Nanodecoys made from human lung spheroid cells (LSCs) can bind to and neutralize SARS-CoV-2, promoting viral clearance and reducing lung injury in a macaque model of COVID-19. By mimicking the receptor that the virus binds to rather than targeting the virus itself, nanodecoy therapy could remain effective against emerging variants of the virus.SARS-CoV-2 enters a cell when its spike protein binds to the angiotensin-converting enzyme 2 (ACE2) receptor on the cell’s surface. LSCs—a natural mixture of lung epithelial stem cells and mesenchymal cells—also express ACE2, making them a perfect vehicle for tricking the virus.
They confirmed that the spike protein did bind to the ACE2 receptors on the decoys in vitro, then used a fabricated SARS-Co-V-2 mimic virus for in vivo testing in a mouse model. The decoys were delivered via inhalation therapy. In mice, the nanodecoys remained in the lungs for 72 hours after one dose and accelerated clearance of the mimic virus.
Finally, a contract research organization conducted a pilot study in a macaque model and found that inhalation therapy with the nanodecoys accelerated viral clearance, and reduced inflammation and fibrosis in the lungs. Although no toxicity was noted in either the mouse or macaque study, further study will be necessary to translate this therapy for human testing and determine exactly how the nanodecoys are cleared by the body.
These nanodecoys are essentially cell ‘ghosts,’ and one LSC can generate around 11,000 of them. Deploying millions of these decoys exponentially increases the surface area of fake binding sites for trapping the virus, and their small size basically turns them into little bite-sized snacks for macrophages, so they are cleared very efficiently.
The researchers point out three other benefits of the LSC nanodecoys. First, they can be delivered non-invasively to the lungs via inhalation therapy. Second, since the nanodecoys are acellular—there’s nothing living inside—they can be easily preserved and remain stable longer, enabling off-the-shelf use. Finally, LSCs are already in use in other clinical trials, so there is an increased likelihood of being able to use them in the near future.
Zhenhua Li et al, Cell-mimicking nanodecoys neutralize SARS-CoV-2 and mitigate lung injury in a non-human primate model of COVID-19, Nature Nanotechnology (2021). DOI: 10.1038/s41565-021-00923-2