Category: biology

Developing Antivirals for COVID-19 and Beyond

Jeffrey Glenn, MD, PhD (Photo by Steve Fisch)

Almost every day, news outlets report on highly infectious COVID-19 variants threatening to sneak past the front-line antibody defenses developed by our bodies after vaccination or previous infection. That’s because the coronavirus strain responsible for COVID-19, SARS-CoV-2, is doing what most viruses do: evolving and naturally selecting toward becoming more resistant to vaccines and antiviral drugs.

This isn’t surprising to Stanford researcher Jeffrey Glenn, MD, PhD, professor of medicine and of microbiology and immunology, who has spent years developing novel antiviral therapies for hepatitis, influenza, and enteroviruses. Fortunately, he and his international collaborators quickly pivoted and applied their expertise to COVID-19 too.

“When all of Stanford was shut down, we were considered essential. In fact, we’d never been busier. We worked 24/7 in shifts, wearing masks and social distancing,” describes Glenn, the Joseph D. Grant Professor. “This is what we’ve trained our whole lives to do — help develop drugs that could counter this and future pandemics. It’s an honor and privilege to do this work.”

Glenn’s research focuses on two approaches for creating antivirals for various diseases. The first strategy targets factors in the host that the virus depends on. The second one targets the structure of the virus itself.

Targeting Factors in the Host to Treat Hepatitis

Although viruses mutate quickly, they rely on their hosts’ cells to reproduce. So, researchers are developing host-targeting drugs. These are novel antivirals that interfere with host factors essential for the life cycle of the virus or that boost the host’s innate immunity. For example, some antivirals target specific proteins in the host to prevent the virus from replicating its genome inside the host’s cells.

Host-targeting drugs have several advantages. They act on something in the host that isn’t under the genetic control of the virus, Glenn explains, so it’s much harder for the virus to mutate, escape the drug, and still be viable.

“Another advantage is in the biology,” he says. “If one virus has evolved to depend on a particular host factor, many other viruses may have too. So, you can create a broad-spectrum antiviral therapy: one drug for multiple bugs.”

Glenn’s team pursued this strategy for hepatitis delta, the most severe form of viral hepatitis.

First they discovered a specific process occurring inside a host’s liver cells that the virus depends on. Then they performed animal studies and human clinical trials to test the safety and effectiveness of treating hepatitis delta with lonafarnib, a drug originally designed to treat various cancers. They demonstrated that lonafarnib inhibits the identified host-cell process and prevents the virus from replicating.

“Our phase 2 trial showed no evidence of drug resistance — one of the first examples in humans to validate this advantage of a host-targeting drug,” Glenn says. “A company that I founded, Eiger Biopharmaceuticals, is completing by year’s end a phase 3 trial. Hopefully, lonafarnib will become the first oral drug approved by the U.S. Food and Drug Administration (FDA) for hepatitis delta based on that data.”

Glenn takes this success to heart, as evidenced by a photograph on his cell phone of three Turkish young men standing together in Ankara, where the study was conducted. “They are the first three patients in history to have their hepatitis delta virus become undetectable from lonafarnib,” he says. “There is nothing cooler for a physician-scientist than seeing something you’ve made actually make a difference in patients’ lives.”

Lonafarnib also demonstrates the potential advantage of using host-targeting drugs for nonviral applications. The FDA has approved the drug to treat Hutchinson-Gilford progeria syndrome, a rare genetic condition that causes children to prematurely age and die, and lonafarnib was shown to prolong their lives.

Pivoting to Treat COVID-19

Glenn and his collaborators have developed other host-targeting drugs — including peginterferon lambda, which was originally designed to treat hepatitis delta by boosting a host’s immune system.

When the pandemic hit, they realized peginterferon lambda may be the perfect drug to treat COVID-19, because it is a broad-spectrum antiviral that targets the body’s first line of defense against viruses. Importantly, it had already been safely given to more than 3,000 patients in 20 different clinical trials, mostly treating chronic hepatitis, for which it is administered weekly for up to a year, he says.

Since Eiger Biopharmaceuticals wasn’t funded for COVID-19 studies, it made peginterferon lambda available at no cost to outside researchers. Glenn’s colleagues responded with tremendous interest within minutes of getting his email offer. Stanford was the first site to finish a phase 2, randomized, placebo-controlled clinical trial, but other studies soon followed, including one in Toronto.

These phase 2 trials treated COVID-19 outpatients. Collectively, they showed a single dose of peginterferon lambda was well tolerated and significantly reduced the amount of SARS-CoV-2 virus in the nasal passages — particularly for patients who initially had a high level of detectable virus, Glenn explains.

Next, his colleagues in Brazil performed a large, randomized, placebo-controlled outcomes study to evaluate the effectiveness of peginterferon lambda. This TOGETHER Trial uses an adaptive trial design that analyzes data as it emerges rather than waiting until the end of the study, saving valuable time and money. The study ran from June 2021 to February 2022.

Even though the majority of more than 1,900 patients enrolled were vaccinated, a single dose of peginterferon lambda reduced the number of COVID-related hospitalizations by 51% and deaths by 61%, as reported in a Grand Rounds presentation. For unvaccinated patients treated early, there was an 89% reduction in COVID-19 hospitalizations or death. And it worked across all variants, including omicron.

“This has been a frustrating journey in the sense that I know this drug could have saved millions of lives if we had it ready at the beginning of the pandemic,” says Glenn. “But it can still save many lives. The phase 3 study is done, and hopefully that’ll be the basis of an emergency use authorization before the end of this year.”

Once approved, peginterferon lambda could be used on its own or in combination with Pfizer’s Paxlovid, an antiviral with a different underlying mechanism. Giving both antivirals together could help prevent drug resistance to Paxlovid from developing, says Glenn.

Glenn is also looking beyond COVID-19 treatment uses for the drug, believing it should work against influenza and other viruses too. In the future, he envisions a patient with a respiratory virus getting a shot of peginterferon lambda at a clinic, going home, and having the doctors sort out later which virus caused the infection.

