Asbestos exposures associated with the use and handling of drilling mud additives.

This paper summarizes historical asbestos exposure data collected during the handling of short-fiber chrysotile asbestos that was used as an additive to drilling fluid in oil and gas exploration. A total of 1171 industrial hygiene (IH) personal and area air samples were collected and analyzed from more than 20 drilling rigs between 1972 and 1985. The dataset consists of 1097 short-term samples (<240 min) with more than 80% having sample durations less than 30 min. Average airborne fiber concentrations measured during asbestos handling activities ranged from 0.62 f/cc to 3.39 f/cc using phase-contrast microscopy (PCM). An additional 14 samples were considered long-term samples (>240 min) and there were 60 samples with no reported sample duration. Eight-hour time-weighted average (8-h TWA) results, calculated using short-term samples, along with long-term samples greater than 240 min, did not exceed contemporaneous Occupational Safety and Health Administration (OSHA) permissible exposure limits (PELs). This analysis fills a data gap in the evaluation of asbestos exposures from the use of drilling mud additives (DMAs) that contained chrysotile asbestos.

Association Between Bedroom Particulate Matter Filtration and Changes in Airway Pathophysiology in Children With Asthma.

Importance: Fine particles (particulate matter 2.5 µm [PM2.5]), a ubiquitous air pollutant, can deposit in the small airways that play a vital role in asthma. It appears to be unknown whether the use of a PM2.5 filtration device can improve small airway physiology and respiratory inflammation in children with asthma. Objective: To discover what pathophysiological changes in the small airways are associated with using a PM2.5-removing device in the bedrooms of children with asthma. Design, Setting, and Participants: Children with mild or moderate asthma were enrolled in this double-blind, crossover study. The participants used a true filtration device and a sham filtration device in their bedrooms in a random order for 2 weeks each with a 2-week washout interval. The study was conducted in a suburb of Shanghai, China, during a low-ozone season. Exposures: Ozone and PM2.5 were measured inside bedrooms and outside a window. Main Outcomes and Measures: Impulse oscillometry, spirometry, and fractional exhaled nitric oxide were measured at the beginning and the end of each intervention. Peak expiratory flow was measured twice daily at home. Results: Forty-three children (5-13 years old; 26 boys [60%]) participated. Outdoor 24-hour mean PM2.5 concentrations were moderately high, ranging from 28.6 to 69.8 µg/m3 (median, 53 µg/m3). During true filtration, bedroom PM2.5 concentrations were a mean (SD) of 63.4% (35.9%) lower than during sham filtration. Compared with sham filtration, true filtration was significantly associated with improved airway mechanics, reflected in a 24.4% (95% CI, 11.8%-37.1%) reduction in total airway resistance, a 43.5% (95% CI, 13.7%-73.3%) reduction in small airway resistance, a 22.2% (95% CI, 2.2%-42.2%) reduction in resonant frequency, and a 73.1% (95% CI, 0.3%-145.8%) increase in airway reactance. True filtration was also associated with significant improvements in fractional exhaled nitric oxide (a 27.6% [95% CI, 8.9%-42.4%] reduction) and peak expiratory flow (a 1.6% [95% CI, 0.8%-2.5%] increase). These improvements were significantly associated with bedroom PM2.5 reduction. Improvements in small airway function were nonsignificant (8.4% [95% CI, -1.4% to 18.3%]) in all participants but significant (13.2% [95% CI, 1.2%-25.1%]) in participants without eosinophilic airway inflammation at baseline. No improvements were observed for forced vital capacity, forced expiratory volume during the first second, and the ratio of these in all participants or subgroups. Conclusions and Relevance: Per these results, indoor PM2.5 filtration can be a practical method to improve air flow in an asthmatic lung through improved airway mechanics and function as well as reduced inflammation. This warrants a clinical trial to confirm. Trial Registration: ClinicalTrials.gov Identifier: NCT03282864.

Dissecting the Herpesvirus Architecture by Targeted Proteolysis.

