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Searching for Ways to Prevent Life-Threatening Blood Clots in COVID-19

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At Home with Gary Gibbons

Six months into the coronavirus disease 2019 (COVID-19) pandemic, researchers still have much to learn about the many ways in which COVID-19 can wreak devastation on the human body. Among the many mysteries is exactly how SARS-CoV-2, which is the novel coronavirus that causes COVID-19, triggers the formation of blood clots that can lead to strokes and other life-threatening complications, even in younger people.

Recently, I had a chance to talk with Dr. Gary Gibbons, Director of NIH’s Heart, Lung, and Blood Institute (NHLBI) about what research is being done to tackle this baffling complication of COVID-19. Our conversation took place via videoconference, with him connecting from his home in Washington, D.C., and me linking in from my home just up the road in Maryland. Here’s a condensed transcript of our chat:

Collins: I’m going to start by asking about the SARS-CoV-2-induced blood clotting not only in the lungs, but in other parts of the body. What do we know about the virus that would explain this?

Gibbons: It seems like every few weeks another page gets turned on COVID-19, and we learn even more about how this virus affects the body. Blood clots are one of the startling and, unfortunately, devastating complications that emerged as patients were cared for, particularly in New York City. It became apparent that certain individuals had difficulty getting enough oxygen into their system. The difficulty couldn’t be explained entirely by the extent of the pneumonia affecting the lungs’ ability to exchange oxygen.

It turned out that, in addition to the pneumonia, blood clots in the lungs were compromising oxygenation. But some patients also had clotting, or thrombotic, complications in their veins and arteries in other parts of the body. Quite puzzling. There were episodes of relatively young individuals in their 30s and 40s presenting with strokes related to blood clots affecting the arterial circulation to the brain.

We’re still trying to understand what promotes the clotting. One clue involves the endothelial cells that form the inner lining of our blood vessels. These cells have on their surface a protein called the angiotensin-converting enzyme 2 (ACE2) receptor, and this clue is important for two reasons. One, the virus attaches to the ACE2 receptor, using it as an entry point to infect cells. Two, endothelial-lined blood vessels extend to every organ in the body. Taken together, it seems that some COVID-19 complications relate to the virus attaching to endothelial cells, not only in the lungs, but in the heart and multiple organs.

Collins: So, starting in the respiratory tree, the virus somehow breaks through into a blood vessel and then gets spread around the body. There have been strange reports of people with COVID-19 who may not get really sick, but their toes look frostbitten. Is “COVID toes,” as some people call it, also part of this same syndrome?

Gibbons: We’re still in the early days of learning about this virus. But I think this offers a further clue that the virus not only affects large vessels but small vessels. In fact, clots have been reported at the capillary level, and that’s fairly unusual. It’s suggestive that an interaction is taking place between the platelets and the endothelial surface.

Normally, there’s a tightly regulated balance in the bloodstream between pro-coagulant and anticoagulant proteins to prevent clotting and keep the blood flowing. But when you cut your finger, for example, you get activation for blood clots in the form of a protein mesh. It looks like a fishing net that can help seal the injury. In addition, platelets in the blood stream help to plug the holes in that fishing net and create a real seal of a blood vessel.

Well, imagine it happening in those small vessels, which usually have a non-stick endothelial surface, almost like Teflon, that prevents clotting. Then the virus comes along and tips the balance toward promoting clot formation. This disturbs the Teflon-like property of the endothelial lining and makes it sticky. It’s incredible the tricks this virus has learned by binding onto one of these molecules in the endothelial lining.

Collins: Who are the COVID-19 patients most at risk for this clotting problem?

Gibbons: Unfortunately, it appears right now that older adults are among the most vulnerable. They have a lot of the risks for the formation of these blood clots. What’s notable is these thrombotic complications are also happening to relatively young adults or middle-aged individuals who don’t have a lot of other chronic conditions, or comorbidities, to put them at higher risk for severe disease. Again, it’s suggestive that this virus is doing something that is particular to the coagulation system.