Targeting RNA Structures in the Virus

In addition to developing host-targeting drugs, Glenn’s team is developing programmable antivirals that target a virus’s genome structure. After identifying essential RNA secondary structures for a virus, they design or “program” a drug to act against these structures. The aim is to use the virus’s own biology against itself, limiting its ability to mutate to escape the effect of the drug.

Glenn and his collaborators have developed such antivirals for influenza A and COVID-19 and have shown drug efficacy in animal models, but not in people yet.

In the influenza study, a single intranasal injection of the antiviral allowed mice to survive a lethal dose of influenza A virus — when the drug was given 14 days before or even three days after viral inoculation. Additionally, the antiviral provided immunity against a tenfold lethal dose of influenza A given two months later.

“We call this a single-dose preventive, therapeutic, and just-in-time universal vaccination that works against all influenza A virus strains, including drug-resistant ones,” says Glenn. “The primary goal is to prevent a severe influenza pandemic, but the same drug could be used for regular seasonal flu.”

Preparing for Future Pandemics

Glenn hopes the current pandemic is a wake-up call to better prepare against future pandemics.

“COVID-19 is tragic, but it isn’t what keeps me up at night,” admits Glenn. “We are extremely vulnerable to a highly pathogenic, drug-resistant influenza virus. That fear is really what motivates us.”

Fear of an influenza and other serious pandemics also inspired Glenn to start ViRx@Stanford, a Stanford Biosecurity and Pandemic Preparedness Initiative. Its goal is to proactively build up our collective antiviral tool kit to protect against future pandemics.

ViRx@Stanford’s subsection SyneRx was recently selected as one of nine Antiviral Drug Discovery Centers by the National Institutes of Health. Stanford’s center will involve more than 60 faculty and consultants working on seven research projects and three scientific cores. And ViRx@Stanford is now expanding, establishing hubs in Vietnam, Israel, Brazil, Singapore, and beyond.

“Innovative drug development is expensive. This is the kind of support that can actually help us do what we’ve never been able to do here before,” says Glenn. “The goal of all of this is to develop real-world drugs that can make a big difference for patients across the world. And I think we’re on track to do that.”

This is a reposting of my feature article in the recent Stanford Medicine annual report, courtesy of Stanford Medicine.

Lung Organoids: A Novel Way to Model COVID Infection

Calvin Kuo, MD, PhD, with Shannon Choi, MD, PhD, a student in the Kuo lab. Courtesy Steve Fisch

A year into the pandemic, we’ve all heard the stories. A patient is a little short of breath but appears to have a mild case of COVID-19. The next day, she deteriorates so rapidly that she’s rushed to intensive care, put on a ventilator, and hooked up to a dialysis machine to prevent kidney failure. Her overzealous immune system has gone rogue, attacking healthy cells instead of just fighting off the virus.

What triggers this devastating immune response, called a cytokine storm? Researchers are still struggling to identify the underlying processes that initiate a COVID infection and subsequent cytokine storm.

Biologists use advanced technologies and cell cultures in petri dishes to study severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the coronavirus strain responsible for COVID-19, identifying its key characteristics such as the famous crownlike spikes on their surfaces. But these short-lived cultures don’t act like real organs. And scientists are limited by their samples.

“When you analyze samples from patients, they’re often at the end stage of the disease, and many of the samples are from autopsy. You can’t understand the initiation process because the tissue is essentially destroyed,” says Calvin Kuo, MD, PhD, professor of hematology.

Understanding how the disease develops and testing potential treatments require better ways to model this coronavirus.

Miniature Organs in a Dish

Kuo’s laboratory develops organoids—three-dimensional miniature organs grown in a petri dish that mimic the shape, structure, and tissue organization of real organs.

Grown from human tissue samples using precisely defined ingredients, these organoids are little spheres of gel up to 1 millimeter in diameter. Healthy tissue samples are mechanically minced and enzyme digested to get to single cells, and then the organoids are grown from single stem cells. They last about six months, significantly longer than the few-weeks lifetime of traditional cell cultures.

Kuo initially developed organoids to study stem cell biology and model cancer. His team was the first to use organoids to convert normal tissues to cancer, as previously reported in Nature Medicine.

But he was passionate about using organoids to model infectious diseases. In 2015, he led a National Institute of Allergy and Infectious Diseases U19 research program, recently renewed for an additional five years, in collaboration with Stanford researchers Manuel Amieva, MD, professor of pediatrics and of microbiology and immunology; Harry Greenberg, MD, the Joseph D. Grant Professor in the Stanford University School of Medicine and professor of microbiology and immunology; Elizabeth Mellins, MD, professor of pediatrics; and Sarah Heilshorn, PhD, professor of materials science and engineering. Focusing mainly on the gastrointestinal tract, this multidisciplinary team provided proof of principle that organoids could model infectious diseases.

“With an organoid system, you can start at the infection and look at the very earliest events that occur after infection. And those can give insights as to what needs to be blocked therapeutically,” Kuo explains.

Distal Lung Organoids

After the initial success with gastrointestinal organoids, Ameen Salahudeen, MD, PhD, a hematology and oncology postdoctoral fellow working in Kuo’s lab, led efforts to expand this work by developing distal lung organoids. He partnered with lung stem cell expert Tushar Desai, MD, associate professor of pulmonary, allergy, and critical care medicine at Stanford.

The distal lung is composed of terminal bronchioles and alveolar air sacs, where inhaled air passes through the tiny ducts from the bronchioles into the elastic air sacs. It performs essential respiratory functions that can be compromised by inflammatory or infectious disorders, such as COVID-19 pneumonia.

“Growing distal lung cultures in a pure way that doesn’t require any supporting feeder cells and is in a chemically defined media had not been possible,” Kuo says. “We were able to do this very beautifully—to grow alveoli at the terminal bronchioles as long-term human cultures.”

The team developed two types of distal lung organoids. Both were made from human distal lung samples provided by Stanford cardiothoracic surgeon Joseph Schrager, MD.

