Croup

Far from being stiff and pointy, a coronavirus's infectious spikes are shaped like chicken drumsticks with the meaty part facing out, and the meaty part can tilt every which way on its slender stalk. A new study suggests that disabling those hinges could block infection. A coronavirus uses protein "spikes" to grab and infect cells. Despite their name, those spikes aren't stiff and pointy. They're shaped like chicken drumsticks with the meaty part facing out, and the meaty part can tilt every which way on its slender stalk. That ability to tilt, it turns out, affects how successfully the spike can infect a cell. Now researchers from the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, along with collaborators at three more universities, have obtained high-resolution images of intact coronavirus spikes on the surfaces of virus particles; identified a tiny hinge surrounded by sugar molecules that allows the spike's glob-like "crown" to bend on its stalk; and measured how far it can tilt in any direction. While the study was carried out on a much less dangerous cousin of SARS-CoV-2, the coronavirus that causes COVID-19, it has implications for COVID-19, too, since both viruses bind to the same receptor on a cell's surface to initiate infection, said Jing Jin, a biologist at Vitalant Research Institute and adjunct assistant professor at the University of California, San Francisco who performed virology experiments for the study. The results, she said, suggest that disabling the spike's hinges could be a good way to prevent or treat a wide range of coronavirus infections. The team also discovered that each coronavirus particle is unique, both in its underlying shape and its display of spikes. Some are spherical, some are not; some bristle with spikes while others are nearly bald. "The spikes are floppy and move around, and we used a combination of tools to explore all their possible angles and orientations," said Greg Pintilie, a Stanford scientist who developed detailed 3D models of the virus and its spikes. Seen up close, he said, each spike is different from all the rest, mainly in its direction and degree of tilting. The research team reported its findings in Nature Communications. "Since the pandemic started, most studies have looked at the structures of coronavirus spike proteins that were not attached to the virus itself," said Wah Chiu, a professor at SLAC and Stanford and co-director of the Stanford-SLAC Cryo-EM facilities where the imaging was done. "These are the first images made of the spikes of this strain of coronavirus while they're still attached to the virus particles." SARS-CoV-2's more benign cousin The study has roots in the early days of the pandemic, when research at SLAC shut down except for work aimed at understanding, preventing and treating COVID-19 infections. Because experiments with the actual SARS-CoV-2 virus can only take place in high-level (BSL3) biosafety labs, many scientists chose to work with more benign members of the coronavirus family. Chiu and his colleagues selected human coronavirus NL63 as their subject. It causes up to 10% of human respiratory infections, mainly in children and immunocompromised people, with symptoms ranging from mild coughs and sniffles to bronchitis and croup. In 2020, Chiu said, the team used cryogenic electron microscopy (cryo-EM) and computational analysis to image the crowns of NL63 spikes with near-atomic resolution. But because a spike's stalk is much thinner than its crown, they were not able to get clear, high-resolution images of both at once. Zooming in on spikes This study combined information gleaned from a series of experiments to get a much more complete picture. First, Stanford graduate student David Chmielewski used cryogenic electron tomography (cryo-ET) to combine cryo-EM images of viruses that were taken from different angles into high-resolution 3-D images of more than a hundred NL63 particles. SLAC senior scientist Michael Schmid plugged those images into a 3D visualization tool and discovered that each of a particle's spikes was bent in a unique way. Another SLAC scientist, Muyuan Chen, used advanced image reconstruction to create maps showing the average density of the spikes' crowns and stalks. Zooming in on one of those spikes, biological chemist Lance Wells at the University of Georgia used a technique called mass spectrometry to pinpoint the site-specific chemical compositions of the 39 sugar chains attached to each of the spike's three identical proteins. Finally, Abhishek Singharoy, a computational biophysicist at Arizona State University, and his student, Eric Wilson, integrated all those measurements into atomic models of the spikes' crowns and stalks at different bending angles, and carried out further simulations to see how far and how freely a spike can bend. "It turns out that no matter what, the spikes have a preferred bending angle of about 50 degrees," Chiu said, "and they can tilt up to 80 degrees in any direction in the simulation, which matches well with our cryo-ET experimental observations." The bending occurred at a place on the stalk, just below the crown, where a particular cluster of sugar molecules clung to the protein, forming a hinge. Computer simulations suggested that changes in the structure of this hinge would affect its ability to bend, and lab experiments went one step further: They showed that mutations in the protein part of the hinge made the spike much less infectious. This suggests that targeting the hinge could provide an avenue to fight the virus. "People working on the more dangerous coronaviruses, including MERS-CoV and SARS-CoV-2, have identified a region equivalent to this one and discovered antibodies targeting this region," Jin said. "That tells us it's a critical region that is highly conserved, meaning that it has stayed much the same over the course of evolution. So maybe by targeting this region in all coronaviruses, we can come up with a universal therapy or vaccine." This work was supported by the National Virtual Biotechnology Laboratory, a group of Department of Energy national laboratories that was focused on responding to the COVID-19 pandemic with funding provided by the Coronavirus CARES Act; the National Science Foundation; and the National Institutes of Health.

