Dirt-powered fuel cell runs forever

New tech harvests energy from microbes in soil to power sensors, communications

Peer-Reviewed Publication

NORTHWESTERN UNIVERSITY

 

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THE FUEL CELL'S 3D PRINTED CAP PEEKS ABOVE THE GROUND. THE CAP KEEPS DEBRIS OUT OF THE DEVICE WHILE ENABLING AIR FLOW.

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CREDIT: BILL YEN/NORTHWESTERN UNIVERSITY

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• New fuel cell harnesses naturally occurring microbes to generate electricity
• Soil-powered sensors to successfully monitor soil moisture and detect touch
• New tech was robust enough to withstand drier soil conditions and flooding
• Fuel cell could replace batteries in sensors used for precision agriculture

EVANSTON, Ill. — A Northwestern University-led team of researchers has developed a new fuel cell that harvests energy from microbes living in dirt. 

About the size of a standard paperback book, the completely soil-powered technology could fuel underground sensors used in precision agriculture and green infrastructure. This potentially could offer a sustainable, renewable alternative to batteries, which hold toxic, flammable chemicals that leach into the ground, are fraught with conflict-filled supply chains and contribute to the ever-growing problem of electronic waste.

To test the new fuel cell, the researchers used it to power sensors measuring soil moisture and detecting touch, a capability that could be valuable for tracking passing animals. To enable wireless communications, the researchers also equipped the soil-powered sensor with a tiny antenna to transmit data to a neighboring base station by reflecting existing radio frequency signals.

Not only did the fuel cell work in both wet and dry conditions, but its power also outlasted similar technologies by 120%.

The research will be published today (Jan. 12) in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies. The study authors also are releasing all designs, tutorials and simulation tools to the public, so others may use and build upon the research.

“The number of devices in the Internet of Things (IoT) is constantly growing,” said Northwestern alumnus Bill Yen, who led the work. “If we imagine a future with trillions of these devices, we cannot build every one of them out of lithium, heavy metals and toxins that are dangerous to the environment. We need to find alternatives that can provide low amounts of energy to power a decentralized network of devices. In a search for solutions, we looked to soil microbial fuel cells, which use special microbes to break down soil and use that low amount of energy to power sensors. As long as there is organic carbon in the soil for the microbes to break down, the fuel cell can potentially last forever.”

“These microbes are ubiquitous; they already live in soil everywhere,” said Northwestern’s George Wells, a senior author on the study. “We can use very simple engineered systems to capture their electricity. We’re not going to power entire cities with this energy. But we can capture minute amounts of energy to fuel practical, low-power applications.”

Wells is an associate professor of civil and environmental engineering at Northwestern’s McCormick School of Engineering. Now a Ph.D. student at Stanford University, Yen started this project when he was an undergraduate researcher in Wells’ laboratory.

Solutions for a dirty job

In recent years, farmers worldwide increasingly have adopted precision agriculture as a strategy to improve crop yields. The tech-driven approach relies on measuring precise levels of moisture, nutrients and contaminants in soil to make decisions that enhance crop health. This requires a widespread, dispersed network of electronic devices to continuously collect environmental data.

“If you want to put a sensor out in the wild, in a farm or in a wetland, you are constrained to putting a battery in it or harvesting solar energy,” Yen said. “Solar panels don’t work well in dirty environments because they get covered with dirt, do not work when the sun isn’t out and take up a lot of space. Batteries also are challenging because they run out of power. Farmers are not going to go around a 100-acre farm to regularly swap out batteries or dust off solar panels.”

To overcome these challenges, Wells, Yen and their collaborators wondered if they could instead harvest energy from the existing environment. “We could harvest energy from the soil that farmers are monitoring anyway,” Yen said.

‘Stymied efforts’

Making their first appearance in 1911, soil-based microbial fuel cells (MFCs) operate like a battery — with an anode, cathode and electrolyte. But instead of using chemicals to generate electricity, MFCs harvest electricity from bacteria that naturally donate electrons to nearby conductors. When these electrons flow from the anode to the cathode, it creates an electric circuit.

But in order for microbial fuel cells to operate without disruption, they need to stay hydrated and oxygenated — which is tricky when buried underground within dry dirt.

