So far, it had been widely accepted that the light-sensitive nature of this material extends throughout the whole film, but scientists did not understand what was causing the shape-shifting movement. A group of scientists led by Dr Takahiro Seki of Nagoya University, Japan, set out to figure out exactly how this happens; they have published their findings in the journal Scientific Reports.

They cite a well-studied phenomenon called Marangoni flow as their inspiration: owing to this phenomenon, differences in “surface tension” (the property by which the particles in the outermost layer of liquids are always attracted inwards, creating a boundary for the liquid) cause many soft, plastic films to move in a peculiar pattern. The most famous example of this phenomenon is the formation of “wine legs” or droplets of liquid evaporating and streaking down the surfaces of wine glasses.

They decided to test whether ultraviolet light triggered changes in the surface tension of azobenzene plastic film, and whether those changes resulted in the film moving. They chose to first cover azobenzene film with a very thin top layer that was light-sensitive, then exposed this film to UV radiation. Next, they did the same with film that was covered in a top layer unresponsive to light. To their excitement, the scientists found surface structural changes in the film with a light-sensitive top layer, but not in the film with a “light-insensitive” top layer. “This is the first time anyone has demonstrated that only the light responsiveness of a very thin ‘nanometer’ level layer is needed for azobenzene-containing film to alter its surface morphology under UV,” said Dr Seki.

An important observation of this study is that the movement of the material isn’t dependent on “light polarization,” or the direction in which light waves travel. If it were, that would suggest that there is another force on the molecular level affecting the whole film. Instead, Dr Seki concludes that it is probably the changes in chemical structure at the surface induced by the UV radiation that changes surface tension, inducing movement to the top of the film.

Describing the wider ramifications of their results, Dr Seki states: “We are only at the cusp of developing this discovery onto an industrial scale, but you can imagine how needing only a very small amount of light-sensitive material can reduce costs. Many optical devices like photocopiers, printers, and monitors depend on the light-based surface change in azobenzene polymer film. Based on our findings, azobenzene film can also act as an “actuator” (that part in a device that moves other parts) in nanomachinery.”

These newly discovered properties have vast implications, from improving the economics of production and lowering material prices, to advancing the field of nanotechnology itself.

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An international team of scientists used genomic analysis to compare the main cellular receptor for the virus in humans — angiotensin converting enzyme-2, or ACE2 — in 410 different species of vertebrates, including birds, fish, amphibians, reptiles and mammals.

ACE2 is normally found on many different types of cells and tissues, including epithelial cells in the nose, mouth and lungs. In humans, 25 amino acids of the ACE2 protein are important for the virus to bind and gain entry into cells.

The researchers used these 25 amino acid sequences of the ACE2 protein, and modeling of its predicted protein structure together with the SARS-CoV-2 spike protein, to evaluate how many of these amino acids are found in the ACE2 protein of the different species.

“Animals with all 25 amino acid residues matching the human protein are predicted to be at the highest risk for contracting SARS-CoV-2 via ACE2,” said Joana Damas, first author for the paper and a postdoctoral research associate at UC Davis. “The risk is predicted to decrease the more the species’ ACE2 binding residues differ from humans.”

About 40 percent of the species potentially susceptible to SARS-CoV-2 are classified as “threatened” by the International Union for Conservation of Nature and may be especially vulnerable to human-to-animal transmission. The study was published Aug. 21 in the Proceedings of the National Academy of Sciences.

“The data provide an important starting point for identifying vulnerable and threatened animal populations at risk of SARS-CoV-2 infection,” said Harris Lewin, lead author for the study and a distinguished professor of evolution and ecology at UC Davis. “We hope it inspires practices that protect both animal and human health during the pandemic.”

Endangered species predicted to be at risk

Several critically endangered primate species, such as the Western lowland gorilla, Sumatran orangutan and Northern white-cheeked gibbon, are predicted to be at very high risk of infection by SARS-CoV-2 via their ACE2 receptor.

Other animals flagged as high risk include marine mammals such as gray whales and bottlenose dolphins, as well as Chinese hamsters.

Domestic animals such as cats, cattle and sheep were found to have a medium risk, and dogs, horses and pigs were found to have low risk for ACE2 binding. How this relates to infection and disease risk needs to be determined by future studies, but for those species that have known infectivity data, the correlation is high.

In documented cases of SARS-COV-2 infection in mink, cats, dogs, hamsters, lions and tigers, the virus may be using ACE2 receptors or they may use receptors other than ACE2 to gain access to host cells. Lower propensity for binding could translate to lower propensity for infection, or lower ability for the infection to spread in an animal or between animals once established.

