Dr. Francis Collins
Posted on by Dr. Francis Collins
One of the best ways to learn how something works is to understand how it’s built. How it came to be. That’s true not only if you play a guitar or repair motorcycle engines, but also if you study the biological systems that make life possible. Evolutionary studies, comparing the development of these systems across animals and organisms, are now leading to many unexpected biological discoveries and promising possibilities for preventing and treating human disease.
While there are many evolutionary questions to ask, Brenda Bass, a distinguished biochemist at University of Utah, Salt Lake City, has set her sights on a particularly profound one: How has innate immunity evolved through the millennia in all living things, including humans? Innate immunity is the immune system’s frontline defense, the first responders that take control of an emerging infectious situation and, if needed, signal for backup.
Exploring the millennia for clues about innate immunity takes a special team, and Bass has assembled a talented one. It includes her Utah colleague Nels Elde, a geneticist; immunologist Dan Stetson, University of Washington, Seattle; and biochemist Jane Jackman, Ohio State University, Columbus.
With a 2020 NIH Director’s Transformative Research Award, this hard-working team will embark on studies looking back at 450 million years of evolution: the point in time when animals diverged to develop very distinct methods of innate immune defense . The team members hope to uncover new possibilities encoded in the innate immune system, especially those that might be latent but still workable. The researchers will then explore whether their finds can be repurposed not only to boost our body’s natural response to external threats but also to internal threats like cancer.
Bass brings a unique perspective to the project. As a postdoc in the 1980s, she stumbled upon a whole new class of enzymes, called ADARs, that edit RNA . Their function was mysterious at the time. It turns out that ADARs specifically edit a molecule called double-stranded RNA (dsRNA). When viruses infect cells in animals, including humans, they make dsRNA, which the innate immune system detects as a sign that a cell has been invaded.
It also turns out that animal cells make their own dsRNA. Over the years, Bass and her lab have identified thousands of dsRNAs made in animal cells—in fact, a significant number of human genes produce dsRNA . Also interesting, ADARs are crucial to marking our own dsRNA as “self” to avoid triggering an immune response when we don’t need it .
Bass and others have found that evolution has produced dramatic differences in the biochemical pathways powering the innate immune system. In vertebrate animals, dsRNA leads to release of the immune chemical interferon, a signaling pathway that invertebrate species don’t have. Instead, in response to detecting dsRNA from an invader, and repelling it, worms and other invertebrates trigger a gene-silencing pathway known as RNA interference, or RNAi.
With the new funding, Bass and team plan to mix and match immune strategies from simple and advanced species, across evolutionary time, to craft an entirely new set of immune tools to fight disease. The team will also build new types of targeted immunotherapies based on the principles of innate immunity. Current immunotherapies, which harness a person’s own immune system to fight disease, target infections, autoimmune disorders, and cancer. But they work through our second-line adaptive immune response, which is a biological system unique to vertebrates.
Bass and her team will first hunt for more molecules like ADARs: innate immune checkpoints, as they refer to them. The name comes from a functional resemblance to the better-known adaptive immune checkpoints PD-1 and CTLA-4, which sparked a revolution in cancer immunotherapy. The team will run several screens that sort molecules successful at activating innate immune responses—both in invertebrates and in mammals—hoping to identify a range of durable new immune switches that evolution skipped over but that might be repurposed today.
Another intriguing direction for this research stems from the observation that decreasing normal levels of ADARs in tumors kickstarts innate immune responses that kill cancer cells . Along these lines, the scientists plan to test newly identified immune switches to look for novel ways to fight cancer where existing approaches have not worked.
Evolution is the founding principle for all of biology—organisms learn from what works to improve their ability to survive. In this case, research to re-examine such lessons and apply them for new uses may help transform bygone evolution into a therapeutic revolution!
 Evolution of adaptive immunity from transposable elements combined with innate immune systems. Koonin EV, Krupovic M. Nat Rev Genet. 2015 Mar;16(3):184-192.
 A developmentally regulated activity that unwinds RNA duplexes. Bass BL, Weintraub H. Cell. 1987 Feb 27;48(4):607-613.
 Mapping the dsRNA World. Reich DP, Bass BL. Cold Spring Harb Perspect Biol. 2019 Mar 1;11(3):a035352.
 To protect and modify double-stranded RNA – the critical roles of ADARs in development, immunity and oncogenesis. Erdmann EA, Mahapatra A, Mukherjee P, Yang B, Hundley HA. Crit Rev Biochem Mol Biol. 2021 Feb;56(1):54-87.