“Although MFCs have existed as a concept for more than a century, their unreliable performance and low output power have stymied efforts to make practical use of them, especially in low-moisture conditions,” Yen said.

Winning geometry

With these challenges in mind, Yen and his team embarked on a two-year journey to develop a practical, reliable soil-based MFC. His expedition included creating — and comparing — four different versions. First, the researchers collected a combined nine months of data on the performance of each design. Then, they tested their final version in an outdoor garden.

The best-performing prototype worked well in dry conditions as well as within a water-logged environment. The secret behind its success: Its geometry. Instead of using a traditional design, in which the anode and cathode are parallel to one another, the winning fuel cell leveraged a perpendicular design.

Made of carbon felt (an inexpensive, abundant conductor to capture the microbes’ electrons), the anode is horizontal to the ground’s surface. Made of an inert, conductive metal, the cathode sits vertically atop the anode. 

Although the entire device is buried, the vertical design ensures that the top end is flush with the ground’s surface. A 3D-printed cap rests on top of the device to prevent debris from falling inside. And a hole on top and an empty air chamber running alongside the cathode enable consistent airflow.  

The lower end of the cathode remains nestled deep beneath the surface, ensuring that it stays hydrated from the moist, surrounding soil — even when the surface soil dries out in the sunlight. The researchers also coated part of the cathode with waterproofing material to allow it to breathe during a flood. And, after a potential flood, the vertical design enables the cathode to dry out gradually rather than all at once.

On average, the resulting fuel cell generated 68 times more power than needed to operate its sensors. It also was robust enough to withstand large changes in soil moisture — from somewhat dry (41% water by volume) to completely underwater.

Making computing accessible

The researchers say all components for their soil-based MFC can be purchased at a local hardware store. Next, they plan to develop a soil-based MFC made from fully biodegradable materials. Both designs bypass complicated supply chains and avoid using conflict minerals.

“With the COVID-19 pandemic, we all became familiar with how a crisis can disrupt the global supply chain for electronics,” said study co-author Josiah Hester, a former Northwestern faculty member who is now at the Georgia Institute of Technology. “We want to build devices that use local supply chains and low-cost materials so that computing is accessible for all communities.”

The study, “Soil-powered computing: The engineer’s guide to practical soil microbial fuel cell design,” was supported by the National Science Foundation (award number CNS-2038853), the Agricultural and Food Research Initiative (award number 2023-67021-40628) from the USDA National Institute of Food and Agriculture, the Alfred P. Sloan Foundation, VMware Research and 3M.

The fuel cell in the lab

The fuel cell, covered in dirt after being extracted from the ground for studies.

CREDIT

Bill Yen/Northwestern University

Bill Yen, the study's lead author, buried the fuel cell during testing in the lab at Northwestern University.

CREDIT

Northwestern University

CREDIT

Bill Yen/Northwestern University

JOURNAL

Proceedings of the ACM on Interactive Mobile Wearable and Ubiquitous Technologies

DOI

10.1145/3631410 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

Soil-Powered Computing: The Engineer's Guide to Practical Soil Microbial Fuel Cell Design

ARTICLE PUBLICATION DATE

16-Jan-2024

 

Science must support the breakthrough for the full renovation of homes and workplaces

Grant and Award Announcement

ESTONIAN RESEARCH COUNCIL

 

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TREE OF TRUTH

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CREDIT: STATISTICS ESTONIA

Estonian Ministry of Education and Research allocated 7 million euros to distribute over seven years for both the Centre of Excellence for Energy Efficiency, led by Professor and academician Jarek Kurnitski of the University of Technology, and the Centre of Excellence for Strategic Mineral and Carbon-based Resource Circular Economy, led by Professor Riina Aav.

According to Professor Kurnitski, the Centre of Excellence for Energy Efficiency aims to help break the trend of rising energy consumption and support a breakthrough in the full renovation of residential buildings in Estonia. The best expertise in engineering, data science, and social sciences in Estonia is being brought together for this purpose. ‘We will also work on the energy efficiency and resilience of new buildings where the energy transition has largely already taken place. The biggest challenge, however, is improving the energy efficiency of existing homes and workplaces. There is still a lot of work to be done to achieve a breakthrough,’ said Jarek Kurnitski.
The Centre of Excellence, led by Kurnitski, is already organising a scientific luncheon titled ‘Socially Cohesive and Broad-Based Renovation of Buildings’ on 26 January, at the Estonian Academy of Sciences, which will analyse the current situation of the Estonian building stock and present the best current solutions for energy-efficient renovation.