They grew the first type, alveolar organoids, from single alveolar type 2 (AT2) stem cells. AT2 cells have several important functions that together help control the immune response to decrease lung injury and repair. The scientists then induced the AT2 cells to produce alveolar type 1 (AT1) cells, which are the thin-walled cells lining the alveolar air sacs; they are essential for the lung’s gas-exchange function.

“The second type are the basal organoids, which grow from single basal stem cells. They give rise to the mucus-secreting club cells and the ciliated cells with beating hair. And we can see the beating hair under the microscope—it’s quite dramatic,” describes Kuo. “That’s a very nice reproduction of the differentiation and function of the lung.” The team also grows a mixture of alveolar and basal organoids.

They selected these organoid types to determine which cell types in the bronchioles and alveoli were infectible—in hopes of identifying the different mechanisms for how viruses cause respiratory compromise.

Initially, they tested the distal lung organoids using the H1N1 influenza virus, collaborating with Stanford molecular virology expert Jeff Glenn, MD, PhD.

The team fluorescently labeled the virus and infected the lung organoids, demonstrating that the virus replicated in both basal and alveolar organoids. Next, they did more sophisticated PCR-based testing to show that the virus replicated its genome.

COVID-19 Model

“But then the COVID-19 pandemic hit, so we initiated a fabulous collaboration with infectious disease expert Catherine Blish, MD, PhD, in the Department of Medicine, to infect our lung organoids with SARS-CoV-2. This was driven by a talented MD-PhD student in my lab, Shannon Choi,” says Kuo. “She worked with Arjun Rustagi, an infectious disease fellow in Catherine Blish’s lab, who infected the organoids in a biosafety-level-3 lab.”

Another partnership was critical, though. An important coronavirus receptor, called angiotensin-converting enzyme 2, or ACE2, resides inside the lung organoids. But ACE2 needed to be on the outside of the organoid to get the infection going.

Luckily, Amieva previously devised a way to flip intestinal organoids inside out. Working together, Choi and Amieva turned the lung organoids inside out.

As reported in Nature in November 2020, the team demonstrated that the coronavirus infected their distal lung organoids, including the alveolar air sacs, where COVID-19 pneumonia originates. They also identified a new airway subpopulation as a COVID-19 virus target cell.

“Everyone knew basal cells were stem cells in the lung, but they thought they were all equivalent. Using our organoids, we discovered an unknown basal cell subpopulation containing the stem cell activity. And then we showed this subpopulation actually existed in human lungs in very interesting anatomic locations,” Kuo says.

COVID-19 Applications

According to Kuo, their distal lung organoids have three major applications for COVID-19.

They are using them to screen potential coronavirus therapeutic antibodies and to understand how these treatments work. Although initially focused on COVID-19, this screening will likely expand to other kinds of lung infections in the future.

Because the distal lung with the alveoli is the site of the COVID-19 pneumonia, they also plan to use the organoids to identify the underlying biological mechanisms behind coronavirus infection. Finally, they plan to extend their organoid system to incorporate immune cells and understand more complex processes. In particular, they plan to model the dreaded cytokine storm.

Overall, Kuo emphasizes that this organoid research represents a huge team effort involving many investigators with wide-ranging expertise from various departments at Stanford, as well as an “interesting evolution of events.” “Now we have a human experimental system to model SARS-CoV-2 infection of the distal lung with alveoli, which is the site of the lung disease that kills patients,” he summarizes. “We know patients die because of severe pneumonia and lung failure. We can now recapitulate this in the dish. So, we can study how it works, and also test drug treatments.” 

This is a reposting of my feature article in the recent Stanford Medicine Annual Report. Check it out to see videos of these lung organoids.

Innovative Antibody Treatment Proves Safe and Effective for Immune Disorders

Many blood and immune disorders could be cured by transplanting healthy blood stem cells from a matched donor. But first the patients need a pretreatment procedure to eliminate their own blood stem cells, making room in the bone marrow for the donor cells to take their place.

The problem is that the standard pretreatments—chemotherapy or radiation—are very toxic. Doctors don’t want to give them to vulnerable children, such as those with a rare genetic disorder called severe combined immunodeficiency (SCID).

Infants with SCID have compromised immune systems that struggle to fight off even common infections caused by viruses and fungi. These babies have many chronic and life-threatening problems, including frequent lung infections, chronic diarrhea, and recurrent sinus infections.

Judy Shizuru, MD, PhD, reviews data with Wendy Pang, PhD

“Without treatment, SCID infants usually die from infections within the first two years of life. Blood stem cell transplants are the only definitive cure for this disease,” says Judith Shizuru, MD, PhD, professor of blood and marrow transplantation and cellular therapy and of pediatrics. “But transplants usually involve chemotherapy, and we don’t want to give these agents to these children because they’re particularly susceptible to the damaging short-term and long-term effects—including growth defects, neurological problems, and increased risk of cancers. This is especially true for certain subtypes of SCID.”

Instead, SCID patients are often given a blood stem cell transplant without pretreating with chemotherapy to create space in their bone marrow. But then the donors’ self-renewing blood stem cells may not fully engraft, so the kids can’t robustly regenerate their immune systems. These children have to rely on regular intravenous immunoglobulin infusions to boost their immune response, and the effectiveness of donor immune cells can wane over time.

The great need for a less toxic pretreatment for blood stem cell transplants inspired Shizuru to initiate a Stanford study testing a novel antibody pretreatment in SCID patients—in collaboration with Rajni Agarwal-Hashmi, MD, associate professor of pediatrics, and other stem cell transplantation and regenerative medicine specialists at Stanford and UC-San Francisco.  

Targeting Blood Stem Cells

The novel pretreatment uses the JSP191 antibody to target a protein called CD117, found on the surface of blood stem cells. The antibody binds to this protein, which then blocks CD117 from binding to a stem cell factor critical for keeping blood stem cells alive. When the interaction between CD117 and the essential stem cell factor is interrupted, the patient’s blood stem cells are depleted—making space for the donor’s healthy cells to engraft.

“It’s not like chemotherapy or radiation,” says Shizuru. “It’s a targeted way to deplete the blood stem cells without damaging normal healthy cells.”