 Loss of ADAR1 in tumours overcomes resistance to immune checkpoint blockade. Ishizuka JJ, Manguso RT, Cheruiyot CK, Bi K, Panda A, et al. Nature. 2019 Jan;565(7737):43-48.
Bass Lab (University of Utah, Salt Lake City)
Elde Lab (University of Utah)
Jackman Lab (Ohio State University, Columbus)
Stetson Lab (University of Washington, Seattle)
Bass/Elde/Jackman/Stetson Project Information (NIH RePORTER)
NIH Director’s Transformative Research Award Program (Common Fund)
NIH Support: Common Fund; National Cancer Institute
Posted on by Dr. Francis Collins
COVID-19 is primarily considered a respiratory illness that affects the lungs, upper airways, and nasal cavity. But COVID-19 can also affect other parts of the body, including the digestive system, blood vessels, and kidneys. Now, a new study has added something else: the mouth.
The study, published in the journal Nature Medicine, shows that SARS-CoV-2, which is the coronavirus that causes COVID-19, can actively infect cells that line the mouth and salivary glands. The new findings may help explain why COVID-19 can be detected by saliva tests, and why about half of COVID-19 cases include oral symptoms, such as loss of taste, dry mouth, and oral ulcers. These results also suggest that the mouth and its saliva may play an important—and underappreciated—role in spreading SARS-CoV-2 throughout the body and, perhaps, transmitting it from person to person.
The latest work comes from Blake Warner of NIH’s National Institute of Dental and Craniofacial Research; Kevin Byrd, Adams School of Dentistry at the University of North Carolina, Chapel Hill; and their international colleagues. The researchers were curious about whether the mouth played a role in transmitting SARS-CoV-2. They were already aware that transmission is more likely when people speak, cough, and even sing. They also knew from diagnostic testing that the saliva of people with COVID-19 can contain high levels of SARS-CoV-2. But did that virus in the mouth and saliva come from elsewhere? Or, was SARS-CoV-2 infecting and replicating in cells within the mouth as well?
To find out, the research team surveyed oral tissue from healthy people in search of cells that express the ACE2 receptor protein and the TMPRSS2 enzyme protein, both of which SARS-CoV-2 depends upon to enter and infect human cells. They found the proteins may be expressed individually in the primary cells of all types of salivary glands and in tissues lining the oral cavity. Indeed, a small portion of salivary gland and gingival (gum) cells around our teeth, simultaneously expressed the genes encoding ACE2 and TMPRSS2.
Next, the team detected signs of SARS-CoV-2 in just over half of the salivary gland tissue samples that it examined from people with COVID-19. The samples included salivary gland tissue from one person who had died from COVID-19 and another with acute illness.
The researchers also found evidence that the coronavirus was actively replicating to make more copies of itself. In people with mild or asymptomatic COVID-19, oral cells that shed into the saliva bathing the mouth were found to contain RNA for SARS-CoV-2, as well its proteins that it uses to enter human cells.
The researchers then collected saliva from another group of 35 volunteers, including 27 with mild COVID-19 symptoms and another eight who were asymptomatic. Of the 27 people with symptoms, those with virus in their saliva were more likely to report loss of taste and smell, suggesting that oral infection might contribute to those symptoms of COVID-19, though the primary cause may be infection of the olfactory tissues in the nose.
Another important question is whether SARS-CoV-2, while suspended in saliva, can infect other healthy cells. To get the answer, the researchers exposed saliva from eight people with asymptomatic COVID-19 to healthy cells grown in a lab dish. Saliva from two of the infected volunteers led to infection of the healthy cells. These findings raise the unfortunate possibility that even people with asymptomatic COVID-19 might unknowingly transmit SARS-CoV-2 to other people through their saliva.
Overall, the findings suggest that the mouth plays a greater role in COVID-19 infection and transmission than previously thought. The researchers suggest that virus-laden saliva, when swallowed or inhaled, may spread virus into the throat, lungs, or digestive system. Knowing this raises the hope that a better understanding of how SARS-CoV-2 infects the mouth could help in pointing to new ways to prevent the spread of this devastating virus.
 SARS-CoV-2 infection of the oral cavity and saliva. Huang N, Pérez P, Kato T, Mikami Y, Chiorini JA, Kleiner DE, Pittaluga S, Hewitt SM, Burbelo PD, Chertow D; NIH COVID-19 Autopsy Consortium; HCA Oral and Craniofacial Biological Network, Frank K, Lee J, Boucher RC, Teichmann SA, Warner BM, Byrd KM, et. al Nat Med. 2021 Mar 25.