The Centre of Excellence for Strategic Mineral and Carbon-based Resource Circular Economy is jointly aiming to find solutions for managing complex supply chains and ensuring the quality of recycled materials. The objective is to overcome the technological challenges associated with mineral and carbon-based raw materials. ‘The results of the researchers working together can make a significant contribution to sustainable development and more efficient use of resources in a global context.’
In addition to researchers of natural sciences, engineering and economics from the Tallinn University of Technology, the Centre of Excellence is also bringing together researchers from the University of Tartu and the National Institute of Chemical Physics and Biophysics.

The 40 researchers in the Centre of Excellence will be working in four groups: the working groups on strategic mineral raw materials, carbon-based raw materials, industrial transfer of circular technologies, and the business applications and modelling analysis of the circular economy.

According to Tiit Lukk, Vice-Rector for Research at TalTech, the Centres of Excellence provide an amazing opportunity for cooperation not only within the University, but also between different research institutions. ‘A research group is like a string quartet, where music is played by a small number of musicians and is limited to four instruments. In contrast, a university is as varied as a symphony orchestra, which also gives the opportunity to play very different kinds of music, because in addition to string instruments, the wind and percussion instruments also add colour to the music. A centre of excellence, however, is like a chamber orchestra, which can perform a much wider repertoire than a quartet, but is more limited than a symphony orchestra due to the assortment of instruments. And yet, a chamber orchestra (the Centre of Excellence) is large and distinctive enough to give concerts on larger stages (do research that speaks more to society as a whole). Interestingly enough, a chamber orchestra is made up of around 40 to 50 musicians, which is also the number of researchers contributing to the Centre of Excellence,’ commented Lukk.

In total, ten Centres of Excellence were financed to achieve the objectives of the ‘Estonia 2035’ long-term development strategy. These Centres involve 10 evaluated research institutions and more than 80 research groups.

 

Help people monitor their own air quality to save lives, say pollution experts

Peer-Reviewed Publication

UNIVERSITY OF SURREY

Empowering the public to monitor pollution in their communities could lead to cleaner air, say researchers from the University of Surrey. 

 

During a five-month study, scientists from Surrey’s Global Centre for Clean Air Research (GCARE) worked with volunteers from Zero Carbon Guildford to create a new way of monitoring air quality in real-time. The data made the public more aware of pollution levels. The team hopes similar projects can empower communities to improve their air.   

 

The team installed ten low-cost sensors in the Zero Carbon Guildford building, a large public space in the town centre. The public had asked for live air pollution data, which researchers presented using a newly designed system. Emojis represented the levels of pollution, from “good” to “very high”.    

 

Professor Prashant Kumar, Director of the Global Centre for Clean Air Research at the University of Surrey, said:   

 

“Rather than study them from afar, we asked the local community what they wanted to know. We designed this research with them and helped them understand how to improve their air quality. We need more work like this. When scientists, public bodies and citizens come together, they can create a healthier environment for all.” 

 

Researchers found that large gatherings led to more dust in the air and more CO2, thanks to more people breathing it out. At peak times, high air pollution in the street outside led to a rise in smaller particles inside the building, too.    

 

Members of the public then got tips on how to improve air quality through an interactive quiz.   

 

Professor Kumar said:  

“We found that large gatherings can worsen the air quality indoors, and pollution outside can find its way in. But knowledge is power. Our study helped people find better ways to ventilate their homes and workplaces – improving air quality and improving their health.”   

  

Ben McCallan, former chair of Zero Carbon Guildford and co-author of the study, said:   

“Polluted air causes around 7 million premature deaths a year. This collaborative work is a leading example of how to help local communities understand the situation where they live and work. This empowers them to solve their own air quality challenges. 

“Our approach does not cost much, but could transform public health for millions.”   

 

The study demonstrates Surrey’s contribution to UN Sustainability Goal 11 – Sustainable Cities and Communities. 

 

The research is published in the journal Sustainable Horizons. 