The Stanford team chose SCID patients for their first human JSP191 clinical trial in part because these children have a unique biology—they lack lymphocytes, so they are less likely to immunologically reject the blood stem cells from a donor. Since immune suppressive medications aren’t necessary, the researchers can more easily see if the antibody therapy clears space in the bone marrow and the transplant works.

Initially, the clinical trial studied older children and adults with SCID whose first blood stem cell transplant had failed, so that they could evaluate whether JSP191 therapy was safe and well tolerated. The participants ranged in age from 3 years old to mid-30s, but most were between 11 and 13 years old. According to Shizuru, many of these kids had chronic infections and also wanted to be liberated from having intravenous immunoglobulin infusions.  

Rajni Agarwal-Hashmi, MD

Promising Results

The results are very promising, as Shizuru reported in 2019 at the American Society of Hematology annual conference. The antibody safely created room in the patients’ bone marrow, allowing healthy donor stem cell engraftment without common side effects like transfusion reactions, treatment-related toxicities, or bone marrow suppression.

“The wonderful thing about the antibody JSP191 is it’s super-safe. This conditioning agent doesn’t affect the DNA or any other organ, as far as we can tell,” explains Shizuru. “We give it as a onetime, really low dose. And it’s not showing any side effects. It’s an amazing drug.” 

The study’s clinicians even remarked that the re-transplant kids looked bored in the hospital because the expected complications didn’t happen, says Shizuru. “The patients’ counts didn’t drop. They didn’t have increased infections. They didn’t need blood transfusions,” she says. “So, we decided to give the antibody as an inpatient treatment and then do everything else as outpatient after 48 hours.”

The results were promising from the start. The first participant pretreated with JSP191 was a 3-year-old girl with chronic diarrhea and infections. After about a year, she no longer had diarrhea and started going to school for the first time. In fact, her family was infected with COVID-19 and she did fine, as Shizuru learned during a public discussion.

Expanding the Clinical Trial

Based on the safety and success of the first phase, the JSP191 trial expanded to include infants newly diagnosed with SCID. Two infants have received the antibody pretreatment followed by a blood stem cell transplant.

The first infant did really well, demonstrating signs that his donor cells may fully restore his immune function. The second infant’s response was more complicated; the researchers determined that she had some immune function that may have rejected the maternal stem cells. She subsequently underwent another transplant without the antibody agent, using a mix of chemotherapies.  

After their initial success, Shizuru’s team expanded the use of JSP191 to include other vulnerable populations—older adults with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS). AML is a type of leukemia in which DNA mutations cause the rapid growth of abnormal cells that build up in the bone marrow. Although it starts in the bone marrow, AML often quickly moves to the blood and sometimes spreads to other parts of the body. MDS are a group of diverse bone marrow disorders in which the bone marrow does not produce enough healthy blood cells. Both AML and MDS primarily occur in people over 65 years old.

This adult study is based on the preclinical work of Wendy Pang, MD, PhD, who was a postdoctoral fellow in the Shizuru laboratory. She showed that the disease-causing MDS and AML stem cells express CD117, so they can be targeted by JSP191. Further, the team observed synergistic eradication of stem cells when these anti-CD117 antibodies were combined with low-dose radiation.

The ongoing clinical trial utilizing JSP191 combined with low-dose radiation is led by Lori Muffly, MD, assistant professor of blood and marrow transplantation and cellular therapies. The preliminary results are encouraging based on the first six participants, who were older adults (64–74 years old) with AML or MDS. The researchers observed no side effects associated with JSP191, and the patients’ blood stem cell transplants were successful.

“We transplanted our first SCID babies and then opened the trial up to older patients with AML and MDS. So, now we’re covering the full spectrum for this targeted therapy: from a 3-month-old infant with SCID to a 74-year-old with AML,” Shizuru says.

The JSP191 project has now moved to a biotechnology company, Jasper Therapeutics. Shizuru expects that in the future, the studies will expand to include sickle cell disease, a group of inherited red blood cell disorders, where the JSP191 antibody can help to engraft the donor cells.

“In terms of pretreatment, there’s been no innovation on transplant agents in decades. People have been innovating on transplant by simply reducing the dose of chemotherapies, but we haven’t seen a successful new agent,” explains Shizuru. “The development of JSP191 leverages our understanding of the biology of blood stem cells by targeting a critically important molecule. JSP191 antibody is now the platform agent.”

This is a reposting of my feature article in the recent Stanford Medicine Annual Report.

Scientists uncover surprising behavior of a fatty acid enzyme with potential biofuel applications

Derived from microscopic algae, the rare, light-driven enzyme converts fatty acids into starting ingredients for solvents and fuels.

A study using SLAC’s LCLS X-ray laser captured how light drives a series of complex structural changes in an enzyme called FAP, which catalyzes the transformation of fatty acids into starting ingredients for solvents and fuels. This drawing captures the starting state of the catalytic reaction. The dark green background represents the protein’s molecular structure. The enzyme’s light-sensing part, called the FAD cofactor, is shown at center right with its three rings absorbing a photon coming from bottom left. A fatty acid at upper left awaits transformation. The amino acid shown at middle left plays an important role in the catalytic cycle, and the red dot near the center is a water molecule. (Damien Sorigué/Université Aix-Marseille)

By Jennifer Huber

Although many organisms capture and respond to sunlight, it’s rare to find enzymes – proteins that promote chemical reactions in living things – that are driven by light. Scientists have identified only three so far. The newest one, discovered in 2017, is called fatty acid photodecarboxylase (FAP). Derived from microscopic algae, FAP uses blue light to convert fatty acids into hydrocarbons that are similar to those found in crude oil.

“A growing number of researchers envision using FAPs for green chemistry applications because they can efficiently produce important components of solvents and fuels, including gasoline and jet fuels.” says Martin Weik, the leader of a research group at the Institut de Biologie Structurale at the Université Grenoble Alpes.

Weik is one of the primary investigators in a new study that has captured the complex sequence of structural changes, or photocycle, that FAP undergoes in response to light, which drives this fatty acid transformation. Researchers had proposed a possible FAP photocycle, but the fundamental mechanism was not understood, partly because the process is so fast that it’s very difficult to measure. Specifically, scientists didn’t know how long it took FAP to split a fatty acid and release a hydrocarbon molecule.