Collins: We’d love to have a way of identifying in advance the people who are most likely to get into trouble with blood clotting. They might be the ones you’d want to start on an intervention, even before you have evidence that things are getting out of control. Do you have any kind of biomarker to tell you which patients might benefit from early intervention?

Gibbons: Biomarkers are being actively studied. What we do know from some earlier observations is that you can assess the balance of clotting and anticlotting factors in the blood by measuring a biomarker called D-dimer. It’s basically a protein fragment, a degradation product, from a prior clot. It tells you a bit about the system’s activity in forming and dissolving clots.
If there’s a lot of D-dimer activity, it suggests a coagulation cascade is jazzed up. In those patients, it’s probably a clue that this is a big trigger in terms of coagulation and thrombosis. So, D-dimer levels could maybe tell us which patients need really aggressive full anticoagulation.

Collins: Have people tried empirically using blood thinners for people who seem to be getting into trouble with this clotting problem?

Gibbons: There’s a paper out of the Mount Sinai in New York City that looked at thousands of patients being treated for COVID-19 [1]. Based on clinical practice and judgments, one of the striking findings is that those who were fully anticoagulated had better survival than those who were not. Now, this was not a randomized, controlled clinical trial, where some were given full anticoagulation and others were not. It was just an observational study that showed an association. But this study indicated indirectly that by giving the blood thinners, changing that thrombotic risk, maybe it’s possible to reduce morbidity and mortality. That’s why we need to do a randomized, controlled clinical trial to see if it can be used to reduce these case fatality rates.

Collins: You and your colleagues got together and came up with a design for such a clinical trial. Tell us about that.

Gibbons: My institute studies the heart, lung, and blood. The virus attacks all three. So, our community has a compelling need to lean in and study COVID-19. Recently, NIH helped to launch a public-private partnership called Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV). As the name spells out, this initiative provides is a clinical platform to generate life-saving treatments as we wait for the development of a vaccine.

Through ACTIV, a protocol is now in the final stages of review for a clinical trial that will involve a network of hospitals and explore the question: is it sufficient to try a low-dose thrombo-prophylactic, or clot preventative, approach versus full anticoagulation? Some think patients ought to have full anticoagulation, but that’s not without risk. So, we want to put that question to the test. As part of that, we’ll also learn more about biomarkers and what could be predictive of individuals getting the greatest benefit.

If we find that fully anticoagulating patients prevents clots, then that’s great. But it begs the question: what happens when patients go home? Is it sufficient to just turn off the drip and let them go their merry way? Should they have a low dose thrombo-prophylactic regimen for a period of time? If so, how long? Or should they be fully anticoagulated with oral anticoagulation for a certain period of time? All these and other questions still remain.

Collins: This can make a huge difference. If you’re admitted to the hospital with COVID-19, that means you’re pretty sick and, based on the numbers that I’ve seen, your chance of dying is about 12 percent if nothing else happens. If we can find something like an anticoagulant that would reduce that risk substantially, we can have a huge impact on reducing deaths from COVID-19. How soon can we get this trial going, Gary?

Gibbons: We have a sense of urgency that clearly this pandemic is taking too many lives and time is of the essence. So, we’ve indeed had a very streamlined process. We’re leveraging the fact that we have clinical trial networks, where regardless of what they were planning to do, it’s all hands on deck. As a result, we’re able to move faster to align with that sense of urgency. We hope that we can be off to a quick launch within the next two to three weeks with the anticoagulation trials.

Collins: This is good because people are waiting on the vaccines, but realistically we won’t know whether the vaccines are working for several more months, and having them available for lots of people will be at the very end of this year or early 2021 at best. Meanwhile, people still are going to be getting sick with COVID-19. We want to be able to have as many therapeutic options as possible to offer to them. And this seems like a pretty exciting one to try and move forward as quickly as possible. You and your colleagues deserve a lot of credit for bringing this to everybody’s attention.

But before we sign off, I have to raise another issue of deep significance. Gary, I think both of us are struggling not only with the impact of COVID-19 on the world, but the profound sorrow, grief, frustration, and anger that surrounds the death of George Floyd. This brings into acute focus the far too numerous other circumstances where African Americans have been mistreated and subjected to tragic outcomes.