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JOURNAL

Sustainable Horizons

DOI

10.1016/j.horiz.2023.100086 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Improving air pollution awareness of the general public through citizen science approach

ARTICLE PUBLICATION DATE

12-Jan-2024

COI STATEMENT

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment This work has been carried out as a part of the RealAir (Real-Time Display of Air Pollution) project supported by the University of Surrey's Higher Education Innovation Funding (HEIF). We thank Idris Hayward and Narges Pourshahrokhi for their inputs during the development of the Live Air Pollution Data tool. We also thank the University of Surrey's Global Centre for Clean Air Research (GCARE) team, including visiting researcher Yasemin Guler, for their help during the various stages of the work. We also thank all ZCG visitors, volunteers and participants who enthusiastically participated and supported this project. PK acknowledges the support received from the EPSRC-Funded CO-TRACE/SAMHE (EP/W001411/1), NERC-funded GreenCities (NE/X002799/1), UKRI (EPSRC, NERC and AHRC) funded RECLAIM Network Plus (EP/W034034/1) and the RECLAIM Network Plus funded CoGreen project.

 

Study examines how ad strategies of the Great Depression can inform today's crisis communications

Approaches by Dust Bowl newspapers to advertise during dual crisis can hold lessons for current mass media during emergencies

Peer-Reviewed Publication

UNIVERSITY OF KANSAS

LAWRENCE — The COVID-19 pandemic was not the first time a crisis swept through the nation and beyond, forcing businesses and media to find ways to reach people in uncertain times. A new study from the University of Kansas has analyzed newspaper advertising strategies from the Great Depression to see what one historic crisis can teach communicators about reaching people today.

Researchers analyzed newspaper ads from Dust Bowl states during 1934 to see how businesses and companies tried to reach consumers. Results showed essential services such as utilities, banks and transportation companies used informational and rational strategies, while nonessential services such as tobacco and cosmetics companies tended to use transformational and sensory approaches. While the times and technologies of the two eras were different, lessons learned can both help communicators avoid mistakes of the past and consider new ways to communicate with people during times of crisis.

“It was interesting to me to think about how, during COVID, so many newspapers turned to the 1918 influenza pandemic to see what they could learn. But nobody seemed to really look at the advertising side,” said Teri Finneman, associate professor of journalism & mass communications at KU. “We saw a lot of lessons to be learned from the Great Depression when American society and media were dealing with the economic crisis and the Dust Bowl, two major catastrophes, at the same time.”

Chloe Martens, a recent graduate of KU, was taking Finneman’s journalism history class and conducted a pilot analysis of advertising strategies during the Depression for her final project. The project became “Is It Smart to Be Thrifty?: How Advertisers Navigated Message Strategies During the Great Depression,” recently published in the journal Journalism History.

The study, written by Finneman, Vaibhav Diwanji, assistant professor; Melissa Greene-Blye, assistant professor; and Martens, all of KU, analyzed newspaper ads from the year 1934 published in Nebraska, Colorado, Kansas, Oklahoma, New Mexico and Texas. The states were chosen as they were the epicenter of the Dust Bowl crisis, while 1934 was selected as the timeframe because it was one of the most financially and economically devastating years of the Depression.

Analysis showed brands continued to advertise and used psychological approaches to appeal to people at that particular time in history. Banks, which took much of the blame for the financial struggles of the time, tended to use reassurance as a theme, urging people to trust them as they were in the struggle with the people. Some ads saw claims of banks investing one dollar of their own for every four deposited by consumers. One featured a drawing of President Franklin Delano Roosevelt shaking hands with Baby New Year and promising that next year would be better for everyone.

Advertisements for nonessential products like tobacco or cosmetics tended to appeal to people’s senses, rights to feel good despite hard times and transforming from their difficult circumstances. Cosmetics ads assured women their products could help them move to higher social classes, while cigarette ads claimed their products could make people feel better and even deliver health benefits.

Newspapers were not immune from the struggles of the era, and Greene-Blye, a media historian, noted how publications engaged in boosterism, or positioning themselves as essential to people’s lives, especially during difficult times. That echoed an earlier time in American history. As communities were established in the 19th century, a newspaper was viewed as key to having a successful city.