Experiments at the Linac Coherent Light Source (LCLS) at the Department of Energy’s SLAC National Accelerator Laboratory helped answer many of these outstanding questions. The researchers describe their results in Science.

All the tools in a toolbox

To understand a light-sensitive enzyme like FAP, scientists use many different techniques to study processes that take place over a broad range of time scales. For instance, photon absorption happens in femtoseconds, or millionths of a billionth of a second, while biological responses on the molecular level often happen in thousandths of a second.

“Our international, interdisciplinary consortium, led by Frédéric Beisson at the Université Aix-Marseille, used a wealth of techniques, including spectroscopy, crystallography and computational approaches,” Weik says. “It’s the sum of these different results that enabled us to get a first glimpse of how this unique enzyme works as a function of time and in space.”

The consortium first studied the complex steps of the catalytic process at their home labs using optical spectroscopy methods, which investigate the electronic and geometric structure of atoms in the samples, including chemical bonding and charge. Spectroscopic experiments identified the intermediate states of the enzyme that accompanied each step, measured their lifetimes and provided information on their chemical nature. These results revealed the need for the ultrafast capabilities of the LCLS X-ray free-electron laser (XFEL), which can track the molecular motion with atomic precision.

A structural view of changes in the FAP molecule during the catalytic process was provided by serial femtosecond crystallography (SFX) at the LCLS. During these experiments, a jet of tiny FAP microcrystals was hit with optical laser pulses to kick off the catalytic reaction. This ensured that all the molecules react at a similar time, synchronizing their behavior and making it possible to track the process in detail. Extremely brief, ultrabright X-ray pulses then measured the resulting changes in the enzyme’s structure.

By integrating thousands of these measurements – acquired using various time delays between the optical and X-ray pulses – the researchers were able to follow structural changes in the enzyme. They also determined the structure of the enzyme’s resting state by probing without the optical laser.

Surprisingly, the researchers found that in the resting state, the light-sensing part of the enzyme has a bent shape. “This small molecule, called the FAD cofactor, is a derivative of vitamin B2 that acts like an antenna to capture photons,” Weik says. “It absorbs blue light and initiates the catalytic process. We thought the starting point of the FAD cofactor was planar, so this bent configuration was unexpected.”

The bent shape of the FAD cofactor was first discovered by X-ray crystallography at the European Synchrotron Radiation Facility, but the scientists had suspected this bend was an artifact of radiation damage, a common problem for crystallographic data collected at synchrotron light sources.

“Only SFX experiments could confirm this unusual configuration because of their unique ability to capture structural information before damaging the sample,” Weik says. “These experiments were complemented by computations. Without the high-level quantum calculations performed by Tatiana Domratcheva of Moscow State University, we wouldn’t have understood our experimental results.”

Next steps

Even with this improved understanding of FAP’s photocycle, unanswered questions remain. For example, researchers know carbon dioxide is formed during a certain step of the catalytic process at a specific time and location, but they don’t know if it is transformed into another molecule before leaving the enzyme.

“In future XFEL work, we want to identify the nature of the products and to take pictures of the process with a much smaller step size so as to resolve the process in much finer detail,” says Weik. “This is important for fundamental research, but it can also help scientists modify the enzyme to do a task for a specific application.”

Such precision experiments will be fully enabled by upcoming upgrades to the LCLS facility that will increase its pulse repetition rate from 120 pulses per second to 1 million pulses per second, transforming scientists’ ability to track complex processes like this.

Other researchers are already working towards industrial FAP applications, including a group that is designing an economic way to produce gases such as propane and butane.

The interdisciplinary consortium included researchers from the Institute of Structural Biology in Grenoble, Max Planck Institute for Medical Research in Heidelberg, Université Aix-Marseille, Ecole Polytechnique in Paris-Palaiseau, the Integrative Biology of the Cell Institute in Paris-Saclay, Moscow State University, the ESRF and SOLEIL synchrotrons in Grenoble and Paris-Saclay, and the team at SLAC National Accelerator Laboratory.

LCLS is a DOE Office of Science user facility. Major funding for this work came from the French National Research Agency (ANR).

Citation: D. Sorigué et al., Science, 9 April 2021 ((https://doi.org/10.1126/science.abd5687)

For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.

This reposting of my news release, courtesy of SLAC National Accelerator Center.

Computer models show promise for personalizing chemotherapy

Computers have revolutionized many fields, so it isn’t surprising that they may be transforming cancer research. Computers are now being used to model the molecular and cellular changes associated with individual tumors, allowing scientists to simulate the tumor’s response to different combinations of chemotherapy drugs.  

Modeling big data to improve personalized cancer treatment was the focus of a recent episode of the Sirius radio show “The Future of Everything.” On hand was Sylvia Plevritis, PhD, a professor of biomedical data science and of radiology at Stanford, who discussed her work with Stanford professor and radio show host Russ Altman, MD, PhD.  

Plevritis and her colleagues are using multi-omics data — including measures of gene expression, protein function, metabolic processes and more — to extensively profile individual tumors of individual patients.

They are analyzing this data to better understand how tumors become drug-resistant. She explained in the podcast that tumors are often heterogeneous — not every cell has the same gene mutations — but chemotherapy drugs typically target specific genetic mutations. Tumors are also driven by complex mechanisms beyond genetic mutations. So her lab is comprehensively characterizing the different cell types in a tumor and how these different cell types respond to individual drugs. By better understanding the complexity of what drives the tumor’s response, they hope to identify the underlying mechanisms of drug resistance.

The goal, Plevritis said, is to more accurately estimate the response of the entire tumor to a given set of drugs without having to run clinical trials on every drug combination. Using their modeling, they hope to identify the most promising drug combinations to make clinical trials more efficient, she said.

The research team tested their computational model by measuring the multi-omics profile of human cancer cells in a dish, before and after exposing the cells to specific drugs. Their model then identified the minimum combination of drugs with the maximum effect. This work used archived cell samples, so their modeling results didn’t impact the patients’ treatment. But they compared their model’s prediction to what drugs the patients actually received.