This troubling time also shines a light on the health disparities that affect our nation in so many ways. We can see what COVID-19 has done to certain underrepresented groups who have borne an undue share of the burden, and have suffered injustices at the hands of society. It’s been tough for many of us to admit that our country is far from treating everyone equally, but it’s a learning opportunity and a call to redouble our efforts to find solutions.

Gary, you’ve been a wonderful leader in that conversation for a long time. I want to thank you both for what you’re doing scientifically and for your willingness to speak the truth and stand up for what’s right and fair. It’s been great talking to you about all these issues.

Gibbons: Thank you. We appreciate this opportunity to fulfill NIH’s mission of turning scientific discovery into better health for all. If there’s any moment that our nation needs us, this is it.


[1] Association of Treatment Dose Anticoagulation With In-Hospital Survival Among Hospitalized Patients With COVID-19. Paranjpe I, Fuster V, Lala A, Russak A, Glicksberg BS, Levin MA, Charney AW, Narula J, Fayad ZA, Bagiella E, Zhao S, Nadkarni GN. J Am Coll Cardiol. 2020 May 5;S0735-1097(20)35218-9.


Coronavirus (COVID-19) (NIH)

Rising to the Challenge of COVID-19: The NHLBI Community Response,” Director’s Messages, National Heart, Lung, and Blood Institute/NIH, April 29, 2020.

Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) (NIH)

Looking for Answers to Epilepsy in a Blood Test

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Gemma Carvill and lab members
Gemma Carvill (second from right) with members of her lab. Courtesy of Gemma Carvill

Millions of people take medications each day for epilepsy, a diverse group of disorders characterized by seizures. But, for about a third of people with epilepsy, current drug treatments don’t work very well. What’s more, the medications are designed to treat symptoms of these disorders, basically by suppressing seizure activity. The medications don’t really change the underlying causes, which are wired deep within the brain.

Gemma Carvill, a researcher at Northwestern University Feinberg School of Medicine, Chicago, wants to help change that in the years ahead. She’s dedicated her research career to discovering the genetic causes of epilepsy in hopes of one day designing treatments that can control or even cure some forms of the disorder [1].

It certainly won’t be easy. A recent paper put the number of known genes associated with epilepsy at close to 1,000 [2]. However, because some disease-causing genetic variants may arise during development, and therefore occur only within the brain, it’s possible that additional genetic causes of epilepsy are still waiting to be discovered within the billions of cells and their trillions of interconnections.

To find these new leads, Carvill won’t have to rely only on biopsies of brain tissue. She’s received a 2018 NIH Director’s New Innovator Award in search of answers hidden within “liquid biopsies”—tiny fragments of DNA that research in other forms of brain injury and neurological disease [3] suggests may spill into the bloodstream and cerebrospinal fluid (CSF) from dying neurons or other brain cells following a seizure.

Carvill and team will start with mouse models of epilepsy to test whether it’s possible to detect DNA fragments from the brain in bodily fluids after a seizure. They’ll also attempt to show DNA fragments carry telltale signatures indicating from which cells and tissues in the brain those molecules originate. The hope is these initial studies will also tell them the best time after a seizure to collect blood samples.

In people, Carvill’s team will collect the DNA fragments and begin searching for genetic alterations to explain the seizures, capitalizing on Carvill’s considerable expertise in the use of next generation DNA sequencing technology for ferreting out disease-causing variants. Importantly, if this innovative work in epilepsy pans out, it also can be applied to any other neurological condition in which DNA spills from dying brain cells, including Alzheimer’s disease and Parkinson’s disease.


[1] Unravelling the genetic architecture of autosomal recessive epilepsy in the genomic era. Calhoun JD, Carvill GL. J Neurogenet. 2018 Sep 24:1-18.

[2] Epilepsy-associated genes. Wang J, Lin ZJ, Liu L, Xu HQ, Shi YW, Yi YH, He N, Liao WP. Seizure. 2017 Jan;44:11-20.