“They positioned themselves as the best way to find the most important information,” Greene-Blye said. “‘Of all things you might sacrifice, not your newspaper.’ Not only because they would find the best information there, but because they’d find the best deals.”

And times of financial hardship, finding deals is especially important to consumers. Advertisers repeatedly touted not only their own good prices but the acceptability of thrift as a practice, hence the title of the study.

Diwanji, who has studied advertising and messaging during the pandemic, said there were parallels between advertising during the Depression and the more recent pandemic.

“A lot of ads during the pandemic were focusing on ‘staycations.’ Saying things like, ‘Even if you’re stuck at home, you still deserve to feel good.’ That is similar to how we saw tobacco ads promoting health,” Diwanji said. “They were trying to distract from the tragic position and focus less on the problems ‘out there’ and more on economic or social betterment.”

Understanding what types of approaches work in times of crisis can benefit advertisers and consumers, the authors wrote.

“The two sides get disconnected, especially in times of crisis,” Diwanji said of advertisers and consumers. “We saw during the pandemic how many institutions simply went silent or went with a bland ‘we’re all in this together’ message and got criticized for being tone deaf. Understanding past approaches can help avoid that type of criticism and get people the information they need.”

Image credit: Study authors from newspaper archives

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JOURNAL

Journalism History

DOI

10.1080/00947679.2023.2270890 

METHOD OF RESEARCH

Content analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

“Is It Smart to Be Thrifty?”: How Advertisers Navigated Message Strategies During the Great Depression

1933

 

Do violent video games numb us towards real violence?

Results of a neuroscientific study suggest that violence in video games has no negative influence on the empathy of adults

Peer-Reviewed Publication

UNIVERSITY OF VIENNA

Neuroscientists from the University of Vienna and the Karolinska Institute in Stockholm have investigated whether playing violent video games leads to a reduction in human empathy. To do this, they had adult test subjects play a violent video game repeatedly over the course of an experiment lasting several weeks. Before and after, their empathic responses to the pain of another person were measured. It was found that the violent video game had no discernible effect on empathy and underlying brain activity. These results have now been published in the renowned journal eLife.

Video games have become an integral part of the everyday life of many children and adults. Many of the most popular video games contain explicit depictions of extreme violence. Therefore, concerns have been raised that these games may blunt the empathy of their players and could therefore lower the inhibition threshold for real violence. An international research team led by Viennese neuroscientists Claus Lamm and Lukas Lengersdorff has now investigated whether this is actually the case.

The Austrian and Swedish researchers invited a total of 89 adult male subjects to take part in the study. A key selection criterion was that the subjects had had little or no previous contact with violent video games. This ensured that the results were not influenced by different experiences with these games. In a first experimental study, the baseline level of empathy of the test subjects was assessed. Brain scans were used to record how the test subjects reacted when a second person was administered painful electric shocks. Then, the video game phase of the experiment began, during which the test subjects came to the research laboratory seven times to play a video game for one hour each time. The participants in the experimental group played a highly violent version of the game Grand Theft Auto V and were given the task of killing as many other game characters as possible. In the control group, all violence had been removed from the game and the participants were given the task of taking photos of other game characters. Finally, after the video game phase was over, the test subjects were examined a second time to determine whether their empathic responses had changed.

The analysis of the data showed that the video game violence had no discernible effect on the empathic abilities of the test subjects. The reactions of the participants in the experimental group who were confronted with extreme depictions of violence did not differ statistically from those of the participants who only had to take photos. In addition, there were no significant differences in the activity of brain regions that had been identified in other studies as being associated with empathy – such as the anterior insular and anterior midcingulate cortex. 

Does that mean that concerns about violence in video games are unfounded? The authors advise against jumping to conclusions. "Precisely because this is such a sensitive topic, we have to be very careful when interpreting these results," explains lead author Lukas Lengersdorff, who carried out the study as part of his doctoral studies. "The conclusion should not be that violent video games are now definitively proven to be harmless. Our study lacks the data to make such statements." According to the neuroscientist and statistician, the value of the study lies rather in the fact that it allows a sober look at previous results. "A few hours of video game violence have no significant influence on the empathy of mentally healthy adult test subjects. We can clearly draw this conclusion. Our results thus contradict those of previous studies, in which negative effects were reported after just a few minutes of play". In these previous studies, participants had played the violent video game immediately before data collection. "Such experimental designs are not able to distinguish the short-term and long-term effects of video games", explains Lengersdorff.