They determined that the best chemotherapy cocktail for most of the patients would have been just one or two of the drugs that they received. For about 10 percent of the patients, they predicted that a totally different drug would have been the most effective, Plevaritis said in the podcast.

Thus, their computational model may be able to divide patients into different groups, based on tumor characteristics, and match those groups with specific chemotherapy cocktails that would be most effective for them. Plevaritis’ team is currently setting up a study to validate their computational predictions for a group of patients with acute myeloid leukemia, in parallel with a combination drug therapy trial, she said.

As a member of the Cancer Intervention Surveillance Network Modeling consortium, Plevritis is also using computational models to evaluate the impact of cancer screening guidelines — such as the recommended frequency of mammograms for general breast cancer screening — on mortality rates. For example, policy organizations like the U.S. Preventive Service Task Force often ask the consortium to simulate thousands of different screening policies — and rank their potential impact — to use as part of their selection criteria, she said.

One outcome of this work is an online decision tool for women who are at high risk for developing breast cancer because they carry a mutation in the BRCA1 or BRCA2 gene. Plevritis said about 45,000 people worldwide have used the tool, and her team has received a lot of positive feedback.

“It’s been very satisfying to get these emails and this feedback from individuals who feel that this complex information was distilled in a way that they can make sense of it,” Plevritis said.

Image of acute promyelocytic leukemia cells by Ed Uthman

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Stanford researchers watch proteins assemble a protective shell around bacteria

Many bacteria and viruses are protected from the immune system by a thin, hard outer shell  — called an S-layer — composed of a single layer of identical protein building blocks.

Understanding how microbes form these crystalline S-layers and the role they play could be important to human health, including our ability to treat bacterial pathogens that cause serious salmonella, C. difficile and anthrax infections. For instance, researchers are working on ways to remove this shell to fight anthrax and other diseases.

Now, a Stanford study has observed for the first time proteins assembling themselves into an S-layer in a bacterium called Caulobacter crescentus, which is present in many fresh water lakes and streams.

Although this bacteria isn’t harmful to humans, it is a well-understood organism that is important to various cellular processes. Scientists know that the S-shell of Caulobacter crescentus is vital for the microbe’s survival and made up of protein building blocks called RsaA.  

A recent news release describes how the research team from Stanford and SLAC National Accelerator Laboratory were able to watch this assembly, even though it happens on such a tiny scale:

“To watch it happen, the researchers stripped microbes of their S-layers and supplied them with synthetic RsaA building blocks labeled with chemicals that fluoresce in bright colors when stimulated with a particular wavelength of light.

Then they tracked the glowing building blocks with single-molecule microscopy as they formed a shell that covered the microbe in a hexagonal, tile-like pattern (shown in image above) in less than two hours. A technique called stimulated emission depletion (STED) microscopy allowed them to see structural details of the layer as small as 60 to 70 nanometers, or billionths of a meter, across – about one-thousandth the width of a human hair.”

The scientists were surprised by what they saw: the protein molecules spontaneously assembled themselves without the help of enzymes.

“It’s like watching a pile of bricks self-assemble into a two-story house,” said Jonathan Herrmann, a graduate student in structural biology at Stanford involved in the study, in the news release.

The researchers believe the protein building blocks are guided to form in specific regions of the cell surface by small defects and gaps within the S-layer. These naturally-occurring defects are inevitable because the flat crystalline sheet is trying to cover the constantly changing, three-dimensional shape of the bacterium, they said.

Among other applications, they hope their findings will offer potential new targets for drug treatments.

“Now that we know how they assemble, we can modify their properties so they can do specific types of work, like forming new types of hybrid materials or attacking biomedical problems,” said Soichi Wakatsuki, PhD, a professor of structural biology and photon science at SLAC, in the release.

Illustration by Greg Stewart/SLAC National Accelerator Laboratory

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Predicting women at risk of preeclampsia before clinical symptoms

Many of my female friends became pregnant with their first child in their late 30s or early 40s, which increased their risk of common complications such as high blood pressure, gestational diabetes and preeclampsia.

Affecting over 8 million women worldwide, preeclampsia can lead to serious, even fatal, complications for both the mother and baby. The clinical symptoms of preeclampsia typically start at 20 weeks of pregnancy and include high blood pressure and signs of kidney or liver damage.

“Once these clinical symptoms appear, irreparable harm to the mother or the fetus may have already occurred,” said Stanford immunologist Brice Gaudilliere, MD, PhD.  “The only available diagnostic blood test for preeclampsia is a proteomic test that measures a ratio of two proteins. While this test is good at ruling out preeclampsia once clinical symptoms have occurred, it has a poor positive predictive value.”

Now, Stanford researchers are working to develop a diagnostic blood test that can accurately predict preeclampsia prior to the onset of clinical symptoms.

A new study conducted at Stanford was led by senior authors Gaudilliere, statistical innovator Nima Aghaeepour, PhD, and clinical trial specialist Martin Angst, MD, and co-first authors and postdoctoral fellows Xiaoyuan Han, PhD, and Sajjad Ghaemi, PhD. Their results were recently published in Frontiers in Immunology.

They analyzed blood samples from 11 women who developed preeclampsia and 12 women with normal blood pressure during pregnancy. These samples were obtained at two timepoints, allowing the scientists to measure how immune cells behaved over time during pregnancy.

“Unlike prior studies that typically assessed just a few select immune cell types in the blood at a single timepoint during pregnancy, our study focused on immune cell dynamics,” Gaudilliere explained. “We utilized a powerful method called mass cytometry, which measured the distribution and functional behavior of virtually all immune cell types present in the blood samples.”

The team identified a set of eight immune cell responses that accurately predicted which of the women would develop preeclampsia — typically 13 weeks before clinical diagnosis.

At the top of their list was a signaling protein called STAT5. They observed higher activity of STAT5 in CD4+ T-cells, which help regulate the immune system, at the beginning of pregnancy for all but one patient who developed preeclampsia.