TUESDAY, Aug. 1, 2023 -- A 30-minute exposure to outdoor cold air is beneficial for reducing clinical symptoms in children with croup as an adjunct to oral dexamethasone , according to a study published online Aug. 1 in Pediatrics . Johan N. Siebert, M.D., from Geneva Children's Hospital in Switzerland, and colleagues conducted an open-label, single-center, randomized trial enrolling children aged 3 months to 10 years with croup and a Westley Croup Score (WCS) ≥2 attending a tertiary pediatric emergency department. Immediately after triage and administration of single-dose oral dexamethasone, patients were randomly assigned to a 30-minute exposure to outdoor cold (<10 degrees Celsius) atmospheric air or to indoor ambient room air (59 participants in each group). The researchers found that at 30 minutes, 49.2 and 23.7 percent of the participants in the outdoor and indoor groups, respectively, showed a decrease in WCS ≥2 points from baseline (risk difference, 25.4 percent). The greatest benefit from the intervention at 30 minutes was seen for patients with moderate croup (risk difference, 46.1 percent). "This randomized controlled trial supports the benefits of exposure to outdoor cold air on croup symptoms in children with mild to moderate croup in the first 30 minutes before the onset of action of steroids," the authors write. Abstract/Full Text Posted August 2023

TUESDAY, Aug. 1, 2023 -- Pediatricians have suspected it for years, and now a new study may be proving them right: Cold air really can help ease children's croup symptoms. Croup is a common childhood illness that usually starts as an ordinary cold. It arises when the infection causes swelling around the voice box (larynx) and wind pipe (trachea), leading to some distinctive croup symptoms: a cough that sounds like a seal's bark and a high-pitched "creaky" or whistling noise when a child inhales (what doctors call stridor). Fortunately, most cases of croup are mild. And pediatricians have long told parents they can try some old-fashioned tricks for milder croup symptoms: running a hot shower and standing with their child in the steamy bathroom; standing in front of an open refrigerator freezer, or wrapping their child in blankets and going outside in the chilly air for a bit. "The common denominator there is the moist air," said Dr. Mike Patrick , an emergency medicine physician at Nationwide Children's Hospital in Columbus, Ohio. "Indoor air, especially in the winter, is dry." He said pediatricians were giving that advice back when he was a resident almost 30 years ago. There is a basis for it, Patrick and other pediatricians said. There is a "classic" croup scenario where a child develops worsening symptoms at night and worried parents rush the child to the ER. "But by the time they get there, the symptoms are getting better," said Dr. Matthew Harris , an emergency physician at Cohen Children's Medical Center in New York. It seems that just a short time in the cool air can be helpful, Harris said. A new study, published online Aug. 1 in Pediatrics, put that belief to the test. The research was conducted by Dr. Johan Siebert and colleagues at Geneva Children's Hospital in Switzerland. They recruited families who were bringing their baby or young child to the ER because of croup symptoms. If the symptoms were mild to moderate, the families were randomly assigned to one of two groups: one where children were given the oral anti-inflammatory drug dexamethasone and then spent 30 minutes outside in the chilly air; and one where kids received dexamethasone and stayed inside the ER. None of the children had severe symptoms, such as persistent stridor, even at rest, or difficulty breathing. In those cases, it's standard to give inhaled epinephrine to open up the airways quickly, Patrick said. Overall, the study found, cold air was helpful for at least some kids. Of 59 children exposed to outdoor air, 49% had a substantial improvement in symptoms by the 30-minute mark. That compared with about 24% of 59 children who stayed indoors. However, the findings do not mean that ERs should start sending families out into the ambulance bay to manage a child's croup symptoms. For the study's purposes, the ER served as a controlled setting to observe the effects of cold air exposure, Harris and Patrick said. Instead, they said, pediatricians can see the findings as evidence for some benefit of the practice. "What's cool about this study is, it brings this into the realm of evidence, and not just anecdote," Patrick said. Dr. Joanne Nazif , of Children's Hospital at Montefiore in New York City, agreed that the study offers "some evidence" in support of cold air. But she also stressed that the researchers tested it in combination with dexamethasone -- not as a stand-alone. And cold air did not always help, Nazif noted. If parents have any worry about their child's breathing, Nazif said, they should seek care. But, she added, "you might want to crack the car window open on the way to the ER." Sources Michael Patrick, MD, emergency medicine physician, Nationwide Children's Hospital, assistant professor, clinical pediatrics, Ohio State University College of Medicine, Columbus, Ohio Matthew Isaac Harris, MD, emergency physician, Cohen Children's Medical Center, New York City Joanne M. Nazif, MD, attending physician, Children's Hospital at Montefiore, assistant professor, clinical pediatrics, Albert Einstein College of Medicine, New York City Pediatrics, September 2023 Posted August 2023