According to research group leader and co-author Claus Lamm, the study also sets a new standard for future research in this area: "Strong experimental controls and longitudinal research designs that allow causal conclusions to be drawn are needed to make clear statements about the effects of violent video games. We wanted to take a step in this direction with our study". Now it is the task of further research to check whether there are no negative consequences even after significantly longer exposure to video game violence – and whether this is also the case for vulnerable subpopulations. "The most important question is of course: are children and young people also immune to violence in video games? The young brain is highly plastic, so repeated exposure to depictions of violence could have a much greater effect. But of course these questions are difficult to investigate experimentally without running up against the limits of scientific ethics," says Lamm.

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JOURNAL

eLife

DOI

10.7554/eLife.84951 

ARTICLE TITLE

Neuroimaging and behavioral evidence that violent video games exert no negative effect on human empathy for pain and emotional reactivity to violence.

ARTICLE PUBLICATION DATE

16-Jan-2024

SEE

LA REVUE GAUCHE - Left Comment: Search results for EMOTIONAL PLAGUE 

 

Light-matter interaction: broken symmetry drives polaritons

Peer-Reviewed Publication

FRITZ HABER INSTITUTE OF THE MAX PLANCK SOCIETY

 

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STRUCTURAL AND OPTICAL SYMMETRY BREAKING IN POLAR CRYSTALS

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CREDIT: FHI

An international team of scientists provide an overview of the latest research on light-matter interactions. A team of scientists from the Fritz Haber Institute, the City University of New York and the Universidad de Oviedo has published a comprehensive review article in the scientific journal Nature Reviews Materials. In this article, they provide an overview of the latest research on polaritons, tiny particles that arise when light and material interact in a special way.

In recent years, researchers worldwide have discovered that there are different types of polaritons. Some of them can trap light in a very small space, about the size of a nanometer. That's about 80,000 times thinner than a human hair!

The scientists report in their article that these special polaritons can arise in certain crystals. When the light in these crystals generates special vibrations - the researchers call this "phonons" - these special polaritons are created. Interestingly, they also found that the less symmetric the crystal is, the better the whole thing works. This leads to new and exciting possibilities for controlling light in the smallest space.

In their article, the scientists provide an overview of the latest research findings and discuss how these new insights could be used in the future. They believe that this work could help develop new materials that can use light in innovative ways.

This fundamental research could therefore have a major impact on many areas, from the development of new technologies to the improvement of existing devices. It's an exciting step forward in the world of nanotechnology!

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JOURNAL

Nature Reviews Materials

DOI

10.1038/s41578-023-00620-7 

ARTICLE TITLE

Extreme light confinement and control in low-symmetry phonon-polaritonic crystals

 

We need a staph vaccine: here’s why we don’t have one

Research from UC San Diego explains the clinical failure of dozens of candidate vaccines for one of the most common human infections; it also suggests a way to fix the problem

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - SAN DIEGO

 

IMAGE: 

THIS ILLUSTRATION SHOWS SA (GOLDEN SPHERES) AND VARIOUS ANTIGENS AND ANTIBODIES. DOMINANT ANTIGENS (PURPLE) CAUSE SA TO PRODUCE NON-PROTECTIVE ANTIBODIES (RED WITH PURPLE TIPS). THESE NONPROTECTIVE ANTIBODIES OUTCOMPETE ANTIBODIES DERIVED FROM VACCINATION (GREEN WITH PURPLE TIPS). VACCINES TARGETING SUBDOMINANT ANTIGENS (BLUE) COULD HELP YIELD MORE PROTECTIVE ANTIBODIES (GREEN WITH BLUE TIPS), MAKING THE VACCINE MORE EFFECTIVE.

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CREDIT: JR CALDERA/ UC SAN DIEGO HEALTH SCIENCES

Staphylococcus aureus (SA) is an extremely common bacterial infection; about 30% of people have colonies of SA living in their nose. SA is often harmless, but it is also a leading cause of hospital-acquired and community-associated infections. A vaccine for SA would be a game-changer for public health, but for decades, all vaccine candidates for SA have failed in clinical trials despite successful preclinical studies in mice. Researchers at University of California San Diego School of Medicine have finally explained why.