“Pregnancy is an amazing immunological phenomenon where the mother’s immune system ‘tolerates’ the fetus, a foreign entity, for nine months,” said Angst. “Our findings are consistent with past studies that found preeclampsia to be associated with increased inflammation and decreased immune tolerance towards the fetus.”

Although their results are encouraging, more research is needed before translating them to the clinic.

The authors explained that mass cytometry is a great tool to find the “needle in the haystack.” It allowed them to survey the entire immune system and identify the key elements that could predict preeclampsia, but it is an exploratory platform not suitable for the clinic, they said.

“Now that we have identified the elements of a diagnostic immunoassay, we can use conventional instruments such as those used in the clinic to measure them in a patient’s blood sample.” Aghaeepour said.

First though, the team needs to validate their findings in a large, multi-center study. They are also using machine learning to develop a “multiomics” model that integrates these mass cytometry measurements with other biological analysis approaches. And they are investigating how to objectively define different subtypes of preeclampsia.

Their goal is to accurately diagnose preeclampsia before the onset of clinical symptoms.

 “Diagnosing preeclampsia early would help ensure that patients at highest risk have access to health care facilities, are evaluated more frequently by obstetricians specialized in high-risk pregnancies and receive treatment,” said Gaudilliere.

Women with preeclampsia can receive care through the obstetric clinic at Lucile Packard Children’s Hospital Stanford.

Photo by Pilirodriquez

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Seeing the Web of Microbes

New Web-based Tool Hosted at NERSC Helps Visualize Exometabolomic Data

The Web view, BG11+MvExtract
WoM The Web: Microcoleus vaginatus and six heterotrophic biocrust isolates in M. vaginatus extract. The metabolite composition of the control medium is represented by the solid tan circles. Hollow circles are metabolites that were only identified after microbial transformation (indicating production/release by at least one of the organisms and not initially present in the control medium). Connecting lines indicate an increase (red) or decrease (blue) in the metabolite level in the spent medium compared to the control.

Understanding nutrient flows within microbial communities is important to a wide range of fields, including medicine, bioremediation, carbon sequestration, and sustainable biofuel development. Now, researchers from Lawrence Berkeley National Laboratory (Berkeley Lab) have built an interactive, web-based data visualization tool to observe how organisms transform their environments through the increase and decrease of metabolites — enabling scientists to quickly see patterns in microbial food webs.

This visualization tool — the first of its kind — is a key part of a new data repository, the Web of Microbes (WoM) that contains liquid chromatography mass spectrometry datasets from the Northen Metabolomics Lab located at the U.S. Department of Energy’s Joint Genome Institute (JGI). The Web of Microbes project is an interdisciplinary collaboration between biologists and computational researchers at Berkeley Lab and the National Energy Research Scientific Computing Center (NERSC). JGI and NERSC are both DOE Office of Science user facilities.

“While most existing databases focus on metabolic pathways or identifications, the Web of Microbes is unique in displaying information on which metabolites are consumed or released by an organism to an environment such as soil,” said Suzanne Kosina, a senior research associate in Berkeley Lab’s Environmental Genomics & Systems Biology (EGSB) Division, a member of the DOE ENIGMA Scientific Focus Area, and lead author on a paper describing WoM published in BMC Microbiology. “We call them exometabolites since they are outside of the cell. Knowing which exometabolites a microbe ‘eats’ and produces can help us determine which microbes might benefit from growing together or which might compete with each other for nutrients.”

Four Different Viewpoints

WoM is a python application built on the Django web development framework. It is served from a self-contained python environment on the NERSC global filesystem by an Apache web server. Visualizations are created with JavaScript, cascading style sheets, and the D3 JavaScript visualization library.

Four different viewing methods are available by selecting the tabs labeled “The Web”, “One Environment”, “One Organism”, and “One Metabolite.” “The Web” view graphically displays data constrained by the selection of an environment, while the other three tabs display tabular data from three constrainable dimensions: environment, organism, and metabolite.

“You can think of the 3D datasets as a data cube,” said NERSC engineer Annette Greiner, second author on the BMC Microbiology paper. “The visualization tool allows you to slice the data cube in any direction. And each of these slices gives one of the 2D views: One Environment, One Organism, or One Metabolite.”

The most intuitive way to view the data is via The Web, which displays an overview of connections between organisms and the nutrients they act on within a selected environment. After choosing the environment from a pull-down menu, The Web provides a network diagram in which each organism is represented as a little box, each metabolite as a circle, and their interactions as connecting lines. The size of the circle scales with the number of organisms that interact with that metabolite, whereas the color and shade of the connecting line indicate the amount of increase (red) or decrease (blue) in the metabolite level due to the microbial activation.

“Having a lot more connecting lines indicates there’s more going on in terms of metabolism with those compounds in the environment. You can clearly see differences in behavior between the organisms,” Greiner said. “For instance, an organism with a dense number of red lines indicates that it produces many metabolites.”

Although The Web view gives users a useful qualitative assessment of metabolite interaction patterns, the other three tabular views provide more detailed information.

The One Environment view addresses to what extent the organisms in a single environment compete or coexist with each other. The heatmap table shows which metabolites (shown in rows) are removed or added to the environment by each of the organisms (shown in columns), where the color of each table cell indicates the amount of metabolic increase or decrease. And icons identify whether pairs of organisms compete (X) or are compatible (interlocking rings) for a given metabolite.

“For example, if you’re trying to design a bioreactor and you want to know which organisms would probably work well together in the same environment, then you can look for things with interlocking rings and try to avoid the Xs,” said Greiner.

Similarly, the One Organism heatmap table allows users to compare the actions of a single microbe on many metabolites across multiple environments. And users can use the One Metabolite table to compare the actions of multiple organisms on a selected metabolite in multiple environments.

“Ultimately, WoM provides a means for improving our understanding of microbial communities,” said Trent Northen, a scientist at JGI and in Berkeley Lab’s EGSB Division. “The data and visualization tools help us predict and test microbial interactions with each other and their environment.”