Herpesvirus particles have a complex architecture consisting of an icosahedral capsid that is surrounded by a lipid envelope. Connecting these two components is a layer of tegument that consists of various amounts of 20 or more proteins. The arrangement of proteins within the tegument cannot easily be assessed and instead is inferred from tegument interactions identified in reductionist models. To better understand the tegument architecture, we have developed an approach to probe capsid-tegument interactions of extracellular viral particles by encoding tobacco etch virus (TEV) protease sites in viral structural proteins, along with distinct fluorescent tags in capsid and tegument components. In this study, TEV sites were engineered within the pUL36 large tegument protein, a critical structural element that is anchored directly on the capsid surface. Purified pseudorabies virus extracellular particles were permeabilized, and TEV protease was added to selectively cleave the exposed pUL36 backbone. Interactions with the capsid were assessed in situ by monitoring the fate of the fluorescent signals following cleavage. Although several regions of pUL36 are proposed to bind capsids, pUL36 was found stably anchored to the capsid exclusively at its carboxyl terminus. Two additional tegument proteins, pUL37 and pUS3, were tethered to the capsid via pUL36, whereas the pUL16, pUL47, pUL48, and pUL49 tegument proteins were not stably bound to the capsid.IMPORTANCE Neuroinvasive alphaherpesviruses produce diseases of clinical and economic significance in humans and veterinary animals but are predominantly associated with less serious recurrent disease. Like all viruses, herpesviruses assemble a metastable particle that selectively dismantles during initial infection. This process is made more complex by the presence of a tegument layer that resides between the capsid surface and envelope. Components of the tegument are essential for particle assembly and also serve as critical effectors that promote infection upon entry into cells. How this dynamic network of protein interactions is arranged within virions is largely unknown. We present a molecular approach to dissect the tegument, and with it we begin to tease apart the protein interactions that underlie this complex layer of the virion architecture.

The C Terminus of the Herpes Simplex Virus UL25 Protein Is Required for Release of Viral Genomes from Capsids Bound to Nuclear Pores.

The herpes simplex virus (HSV) capsid is released into the cytoplasm after fusion of viral and host membranes, whereupon dynein-dependent trafficking along microtubules targets it to the nuclear envelope. Binding of the capsid to the nuclear pore complex (NPC) is mediated by the capsid protein pUL25 and the capsid-tethered tegument protein pUL36. Temperature-sensitive mutants in both pUL25 and pUL36 dock at the NPC but fail to release DNA. The uncoating reaction has been difficult to study due to the rapid release of the genome once the capsid interacts with the nuclear pore. In this study, we describe the isolation and characterization of a truncation mutant of pUL25. Live-cell imaging and immunofluorescence studies demonstrated that the mutant was not impaired in penetration of the host cell or in trafficking of the capsid to the nuclear membrane. However, expression of viral proteins was absent or significantly delayed in cells infected with the pUL25 mutant virus. Transmission electron microscopy revealed capsids accumulated at nuclear pores that retained the viral genome for at least 4 h postinfection. In addition, cryoelectron microscopy (cryo-EM) reconstructions of virion capsids did not detect any obvious differences in the location or structural organization for the pUL25 or pUL36 proteins on the pUL25 mutant capsids. Further, in contrast to wild-type virus, the antiviral response mediated by the viral DNA-sensing cyclic guanine adenine synthase (cGAS) was severely compromised for the pUL25 mutant. These results demonstrate that the pUL25 capsid protein has a critical role in releasing viral DNA from NPC-bound capsids.IMPORTANCE Herpes simplex virus 1 (HSV-1) is the causative agent of several pathologies ranging in severity from the common cold sore to life-threatening encephalitic infection. Early steps in infection include release of the capsid into the cytoplasm, docking of the capsid at a nuclear pore, and release of the viral genome into the nucleus. A key knowledge gap is how the capsid engages the NPC and what triggers release of the viral genome into the nucleus. Here we show that the C-terminal region of the HSV-1 pUL25 protein is required for releasing the viral genome from capsids docked at nuclear pores. The significance of our research is in identifying pUL25 as a key viral factor for genome uncoating. pUL25 is found at each of the capsid vertices as part of the capsid vertex-specific component and implicates the importance of this complex for NPC binding and genome release.

The pseudorabies virus protein, pUL56, enhances virus dissemination and virulence but is dispensable for axonal transport.

Neurotropic herpesviruses exit the peripheral nervous system and return to exposed body surfaces following reactivation from latency. The pUS9 protein is a critical viral effector of the anterograde axonal transport that underlies this process. We recently reported that while pUS9 increases the frequency of sorting of newly assembled pseudorabies virus particles to axons from the neural soma during egress, subsequent axonal transport of individual virus particles occurs with wild-type kinetics in the absence of the protein. Here, we examine the role of a related pseudorabies virus protein, pUL56, during neuronal infection. The findings indicate that pUL56 is a virulence factor that supports virus dissemination in vivo, yet along with pUS9, is dispensable for axonal transport.

Pseudorabies Virus Fast Axonal Transport Occurs by a pUS9-Independent Mechanism.

Reactivation from latency results in transmission of neurotropic herpesviruses from the nervous system to body surfaces, referred to as anterograde axonal trafficking. The virus-encoded protein pUS9 promotes axonal dissemination by sorting virus particles into axons, but whether it is also an effector of fast axonal transport within axons is unknown. To determine the role of pUS9 in anterograde trafficking, we analyzed the axonal transport of pseudorabies virus in the presence and absence of pUS9.