Potential COVID-19 treatment pairs nanoparticles with immune system to search and destroy viruses
Researchers at the University of Chicago have designed a completely novel potential treatment for COVID-19: nanoparticles that capture SARS-CoV-2 viruses within the body and then use the body’s own immune system to destroy them. These “nanotraps” attract the virus by mimicking the target cells the virus infects. When the virus binds to the nanotraps, the traps then sequester the virus from other cells and target it for destruction by the immune system. The results were published April 19 in the journal Matter. To design the nanotrap, the research team—led by postdoctoral scholar Min Chen and graduate student Jill Rosenberg—looked into the mechanism SARS-CoV-2 uses to bind to cells: a spike-like protein on its surface that binds to a human cell’s ACE2 receptor protein. To create a trap that would bind to the virus in the same way, they designed nanoparticles with a high density of ACE2 proteins on their surface. Similarly, they designed other nanoparticles with neutralizing antibodies on their surfaces. Made of FDA-approved polymers and phospholipids, the nanoparticles are about 500 nanometers in diameter—much smaller than a cell. That means the nanotraps can reach more areas inside the body and more effectively trap the virus. Then, to check to make sure the tiny particles looked the way they expected, they partnered with the lab of Assoc. Prof. Bozhi Tian to use electron microscopes to get a good look. “From our imaging, we saw a solid core and a lipid bilayer shell. That’s the essential part because it mimics the cell,” said Tian, who is appointed in the Department of Chemistry.
The researchers tested the safety of the system in a mouse model and found no toxicity. They then tested the nanotraps against a pseudovirus—a less potent model of a virus that doesn’t replicate—in human lung cells in tissue culture plates and found that they completely blocked entry into the cells. Once the pseudovirus bound itself to the nanoparticle—which in tests took about 10 minutes after injection—the nanoparticles used a molecule that calls the body’s macrophages to engulf and degrade the nanotrap. Macrophages will generally eat nanoparticles within the body, but the nanotrap molecule speeds up the process. The nanoparticles were cleared and degraded within 48 hours. The nanotraps can be stored in a standard freezer and could ultimately be given via an intranasal spray, which would place them directly in the respiratory system and make them most effective.
Source: University of Chicago news release