Because of the potential for animals to contract the novel coronavirus from humans, and vice versa, institutions including the National Zoo and the San Diego Zoo, which both contributed genomic material to the study, have strengthened programs to protect both animals and humans.

“Zoonotic diseases and how to prevent human to animal transmission is not a new challenge to zoos and animal care professionals,” said co-author Klaus-Peter Koepfli, senior research scientist at Smithsonian-Mason School of Conservation and former conservation biologist with the Smithsonian Conservation Biology Institute’s Center for Species Survival and Center for Conservation Genomics. “This new information allows us to focus our efforts and plan accordingly to keep animals and humans safe.”

The authors urge caution against overinterpreting the predicted animal risks based on the computational results, noting the actual risks can only be confirmed with additional experimental data. The list of animals can be found here.

Research has shown that the immediate ancestor of SARS-CoV-2 likely originated in a species of bat. Bats were found to be at very low risk of contracting the novel coronavirus via their ACE2 receptor, which is consistent with actual experimental data.

Whether bats directly transmitted the novel coronavirus directly to humans, or whether it went through an intermediate host, is not yet known, but the study supports the idea that one or more intermediate hosts was involved. The data allow researchers to zero in on which species might have served as an intermediate host in the wild, assisting efforts to control a future outbreak of SARS-CoV-2 infection in human and animal populations.

Additional authors on the study include: Marco Corbo, UC Davis Genome Center; Graham M. Hughes and Emma C. Teeling, University College Dublin, Ireland; Kathleen C. Keough and Katherine S. Pollard, UC San Francisco; Corrie A. Painter, Nicole S. Persky, Diane P. Genereux, Ross Swofford, Kerstin Lindblad-Toh and Elinor K. Karlsson, Broad Institute of MIT and Harvard, Cambridge, Massachussetts; Michael Hiller, Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany; Andreas R. Pfenning, Carnegie Mellon University, Pittsburgh; Huabin Zhao, Wuhan University, Wuhan, China; Oliver A. Ryder, San Diego Zoo Institute for Conservation Research, Escondido, and UC San Diego; Martin T. Nweeia, Harvard School of Dental Medicine, Boston, and Smithsonian Institution, Washington D.C.

The research in this study was coordinated as part of the Genome 10K Organization, which includes the Bat1K, Zoonomia, the Vertebrate Genomes Project and the Earth BioGenome Project. Genomic information for the study was also provided the National Center for Biotechnology Information’s GenBank, the San Diego Zoo’s Frozen Zoo and the Smithsonian’s Global Genome Initiative. This work was supported by the Robert and Rosabel Osborne Endowment.

Coral reef environments are typically low in naturally occurring nutrients such as nitrogen and phosphorus compounds. But ocean currents passing by can bring in a concentration of nutrients from elsewhere. Similarly, nutrients from human-made fertilisers and stormwater runoff enter reefs from adjacent coastlines.

Lead author Dr Thomas DeCarlo from the King Abdullah University of Science and Technology (KAUST) says corals are sensitive to high levels of nutrients.

“As the climate warms, mass coral bleaching could occur as often as annually within this century,” Dr DeCarlo said. “In our study, we found that already heat-stressed corals exposed to excess nutrient levels were even more susceptible to bleaching.”

The study suggests ecosystem managers can reduce the impacts of coral bleaching by implementing strategies to reduce nutrient stress in areas subject to thermal stress.

Co-author Professor John Pandolfi from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at The University of Queensland says this and previous studies, including on the Great Barrier Reef, related coral bleaching to combinations of heat and nutrient stresses.

“Our results provide a roadmap for coral reef conservation efforts to be at their most effective,” Prof Pandolfi said. “We suggest oceanographic processes should be included when deciding when and where to allocate resources or protection.”

Using the skeletal cores of long-living corals, the authors studied the past few decades worth of bleaching events in the Red Sea. They found the reefs historically suffered severe bleaching only when high sea surface temperatures were coupled with high nutrient levels.

The Red Sea was chosen as a study site as it is one of the only marine environments where the effects of summertime nutrients and heat stress are independent of each other: only one area has a single major source of nutrients in the summer, when a water mass brings nutrients to the surface through a process called upwelling.

Previous field tests on the role of nutrients in coral bleaching were otherwise difficult: nutrients and temperature often co-vary in the ocean, making it difficult to disentangle their effects. Nutrient loads are also difficult to measure in the same way sea surface temperatures are, via satellite.

“The fact that nutrients are more difficult to measure than temperature may be restricting our recognition of their importance,” Dr DeCarlo said. “And we need greater longer-term monitoring efforts of nutrient levels on coral reefs.”