In a new study, published January 16, 2024 in Cell Reports Medicine, they tested a new hypothesis that SA bacteria can trick the body into releasing non-protective antibodies when they first colonize or infect humans. When the individual is later vaccinated, these non-protective antibodies are preferentially recalled, making the vaccine ineffective.

SA has a unique relationship with humans. While it causes many dangerous health complications, including wound and bloodstream infections, the bacterium is also a normal part of the healthy human microbiome, where it lives peacefully in the nose and on the skin.

“SA has been with humans a long time, so it’s learned how to be part-time symbiont, part-time deadly pathogen,” said senior author George Liu MD, PhD, professor in the Department of Pediatrics at UC San Diego School of Medicine. “If we’re going to develop effective vaccines against SA, we need to understand and overcome the strategies it uses to maintain this lifestyle.”

The immune system releases protective antibodies in response to molecules it suspects are foreign, called antigens. These antibodies are then saved in the immune system’s memory, so the next time the immune system encounters that same antigen, it will generally recall its earlier immune response rather than mount a brand-new attack.

“This is an effective system for conferring long-term protection against pathogens, but it only works when the initial immune response to that pathogen was actually protective,” said co-lead author JR Caldera, PhD, who completed his doctoral research in the Liu Lab. “What sets SA apart is that the bacteria themselves have ways of evading the immune system from the moment they encounter us, and these evasive strategies are only reinforced by vaccination.”

While SA vaccines have unilaterally failed in clinical trials, they generally do well in preclinical studies of mice. In order to figure out why this is, the researchers collected blood serum from healthy volunteers, quantifying and purifying the anti-SA antibodies present in the samples. They then transferred these antibodies to mice to explore how protective they were against SA on their own, as well as how they influenced the efficacy of several clinically-tested SA vaccine candidates.

The researchers found that the vaccines were ineffective in mice that had been given human anti-SA antibodies, as well as mice that had been previously exposed to SA. However, in mice that had never been exposed to either SA or human antibodies, the vaccines worked. Unlike previous mouse studies of SA vaccines, the researchers’ results were consistent with those of failed clinical trials, suggesting that their experimental model could help predict the clinical success of SA vaccines while they are still being tested in preclinical mouse studies.

Further, they found that specific antibodies were to blame for the effect they observed. The antibodies that attack the cell walls of SA bacteria, which are the basis for most current SA vaccines, didn’t protect the mice against SA. By contrast, antibodies that target the toxins produced by SA were able to successfully neutralize them.

“One pathogen can have many different antigens that the immune system responds to, but there is a hierarchy as far as which antigen is dominant,” said co-lead author Chih Ming Tsai, PhD, a project scientist in the Liu Lab.  “Most vaccines are based on the dominant antigen to trigger the strongest possible immune response. But our findings suggest that for SA, the rules are different, and it is more beneficial to target so-called subdominant antigens, which triggered a weak immune response in the first place.”

In addition to exploring the possibility of targeting new antigens with future SA vaccines, the researchers are also interested in exploring the deeper question at play here: why is the natural human immune response to this bacterium so ineffective to begin with?

“Somehow, SA is able to trick our immune system, and figuring out how will help us improve existing SA vaccines and develop new ones,” said Liu. “More broadly, these findings suggest a whole new way of reevaluating failed vaccines, which could have implications well beyond this one bacterium.”

Co-authors of the study include: Desmond Trieu, Cesia Gonzalez, Irshad A. Hajam, Xin Du and Brian Lin at UC San Diego.

This study was funded, in part, by the National Institute of Health (grants R01AI127406, R01AI144694 and R01AI181321).

This graphical abstract shows the experimental approach used by the researchers to study immune responses to SA vaccination. Vaccines targeting subdominant antigens, such as toxins produced by the bacteria, conferred more protection than vaccines targeting dominant antigens.

CREDIT

UC San Diego Health Sciences

JOURNAL

Cell Reports Medicine

DOI

10.1016/j.xcrm.2023.101360 

COI STATEMENT

George Y. Liu, Chih-Ming Tsai and Irshad A. Hajam have received a research grant from Pfizer to study S. aureus vaccines.

Disclaimer: AAAS and Eure