Participatory Design

The WoM tools were developed iteratively using a participatory design process, where research scientists from Northen’s lab worked directly with Greiner to identify needs and quickly try out solutions. This differed from the more traditional approach in which Greiner completes a coherent design for the user interface before showing it to the scientists.

Both Greiner and Kosina agreed that collaborating together was fun and productive. “Instead of going off to a corner alone trying to come up with something, it’s useful to have a user sitting on my shoulder giving me feedback in real time,” said Greiner. “Scientists often have a strong idea about what they need to see, so it pays to have frequent interactions and to work side by side.”

In addition to contributing Greiner’s expertise in data visualization and web application development, NERSC hosts WoM and stores the data. NERSC’s computing resources and well-established science gateway infrastructure should enable WoM to grow both in volume and features in a stable and reliable environment, the development team noted in the BMC Microbiology paper.

According to Greiner, the data itself doesn’t take up much storage space but that may change. Currently, only Northen’s group can upload data but the team hopes to support multiple user groups in the future. For now, the Berkeley Lab researchers are excited to share their data on the Web of Microbes where it can be used by scientists all over the world. And they plan to add more data to the repository as they perform new experiments.

Kosina said it also made sense to work with NERSC on the Web of Microbes project because the Northen metabolomics lab relies on many other tools and resources at NERSC. “We already store all of our mass spectrometry data at NERCS and run our analysis software on their computing systems,” Kosina said.

Eventually, the team plans to link the Web of Microbes exometabolomics data to mass spectrometry and genomics databases such as JGI’s Genome Portal. They are also working with the DOE Systems Biology Knowledgebase (KBase) to allow users to take advantage of KBase’s predictive modeling capabilities, Northen added, which will enable researchers to determine the functions of unknown genes and predict microbial interactions.

This is a reposting of my news feature originally published by Berkeley Lab’s Computing Sciences.

Blocking Zika: New antiviral may treat and prevent infection, a Stanford study suggests

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Image of the surface of the Zika virus by Purdue University/courtesy of Kuhn and Rossmann research groups

The Zika virus, which made headlines in 2016 following an outbreak in South America, is transmitted by mosquitos and can cause serious birth defects and neurological problems. Researchers are searching for antiviral treatments or effective vaccines to address this global health threat, but there are currently no approved treatments.

Now, Stanford researchers are taking a different approach — investigating cellular factors of humans that are essential for Zika to propagate. One of those factors is a type of protein called Hsp70, which helps proteins fold correctly and performs a wide range of housekeeping and quality-control functions in cells.

Based on a series of experiments in mosquito and human cells, the Stanford study found that certain Hsp70 proteins are required in multiple steps of the Zika virus’ lifecycle. By blocking Hsp70 with an Hsp70 inhibitor drug, the researchers were able to prevent virus replication, as recently reported in Cell Reports.

One advantage of targeting the human host protein to thwart Zika is that it is less likely to promote drug resistance, Judith Frydman, PhD, senior author of the paper and a professor of genetics and of biology at Stanford, told me.

“The emergence of drug-resistant variants is a major obstacle for the development of antiviral therapies,” she continued. “We hypothesize that because Hsp70 is required for several different steps in the Zika virus cycle, it would be difficult for Zika to acquire enough mutations to develop resistance to the Hsp70 inhibitors. This opens the way to both therapeutic and prophylactic use of these drugs for short courses of treatment without losing effectiveness due to resistance.”

In addition, the team found that the Hsp70 inhibitors showed negligible toxicity to the host cells at the concentrations needed to fully block virus production. They demonstrated this lack of toxicity in both human cells and mice.

“The virus has a much higher demand for Hsp70 than the host cellular processes,” Frydman said. “We can exploit the viral ‘addiction’ to Hsp70 for treatment to prevent the virus from producing the proteins it needs to replicate and infect cells. But most importantly, we show Hsp70 inhibitors can be administered to animals at therapeutically effective doses. To my knowledge, this is the first drug that actually works for Zika-infected animals, protecting them from lethal infection and disease symptoms.”

The researchers believe their new approach could serve to create broad-spectrum antivirals that work against other existing and emerging viruses. In fact, this class of drugs could also treat other insect-borne viruses including Dengue virus and Yellow Fever, Frydman said.

“Our findings provide new strategies to develop a novel class of antivirals that will not be rendered ineffective by the emergence of drug resistance,” Frydman said. “This unique property of targeting host factors used for viral protein folding therapeutically may close a fundamental gap in antiviral drug development.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Inherited Neanderthal genes protect us against viruses

Image by Claire Scully

When Neanderthals and modern humans interbred about 50,000 years ago, they exchanged snippets of DNA. Today, Europeans and Asians still carry 2 to 3 percent of Neanderthal DNA in their genomes.

During contact, they also exposed each other to viruses. This could have been deadly for the human species since Neanderthals encountered many novel infectious viruses while living for hundreds of thousands of years outside Africa. Luckily, the Neanderthals’ immune systems evolved genetic defenses against these viruses that were passed on to humans, according to a study reported in Cell.

“Neanderthal genes likely gave us some protection against viruses that our ancestors encountered when they left Africa,” said Dmitri Petrov, PhD, an evolutionary biologist at Stanford’s School of Humanities and Sciences, in a recent Stanford news release.

In the study, the researchers gathered a large dataset of several thousand proteins that interact with viruses in modern humans. They then identified 152 Neanderthal DNA snippets present in the genes that make these proteins. Most of the 152 genes create proteins that interact with a specific type of viruses, RNA viruses, which have RNA encased in a protein shell.

The team identified 11 RNA viruses with a high number of Neanderthal-inherited genes, including HIV, influenza A and hepatitis C. These viruses likely played a key role in shaping human genome evolution, they said.

Overall, their findings suggest that the genomes of humans and other species contain signatures of ancient epidemics.

“It’s similar to paleontology,” said David Enard, PhD, a former postdoctoral fellow in Petrov’s lab. “You can find hints of dinosaurs in different ways. Sometimes you’ll discover actual bones, but sometimes you find only footprints in fossilized mud. Our method is similarly indirect: Because we know which genes interact with which viruses, we can infer the types of viruses responsible for ancient disease outbreaks.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.