Snapshots of Life
Posted on by Dr. Francis Collins
Spiders spin webs to catch insects for dinner. It turns out certain human immune cells, called neutrophils, do something similar to trap bacteria in people who develop sepsis, an uncontrolled, systemic infection that poses a major challenge in hospitals.
When activated to catch sepsis-causing bacteria or other pathogens, neutrophils rupture and spew sticky, spider-like webs made of DNA and antibacterial proteins. Here in red you see one of these so-called neutrophil extracellular traps (NETs) that’s ensnared Staphylococcus aureus (green), a type of bacteria known for causing a range of illnesses from skin infections to pneumonia.
Yet this image, which comes from Kandace Gollomp and Mortimer Poncz at The Children’s Hospital of Philadelphia, is much more than a fascinating picture. It demonstrates a potentially promising new way to treat sepsis.
The researchers’ strategy involves adding a protein called platelet factor 4 (PF4), which is released by clot-forming blood platelets, to the NETs. PF4 readily binds to NETs and enhances their capture of bacteria. A modified antibody (white), which is a little hard to see, coats the PF4-bound NET above. This antibody makes the NETs even better at catching and holding onto bacteria. Other immune cells then come in to engulf and clean up the mess.
Until recently, most discussions about NETs assumed they were causing trouble, and therefore revolved around how to prevent or get rid of them while treating sepsis. But such strategies faced a major obstacle. By the time most people are diagnosed with sepsis, large swaths of these NETs have already been spun. In fact, destroying them might do more harm than good by releasing entrapped bacteria and other toxins into the bloodstream.
In a recent study published in the journal Blood, Gollomp’s team proposed flipping the script . Rather than prevent or destroy NETs, why not modify them to work even better to fight sepsis? Their idea: Make NETs even stickier to catch more bacteria. This would lower the number of bacteria and help people recover from sepsis.
Gollomp recalled something lab member Anna Kowalska had noted earlier in unrelated mouse studies. She’d observed that high levels of PF4 were protective in mice with sepsis. Gollomp and her colleagues wondered if the PF4 might also be used to reinforce NETs. Sure enough, Gollomp’s studies showed that PF4 will bind to NETs, causing them to condense and resist break down.
Subsequent studies in mice and with human NETs cast in a synthetic blood vessel suggest that this approach might work. Treatment with PF4 greatly increased the number of bacteria captured by NETs. It also kept NETs intact and holding tightly onto their toxic contents. As a result, mice with sepsis fared better.
Of course, mice are not humans. More study is needed to see if the same strategy can help people with sepsis. For example, it will be important to determine if modified NETs are difficult for the human body to clear. Also, Gollomp thinks this approach might be explored for treating other types of bacterial infections.
Still, the group’s initial findings come as encouraging news for hospital staff and administrators. If all goes well, a future treatment based on this intriguing strategy may one day help to reduce the 270,000 sepsis-related deaths in the U.S. and its estimated more than $24 billion annual price tag for our nation’s hospitals [2, 3].
 Fc-modified HIT-like monoclonal antibody as a novel treatment for sepsis. Gollomp K, Sarkar A, Harikumar S, Seeholzer SH, Arepally GM, Hudock K, Rauova L, Kowalska MA, Poncz M. Blood. 2020 Mar 5;135(10):743-754.
 Sepsis, Data & Reports, Centers for Disease Control and Prevention, Feb. 14, 2020.
 National inpatient hospital costs: The most expensive conditions by payer, 2013: Statistical Brief #204. Torio CM, Moore BJ. Healthcare Cost and Utilization Project (HCUP) Statistical Briefs. Agency for Healthcare Research and Quality (US); 2016 May.