“Incorporating nutrient-supplying ocean currents into coral bleaching forecasts will enhance those predictions that are based on temperatures alone,” Prof Pandolfi said.

“Our research suggests that projections of coral reef futures should move beyond solely temperature-based stress to incorporate the influence of ocean current systems on coral reef nutrient enrichment, and thus susceptibility to bleaching,” Dr DeCarlo said.

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The study is available online in the journal Cell.

Unlike other COVID-19 vaccines in development, this one is delivered via the nose, often the initial site of infection. In the new study, the researchers found that the nasal delivery route created a strong immune response throughout the body, but it was particularly effective in the nose and respiratory tract, preventing the infection from taking hold in the body.

“We were happily surprised to see a strong immune response in the cells of the inner lining of the nose and upper airway — and a profound protection from infection with this virus,” said senior author Michael S. Diamond, MD, PhD, the Herbert S. Gasser Professor of Medicine and a professor of molecular microbiology, and of pathology and immunology. “These mice were well protected from disease. And in some of the mice, we saw evidence of sterilizing immunity, where there is no sign of infection whatsoever after the mouse is challenged with the virus.”

To develop the vaccine, the researchers inserted the virus’ spike protein, which coronavirus uses to invade cells, inside another virus — called an adenovirus — that causes the common cold. But the scientists tweaked the adenovirus, rendering it unable to cause illness. The harmless adenovirus carries the spike protein into the nose, enabling the body to mount an immune defense against the SARS-CoV-2 virus without becoming sick. In another innovation beyond nasal delivery, the new vaccine incorporates two mutations into the spike protein that stabilize it in a specific shape that is most conducive to forming antibodies against it.

“Adenoviruses are the basis for many investigational vaccines for COVID-19 and other infectious diseases, such as Ebola virus and tuberculosis, and they have good safety and efficacy records, but not much research has been done with nasal delivery of these vaccines,” said co-senior author David T. Curiel, MD, PhD, the Distinguished Professor of Radiation Oncology. “All of the other adenovirus vaccines in development for COVID-19 are delivered by injection into the arm or thigh muscle. The nose is a novel route, so our results are surprising and promising. It’s also important that a single dose produced such a robust immune response. Vaccines that require two doses for full protection are less effective because some people, for various reasons, never receive the second dose.”

Although there is an influenza vaccine called FluMist that is delivered through the nose, it uses a weakened form of the live influenza virus and can’t be administered to certain groups, including those whose immune systems are compromised by illnesses such as cancer, HIV and diabetes. In contrast, the new COVID-19 intranasal vaccine in this study does not use a live virus capable of replication, presumably making it safer.

The researchers compared this vaccine administered to the mice in two ways — in the nose and through intramuscular injection. While the injection induced an immune response that prevented pneumonia, it did not prevent infection in the nose and lungs. Such a vaccine might reduce the severity of COVID-19, but it would not totally block infection or prevent infected individuals from spreading the virus. In contrast, the nasal delivery route prevented infection in both the upper and lower respiratory tract — the nose and lungs — suggesting that vaccinated individuals would not spread the virus or develop infections elsewhere in the body.

The researchers said the study is promising but cautioned that the vaccine so far has only been studied in mice.

“We will soon begin a study to test this intranasal vaccine in nonhuman primates with a plan to move into human clinical trials as quickly as we can,” Diamond said. “We’re optimistic, but this needs to continue going through the proper evaluation pipelines. In these mouse models, the vaccine is highly protective. We’re looking forward to beginning the next round of studies and ultimately testing it in people to see if we can induce the type of protective immunity that we think not only will prevent infection but also curb pandemic transmission of this virus.”

This work was supported by the National Institutes of Health (NIH), grant and contract numbers 75N93019C00062, R01 AI127828, R01 AI130591, R01 AI149644, R35 HL145242, HHSN272201400018C, HHSN272201200026C, F32 AI138392 and T32 AI007163; the Defense Advanced Research Project Agency, grant number HR001117S0019; a Helen Hay Whitney Foundation postdoctoral fellowship; and the Pulmonary Morphology Core at Washington University School of Medicine.

Diamond is a consultant for Inbios, Vir Biotechnology, NGM Biopharmaceuticals, and on the scientific advisory board of Moderna. The Diamond laboratory has received unrelated funding support from Moderna, Vir Biotechnology, and Emergent BioSolutions. Diamond, Curiel, Ahmed Hassan and Igor Dmitriev have filed a disclosure with Washington University for possible development of ChAd-SARS-CoV-2. Michael Holtzman is a member of the DSMB for AstroZeneca and founder of NuPeak Therapeutics. The Baric laboratory has received unrelated funding support from Takeda, Pfizer and Eli Lily.