COVID-19 Research (NIH)
Saliva & Salivary Gland Disorders (National Institute of Dental and Craniofacial Research/NIH)
Blake Warner (National Institute of Dental and Craniofacial Research/NIH)
Kevin Byrd (Adams School of Dentistry at University of North Carolina, Chapel Hill)
NIH Support: National Institute of Dental and Craniofacial Research; National Institute of Diabetes and Digestive and Kidney Diseases; National Center for Advancing Translational Sciences
Posted on by Dr. Francis Collins
It’s become increasingly clear that even healthy people with mild cases of COVID-19 can battle a constellation of symptoms that worsen over time—or which sometimes disappear only to come right back. These symptoms are part of what’s called “Long COVID Syndrome.”
Now, a new study of relatively young, healthy adult healthcare workers in Sweden adds needed information on the frequency of this Long COVID Syndrome. Published in the journal JAMA, the study found that just over 1 in 10 healthcare workers who had what at first seemed to be a relatively mild bout of COVID-19 were still coping with at least one moderate to severe symptom eight months later . Those symptoms—most commonly including loss of smell and taste, fatigue, and breathing problems—also negatively affected the work and/or personal lives of these individuals.
These latest findings come from the COVID-19 Biomarker and Immunity (COMMUNITY) study, led by Charlotte Thålin, Danderyd Hospital and Karolinska Institutet, Stockholm. The study, launched a year ago, enlisted 2,149 hospital employees to learn more about immunity to SARS-CoV-2, the coronavirus that causes COVID-19.
After collecting blood samples from participants, the researchers found that about 20 percent already had antibodies to SARS-CoV-2, evidence of a past infection. Thålin and team continued collecting blood samples every four months from all participants, who also completed questionnaires about their wellbeing.
Intrigued by recent reports in the medical literature that many people hospitalized with COVID-19 can have persistent symptoms for months after their release, the researchers decided to take a closer look in their COMMUNITY cohort. They did so last January during their third round of follow up.
This group included 323 mostly female healthcare workers, median age of 43. The researchers compared symptoms in this group following mild COVID-19 to the 1,072 mostly female healthcare workers in the study (median age 47 years) who hadn’t had COVID-19. They wanted to find out if those with mild COVID-19 coped with more and longer-lasting symptoms of feeling unwell than would be expected in an otherwise relatively healthy group of people. These symptoms included familiar things such as fatigue, muscle pain, trouble sleeping, and problems breathing.
Their findings show that 26 percent of those who had mild COVID-19 reported at least one moderate to severe symptom that lasted more than two months. That’s compared to 9 percent of participants without COVID-19. What’s more, 11 percent of the individuals with mild COVID-19 had at least one debilitating symptom that lasted for at least eight months. In the group without COVID-19, any symptoms of feeling unwell resolved relatively quickly.
The most common symptoms in the COVID-19 group were loss of taste or smell, fatigue, and breathing problems. In this group, there was no apparent increase in other symptoms that have been associated with COVID-19, including “brain fog,” problems with memory or attention, heart palpitations, or muscle and joint pain.
The researchers have noted that the Swedish healthcare workers represent a relatively young and healthy group of working individuals. Yet, many of them continued to suffer from lasting symptoms related to mild COVID-19. It’s a reminder that COVID-19 can and, in fact, is having a devastating impact on the lives and livelihoods of adults who are at low risk for developing severe and life-threatening COVID-19. If we needed one more argument for getting young people vaccinated, this is it.
At NIH, efforts have been underway for some time to identify the causes of Long COVID. In fact, a virtual workshop was held last winter with more than 1,200 participants to discuss what’s known and to fill in key gaps in our knowledge of Long COVID syndrome, which is clinically known as post-acute sequelae of COVID-19 (PASC). Recently, a workshop summary was published . As workshops and studies like this one from Sweden help to define the problem, the hope is to learn one day how to treat or prevent this terrible condition. The NIH is now investing more than $1 billion in seeking those answers.
 Symptoms and functional impairment assessed 8 Months after mild COVID-19 among health care workers. Havervall S, Rosell A, Phillipson M, Mangsbo SM, Nilsson P, Hober S, Thålin C. JAMA. 2021 Apr 7.
 Toward understanding COVID-19 recovery: National Institutes of Health workshop on postacute COVID-19. Lerner A, et al. Ann Intern Med, 2021 March 30.
COVID-19 Research (NIH)
Charlotte Thålin (Karolinska Institutet, Stockholm, Sweden)
Previous Page Next Page