis.

This study reports the design, prototyping, and assay development of multiplexed polymerase chain reaction (PCR) on a plastic microfluidic device. Amplification of 17 DNA loci is carried out directly on-chip as part of a system for continuous workflow processing from sample preparation (SP) to capillary electrophoresis (CE). For enhanced performance of on-chip PCR amplification, improved control systems have been developed making use of customized Peltier assemblies, valve actuators, software, and amplification chemistry protocols.

Secretory pathway antagonism by calicivirus homologues of Norwalk virus nonstructural protein p22 is restricted to noroviruses.

Background: Our previous report that the Norwalk virus nonstructural protein p22 is an antagonist of the cellular secretory pathway suggests a new aspect of norovirus/host interaction. To explore conservation of function of this highly divergent calicivirus protein, we examined the effects of p22 homologues from four human and two murine noroviruses, and feline calicivirus on the secretory pathway.

Findings: All human noroviruses examined induced Golgi disruption and inhibited protein secretion, with the genogroup II.