[3] Identification of tissue-specific cell death using methylation patterns of circulating DNA. Lehmann-Werman R, Neiman D, Zemmour H, Moss J, Magenheim J, Vaknin-Dembinsky A, Rubertsson S, Nellgård B, Blennow K, Zetterberg H, Spalding K, Haller MJ, Wasserfall CH, Schatz DA, Greenbaum CJ, Dorrell C, Grompe M, Zick A, Hubert A, Maoz M, Fendrich V, Bartsch DK, Golan T, Ben Sasson SA, Zamir G, Razin A, Cedar H, Shapiro AM, Glaser B, Shemer R, Dor Y. Proc Natl Acad Sci U S A. 2016 Mar 29;113(13):E1826-34.


Epilepsy Information Page (National Institute of Neurological Disorders and Stroke/NIH)

Gemma Carvill Lab (Northwestern University Feinberg School of Medicine, Chicago)

Carvill Project Information (NIH RePORTER)

NIH Director’s New Innovator Award (Common Fund)

NIH Support: Common Fund; National Institute of Neurological Disorders and Stroke

Moving Toward Answers in ME/CFS

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Woman in bed

Thinkstock/Katarzyna Bialasiewicz

Updated September 27, 2017: The National Institutes of Health (NIH) will award four grants to establish a coordinated scientific research effort on myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The total cost of the projects for fiscal year 2017 will be over $7 million, with support from multiple NIH Institutes and Centers that are part of the Trans-NIH ME/CFS Working Group.

The grants will support the creation of a consortium made up of three Collaborative Research Centers (CRC) and a Data Management Coordinating Center (DMCC). The CRCs will each conduct independent research but will also collaborate on several projects, forming a network to help advance knowledge on ME/CFS. The data will be managed by the DMCC and will be shared among researchers within the CRCs and more broadly with the research community.

Imagine going to work or school every day, working out at the gym, spending time with family and friends—basically, living your life in a full and vigorous way. Then one day, you wake up, feeling sick. A bad cold maybe, or perhaps the flu. A few days pass, and you think it should be over—but it’s not, you still feel achy and exhausted. Now imagine that you never get better— plagued by unrelenting fatigue not relieved by sleep. Any exertion just makes you worse. You are forced to leave your job or school and are unable to participate in any of your favorite activities; some days you can’t even get out of bed. The worst part is that your doctors don’t know what is wrong and nothing seems to help.

Unfortunately, this is not fiction, but reality for at least a million Americans—who suffer from a condition that carries the unwieldy name of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), a perplexing disease that biomedical research desperately needs to unravel [1]. Very little is currently known about what causes ME/CFS or its biological basis [2]. Among the many possibilities that need to be explored are problems in cellular metabolism and changes in the immune system.

What Is Obesity? Metabolic Signatures Offer New Comprehensive View

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Silhouettes over an NMR

Credit: Adapted from Elliott, P et al., Sci Transl Med. 2015 Apr 29;7(285)

As obesity has risen in the United States and all around the world, so too have many other obesity-related health conditions: diabetes, heart disease, stroke, cancer, and maybe even Alzheimer’s disease. But how exactly do those extra pounds lead to such widespread trouble, and how might we go about developing better ways to prevent or alleviate this very serious health threat?

In a new study in Science Translational Medicine [1], researchers performed sophisticated analyses of the molecules excreted in human urine to produce one of the most comprehensive pictures yet of the metabolic signature that appears to correlate with obesity. This work provides a fascinating preview of things to come as researchers from metabolomics, microbiomics, and a wide variety of other fields strive to develop more precise approaches to managing and preventing disease.

Metabolomics: Taking Aim at Diabetic Kidney Failure

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Patients with red tubes attached to their arms

Caption: Dialysis is often used to treat kidney failure related to diabetes.

My own research laboratory has worked on the genetics of diabetes for two decades. One of my colleagues from those early days, Andrzej Krolewski, a physician-scientist at the Joslin Diabetes Center in Boston, wondered why about one-third of people with type 2 diabetes eventually develop kidney damage that progresses to end-stage renal disease (ESRD), but others don’t. A stealthy condition that can take years for symptoms to appear, ESRD occurs when the kidneys fail, allowing toxic wastes to build up. The only treatments available are dialysis or kidney transplants.