Sepsis (National Institute of General Medical Sciences/NIH)
Kandace Gollomp (The Children’s Hospital of Philadelphia, PA)
Mortimer Poncz (The Children’s Hospital of Philadelphia, PA)
NIH Support: National Heart, Lung, and Blood Institute
Posted on by Dr. Francis Collins
The coronavirus disease 2019 (COVID-19) pandemic has truly been an all-hands-on-deck moment for the nation. Among the responders are many with NIH affiliations, who are lending their expertise to deploy new and emerging technologies to address myriad research challenges. That’s certainly the case for the dedicated team from the National Institute of Allergy and Infectious Diseases (NIAID) at the NIH 3D Print Exchange (3DPX), Rockville, MD.
A remarkable example of the team’s work is this 3D-printed physical model of SARS-CoV-2, the novel coronavirus that causes COVID-19. This model shows the viral surface (blue) and the spike proteins studded proportionally to the right size and shape. These proteins are essential for SARS-CoV-2 to attach to human cells and infect them. Here, the spike proteins are represented in their open, active form (orange) that’s capable of attaching to a human cell, as well as in their closed, inactive form (red).
The model is about 5 inches in diameter. It takes more than 5 hours to print using an “ink” of thin layers of a gypsum plaster-based powder fused with a colored binder solution. When completed, the plaster model is coated in epoxy for strength and a glossy, ceramic-like finish. For these models, NIAID uses commercial-grade, full-color 3D printers. However, the same 3D files can be used in any type of 3D printer, including “desktop” models available on the consumer market.
Darrell Hurt and Meghan McCarthy lead the 3DPX team. Kristen Browne, Phil Cruz, and Victor Starr Kramer, the team members who helped to produce this remarkable model, created it as part of a collaboration with the imaging team at NIAID’s Rocky Mountain Laboratories (RML), Hamilton, MT.
The RML’s Electron Microscopy Unit captured the microscopic 3D images of the virus, which was cultured from one of the first COVID-19 patients in the country. The unit handed off these and other data to its in-house visual specialist to convert into a preliminary 3D model. The model was then forwarded to the 3DPX team in Maryland to colorize and optimize in preparation for 3D printing.
This model is especially unique because it’s based exclusively on SARS-CoV-2 data. For example, the model is assembled from data showing that the virus is frequently oval, not perfectly round. The spike proteins also aren’t evenly spaced, but pop up more randomly from the surface. Another nice feature of 3D printing is the models can be constantly updated to incorporate the latest structural discoveries.
That’s why 3D models are such an excellent teaching tools to share among scientists and the public. Folks can hold the plaster virus and closely examine its structure. In fact, the team recently printed out a model and delivered it to me for exactly this educational purpose.
In addition to this complete model, the researchers also are populating the online 3D print exchange with atomic-level structures of the various SARS-CoV-2 proteins that have been deposited by researchers around the world into protein and electron microscopy databanks. The number of these structures and plans currently stands at well over 100—and counting.
As impressive as this modeling work is, 3DPX has found yet another essential way to aid in the COVID-19 fight. In March, the Food and Drug Administration (FDA) announced a public-private partnership with the NIH 3D Print Exchange, Department of Veterans Affairs (VA) Innovation Ecosystem, and the non-profit America Makes, Youngstown, OH . The partnership will develop a curated collection of designs for 3D-printable personal protective equipment (PPE), as well as other necessary medical devices that are in short supply due to the COVID-19 pandemic.
You can explore the partnership’s growing collection of COVID-19-related medical supplies online. And, if you happen to have a 3D printer handy, you could even try making them for yourself.
 FDA Efforts to Connect Manufacturers and Health Care Entities: The FDA, Department of Veterans Affairs, National Institutes of Health, and America Makes Form a COVID-19 response Public-Private Partnership (Food and Drug Administration)
Coronavirus (COVID-19) (NIH)
NIH 3D Print Exchange (National Institute of Allergy and Infectious Diseases/NIH, Rockville, MD)
Rocky Mountain Laboratories (NIAID/NIH, Hamilton, MT)
Department of Veterans Affairs (VA) Innovation Ecosystem (Washington, D.C.)
America Makes (Youngstown, OH)
NIH Support: National Institute of Allergy and Infectious Diseases